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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Has the mass of longitudinal and perpendicular spin 1 mesons been measured separately?

This might be a silly question. When the mass of a spin 1 meson is measured, is there a way to check whether it is the same for all polarizations? Is such a meson mass the same for longitudinal and ...
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634 views
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92 views

How are particle simplices associated into complex particles?

Nonfundamental particles are seen as made up of fundamental particles (in whatever specific theory). consider the simple case of 2 simplex particles (subscript 1 and 2) which form a complex particle (...
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666 views

Where to find experimental/theoretical value of (charge) radius of particles?

Where to find experimental/theoretical value of (charge) radius of particles like proton, neutron, $\pi^+$, etc.?
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229 views

Speed Distribution of The Particles

I want to know the distribution of the particles's speed. The particles what I mean are nucleons and electrons of element. Consume there is 1kg of iron on room temperature and it's shape is sphere. ...
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178 views

What is the dominant interaction in elastic collision pi- + neutron -> pi- + neutron?

What is the dominant interaction in elastic collision pi- + neutron -> pi- + neutron? Is it strong nuclear interaction or electromagnetism? Edit: sorry I meant to say "elastic". There is no matter - ...
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244 views

Is the quantum state or information of a particle is all that differentiates it from another particle?

So I have learned in my QM classes that you can't tell one electron from another electron. They are indistinguishable. I also learned that the wavefunction of a particle includes the spacial part and ...
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50 views

How to understand CP-violation in kaon systems with Feynman diagrams and matrix elements?

I am trying to understand CP-Violation in the Kaon system using feynman diagrams and matrix element. Here is a slide from Mark Thomson corresponding exactly to what I am looking for (http://www.hep....
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55 views

Internal structure of electrons and quarks

I have some questions about experiments to probe the internal structure of electron and quarks. What type of experiments were done, in the recent years, to probe the internal structure of the ...
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33 views

Basic calculus of the adjoint spinor being transformed under parity

In Modern Particle Physics (p.287) Thompson says that under the parity transformation of the adjoint spinor we have $$\bar u=u^\dagger\gamma^0\rightarrow^p (\hat Pu)^\dagger\gamma^0= u^\dagger\gamma^{...
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16 views

How to know the cross section in this Fig

I wonder how to calculate the cross section of ( p p > gamma gamma b b~) (blue region) in the opposite plot, the y-axis is the number of events divided by 100 GeV with luminosity = 100 $\mbox{fb}^{-1}...
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27 views

What is meant by interactions being mediated by force-carrier particles?

When a photon interacts with an electron, what is observed to happen? Force-carrier particles are described as the mediators of these interactions. What does this mean and how is this concluded?
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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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25 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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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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36 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
34 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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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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26 views

Scanning Electron Microscopy on a smaller scale

Is it possible to sufficiently focus a ~1nm beam of electrons into a sample chamber in less than 10cm of vertical space, therefore reducing the volume of the entire vacuum chamber, and subsequently ...
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1answer
44 views

Do Calabi -Yau shapes also influence a strings particle identity?

Since strings reside on the surface of a d-brane, and it' a three dimensional hyperspace, are their manifestations as certain particles also influenced by Calabi Yau Spaces? Could the way strings ...
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25 views

How is the decay width of a resonance is measured?

Last December LHC found an excess in the diphoton channel around 750 GeV. Along with number of excess events and cross section for proton proton -> gamma gamma process, they also provided a width for ...
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57 views

How are the standard model and the Higgs boson actually confirmed experimentally in practice?

This is my mental picture on how we can make predictions from a theory (I'm not a physicist so this might be quite wrong) : Typically, we solve a partial differential equation (analytically if we can,...
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21 views

Need a mass to accelerate to create gravitational waves?

For a charged particles which travels through an electric field it only emits photons when it is accelerated. It undergoes a change of momentum, and the law of conservation of momentum requires some ...
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22 views

Do subatomic particles spin? [duplicate]

What exactly is "spin" of subatomic particles such as electrons and protons? Does it have any physical significance, analogous to the spin of a planet or Mon?
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30 views

Lagrangian Interaction Type and Spin-Dependence

So I'm transitioning from reading particle physics books to the literature, specifically as it pertains to dark matter models. In this case I'm talking about t-channel DM-nucleon scattering. They ...
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54 views

Mystery $p^0$ particle

Some exercises in my physics book mention a particle denoted $p^0$, but I can't seem to find any information about this particle, neither in my book nor on the web. I've been able to deduce from the ...
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2answers
36 views

Total Angular Momentum of Hadrons

Hadrons are made of 2 or 3 quarks. Quarks have spin 1/2, so Mesons can have spin S = 1 or spin S = 0, and Baryons can have spin S = 3/2 or spin S = 1/2. Is there orbital angular momentum of the quarks ...
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28 views

Does a cathode ray tube emits electromagnetic waves from a steady DC electron beam?

In cathode ray tube, heated cathode emits stream of electrons but when I wrap a coil around tube a current will be inducted in that coil? after all electron beam is a steady DC current? so no emf?
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23 views

What is the most essential theoritical constrains should be imposed on arbitrary potential's parameters?

I'm little confused about the unitarity and perturbativity constrains which imposed on a potential's parameters, like 2HD potential. Look for example: [arXiv:1507.03618v3 [hep-ph]] First, I'd like to ...
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1answer
16 views

If cathode rays travel from the cathode to the anode how do they make zinc sulphide glow?

So I basically learned about cathode rays today, and I had a lot of questions in mind. So my textbook says cathode rays travel from the cathode to the anode. So it further says that to observe ...
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12 views

Transverse momentum [duplicate]

I'm having an introduction on detector systems in particle physics. The sources I read constantly talk about the measurement of "transverse momentum". However, I cannot find a definition of what is ...
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20 views

Why can $\chi_{c}$ states not decay leptonically?

I am trying to understand why the $\chi_{c}$ states of charmonium cannot decay to $l\overline{l}$ pairs. I believe it is because they have positive parity, but I'm unsure why this prevents the decay?
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20 views

Particle interaction kinematics in lab frame

Attempting a question from a past paper on scattering kinematics, fixed particle mass $m$ is struck by another particle mass $m$ with kinetic energy $T$. By evaluating $s$, $t$ and $u$, and their sum ...
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12 views

Why is the bottom antibottom decay channel for the Higgs difficult to observe? [duplicate]

This is a question from a past paper on particle physics, it asks: Explain why experimentally it was easier to observe $h \to\gamma\gamma$ rather than $h \to b\bar b$ which has the highest ...
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22 views

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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2answers
82 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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37 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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24 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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34 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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46 views

Are quadrilinear weak boson couplings possible?

$ZZ\rightarrow ZZ$, $ZZ\rightarrow W^+ W^-$, etc. Are these interactions possible?
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35 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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10 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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55 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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1answer
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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32 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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60 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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1answer
34 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 ...