Questions tagged [particle-physics]

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.

Filter by
Sorted by
Tagged with
1
vote
0answers
11 views

F-type and D-Type Coupling between meson baryons

What is the basic definition and detailed meaning of the D-type (symmetric) and F-Type (symmetric) coupling between mesons and baryons. Why the name D and F. What is their origin?
-3
votes
1answer
48 views

What caused the particles to move? [on hold]

I wonder how the movement of the particles began? were they always on the move or was there a cause that set them in motion? Could it be that at the beginning of time, all the particles remained ...
1
vote
0answers
48 views

Isospin and $\Delta$ Production

I have seen the relation between cross sections postulated: \begin{align} \sigma(\nu+p\to\mu^- + \Delta^{++})=9\sigma(\nu+n\to\mu^- + \Delta^{+}) \end{align} Motivated by isospin symmetry. I wanted ...
0
votes
0answers
33 views

Particle physics and quantum numbers

Elementary particles contain many quantum numbers which are usually said to be intrinsic to them. If we see a particle that has a same mass, charge and spin of an electron could not be an electron if ...
3
votes
1answer
72 views

How can electrons and quarks be composite?

There are theories suggesting that the electrons and quarks are not elementary particles, but instead are composite particles of two or more yet undiscovered elementary particles. However ...
3
votes
1answer
58 views

Why is color change between quarks without consequence?

As always I will preface this question with the fact that I only have a high school education, so I may be overlooking something, or unaware of something that is inherent to the question. That being ...
1
vote
1answer
77 views

What does color represent in quarks?

Im sure I'm pretty undereducated to be asking a question like this, but what do the colors represent in quark chromodynamics? A I understand it, each color represents a sort of charge, but what kind ...
13
votes
3answers
948 views

Are there any Baryons that have quark-antiquark combinations?

I'll be honest, I only have a Highschool education, so there might be something obvious I'm overlooking. However particle physics is of massive Interest to me. My question is, I know there are ...
3
votes
1answer
60 views

Proton to Neutron conversion

Is there a way to convert a proton in a nucleus to a neutron? Hyperphysics writes that if a proton was supplied with 1.29 MeV of energy, there would be enough energy to make that conversion. Has ...
1
vote
2answers
46 views

Are there scattering targets other than nuclei, protons or electrons in experimental particle physics?

I am not too familiar with particle physics, so maybe I missed something. Typical scattering targets seem to be nuclei, protons, electrons, i.e. stable targets, which of course makes some sense. Have ...
0
votes
1answer
29 views

Caculating masses of unstable particles

I learned that if an unstable particle $A$ decays to $N$ particles $i=1,2,3..N$ in the final state, i.e. $$A \rightarrow 1 +2+...N,$$ then the invariant mass W of the final state particles is given by ...
2
votes
0answers
54 views

How is a T-violation inherited in a QFT?

CP violation In quantum field theory (QFT), ${\rm CP}$ symmetry or ${\rm CP}$ violation is a property of the Lagrangian. For a ${\rm CP}$ violating QFT, in general, the absolute square of the Feynman ...
0
votes
1answer
50 views

Does the air conduct electricity?

If the air is compressed at high pressure in a container, then the volume of the air is less, therefore the air molecules are close to each other. If electricity is passed through the container, do ...
2
votes
3answers
76 views

How does an electron in the same shell of an atom have same energy despite of having different magnitudes of orbital angular momentum?

For example, consider the $n=2$ shell. This will have $l=0,1$ values, so correspondingly there are 2 angular momentum states having magnitude $0$ and $\sqrt{2}\frac{h}{2\pi}$. So how do these 2 ...
2
votes
0answers
43 views

Are all bound states entangled?

In QM, a bound state is a special state of a particle subject to ta potential such that the particle tends to remain localized in space. The potential may be external or it may be the result ...
0
votes
1answer
47 views

Has it ever been possible to measure the fluxes of $\nu_e$, $\nu_\mu$ and $\nu_\tau$ separately?

This is a follow-up of the question asked here. After going through the Wikipedia page on SNO experiment, I need further clarifications about the accepted answer here. First, the SNO experiment ...
1
vote
2answers
37 views

When do we call a composite particle system bound?

I know that to see if a system (for example, a nucleus) is a boson, we see the total spin on it. For example, an even number of protons and neutrons would make the system a composite boson. The same ...
0
votes
0answers
21 views

Heat and ionization energy loss for a nucleus

What are the energy loss magnitudes for heat and ionization? I’m interested for an argon nucleus in liquid argon with a kinetic energy of 1-100keV. There are others relevant energy loss mechanisms at ...
0
votes
1answer
32 views

Does it mean time reverses if all particles were antiparticles and vice versa?

First of all, I'm not major in physics and the question might seems stupid, as I'm layman studying for my self-interest and I really don't know much about it. I only think it might open some ...
0
votes
0answers
31 views

Explain why we have 1/m* at various location in the first and second Brillouin zones (1/m*>0, 1/m*0, 1/m*<0 and 1/m*1/m) [closed]

Explain why we have 1/m* at various location in the first and second Brillouin zones (1/m*>0, 1/m*0, 1/m*<0 and 1/m*1/m)
0
votes
0answers
32 views

I need hints on getting started with this Elementary Particles Problem involving their Wavelengths [closed]

the problem is: Elemental particles A and elementary particles B were accelerated in a vacuum with the same (in absolute value) voltage of $V=228 kV$. The mass of particle $A$ is $55$ times the ...
0
votes
0answers
13 views

Proton and Antiproton decaying into positive and negative pions [duplicate]

A proton and an antiproton annihilate at rest (or in a $p\bar{p}$ atom in an S state) into pions. Show that the decay into a $\pi^+\pi^-$ final state is possible from a $^3S_1$ state, but not from a $...
1
vote
0answers
78 views

A proton and antiproton annihilate at rest into pions

I'm having a difficult time with this particular problem. I'm really hoping for some guidance. A proton and an antiproton annihilate at rest (or in a $p\bar{p}$ atom in an $S$ state) into pions. (a) ...
1
vote
1answer
47 views

Resolution between off-shell and on-shell views of particle interactions in popular writing

This question is based on this blog post 'Is Dark Matter Lurking in Neutron Decays?' and a following comment I re-read recently. It has something I have seen often in popular writing, which I believe ...
13
votes
1answer
334 views

How did we know that the Dirac equation describes the electron but not the proton?

I'm suddenly getting confused on what should be a very simple point. Recall that the $g$-factor of a particle is defined as $$\mu = \frac{ge}{2m} L$$ where $L$ is the spin angular momentum. For any ...
0
votes
0answers
19 views

How to calculate the density of color glass condensate

Color glass condensate is theoretical type of matter that is supposed to exist in the nuclei of relativistic particles. Now, the name itself implies that the material is very dense, but how can we ...
0
votes
1answer
64 views

Would a graviton if it exists have energy?

If it has energy and comes from all matter would then matter lose mass as it releases these gravitons that have energy given that energy and mass can be converted to each other?
1
vote
2answers
42 views

How can increasing the speed and/or mass of a particle reduce, not increase, it's frequency?

In a Physics World article called 'Neutrons on a Lab Bench', from 30 January 2013, it says, '...Yin and Albright calculated that a very intense laser beam should be able to boost the speed of ...
0
votes
2answers
35 views

How to interpret air movement when we breath in terms of fundamental laws of nature?

How to interpret the movement of air in nose in the two parts of breath : inspire and expire in terms of the 4 interactions of nature, gravitational, electromagnetic, weak, strong interactions ?
0
votes
1answer
42 views

What is the point of particle accelerators with lower energies than the LHC?

Brazil's scientists are building a synchrotron, named Sirius. I'm wondering what the point of building this synchrotron is. From Sirius's Wikipedia page, it reaches an electron energy of 3 GeV. This ...
0
votes
0answers
56 views

Mixing matrix in particle physics

It is familiar for us that the diagonalization of a mixing matrix which is written in the neutral basis gives the masses of the neutral particles. If I construct a mixing matrix which is written in ...
0
votes
2answers
54 views

Pauli's exclusion principle in elementary particles

Elementary particles such as Quarks obey Pauli's exclusion principle since they exist in three colors (RBG). Where as electrons which is also elementary that does not have any color quantum numbers ...
0
votes
0answers
30 views

Are electrons in a singlet state still electrons?

Given that some interactions such as electron capture make the electron "disappear" and the output fermion is a neutrino, I wonder what is the rationale behind saying that in the case of two opposite ...
0
votes
3answers
77 views

Experimental proof for isospin conservation of strong interaction

I am having a surprisingly hard time to find direct experimental results for the (approx.) conservation of isospin in strong interactions. The canonical examples seem to be $\omega \! \to 3\pi^0$ and $...
0
votes
0answers
27 views

Jacobian peak in particle physics

The question is related to the derivation of equation (42) in the lecture note of (https://arxiv.org/pdf/1709.04533.pdf). I discussed this with my professor and he seems not interested in such "...
2
votes
1answer
27 views

How to know what production channel Higgs came from?

There are four main production channels for SM Higgs: ggF, VBF, Higgstrahlung and associated top. In multiple occasion I've seen experimental bounds referring to say $\sigma(gg \to H \to \tau^+\tau^-)...
0
votes
0answers
47 views

If the observable universe's mass & energy was converted to white light, how many photons would there be?

Background: The idea is to get a large number that is relatable to humans. The number of atoms in the observable universe is estimated at around 10^80, but this number isn't satisfying as the ...
4
votes
2answers
107 views

According to the Standard Model, were there 4 Higgs bosons at the beginning of the universe, before the electroweak symmetry breaking?

My question is in the context of the Standard Model, not about Beyond Standard Model. At the beginning of the Universe, before electroweak symmetry breaking, we have a complex Higgs isospin doublet. ...
0
votes
0answers
21 views

In particle physics, how should we call a model with several Higgs boson : Higgs multiplet?

In Higgs physics of the Standard Model, there is only one Higgs. The Higgs belong to a Higgs doublet. After electroweak symmmetry breaking, there is only one remaining Higgs, and 3 Goldstone bosons. ...
2
votes
1answer
88 views

Motivation for introducing quantum field theory in particle physics

Why is it so that because particles can be destroyed and recreated we introduce QFT? I read at the begining of some textbook that this is so. My main problem is not the rest of the book but the first ...
0
votes
0answers
36 views

Why there is accelerator chain at LHC?

Why can the LHC not accelerate protons to several TeV in one go? What is the limitation? My Answer: First reason is to minimize the cost of LHC accelerator construction by utilizing the previous ...
0
votes
1answer
60 views

The concept of force carrying photons

Are the force carrying photons really something physical? Do they really occur during electromagnetic interactions? Does this mean that in different mediums where the speed of light differ, the ...
0
votes
0answers
24 views

Total cross section in hadron colliders with optical theorem?

In hadron colliders (like LHC) the total cross-section is calculated using the optical theorem. The origin of this is the scattering of two particles which is solved with the Schrödinger equation ...
1
vote
0answers
44 views

Can we hold atomic hydrogen for a long time? [closed]

If we take atomic hydrogen with similar spin together, can we hold it in balloon? I know, that the atom is hydrogen is reactive. But when all atoms will have similar spin, reactions between them will ...
0
votes
0answers
14 views

Book recommendation for Tree level calculations for decay rates and cross sections?

I know how to do tree level calculations, I just want to copy expressions for Standard model interactions rather than doing them all myself. Is it possible to find them in a table somewhere ?
0
votes
0answers
20 views

Deriving hadrons by their quantum numbers

While preparing for an exam I found a problem where one has to find the composition of hadrons given their quantum numbers. $$\text{ (Charge, Baryon number, Strangeness, Charm, Bottomness)=(Q,B,s,c,b)...
1
vote
1answer
41 views

How does flavor change in weak interaction works with $Z$ and $W^{\pm,0}$?

How does flavor change in weak interaction works with $Z$ and $W^{\pm,0}$? I'm completely confused of how could weak interaction just "approximately" conserve the flavor, but $u,d,s,c$ could be just ...
0
votes
0answers
14 views

Meson decay constants from PDG

I've been looking for data for meson decay constants (pseudoscalar and vector), but in the latest release of PDG review I only find information about these parameters for charged pseudoscalar mesons. ...
1
vote
1answer
24 views

Interference of spin in scattering processes

I am unable to understand how do we determine interference of matrix elements in processes such as positron electron annihilation into muons, i.e. $e^++e^-\rightarrow \mu^++\mu_-$. Let us consider the ...
0
votes
0answers
26 views

Can photon Create gravitational wave when it travel through Space-time? [duplicate]

When big Explosion occurs in space it create gravitational wave. but it is possible that when photon (a packet of energy) make displacement in space-time it also create gravitational wave after all it'...