Tagged Questions
8
votes
0answers
57 views
Does the existence of Higgs imply the existence of Magnetic Monopoles?
I am aware that in theories with spontaneous symmetry breaking, Magnetic Monopoles can exist as topological solitons. Can the same be done with the Standard Model gauge group. I am familiar with the ...
3
votes
0answers
49 views
List of cross sections?
Sometimes I need to look up a certain cross section, say the inclusive Z production cross section at $\sqrt{s}$ = 7 TeV. Is there a place where 'all the' cross sections are tabulated ...
9
votes
0answers
89 views
infrared free QED and Higgsless standard model phenomenology
This is one of those "what if" fantasy world type questions. I like hard sci-fi so please no "well, you changed one thing about the world so now anything goes." :)
What if the Higgs had no vev?
That ...
4
votes
2answers
240 views
What is the Standard Model equation which unified Strong, Weak, and Electromagnetism?
I always heard that three atomic force in small scale structure (Strong, weak and electromagnetic) are unified through the standard model, but I've never seen its unified equation. What is single ...
1
vote
0answers
92 views
Mirror Matter Hypothesis?
What is the current state of the hypothesis of mirror matter today?
Are there any experimental data or theoretical arguments that exclude it by now, or is it still considered viable among physicists?
...
3
votes
1answer
146 views
Origin of electric charge
Baryons have charges that are the result of a polynomial calculation of their building blocks (quarks)'s fractional charges. But what gives these quarks electric charges? What interactions do they ...
5
votes
2answers
116 views
Why is there a linear relationship between charge and isospin?
So the title basically says it all. Something that's really bothering me is the fact that the Gell-Mann Nishijima relationship can be extended to provide a linear relationship between charge and all ...
3
votes
3answers
73 views
Trilinear gauge couplings: Spin
In non-abelian gauge theories self interaction of gauge fields is permitted, allowing coupling such as $WWZ$ (i.e. $Z$-boson decaying to $W^+W^-$) or ggg (i.e. gluon splitting into two new gluons).
...
0
votes
0answers
62 views
Pareto efficiency and Standard Model parameters
Pareto Efficiency is a well understood concept in economics, which basically is a condition where no one actor could be made better off without some one being made worse off. This condition allows ...
2
votes
0answers
114 views
Do all the particles acquire mass in the Standard Model due to the Higgs mechanism only?
I know that a mass term for an intermediate boson is not compatible with the gauge symmetry. But in principle a mass term for the electron field does not violate a gauge symmetry. However to build an ...
0
votes
0answers
17 views
Hamiltonian of the charged current in SM (related to the lorentz invariance)
recently when I was studying the scatterings which involves a vector boson (like W boson) as an intermediate particle, I saw that the propagator is not Lorentz invariant, I read that there is another ...
6
votes
3answers
191 views
Origin of lepton/quark generations?
What theoretical explanations exist for the fact that there are three generations of leptons and quarks?
I'm not so much asking why there are exactly 3 generations, but rather what makes electron, ...
2
votes
2answers
109 views
What is difference between the different 'flavours' of neutrinos?
Moreover, how-come scientist know that muon-neutrino are different from electron-neutrino when they didn't even know what the difference was? Did they interact differently with other particles?
4
votes
2answers
224 views
About free quarks and confinement
I simply know that a single free quark does not exist. What is the reason that we can not get a free quark?
If we can't get a free quark then what is single-top-quark?
5
votes
2answers
97 views
What maintains quark spin alignments in baryons?
What maintains quark spin alignments in baryons?
The $uud$ proton and $udd$ neutron are both spin 1/2, implying that two of their spin 1/2 quarks are always parallel and the other is always opposed.
...
3
votes
1answer
223 views
Higgs boson in LHC
Recently,the higgs bosons are discovered in LHC. My question is
How did they come to know that the particle that are created are actually Higgs boson?
On the basis of which properties,they ...
2
votes
1answer
113 views
How exactly are the different motions of only one kind of fundamental string assumed to give rise to the spectrum of elementary particles we observe?
In string theory, it is assumed that all particles can be described as quanta corresponding to the excitations of only one kind of fundamental string.
How can in principle the different motion ...
10
votes
1answer
293 views
What does the latest $B_s^0\rightarrow \mu^+\mu^-$ results mean for SUSY?
A paper from the LHCb collaboration just came out last week, stating basically that the $B_s^0\rightarrow\mu^+\mu^-$ decay matches standard model predictions, and people are already shouting that SUSY ...
6
votes
1answer
187 views
Weinberg angle measurement methods
I was reading up on the history of $W/Z$ bosons today and I got a little puzzled. I always assumed that people measured $M_Z$ and $M_W$ and then derived the Weinberg angle. But it appears that they ...
5
votes
2answers
251 views
Was the Higgs mass correctly predicted by asymptotic safety of gravity?
This paper was published in Phys Lett B in 2009, and predicted the Higgs mass to be 126 GeV based on the asymptotic safety of gravity. Is this prediction taken seriously by the theory community, or is ...
7
votes
1answer
110 views
Is the LEP B meson asymmetry evidence for higher dimensions and/or string theory?
According to this blog, new standard model calculations have changed the 3 sigma B meson forward and backward production asymmetry observed at LEP into two anomolies:
A 2.5 sigma B meson production ...
2
votes
2answers
198 views
Fermion Field of Standard Model
Why fermion field is treated as anti-commuting and boson field as truly classical in standard model?
3
votes
1answer
98 views
Weak isospin confinement?
According to the Wikipedia article on color confinement:
The current theory is that confinement is due to the force-carrying gluons having color charge [...],
i.e. because the gauge group is ...
1
vote
2answers
251 views
Quark compositions in $\pi^+$ to $\pi^0$ pion decay
Pions can undergo a rare beta-like decay into leptons:
Pion beta decay (with probability of about $10^{−8}$) into a neutral
pion plus an electron and electron antineutrino (or for positive
...
5
votes
3answers
224 views
Higgs Boson: The Big Picture
First, please pardon the ignorance behind this question. I know a fair amount of math but almost no physics.
I'm hoping someone can give me a brief "big picture" explanation of how physicists were ...
3
votes
3answers
240 views
If the electron is point like, then what is the significance of the classical radius of the electron?
What is the physical meaning/significance of the classical radius of the electron if we know from experiments that the electron is point like?
Is there similarly a classical radius of the photon? The ...
6
votes
3answers
418 views
How are the masses of unstable elementary particles measured?
I am interested in knowing how (Q1) the particle's masses are experimentally determined from accelerator observations.
What kind of particles? They must be as far as we know elementary and unstable ...
0
votes
0answers
95 views
What would the universe be like if Electroweak symmetry were unbroken? [duplicate]
Possible Duplicate:
What happens to matter in a standard model with zero Higgs VEV?
What if the Higgs did not have a "Mexican hat" potential and the therefore it's vacuum expectation value ...
4
votes
0answers
111 views
Relation among anomaly, unitarity bound and renormalizability
There is something I'm not sure about that has come up in a comment to other question:
Why do we not have spin greater than 2?
It's a good question--- the violation of renormalizability is linked
...
1
vote
1answer
118 views
Lepton masses in the Standard Model
Some simple questions regarding leptonic masses in the Standard Model (SM):
Why there is not an explicit mass term in addition to the effective mass term that arises from the Yukawa terms after ...
2
votes
2answers
98 views
Charges of quarks and leptons
Are there any theoretical restrictions within the framework of QFT that fix the relative sign between charged leptons and up-type quarks?
We know that in our universe, they have opposite signs -- ...
3
votes
0answers
271 views
On the naturalness problem
I know that there are several questions about the naturalness (or hierarchy or fine-tunning) problem of scalars masses in physics.stackexcange.com, but I have not found answers to any of the following ...
5
votes
2answers
228 views
How does Annihilation work?
I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different charges? Then what about ...
4
votes
2answers
179 views
What has been measured at the Higgs experiment and what do we know now?
Explained at the level of a 5$^{\text {th}}$ semester physics student (i.e. pre QFT, but far beyond the level of a news article for non-physicists, which avoids all details and only deals in ...
1
vote
1answer
170 views
Why not accurate masses of elementary particles?
In the standard model of particle accuracy in calculating mass is very low.
And you can not predict the upper limit of Higgs particle mass accurately. Why not accurate masses of elementary particles?
3
votes
1answer
177 views
Lepton Number Conservation
What is the global symmetry of the electroweak Lagrangian that gives rise to lepton number conservation?
As I understand it, electric charge is some linear combination of the conserved quantities ...
1
vote
1answer
359 views
Origin of the Higgs field
Are there any attempts in the literature at addressing the origin of the Higgs field? And, which lines of research that find it inevitable to address this question?
1
vote
1answer
130 views
Particle mixing and indistinguishability
Neutral kaons have two flavor combinations: $\mathrm{d}\bar{\mathrm{s}}$ and $\mathrm{s}\bar{\mathrm{d}}$. They can also be weak eigenstates: $\mathrm{\frac{d\bar{s} \pm s\bar{d}}{\sqrt{2}}}$.
But ...
3
votes
1answer
420 views
Introduction to Physical Content from Adjoint Representations
In particle Physics it's usual to write the physical content of a Theory in adjoint representations of the Gauge group. For example:
$24\rightarrow (8,1)_0\oplus (1,3)_0\oplus (1,1)_0\oplus ...
1
vote
0answers
99 views
What are the prerequisites to study CP violation?
If one would like to study CP violation, what would be the prerequisites for it?
For example, until now I have not studied quantum field theory and have done very little classical field theory, but ...
5
votes
1answer
256 views
How do physicists know that mass of possible Higgs particle is limited between two values?
How do physicists know that mass of possible Higgs particle is limited between two values 90 GeV/c$^2$ and 145 GeV/c$^2$?
0
votes
1answer
133 views
“Conceptualizing” neutrinos
Layman here. EE and BS physics. I am "content" in viewing photons/electromagnetic radiation as an "emergent" property of spacetime? due to the electrons ("particles..?") and all their activity jumping ...
2
votes
0answers
58 views
How can one activate the decay of the quark b with PYTHIA event generator?
This is my problem and I hope finding a solution.
_In the simplest alternative, MSTJ(22) = 2, the comparison is based on the average lifetime, or rather (c*tau "time life") , measured in mm. Thus ...
7
votes
2answers
1k views
Why is the Higgs boson spin 0?
Why is the Higgs boson spin 0? Detailed equation-form answers would be great, but if possible, some explanation of the original logic behind this feature of the Higgs mechanism (e.g., "to provide ...
6
votes
2answers
209 views
Is there an explanation for the 3:2:1 ratio between the electron, up and down quark electric charges?
I understand that the NNG formula relates $Q$, $I_3$, and $Y$ and can be derived in QCD; does this unambiguously predict the electric charge ratios without making assumptions about the definitions of ...
0
votes
1answer
248 views
What really is the future about the Standard Model
The fact that the bosons of the weak force have mass is something that I think technically poses many problems.
To avoid this and other problems with the masses of the particles devised a mechanism ...
3
votes
3answers
431 views
Building the meson octet and singlet
I am very lost in this topic. I understand that there are $3\times 3$ possible combinations of a quark and an anti-quark, but why should one decide arbitrarily (that's how it appears to me) that one ...
2
votes
1answer
185 views
In SUSY why does electroweak symmetry breaking only happen in the SM sector?
This is a difficult question to phrase succinctly, so I hope the title makes sense. What I want to understand is what seems like a lack of symmetry (besides SUSY-breaking) between the SM sector and ...
3
votes
3answers
148 views
What barriers exist to prevent us from turning a baryon into a anti-baryon?
At present the only way we can produce anti-matter is through high powered collisions. New matter is created from the energy produced in these collisions and some of them are anti-matter particles ...
2
votes
1answer
187 views
What is meant by the rest energy of non-composite particle?
When talking about the rest energy of a composite particle such as a proton, part of the rest energy is accounted for by the internal kinetic energy of its constituent quarks. But what is physically ...
