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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2answers
20 views

WIMP dark matter annihilation rate equation (approximation)?

WIMP is a possible dark matter candidates, which self-annihilates. What is the WIMP annihilation rate, as a function of density? Most sources state this scales as $\rho^2$, (density squared), but ...
10
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2answers
785 views

Deriving Feynman rules from a Lagrangian for vertex factors for “more complicated” interactions

I am trying to derive Feynman rules from a given Lagrangian and I got stuck on some vertex factors. What for example is the vertex factor that corresponds to the four-scalar interaction that is ...
1
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0answers
19 views

Upsilon full decay width? (and reference request)

The decays of 1S, 2S, 3S states of the $\Upsilon$ meson are according the particle data group surprisingly stable, but not as stable as a typical weak-only decay. Some electromagnetic decays, such as ...
-1
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0answers
44 views

Hydrogen is the ONLY Element? [on hold]

Let's say you have Hydrogen and it's isotopes, Can you fuse them together to create all the 118 elements, by fusion or something else, Can anyone give me any research paper or anything which gives ...
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2answers
65 views

What is voltage?

I am a little unclear on what voltage actually is and I am trying to find out what the physical cause for voltage is. Is it the speed of the electrons through the conductor or is it an excess of ...
2
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0answers
22 views

How to let Pythia to output the complete event record in LHEF or StDHep format?

I am currently using Pythia 6.4 to simulate some processes (I do not have the intention to upgrade to 8). Now, I need Pythia to output its event record in the format of LHEF or StDHeP. I accidently ...
4
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1answer
336 views
+50

Why should the mass of leptons to be near of proton and QCD/chiral scales?

The mystery of the mass of the top being in the electroweak scale can be justified by the Higgs mechanism itself; in some sense the top mass is the only "natural" mass, the other masses of fermions ...
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0answers
110 views
+50

should the Z0 decay at the same rate that the neutral pion?

The original title of the question was "In a composite Higgs..." and so the sub-questions were done around this theme: Should the decay rate of Z0 be related to the decay of the "higgs" composite ...
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0answers
22 views

can light bounce off another light? [duplicate]

If light is a wave and a particle (wave particle duality), is it possible for light to bounce off another light since light bounces of another matter(particle)?
-1
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1answer
60 views

How to model matter in code [on hold]

I've always had a passion for science, understanding and programming. Given my interests, I thought a cool thing to do would be to model real world theories in code (with visuals) so that others may ...
12
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2answers
437 views

Alejandro Rivero's correspondence: diquarks and mesons as superpartners of quarks and leptons

The idea of “hadronic supersymmetry” originated in the mid-1960s and derives from the observation that baryons and mesons have similar Regge slopes, as if antiquarks and diquarks are superpartners. ...
1
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0answers
43 views

GUT predictions for charm mass?

Most GUT models have some relationship between down-type quarks and leptons, that more or less agree with the observed values after running the renormalization equations. But, what about up-type ...
1
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0answers
27 views

Covariant projection method - Meson bound states

I have seen many papers that discuss the production or decay of mesons ( quark bound states ) to make use of the covariant projection method where the product $\upsilon\bar{u}$ of the quark spinors ...
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1answer
16 views

Is the decay of the positive Kaon into 3 pions a weak processs or strong one?

The strangeness is not conserved in the decay of the positive Kaon into 3 pions. so this decay should be a weak process but on the other hand parity is conserved in this decay. Kaon has odd parity and ...
4
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1answer
197 views

Can the Higgs condensate be described in terms of creation operators?

In superconductivity, the BCS condensate can be described in terms of 2 creation operators (the 2 electrons of the pair) acting on the vacuum. I'm wondering whether a similar description can be given ...
1
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0answers
14 views

Collision symmetry and measuring the asymmetry in the Drell-Yan process

I saw a talk the other day about an asymmetry in the Drell-Yan process caused by CP-violation: Apparently one way this can be measured (ATLAS is doing this) is to collide protons and observe the ...
6
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0answers
34 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 ...
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0answers
34 views

Infinitesimal transformation by Noether's charge [on hold]

Can anybody explain me the physics of the commutation relation : $ [Q,\phi_{i}] = it_{ij}\phi_{j}$ ; where, Q is Noether's charge and $\phi_{i} (i=1,2)$ are components of an isodoublet?
3
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2answers
107 views

Can quarks be considered elementary?

In our current theories all hadrons are made up of quarks and gluons. This view reduces considerably the big family of hadrons by providing a very logical structure in which all quantum properties ...
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0answers
24 views

Properties of vector potential

Given the definition of vector potential as, $ A_{\mu}= \sum_{k} \partial_{\mu}\theta F^{k}$ , where F are the generators and $\theta$ are the parameters of the symmetry group. I have two questions ...
2
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0answers
32 views

Gauge transformation and Special relativity

While explaining gauge theories, a book makes a comment that the U(1) transformation definition, $ U= e^{i q \lambda(x)}$ is analogous to a special relativity transformation in freely falling ...
0
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1answer
64 views

Fractional number of particles in the universe?

Is it possible, that the metagalaxy contains a fractional (non whole) number of particles or fractional number of a particular kind of particles (such as electrons)? Sorry, if my question is stupid, ...
-2
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1answer
52 views

Probablity Wave and Wavefunction [closed]

Are wave function and probability wave same? Well I am a bit confused about wavefunctions and probability waves. I read in Fabric of the Cosmos by Brian Greene that they are same. Please help me and ...
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3answers
201 views

Why do electrons and positrons exhibit opposite helical motion in a magnetic field?

When you throw an electron through a solenoid, it moves helically around the field lines, as per this schoolphysics illustration: © Keith Gibbs 2013 Then if we were to throw a positron through the ...
3
votes
3answers
394 views

What is a particle?

I posted this elsewhere also and just found this place so copied it down but yeah. I've always wondered this cause I like wondering bout things but I wanna know and it's simple so I should. I got an ...
1
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0answers
36 views

Is there a local canonical ensemble partition function for a Bose-Einstein gas?

The grand canonical partition function for a Bose-Einstein gas is $$ Z_{\text{grand bos}} = \exp \left( \sum_{j=0}^{\infty} -\ln \left( 1-e^{\beta(\mu-\epsilon_j)} \right)g_j \right) $$ where $\beta$ ...
-1
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1answer
57 views

Why should an electron orbit decay?

I have heard physicists say that 'if' an electron was a particle then it's orbit would decay so it would crash into the nucleus. How do they propose that it would lose it's energy in order to decay?
0
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1answer
41 views

Is possible to use optical fiber to transmit light to streetlights? [closed]

I was thinking about this idea: Only one lamp, inside a optical fiber structure, transmitting all the light through a lot of optical fiber cables direct to streetlights. (I guess that the cables ...
1
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1answer
19 views

Why do I not observe single/double escape peaks for K-40

A question on gamma spectrometry here. If I'm looking at a background gamma spectrum with a big peak at 1460KeV (approximately 180 counts) and I attribute this peak to the presence of K-40, should I ...
0
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1answer
118 views

If a black hole is just warped spacetime, then where is the electric charge?

I've heard Kip Thorne repeatedly state that matter is destroyed when a black hole is created, that all you are left with is distorted spacetime. "The idea that black holes are made from very ...
0
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1answer
77 views

What's the difference between vacuum particle-antiparticle annhiliation and regular annihilation?

Why does vacuum particle-antiparticle creation and annihilation result in nothing rather than photons? What is the difference between that and regular annihilation that does result in photons.
1
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1answer
27 views

Nuclear decay of V-48

I have a question on the "decay" of Vanadium-48. The reason it's in inverted commas is because I'm not sure whether decay is the right word. Basically what I'm trying to work out is whether it's ...
6
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2answers
279 views

Scalar field divergent mass correction interpretation question (hierarchy problem)

Simple power counting tells you that a scalar field coupled to some fermions at one-loop picks up a correction to the mass of the order $\Lambda^2$. Based on this people say things like "it's natural ...
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1answer
110 views

If there is a boson that carries mass, why not space, or time? [closed]

If the Higgs Boson carries mass, why doesn't there exist more bosons that carry other fundamental properties such as volume/distance (space), time, or even spacetime? Also if bosons carry force, but ...
1
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0answers
34 views

Is there any difference in mixing and oscillation of neutral mesons?

I have often read about neutral Kaon oscillation or neutral B meson mixing. Both are described by the similar box diagrams. So I want to know if we can say neutral kaon mixing and D meson oscillation. ...
0
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1answer
17 views

What is the total velocity/force on a particle in fluid?

I am now facing a fluid-particle interaction problem. I would like to simulate particle motion in a fluid. I do know the external force acting on a particle (dielectrophoretic force in this case) ...
8
votes
2answers
308 views

$t\bar{t}$ asymmetry

Some weeks ago, there was lots of talk about this CDF paper: Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production where they measured a much higher asymmetry than ...
9
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2answers
855 views

ATLAS and CMS calorimeters

I was reading this interesting recent review on arXiv about particle identification: "Particle Identification" by Christian Lippmann (2011), arXiv:1101.3276 In figure 2, there is an interesting ...
3
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1answer
36 views

One-point function and VEV in $\phi^4$-theory

Why is it that the one-point function in the $\phi^4-$theory, for example calculated from the generating functional, always gives zero value in absence of external source i.e., $J=0$? If there is ...
0
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1answer
57 views

Spin angular momentum

Spin angular momentum is defined as $\Sigma^{i}= 1/2 e^{ijk} \sigma_{jk}$ . Thus, I can write $\Sigma^{1}$ as $[\gamma_{2},\gamma_{3}]$ . I want some insights on this definition. Also, Can anybody ...
0
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1answer
64 views

How do gluons form virtual top quark or bottom quark loop?

Main mechanism for the production of a higgs boson in Large Hadron Collider is the gluon fusion that is two of the gluons binding these protons collide and those energetic gluons form virtual top or ...
1
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0answers
28 views

How come plasmon resonances of metals are capable of being tuned to different wavelengths?

I read in this article that plasmon resonances though being a pre-determined property of a metal are capable of being tuned to other wavelengths when these same metals are made into tiny ...
3
votes
1answer
107 views

Singlet neutrinos decaying to Higgs bosons during leptogenesis

(i) The Lagrangian of electroweak model extended with right-chiral singlet neutrinos $N_{iR}$ contains the Yukawa coupling term+ the bare Majorana mass term $$f_{\alpha ...
0
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1answer
35 views

How long is a higgs boson stable for before it fully decays?

How long after the creation of a higgs boson is it stable for on average?
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2answers
47 views

When a charged particle absorbs a photon, does the particle get 'pulled' or 'pushed'?

When a charged particle absorbs a photon, does the particle accelerate towards where the photon was coming from or where the photon was going
1
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1answer
59 views

Why standard model particles cannot be dark matter particles

I'm interested if any of the particles in the standard model could be potential candidates for dark matter? I know that we do not see dark matter, therefore dark matter does not interact ...
4
votes
1answer
294 views

Fierz identity for Weyl spinors in tensor currents

Using Fierz identity I found that certain four-fermion operator with left $l_i$ and right-chiral $r_i$ Weyl spinors vanish $\bar{l}_1\sigma_{\mu\nu} r_2 \bar{r}_3 \sigma^{\mu\nu} l_4 =$ $ ...
0
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3answers
62 views

Are there an even number of particles in the universe

I generally understand that every particle has an anti-particle that is created along with that type of particle with opposite effects (unless there is no charge), and that if that anti-particle comes ...
2
votes
1answer
235 views

Classical models with unbounded particle number

Is there any classical model which deals with the birth, life and death of particles? What application could it have? I am talking about a 'billiard-ball' kind of model, but the kind in which balls ...
1
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1answer
85 views

Why cannot massless particles carry charges? [duplicate]

How to show that massless particles do not carry charges from QFT's point of view?