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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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 ...
3
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1answer
149 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 $\bar{l}_1\sigma_{\mu\nu} r_2 \bar{r}_3 \sigma^{\mu\nu} l_4 =$ $ ...
3
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1answer
246 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 ...
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1answer
81 views

Isn't the Coulomb interaction a photon interaction between two charges?

Isn't the Coulomb interaction a photon interaction between two charges? if yes then what does the following text mean? (Many-particle Physics by Gerald D. Mahan.)
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1answer
47 views

Leptogenesis with singlet neutrinos

(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 ...
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1answer
37 views

How many properties like charge, mass etc any quanta or particle must have?

How many properties are required to measure full energy of a fundamental particle? I know $E=mc^2$, but what about charge, spin, etc? Which full equation would give me all parameters of any particle?
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72 views

Any known relationships among quark masses?

Here is some numerology: Gen 1 Mass(d)/Mass(u) = 2 = 2 * 1 Gen 2 Mass(c)/Mass(s) = 12 = 4 * 3 Gen 3 Mass(t)/Mass(b) = 40 = 8 * 5 Does standard model make any predictions of relations? Do any GUT ...
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1answer
17 views

If we rub glass particles with paper , will there be any charge induction in glass particles?

If we rub glass particles with paper , will there be any charge induction in glass particles ? I know if you rub with silk they do get charged, but i want to know specifically for glass and paper.
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19 views

What is the general definition of signal acceptance?

Suppose I have a beyond Standard Model theory and want to test it. I want to test if some experiments, say conduced in LHC, show signals of the theory. In this case, what is "signal acceptance"?
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55 views

Constraints on new unknown stable fermions?

This question is rather speculative, but I would like to ask it anyway. What are the constraints on possibility of discovering new unknown stable fermions of some sort in the future? If I am not ...
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1answer
196 views

Photons and proper time

Why is there no proper time without inertial frame? In question n°95054 I learned that there is no proper time zero and no proper distance zero for photons because they are no inertial frames. That ...
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367 views

Why does mass in the universe have no limit in large size, but has a limit in small size?

We found VY Canis Majoris, a star so big it can't even be seen in scaled illustratations with the sun itself. However, we stop at particle physics, or quantum mechanics, i.e. particles, subatomic, ...
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79 views

QCD corrections in W boson production

The book "Collider Physics", by barger and Phillips, deals with hadronic W and Z productions, and includes the $K$ factor which represents QCD corrections. However, when dealing with the hadronic ...
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117 views

Decay Amplitudes Notation

This question is mostly about how to interpret notation used in Particle Physics. I am given that at lowest order the rate of $b\rightarrow s\gamma$ is proportional to $\langle B_p|b^\dagger ...
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195 views

decay with initial velocity:

decay with initial velocity: All static particle decay to particles with momentum distribution in the same shape like that's implied by structure function and calculated by MG. but the decay of W ...
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48 views

Is it possible to single out a proton, electron, neutron?

I've read that it's nearly impossible to take a proton from an element. But if it's "nearly" impossible then it is possible to some degree. If this has happened, what is exactly the process of taking ...
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17 views

What does a completely negative Greens function in frequency mean?

What can a Greens function of frequency mean when it is always negative? The Greens function is for the photons as the following: (It's derived by Matsubara method to enter the thermal effects and the ...
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3 views

how to completely remove the charge from the glass bubble particles?

Do you have any idea on how to completely remove the charge from the glass bubble particles (25-32 micrometer diameter)? Thanks
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5 views

What is 'transparency rate' for ionization chambers?

I was reading a paper a little while ago and I saw that the author noted the 'transparency rate' of an ionization chamber. The ionization chamber had field shaping wires at the entrance and exit that ...
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19 views

Materials on charged black brane

everybody! Does anyone know some good materials on charged black branes in AdS/CFT and the role of chemical potential in theses cases?
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29 views

When optically pumping a lasing gain medium with another laser, does Stimulated, or Spontaneous emission dominate?

Much of my reading seems to indicate that laser pumping results in a fluorescent stokes shift but somehow photon vector is maintained. I've seen the phrase "Spontaneous Fluorescence by Stimulated ...
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24 views

Is the continuity (discontinuity) one of the intrinsic properties of all physical objects?

Is the continuity (discontinuity) one of the intrinsic properties of all physical objects? How do we define continuity? Which of the definitions of continuity are used (and why) in physics? This ...
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17 views

Penning Trap Simulation

I'm currently working on a particle tracker and I would like to implement a Penning trap. I think I might have a problem with the field of the electrical quadrupole. My idea was to place 2 dipoles and ...
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35 views

Constant Rayleigh Scattering Cross Section

in the Review of Particle Physics - Interactions of Particles with Matter, there is a plot that gives the cross sections for different interactions of photons with matter. One of them is Rayleigh ...
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39 views

Is there a machine readable format of the data tables in Particle Data Group PDFs?

Is there a machine-readable format of the tables of data in PDG documents such as this one? http://pdg.lbl.gov/2011/download/rpp-2010-booklet.pdf Something such as JSON, XML, CSV, HTML, or anything ...
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45 views

Nuclear Interaction Stopping Power

Hello again question board. I'm in need of some help with my b) question for homework I have. Following question is verbatim: "How thick should a wall of shielding iron be to absorb a 10 GeV/c pion ...
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105 views

General definition of vector spinor and spin

I am looking for basic and exact definitions of fundamental physical consepts in graduate level. I reach this following definitions. Could you please help to improve these definitions. Spin: ...
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55 views

Mathematical formalism to include wave and particle perspectives of light

Does the exist any mathematical formalism (model) describing the behavior of light and incorporating its particle character (divisibility, quantization) and wave character? (i.e. quantized wave model) ...
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15 views

in an organic semiconductor, what is the average distance travelled by an exciton?

In an organic semiconductor, what is the average distance travelled by an exciton up to recombination? How is this value related to the morfology / structure of the organic semiconductor?
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15 views

Can we say that nanomaterials have higher cohesive energies compared to coarse-grained counterparts?

Can we say that nanomaterials have higher cohesive energies compared to coarse-grained counterparts?
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23 views

Is there a finite frequency of physical interactions?

If particles use gauge bosons to convey information about various forces then is there something like a finite "refresh rate" at which they update information about themselves?
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36 views

How to find particle number fluctuation under given condition?

So we know the particle number fluctuation of a one room. Let it be equal to ФN, and we have to find the particle number fluctuation of a big room, which is just n times bigger, than a smaller one. ...
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28 views

Nilsson Hamiltonian - looking for problem and answers

I have been looking, unsuccessfully, online for academic problems involving the Nilsson nuclear hamiltonian. I understand the nature of the terms in the equation, but have never seen actual ...
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35 views

Quantum Hall Effect Dark Matter Detector?

Has anyone used a Quantum Hall effect detector to detect dark matter? I was looking at the following animation on wikipedia: ...
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66 views

What is the most fundamental peice of matter? What is it that thing which can no more be sub-divided?

I know that there is theory that strings are the most fundamental particles. But if it is a string, then it can be 'cut' into pieces, and if it can be 'cut', then it can be cut at infinitely many ...
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34 views

Quantum distance ladder

There is a lecture on how facts about the cosmos can be derived form rather simple observation. Is there an analogy for the small scale? Is there a technically simple observation that would imply, ...
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11 views

multiple frequency trapped power signal

is there any possibility to generate a waveform that consists of multiple power signals with different frequencies such that these signals travel together like they constitute [to form a ...
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80 views

Calculating the Neutron Stopping Power of complex materials

Is there a fast and convenient way of calculating the neutron stopping power of materials, consisting of multiple elements (e.g. doped crystals) without the need for Monte Carlo Simulation, that is ...
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76 views

Born rule and Feynman propagators

Let us assume that we want to describe the full process of photon emission by electron A and absorption by electron B. Therefore electron B must be on the forward lightcone of electron A. In the ...
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35 views

References on the LHC experiments

I'm looking for a references / short book which discusses what is going on LHC collider - specific experiments, collision processes, analysis of data, how exactly the facility is operating (not ...
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65 views

Lorentz force helix

I have a few questions about the Lorentz force. Is it possible to create a Lorentz force helix in a cloud chamber and if so how would this be achieved? How would the pressure inside the helix be ...
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38 views

Yan - Drell process

I'm looking for more information about Yan - Drell process but didn't manage to find a good place to learn from (still looking for one). I understood that this process can help us to understand the ...
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57 views

Fermi's weak interaction theory

In Fermi's theory, we have energy squared in the numerator of the cross-section which makes it diverge as energy increases. But isn't that the Fermi constant suppresses it with increasing order?
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79 views

Reduced graphs and pinch-singular surfaces

I am reading a book on perturbative QCD by John Collins. In Chapter 5, the terms reduced graph and pinch-singular surface are used for the analysis of mass singularities. However, their meanings are ...
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173 views

Will the absorption of high energy gamma rays end up heating the absorping material?

By high energy I mean 100+ MeV gamma rays. I think that at this energy of photons, pair production is the dominating absorption process. So, as known, in pair production an electron and a positron ...
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81 views

Neutrons in nucleus

When I asked here why neutrons in nucleus (with protons) don't decay I was told that it would require energy for the neutron to decay, it wouldn't give energy. And since that wasn't really what I ...
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229 views

Pair annihilation - how to generaly solve these types of problems?

Simple question regarding pair production: Can a collision of an electron with a positron result in two photons? I have this problem to solve and I doubt this is even possible. Please provide some ...
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65 views

Preons and 't Hooft condition

If some fundamental particles, like leptons or quarks are composite (e.g.in preonic models), or the same with gauge bosons or the higgs particles. How could it be possible that preons were more ...
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51 views

the effects of an ln-prime transformation to physical models

I have rather a "toy" type of modelling-problem that appeared to me along a book I am writing on number theory. I would be outmost thankful for any concrete or inspirational answers, including ...
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42 views

why is the modelisation of elementary particle as a two dimensional object in contradiction with General Relativity?

This is asserted by Trinh Xuan Thuan in his book "Chaos & Harmony" chapter String theory.