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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87 views

Is the usage of the Fock space a postulate in QFT?

In this question, when I write Fock space, I mean "the direct sum of the symmetric or antisymmetric tensors in the tensor powers of a single-particle Hilbert space H", as it is described by Wikipedia. ...
1
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0answers
91 views

The Mechanism Behind Massless Particles Acting As One Massive Particle

I am reading a historical account of the development of the Higgs Field theory by Sean Carroll. In it, he states that the 1963 paper by Anderson postulated that "the massless Nambu-Goldstone bosons ...
0
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1answer
29 views

How to detect particle resonance with cross section measurement?

During one of the final year under-graduate courses, we had a lab experiment about particle physics. In this experiment we got some data from a detector regarding the electrons in the event. If we ...
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0answers
17 views

Is the bandgap energy at the same level quantasized as other orbits of electrons?

Usually to excite an electron to an 'higher orbit' there has to be an exact quantity of energy of a photon. I don't know hów exact this quantity of photonenergy has to be, but is there a difference ...
2
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1answer
45 views

C-parity violation evidence

I know about the CP-violation experiments from the 60's and the P-violation from the 50's. But, is there a similar experiment which displays (perhaps historically in the same way as the experiements ...
3
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0answers
54 views

Branching ratio for a bound state

Consider the meson $\Upsilon(10860)$. It decays into $B\bar{B}$, $B\bar{B}^*+cc$ and $B^*\bar{B}^*$. The mass of $B$ is $5.28 ~\textrm{ GeV}$ and mass of $B^*$ is $5.33~\textrm{ GeV}$. The branching ...
1
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1answer
73 views

Understanding type of force interaction in particle decays

Are there any fundamental rules of thumbs that can be used to identify the type of force interaction (weak, electromagnetic, strong) in a particle decay without drawing the Feynman diagrams at the ...
2
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1answer
46 views

Stopping power of charged particles in matter

So I have this diagram of how the stopping power of muons changes with energy: Depending on energy different equations are used to describe the stopping power variation. Now, currently I'm reading ...
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0answers
25 views

how spin of a particle can be measured from the angular distribution of its decay products

To measure the spin of Higgs boson the angular distribution of its decay products from the higgs rest mass frame is measured, but how the angular distribution of the decay products of a particle is ...
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0answers
23 views

Diffusion Equation for Particle Hopping with drift

First of all, I haven't studied partial differential equations yet, hence this question might sound silly. I am doing a simulation for particle hopping on a lattice with python. I was said that in ...
3
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1answer
105 views

Proton is made of 3 quarks of each spin 1/2, but the total spin of proton also 1/2, how it is possible?

Proton is made of 3 quarks (UUD) each has a spin of 1/2, so if you follow the constitution the total spin of the proton must be (3/2), but the spin of the proton is still 1/2. How it is possible? But ...
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3answers
203 views

How do we know that an electron “spins”?

As far as I know, you can't necessarily isolate an electron to observe it, you can only observe its effects on other particles due to fields. Moreover, we can't know an electron's exact location or ...
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0answers
34 views

Collins Soper frame

What I understand is when a particle is produced by pp collision at LHC, the transverse momentum of the produced particle depends on the pt of the colliding parton. To minimise the effect of parton's ...
0
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1answer
34 views

How does a hydrogen ion gas cool?

Ok I understand that a hydrogen gas of non-ions at a temperature higher than its surroundings exists with many excited electrons. These electrons, either spontaneously or due to collisions, will ...
0
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0answers
14 views

meaning of ISR and Heavy signal

I was reading a paper on particle physics and came across two undefined terms which are ISR and Heavy signals. I would really appreciate any help explaining what those terms mean. Thank you in advance....
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2answers
23 views

Cinematics; Equation of movement

What's the difference using the fórmulas v=d/t , or a=v/t, instead of equations of motion? I dont get it.
1
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1answer
33 views

Does increasing the energy of a relativistic particle increase thrust?

I know this particular chestnut has been asked before, but I have a specific variation on the theme: Particle accelerator space thrust. Specifically, cyclotrons to generate the thrust. They are ideal ...
2
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0answers
32 views

What is the difference between selection efficiency and acceptance in high energy physics?

Often in papers the product of these two quantities is mentioned, but I'm not sure what exactly they mean separately. My guess would be that one of these is the fraction of the events that you are ...
3
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1answer
37 views

Can anyone please explain the meaning of vector resonances in the scenario of particle physics?

I was reading some material on Particle physics and I came across the sentence: pseudoscalar D and B meson states and the corresponding vector resonances D* and B*. What are vector resonances? ...
2
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1answer
51 views

High $p_T$ and high $Q^2$ in deep inelastic hadronic collisions

When reading about high energy collisions (for example proton-proton collisions at LHC), I always find the relation $Q\sim p_T$, which, for me, is hard to demonstrate. Moreover, I found statements ...
1
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1answer
33 views

Electric Field under Time reversal

We know under time reversal electric field does not change direction. I am doubtful about it. Imagine an electric field parallel to x-axis (in positive x direction) and a charge moving parallel to ...
3
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2answers
79 views

Does the Flavor symmetry forbid $uu\rightarrow cc,ss$?

This question comes from the reading of this paper. They suppose a flavor symmetry group $G_F = U(3)_q\times U(3)_{d} \times U(2)_{d}$ which acts on the three LH quarks $q_L$, three RH quarks $u_R$ ...
1
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1answer
54 views

Angular momentum in annihilation $n\overline{n} \rightarrow \pi^0 \pi^0$

Consider the annihilation of a neutron by an anti-neutron $$ n\overline{n} \rightarrow \pi^0 \pi^0 $$ so that the initial relative angular momentum is zero. Because the spin of neutrons is $1/2$, $J_i$...
0
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1answer
24 views

Meson production not originating from a collision

Does anyone know a process that produces mesons other than through collisions from particle accelerators and cosmic ray experiments? Thanks DaPhys
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0answers
23 views

Yukawa exchange model

For my physics class I have to answer the following question. Why do we need two pion exchange and rho meson exchange , and not just one pion in order to explain the strong interaction. My thought is ...
3
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0answers
18 views

CP violation in B meson system through mixing

Mathematically, $\left|\Gamma_{12}\right|<<\left|M_{12}\right|$ implies $\left|q/p\right|=1$,i.e there is no CP violation due to mixing. Please explain why it happens beyond this mathematical ...
0
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1answer
62 views

If matter cannot be destroyed, does that mean that these particles are created somewhere else after breakdown but in the particles original shape?

In the electron collider, after the breakdown into smaller particles, these particles last for a fraction of a second, and then they disappear. My question is: If matter cannot be destroyed, does ...
3
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0answers
51 views

Derivation of Gell-Mann Okubo relation for mesons

In SU(3) quark model of hadronic structure one assumes that mass splitings between hadrons is due to difference between masses of $s$ quark and $u,d$. This is modeled by perturbation Hamiltonian $$ \...
2
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0answers
27 views

Where do the intrinsic parities of particles come from?

It is known that some particles have negative intrinsic parity - for example pion $\pi$. I was wondering if this parity can be understood. I read somewhere that parity of quarks is defined to be ...
0
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1answer
47 views

Would moving quarks constitute a current?

I know that it would take an almost infinite amount of energy to isolate quarks, but let's say we've gotten past that and we have isolated quarks and put them in motion. Would that be a current since ...
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1answer
63 views

Why do particles moving in circular motion emit em radiation? [duplicate]

For example particles moving in a synchrotron . Which energy of the particle is converted to the energy of the radiation ? What is the relation between this energy and the change in direction of the ...
3
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2answers
104 views

Did people ever thought of accelerating neutrons?

It is shamefully charge-free. But presumably, if we can tune its velocity, a lot of interesting things can be done, right? So, was there any proposal for obtaining high velocity neutrons?
11
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2answers
967 views

What is the color of a group of trillions of electrons, protons, and neutrons

Since an electron is smaller than visible light, then what what color would a group of electrons (trillions of electrons) be if there were enough of them to be seen by the eye? What color would a ...
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1answer
49 views

How do comparatively larger particles arise from vibrations of infinitely smaller strings?

In String Theory, how can a string as infinitesimally small as the Planck length, manifest itself as a much larger and massive particle?
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26 views

Scanning Electron Microscopy on a smaller scale

Is it possible to sufficiently focus a ~1nm beam of electrons into a sample chamber in less than 10cm of vertical space, therefore reducing the volume of the entire vacuum chamber, and subsequently ...
2
votes
1answer
42 views

What do the terms “offline” and “online” refer to in the field of high energy physics data analysis?

The title says it - I've encountered these terms several times but have never found an explanation anywhere. An example of use is this ATLAS note. If I may hazard a guess: Data rate is high at the ...
3
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2answers
77 views

Change of flavour, Weak interaction

I couldn't find a straight and clear answer to this question on the internet: Why is the weak interaction (charged), the only interaction which can change the flavours of the quarks?
0
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1answer
43 views

Do Calabi -Yau shapes also influence a strings particle identity?

Since strings reside on the surface of a d-brane, and it' a three dimensional hyperspace, are their manifestations as certain particles also influenced by Calabi Yau Spaces? Could the way strings ...
0
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0answers
25 views

How is the decay width of a resonance is measured?

Last December LHC found an excess in the diphoton channel around 750 GeV. Along with number of excess events and cross section for proton proton -> gamma gamma process, they also provided a width for ...
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1answer
77 views

Should entropy define order rather than disorder? [closed]

Disorder, as I understand it, is basically a measure of entropy. This does not seem correct to me, and appears to be a result of our macroscopic bias. Not only does the beginning of the universe ...
0
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1answer
57 views

How are the standard model and the Higgs boson actually confirmed experimentally in practice?

This is my mental picture on how we can make predictions from a theory (I'm not a physicist so this might be quite wrong) : Typically, we solve a partial differential equation (analytically if we can,...
1
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1answer
66 views

What are quarks made out of? [duplicate]

I want to know what quarks are made out of for a project for my class. It has always confused on what quarks are.
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0answers
21 views

Need a mass to accelerate to create gravitational waves?

For a charged particles which travels through an electric field it only emits photons when it is accelerated. It undergoes a change of momentum, and the law of conservation of momentum requires some ...
1
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1answer
36 views

Can an electron make quadrupole gravitational waves?

A gravitational wave is a quadrupole wave. Now when an electron is accelerated it usually emits a photon. But can an electron also emits an gravitational wave? If so how does it 'make' an quadrupole ...
0
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3answers
103 views

In String Theory, can some particles contains multiple strings? [closed]

According to String Theory, can a particle consist of more than one string? I can visualize elementary particles, like leptons, being composed of a single string. But what about composite particles, ...
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0answers
22 views

Do subatomic particles spin? [duplicate]

What exactly is "spin" of subatomic particles such as electrons and protons? Does it have any physical significance, analogous to the spin of a planet or Mon?
0
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1answer
30 views

How can I determine the interaction knowing the decay formula?

I know the kind of interaction occurring in very common reaction. For example, I know that the interaction: $e^- + e^+ \longrightarrow \mu^+ + \mu^-$ is driven by the electromagnetic force (there is ...
1
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1answer
92 views

What particles are closed strings? [closed]

In String Theory, I understand that gravitons are particles that are closed strings. Are there other particles that are manifested from closed strings?
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2answers
65 views

is curvilinear motion really a type of linear motion?

Let us consider any arbitrary curve except a straight line in the Cartesian coordinates. From the perspective of the particle tracing the curve the motion can only be linear. But from the point of ...
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0answers
30 views

Lagrangian Interaction Type and Spin-Dependence

So I'm transitioning from reading particle physics books to the literature, specifically as it pertains to dark matter models. In this case I'm talking about t-channel DM-nucleon scattering. They ...