Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales.
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votes
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504 views
What is the upper-limit on intrinsic heating due to dark matter?
Cold dark matter is thought to fill our galactic neighborhood with a density $\rho$ of about 0.3 GeV/cm${}^3$ and with a velocity $v$ of roughly 200 to 300 km/s. (The velocity dispersion is much ...
10
votes
0answers
200 views
Is there any way to distinguish experimentally gauge mediation from gravity mediation in an unambiguous way?
There are lots of models of gravity mediated SUSY breaking with various spectra as well as various general gauge mediation models. Are there any "smoking gun" experimental singnatures that could ...
9
votes
0answers
86 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 ...
7
votes
0answers
318 views
+100
About defining “baryons” and “mesons”
I want to understand the proof of the claims (of the construction as well as of its uniqueness) of gauge singlet states given around equation 2.13 (page 10) of this paper.
Also does the listing of ...
6
votes
0answers
84 views
Status of experimental searches for tachyons?
Now that the dust has settled on the 2011 superluminal neutrino debacle at OPERA, I'm interested in understanding the current status of experimental searches for neutrinos. Although the OPERA claim ...
6
votes
0answers
20 views
status of +4/3 scalar as explanation of $t\bar t$ asymmetry
One of the early proposals for the Tevatron asymmetry on $t \bar t$ was a "fundamental diquark" with a charge (and hypercharge) +4/3, either in a triplet or a sextet colour. I am interested on the ...
5
votes
0answers
74 views
$WW\to t\bar{t}$ growth
I was told recently that "it is well known that processes like $WW\to t\bar{t}$ ($t$ being a top, or any massive fermion) grows linearly with the energy in the absence of an Higgs boson." Does anyone ...
5
votes
0answers
257 views
How well is the $\rho$ and $\omega$ coupling universality measured?
Is there any good recent experimental data that tests whether the $\rho$ coupling constant depends only on the isospin multiplet of the produced particle?
EDIT: I got a downvote, so I should explain ...
4
votes
0answers
59 views
Are oscillations of electron chirality experimentally observable?
Is there any plausible experiment by which chirality oscillations in electrons could be observed experimentally, such as through some analogy to neutrino oscillation experiments?
4
votes
0answers
36 views
axial and vector resonances in composite higgs models
Is there a reason to believe that the axial resonances be heavier than the vector resonances in the composite higgs models?
For instance, in http://arxiv.org/abs/0808.2071, to have zero tree level ...
4
votes
0answers
118 views
Trace of stress tensor vanishes ==> Weyl invariant
You often see in textbooks the statement that ${T^\mu}_\mu = 0$ implies Weyl invariance or conformal invariance. The proof goes like
$\delta S \sim \int \sqrt{g} T^{\mu\nu} \delta g_{\mu\nu} \sim ...
4
votes
0answers
150 views
Parity and Helicity of the Higgs Boson
I have been studying how the spin and parity of the new boson discovered at the LHC will be studied and have run into some confusion. The Standard Model Higgs is expected to be a scalar (i.e. have ...
4
votes
0answers
109 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
...
4
votes
0answers
148 views
What statistical test should I use?
I have two differential cross sections $d\sigma_{1,2}/dM$ ($M$ is some invariant mass) corresponding to different hypothesis. What I want is to calculate how well the appropriate experiment would do ...
4
votes
0answers
103 views
Is there precision experimental evidence for Furry's theorem — that only even degree VEVs are non-zero?
Is there precision experimental evidence for or contradicting Furry's theorem -- that only even degree VEVs are non-zero, specifically for the EM field?
4
votes
0answers
23 views
Classic mass predictions from Left-Right models with discrete symmetries?
I am covering the classic literature on predictions of Cabibbo angle or other relationships in the mass matrix. As you may remember, this research was a rage in the late seventies, after noticing that ...
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 ...
3
votes
0answers
57 views
Final-state baryons in $p \bar p$ collisions in Pythia
I'm trying to simulate inclusive $\chi_c$ production in $p \bar p$ collisions at very low energies (~ 5.5 GeV) using Pythia8 event generator. Leaving aside problems bounded with applicability of ...
3
votes
0answers
69 views
What is the importance of the Higgs-strahlung process in the Higgs search?
I would particularly like to know why this process is considered the main search mode for Tevatron but useless for search at LHC.
3
votes
0answers
56 views
Can the mass of a SUSY particle depend on the process it participates in?
I believe that mass is property of every particle,as well as spin etc.Now I'm interested in SUSY particles in cMSSM model.Can it be,that mass of a SUSY particle (at one point in five parameter space) ...
3
votes
0answers
138 views
Spin polarization of decay products
A relativistic moving particle, e.g. muon $\mu^+$, described by its four-momentum vector $p_\mu$, charge $e$ and with a given spin polarization, ${\bf S}=(S_x,S_y,S_z)$, decays into three particles, ...
3
votes
0answers
116 views
Dual Resonance Model: Fermions
I am going through Ramond's 1971 paper Dual Theory for Free Fermions Phys Rev D3 10, 2415 where he first attempts to introduce fermions into the conventional dual resonance model.
I get the 'gist' of ...
3
votes
0answers
267 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 ...
3
votes
0answers
185 views
what interactions would take place between a free proton and a dipolariton?
What interactions can be expected to take place between a free proton and a dipolariton, (a) at high energies and (b) at lower energies?
A dipolariton is a bosonic quasi-particle mentioned in a ...
3
votes
0answers
86 views
Proton flux model or data at energy range up to 100 keV
I am looking for a model or at best the database of proton fluxes (solar p+) at a energy range of some eV up to 100 keV. I have already found the SOHO database:
http://umtof.umd.edu/pm/
But the ...
3
votes
0answers
70 views
Seeking chiral anomaly EFT example
If an effective field theory has a chiral anomaly it means that chiral symmetry isn't a symmetry of the underlying theory which has been cut off to make the EFT. My question is whether there's a good ...
3
votes
0answers
104 views
A moderate introduction to Hanbury Brown Twiss interferometry in particle physics
For astronomy as originally invented it is good for finding the angular diameter of stars and is not a rapidly fluctuating observable like the amplitude in ordinary interferometry. The same concept ...
2
votes
0answers
127 views
Field content and symmetry groups of Minimal Composite Higgs Models
I'm trying to teach myself the Composite Higgs Model, both its theory and its LHC phenomenology (particularly the 4DCHM). Unfortunately, I'm struggling; the literature is contradictory and/or omits ...
2
votes
0answers
47 views
Parton Distribution Functions, average cross section of the nucleon
Say we are given the scattering cross section for neutrinos from $d$ and $\bar{u}$ quarks as $\frac{d\sigma^{d}}{dQ^2}=\frac{G_F^2}{\pi}$, $\frac{d\sigma^{\bar{u}}}{dQ^2}=\frac{G_F^2}{\pi} (1-y)^2$, ...
2
votes
0answers
99 views
Strong decays of baryons via quark-antiquark pairs
I have the doubly charmed $\Xi_{cc}^{++}$ consisting of ccu quarks.
This is meant to decay via strong force, producing a light baryon (cud/uuc/udc etc...) and a quark-antiquark pair along with a ...
2
votes
0answers
49 views
Chirality when moving around legs in Feynman diagrams
Assuming one has the following term in a Lagrangian:
$$
g (\overline{A_R} B_L)(\overline{C_R}D_L)
$$
where A,B,C,D correspond to spin 1/2 Dirac particles and the subscripts $R$ and $L$ denote left- ...
2
votes
0answers
113 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 ...
2
votes
0answers
54 views
In a composite Higgs, should the Z0 decay at the same rate that the neutral pion?
I am sorry to ask a question that obviously is a sum of separate questions about a process: Should the decay rate of Z0 be related to the decay of the "higgs" composite field it is eating? And, should ...
2
votes
0answers
93 views
Eternal clocks and 4D spacetime crystals
There was a recent article about the creation of 4D spacetime crystals based on recent theory proposed by Frank Wilczek. This theory is based on breaking time translational symmetry which basically ...
2
votes
0answers
146 views
What makes *electric* charge special (wrt. CPT theorem)?
I'm wondering why the 'C' in CPT - charge conjugation - refers specifically to electric charge. Of course you could say that C is just defined as $e^+ \leftrightarrow e^-$... but there has to be ...
2
votes
0answers
53 views
Are scalars starting at around 1300 MeV analogous to some kind of sound in the vacuum glue?
Are scalars starting at around 1300 MeV analogous to some kind of sound in the vacuum glue?
Background:
There are scalars starting at around 1300 MeV which are probably some combination of ...
2
votes
0answers
58 views
Remaining Potential Experimental Particle Physics Discoveries at the TeV Scale?
With the discovery of the Higgs Boson, some have been calling it the end of experimental particle physics for our generation, due to the fact that all of the particles predicted by the standard model ...
2
votes
0answers
737 views
Decay of Cobalt-60 isotope
How does the Gamma decay of Cobalt-60 occur?
Motivation: A research team led by D. Habs made contributions to our understanding of the gamma decay of Ca-40 and Zr-90: ...
2
votes
0answers
101 views
What results from particle collision would ensure the existence of the graviton?
I understand that particles are smashed together to try to enable us to detect some sort of graviton presence but we can't actually detect a graviton due to the fact that it 'exists' in some extra ...
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 ...
2
votes
0answers
147 views
Can the mass of longitudinal and transverse W bosons be measured separately?
Some higgsless unified models of particle physics predict that the mass of longitudinally polarized W bosons and the mass of transversely polarized W bosons are different.
In those models, a ...
2
votes
0answers
116 views
About the decay of Higgs into 2 Z bosons
I need to know if I understand this point.
The factor of HZZ vertex in the SM Lagrangian is half the value of the Feynman rule which appears in Diagrammatica.
When I calculate the decay of Higgs ...
2
votes
0answers
188 views
Has CERN recently found evidence for a Z-prime boson?
In the recent Higgs seminar at 73:38 Guido Tonelli the spokesman for CMS, makes a mistake and refers to a Z-prime in a context that would imply that they see them frequently. He swiftly backpedals ...
2
votes
0answers
112 views
Treatment of sbottoms in prospino
Could someone please explain the details of the following "propaganda plot" from the prospino website?
There is one curve for stop pair production $\tilde t \bar {\tilde t}$, and one for general ...
1
vote
0answers
52 views
Matrix element approximation
In the formula for the decay width of $\Upsilon(4S)$ to B-mesons from $\text{e}^+\text{e}^-$ collisions:
$$\Gamma_{\Upsilon(4S)\to B\bar{B}}=\frac{\left|\underline{P}_B \right|}{8\pi ...
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vote
0answers
91 views
Mirror Matter Hypothesis?
What is the current state of the hypothesis of mirror matter today?
Are there any experimental data or theoretical arguments that exclude it by now, or is it still considered viable among physicists?
...
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vote
0answers
42 views
Conservation laws in mSUGRA model
Can somebody list all the quantum numbers (beside R-parity) that are conserved in vertex for SUSY particles in mSUGRA model?
1
vote
0answers
79 views
Kinematics algebra, pT, Peskin Eq.17.59
my question concerns the kinematics of 2 to 2 particle scattering. I refer to Peskin and Schroeder eq.17.59 going from this expression
...
1
vote
0answers
57 views
Linear rising potential from a Gribov propagator
It is common wisdom that a gluon propagator (Gribov-)like
$$
G(p^2)=\frac{a+bp^2}{cp^4+dp^2+e}
$$
should give rise to a linear rising potential. So far, I have not seen a proof of this and I would ...
1
vote
0answers
147 views
Describing the Higgs mechanism to non-particle physicists
I'm sure I'm not the only person with this problem at the moment. I have been asked to give a public (not quite public, scientists, just not physicists) about 'this Higgs boson thing'. I am trying to ...
