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)

1
vote
1answer
66 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
37 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
47 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
187 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
9 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 ...
5
votes
0answers
73 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} ...
1
vote
2answers
92 views

Are fundamental particles just a trajectory in spacetime? [closed]

Long time ago Wheeler proposed an idea that there is only one electron, some kind of a closed(?) four dimensional knot in spacetime, and in one particular time we slice this knot with a plane and ...
1
vote
0answers
85 views

Finding the final velocity of an accelerated proton using its kinetic energy? [closed]

So. I'm trying to find the final velocity of a proton that is being accelerated by a particle accelerator, just before it collides with a particle. All I have is its kinetic energy just before ...
0
votes
1answer
63 views

Are Neutrons and anti-Neutrons attracted to each other over distance?

Lets create a scenario where you have a total vacuum and you're shooting into this vacuum two streams, one, a Neutron stream and the other an anti-Neutron stream and because you're curious what will ...
2
votes
1answer
81 views

Explicit derivation of the Feynman amplitude of $e^+e^-\rightarrow\mu^+\mu^-$

I'm trying to compute the Feynman amplitude of the process $$ e^+(p_1,s_1)e^-(p_2,s_2)\rightarrow \mu^+(q_1,r_1)\mu^-(q_2,r_2), $$ considering as interaction Lagrangian $$ ...
10
votes
1answer
1k views

How can we speak use the notion of “particle” in LHC, given that we live in a curved spacetime?

I understood from lectures that the metric of a spacetime was absolute: It does not depend upon the test charge we put inside. Indeed, all the calculation our professor carried out were independent of ...
0
votes
1answer
107 views

Effects of massive magnetic field generated by operation of the large hadron collider?

I read an article about the CERN large hadron collider in which it talks about the magnetic field that is generated while the LHC is operating. A magnetic field more than 100,000 times more powerful ...
29
votes
1answer
1k views

How close does a particle-antiparticle pair need to be for annihilation to happen?

I've most often seen the statement that the annihilation of a particle and its antiparticle occurs when they 'collide' with one another. So in other words when they get very close to one another ...
2
votes
2answers
74 views

Measurement on a particle described by a quantum superposition of quark states

Some particles are described as a quantum superposition of quark states. For example, the pion meson: $$ |\pi^0⟩=\frac{|u\bar u⟩−|d \bar d⟩}{\sqrt{2}} $$ Is it possible to design an experiment giving ...
3
votes
1answer
77 views

How are the two proton beams at the LHC accelerated in opposite directions?

At the Large Hadron Collider (LHC), how are the protons in the two beams accelerated in opposite directions?
1
vote
1answer
56 views

Temperature of a trapped particle

How is the temperature of the center of mass of a trapped particle (e.g. in a Paul or Penning trap with laser cooling) defined? I assume it has something to do with the equipartition theorem and ...
1
vote
1answer
102 views

Branching fraction for Kaon decay

I'm attempting to calculate the branching fraction of a particular Kaon decay, namley $K^{+}\rightarrow{\pi^{+}\pi^{0}}$. I know what the branching fraction equation is, namely: $$ ...
0
votes
1answer
116 views

4-Momentum conservation for particle annihilation

Disclaimer: this is a homework question, so I am happy with just a hint or the expressions needed to proceed with my understanding. I am working on the momentum conservation of a ...
0
votes
0answers
20 views

What Happens When 2 particles Touch [duplicate]

Lets take two uncharged particles namely A and B . If these two particles touch each other what are the energy changes that could occur on both the particles. Also when the process of Touching is ...
2
votes
0answers
82 views

Is there any additional complexity in the physical laws that seems unnecessary for us to exist? [closed]

I am wondering if the universe is as simple as possible, at least given the constraint that humans exist on Earth. This is my second attempt at this question, which was marked as too broad, since I ...
1
vote
1answer
34 views

What is happening from electro-magnetic point of view when a proton and an anti-proton annihilate?

Purely electro-magnetically before a proton (+) and an anti-proton (-) annihilate each other /assume they do/, they form a dipole. What happens after that? In other words, what does an external ...
1
vote
3answers
186 views

How many electrons are there – quantum-wise?

If you consider that a particle exists as a quantum field, could you say that all the particles' fields combine into one field for that particle type? Why could you then not say there is no specific ...
0
votes
0answers
55 views

Probe the nucleus by using high energy particles

Why alpha particles would give better resolution than protons moving at the same speed? Can it be explained by Heisenberg uncertainty?
2
votes
2answers
84 views

Limitations of particle in cell method for high desnity plasma

Are there any limitations of particle in cell (PIC) method for high density plasma? To be more specific, is modelling of a narrow channel of high density plasma possible or are there any limitations ...
1
vote
0answers
40 views

What is the current theory underlying the concept of fields? [duplicate]

When I went to school I was specifically told that fields are material (they occupy some region in space, and they "exist" there) and continuous. Recently, studying quantum physics I came across the ...
-1
votes
1answer
53 views

Why do bosons and fermions exist? [duplicate]

if i have two particles in states: |1> and |2> respectavly , and they are not identical then the combined state is |1>|2> , but if they are identical then the labels 1 or 2 are arbitrary and could be ...
2
votes
1answer
137 views

What is a Lagrangian of a photon? [duplicate]

In sense of classical mechanics+special relativity what is lagrangian of a photon? Lagrangian of a relativistic massive particle is as follows: $$ L_{massive}= -mc\sqrt{c^2-v^2} $$ So is it a zero?
1
vote
1answer
55 views

How was there an extra particle in the early universe?

According to theories.. In the early universe.. There were particles and anti-particles in equal number.. But there seems to be one extra particle against the number of anti-particles.. As the ...
1
vote
1answer
91 views

Would it be safe to say that mass is kind of a property of energy?

In a video i just saw about the true meaning of E=mc2, it said something that really got me thinking; "Mass is not really converted to energy" and that mass wasn't actually a thing, but more of a ...
1
vote
3answers
141 views

New particles found using the LHC

After finding the Higgs boson in 2012, CERN. What did the CERN found recently using the large Hadron Collider?
0
votes
1answer
17 views

Phosphorus particle experiment

Has anyone ever done an experiment using phosphorus light in complete darkness and in a vacuum to see position and speed of a particle? If casting light on the particles to measure them and know their ...
3
votes
1answer
128 views

Quark mixing vs neutrino mixing, mass eigenstates, weak states and detection

I have some doubts regarding the CKM matrix in the quark sector and PMNS matrix in the leptonic sector. Let us call $(d^\prime, s^\prime, b^\prime)$ the weak basis for quarks and $(d,s,b)$ the mass ...
1
vote
1answer
81 views

Is there a $\mathrm{p}^0$ particle?

In the following equation of a reaction $$\mathrm{p}^0 + \mathrm{n} \to \mathrm{K}^+ + \Sigma^-$$ What is the quark composition of the $\mathrm{p}^0$ particle? Or is it supposed to be $\rho^0$? ...
0
votes
1answer
77 views

Can a magnetic or electric field deflect subatomic particles?

I always wondered if the subatomic particles can be deflected by a magnetic or electric field. Basically I am asking the viability of the typical "Force Field" in movies.
1
vote
1answer
33 views

How the number of binary collisions increases with centrality faster than the number of participant in heavy ion collisions?

How the number of binary collisions increases with centrality faster than the number of participant in heavy ion collisions at different particle colliders?
0
votes
0answers
28 views

quantum two particle system? [duplicate]

according to wiki if you have two different particle with state vectors |1> and |2> respectively than the state vectors of the combined system is the tensor product denoted: |1>|2> but if the two ...
2
votes
1answer
205 views

Understanding Kaon Mixing

While studying Neutral-Kaon mixing, I learnt that the way we observe them is through their decays to Pions. But the states that decay are not the particles/antiparticles themselves but their mixture. ...
3
votes
2answers
1k views

How does a neutron have more mass than a hydrogen atom's isotope (Specifically deuterium)? [closed]

A hydrogen atom weighs 1.00794 u ± 0.00001 u. The mass of a neutron is slightly above it, at 1.00866491600(43) u‎. I'm wondering, how does a neutron weigh more than itself plus 2 extra particles, as ...
0
votes
0answers
86 views

What is Quantum fluctuation, and does it break law of conservation of energy?

Please explain what is quantum fluctuation as simple as possible and (according to Wikipedia) how could it break law of conservation of energy ? Wikipedia quote: That means that conservation of ...
0
votes
0answers
40 views

How does positronium work?

I've heard that in positronium, electrons and positrons orbit each other before annihilating one another shortly after. However, I thought that electrons never orbit anything, but instead have a ...