Elementary Particles Presented

[marlon]

Hi everyone...

I have answered already a lot of questions here on the topic of the different elementary particles in the Standard Model. For this reason I will give the interested reader this site that describes this subject very clearly...

http://pdg.web.cern.ch/pdg/particleadventure/frameless/startstandard.html

If you have more questions, please don't hesitate to post them here...

regards
marlon :biggrin: :cool:

[humanino]

The Standard Model relies on several assumptions, among which the existence of a certain fields, whose quanta are point-like particles, divided first in two categories : matter and force particles.

Matter particles

Those fundamental particles are fermionic, which implies one can fill a box with them until none can be added (as long as the box is strong enough to resist electric repulsion for instance). Fermi-Dirac statistics is a deep phenomenon, linked to the intrinsic angular momentum called spin : fundamental fermions are spin 1/2 (spinor) particles, and it implies that after a rotation of 2\pi, their wavefunction changes sign !. This is not a real problem, since only the (hermitean) square of the wavefunction is observable, that is the probability density. Notice also that after 4\pi the double sign reverses cancel, and there are deep reasons why 4\pi rotations are always equivalent to no rotation. Let us first stare at a list of them :

First familySecond familyThird family

electron e^-muon \mu^-tau \tau^-

electronic neutrino \nu_{e} muonic neutrino \nu_{\mu} tauonic neutrino \nu_{\tau}


up quark ucharm quark ctop quark t
down quark dstrange quark sbottom (beauty) quark b


Botanistic classification : 1 and 2 are leptons, while 3 and 4 are hadrons. Leptons do not feel the strong force (on which more latter). Etymology : "hadron" comes from a greek word sounding like "hadros" and meaning "strong, robust, bulky, thick, or stout", and "lepton" from "leptos" : "fine, thin, slender, small". To this list you could add anti-particles, or consider they are ordinary particles travelling backwards in time. Anti-particles have opposite charges except mass and spin, are denoted by an upper bar on the particle symbol, and sometimes have a special name, such as the positron \bar{e}^+. Each of those might have a supersymetric bosonic partner (supersymetry relates bosons and fermions) but this is not part of the standard model. Although supersymetry has shown relevance in nuclei, it has not been observed for fundamental particles. Some basic facts :

Carry minus one unit of electrical charge : -e.
Zero electric charge, and at most a very small mass (zero in the standard model)
+2/3 e, and color charge (red, blue or green) which is "hidden" : free particles are "white", or more accurately "invariant under color rotations".
-2/3 e. Also colored. It is difficult to define mass for 3 and 4 guys because they are never free, especially difficult for the lightest, first family members.


The quarks are "contained in a white bag", either they pair in mesons (quark/antiquark bound state) or in baryons (three quarks bound states). Recent proposal of "pentaquarks" seem nowadays unlikely : only intermediate energy have published low statistics evidences, high energy experiments lead to negative results. Confirmation or rejection of this hypothesis will be available soon, when the analyzing process of data from dedicated experiments will be over.

Force particles

There are 12 bosonic fundamental particles with spin 1 (vector) in the standard model, plus one additional not yet confirmed and spin zero (scalar) particle. They are beautifully unified by a so-called gauge model, formulated entirely in terms of symmetries. One would contemplate a U(1)\otimes SU(2)\otimes SU(3) gauge group. Let us emphasized here that gauge symmetry is not a real symmetry, but rather a very elegant mean to deal with constrained systems

The photon is the quantum of light, it is usually denoted \gamma and carries the electromagnetic interaction. It is massless, and this fact is related to the U(1) Quantum ElectroDynamic (QED) part of the standard gauge group which is not broken. Broken symmetries occur when the laws have a certain symmetry, but the ground state (vacuum) does not. So all the tower of states constructed form the vacuum do not exhibit this symmetry.
The 3 massive vector bosons W^+, W^- and Z^0 are responsible for the weak interaction. This is for instance what causes \beta decay of the proton into a neutron, at the quark level : d\rightarrow u + e^- + \bar{\nu}_e. There are also so-called "neutral currents" with the Z^0 able to go from one family to another. The gauge part is SU(2), but this symmetry is spontaneously broken, giving mass to the vector bosons by the so-called Higgs mechanism. The weak interaction is very peculiar, in that is does not respect some basic symmetries of Nature the other interactions seem to : especially P symmetry, the parity which consists in "taking the mirror image", is maximally broken : the \nu (if massless) is always left handed, while the \bar{\nu} (if massless) is always right handed. So physicists first hoped CP would not be broken, with addition of the exchange particle-antiparticle exchange C. It appears not to be the case, but then it is only slightly broken, such as in the decay modes of the some mesons. Today, we strongly believe that by adding time reversal, the all-important CPT symmetry is the fundamental for the theory. The spin-statistics theorem relies on this symmetry.
The 8 massless gluons, with gauge group the color SU(3). Gluons are also peculiar in that themselves carry color charge : a red gluon turn blue by emitting a red/antiblue gluon absorbed by a blue quark turning red for instance. This fact makes gluons interact with each other. There are three gluons and four gluons vertices in the standard model. The non-linearity makes the equation hopelessly unsolvable until now. Also, this is likely the cause of confinement, the property that color is always hidden in color-invariant bound states. Another striking feature is asymptotic freedom, the fact that at very low distances, or alternatively at high energy, quarks look like free particles.


The Glashow-Weinberg-Salam model has already unified the first two in the so-called electroweak unification U(1)\otimes SU(2)=U(2). This leads us to the Higgs mechanism : for each broken symmetry, a massless Goldstone boson appears. The Higgs mechanism permits this degree of freedom to be "eaten" by the massless gauge boson thus acquiring mass. We can even refine the model to make all fundamental particles massless acquiring mass by interaction with the Higgs scalar boson. This particle should soon be discovered at the LHC facility (Geneva)


Additional informations :

A good source of general information is wikipedia (http://en.wikipedia.org/wiki/Elementary_particle)

Another specifically on physics, somewhat at lower level but good illustrations is hyperphysics (http://hyperphysics.phy-astr.gsu.edu/hbase/particles/parcon.html)

The the particle adventure (http://particleadventure.org/particleadventure/) is the source of the link provided by Marlon, and this link leads to the gateway to it, a very friendly introduction.

The CERN (http://public.web.cern.ch/Public/Content/Chapters/AboutCERN/WhyStudyPrtcles/WhyStudyPrtcles-en.html) is the main European research center.

Of course, the Particle Data Group (http://pdg.lbl.gov/) has a reference site with all particles informations, and more, quite up-to-date and reliable,
The less technical particle adventure is also from the PDG.

etymology (http://laser.physics.sunysb.edu/~wise/wise187/janfeb2001/weblinks/physics_words.html)

[humanino]

Beyond the standard model :
There are many extensions to the standard model. Grand unification to include Quantum ChromoDynamics (QCD) and the Electroweak theory in a single SU(5) theory implies for instance proton decay, which has not been observed, and should anyway occur at very large time scales. Other schemes exist, such as SO(10) for instance. Those elegant theories cry for experimental evidences.

Also, anybody noticed that the historically first discovered interaction has not been mentioned yet : Gravity ! The graviton is supposed to be a massless spin-2 boson, an assumption from which Einstein's equation can be recovered. Yet it is difficult to identify the physical field of the graviton. It is usually defined as the departure of the metric from the flat Minkiwski one, but for two reasons this seems a priori wrong : this does not obviously look like a background independent formulation, whereas General Relativity is. Besides, fermions require the introduction of a "square-root" of the metric field, so this is more likely a candidate for the graviton. It is especially difficult to make sens of gravity in a quantum field theory, because it is notoriously non-renormalizable. Renormalization is a technical well-defined procedure to remove infinites in the theory, which appear form contributions where the validity of the model cannot be proven at least yet. The gravitation coupling constant having mass dimension -2, and one can easily see that an expansion in the coupling constant will not converge. So new physics must appear, in other terms Einstein beautiful geometrical formulation of gravity might only be a low-energy approximation to a deeper interaction.

[Orion1]

If I understand the course of the Standard Model based upon the above information, the next expected unification is:
U(2)\otimes SU(3)=U(3) \; \; 10^{14} GeV

Resulting in the Electrostrong unification and the production of a Goldstone boson called a X-boson.




The basic problem of "restoring the broken symmetry" between the strong and electroweak forces is that the strong force works only on colored particles and the leptons don't have color. You have to be able to convert quarks to leptons and vice versa. But this violates the conservation of baryon number, which is a strong experimental nuclear physics principle. Baryon number minus lepton number (B-L) would still be conserved as a quark is changed to an anti-lepton. The required mass of the exchange boson is 10^15 eV, which is more like the mass of a visible dust particle than that of a nuclear entity. This particle is called the X-boson.

One prediction of the grand unified theories is that the proton is unstable at some level.

In the 1970's, Sheldon Glashow and Howard Georgi proposed the grand unification of the strong, weak, and electromagnetic forces at energies above 10^14 GeV. If the ordinary concept of thermal energy applied at such times, it would require a temperature of 10^27 K for the average particle energy to be 10^14 GeV.


The next expected unification is:
U(3)\otimes SU(1)=U(4) \; \; 10^{19} GeV

Resulting in the Electrostrong Gravitation unification and the production of a Goldstone boson called a g-boson?.


Reference:
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/unify.html
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/unigrav.html#c1
http://en.wikipedia.org/wiki/SU%283%29XSU%282%29XU%281%29

[meteor]

There are various extensions of the Standard model including supersymmetric particles: The MSSM, and its constrained version, the constrained minimal supersymmetric Standard model (cMSSM ) ,(there are indeed various differents cMSSM: mSUGRA, the GMSB model, SGUT,...). Which of these theories offers better perspectives, which is more appreciated by the physics community?

[Orion1]

There are various extensions of the Standard model including supersymmetric particles: The MSSM, and its constrained version, the constrained minimal supersymmetric Standard model (cMSSM ) ,(there are indeed various differents cMSSM: mSUGRA, the GMSB model, SGUT,...). Which of these theories offers better perspectives, which is more appreciated by the physics community?

* Georgi-Glashow model -- SU(5)
* SO(10)
* Flipped SU(5) -- SU(5)×U(1)
* Pati-Salam model -- SU(4)×SU(2)×SU(2)
* Trinification -- SU(3)×SU(3)×SU(3)
* E6
* Technicolor models

Note: These models refer to Lie algebras not to Lie groups. The Lie group could be [SU(4)×SU(2)×SU(2)]/Z2, just to take a random example.

GUT models generically predict the existence of topological defects such as monopoles, cosmic strings, domain walls, and others. None have been observed and their absence is known as the monopole problem in cosmology.

As of 2004, there is still no hard evidence nature is described by a GUT theory. In fact, since the Higgs particle hasn't been discovered yet, it's not even certain if the Standard Model is fully accurate.

GUT theories are based on the idea of a "desert" with no new physics of several orders of magnitude in the renormalization group. However, it's a bit suspicious to run the renormalization group backwards because we don't know what new physics lie there and the property of universality suggests we can't tell easily either.



Reference:
http://en.wikipedia.org/wiki/Grand_unified_theory
http://en.wikipedia.org/wiki/Magnetic_monopoles
http://en.wikipedia.org/wiki/Cosmic_strings
http://en.wikipedia.org/wiki/Monopole_problem

[zefram_c]

I enjoyed reading this thread - it is a very good introduction to the SM for the uninitiated. However, I think there's a slight technical inaccuracy here:
The 3 massive vector bosons W+, W- and Z0 are responsible for the weak interaction. This is for instance what causes beta decay of the proton into a neutron, at the quark level : d\rightarrow u + e^- + \bar{\nu}_e. There are also so-called "neutral currents" with the Z0 able to go from one family to another. The gauge part is SU(2), but this symmetry is spontaneously broken, giving mass to the vector bosons by the so-called Higgs mechanism. This is not *entirely* correct. When the SU(2) group alone is gauged, the result is three vector bosons. However, they are not the W and Z. Two of them are indeed the mediators of charged currents (the W+ and W-). However, the third boson is not the Z - it is usually denoted the W0 in texts. The coupling of this W0 to fermions doesn't match the experimentally observed weak neutral currents.

Enter the remaining group, U(1)Y. This group is also part of the electroweak interaction, and comes with its own neutral boson, usually denoted B. The B is also non-physical. What happens in symmetry breaking is that the B and the W0 mix and produce two orthogonal states: the photon and the Z. The latter also acquires mass, while the former does not, by the choice of the vacuum expectation value of the Higgs. The Z is the physical mediator of weak neutral currents, and the photon mediates the (seemingly unrelated) EM interaction. Being a mixture of the two gauge fields is what gives the Z the correct couplings to the fermions.

The point of all this is that the SU(2) gauge group alone is insufficient to account for the weak interactions (charged and neutral currents), even after symmetry breaking. This was actually going to be part of a quiz I was planning to post :smile:

[meteor]

* Georgi-Glashow model -- SU(5)
* SO(10)
* Flipped SU(5) -- SU(5)×U(1)
* Pati-Salam model -- SU(4)×SU(2)×SU(2)
* Trinification -- SU(3)×SU(3)×SU(3)
* E6
* Technicolor models

This is a god summary of GUT. Some of these GUT (all?) propose the existence of particles not appearing in the SM. For example, the technicolor model proposes tthe existence of the coloron. Flipped SU(5) proposes the existence of the crypton

In what year appeared E6 GUT?

[humanino]

The original, I cannot provide access but reference : Gursey F, Ramond P, Sikivie P. "A Universal Gauge Theory Model Based on E_6", Phys. Lett. B60:177,1976.

A nice introduction to begin with :
"The quest for unification" by Witten (www-library.desy.de/preparch/desy/proc/proc02-02/Proceedings/Hertz/hertz_pr.pdf)

A recent paper by N. Maekawa (University of Kyoto) with 30 references, and phenomenology :
E6 Unification, large neutrino mixings, and SUSY flavor problem (xxx.arxiv.cornell.edu/pdf/hep-ph/0402224)

Plus three papers by Gregory W. Anderson, Tomas Blazek :

E_6 unification model building III. Clebsch-Gordan coefficients in E_6 tensor products of the 27 with higher dimensional representations here (http://www.arxiv.org/abs/hep-ph/0101349)

E_6 unification model building II : Clebsch-Gordan coefficients of 78\otimes78 here (http://www.arxiv.org/abs/hep-ph/0006017)

E_6 unification model building I: Clebsch-Gordan coefficients of 27\otimes \ol{27} here (http://www.arxiv.org/abs/hep-ph/9912365)

[humanino]

The non-discovery of the Higgs boson is anticipated for a while. Theoreticians lacking data cannot bet on only one possibility. Anyway, we do not know yet, and I like "minimal hypothesis" models. So here is a recent paper about electroweak theory :
Massive Gauge Bosons in Yang-Mills Theory without Higgs Mechanism (http://www.arxiv.org/abs/hep-ph/0409340)
whose title speaks by itslef.
It is short, and gives a brief introduction to playing with the standard notations. Ghosts are discussed, renormalization is very likely, yet parity violation as well as down quark mixing are not included, at least at this step.

[humanino]

A very nice introduction to the standard electroweak model :
introduction (hep.ift.unesp.br/SPRACE/people%20page/novaes/papers/swieca.pdf)
to balance with the previous paper :smile:

[marlon]

when studying electrowrak interactions the first question should be : why using this famous V - A current ??? What is it and what does it do...
Some nice anwers are provided on this site, just look at the "sessions" on the bottom of the page. They may be introductory but this is the main intention of this thread...you will acquire a nice perspective on these subjects...

http://www.shef.ac.uk/physics/teaching/phy604/electroweak.html

enjoy

regards
marlon

[marlon]

This is a nice site on quarkconfinement...very interesting...i did my master-thesis on this subject. "One of the biggest problems in contemporary theoretical physics : why are quarks confined ???"

In this paper magnetical monopoles are used...very spectacular :tongue2:

http://arxiv.org/PS_cache/hep-ph/pdf/0310/0310102.pdf
regards
marlon

ps : it may take a while before the pdf-file is loaded so be patient...you will be extensively rewarded... :biggrin:

[humanino]

Grand Unification and Physics Beyond the Standard Model (http://www.arxiv.org/abs/hep-ph/0410023)
Recent progress in some selected areas of grand unification and physics beyond the standard model is reviewed. Topics include gauge coupling unification, SU(5), SO(10), symmetry breaking mechanisms, finite field theory: SU(3)^3, leptonic color: SU(3)^4, chiral color and quark-lepton nonuniversality: SU(3)^6.
Ernest Ma (UC Riverside)
12 pages, no figure, talk at V-SILAFAE, Lima, Peru (July 2004)

Very short paper, good for introduction to the beginner.

[Haelfix]

If you like minimality, you probably should go with non SUSY SO(10). Its also amongst the few GUTs with some amount of experimental evidence (neutrino mixing). There are of course a number of inequivalent ways of breaking the group.

Normally we live in the 16 of SO(10), and like to break it down to SU(5), which we understand a little better. However, you can also break it via the Salam left-right model (SU(4)*Su(2)*SU(2))

However it has a few problems (all GUTS have problems), namely the Higgs sector involves some nasty fine tuning. So then people sometimes boost the representation up to some big number (127 or something like that, I forget), and you end up with some sort of Higgs SeeSaw mechanism.

The only GUT that is ruled out atm, is non SUSY SU(5), b/c of proton decay bounds.

[marlon]

This is for all you out there, who are wondering about gluons and pions...


The strong force holds baryons and mesons together and is mediated through gluon-exchange between the constituent quarks. I have studied models (dual abelian Higgs-model) where the distance between such quarks (in a baryon or meson) is estimated to be less then 0.7fm when we assume that the three quarks of the baryon are placed on the corners of a triangle. In this case the whole system is to be looked at as one three-body-problem. Bigger inter-quark-distances will give rise to a Y-shaped structure.

The atomic nucleus is bound together by the residual strong force and is mediated by the lightest mesons called the pions. Now, when two baryons (like a proton and a neutron) come close enough to each other, the valence quarks of the first baryon will interact with the valence quarks of the second baryon. What happens is this : two valence quarks from the two different baryons will feel a linear potential between them. When they are pulled apart, the potential rises which leads to an unstable connection between the two quarks. This leads to the fact that the connection is broken apart and the available energy is used to form a quark-anti-quark pair which is the pion. Energy is converted into matter via E =mc² and when enough energy is available this created pair can exists for quite a while because of Heisenberg uncertainty. All these things are described by QFT, which needs to be seen as the unification of special relativity and QM because of the previous two reasons (E=mc² and Heisenberg uncertainty from QM). At distances of about 1fm, the quark pair creation speed is maximal, yielding a maximal interaction between baryons of the atomic nucleus.

It needs to be said that these are result that are predicted by the denoted model above and other models will give you other numbers, although they are in the same range. If you wish i can give you a link to the model i mentioned as some sort of reference, but you are gonna have to know your QFT thoroughly because it is heavy material.

The main difference between gluons and pions is the fact that gluons are elementary in nature, pions are not. Basically this means that gluons arise because of the local colour symmetry of QCD, which provides a fundamental
description of this field theory. The quark-colours can be used to write down this entire theory at it's most fundamental level.

Also notice the fact that pions are the lightest meson. Thus they are constituted out of TWO quarks. The reason for this is that one quark would require an quasi "infinite" amount of energy to exist as a single identity. Reason ? : well, asymptotic freedom. The strong force coupling constant (which expresses the strength of this interaction) becomes smaller when energy rises. Basically this means that high-energy-quarks (for example quarks with high kinetic energy in accelerators) will be less tightly bound to each other because of this principle. Clearly, at the vaccuum-state, energy is low and quarks will therefore never arise as single identities. This property is called the quark-confinement and this years Nobel prize for physics is awarded to the "discoverers" of this principle (ie asymptotic freedom).


regards
marlon

[marlon]

Hello everyone,...

I have posted this somewhere else a few days ago, but i think it is a good idea to put this text on "mass in QFT" in our joint encyclopedia...


Dynamical mass-generation refers to the vaccuum condensates in field theory...It can be shown that the perturbative vaccuum is unstable and the vaccuum energy can be lowered when certain condensates (the vaccuum condensates) are created. These condensates do not exist (i mean, the expectation value of them is zero) when they are calculated with perturbation theory. They reason for this is that symmetry of the physical models at hand do not allow a non-zero expectation value. In a non-perturbative field theory (like low energy-QCD) these condensates DO occur and as a consequence of this some symmetries of the models are broken. When symmetry is broken, mass is generated through the Higgs-mechanism. These condensates are thus responsible for giving massless-elementary particles some dynamically generated mass. For example the QCD Lagrangian contains massless quarks and exhibits as a consequence of this chiral symmetry. When vaccuumcondensates are allowed (low-energies or non-perturbative QCD) these quark-antiquarkpairs will break this chiral symmetry and will give the quark mass.

Effective mass is a concept that QFT took over from solid state physics. As an example : consider many electrons that interact with each other. This is one many-particle system with many coupled differential equations. We cannot solve this so what's the way out? Well take one electron and put all the "interactions" it makes with the surrounding electrons into the mass of the electron. What we get is the equation of motion (with adapted mass = effective mass)of an electron that moves around in the vaccuum, because all the interactions with neighbors are put into the effective mass. basically what you have done here is convert one many-body problem into many one body problems that we CAN solve...

Keep in mind that this is a simplified picture but it gives you an image...An effective field theory is a field theory of which the degrees of freedom are not elementary. For example , the degrees of freedom of QCD are quarks, which are elementary particles. In QHD, the degrees if freedom are hadrons (particles that consist out of quarks and feel the strong force), but they are not elementary since they are built out of quarks...

Particles are elementary when they can be used as a FUNDAMENTAL representation of the symmetry-group of the Lagrangian of the field theory...Like quarks with three colours form the fundamental representation of SU(3), the local colour symmetry of QCD which generates 8 gauge bosons (you know, the gluons...)

regards
marlon

[humanino]

ok with me
but Marlon started this

and I would like to add something to your last post Marlon. I already wanted to to add it in the other thread : there are other possibilities to generate mass dynamically, among which one I want to mention because of its role in QCD : instantons are also able to break chiral symmetry and give non-vanishing value to the quark condensate. In fact, instanton-based calculations are much in agreement with actual value of the quark condensate (this quark condensate is the order parameter in the phase transition where the breaking of chiral symmetry occurs). Unfortunately, I do not have much time right now to write an account on this.

Also in your post, should not QHC be replaced with QHD (quantum hadro-dynamics) ?

[marlon]

ok with me
but Marlon started this

and I would like to add something to your last post Marlon. I already wanted to to add it in the other thread : there are other possibilities to generate mass dynamically, among which one I want to mention because of its role in QCD : instantons are also able to break chiral symmetry and give non-vanishing value to the quark condensate. In fact, instanton-based calculations are much in agreement with actual value of the quark condensate (this quark condensate is the order parameter in the phase transition where the breaking of chiral symmetry occurs). Unfortunately, I do not have much time right now to write an account on this.

Indeed this is very correct... I am planning to write down a text on instantons. Basically they are the QFT-variant of what we call tunneling in QM. The QM-tunneling lowers the vaccuum-energy-value and in QFT it is the instantons that are able to tunnel from one vacuum-gauge-configuration to another...

See this nice link for an indept explanation by Gerardus t'Hooft :
http://xxx.lanl.gov/abs/hep-th/0010225


Also in your post, should not QHC be replaced with QHD (quantum hadro-dynamics) ?
Indeed, thanks for the correction...

regards
marlon

[marlon]

This is a nice site on quarkconfinement...very interesting...i did my master-thesis on this subject. "One of the biggest problems in contemporary theoretical physics : why are quarks confined ???"

In this paper magnetical monopoles are used...very spectacular :tongue2:

http://arxiv.org/PS_cache/hep-ph/pdf/0310/0310102.pdf
regards
marlon

ps : it may take a while before the pdf-file is loaded so be patient...you will be extensively rewarded... :biggrin:

Magnetic monopoles are looked at as being point particles in QFT. Like i stated before, for example in the dual abelian Higgsmodell, they are used in order to describe the dual analogon of the Meissner-effect that pushes the magnetic field lines out of a superconductive specimen...The actual charge of such a monopole is determined in those points of the space-time where the gauge of the field theory is undetermined. This means, where this gauge becomes singular...


I attached a zip-document in which quantization of magnetic charge is explained. The reason for this phenomenon is the Dirac-quantization which makes sure that the Dirac string is not noticable when you pass through a surface that is subtended by a deformed world-line

regards
marlon

[marlon]

http://www.arxiv.org/abs/hep-ph/0111062
http://www.arxiv.org/abs/hep-ph/9906526
http://www.arxiv.org/abs/hep-ph/9910526

These are a few links on magnetic monopoles...Beware : A solid QFT-knowledge is required...these papers are far from introductory...

regards
marlon

[davidmerritt]

I am sure Humanino will have no problem with that :wink:

regards
marlon

Excellent I'll post them sometime soon..... just thought I'd add one or two of my links on the topic of the standard model and EPP :approve:

UK particle physics and astronomy research council
http://www.pparc.ac.uk

University College London's course on Particle and Nuclear physics
http://www.hep.ucl.ac.uk/~jthomas/notes3c24.html

Queen Mary (westfield) London EPP course
http://hepwww.ph.qmw.ac.uk/epp/lectures.shtml

Sheffield University Particle Physics courses
http://www.shef.ac.uk/physics/research/pppa/teaching.htm

Durham university's Institute for Particle Physics Phenomenology (what a name!)
http://www.ippp.dur.ac.uk


My rubish notes on the Higgs Boson

There is something missing from modern particle physics, that something is the proof of the existence of the Higgs Boson (which only has mass , no charge or spin). In order for Gauge invariance to hold there needs to be a mechanism by which gauge bosons can acquire mass. The process which provides mass endowment is called the ‘Higgs Mechanism’.

The standard model (explained above) predicts the existence of the Higgs particle; however, it does not predict an accurate mass. The research effort is lead by the European CERN project, a collection of large colliders, the focus of which was the LEP. Unfortunately the LEP (Large Electron Positron) collider has been dismantled in favour of the construction of the LHC (large hadron collider) due to be in service in 2007. A suspect result at CERN caused them to announce that they’d found the Higgs particle, but they’d miscalculated. The research group at FNAL near Chicago are hoping to identify the elusive particle, however there is a growing number of concerned particle physicists speculating that the standard model is flawed. As the power of the colliders increases over 140GeV scientists become increasingly sceptical of existence of the Higgs boson. Explaining how particles gain mass will remain a mystery for the time being!

and some links:
• http://news.bbc.co.uk/1/hi/sci/tech/3546973.stm
• http://www.newscientist.com/news/news.jsp?id=ns99991649
• http://www.cerncourier.com/main/article/39/9/12

[marlon]

This years Physics Nobel Prize was awarded for the discovery of
asymptotic freedom of the strong force. This means that the strong
force gets weaker in strength when energy gets higher. For example
consider two quarks that interact with each other via the strong force.
When they have a very high kinetic energy they will be less tightly
bound because of this high energy (strong interaction is weaker). This
also results in the fact that no single quark can be found in the
vaccuumstate (lowest energy or groundstate). This phenomenon is called
quark confinement. Quarks will always sit per two (meson) or per three
(baryon, like the proton or neutron).

Quarks were discovered (well, i mean they were "observed"
experimentally) by performing deep inelastic scattering experiments
with electrons onto protons. By studying the electromagnetic
interactions, scientist found out that some fraction of the proton
(Feynmann called these fractions partons)was "knocked out" by the
high-energy-incident electron. Thus suggesting that protons were
constituted out of something more fundamental. Another suggestion for
this was the fact that the neutron did exhibit a nuclear magnetic
moment that was NOT equal to (so not neutral)...

Theoretically quarks were implemented via group theory in the famous
Eightfold-way...Thus QCD was born, the field theory that describes the
quark-interactions at best via 8 gauge bosons called gluons. Each quark
has a flavour bottom-, ...quarks) and each such flavour also has
a colour-quantum-number (Red,Green,Blue)...These quantumnumbers
"decide" via conservation laws how quarks interact with each other...

regards
marlon

[marlon]

If anyone is interested in a simple explanation of asymptotic freedom and the concept of screening versus anti-screening...well, check out my journal...just look for "ON THE ORIGIN OF "CONFINED" SPECIES"

regards
marlon

i also included the link to the Nobel lectures on this years physics Nobel Prize, as a reference...great stuff...again thanks to marcus for providing us with such great links..i suggest you all check it out...

[marlon]

I have written an introductory text on the meaning and role of the Higgs field in QFT. If you are interested, please check out my journal and read the "what is the higgs field"-entry


regards
marlon

ps : any comments are always welcome...both good as well as bad...

[selfAdjoint]

Marlon, could you clarify the transition from your example of electron spins to the mass-acquiring Higgs field? Surely you don't mean that the spin lineup of the elecrons is due to a Higgs mechanism? But your text reads that way.

[marlon]

Marlon, could you clarify the transition from your example of electron spins to the mass-acquiring Higgs field? Surely you don't mean that the spin lineup of the elecrons is due to a Higgs mechanism? But your text reads that way.


Thanks for the remark sA..

Ofcourse as you know the transition is certainly not triggered by the Higgs field. It originates when the temperature of the specimen goes under a certain transition value. I mean, when the nearest neigbor interaction between two spins (the one tells the other to postion itself into the same direction : this is the definition of ferromagnetism) becomes dominant over the "chaos among the spins" caused by higher temperatue values of the specimen. In easier language : when the temperature is low enough there won't be enough kinetic energy of the particles at hand, to disturb the natural tendency of spin-ordening that is caracteristic for ferromagnetism...


regards
marlon

[marlon]

http://www.physicsforums.com/journal.php?s=&action=view&journalid=13790&perpage=10&page=2


In my journal i wrote a text as an attempt to explain the Higgs-particle and how it can be accounted for the mass-generation of elementary particles. Also (see the above link) i wrote a reference to a site. This site gives the results of the 1993 HIGGS-CONTEST...Wanna know what this is, check out my journal...


marlon

[Astronuc]

Another simple overview of elementary particles - Fundamental Particles and Interactions (http://www.cpepweb.org/particles.html)

Look for the Chart of Fundamental Particles and Interactions

[marlon]

http://www.physicsforums.com/journal.php?s=&journalid=13790&action=view#PREONS:%20elementary%20particle%20buil ders%20and%20possible%20dark%20matter

Go check out the new text on Preons. This is hot new stuff but still very speculative. I also included a reference to a peer reviewed text given to me here on this forum. If anyone has other links on preons, just let me know.


Preons are assumed to be more fundamental the quarks (STILL SPECULATIVE AND NOT PROVEN!!!!!!!!) and they are a good candidate for dark matter...
regards
marlon

[pelastration]

Can I find somewhere on Internet a full overview or tree scheme about all particles and all their possible decays?

Thanks.

Dirk

[marlon]

Can I find somewhere on Internet a full overview or tree scheme about all particles and all their possible decays?

Thanks.

Dirk
Hallo Dirk,

This is an overview from CERN

http://pdg.web.cern.ch/pdg/particleadventure/frameless/chart.html

Marlon aka Nikolaas

[pelastration]

Hallo Dirk,
This is an overview from CERN
http://pdg.web.cern.ch/pdg/particleadventure/frameless/chart.html
Marlon aka Nikolaas
Thanks Marlon,
You provided already in previous posts good links.

yes I know the CERN chart, it's very interesting. But what I am looking for is a more in depth overview. A tree scheme - the kind as you see in the image on http://abyss.uoregon.edu/~js/glossary/quarks.html. For example the CERN chart says there are 120 Baryons and 140 type of mesons. Any idea where we can find those?

regards
dirk

[marlon]

http://home.cwru.edu/~sjr16/advanced/extras_particlephys.html

this site gives a few more

marlon

[marlon]

http://pdg.web.cern.ch/pdg/2004/listings/contents_listings.html

HERE IS EVERYTHING THAT YOU NEED, from CERN

marlon

[marlon]

What are dynamical quarks and why is the hadronmass bigger then the sum of the constituent quarkmasses (which is the opposite to the mass of nucleus being smaller then the sum of the constituent nucleon masses, because of the binding energy):

Check out the lattice QCD entry in my journal, there are some links from the CERN
http://www.physicsforums.com/journal.php?s=&journalid=13790&action=view

ps also, check out the "is energy conservation respected in beta decay"-entry

marlon

[marlon]

I have had many questions on virtual particles and vacuum fluctuations. That is why i decided to write down this text in my journal...

Enjoy:
http://www.physicsforums.com/journal.php?s=&journalid=13790&action=view

Suggestions and comments are always welcome, as usual

I also wrote a text on grouptheory in QFT, please let me know your thoughts as to whether the content is clear enough

Grazie mille

marlon

[Astronuc]

Found this - http://www.benbest.com/science/standard.html

The Standard Model of Particle Physics
A Simplified Summary
by Ben Best

maybe a bit redundant.

[marlon]

Thanks Astronuc for the link. I also want to give this link to these introductory lectures notes on nuclear physics, provided by Humanino :

http://hitoshi.berkeley.edu/129A/strong1.pdf

marlon

ps : here is some additional info on both gluons and pions :

http://www.physicsforums.com/journal.php?s=&action=view&journalid=13790&perpage=10&page=10

and

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/expar.html

[marlon]

Hi,

I Just wanted to point out this very interesting thread on the parity-conservation of the neutral pi meson decay.

http://www.physicsforums.com/showthread.php?t=68715

regards
marlon

ps : if there are any questions, please don't hesitate...

[marlon]

The beta decay really announced the advent of QFT. In the beginning some scientists thought that the electron really came out of the nucleus, ofcourse this is wrong. What happens is this : the electron is created "out of nothing". This means that the energy involved in the beta decay is used to create this electron out of the vacuum. This kind of process is only possible in QFT and that is why beta decay was one of the first major breakthroughs of QFT.

Also, keep in mind that negative beta decay (neutron ---> proton) is a particle decay mode while the positive beta decay (proton --> neutron) is a nuclear decay mode because the neutron is more heavy then the proton. This proton can only decay (due to energyconservation) when it is surrounded by many other protons in a nucleus...Part of the energy coming from proton-proton-interactions can also account for mass via E=mc².

Beta plus decay commonly means the basic process p->n + e++v. It is a nuclear decay mode in that it can only happen if the proton is inside a heavier nucleus and the final state nucleus is more tightly bound; the process is forbidden in free space by energy conservation since a neutron alone is heavier than a proton

marlon

More info here : http://www.physicsforums.com/showthread.php?t=66287

[marlon]

I have posted this in my journal but i thought it might be nice to put this text in this thread too...

Many students have difficulties understanding what 'transforming like a vector or tensor' really means in physics. Here is the solution...Before you begin, be sure that you know really well what a tensor is...if you do not, check out my 'what is a tensor' entry...


A spinor is a special kind of vector. I mean, it has the property that if you rotate it 360° you get the exact opposite (A ---> -A) of what you originally rotated. Rotate another 360° and you get where you started off in the first of the two rotations (A---> -A--->A).

Now let us look at the rotationgroup SO(3) or even any other group, it don't matter :

An object v transforms as a vector if you can write v' = Uv where U is a representation for the group in question, U represents a rotation. Another way to say this is if you transform an object under a certain group, the 'image' of this transformation will be a linear combination of the object that you transformed. So transforming like a vector really means that the object you transform will be written out as a linear combination of it's components after the transformation.

An object transforms as a tensor if you can write v'=UU'U''v
So this means that v transforms 'as a product of vectors' because of the multiple U-matrices.

Now, transforming like a spinor really means that the object tranforms like a vector (you know what that means) but not just any vector. This is a special case, where the U-matrix does not represent just any transformation but a transformation that gives you the opposite of the initial object after a rotation of 360°.


Rotations are generated by the J-operator. J = 1 for example means that the quantity at hand transforms like a vector under three dimensional rotations. And the other way around, if an object transforms like a vector under these 3-D rotations, you know it will have spin J =1 and thus three degrees of freedom. YES, because the fundamental representations will be (3*1)-matrices which have three components...Spin 2 is a tensor and Spin 0 is a scalar...ODD SPIN IS A SPINOR


One can recognize a spinor by the way it transforms under a group. If the generator is a Pauli-matrix you are done...Just like in the case of SU(3), if you now the generator is a GellMann matrix, you know you are working with anobject in the adjoint representation and these objects are GLUONS. Let us look into gluons :

There are 3 colors. Why ? Well, becauseSU(3) is the group of 3 x 3 unitary matrices with determinant 1. The most easy matrix such an SU(3) matrix can work on is the 3*1-colum-matrix (ythis one has three components and is called the fundamental representation). SU(3) is the symmetry group of the strong force. What this means is that, as far as the strong force is concerned, the state of a particle is given by a vector in some vector space on which elements of SU(3) act as linear (in fact unitary) operators.

We say the particle "transforms under some representation of SU(3)".

For example, since elements of SU(3) are 3 x 3 matrices,like i already said before , they can act on column vectors by matrix multiplication. This gives a 3-dimensional representation of SU(3). The quarks are represented by this 3*1-matrix. The antiquarks can be represented by row vectors because we can multiply a 3*3-matrix with a row vector on the LEFT side of the matrix.

The gluons are represented by the socalled adjoint representation which consits out of traceless 3*3matrices. It can be seen that a row of such a matrix represents one quark colour and a colom of such a matrix represents a anti-colour. each gluon is therefore constructed out of a colour-anticolour combination. Given that there are 3 such colours and anticolours, you would expect 9 gluons. However there are only eight . Can you see why ???

ps : you know that the colours are red green and blue and it is the postulate of QCD that the sum of these three represents colour-neutrality !!! This is the main law that needs to be respected : in interactions : the sum of all involved colours must be WHITE


regards

marlon


ps : maybe others can add or correct ???

[tritonphysics]

all these particles are great, but let's ask one basic question.

When you see those particle tracks, specifically the electron and positron
slowing down in a spiral ... is this occurring in a plane, or is there a
"z" component to the motion ? Is it really a helix ? with gradually
decreasing radius?

Seems like this motion is fundamental to understanding
particle physics ...

[marlon]

all these particles are great, but let's ask one basic question.

When you see those particle tracks, specifically the electron and positron
slowing down in a spiral ... is this occurring in a plane, or is there a
"z" component to the motion ? Is it really a helix ? with gradually
decreasing radius?



When the particle enters the magnetic field in a plane perpendicular to that field, the Lorentz force will make sure that it moves in a circular orbit. Due to collisions with surrounding particles (like in an ionization chamber or a bubble chamber) the radius will decrease. The helix (three dimensions) only occurs when the initial velocity of the particle is not perpendicular to the B-field. Then the motion can be composed out of a circular motion in a plane perpendicular to the B-field lines and a constant velocity motion along a straight line. The superposition of these two motions results in the helix

marlon

[marlon]

Quarks have spin 1/2 and a proton has spin 1/2. There are three quarks in one proton, so you'd think that a proton spin must be 3/2. Ofcourse this is NOT the case.

Ever wondered why that is ?

Here is the answer : http://www.physicsforums.com/showthread.php?t=70409


Ps : it's this 'system' that also solves the apparent parity-violation in the neutral pion decay...I refer to the previous made post in this thread, dealing with that matter...


marlon

[Gamble]

Hi, I am programming a computer model of atom nucleus at the moment. Could you help me with the following two questions:

Does standard model give a forumla that describes strong force between two quarks as a function of distance?

Given a mass of each quark in a nucleon, is there a formula that gives out the mass of nucleon itself?

[marlon]

Hi, I am programming a computer model of atom nucleus at the moment. Could you help me with the following two questions:

Does standard model give a forumla that describes strong force between two quarks as a function of distance?

Given a mass of each quark in a nucleon, is there a formula that gives out the mass of nucleon itself?

Well, that's quite alot that you are asking. I mean, what exactly do you want to achieve ? Does this need to be a lattice QCD-thing (i suppose so). the clue will be to find the right information. I suppose you are very well trained in QCD, so you should have access to the landmark papers on this topic.

regards
marlon

[marlon]

Ofcourse,seeing as how our most powerful supercomputers struggle just to model a single proton or neutron, I don't think full QCD is going to be an efficient way to model the nucleus.

As for links, how about something like this: Hartree-Fock-Bogoliubov Mass Formula
Just Google the name...

Here is a nice overview with various references :
http://www.apsidium.com/number/nuclear_masses.pdf

marlon

[humanino]

Here is a very nice introduction to instantons by Diakonov. He points out that, surprisingly enough, the linear rising potential between quarks probably is not the key to the problem of confinement. This simple picture of the glue-tube string is probably far too simple to account for what is realized in Nature.
Instantons and baryon dynamics (http://www.arxiv.org/abs/hep-ph/0205054)
I explain how instantons break chiral symmetry and how do they bind quarks in baryons. The confining potential is possibly irrelevant for the task.

[marlon]

Wanna know more about the words intrinsic and helicity ? :

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino3.html#c1

Attention : the spin S of a particle is called the intrinsic angular momentum. After reading this text, i hope you have a clear understanding of what that means. Also a particle with certain spin does NOT actually rotate around its axis, this is a common misconception. The rotation-part is an abstract grouptheoretical formulation that arises because if certain symmetries that need to be respected.


This thread explains everything on orbital angular momentum and it's connection to spin : http://www.physicsforums.com/showthread.php?t=71642
It's important to realize how an atom can interact with an extern magnetic field. This is why the concept of magnetic moment has been invented. it's all in this thread, check it out people....


regards
marlon

[marlon]

Hey, guys and girls,

I have written a little and simple text in order to eliminate some common misconceptions of QFT (well QM too ofcourse).

NUMBER ONE:
Besides, i would like to add this : people always ask how do electrons orbiting the nucleus prevent from falling in ? Well, this question itself contains incorrect formulations. the electron does NOT orbit the nucleus. Just look at the lowest energy orbital : the s-orbital. It is a sphere around the nucleus. So , prior to any kind of measurement, the electron is basically everywhere around the nucleus.
Same goes for any other orbital (ofcourse the have another shape)

QM proves us that the kinetic energy is higher when being closer to the nucleus, but the potential energy is lower (more negative). The sum of these two really yields a stable equilibrium throughout all energy levels.


NUMBER TWO:
People always mix QFT with QM. A wave function that describes an electron is not a wave that IS an electron. It just contains the electron-properties. This is QM

In QFT, particles arise as fluctuations of fields but the fields themselves ARE NOT particles. Particles arise (and also forces) as actual vibrations of these fields. Just think of the mattress analogy that i have used throughout my entire journal


NUMBER THREE:
An electron has a spin (intrinsic angular momentum), but it does NOT actually rotate around its axis, guys. The 'rotational nature' of spin comes from the behavior of the Dirac wavefunction (this is a matrix that represents a physical state and arises when solving the Dirac equation. This equation describes a fermion : a particle with non-integer spin) under coordinate-transformations (which are called the rotations).

With behavior i mean : how does the physics change if we interchange the components of this Dirac spinor, if we change the parity, if we apply coordinate transformations to the wavefunction and so on....For example, if we rotate the wavefunction 360°, do we still get the same physical laws...You see the pattern ???

It is this specific behavior that yields the name SPINOR because if you rotate it 360°, you get the opposite value. Now, changing coordinates (represented by rotations) and looking how the physics changes or not, is NOT THE SAME as actually rotating. So, spin arises thanks to symmetries involved but there is no actual rotation.

ps : be sure that you know what 'intrinsic' means


NUMBER FOUR:
Finally : there ain't two ways of describing light : The particle wave-duality exists only because of our 'classical minds' ; we wanna think in terms of either particles or waves. There is no problem with that but we do need to keep the correct perspective on things here. First of all 'particles' in this case does not mean little objects with finite boundaries. It means little finite pieces of energy (this is the actual quantization , right ?)

Secondly, in QM we have experiments that are better explained with the wave-like notion (eg the double slit experiment) and we have those experiments that are better described with the particle-like notion (eg photo-electric effect). However in the end both descriptions are just ONE SINGLE way of describing the physical properties of light....that is all.


NUMBER FIVE:
Another common misconception is the fact that the photo-electric effect proved the existence of photons. That is not true because this photo-electric effect can be described in terms of the wavelike-notion of the incident EM-radiation too. It is only the atoms of the target electrode that are treated with QM. However, the particle-like notion of light is suggested by this experiment. If you wanna read more, check out my journal and find the article on creating an entangeled photon-state in an undergrad lab

Here's the article : Create entangled photons yourself in an undergrad laboratory :
http://marcus.whitman.edu/~beckmk/Q...r/Thorn_ajp.pdf


regards
marlon

[marlon]

Standard Model : SU(3)xSU(2)xU(1) gauge theory
Gauge bosons : 8 SU(3) color-coupled gluons, 3 SU(2) 2 W\'s and 1 Z-boson, 1 U(1) B the foton

In the unbroken SU(2)xU(1) gauge theory of the electroweak interactions, there are four fields. These fields are usually called W1, W2, W3, (from SU(2)) and B (from U(1))

After spontaneous symmetry breaking due to the Higgs mechanism, you still have four fields, but three of them gain masses. The W1 and W2 mix to form the W+ and W- and the W3 mixes with the B to form the Z0. The rest of the W3-B mix remains massless and is the photon (often called A and belonging to the remnant U(1) symmetry of QED).


Three generations of spinor fermions divided into:
1) colored doublet left-quarks (ups and downs)
2) doublet left-leptons (electrons and neutrinos)
3) colored right-ups
4) colored right-downs
5) right-electrons
with various hypercharges

The singlet states correspond to particles that don't feel the weak force like 3,4 and 5...

Or you can classify like this :

Mass Particles

---A. Six quarks
------1. Up, down, strange, charm, top, bottom
------2. Combine to form Hadrons in two varieties: baryons, mesons

---B. Six leptons
------1. Three with charge (Tau, muon, electron)
------2. Three neutrinos each corresponding to a charged lepton
------3. Decay, don't combine

II. Three types of interactions mediated by force particles

---A. Strong (gluons)
---B. Electroweak
------1. Electromagnetic (photon)
------2. Weak (Z, W+, W- bosons)
---C. Gravity (graviton?)

Can you understand "the why" of this classification ?
marlon

[arivero]

---A. Six quarks
------1. Up, down, strange, charm, top, bottom
------2. Combine to form Hadrons in two varieties: baryons, mesons

---B. Six leptons
------1. Three with charge (Tau, muon, electron)
------2. Three neutrinos each corresponding to a charged lepton
------3. Decay, don't combine

Can you understand "the why" of this classification ?
marlon

No.

I can not understand why the leptons are classified according electric charge, but the quarks are not.

[Meir Achuz]

The quarks are classified like the leptons.
The quarks come in 3 doublets. (u,d),(c,s),(t,b).
In each doublet the upper quark has a charge +e more than the lower quark.
This is just like the leptons. Details are related to the groups involved.
The group structure is S(3)XSU(2)XU(1).
Why the quarks are +2/3 and -1/3 is involved with hypercharge and group details.
If the GUT is SU(5), the breakdown into this structure is unique,
but th proton decays.

[marlon]

Here is a nice introductory story on the Top Quark, presented by Fermilab

http://www-ed.fnal.gov/samplers/hsphys/activities/student/index.html

Also check out my TOP QUARK entry in my journal :
http://www.physicsforums.com/journal.php?s=&journalid=13790&action=view

regards
marlon

[marlon]

Let's start the elementary particle journey

http://particleadventure.org/particleadventure/

regards
marlon

[Astronuc]

Some useful information regarding particles.

Fermions (http://en.wikipedia.org/wiki/Fermions)

Fermi-Dirac Statistics (http://en.wikipedia.org/wiki/Fermi-Dirac_statistics)

Pauli Exclusion Principle (http://en.wikipedia.org/wiki/Pauli_exclusion_principle)

Bosons (http://en.wikipedia.org/wiki/Boson)

Bose-Einstein Statistics (http://en.wikipedia.org/wiki/Bose-Einstein_statistics)

Spin (http://en.wikipedia.org/wiki/Spin_%28physics%29)

Quantum Electrodynamics (QED) (http://en.wikipedia.org/wiki/Quantum_electrodynamics)

Quantum Chromodynamics (QCD) (http://en.wikipedia.org/wiki/Quantum_chromodynamics)

Quantum field theory (QFT) (http://en.wikipedia.org/wiki/Quantum_field_theory)

[Astronuc]

This is a cool website if your into Particle Physics - which I am among many other things :biggrin: - but I have to get up to speed on QCD, QFT, GUT and other things.

Stanford Linear Accelerator Center Virtual Visitor Center (http://www2.slac.stanford.edu/vvc/)

Also -

High Energy Cosmic Rays (http://www2.slac.stanford.edu/vvc/cosmicrays/default.htm)

Electron Gamma Shower (http://www2.slac.stanford.edu/vvc/egs/Default.htm)

Have fun! :smile: :cool:

Hey, Marlon - you were looking for physics opportunities in California. Well - here is one, but it is a bit of drive down to Hollywood!

[Astronuc]

Some short articles on particle physics from American Institute of Physics - Physics News - http://newton.ex.ac.uk/aip/catagories/particle_physics.html

[Astronuc]

I search for this but I didn't find it in this thread.

Summary Tables
in the 2002 Review of Particle Physics

http://pdg.lbl.gov/2002/contents_tables.html

[Astronuc]

News from the particle physics world -

http://www.interactions.org/cms/

[marlon]

Check THIS SITE (http://nobelprize.org/physics/laureates/2004/index.html) if you wanna find out more on the concept of asymptotic freedom in QCD. You need to click on "Nobel Lectures" to read what the 2004 Nobel Laureates in Physics have to say on it.

PS : Did you guys know that the guy in the middle actually played in a movie (http://en.wikipedia.org/wiki/David_Politzer)with Paul Newman ?

regards
marlon

[marlon]

If you wanna have a very introductory lesson (http://nobelprize.org/physics/laureates/1999/index.html) in renormalization theory of the weak interaction, just read the Nobel Lecture of Gerardus 't Hooft, the 1999 Physics Nobel Prize Laureate.

Enjoy


regards
marlon

[Astronuc]

Deutsche Physikalische Gesellschaft e.V.
http://www.dpg-physik.de/

http://www.dpg-tagungen.de/index.html - auf Deutsch

http://www.dpg-tagungen.de/index_en.html - English

ein Beispiel / example -

http://www.dpg-tagungen.de/archive/2004/files/koeln_prog.pdf

[Astronuc]

WS 05/06 No. 6811
Ian C. Brock

http://www-zeus.physik.uni-bonn.de/~brock/teaching/vtp_ws0506/

[Astronuc]

This is really cool!

http://geant4.cern.ch/G4UsersDocuments/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html

[Astronuc]

Researchers report the first direct observation of the strange b baryon Xi_b^{-} or \Xi_b^{-}

http://www.arxiv.org/abs/0706.1690

p\bar{p} collisions at \sqrt{s} = 1.96 TeV.

For more publications related to the D0 experiment.
http://www.arxiv.org/find/hep-ex/1/au:+Collaboration_D0/0/1/0/all/0/1

[humanino]

Hi everyone,

I was earlier today searching for online video material for students who asked me where to find it. I admit that such lectures are much more pleasant to follow than textbooks, although I myself never find the need for video material. The best would be to actually be able to attend the lecture interactively. In any case, it did not occur to me at first, but CERN as an amazing server full of countless presentations on all sorts of topics. Soome of them of incredible value.

You will find them by browsing their web server (http://webcast.cern.ch/). Enjoy :smile:

Praising thanks to this wonderful initiative.

[Astronuc]

Revealing the Hidden Nature of Space and Time:
Charting the Course for Elementary Particle Physics
http://www.nap.edu/catalog.php?record_id=11641

Principal Chapters:

1. The Scientific Excitement and Challenges 17-32
2. Key Questions in Particle Physics 33-55
3. The Experimental Opportunities 56-100
4. The Strategic Framework 101-117
5. Findings and Recommended Actions 118-135

As part of the Physics 2010 decadal survey project, the National Research Council was asked by the Department of Energy and the National Science Foundation to recommend priorities for the U.S. particle physics program for the next 15 years. The challenge faced in this study was to identify a compelling leadership role for the United States in elementary particle physics given the global nature of the field and the current lack of a long-term and distinguishing strategic focus. Revealing the Hidden Nature of Space and Time provides an assessment of the scientific challenges in particle physics, including the key questions and experimental opportunities, the current status of the U.S. program and the strategic framework in which it sits and a set of strategic principles and recommendations to sustain a competitive and globally relevant U.S. particle physics program.

[Astronuc]

Course notes on particle physics and standard model.

http://physics.uoregon.edu/~jimbrau/physics.html

Three part program on Elementary Particle Phenomenology:

Physics 661, Fall 2003 (http://physics.uoregon.edu/~jimbrau/ph661-2003/) -

Introduction to the particles, forces, and the observable universe
Cosmic Rays
Quarks and Leptons
Interactions and Fields
Invariance Principles and Conservation Laws
Quarks in Hadrons
Lepton and Quark Scattering

Physics 662, Winter 2004 (http://physics.uoregon.edu/~jimbrau/ph662-2004/) -

Quark Interactions and QCD
Weak Interactons
Cosmic Neutrinos
Electroweak Interactions and the Standard Model
Physics Beyond the Standard Model
Relativity and Cosmological Models

Physics 663, Spring 2004 (http://physics.uoregon.edu/~jimbrau/ph663-2004/) -

particle accelerator concepts
experimental particle physics detector techniques
search for gravitational radiation




From his course - Physics 610 - Collider Physics:

"The Standard Model in 2001,'' Jonathan Rosner
Lectures at the 55th Scottish Universities' Summer School in Physics, St. Andrews
http://arXiv.org/abs/hep-ph/0108195
particularly sections 1 through 2.2
.
"Introduction to Electroweak Symmetry Breaking,'' Sally Dawson
Lectures given at the 1998 Summer School in High Energy Physics and Cosmology, Trieste, Italy
http://xxx.lanl.gov/abs/hep-ph/9901280
.
"Beyond the Standard Model,'' Michael Peskin
Lectures presented at the 1996 European School of High-Energy Physics
http://xxx.lanl.gov/abs/hep-ph/9705479

[Astronuc]

Some historical background on HEP.


The discovery of the tau lepton: Part 1, The early history through 1975; Part 2, Confirmation of the discovery and measurement of major properties, 1976--1982; Perl, M. L.; February 01, 2000; SLAC-PUB--6584; ACC0025
http://www.osti.gov/accomplishments/documents/fullText/ACC0025.pdf


Discovery of charm; Goldhaber, G.; November 29, 1999; LBL--18696; ACC0023
http://www.osti.gov/accomplishments/documents/fullText/ACC0023.pdf


The hydrogen bubble chamber and the strange resonances; Alvarez, L.W.; November 29, 1999; LBL--22392; ACC0021
http://www.osti.gov/accomplishments/documents/fullText/ACC0021.pdf


The discovery of the top quark; Sinervo, P.K.; November 19, 1999; FNAL/C--95/371-E; ACC0015
http://www.osti.gov/accomplishments/documents/fullText/ACC0015.pdf


The discovery of the b quark at Fermilab in 1977: The experiment coordinator's story; Yoh, J.; October 26, 1999; FNAL/C--97/432-E; ACC0013
http://www.osti.gov/accomplishments/documents/fullText/ACC0013.pdf


Delta: the first pion nucleon resonance - its discovery and applications; Nagle, D.; October 26, 1999; LALP--84-27; ACC0011
http://www.osti.gov/accomplishments/documents/fullText/ACC0011.pdf


The ultimate structure of matter: The high energy physics program from the 1950s through the 1980s; ; January 19, 1999; DOE/ER--0435; ACC0005
http://www.osti.gov/accomplishments/documents/fullText/ACC0005.pdf


More at - http://www.osti.gov/accomplishments/databasebrowse.html

[Astronuc]

I stumbled across this huge resource while looking for information on CMB and CMB-frame. These are all in downloadable PDF format.

http://pdg.lbl.gov/2008/reviews/contents_sports.html

Categories:

Constants, Units, Atomic and Nuclear Properties
Physical constants (Rev.)
Astrophysical constants and parameters (Rev.)
International System of units (SI)
Periodic table of the elements (Rev.)
Electronic structure of the elements
Atomic and nuclear properties of materials (Rev.) PDF / Interactive
Electromagnetic relations
Naming scheme for hadrons



Standard Model and Related Topics

Quantum chromodynamics
Electroweak model and constraints on new physics (Rev.)
Cabibbo-Kobayashi-Maskawa quark-mixing matrix (Rev.)
CP violation (Rev.)
Neutrino mass, mixing, and flavor change (Rev.)
Quark model (Rev.)
Grand Unified Theories
Structure Functions (Rev.; see below for more figures)
Structure Functions--additional figures (Rev.; see above)
Fragmentation functions in e+e- annihilation and lepton-nucleon DIS (Rev.)
Tests of Conservation Laws
CPT Invariance Tests in Neutral Kaon Decay (New)
CP Violation in KS -> 3pi
CP Violation in KL Decays (Rev.)
V(ud), V(us), Cabibbo Angle, and CKM Unitarity (Rev.)
Determination of V(cb) and V(ub) (Rev.)



Particle Properties (Hypothetical particles are listed below.)

Gauge Bosons
The Mass of the W Boson (Rev.)
Triple Gauge Couplings
Anomalous W/Z Quartic Couplings
The Z Boson (Rev.)
Anomalous Z Z gamma,
Z gamma gamma, and Z Z V Neutral Couplings


- Charged Leptons
Muon Anomalous Magnetic Moment (Rev.)
Muon Decay Parameters (Rev.)
tau Branching Fractions (Rev.)
tau-Lepton Decay Parameters (Rev.)

- Neutrinos
Number of Light Neutrino Types (Rev.)
Neutrinoless Double-beta Decay (Rev.)
Solar Neutrinos Review (Rev.)

- Quarks
Quark Masses (Rev.)
The Top Quark (Rev.)

- Mesons
Note on Scalar mesons (Rev.)
The eta(1405), eta(1475), f_1(1420), and f_1(1510) (Rev.)
Rare Kaon Decays (Rev.)
K(l3)+- and K(l3)0 Form Factors (Rev.)
CPT Invariance Tests in Neutral Kaon Decay (New)
CP-Violation in KS -> 3pi
V(ud), V(us), Cabibbo Angle, and CKM Unitarity (New)
CP-Violation in KL Decays (Rev.)
Dalitz-Plot Analysis Formalism
Review of Charm Dalitz-Plot Analyses (Rev.)
D0-- Dbar0 Mixing (Rev.)
Decay Constant of Charged Pseudoscalar Mesons (new)
Production and Decay of b-flavored Hadrons (Rev.)
Polarization in B Decays (Rev.)
B0-- Bbar0 Mixing (Rev.)
Determination of V(cb) and V(ub) (Rev.)
Branching Ratios of psi(2S) and chi_c(0,1,2) (Rev.)

- Baryons
Baryon Decay Parameters
N and Delta Resonances
Pentaquarks (New)
Radiative Hyperon Decays
Charmed Baryons (Rev.)
Lambda(c)+ Branching Fractions

- Hypothetical Particles and Concepts
Searches for Higgs Bosons (Rev.)
Free Quark Searches
Magnetic Monopole Searches
Supersymmmetry: Theory (Rev.)
Supersymmmetry: Experiment (Rev.)
Dynamical Electroweak Symmetry Breaking (Rev.)
Searches for Quark and Lepton Compositeness
Extra Dimensions (Rev.)
Axions and Other Very Light Bosons (New)
The W' Searches (Rev.)
The Z' Searches (Rev.)
The Leptoquark Quantum Numbers (New)


Astrophysics and Cosmology

Experimental tests of gravitational theory (Rev.)
Big-Bang cosmology (Rev.)
Big-Bang nucleosynthesis (Rev.)
Cosmological parameters (Rev.)
Dark matter (Rev.)
Cosmic microwave background (Rev.)
Cosmic rays (Rev.)



Experimental Methods and Colliders

Accelerator physics of colliders
High-energy collider parameters (Rev.)
Passage of particles through matter (Rev.)


Particle detectors (Rev.)

Radioactivity and radiation protection (Rev.)
Commonly used radioactive sources


and related - http://pdg.lbl.gov/2008/AtomicNuclearProperties/index.html - but I don't know where to put it at the moment.


Mathematical Tools

Probability (Rev.)
Statistics (Rev.)
Monte Carlo techniques (Rev.)
Monte Carlo particle numbering scheme (Rev.)
Clebsch-Gordan coeff., sph. harmonics, and d functions
SU(3) isoscalar factors and representation matrices
SU(n) multiplets and Young diagrams



Kinematics, Cross-Section Formulae, and Plots

Kinematics (Rev.)
Cross-section formulae for specific processes (Rev.)
Plots of cross sections and related quantities (Rev.) PDF / Interactive



Authors, Introductory Text, History plots

[Narayanan.S]

Hi everyone...

I have answered already a lot of questions here on the topic of the different elementary particles in the Standard Model. For this reason I will give the interested reader this site that describes this subject very clearly...

http://pdg.web.cern.ch/pdg/particleadventure/frameless/startstandard.html

If you have more questions, please don't hesitate to post them here...

regards
marlon :biggrin: :cool:

Hi
marlon
I have a very fundamental question please help me
Are electrons really close to structure less point charged particles?
Since I am not getting convinced from theory, is it the experiments that makes us believe so,then why is its size being revised year after year.
Are we missing something very fundamental?
Regards
Shankar

[malawi_glenn]

Hi
marlon
I have a very fundamental question please help me
Are electrons really close to structure less point charged particles?
Since I am not getting convinced from theory, is it the experiments that makes us believe so,then why is its size being revised year after year.
Are we missing something very fundamental?
Regards
Shankar

We have so far no experimental signs of size or structure of the electron; experimentally we can only deduce the UPPER LIMIT - and that limit changes as we reach higher and higher energies in our laboratories.

The upper limit of the electron radius is 10^-21 meters I think, thus we have not said that "the size of the electron IS 10^-21 meters", we have only said "IF the electron has size, then it is smaller than 10^-21meters".