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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How can I understand Anderson's work “More Is Different”?

Recently, I am reading P. W. Anderson's famous paper "More is different". I know it is a masterpiece, and many people have their thinking on it. Is there anyone can tell me something about it? ...
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1answer
112 views

Why do we ignore rotational energy in monatomic gases?

I understand that the average energy of each degree of freedom in a thermodynamic system is $\frac12kT$. And so, for an ideal monatomic gas, there are three degrees of freedom associated with the ...
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30 views

Is there any absolute reality in our Universe [on hold]

Everything in the Universe is different for everything. So nothing is absolute real. Hence my question, is there any absolute real things in our universe?
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54 views

What are these arcs in bubble chamber photos?

In photos such as this one, or this one (too large to fit inside post), what are the highly frenzied arcs that are really prominent in these photos? Are they simply physical walls in/of the ...
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15 views

Sub atomic interactions between Photons and TI nuclei [on hold]

What are the possible interactions between photons fired thru a sapphire medium at TI amplifiers containing TI nuclei ?
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1answer
32 views

Preventing Heat Escape

Is is possible to completely prevent heat from escaping from a closed container? Here is a diagram of vacuum flask, which tries to implement the design - Vacuum Flask prevents heat from escaping ...
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18 views

Fun physics book for high school student [duplicate]

can anyone recommend me a physics book for a highschool student (not these typical school books) a book that will let you think mostly interested in theoretical /quantum physics done with the ...
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0answers
16 views

Origin and motivation of various flavor symmetries in the neutrino sector

Flavor symmetries of various kinds (for example, $\mu-\tau$ permutation symmetry, or the scaling symmetry, or $S_3$ symmetry) are sometimes assumed between neutrino flavours to "reproduce" the ...
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1answer
33 views

Energy of a system if the nuclear repulsion increases

I have calculated the optimised geometry for a molecule. I have noticed that the energy of the nuclear repulsion increases with each iteration of optimisation. What is the logic behind this?
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2answers
35 views

How is mass conserved when a muon decays?

A small disclaimer: I am a layperson and not a formal student of physics so forgive any glaring stupidity betrayed in the nature of the question. A muon is supposed to always decay into an electron ...
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1answer
50 views

Trying to derive compton scattering using 4-vectors [closed]

I'm trying to derive the energy of a photon after compton scattering: $$ E_\gamma' = \frac{E_\gamma}{1 + \frac{E_\gamma}{m_ec^2} (1-\cos \theta)}$$ where $E_\gamma'$ is the photon energy after ...
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1answer
46 views

meaning of Higgs coupling is flavor conserving

I have heard the statement that the Higgs coupling is flavor conserving. What does it mean? What kind of coupling would be flavor non-conserving?
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1answer
45 views

Why is cut-off regularization is not Lorentz invariant?

Why is it said that the cut-off regularization is not a Lorentz invariant regularization method?
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1answer
51 views

Rest Mass and Wigner's Classification

I believe (but please correct me if I'm wrong) that I understand the basic philosophy and most of the mathematics involved in Wigner's classification of particles via group representations. But I'm ...
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1answer
372 views

Pair production by collision

Electron Positron pairs can be created via three process: Photon-Photon interaction Photon-Particle interaction Particle-Particle interaction I want to know how 2. and 3. can create electron - ...
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1answer
48 views

What's the significance of neutrino oscillations? [duplicate]

I read some about netrino oscillations and flavour changing between three types of neutrinos. The question is, what is the significance of that observation? So far, we did not expect them to oscillate ...
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3answers
80 views

Detectable interactions in Cherenkov detectors

What are the possible (and at least somewhat probable) particle interactions that could leave a signal in a cherenkov detector (such as super-k)? One source suggested there would be inverse beta ...
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0answers
22 views

What is a “cut” in the Hanbury-Brown and Twiss (HBT) method?

I am currently working on p-p collisions simulations using PYTHIA 6. I am using a Monte Carlo approach, but I have done mass reconstructions in the past using something very similar to the ...
2
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2answers
125 views

What is the mechanism of particle anti-particle annihilation

My question is loaded with assumptions so to minimize them, I would like to ask it with respect to an electron and anti-electron annihilating. When I think of annihilation, I think of electron and ...
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0answers
13 views

CMS magnetic field outside

The magnetic field at CMS is often given as 4 T. According to this picture the field outside the solenoid is just 2 T. Is this just because the field of a solenoid is not constant and decreases with ...
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1answer
35 views

What is “forward peaking”?

In "Research and Development for a Gadolinium Doped Water Cherenkov Detector" the phrase "forward peaking" is used to describe a signal. This comes up in lots of other contexts too, but I still can't ...
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51 views

Is hidden symmetry the same concept as broken symmetry for the standard model?

I have recently started studying the basic ideas of symmetry and group representation in order to understand the basic principles behind the standard model. I do follow the difference between a global ...
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0answers
42 views

Compared to the rest in Baryon Octet, why is neutron decay lifetime so long? [duplicate]

Compared to the other particles in the baryon octet, neutron decays with a lifetime of about $900s$, compared to $10^{-10}s$ for the rest. Why the discrepancy? Is it because when the neutron decays to ...
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1answer
90 views

Total number of photons per unit volume in a box (extremely confusing)

This is a worked example from a text. a) Find an expression for the number of photons per unit volume with energies between $E$ and $E+dE$ in a cavity at temperature $T$. $$n(E)dE = g(E)f(E)dE = ...
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41 views

How to derive the Gamow factor in the simplest way?

I want to know how to derive the Gamow factor (how to solve the integral and which approximation I have to do) without the centrifugal correction. $$V(r) = V_N(r)+V_c(r). $$ The Gamow factor is ...
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1answer
73 views

Why is the energy spectrum of alpha decay discrete?

Are the other peaks with lower energy caused by the possibility that daughter nuclei have to be in excited states?as show in this link (count versus energy)
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1answer
57 views

Strong force between quarks that are out of causal contact

This is a rather artificial scenario, but it has been bugging me lately. Background Due to the confinement in QCD, quarks are bound in color-neutral configurations. Any attempt to separate a quark ...
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2answers
100 views

Why is a photon its own anti-photon?

Two properties of a photon that I have considered in trying to answer this myself : Photons are electrically neutral, so there is no need for "anti-photons" to preserve conservation of charge. Take ...
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2answers
152 views

Has a phonon, a formal quasi-particle, ever been observed as a point particle?

Phonons are a nice tool to simplify the quantum-mechanical description of lattice vibrations by identifying the ladder operator of normal modes as creation operators of a certain quasi-particle. In ...
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14 views

At what energy would contributions from EM decay equal weak decay?

Calculate the ratio $R = \frac{\sigma_{had}}{\sigma_{\mu+\mu-}}$ for energies around $10GeV$. At sufficiently high energies, the $e^+e^- \rightarrow \mu^+ \mu^-$ reaction can proceed via the $Z^0$ ...
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1answer
42 views

Why is the phi meson decay width much smaller than rho meson?

Decay widths for $\rho$ meson is $149 MeV$ while for the $\phi$ meson it is $4MeV$. Why is there such a difference? I know that the phi meson decays primarily to $K \bar K$ states as the $\pi^+ \pi^- ...
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39 views

Light Photons 101

How are photons emitted from for example a heated metal. Are they smaller than electrons, do they collide with electrons or can you even say microwaves are made of photons. Don't really understand it ...
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1answer
36 views

Experimental evidence of two neutrinos in muon decay?

We know that the pion decays into a lepton/neutrino pair while the muon decays into a muon neutrino, electron and electron neutrino. How do we distinguish them experimentally? Would the muon decay ...
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10 views

How to draw Feynman Rule and parton process [migrated]

How to draw Feynman Rule and parton process as picture in latex ?
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3answers
98 views

Elementary particles that make up an atom

How many real elementary particles (not hypothetical) make up an atom or can be in an atom?
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37 views

Total cross section of particle decay

Suppose a particle A travelling along the $z$-axis and decays into particles B and C. The cross section is given by $$\frac{d\sigma}{d\cos\theta^*} = k(1+\cos\theta^*)^2$$ where $k$ is a constant ...
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1answer
39 views

why are tau-jets narrower compared to quark-jets?

I read in a thesis (no online link provided) that tau-jets result in a narrower cone in comparison with the other quark/gluon originated jets. I don't understand this. Is this true? If so, why?
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1answer
36 views

what does interference between two decays amplitudes mean?

can anyone explain to me what does interference between two decay amplitudes mean? I'm reading about the GLW and ADS methods used to extract the CKM angle gamma they are both based on the interference ...
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1answer
64 views

Decay channels of the Higgs Boson in Large Hadron Collider particle production

I attach a diagram of 4 of the (many) possible decay channels produced by the Higgs boson, and I have read that 57 % of the time, we find a bottom quark, antibottom quark pair resulting from this ...
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2answers
237 views

What is the essential difference between a resonance and a particle?

Let me start by explaining my particle physics background is very patchy, so this question may not be as coherent as I would like it to be. In general terms, what is the difference between a ...
3
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0answers
55 views

Large Hadron Collider 2015 upgrade, what can it show us?

I realise that the initial answer to my question that may come to mind is, "we don't know yet, duh!!" But my question is hopefully not opinion based. To be specific, have we now a greater chance of ...
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8 views

How does impulse lose energy in rotation, forward and striking earth?

I have this kind of empirical signal in Electronics. where the electronics simulate events signal in rotation signal going forward and signal hitting the earth. The area of the signal is ...
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31 views

What does conservation of strangeness imply for the nature of interaction?

If the conservation of strangeness holds for a decay, then the possible interactions are Strong, Electromagnetic and Weak. But how does one determine which one is it, out of the three?
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35 views

Why doesn't the decay mode of negative omega conserve rest mass?

There are 3 modes of decay via which a $$\Omega ^{-}$$ particle can decay This is one of the decay: $$\Omega ^{-} \rightarrow \Xi ^{0} + \pi^{-}$$ Baryon number is conserved. Strangeness number is ...
3
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1answer
81 views

How do black hole jets form? [duplicate]

A black hole, neutron star or any object that has accumulated an accretion disc, sometimes features opposing jets, positioned perpendicular to the accretion disc. I understand that these jets are ...
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52 views

Implications of dark matter imprints on Cosmic Microwave Background Radiation?

Looking at this link, CMB Anisotropy, I have two questions regarding the possible creation and properties of dark matter: If dark matter has left it's imprint on the CMB, that to me, would imply ...
2
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2answers
52 views

Spectral function with negative value

How does one understand a negative value in the spectral function $$\chi=-\mathrm{Im(G)}$$ where $G$ is the Green function and $\chi$ is a spectral function?
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1answer
38 views

Role of quark color with respect to exclusion principle

From Wikipedia's article on color charge: "Shortly after the existence of quarks was first proposed in 1964, Oscar W. Greenberg introduced the notion of color charge to explain how quarks could ...
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1answer
11 views

Do Two-wire Full Duplex Data Signal Cause Collison at atomic Level

Can the transmitting and receiving signal travel in the same wire in Full Duplex (FDD)? If yes, will there be any collision at atomic level? If yes, how this phenomena can be explained?
2
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1answer
372 views

Is there a significant possibility of the LHC missing “exotic” particles or events?

In his popsci book, "Particle at the end of the universe", Sean Carroll says that the LHC, due to it's sheer information gathering capability, necessarily needs to completely discard most of the data ...