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
17 views

When is the spin of an electron changing?

An electron can have a half spin up or down. The up spin can become a down spin to lose his weak charge. But when are electrons changing their spin?
1
vote
2answers
33 views

How to understand that Higgs not implies a circular reasoning?

For what I know about Higgs (boson/field) it gives mass to subatomic particles. When it interacts a lot with the fiels it gets a great mass (like a topquark) and when it interacts a little it gets ...
0
votes
0answers
10 views

Is the magnetic dipole moment in charged particles the more survivable property than the electric charge?

After asking about Which of the properties of particles are intrinsic properties and why? it was commented "Charge, spin, lepton number, baryon number definitely. Mass maybe." and "is magnetic dipole ...
4
votes
1answer
40 views

Fractionally charged Quarks

Just wondering what the evidence is for fractionally charged quarks, is it simply enough to say that as we see deep inelastic scattering of electrons (at high energies) off the nucleus of an atom ...
0
votes
0answers
32 views

If quarks are fundamental, and mass is a form of energy, then can quarks/leptons be pure energy? [on hold]

So, if quarks and leptons are fundamental particles, then could quarks/leptons be pure energy?
1
vote
1answer
29 views

Open Source Particle Tracing Software

I am fairly new to this forum. I am designing an ionospheric plasma testing environment in a thermal vacuum chamber and to do so I require some form of multi-physics package for simulations .. such as ...
0
votes
0answers
27 views

How do I find the co-ordinates and speed of this particle on the x-y plane? [on hold]

I got this question from an old physics exam paper. I'm trying to use the kinematics equations to solve this question but the x and y co-ordinates keep confusing me. Here's the question: A particle ...
0
votes
2answers
25 views

Why is the intensity of an alpha ray constant along a material?

I'm taking a course in radiation physics and I've come across the following problem: A thin beam of alpha particles of intensity $I_0$ and energy $E_0$ impacts in a material. What is the intensity ...
-1
votes
2answers
74 views

Is there a natural source of Antimatter in this universe?

I was just asking if there is an natural source of Antimatter in this universe capable of creating simple molecules/compounds? So, any good answers?
-1
votes
0answers
31 views

Explaining the Atemporal Dimension of Feynman Diagrams

In a Feynman diagram, I understand that one of the dimensions (horizontal, say) represents time. Could someone please rigorously explain why a second dimension (vertical) is necessary? In particular, ...
5
votes
1answer
64 views

Importance of CP violation

To explain the matter-antimatter assymmetry, CP should be violated according to Sakharov conditions. Charge conjugation is required as matter and antimatter have opposite charges but why Parity ...
1
vote
1answer
43 views

Is light relative? [duplicate]

I was wondering, if two cars (A and B) are going at different velocities let's say A=90km/h, B=80km/h then if we add the two speeds we get 170km/h meaning they are relative to each other. But if one ...
0
votes
2answers
51 views

Is the video “How to Reveal Subatomic Particles at Home”'s explanation of its experiment misleading?

https://www.youtube.com/watch?v=wN_DMMQEhfQ The video asserts that along the path of an electron or muon, a trail of condensation will appear. But from what I understand, if an electron or muon (both ...
0
votes
0answers
53 views

Undergraduate Physics Senior Research Topic (Theory/Mathematical Physics Based) [on hold]

This is most likely a question for those who have experience/knowledge of theoretical/mathematical physics at the graduate level and can provide recommendations following my criteria. Here is some ...
0
votes
0answers
25 views

How to determine likelihood of baryon decay

If I want to determine the probability of $\Sigma(1385)^+ \to \Lambda^0 + \pi^+$ how would i do this? I know I have to do something with the $J^P$ value of each part of the decay, but I'm not sure ...
0
votes
0answers
23 views

Decay of lepton into meson and neutrino using four-momentum

I'm learning about how to use four-momentums and am working through a problem involving the decay of a charged lepton into a charged meson and neutrino. The equation would be: $L^+ \to M^+ + \nu$ ...
-1
votes
0answers
38 views

Is mass in the sub-atomic particles caused by their angular momentum? [closed]

When they found the God Particle, they said it's responsible for creating mass in all other particles except photons and neutrinos. But how it creates mass is a mystery to me. My suspicion is that ...
1
vote
2answers
76 views

Shouldn't atoms of the same element repel each other? [on hold]

Shouldn't the same type of atoms repel each other due to electrostatic charge?
1
vote
0answers
40 views

Why neutrinos are weakly interacting? [duplicate]

I recently attended a talk on neutrinos, where the speaker said there are billions of neutrinos passes through our body every second, but in our lifetime the probability of alteast one neutrino ...
4
votes
2answers
118 views

Do physical entities with one dimension equal to 0 exist?

Within mathematics, a lot of entities with one or more size equal to zero exist and are fluently manipulated. For example, within $\mathbb R^4$, the entity defined as $z=0, t=2$ is a plan, the one ...
1
vote
2answers
108 views

What physics does the Super Proton Proton Collider intend to explore in the $\lesssim 100\:\mathrm{TeV}$ range?

Chinese scientists have completed an initial conceptual design of a super giant particle collider which will be bigger and more powerful than any particle accelerator on Earth. With a circumference of ...
0
votes
0answers
33 views

Can we generate artificial electrostatic energy? [closed]

Can we generate artificial electrostatic energy for electrostatic attraction?And can it be controlled to get element specific electrostatic attraction?
-1
votes
0answers
39 views

What will happen if we collide electron with any quark? [closed]

What will happen if we collide electron with any of the quark at very high velocities? Is this collision possible? Edit: for e.g. consider down quark.
1
vote
0answers
34 views

Normalisation of the $\gamma$-matrices

I'm having a little difficulty with understanding the normalisation process of the $\gamma$-matrices. In Thomson Modern Particle Physics 2013, the normalisation of the $\gamma$-matrices are quoted ...
-2
votes
0answers
33 views

Is it possible that Haïm Harari´s rishon theory can solve the explanation of mass in a ``non Higgs`` way? [closed]

In Harari´s rishon theory there are only (less is impossible) really elementary particles, of wich all quarks and leptons and other particles are made of: The V- en de T-rishon. All known particle ...
0
votes
1answer
16 views

What is the best software to simulate the tracks of muons in matter?

What is the best (free) software to simulate the tracks of muons in matter? I have done some simulations using SRIM/TRIM (www.srim.org) by modifying their proton model to have the mass of a muon, but ...
2
votes
1answer
77 views

Photons Disappear and Reappear from Atoms?

Where does photons come from and disappear to? Can photons be destroyed and created? Without atoms would photons exist?
1
vote
1answer
30 views

What is the physical intuition behind the Bragg peak?

The wikipedia page says: Energy lost by charged particles is inversely proportional to the square of their velocity, which explains the peak occurring just before the particle comes to a ...
5
votes
0answers
54 views

If there are long-lived elements in the Island of stability, why are they not present in Nature?

To my understanding, some (but not many) physicists speculate that the Island of stability may contain long-lived elements, as in a billion or so years. But couldn't we rule that out just by the ...
1
vote
0answers
33 views

What are the lowest level properties of matter [closed]

I am not a physicist but I am interested in philosophical implications of theoretical physics. My understanding is that many physical properties like mass, volume, temperature etc. - are emergent ...
3
votes
2answers
93 views

Feynman diagram, which virtual particle?

Hi I have been asked to produce the lowest order Feynman diagram for the following scattering process: $$a.~~~ \mu^-+\mu^-\rightarrow \mu^-+\mu^-$$ $$b.~~~ \mu^-+\mu^+\rightarrow \mu^-+\mu^+$$ The ...
2
votes
0answers
24 views

Energy dependency of the total cross section for different species

Comparing the plots for the total (inelastic) cross sections as a function of the centre of mass energy for $pp$ and $e^+e^-$ collisions: one notes that the trend at high energy is opposite: the ...
0
votes
1answer
29 views

Does the Higgs Field positive value correlate with “giving mass”?

I understand that the Higgs Field has a positive average value, while the average strength of (almost?) all of the other particle fields is zero. Does that positive value relates specifically to the ...
2
votes
0answers
41 views

Effective collision energy at LHC

The proton is not a fundamental particle, so in high energy proton-proton collision we actually collide proton's sub-constituents: quark-quark and (mostly) gluon-gluon. LHC operates now at 13 TeV ...
1
vote
0answers
16 views

Cold dark matter from creation in external gravitational field

Suppose we have massive (pseudo)scalar field action in FRLW spacetime: $$ S = \int d^{4}x\sqrt{-g}\left( \frac{1}{2}\partial_{\mu}\varphi \partial_{\nu}\varphi g^{\mu \nu} - ...
3
votes
1answer
86 views

Could there exist (and if not: why?) non-elementary particles composed of gravitons?

I read about glueballs, which should be particles made purely out of gluons. This is a quite theoretical thing but its existence has at least been theorized. Now, I don't know so much about ...
0
votes
0answers
11 views

Order of the life time of the K± mesons [duplicate]

It is not a homework. I've just wanted to find the order of the life time of the K± mesons. I had some suggestions like Starting from Fermi’s model and dimensional analysis ,Considered decays like K ...
2
votes
0answers
26 views

Open-source code for computing response functions

Summing Feynman diagrams to compute the response functions of a microscopic model is common in many areas of physics. While conceptually straightforward, the task can be computationally intensive. ...
1
vote
1answer
33 views

Showing the annihilation of an electron-positron pair [duplicate]

How to show that the annihilation of an electron-positron pair under emission of one real photon (mass zero) is forbidden by energy-momentum conservation, the emission of two photons is allowed?
1
vote
1answer
40 views

Are the leptons in $\beta^-$ decay already present in the nucleus in some form?

In beta minus decay, beta-minus particle and anti-neutrino are ejected, leaving behind daughter nucleus. $\beta^-$ and anti-neutrino both are leptons. Were the leptons already present in the ...
10
votes
2answers
744 views

Why couldn't the decay $\pi^- \to e^- + \bar\nu_e$ occur if electrons were massless?

If we assume that electrons (just like neutrinos) are massless, why can’t the decay $\pi^- \rightarrow e^- + \bar{\nu}_e$ occur under the weak interaction?
2
votes
0answers
73 views

Is muon muon annihilation already realised?

As muon colliders do not yet exist, has muon-muon annihilation already been realized experimentally?
1
vote
1answer
36 views

Internal energy + energy of electron

Internal energy of a system composed of molecules or atoms is the mean energy of all these particles in the system (energy as kinetic energy, potential energy etc..). But what I am seeing that we are ...
3
votes
1answer
49 views

How do we know that elementary particles possess definite parity?

As I was reading Griffiths' "Introduction to Elementary Particles" Wiley 2008, on chapter 4 "Symmetries", the question stroke me. The same as Parity operator (inversion in 3-dimensional space) we ...
0
votes
1answer
31 views

Does the electromagnetic force “split” at lower than normal energies?

Since we have working models for forces "combining" or being describable via a single framework at higher energies (such as the "electroweak" force and the aim of GUTs), does electromagnetism split ...
4
votes
0answers
72 views

Second order Fermi mechanism. Is there a mistake in the Claus Grupen book?

The second order Fermi mechanism describes the interaction of charged particles with magnetic clouds. This model leads to a collision-less acceleration of cosmic rays up to ultra high energies. A ...
0
votes
0answers
34 views

Obtaining an angular distribution from the Klein-Nishina formula

I'm having trouble on how one might obtain an angular distribution from the Klein-Nishina formula for compton scattering of polarised photons, more specifically on how this report is obtaining it. ...
3
votes
1answer
86 views

Why don't antiparticles have antispin?

Antiparticles are often said to particles moving backwards in time. However if they are moving backwards in time shouldn't they also "spin backwards", meaning they should have negative or antispin? ...
16
votes
3answers
1k views

What is “mass” in particle physics? [duplicate]

It's clear, from reading pop-science articles about the Higgs boson, that particle physicists have something very specific in mind when they say "mass". In classical physics the mass of a particle is ...
3
votes
1answer
76 views

Hierarchy problem and quadratic corrections in the Standard Model

In this paper, the third paragraph of the “Introduction” says that the Standard Model by itself is a natural theory. As I understand, they say there is no quadratic divergence in the Standard Model ...