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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Exercise: Calculating Q-value for $D_0 \to \chi_s^-e^+\nu_e$

Question Is the following methodology correct in calculating the Q-value (change in kinetic energy) for the $D^0 \to \chi_s^-e^+\nu_e$ decay process? Steps The change in kinetic energy is ...
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81 views

What particles do these Feynman diagram lines represent?

What particles could be represented by A and B (labels I have added myself - this is not a homework question)? For A, it looks like it's supposed to be a photon, but I was under the impression that ...
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32 views

Why can an electric chargeless Z-particle decay in three photons?

The Z-particle that is supposed to convey the weak force has no electrical charge. So how is it possible the particle can decay in three photons. Because the weak and e.m. force are more or less ...
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21 views

B meson mixing and CP violation

From my understanding of CP violation in the weak interation only the $V_{ub}$ and $V_{td}$ terms in the CKM matrix contain the complex phase terms which introduce CP violation. In B meson mixing, ...
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33 views

Electromagnetic Field caused by accelerating and oscillating charge particles?

Will accelerating and oscillating charges will cause EM waves of different shapes ? As EM waves are always shown as sinusoidal Electric and Magnetic Fields perpendicular to each other. Does it mean ...
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45 views

Are quadrilinear weak boson couplings possible?

$ZZ\rightarrow ZZ$, $ZZ\rightarrow W^+ W^-$, etc. Are these interactions possible?
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34 views

Feynman Diagram of $\nu_\mu + p \rightarrow \nu_\mu + p + \pi^0$

According to my class notes, the following interaction is possible $$\nu_\mu + p \rightarrow \nu_\mu + p + \pi^0$$ I tried drawing a Feynman diagram and got the below, but don't know what happens ...
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9 views

Question pertaining to the branching ratio of Ka0ns

I'm a little lost for part c of this question: I understand the $\mathcal{BR}$ (branching ratio) for species $i$ is $\mathcal{BR}=\Gamma_{i}/\Gamma_{T}$ (total Decay width). I know that $$\...
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50 views

How to draw Feynman diagram for K^- + p -> Sigma^0 + pi^0 — superposition in diagram

I'm trying to draw the Feynman diagram for the reaction $$K^- +p \rightarrow \Sigma^0 + \pi^0$$ I have two problems: How to draw the $\pi^0 = (u\bar u + d\bar d)/\sqrt 2$, a superposition of ...
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37 views

Gravitational entropy [duplicate]

In the beginning (big bang), mass was evenly distributed (if you consider an elementary particle as an extended object, like a circle on a very thin cylinder, with a radius near the Planck length, but ...
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20 views

Semileptonic decay of neutral D meson: branching ratios?

I am looking for the branching ratio of the semileptonic decay of the neutral $D^0$ meson: BR($D^0 \to \pi^+e^-\bar\nu_e$) = ? According to the PDG book the branching ratio for $D^0 \to \pi^-e^+\...
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30 views

Are alpha and beta rays also generating electromagnetic rays?

To discover radio waves in 1886, Hertz used electric sparks between two iron balls. These sparks caused radio waves which generated a current between other balls. The oscillating charges caused a ...
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16 views

Conjugation Operator General Question

I’m sitting here reading my particle physics book, and the Conjugation Operator is defined as: $C = -(-1)^{S+1}(-1)^{L}$, where $L = $ relative angular momentum for the $q\overline{q}$ pair for a ...
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59 views

What is more fundamental $E=\hbar \omega$ or $E=c\hbar k$?

Let us say I have a massless particle (not necessarily a photon) then in a medium where $\omega \ne c k$ (e.g. a dispersive medium) what is the energy of the particle? As my title indicates are think ...
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32 views

Motion of an electric charge within an electric field with two electric charges

Assume that air resistance and gravity are negligible and the only significant force acting in the scenario is the electric force. There are two electric charges, both with an equal and positive ...
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46 views

Lagrangian derivation of Thomson scattering cross section (ie photon-electron)

Does anyone know a quick way to obtain the classical Thomson scattering scattering cross section (for photons scattering on electrons) from quantum mechanics/quantum field theory, avoiding the lengthy ...
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1answer
27 views

The highest photon energy ever measured and transplanckian energies

What is the highest energy of we have measured of a photon by any physical experiment? Has a transplanckian energy photon been measured? Can we study them -if they exist- with special relativity?
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25 views

Topics important in electrodynamics for particle physics

Say I'm going to study Griffith's electrodynamics, what are the important topics in it, for particle physics? Like Maxwell equations etc.
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31 views

Helicity of massive particle at high enengy

We know that massless spin-1 particle like photon only has two helicity state (-1,1), what about the helicity of massive spin-1 particle (W boson) at very high energy? Does it have helicity 0 state ...
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23 views

Finding the mixing angle for two-neutrinos

I am trying to answer the following question; Light Majorana neutrino masses can be generated by the see-saw mechanism. Consider a mass term which, in the simplest case of one active and one ...
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54 views

Wave function of particle and antiparticle

The wave functions of particle and antiparticle are related by complex conjugation and wavefunction Ψ must be complex for particle such as n, p. Is there way to prove this mathematically? Can we do ...
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13 views

Is the back induced emf in inductive coil equal to the original? [duplicate]

I always thought that an inductor resists the change of magnetic flux to a CERTAIN EXTENT, that is it would generate a back emf that would provide only a percentage of obstruction to the original emf. ...
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24 views

How to calculate probability of neutrino oscillation after a distance

I'm trying to calculate the probability of an detecting a muon neutrino after a certain distance, where the neutrino beam is entirely electron neutrinos as t = 0. I know I need to use the PMNS matrix ...
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42 views

Could we live if we were made of antimatter? If so, would there be any difference to experience?

Antimatter is material composed of antiparticles, which have the same mass as particles of ordinary matter but opposite charges, as well as other particle properties such as lepton and baryon numbers ...
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129 views

Higgs boson and dark matter.

In the standard model the Higgs boson gives the mass to other particles, but in the Universe we know that the 80% of mass is in form of dark matter, that is not constituted by known particles. The ...
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Why are there presently more electrons than positrons in the universe? [duplicate]

After the Big Bang, when the universe was extremely hot, there was a symmetry in the population of electrons and positrons. But in the present universe we observe a large number of electrons and ...
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39 views

Why do Higgs decays depend on the production method?

I'm reading about Higgs phenomenology and I have come across the following table. I don't see why gluon fusion to $b \bar{b}$ is considered to be "impossible" in this table. As far as I can tell, ...
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16 views

Would the ultra high energy particle beam be scattered in plasma accelerators?

Plasma wakefield accelerators accelerate particles in hot plasma instead of cold vacuum chambers of superconductor linacs. Would the particle beam collide with ions, electrons or thermal photons in ...
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23 views

is the earth's atmosphere positivly charged? [duplicate]

Is the earth's atmoshere charged with positive ions? What are the effects of positive verses negative ions?
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19 views

Parent particles. Production modes of hyperon $\Lambda$

In the PDG are listed the decay modes of the known particles. I wonder if there exist lists with the production modes of particles. It is, lists with all the possible parent particles that decay into ...
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67 views

How the state of elementary particles change under lorentz transformation?

Let us take three observers namely Alice, Bob and Charlie. Bob is stationary with respect to Alice, but his axes are rotated from her's.We can get Bob's coordinate axes by rotating Alice's through 60 ...
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37 views

How do we know that A is a pseudoscalar (CP-odd) Higgs?

Starting from a model with two complex Higgs doublets (as e.g. in the MSSM) we arrive at 5 physical Higgs bosons (instead of 1 as in the Standard Model), 2 of which are charged and 3 are neutral. One ...
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35 views

Proton-Proton collision [duplicate]

How are the people at CERN able to exactly collide protons head on? What about the HUP? Do they accelerate many particles and smash them so that at least some of them collide head on?
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34 views

Massive spin one pseudovector decay?

Suppose you have a massive spin one pseudo-vector particle. Is it allowed to decay into an electron-positron pair? I'm thinking it might be disallowed because of parity conservation. If it is ...
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37 views

A question relating to the Higgs boson scalar field

Just wondering. The potential for the Higgs boson is given by: $$ V(\varphi)=\lambda(\varphi^{2}-v^{2})^{2} $$ where $v≃$ 246 GeV is the vacuum expectation value required to explain mass in the ...
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44 views

What causes certain particles to have charge? [duplicate]

The three major measurements for the elementary particles are mass, spin and charge, mass is supposedly achieved through interaction within the Higgs field due to the Higgs effect, spin is the angular ...
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What is the meaning of the minimum separation requirement?

In this work, BHsearch done by CMS, they reconstructed and identified objects using certain conditions. And finally, in Page 3, the last paragraph requires that the minimum separation between any two ...
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87 views

Electric field inside the “Dees” of a Cyclotron and why no “Cups”

I read about cyclotron and how does it work. Several references say that the particle to be accelerated is only accelerated when it is between the gaps of the "Dees" or the semicircular disc like ...
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17 views

Voltage drop along electron beam

A focused electron beam represents a current and unless the charges (electrons) meet no resistance to their movement there should be a voltage drop along the length of the beam. So, assuming the beam ...
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1answer
35 views

Particle physics books [duplicate]

I am a A-Level student. I have keen interest in physics, especially particle physics. So, I want to know some websites where I can find free books or other study materials to study particle physics as ...
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23 views

Good books to read [duplicate]

I still regard myself as a beginner in the field of physics.. And there are a lot of information I should know, I am in my second year physics, and I need to read books which are not hard to ...
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Is the video “How to Reveal Subatomic Particles at Home”'s explanation of its experiment misleading?

https://www.youtube.com/watch?v=wN_DMMQEhfQ The video asserts that along the path of an electron or muon, a trail of condensation will appear. But from what I understand, if an electron or muon (both ...
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27 views

How to determine likelihood of baryon decay

If I want to determine the probability of $\Sigma(1385)^+ \to \Lambda^0 + \pi^+$ how would i do this? I know I have to do something with the $J^P$ value of each part of the decay, but I'm not sure ...
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26 views

Decay of lepton into meson and neutrino using four-momentum

I'm learning about how to use four-momentums and am working through a problem involving the decay of a charged lepton into a charged meson and neutrino. The equation would be: $L^+ \to M^+ + \nu$ I'...
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1answer
57 views

What is the best software to simulate the tracks of muons in matter?

What is the best (free) software to simulate the tracks of muons in matter? I have done some simulations using SRIM/TRIM (www.srim.org) by modifying their proton model to have the mass of a muon, but ...
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1answer
43 views

Does the electromagnetic force “split” at lower than normal energies?

Since we have working models for forces "combining" or being describable via a single framework at higher energies (such as the "electroweak" force and the aim of GUTs), does electromagnetism split ...
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67 views

Obtaining an angular distribution from the Klein-Nishina formula

I'm having trouble on how one might obtain an angular distribution from the Klein-Nishina formula for compton scattering of polarised photons, more specifically on how this report is obtaining it. (...
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The magnetic moments of Hadrons

So I am very confused about how to find the magnetic moment of a arbitrary hadron. I have found out that the magnetic moment of a quark is given by: $\mu_q = \frac{e_qM_p}{m_q}\mu_N$ Where: $e_q, ...
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1answer
49 views

Four momentum in particle physics

I have seen four momentum defined in two different ways. One is $P =(E,\vec{p}c)$ and the other is $P =(E/c,\vec{p})$. Which one is correct and if they both are then why and when is it more convenient ...
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Mass difference in particle oscillation from weak lagrangian

Looking for an answer to how an expression to $\Delta M = M_2 - M_1$ arise in QFT I have found the approximation \begin{equation} \Delta M_K \approx \frac{G_F^2}{4\pi} m_K f_K^2 \sum_{q=u,c,t} m_q^2 \...