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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235 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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49 views

How to stop particles from clustering on a water surface

For my experiment I have to obtain a water surface (1 m$^2$) seeded with floating particles. I found particles of the right size, density (and very acceptable price): expanded glass granulate. However,...
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71 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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1k 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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87 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
249 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
284 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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1answer
280 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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52 views

Observer carries beam of light and travels at speed of light

I am more of an "arm-chair" quantum physicists, i.e. I'm interested in books and articles about the subject. In the book "Tao of Physics" (Fritoj Capra) it mentions that when Einstein was 16, he ...
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47 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
108 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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3answers
198 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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2answers
314 views

What was the largest object/particle tunneling observed?

What is a current record? Reference to that would be nice. and what can be expected in near future? what are the theoretical limits?
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60 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
46 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
52 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
100 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
616 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 ...
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115 views

Large Hadron Collider 2015 upgrade, what may we discover?

I realise that the initial answer to my question that may come to mind is, "we don't know yet, obviously" But my question is hopefully not opinion based. For example, does this upgrade have a ...
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0answers
25 views

How does impulse lose energy in rotation?

I have this kind of empirical signal in Electronics where the signal is 1D current measurement (AD current coming from dynamic processes) such that the wire rotates in a big volume of water/mud: ...
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180 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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55 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 ...
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1answer
139 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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1k views

What is the physical interpretation of second quantization?

One way that second quantization is motivated in an introductory text (QFT, Schwartz) is: The general solution to a Lorentz-invariant field equation is an integral over plane waves (Fourier ...
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0answers
97 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 ...
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2answers
96 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
57 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
27 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?
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1answer
403 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 ...
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1answer
158 views

With the LHC about to restart as max energy, are there absolutely no hints or tantalizing signs of Supersymmetry in previous data?

Over the last couple of years I've seen several articles talk about hints or bumps in the data that might point to Supersymmetry. An article in NewScientist from Summer 2012 discussed the discovery of ...
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2answers
63 views

Is there a word for all the particles in an atom?

That is to say, is there a word that picks out protons, neutrons, AND electrons, rather than just saying "nucleons plus electrons"?
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1answer
135 views

What is the value (order of magnitude) of electric charge density of the atom and the nucleus?

The mass density of the nucleus is constant. But what is the electric charge density of the nucleus and the atom (any order of magnitude)?
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69 views

Acceleration of uncharged particles

Following on from this comment - do uncharged particles radiate under acceleration? (no offense to the commenter, just clarifying as I've not heard of this before) Why is this? I vaguely recall a ...
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4answers
234 views

What really is a particle?

In Classical Mechanics we consider particles as things whose internal structure for the purpose of studying some phenomenon might be neglected. In that setting we associate particles to points and ...
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36 views

Can antimatter becomes black hole? [duplicate]

I know it seems unlikely to accumulate sufficient amount of antimatter to let it collapse under its own weight to become a black hole(maybe the gravity works differently I don't know) since they will ...
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2answers
89 views

Can we create heavier particles with high energy?

It is known that an electron and a positron are created from the energy of gamma ray, is it possible to create heavier particles like proton and neutron from the energy of gamma ray? (if so what is ...
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1answer
226 views

What is the typical strength of the electric field in a particle accelerator?

I am working on a research project involving the closed orbits of hydrogen in the presence of an external electric field and I am curious what a reasonable approximation for the electric field ...
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1answer
95 views

Is a matter anti-matter collision comparable to Gamma Ray Burst (GRB) energy output?

Is a matter anti-matter collision (please assume two cosmological objects, neutron star sized say), the largest energy release method known? Would it be comparable in order of magnitude to gamma ray ...
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59 views

Can elementary particles be rightfully considered quasiparticles?

Can elementary particles rightfully considered quasiparticles? I have this association, because renormalization makes particle properties, like mass and couplings, energy-dependent quantities, even in ...
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0answers
47 views

What processes contribute to non-relativistic proton-antiproton collsions (annihilation)

I wonder what the dominant contributions of nuclear interaction to non-relativistic proton-antiproton annihilation are (I mean that the proton and antiproton are non-relativistic. The products might ...
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1answer
61 views

Charged-current: Why does the neutrino interact with the down-quark?

I'm revising for an exam and looking at a few exercises, one of which starts with Consider the charged-current interaction between a muon neutrino with one of the valence quarks of the proton. ...
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1answer
114 views

If the effects of gravity cannot travel faster than the “c”, does this mean we are only gravitationally bound by masses in our observable universe?

I'm 17 and fascinated by the differences and omissions Newton made in his equations of motion. However it makes sense that gravity can't travel faster than light because of the force-carrying photons.....
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1answer
70 views

Electron-Positron Annihilation: How is charge conserved at the verticies?

How is reaction possible? The verticies do not conserve charge. Also, why is the arrow for the positron pointing downwards when as time increases, the positron should move towards its vertex? Sorry, ...
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1answer
72 views

Where does the Higgs Boson fit in the three generations of charged particle?

I am reading a book called "Gauge Fields, Knots and Gravity" by Baez et. al. In the first chapter, the authors explains that there are three generations of charged particles: First: electrons, ...
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2answers
179 views

Do shadows have mass?

It sounds like a joke but I just want to know if shadows have mass, since shadows are formed when there is blocking of light. It forms a black pattern with no energy therefore it has no mass.
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1answer
199 views

Particle Physics Decay Question - Eta Prime Decay Parity/Angular Momentum Conservation

I was hoping someone could clarify why the following decay does not occur: $ \eta ^{'0} \rightarrow \pi ^{0} + \rho ^{0}$ The quark compositions and spin parity are as followed: $ \eta ^{'0} : (u\...
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2answers
80 views

Neutron antineutron reaction documentation

Has neutron-antinutron reaction been observed? If so, can you please provide a documentation (experimental observation) for neutron antineutron reaction?
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3answers
935 views

Where does the majority of the mass of the usual matter come from? [duplicate]

I apologize in advance to experts for the naivety of the question. It should be a duplicate but I didn't find any satifying question or answer about that. The proton is composed by two up quarks ...