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.

learn more… | top users | synonyms (2)

0
votes
0answers
27 views

Does matter shrink due to energy radiation and does it have anything to do with dark matter and dark energy?

Is matter shrinking? Is shrinking the cause of concentrated dark matter that makes up matter moving from concentration to unconcentration. Does dark energy and expansion of the universe come from this ...
1
vote
1answer
48 views

Fire, catch and fire a particle

To be more specific, would it be possible to perform the stern Gerlach experiment on a single electron multiple times provided that none of the electrons paths were blocked.
0
votes
0answers
12 views

References on particle cooling

I am looking for references on the topic of particle and mechanical oscillators cooling, in particular: Doppler cooling Resolved sideband cooling and Lamb-Dicke regime Stokes and anti-stokes modes ...
7
votes
0answers
104 views

Real world applications of post-1950s High Energy Physics [closed]

Imagine a world where people knew everything we know today except for high energy physics, where their knowledge ends at our ~1950s level. Is there any real world application, any particular piece of ...
2
votes
0answers
79 views

how to analyze the collision of two photons with four-momentum vector? [closed]

Q: If two photons with energies $E_1$ and $E_2$ collide, with their trajectories making an angle $\theta$. Is the following right about individual initial 4-momentums and total initial 4-momentum? and ...
2
votes
1answer
61 views

Particles, quasiparticles, and “stability”?

So I'm studying Fermi Liquid Theory, which concerns itself with quasiparticle excitations made by superpositions of single-electron wavefunctions. We create particle-like wavepackets which exist for ...
2
votes
1answer
30 views

Positive free particle Dirac equation

I've been set the task of showing that: $$ \bar{\psi^{s}}\psi^{s}=2m $$ For s=0,1. Where: $$ \psi^{0,1}=\sqrt{|E|+m}\begin{pmatrix}\chi^{0,1}\\ ...
4
votes
2answers
64 views

Valence sea quarks parton distribution functions

There's somethin from Thomson (Modern Particle Physics) that I am a little mythed by. Section 8.4.3, eq. 8.3 is given as $$ ...
0
votes
1answer
66 views

colorless charge in a baryon

In a baryon there are 3 quarks and in a meson there are one quark + one anti-quark. So color charge is colorless ( a color singlet state ) in a meson. But how is it colorless in a baryon ?
0
votes
0answers
61 views

How often do quarks annihilate?

How often do quarks annihilate? Quarks bond frequently with quarks, and antiquarks bond frequently with antiquarks. So why do quarks not annihilate antiquarks extremely quickly? More to the point, ...
2
votes
1answer
131 views

$SU(3)$ Tensor Methods in a Tetraquark

I am trying to understand the Georgi chapter of tensor methods in $SU(3)$ representations, and I don't know how to resolve the tensor product of 2 matrices in a 2 heavy quark + 2 light antiquark ...
1
vote
0answers
37 views

Quark axial-vector current in nucleion

In almost all direct detection articles (see for example Jungman, G., Kamionkowski, M. & Griest, K., 1996. Supersymmetric dark matter) I found the following parametrization for the matrix element ...
0
votes
1answer
48 views

How to measure the mass of an uncharged particle like a neutron?

How we can measure the mass of a neutral particles like neutron? To measure the mass of a charge particles like electron we use mass spectroscopy. What about uncharged particles?
0
votes
2answers
71 views

How do we determine total isospin when only third component of isospin is known?

Both $ \frac{1}{\sqrt{2}} (np - pn)$ and $\frac{1}{\sqrt{2}} (np + pn)$ has third component of isospin equal to 0. But the first combination has total isospin equal to 0 while the second combination ...
0
votes
3answers
97 views

FWHM increase with energy (gamma spectra)

Below I have two plots from a gamma spectrum which I've been analyzing. The first plot is between a low energy range, the second between a significantly higher energy range. It is clear that the FWHMs ...
2
votes
2answers
133 views

Has the Higgs boson always existed?

I am slow and need some help understanding this. So has the Higgs boson always existed? If not, than how did it come to exist? What would have excited it before matter or particles were created? So ...
3
votes
0answers
50 views

How does one determine chirality experimentally?

The Standard Model says that only left-handed electrons participate in weak interaction. A very natural question for novices like me is then: How can we tell, experimentally, if an electron is ...
0
votes
1answer
40 views

What is the physical meaning of $\alpha$ in this disintegration problem?

I am taking a course where I have to solve the following problem related to the disintegration of a baryon in a proton and a pion $(\Lambda \to p^+ + \pi^-)$: Assume that a $\Lambda$ particle with ...
0
votes
0answers
12 views

Kinematic equations of a cascading particle decay

This paper discusses different measurable quantities that can be used to search for unknown particles at particle accelartors. For the following decay it introduces the invariant mass $m_{XY}$: It ...
0
votes
1answer
59 views

Particle Physics: Weak Interaction

Consider the following decay equation:- A Kaon(+) decays into a muon(-) and an antineutrino(?) The question is as follows :- State and explain whether the anti-neutrino is an electron, muon or tau ...
0
votes
0answers
3 views

Parametrization of the medium change from solid to gas?

I am thinking the model where the parametrization of GEM (Gas Electron Multiplier) is open. I can reach a high sensitivity in similar systems where the medium is solid such as in solar cells (5 ...
0
votes
1answer
33 views

Charge inducing electric field or electromagnetic fields?

I am thinking the therminology here which is about Gas Electron Multipliers (GEM). There is a continuous flow of the fill gas which is ionized so no particles created/destroyed: #1 By Gauss's ...
0
votes
0answers
42 views

Direct vs indirect detection of dark matter

Background There are two categories of searches for dark matter. Direct Detection via reproducible experiments Indirect detection Detection of e.g. annihilation signal from astrophysical sources ...
0
votes
0answers
51 views

A Magnetic Vortex in a Magnetic Vortex

This is not to scale. Can a magnetic vortex be compressed into a flat disk using magnetic entrapment? Can a magnetic vortex happen inside another magnetic vortex?
0
votes
0answers
38 views

Magnetic field of a circular particle accelerator

Suppose there's a $500 \ GeV$ proton beam ($q=1.6 \times 10^{-19} C$) inside a circular particle accelerator, what would be the magnetic field intensity $B$ in Teslas required to keep it stable at a ...
0
votes
1answer
57 views

Combined function magnet

I am searching how a combined function magnet for accelerator physics works, but on the books that i have and on the web i can find only patents for this thing, that suppose to know already how this ...
0
votes
2answers
113 views

Energy forms of a charged particle in an electric field?

I am thinking an explicit list of all energy forms in a system of charged particle (take electron or proton, for instance). It has at least potential energy and kinetic energy by Newton. ...
1
vote
1answer
103 views

Angular Momentum of a Photon

Why is it that the angular momentum of a photon is $\hbar$, irrespective of its energy? I encountered such a claim in a text about Raman spectroscopy. Is there an explanation for this using basic ...
4
votes
0answers
153 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 ...
0
votes
0answers
25 views

Subnuclear reactions: combining quarks

When you try and pull two quarks apart, you don't get two separate quarks, but instead: the energy stored in the field between them gets high enough to create more quarks, and instead of two ...
0
votes
0answers
61 views

Propagator for fermion fields and Feynman diagrams

I need some help concerning the interpretation of propagators and Feynman diagrams. The free fermion propagator is given by the contraction of two fields $\psi(x),\bar\psi(y)$: ...
0
votes
0answers
15 views

Are GEMs parallel plate capacitors?

I am studying different forms of GEMs (Gas Electron Multiplier) and some literature uses the word parallel plate capacitor (Mansfield, Understanding Physics p. 457). However, I am not sure if this ...
1
vote
0answers
35 views

Why is this decay process allowed? [duplicate]

I have been given an assignment in which I have been asked to list some quantum numbers for some given allowed processes. One of them is $\Delta^+ \rightarrow p^+ + \pi^0$ I know that $\Delta^+$ ...
0
votes
1answer
34 views

momentum conservation in particle-antiparticle creation

It's understood that the PRESENCE of a heavy nucleus is necessary for conservation of linear momentum in pair creation. What I can't understand is why it must occur in ADJACENCY of the nucleus. Is ...
1
vote
1answer
69 views

Angular momentum in baryon multiplets

In the Murray Gell-Mann model, particles are brought together as a function of their angular momentum. The classification diagrams can be seen as irreducible representations of $SU(3)$, following ...
1
vote
0answers
39 views

Sterile neutrino constraints (summary of results)

Constraints on sterile neutrinos come from an amazingly wide range of different sources. From astrophysical observations (review1, review2) to particle physics experiments (MiniBooNE, Daya Bay, LSND, ...
11
votes
3answers
1k views

Why not dilute radioactive waste?

Radioactive wastes are dangerous because unstable elements are too concentrated. Originally radioactive elements come from nature where they were very diluted and that's why they were secure. So why ...
-1
votes
1answer
48 views

Can we produce a wave by oscillating current? [closed]

If Radio waves can be generated by using oscillating current so if we changed the properties of current to produce less wavelengths or light waves - I'm not asking about the possibility of producing ...
1
vote
1answer
214 views

Positron-electron annihilation - can more than two photons be created?

I'm an engineer and been reading about PET scanners and how they rely on the fact that a positron-electron annihilation will cause two photons to be emitted at 180 degrees from each other. After a bit ...
0
votes
0answers
10 views

Electric field strength for constant mobility?

I am reading Knoll about radiation detectors. It says at about page 168 that The mobility $\mu$ is constant with the modest electric fields. I am interested in which ranges of electric fields ...
0
votes
0answers
22 views

Presentation of Electric Field Strength as a function of r; voltage

I am trying to generalize the electric field strength equation as a function of radius from the anode for Gas Electron Multiplier (GEM). I think you can think this as a parallel plate capacitor ...
1
vote
0answers
58 views

Two double slit experiments after each other

Does the act of observation forever destroy a photon or electron's wave like behaviour? What would the result be if the electron was observed, and instead of displaying the two lines or particle like ...
1
vote
1answer
56 views

Fusing Hydrogen with lightning

I've been reading about fusion recently (Specifically Deuterium fusion) and a friend of mine asked me if it was possible to fuse two Deuterium atoms with a lightning strike? Now this question has a ...
1
vote
0answers
26 views

Writing the Interaction Hamiltonian for pions in a different way

$\pi^+$, $\pi^-$ and $\pi^0$ are scalars particles with masses approximately equals. Their interaction is, approximately, given by $H_{int}(x) = g \epsilon^{abe}\epsilon^{cde}(\phi^a\partial_\mu ...
0
votes
1answer
74 views

Can more than one photon be in the same space as another photon?

I have heard light described as a particle that travels in a wave. I have heard that waves are unique in that two waves can take up the same space as they are travelling, either through constructive ...
1
vote
0answers
30 views

What is the role of the hyperfine interaction in singlet-triplet transition of spin correlated radical pairs?

I don't really understand the hyperfine structure. I understand, that the magnetic dipole moment of the nucleus interacts with the spin of an electron, causing a split between the energy levels of ...
0
votes
0answers
11 views

Particle damping at low pressures

I'm looking for references on the topic of particle damping at low pressures, where the interactions are rare enough so that collisions are discrete, and the effective damping has to be integrated in ...
0
votes
1answer
36 views

Modes of a quantum string

It has been said that particle identity relates to vibrational modes of its quantum string. However, I have not seen the identification of a particle related to a specific vibrational mode. At a ...
1
vote
0answers
25 views

How to compute the speed of a cosmic ray from its energy? [duplicate]

How can you compute the speed of a cosmic ray from its type and measured energy? For example, if a cosmic ray were said to be a proton of 10 GeV, how would you compute the velocity of that cosmic ...
6
votes
0answers
77 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} ...