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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Calculation of removing a nucleon from a nucleus

I would like to calculate the energy needed to remove one nucleon - proton or neutron - from a nucleus. What is the equation to be used?
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4answers
73 views

What would happen if two electrons fuse?

Two electrons repel each other naturally; however, if protons can be forced to fuse, can electrons technically fuse too? What would be the product if two electrons fuse?
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1answer
92 views

How do you build a Lagrangian in particle/nuclear physics? (A specific example)

I know that the terms in the Lagrangian needs to be scalars (with respect to Lorentz symmetry etc.). Also I know that [see C. G. Tully (EPP) p. 85] in general, for $\psi$ in the fundamental ...
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1answer
186 views

Mølller scattering

I came across Mølller scattering today (which is just a fancy name for electron-electron scattering. I'm confused as to why there are two tree level Feynman diagrams for this process: Check out the ...
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1answer
34 views

Is anything without mass an EM wave?

For the longest time I thought the distinction between matter wave and other types of wave is the non-relativist mass of the "thing" under discussion. Photons are EM wave, electrons are matter waves. ...
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1answer
37 views

Would the blue glow of Cherenkov radiation be visible when diffused across ice, such as in the IceCube neutrino experiment?

The blue glow characteristic of Cherenkov radiation is visible emanating from underwater reactors. Is it also visible through ice, at the IceCube neutrino experiment (not that anyone is physically ...
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28 views

Trilinear term in SUSY soft-breaking

In MSSM soft-SUSY breaking, there are such term called 'A-triliear term'. But, some papers, e.g Riva-Biggio-Pomarol, do not have trilinear term. What is the use of introducing trilinear term?
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1answer
33 views

“Double-counting” in particle detectors

Apparently, when analysing events from particle detectors, one may incur in double-counting, which happens when a physics object appears as a single object of its own type, but it may also be ...
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1answer
47 views

What CP violating processes do we know of?

So, after going over my particle physics notes and some introducing literature, it seems the currently known processes we experimentally confirmed to be CP violating are Kaon mixing (an indirect ...
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1answer
24 views

The counting of all possible baryons quark combinations

I would like to ask how do you count the number of possible quark combination that could possibly exist in a baryon. I know certain spin symmetry or orbital momentum symmetry have to be conserved. But ...
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2answers
124 views

Global symmetry and particle multiplets

In chapter 20, of Peskin and Schroeder's quantum field theory book, they start with a comment that a global symmetry that is manifest lead to particle multiplets with restricted interactions. Can ...
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1answer
38 views

What does 'channel' mean?

I see many plots like the following that graph counts per channel, I know what a 'count' is, but I don't know what a 'channel' is. Could somebody please explain to me? My guess is that it is that ...
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80 views

Is the electromagnetic mass real?

In his Lectures on Physics vol II Ch.28-2 Feynman calculates the field momentum of a moving charged sphere with charge $q$, radius $a$ and velocity $\mathbf{v}$. He finds that the total momentum in ...
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2answers
113 views

How are quarks and leptons detected experimentally?

How are quarks and leptons (including subatomic particles) detected in the laboratory,especially when most hadrons and leptons have a lifespan for a considerable small amount of time?Also how do we ...
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75 views

Current knowledge of Higgs

What is the current knowledge about the Higgs field after its discovery in the LHC? Does it exactly mimic the standard model Higgs? Does this knowledge rules out the possibility of other Higgs ...
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1answer
51 views

Isospin of the neutral sigma baryon

I was typing up another answer on P.S.E. and I wanted to use the fact that the decay $$\Sigma^0\longrightarrow\Lambda^0+\gamma$$ does not occur strongly as an example of isospin conservation. But then ...
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1answer
29 views

Sphaleron interactions erase baryon asymmetry?

The sphaleron interactions in the standard model is $(B-L)$ conserving and $(B+L)$ violating. Each sphaleron transition causes $\Delta B$ and $\Delta L$ to change by the same amount so that ...
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1answer
73 views

Do particle decays happen instantly?

For example, let's say a W boson decays into an electron and a neutrino. Is there some transition? Does the boson fade out while the decay products fade into existence? Or does this happen in the ...
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29 views

Why Does Electron Revolve around nucleus? [duplicate]

Actually why does electron revolve around nucleus. Considering Simple atom, hydrogen atom where a single electron revolves around the nucleus. It is said that the electrostatic force of attraction ...
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4k views

If two photons collide, does the resulting particle have zero velocity?

If two photons traveling in opposite directions along the same line collide, will the resulting particle have a velocity of zero relative to the rest of time space in the instant of the collision?
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intuition about Gauge in Hall bar geometry with 4 leads

Please tell me about the kind of gauge I should use for calculating the resistance in a 4 lead hall bar geometry.As when I use Landau gauge it will make my leads transitionally invariant only along ...
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43 views

How to theoretically determine electric charges of $W^{\pm}$ bosons?

I just realised that I don't remember how to conclude theoretically that $W^{\pm}$ bosons have electric charges of $\pm 1$. After some searching I'm quite surprise that I couldn't find a satisfying ...
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1answer
59 views

Baryogenesis via Leptogenesis

Baryon number is directly violated through electroweak anomaly and so does the Lepton number, for each transition from one vacuum to another. The two violations are of equal amount $\Delta B=\Delta ...
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2answers
169 views

Why would electrons have Weak Charge? [closed]

Electrons (and, their cousins Muon and Tau) carry Weak Charge having value $-1/2$. If you believe in Strong Anthrophic Principle Why does electrons carry Weak Charge? If you don't believe in Strong ...
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3answers
53 views

In the Higgs boson experiments, why are protons used?

Why are protons used to create Higgs particles at CERN? Can anyone please explain the concepts very simply? (How to explain this to a layman?)
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1answer
59 views

Could synchrotron radiation be produced by a gravitational field instead of a magnetic field?

I know that synchrotron radiation is produced when a charged particle is accelerated radially by a magnetic field, but I was wondering if synchrotron radiation could also be produced by an uncharged ...
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1answer
47 views

Where does the mass of a nucleon originate in an atom?

The mass of the three quarks in the nucleons make up only about one to two percent of the mass of the nucleons. What makes up the other 98 percent?
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36 views

Summing up independent mass measurements to recover $Z$ boson mass

I am trying to calculate the $Z$ boson mass from a list of $\mu^+\mu^-$ data (momentum). We have been asked to make five blocks of data from the total amount of 10k. Then calculate the mass via ...
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2answers
130 views

How we see laser light if it travels in a straight path? [duplicate]

Light travels in straight path, and our eyes detects an object's reflected light then we see the object. So if laser light is going in a straight path, how come we can see laser light?
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122 views

Where does the electric force come from if an electron has no definite location?

Say electron A is nearby another electron (B), so that they may repel each other. Electron B is in a position eigenstate (so it has a definite position). But electron A is not. How does electron A ...
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1answer
80 views

Number conservation of bosons and fermions

Why is the number of bosons not conserved while the number of fermions is conserved? Does it have something to do with the Pauli exclusion principle?
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2answers
83 views

How to calculate the tree-level probability amplitude for the electron-positron to muon-antimuon process?

Consider the following process: $e^+ + e^- \rightarrow \mu^+ + \mu^-$. I'm trying to calculate the probability amplitude of such a process in leading order. In leading order the amplitude is given ...
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4answers
2k views

How come “smaller, weaker” particles are more massive (have higher energies)?

Something has always struck me as counter-intuitive: when reading about high-energy experiments such as the LHC, they are always looking for stuff on a really small scale with MASSIVE energies. I ...
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1answer
23 views

Eigenstates of total isospin, I

In the book from which I'm studying particle physics (by Mark Thompson) it is stated that states of two quarks of third component of isospin = 0 (like ud or du) are not eigenstates of the total ...
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Could we make things out of newly discovered particles?

Right now, all of the "stuff" that has been created in the world is made of protons, electrons, and neutrons. I'm aware that particles other than these have much shorter lifetimes. But I've also heard ...
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164 views

Can a superpartner be less massive than its SM counterpart?

Theoretically, can a superpartner be less massive than its standard model counterpart? I realize there are experimental constraints.
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18 views

Introducing inert superfield in R-symmetry model in extended MSSM

Some papers, e.g, Chakraborty et al, Frugiuele and Gregoire introduce inert superfield doublet $\hat{R}_d$ and $\hat{R}_u$. I have a question, what is the role of these inert superfields?
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1answer
35 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
29 views

Stopping power diagram

I'm currently looking at this figure, but I'm not sure how to interpret it. If I'm not mistaken, the energy loss of the muon (This is a muon that penetrates copper) is on the y-axis. But does that ...
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3answers
78 views

Can “particle” waves break as ocean waves do?

I have heard about electrons surfing on wake fields which got me thinking. Are there analogs to reefs for these waves and can these waves break as ocean waves do when they hit a reef?
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1answer
53 views

SU(3) antiquark triplet transformation

I'm reading a rather elementary particle physics text, Modern Particle Physics by Thomson. He is staying away from the heavy group theoretic stuff. He derives the transformation law for an SU(2) ...
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1answer
68 views

Charged current vs. neutral current neutrino interactions

I am doing research related to the detection potential of neutrino detectors and, in looking up the various neutrino interaction channels that exist in each detector, I have found the interactions ...
3
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1answer
87 views

Why Majorana phases cannot be removed?

Why is the extra two Majorana phases in the PMNS matrix cannot be removed if neutrinos are Majorana fermions? Or in other words, why are the Majorana phases cannot be absorbed into the redefinition of ...
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20 views

How to calculate U-spin for baryons

I am trying to calculate U-spin for sigma baryons. I don't know why U-spin for (sigma+) and (sigma-) and (sigma*+) is 1/2 but for (sigma*-) is 3/2? I know that (sigma+) and (sigma-) are octet and ...
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0answers
52 views

If tachyons were real, where would they originate from? [closed]

If the hypothetical tachyon existed, where would it possibly originate from? or is this question off the realms within the current state of physics. Also what are some ways physicist have tried to ...
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1answer
74 views

What happens when an atom absorb electron/photon?

I'll give you a scenario or two, and please tell me what will happen and that shall answer my question. Thanks in advance. Scenario 1: Will an atom absorb an electron with kinetic energy greater ...
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Why cross section of $e^+ e^- \to \bar{q} q$ is 3 times larger than $e^+ e^- \to \mu^+ \mu^-$?

I know the usual answer: quarks carry color charge (let us denote them r,g,b), antiquarks anti color charge, and since the initial state ($e^+ e^-$) does not carry any color charge (and color is ...
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1answer
50 views

Soft-Supersymmetry Mass (Direct contact term)

I found this term/operator in some papers that can generate masses, e.g Riva-Biggio-Pomarol(2012), Fox-Nelson-Weiner $\int d^4\theta \frac{X^\dagger X}{M^2}Q^\dagger Q$ Could anyone explain about ...
3
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64 views

Field Lagrangian <--> Particle Lagrangian

The action-functionals describing the motion $\mathbf{x}:[a,b]\to \mathbb{R}^3$ of a free particle of mass $m$ and the evolution $\varphi:[a,b]\times \Omega\to \mathbb{R}$ of a free scalar field of ...
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1answer
101 views

String Theory: Why should(n't) the string snap?

My question is related to a comment in the margin of the popularising site The Official String Theory Web Site. There are two basic types of string theories: those with closed string loops that ...