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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Is the Higgs field responsible of only 1% of the proton mass?

This post is a sequel of: Where does the majority of the mass of the usual matter come from? The following answer of @hft: Your question asks why the "current quark masses" [see ...
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164 views

What determines the probability of creating a particular particle in a collision?

When discussing events at the quantum level, we deal in probabilities and not absolutes. Articles I've read on particle physics state that a particle has a probability of being created in a collision. ...
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51 views

Mechanism for inelastic collisions in the particle world

We know that inside particle accelerators we collide ionized particles. But we also know that in the microworld all collisions are elastic (due only to the electrostatic force?) between the particles. ...
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98 views

What is high energy physics?

Is high energy physics the same as particle physics? Does research in high-energy physics include things like quantum gravity, string theory and quantum field theory? Is unifying the four ...
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106 views

Why are electrons alike but photons not?

Perhaps this is a misconception, but why are electrons alike and photons not? Given two photons, they may differ by having different frequencies (energies). Given two electrons, there are just two ...
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46 views

Charge of $W$-bosons in Feynman diagrams

When looking at Feynman diagrams of particle decays, how would I be able to find out the charges of the $W$-bosons involved in the decay?
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42 views

A particles lifetime in relation to the speed it travels with

Is it possible for a particles or any matter's lifetime in the universe to depend on it's speed?
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58 views

Do matter and antimatter annihilate or release energy?

Do matter and antimatter eliminate each other or release their equivalent energies? I'm almost certain it's the latter as mass can't be destroyed, but when speaking of the big bang it's said if there ...
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109 views

How many of the Standard Model free parameters are mutually independent: (all of them)?

My knowledge of the standard model is very limited so please let me spell out my assumptions first (and please let me know when I have mangled concepts, terminology or I am plainly just out of my ...
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79 views

Does an object traveling near the speed of light create a gravitaional field? [duplicate]

Does a particle traveling near the speed of light create an observable/measureable gravitational field around it? I know most elementary particles travel near the speed of light and have no ...
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39 views

Physical proceses before the breaking of $SU(2)_L\times U(1)_Y$ symmetry

The energy scale which the electromagnetic and the weak interaction were unified, there were 4 massless gauge bosons: 3 corresponding to the unbroken generators of $SU(2)_L$, say $W_{\mu}^{1,2,3}$ ...
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Thomas precession and neutron star accretion discs

Assuming, based on this wikipedia article Accretion Discs That accretion discs surrounding neutron stars are composed of a gas and / or plasma. That the accretion disc material can achieve a ...
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173 views

How can an infinitesimally small object rotate?

How is it possible for an object like a black hole or electron to spin since they are made up of no other components? If my understanding is correct, an electron is an elementary particle which means ...
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40 views

Can high speed moving hydrogen atoms drive turbines?

We know that hydrogen is a part of air so if we accelerate hydrogen atoms in a circular vacuum tube as done in a particle accelerator, can the high speed moving atoms of hydrogen drive a turbine if we ...
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Is there a time difference for people traveling at different speeds during a long period of time?

I'm just throwing this out there for discussion/answering: If person A sat in a chair all his life, in a house on earth (let's say 100 years), and person B flew around in earth's atmosphere at let's ...
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69 views

In QFT are fields considered a property/function of spacetime? How do they become “excited”?

I am a total layman in physics, but I've been trying to understand the various existing theories and after reading/watching lectures on QFT for months I still can't find an answer to a few very basic ...
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43 views

Differential cross section $d\sigma/dp^{\gamma}_{T}$?

Why we care about $d\sigma/dp^{\gamma}_{T}$? What the physical meaning of it? Why not plot $\sigma$ follow $p^{\gamma}_{T}$?. As in this picture.
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64 views

Angle between two momenta in particle physics (principal axis of a two-body decay vs. center-of-mass motion in the lab)

Situation: I have events with a W-Boson decaying into two leptons (e.g. electron and electron-neutrino). Now I want to see, whether there is an angle range into which the leptons are emitted ...
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57 views

How do quarks have no spatial extent?

I found an answer to a question I had and that is that quarks have no spatial extent. But how is that possible? Everything has to have some spatial extent; to keep continuing on and on, right?
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Synchrotron radiation derivation

In the derivation of synchrotron radiation in a standard text (J.D. Jackson/Rybicki & Lightman), we do it by taking instantaneous circular motion of the electron, because the power emitted by ...
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53 views

Maximizing particle annihilation of a certain particle type?

Is there any theoretical situation where one would be able to maximize the production of a certain type of particle? I wish to continue discussing this question: Where would dark matter be produced? ...
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65 views

Where would dark matter be produced?

There are a zoo of dark matter candidates. Are there any candidates which could be produced in extreme conditions such as black holes/active galactic nuclei/pulsars? After reading an article on WIMPs ...
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43 views

Why in particle physics the background of resonance is a decaying exponential?

When in particle physics they plot the mass histogram we see a resonance on top of a decaying exponential background? Why is the background modeled to be that way? what is the physical explanation? ...
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1answer
37 views

How many combination can quarks form?

How many different combinations can quarks produce? E.g. 2 up quarks + 1 down quark = proton. Is this value going to be infinite?
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50 views

Physical significance of momentum eigenfunction

In an introductory textbook of Quantum Mechanics, I found the momentum eigenfunction in position space to be given as Ne^ipx/h. Where N is the normalization factor and i is root of -1. I don't ...
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45 views

Would infinite material cause a black hole?

If you have an infinite amount of any material(That doesn't have a critical mass to have nuclear reactions), would this matter form massive black holes that condense into an infinite black hole? Two ...
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60 views

What is meant by a preliminary run at the LHC?

I am a bit confused over the meaning of "Preliminary run" when referring to the LHC experiments CMS and ATLAS. For example in this summary, Figure 2 refers to both the CMS $19.7\ \mathrm{fb^{-1}}$ ...
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What tell us know that Parton distributions and Fragmentation function are non-perturbative part of QCD?

I read some document I see Parton distributions and Fragmentation function are non-perturbative part of QCD. Have document tell about that?.
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36 views

How is the stability of Higgs vacuum affected? [duplicate]

What is meant by standard model vacuum? Is it same as the the vacuum of the Higgs potential? What is meant by the stability or instability of vacuum? And how is Higgs self-interaction responsible for ...
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67 views

What are the differences between the Jetphox, Pythia and Herwig event generators?

I know Jetphox is a parton-level event NLO generator program. But I want to know more about other generator programs such as Pythia and Herwig. What are the differences? I am undergraduate student so ...
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1answer
364 views

Why do we ignore rotational energy in monatomic gases? [duplicate]

I understand that the average energy of each degree of freedom in a thermodynamic system is $\frac12kT$. And so, for an ideal monatomic gas, there are three degrees of freedom associated with the ...
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65 views

What are these arcs in bubble chamber photos?

In photos such as this one, or this one (too large to fit inside post), what are the highly frenzied arcs that are really prominent in these photos? Are they simply physical walls in/of the ...
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1answer
52 views

Preventing Heat Escape

Is is possible to completely prevent heat from escaping from a closed container? Here is a diagram of vacuum flask, which tries to implement the design - Vacuum Flask prevents heat from escaping ...
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20 views

Fun physics book for high school student [duplicate]

can anyone recommend me a physics book for a highschool student (not these typical school books) a book that will let you think mostly interested in theoretical /quantum physics done with the ...
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Origin and motivation of various flavor symmetries in the neutrino sector

Flavor symmetries of various kinds (for example, $\mu-\tau$ permutation symmetry, or the scaling symmetry, or $S_3$ symmetry) are sometimes assumed between neutrino flavours to "reproduce" the ...
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77 views

Particle annihilation - mathematical description, equations governing it? [duplicate]

I was wondering about this and I would like to know an explanation why do particles and antiparticles annihilate? I would be interested in phenomenological, but most importantly mathematic explanation ...
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18 views

Particle aggregation: difference between coagulation and coalescence?

I know there are different processes involved in particle aggregation, and that depending on temperature and other factors one of them may be more significant. I know that particles can aggregate, ...
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1answer
40 views

Energy of a system if the nuclear repulsion increases

I have calculated the optimised geometry for a molecule. I have noticed that the energy of the nuclear repulsion increases with each iteration of optimisation. What is the logic behind this?
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48 views

How is mass conserved when a muon decays?

A small disclaimer: I am a layperson and not a formal student of physics so forgive any glaring stupidity betrayed in the nature of the question. A muon is supposed to always decay into an electron ...
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52 views

Trying to derive compton scattering using 4-vectors [closed]

I'm trying to derive the energy of a photon after compton scattering: $$ E_\gamma' = \frac{E_\gamma}{1 + \frac{E_\gamma}{m_ec^2} (1-\cos \theta)}$$ where $E_\gamma'$ is the photon energy after ...
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73 views

meaning of Higgs coupling is flavor conserving

I have heard the statement that the Higgs coupling is flavor conserving. What does it mean? What kind of coupling would be flavor non-conserving?
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53 views

Why is cut-off regularization is not Lorentz invariant?

Why is it said that the cut-off regularization is not a Lorentz invariant regularization method?
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78 views

Rest Mass and Wigner's Classification

I believe (but please correct me if I'm wrong) that I understand the basic philosophy and most of the mathematics involved in Wigner's classification of particles via group representations. But I'm ...
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384 views

Pair production by collision

Electron Positron pairs can be created via three process: Photon-Photon interaction Photon-Particle interaction Particle-Particle interaction I want to know how 2. and 3. can create electron - ...
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1answer
59 views

What's the significance of neutrino oscillations? [duplicate]

I read some about netrino oscillations and flavour changing between three types of neutrinos. The question is, what is the significance of that observation? So far, we did not expect them to oscillate ...
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3answers
80 views

Detectable interactions in Cherenkov detectors

What are the possible (and at least somewhat probable) particle interactions that could leave a signal in a cherenkov detector (such as super-k)? One source suggested there would be inverse beta ...
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28 views

What is a “cut” in the Hanbury-Brown and Twiss (HBT) method?

I am currently working on p-p collisions simulations using PYTHIA 6. I am using a Monte Carlo approach, but I have done mass reconstructions in the past using something very similar to the ...
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152 views

What is the mechanism of particle anti-particle annihilation

My question is loaded with assumptions so to minimize them, I would like to ask it with respect to an electron and anti-electron annihilating. When I think of annihilation, I think of electron and ...
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22 views

CMS magnetic field outside

The magnetic field at CMS is often given as 4 T. According to this picture the field outside the solenoid is just 2 T. Is this just because the field of a solenoid is not constant and decreases with ...
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What is “forward peaking”?

In "Research and Development for a Gadolinium Doped Water Cherenkov Detector" the phrase "forward peaking" is used to describe a signal. This comes up in lots of other contexts too, but I still can't ...