In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles mediate the weak interaction; the respective symbols are W+, W−, and Z0. The W± bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles. The Z0 boson is electrically neutral and is its own antiparticle. The three particles have a spin of 1. The W± bosons have a magnetic moment, but the Z0 has none. All three of these particles are very short-lived, with a half-life of about 3×10−25 s. Their experimental discovery was pivotal in establishing what is now called the Standard Model of particle physics.
The W bosons are named after the weak force. The physicist Steven Weinberg named the additional particle the "Z particle", and later gave the explanation that it was the last additional particle needed by the model. The W bosons had already been named, and the Z bosons were named for having zero electric charge.The two W bosons are verified mediators of neutrino absorption and emission. During these processes, the W± boson charge induces electron or positron emission or absorption, thus causing nuclear transmutation.
The Z boson mediates the transfer of momentum, spin and energy when neutrinos scatter elastically from matter (a process which conserves charge). Such behavior is almost as common as inelastic neutrino interactions and may be observed in bubble chambers upon irradiation with neutrino beams. The Z boson is not involved in the absorption or emission of electrons or positrons. Whenever an electron is observed as a new free particle, suddenly moving with kinetic energy, it is inferred to be a result of a neutrino interacting directly with the electron, since this behavior happens more often when the neutrino beam is present. In this process, the neutrino simply strikes the electron and then scatters away from it, transferring some of the neutrino's momentum to the electron.
If I look at the photon propagator <A_mu (x) A^nu(0) > in momentum space, as I understand it I am to compute this by summing up all the self-energy diagrams of the photon, which look like:
photon -> stuff -> photon
In particular, since the photon shares the same quantum numbers as the Z, you...
I am a student minor in physics and I am taking this course of particle physics. And I have been lost since the Non-Abelian Gauge Theory which a few lectures before Electroweak unified Theory lecture.
i am completely confused and overwhelmed by the math since the mid-term exam, since I was not...
Hi All
1. Homework Statement
with the known coupling strenght between SM neutrinos and Z boson
Z_{\mu} \bar{\nu}_{L} { \gamma}^{ \mu} \nu_{L}
how can I get the coupling strength for Dirac neutrinos
Z_{\mu} \bar{\nu}_{Dirac} { \gamma}^{ \mu} (1- { \gamma}_{ 5} ) \nu_{Dirac} ?
thanks
Homework Statement
Calculate the ratio ##R = \frac{\sigma_{had}}{\sigma_{\mu+\mu-}}## for energy around ##10~GeV##.
At sufficiently high energies, the ##e^+e^- \rightarrow \mu^+ \mu^-## reaction can proceed via the ##Z^0## boson. Assuming vertex factors for EM and weak interaction are the same...
Hi there, my question is the following.
If an electron and positron annihilate, how can they result in ZZ?
The issue I'm having is that due to charge conservation, the exchange particle can't be W- or W+.
It also can't be a photon since the Z's don't have electrical charge to couple to.
It...
The Standard Model formula for the cross-section of ##e^+e^-\rightarrow\mu^+\mu^-## is made up of 3 components: QED interactions, weak interactions, and electroweak interference. I understand the behaviour of the QED part, and the resonance that occurs in the weak part at ##\sqrt{s}=M_Z##, but...
I've seen explanations that when a neutrino with a W+ Boson comes near a neutron, it affects one of the bottom quarks and changes it to a up quark which effectively turns the neutron into a proton. The neutrino then turns into an electron.
Source:
(2:20 onwards)
I've seen other explanations...
I have read that the Z boson cannot change the flavour of a particle. So my assumption is that an interaction such as:
usanti -> udanti + Z
Is not possible, is this correct?
Hi all,
I have a question about simulating (Monte Carlo) proton-proton collisions resulting in, for example, a Z boson. Assume two quarks (quark and antiquark) from each proton collide head-on along the z-axis. The quark momenta are distributed according to the Parton Density Functions...
Hello everyone,
I have read about the theoretical values of the Z boson decay partial width and how well they agreed with experiment. However there is something I do not quite understand: since these theoretical calculations were performed with the hypothesis that the masses of the decay...
Could someone please tell me what the symbols in the Zee.csv file mean on the CERN webpage (https://cms-docdb.cern.ch/cgi-bin/PublicDocDB/ShowDocument?docid=11581)? I am doing a project for my statistics class and that information would be useful. I'll appreciate any and all help.
Why does the Z boson only decay to fermion-antifermion pairs? I'd just like to understand the basic reason why something like Z --> anti-down, strange wouldn't work. This would conserve charge. It obviously wouldn't conserve strangeness, but the weak interaction doesn't, so I'm just wondering...
Homework Statement
One of the mediators of the weak interactions is the Z boson, which has a mass of 91 GeV/c
2.
Use this information to find an approximate value for the range of the weak interaction.
Homework Equations
This is the part that I am having trouble with. I don't know where to...
I was always wondering, on very short distances/high energies, what is a net effect of having not one (gamma) but two (gamma and Z) 'carriers' for the 'force' between 2 charged particles. Does it make an interaction sronger or not?
Can someone give me a qualitative/handwaving argument of
why much more W^+/- boson are produced in proton-antiproton
collisions compared to Z^0 bosons?
PDFs are not enough to explain this I believe, since we will have more
u ubar pairs in the collision than u dbar...
Also if I...
Suppose I want to find the minimum velocity of the electron and positron required to make a Z boson during annihilation. How would I go about this? I had an attempt which came out at 422ms^-1. This doesn't really seem right... so I'm guessing i made a big mistake...
Question leads on from others where s^1/2 = 200GeV mH = 70GeV EH = 91.5GeV and p = 59GeV, (three momentum).
The reaction was e+e- -> HZ0
where H is higgs boson and Z0 is the Z0 boson with mass 91GeV
It says the Z0 decays to two muon and antimuon. They are observed to be equal energy in...
I need help understanding the Higgs mechanism: what is the Higgs condensate, what is the Higgs boson, why do only the W and Z bosons have mass, and how exactly do particles receive mass? thanks guys!
Hi!
I was wondering how W+/- pairs can be created in an electron/positron collider.
Does the e+e- form a Z^0 which decays to W^- W^+ ?
http://www.particle.kth.se/zlab/project/Elep.gif
I have found this picture, but there is no info about the mediating particle (in the small...