View Full Version : Higgs Particles
Hatim Hegab
Apr29-04, 05:38 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Hi,\nCan someone here give me a good idea about Higgs theory?, or provide me with\nsome sites that can help?\n\nhhegab\n\n\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hi,
Can someone here give me a good idea about Higgs theory?, or provide me with
some sites that can help?
hhegab
Doug Sweetser
Apr30-04, 10:34 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Hello Hatim:\n\nIt is usually called the Higgs mechanism. The standard model Lagrange\ndensity has U(1), SU(2), and SU(3) symmetry in order to explain the zoo\nof particles we have seen in Nature. All the particles are _massless_,\nwhich is not what is seen in Nature :-) The Higgs mechanism preserves\nthe symmetry of the Lagrange density. For the vacuum state however,\nthe ground state involves spontaneous symmetry breaking, the proverbial\nMexican hat trick. This broken symmetry gives all the particles mass\nvia a scalar field.\n\nThat is about all I know about it.\ndoug\nquaternions.com\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hello Hatim:
It is usually called the Higgs mechanism. The standard model Lagrange
density has U(1), SU(2), and SU(3) symmetry in order to explain the zoo
of particles we have seen in Nature. All the particles are _massless_,
which is not what is seen in Nature :-) The Higgs mechanism preserves
the symmetry of the Lagrange density. For the vacuum state however,
the ground state involves spontaneous symmetry breaking, the proverbial
Mexican hat trick. This broken symmetry gives all the particles mass
via a scalar field.
That is about all I know about it.
doug
quaternions.com
Hendrik van Hees
May3-04, 05:34 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Doug Sweetser wrote:\n\n> Hello Hatim:\n>\n> It is usually called the Higgs mechanism. The standard model Lagrange\n> density has U(1), SU(2), and SU(3) symmetry in order to explain the\n> zoo\n> of particles we have seen in Nature. All the particles are\n> _massless_,\n> which is not what is seen in Nature :-) The Higgs mechanism preserves\n> the symmetry of the Lagrange density. For the vacuum state however,\n> the ground state involves spontaneous symmetry breaking, the\n> proverbial\n> Mexican hat trick. This broken symmetry gives all the particles mass\n> via a scalar field.\n\nOne should not put it in this form. The Higgs mechanism is not the only\nmechanism in nature, "creating" mass. It creates mass for the gauge\nbosons of the weak interaction, the W und Z-bosons (and via the Yukawa\ncouplings also to the elementary particles, i.e., the quarks and\nleptons) in a way such that the mathematical structure (gauge\ninvariance) of the fieldtheory describing electromagnetic and weak\ninteractions is not destroyed by the fact that the gauge bosons have\nmass.\n\nThe matter, surrounding us every day, is in fact "made of" the two\nlightest quarks, the u and the d quarks (and their antiparticles) and\nelectrons.\n\nThis light quarks are relatively light particles with a mass around some\nMeV (compared to the nucleon with mass 939MeV).\n\nThe main mechanism of mass creation is the breaking of conformal\nsymmetry of massless QCD, leading to the socalled trace anomaly. Here\n"trace" is meant as the sum of the diagonal elements of the\nenergy-momentum tensor. In the classical massless gauge theory, there\nis no dimensionful parameter (here I mean dimension of length or mass)\nand so the theory is invariant under rescaling of space and time. This\nsymmetry yields to the vanishing of the trace of the energy-momentum\ntensor, which reflects the masslessness of the particles, described by\nthe fields.\n\nNow we have not a classical non-abelian Yang-Mills theory to describe\nthe strong interactions, but a quantum theory, namely the quantized\nversion of this non-abelian gauge symmetry, therefore known as QCD\n(Quantum (!) Chromo Dynamics).\n\nQuantising the field theory inevitably destroys the dilatation symmetry.\nMost easily one recognises this when it comes to the issue of\nrenormalisation in perturbative QCD: There is no way to renormalise\nthis theory without introducing a dimensionful parameter, which tells\nus at which momentum scale the various divergent quantities are to be\nsubtracted to get finite and physically meaningful results. The theory\nbecomes dependent on this momentum scale. The physical finite coupling\nconstant becomes thus a function of this momentum scale, and the\nquantised theory can never be invariant under space-time rescalings.\nThe trace of the energy-momentum tensor is thus no longer 0, and the\nparticles acquire mass through the strong interaction.\n\nThus, the masses of the three quarks, making the protons and neutrons\nthe matter surrounding us is made of (and in fact carrying the main\nfraction of the mass, we measure for this matter) are rather tiny\ncompared to the mass of the protons and neutrons, which so are\nidentified as a pure quantum effect, namely the trace anomaly!\n\nDue to the problem that the strong interaction is strong at low momentum\nscales (known as asymptotic freedom), leading to the quark confinement,\nwhich means that we\'ll never be able to find free quarks, but only\nthose bound to hadrons (mesons and baryons like the pion and the\nnucleons), we do not know very precisely how those masses come about.\nUp to now, the only way out of this trouble, which comes from the fact\nthat the usually applied perturbation theory doesn\'t work for strongly\ninteracting particles, is sheer computer power, applied to a\ndiscretized version of QCD as an approximation to "real-world" QCD.\nInstead of the continuous space-time one considers a lattice version of\nspace time.\n\nIt is an art of its own to make this approximations work on rather small\nspace-time lattices, because the numerical effort to calculate physical\nquantitities from this lattice gauge theories is so immense that with\nthe computing power of today\'s computers, the lattice gauge\ntheoreticians can only use rather small lattices, but nevertheless this\napproach to solve QCD was and is a great success. The masses of the\nknown hadrons can be determined at an accuracy of some percent, which\nis very good in view of the immense difficulty in solving the highly\nnon-linear equations, defining QCD.\n\nA nice review, readable for the public (or at least physicists, which\nare not lattice experts) on this subject can be found in one of the\nlast issues of Physics Today (or another article of this type for\nGerman readers in the May issue of the Physik Journal).\n\n--\nHendrik van Hees Cyclotron Institute\nPhone: +1 979/845-1411 Texas A&M University\nFax: +1 979/845-1899 Cyclotron Institute, MS-3366\nhttp://theory.gsi.de/~vanhees/ College Station, TX 77843-3366\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Doug Sweetser wrote:
> Hello Hatim:
>
> It is usually called the Higgs mechanism. The standard model Lagrange
> density has U(1), SU(2), and SU(3) symmetry in order to explain the
> zoo
> of particles we have seen in Nature. All the particles are
> _massless_,
> which is not what is seen in Nature :-) The Higgs mechanism preserves
> the symmetry of the Lagrange density. For the vacuum state however,
> the ground state involves spontaneous symmetry breaking, the
> proverbial
> Mexican hat trick. This broken symmetry gives all the particles mass
> via a scalar field.
One should not put it in this form. The Higgs mechanism is not the only
mechanism in nature, "creating" mass. It creates mass for the gauge
bosons of the weak interaction, the W und Z-bosons (and via the Yukawa
couplings also to the elementary particles, i.e., the quarks and
leptons) in a way such that the mathematical structure (gauge
invariance) of the fieldtheory describing electromagnetic and weak
interactions is not destroyed by the fact that the gauge bosons have
mass.
The matter, surrounding us every day, is in fact "made of" the two
lightest quarks, the u and the d quarks (and their antiparticles) and
electrons.
This light quarks are relatively light particles with a mass around some
MeV (compared to the nucleon with mass 939MeV).
The main mechanism of mass creation is the breaking of conformal
symmetry of massless QCD, leading to the socalled trace anomaly. Here
"trace" is meant as the sum of the diagonal elements of the
energy-momentum tensor. In the classical massless gauge theory, there
is no dimensionful parameter (here I mean dimension of length or mass)
and so the theory is invariant under rescaling of space and time. This
symmetry yields to the vanishing of the trace of the energy-momentum
tensor, which reflects the masslessness of the particles, described by
the fields.
Now we have not a classical non-abelian Yang-Mills theory to describe
the strong interactions, but a quantum theory, namely the quantized
version of this non-abelian gauge symmetry, therefore known as QCD
(Quantum (!) Chromo Dynamics).
Quantising the field theory inevitably destroys the dilatation symmetry.
Most easily one recognises this when it comes to the issue of
renormalisation in perturbative QCD: There is no way to renormalise
this theory without introducing a dimensionful parameter, which tells
us at which momentum scale the various divergent quantities are to be
subtracted to get finite and physically meaningful results. The theory
becomes dependent on this momentum scale. The physical finite coupling
constant becomes thus a function of this momentum scale, and the
quantised theory can never be invariant under space-time rescalings.
The trace of the energy-momentum tensor is thus no longer 0, and the
particles acquire mass through the strong interaction.
Thus, the masses of the three quarks, making the protons and neutrons
the matter surrounding us is made of (and in fact carrying the main
fraction of the mass, we measure for this matter) are rather tiny
compared to the mass of the protons and neutrons, which so are
identified as a pure quantum effect, namely the trace anomaly!
Due to the problem that the strong interaction is strong at low momentum
scales (known as asymptotic freedom), leading to the quark confinement,
which means that we'll never be able to find free quarks, but only
those bound to hadrons (mesons and baryons like the pion and the
nucleons), we do not know very precisely how those masses come about.
Up to now, the only way out of this trouble, which comes from the fact
that the usually applied perturbation theory doesn't work for strongly
interacting particles, is sheer computer power, applied to a
discretized version of QCD as an approximation to "real-world" QCD.
Instead of the continuous space-time one considers a lattice version of
space time.
It is an art of its own to make this approximations work on rather small
space-time lattices, because the numerical effort to calculate physical
quantitities from this lattice gauge theories is so immense that with
the computing power of today's computers, the lattice gauge
theoreticians can only use rather small lattices, but nevertheless this
approach to solve QCD was and is a great success. The masses of the
known hadrons can be determined at an accuracy of some percent, which
is very good in view of the immense difficulty in solving the highly
non-linear equations, defining QCD.
A nice review, readable for the public (or at least physicists, which
are not lattice experts) on this subject can be found in one of the
last issues of Physics Today (or another article of this type for
German readers in the May issue of the Physik Journal).
--
Hendrik van Hees Cyclotron Institute
Phone: +1 979/845-1411 Texas A&M University
Fax: +1 979/845-1899 Cyclotron Institute, MS-3366
http://theory.gsi.de/~vanhees/ College Station, TX 77843-3366
Esa A E Peuha
May6-04, 07:52 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nHendrik van Hees <hees@comp.tamu.edu> writes:\n\n> The main mechanism of mass creation is the breaking of conformal\n> symmetry of massless QCD, leading to the socalled trace anomaly.\n\nCould it be possible that the quarks and leptons get their masses by a\nsimilar mechanism? More precisely, since any internal structure that\nquarks and leptons must have very small distance scale, and therefore\nvery high energy scale, could it produce the relatively small masses\nthat quarks and leptons have?\n\n--\nEsa Peuha\nstudent of mathematics at the University of Helsinki\nhttp://www.helsinki.fi/~peuha/\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hendrik van Hees <hees@comp.tamu.edu> writes:
> The main mechanism of mass creation is the breaking of conformal
> symmetry of massless QCD, leading to the socalled trace anomaly.
Could it be possible that the quarks and leptons get their masses by a
similar mechanism? More precisely, since any internal structure that
quarks and leptons must have very small distance scale, and therefore
very high energy scale, could it produce the relatively small masses
that quarks and leptons have?
--
Esa Peuha
student of mathematics at the University of Helsinki
http://www.helsinki.fi/~peuha/
alistair
May7-04, 06:40 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>If there are a finite number of Higgs particles in the universe,\nwhen a particle moves faster and gains more mass, does it slightly reduce the\nmass of other particles by possessing more Higgs particles than it used to?\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>If there are a finite number of Higgs particles in the universe,
when a particle moves faster and gains more mass, does it slightly reduce the
mass of other particles by possessing more Higgs particles than it used to?
Hatim Hegab
May10-04, 05:02 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nHellow Peuha,\nThe top quark is the heaviest particle ever found...so I am not getting what\nyou said exactly.\n\nhhegab\n\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hellow Peuha,
The top quark is the heaviest particle ever found...so I am not getting what
you said exactly.
hhegab
Esa A E Peuha
May11-04, 07:04 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"Hatim Hegab" <hhegab@hotmail.com> writes:\n\n> The top quark is the heaviest particle ever found...so I am not getting what\n> you said exactly.\n\nYes, the top quark is extremely heavy, but other quarks (especially up\nand down) are light, and some leptons are even lighter - the neutrinos\nare very nearly massless. So is it possible that neutrinos could have\nany kind of internal structure and still fit the vanishingly small upper\nbounds of their masses?\n\n--\nEsa Peuha\nstudent of mathematics at the University of Helsinki\nhttp://www.helsinki.fi/~peuha/\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Hatim Hegab" <hhegab@hotmail.com> writes:
> The top quark is the heaviest particle ever found...so I am not getting what
> you said exactly.
Yes, the top quark is extremely heavy, but other quarks (especially up
and down) are light, and some leptons are even lighter - the neutrinos
are very nearly massless. So is it possible that neutrinos could have
any kind of internal structure and still fit the vanishingly small upper
bounds of their masses?
--
Esa Peuha
student of mathematics at the University of Helsinki
http://www.helsinki.fi/~peuha/
Thomas Dent
May14-04, 04:05 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Esa A E Peuha <esa.peuha@helsinki.fi> wrote in message news:<86p4qqvjjon.fsf@sirppi.helsinki.fi>...\n> Hendrik van Hees <hees@comp.tamu.edu> writes:\n>\n> > The main mechanism of mass creation is the breaking of conformal\n> > symmetry of massless QCD, leading to the socalled trace anomaly.\n>\n> Could it be possible that the quarks and leptons get their masses by a\n> similar mechanism? More precisely, since any internal structure that\n> quarks and leptons must have very small distance scale, and therefore\n> very high energy scale, could it produce the relatively small masses\n> that quarks and leptons have?\n\nIt\'s been tried, "compositeness" or "preons"... but it\'s very\ndifficult to make it work properly. The family/generation structure\nand radiative corrections to electroweak parameters are a big\nchallenge for this sort of approach.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Esa A E Peuha <esa.peuha@helsinki.fi> wrote in message news:<86p4qqvjjon.fsf@sirppi.helsinki.fi>...
> Hendrik van Hees <hees@comp.tamu.edu> writes:
>
> > The main mechanism of mass creation is the breaking of conformal
> > symmetry of massless QCD, leading to the socalled trace anomaly.
>
> Could it be possible that the quarks and leptons get their masses by a
> similar mechanism? More precisely, since any internal structure that
> quarks and leptons must have very small distance scale, and therefore
> very high energy scale, could it produce the relatively small masses
> that quarks and leptons have?
It's been tried, "compositeness" or "preons"... but it's very
difficult to make it work properly. The family/generation structure
and radiative corrections to electroweak parameters are a big
challenge for this sort of approach.
Hatim Hegab
May14-04, 04:11 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>The idea of having a yet smaller internal structure is not nice, we just\ndelay the problem to another time. I mean, we shall have to study those\nconstituents and then propose that they will also have an internal\nstructure...!\nI am kindda lost here, isn\'t supersymmetry supposed to solve this?\n\nHatim\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>The idea of having a yet smaller internal structure is not nice, we just
delay the problem to another time. I mean, we shall have to study those
constituents and then propose that they will also have an internal
structure...!
I am kindda lost here, isn't supersymmetry supposed to solve this?
Hatim
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