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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17
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335 views

“S-duality” between confinement and the Higgs mechanism?

I feel picked by the second to last sentence in this answer to a question about what would happen if EM and QCD were spontaneously broken, which says "In fact, there is a sense in theoretical ...
16
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0answers
256 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 ...
14
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0answers
361 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 ...
10
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0answers
50 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 ...
9
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0answers
173 views

In a universe with four spatial dimensions would there be elementary particles with intrinsic isoclinic spin?

Elementary particles have an intrinsic property called spin which is different from classical spin as it does not involve actual rotation and the magnitude of spin cannot be changed but particles with ...
8
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0answers
461 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 ...
7
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0answers
131 views

Do photons generate gravitational waves since they affect with their energy the stress tensor?

The gravitational waves are fact. They are produced in a way predicted 100 years before by Einstein. Anything with energy affecting stress tensor of space time produces them. What does it happen with ...
7
votes
0answers
82 views

Distinguishing between left-handed and right-handed weak coupling from electron-neutrino scattering

This question comes from Schwartz's QFT book, exercise 13.6. In it we consider a coupling between fermions (neutrinos and electrons in this particular case) and the Z boson of the form $g_V \bar{\psi} ...
7
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72 views

What happens to Hydrogen-Boron plasma at 3 billion Kelvin?

A recent popular report states (beware, I believe it is not peer reviewed and this slightly smells like a PR stunt) that a private company TriAlpha has made some notable progress towards Hydrogen-...
7
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0answers
267 views

Integration & bremsstrahlung calculation

In this paper (relevant pdf section) that I'm reading, involving the calculation of bremsstrahlung in electron proton scattering (diagram below), the author calculates the integral over outgoing ...
7
votes
0answers
854 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 ...
6
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0answers
62 views

If there are long-lived elements in the Island of stability, why are they not present in Nature?

To my understanding, some (but not many) physicists speculate that the Island of stability may contain long-lived elements, as in a billion or so years. But couldn't we rule that out just by the ...
6
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0answers
80 views

Reference on stages of heavy ion collisions in particle physics

Is there any reference (book/review article etc.) where the physics of heavy ion collisions is overviewed? To be absolutely clear about things, I am looking for a introductory review which covers ...
6
votes
0answers
375 views

Strong interacting v.s. Strong Coupling v.s. Strong Correlated

One of the active research areas in present is Strong interacting, Strong Coupling, Strong Correlated regime of the phases of matters. It seems to me that some physicists in the fields often mix the ...
6
votes
0answers
618 views

Entanglement entropy and area law

I am currently reading a review "Area law for the entanglement entropy" by Eisert, Cramer and Plenio (2010). From what I understand: In one dimension, for local gapped models, we have an area law ...
6
votes
0answers
230 views

Could sphaleron-induced proton decay also cause vacuum decay?

I will say right away that I don't mean standard-model sphalerons, I mean the sphalerons of some extension of the standard model. The reason to even think about this is last year's paper by Frampton ...
6
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0answers
160 views

Categorizing solutions to Hierarchy problem

We know that no gauge symmetry can prevent a term $m_\phi^2|\phi|^2$ for a scalar field, and that, given the quadratic loop corrections, the natural scale is $m_\phi \sim M_P$. This is related to the ...
6
votes
0answers
142 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 ...
6
votes
0answers
82 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 ...
6
votes
0answers
538 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 \...
6
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0answers
272 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 ...
6
votes
0answers
202 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 ...
6
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0answers
88 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 ...
6
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0answers
192 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?
5
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0answers
115 views

Large Hadron Collider 2015 upgrade, what may we discover?

I realise that the initial answer to my question that may come to mind is, "we don't know yet, obviously" But my question is hopefully not opinion based. For example, does this upgrade have a ...
5
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0answers
84 views

Which cosmological dark matter theory is most compatible with current particle physics?

This occurred to me while I was writing Why hasn't warm dark matter replaced cold dark matter as the standard model of cosmology? but I think this deserves a question of its own. The background ...
5
votes
0answers
531 views

Smallest minimum feature size possible for transistors printed by photolithography

I'm doing a project about Moore's Law, one of the subtopics I've come to is photolithography. The way I understand it is that the MOSFET transistors are currently printed on a silicon wafer by ...
5
votes
0answers
164 views

Physics of Anathem

Disclaimer: I am not asking whether or not the events that occur in Anathem are possible. I understand that this book is a work of speculative science fiction and this site has no interest in it as ...
5
votes
0answers
68 views

Helicity dependence in loop diagrams

I am trying to evaluate a diagram that looks like The middle of the diagram is a fermion loop. I know that the coupling between the $Z^0$ and fermions depends on the fermions' helicities, so it ...
5
votes
0answers
219 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 ...
5
votes
0answers
104 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 ...
5
votes
0answers
38 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 ...
4
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0answers
49 views

Calculating statistical significance of peak over background in counting experiment

I histogrammed the invariant masses of particular events in a counting experiment. There is a specific peak which towers over the expected exponential background. How can I give the statistical ...
4
votes
0answers
60 views

Appropriate fit function for $\phi$ meson mass from $K^{+}K^{-}$ pair

I am attempting to measure the mass of the $\phi$ meson using the decay mode $\phi \to K^{+}K^{-}$. I have isolated the $\phi$ meson candidates using this decay mode, and have constructed the graph ...
4
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0answers
24 views

Physical inituition for axial and vector form factors of a hadron

I often see a decomposition of the matrix element $\langle V|\bar{q}\Gamma^{\mu} Q |P\rangle$, where $V$ is a vector particle, for example a vector meson or a photon, $P$ is a pseudoscalar meson, and $...
4
votes
0answers
42 views

What is the difference between Breit-Wigner mass and pole mass in PDG?

In Review of Particle Physics 2014, page 81, in the baryon summary table, there are usually noticeable differences between Re(pole position) and Breit-Wigner mass, for example, for $N(1440)$, $M_{BW}=...
4
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0answers
176 views

How are bound states handled in QFT?

QFT seems very well suited to handle scattering amplitudes between particles represented by the fields in the Lagrangian. But what if you want to know something about a bound state without including ...
4
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0answers
180 views

Scattering, Perturbation and asymptotic states in LSZ reduction formula

I was following Schwarz's book on quantum field theory. There he defines the asymptotic momentum eigenstates $|i\rangle\equiv |k_1 k_2\rangle$ and $|f\rangle\equiv |k_3 k_4\rangle$ in the S-matrix ...
4
votes
0answers
47 views

What processes contribute to non-relativistic proton-antiproton collsions (annihilation)

I wonder what the dominant contributions of nuclear interaction to non-relativistic proton-antiproton annihilation are (I mean that the proton and antiproton are non-relativistic. The products might ...
4
votes
0answers
40 views

$ZZ^{(*)}$ decaying to leptons mass spectrum

I was looking the mass spectrum of the $ZZ^{(*)}$: and I was wondering why the shape is the way it is. The peak around 90 GeV is the single Z resonant, what is reason behind the slight peak in the ...
4
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0answers
31 views

What are hadronic uncertainties?

I am reading articles about recent findings at CERN and the possibility of New Physics contributions, and they keep saying that the discrepancies may be due to hadronic uncertainties... What are they?...
4
votes
0answers
182 views

Baryonic density in collision experiments

Does anyone know any way of estimating the net baryon density in collision experiments, e.g. in LHC, RHIC, or the upcoming ones at GSI-FAIR? I have comes across many hand-waving arguments, sample - ...
4
votes
0answers
280 views

Jet rapidity vs. Pseudorapidity

thanks to this post Why is pseudorapidity defined as $-\log \tan \theta/2$ I got a better understanding of what makes (pseudo) rapidity an interesting an often-used concept. Tangentially working ...
4
votes
0answers
152 views

Anomaly cancellation and fermion number violation

In the standard model, an axial $SU(3)$ currents has anomaly which after quantization leads to the fermion number violation. However, taking all the fermions into account we note that the anomalies ...
3
votes
0answers
50 views

Branching ratio for a bound state

Consider the meson $\Upsilon(10860)$. It decays into $B\bar{B}$, $B\bar{B}^*+cc$ and $B^*\bar{B}^*$. The mass of $B$ is $5.28 ~\textrm{ GeV}$ and mass of $B^*$ is $5.33~\textrm{ GeV}$. The branching ...
3
votes
0answers
18 views

CP violation in B meson system through mixing

Mathematically, $\left|\Gamma_{12}\right|<<\left|M_{12}\right|$ implies $\left|q/p\right|=1$,i.e there is no CP violation due to mixing. Please explain why it happens beyond this mathematical ...
3
votes
0answers
42 views

Derivation of Gell-Mann Okubo relation for mesons

In SU(3) quark model of hadronic structure one assumes that mass splitings between hadrons is due to difference between masses of $s$ quark and $u,d$. This is modeled by perturbation Hamiltonian $$ \...
3
votes
0answers
75 views

The mass of X Boson (and Y Boson too)

I was reading an article on Wikipedia about the hypothetical particles called $X$ and $Y$ Bosons. Looking at their "calculated" masses, I felt quite weirded. Their mass should be $$m = 10^{15}\ GeV/...
3
votes
0answers
75 views

Is $PT$ always a symmetry in (2+1)D?

Is the combination of parity $P: (x,y,t)\to (-x,y,t)$ (sometimes also called reflection $R$) and time reversal $T: (x,y,t)\to (x,y,-t)$ always a symmetry in (2+1)D theories with Lorentz or Galilean ...
3
votes
0answers
87 views

$\rho$-parameters for several Higgs multiplets

I'm studying the Higgs mechanism of the spontaneus symmetry breaking in the SM. The expression for the $\rho$-parameter is $$ \rho=\frac{M^2_W}{{\cos^2\theta_w}M^2_Z}, $$ that, in the case of a $SU(2)...