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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Is uniqueness a fundamental property of nature?

The Laws of nature are universally applicable and at every point in force. Together they shape our universe but are all "shapes" unique? For example, is it possible that there is a second identical ...
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1answer
129 views

Excitation energy of carotene using the particle in a box model

I'm practicing for an exam and I came across the following question: The linear, conjugated π-electron system of a carotene molecule comprises 11 atoms and the distance between two atoms is 1.4 Å. ...
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1answer
140 views

Helicity angle of electron in $B^0 \rightarrow K^{*0} \gamma$, with $\gamma \rightarrow e^+ e^-$?

I haven't been able to find the exact definition of a helicity angle, and the ones that I found don't apply to this particular case, because they'd require to boost to the electrons' 4-momentum to the ...
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2answers
49 views

How is one element capable of radiating (almost) every wavelength?

Black bodies are considered as emitting all wavelengths. A incandescent light bulb has (nearly/almost) also the continuous blackbody spectrum near-perfect color rendition. In this bulb is only one ...
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0answers
42 views

Generalisation of a particle in QFT

In classical mechanics, we assumed a particle to have a definite momentum and a definite position. Afterwards, with Quantum mechanics, we gave up the concept of a time-dependend position and momentum, ...
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1answer
179 views

Singlet neutrinos decaying to Higgs bosons during leptogenesis

(i) The Lagrangian of electroweak model extended with right-chiral singlet neutrinos $N_{iR}$ contains the Yukawa coupling term+ the bare Majorana mass term $$f_{\alpha i}\overline{l_{L\alpha}}\hat\...
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2answers
262 views

How it is possible to mediate a weak interactions by very heavy particle such as Boson?

When considering a weak decay interaction such as leptons , the weak force is mediate by huge particle such as bosons (W+ or W- ). How it is possible to have a such heavy particle within less massive ...
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1answer
75 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. ...
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1answer
31 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 ...
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0answers
30 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 ...
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1answer
21 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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50 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 ...
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22 views

What would be the craziest (but still plausible) plan for launching a small payload to the moon? [on hold]

I wonder what would be the cheapest possible (that means cheaper than anything else that's out there already) to "just" launch a small payload (like a ball less than a kilogram) and crash it somewhere ...
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0answers
8 views

How do a boundary layer and velocity affect a gas? [on hold]

In the Field of Mechanical Engineering they talk about velocity And boundary layer. I want to know how do these relate to gases and how they move, do gas molecules every stop moving. Do gas molecules ...
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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 ...
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0answers
25 views

3D wave equation of a 3D object [on hold]

For an example I have to derive wave equation of a sphere, x^2 +y^2 + z^2 = r^2 and its solution (wave function). Boundary condition can be anything. I like to know about eigenvalue and its use at ...
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1answer
63 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
33 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 ...
3
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1answer
97 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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27 views

Is there a scientific centers of support special research? [on hold]

I'm Dr Mustafa , an astrophysics researcher from Egypt I've written a Scientific paper about a possible new fundamental universal force,But it did not publish it yet. Because I want to prove ...
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0answers
21 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 ...
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0answers
45 views

Equal amplitude for the processes P1: u g->W+ d and P2: d g->W- u? [on hold]

My question is the following: We have two processes P1: ug->W+d and P2: dg->W-u. At tree level and in the limit of vanishing quark masses, which is the ratio between the averaged square amplitudes? ...
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3answers
191 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
19 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 ...
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1answer
32 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 ...
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8answers
5k views

Is (rest) mass quantized?

I learned today in class that photons and light are quantized. I also remember that electric charge is quantized as well. I was thinking about these implications, and I was wondering if (rest) mass ...
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1answer
45 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 $1/2$, $J_i$...
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1answer
282 views

Why is there no fundamental force following from the $SU(4)$ symmetry?

I've understood that the three fundamental interactions described by the Standard Model (the electromagnetic, the weak and the strong force) are thought to correspond (roughly) to gauge invariances ...
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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
21 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.
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1answer
26 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 ...
7
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1answer
282 views

effect of a simultaneous local and a global $U(1)$ symmetry breaking

EDIT : I am trying to figure out the effect of symmetry breaking in a $U(1)_Y\times U(1)_Z$ invariant lagrangian where $U(1)_Y$ is local symmetry of the Lagrangian and $U(1)_Z$ is a global symmetry of ...
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2answers
97 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?
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0answers
30 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
35 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
45 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 ...
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5answers
2k views

Do radio waves travel around the Earth or through it?

Whenever you hear someone illustrating/describing the transmission of radio waves they always make it seem like they'd travel perfectly around the Earth to another distant location. For example, a ...
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1answer
61 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 $u_R$ ...
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1answer
31 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 ...
2
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1answer
105 views

how do electrons in 2 separate atoms change its energy level when atoms come close together to form molecule?

The question is just as the title. It's said that electron must receive a specific amount of energy in order to go or drop to another energy level. So how can electrons of separate atoms which have ...
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1answer
21 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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22 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
42 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 $$ \...
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 ...
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1answer
60 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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2answers
70 views

Ambiguity in assigning intrinsic parity

We know that, fermions can have intrinsic parity either $\eta_P=+1$ or $=-1$. How does one then fix the intrinsic parities ofthe elementary particles, uniquely? Again, the intrinsic parity of a baryon ...
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1answer
58 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 ...