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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Why does antimatter and matter fuse to release energy even though they will cancel each other perfectly?

I have seen many physics people talk about antimatter as a evil twin of matter and when they come in contact with each other leave massive amount of energy instead of only void. If antimatter and ...
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0answers
17 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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0answers
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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27 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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1answer
85 views

Equivalence of nonlinear sigma model and the $CP^1$ model

While studying the non-linear sigma model, defined by the action $\mathcal{S} = \int dtd^2x (\partial_\mu n^a \partial^\mu n^a)$ along with the constraint $n^a n^a=1$, people often use the map $n^a = ...
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0answers
66 views

Why are spin-1/2 particles the simplest particles? [closed]

Paul Dirac, in his interview with Friedrich Hund, mentioned that it was to his surprise that his equation automatically incorporated spin. He said that he thought the simplest theory, for which he was ...
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2answers
32 views

time of flight between two scintillators

I found this page on Wikipedia about finding distance between time of flight of two particles passing past two scintillators, https://en.wikipedia.org/wiki/Time_of_flight_detector, but I can't find ...
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1answer
40 views

Does our Universe reside in the smallest particle? [closed]

I do not know where to ask this question in the first place, but I think here would be a start. Is there a possibility that if we go inside the smallest particle (which we have not discovered yet; ...
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2answers
53 views

Neutrinoless double beta decay: annihilation of neutrinos or nucleon absorption?

I've a question regarding the interpretation of the neutrinos in neutrinoless double beta decay: The basic issue that I have is with papers that regard the decay as a neutrino-neutrino ...
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1answer
81 views

Can I catch a particle (such as electron) and say it's left hand

Why is only the left hand electron coupled to weak interaction? How can I tell the chirality of an electron?
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0answers
34 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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1answer
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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4answers
202 views

Why do we say that photons are particles? [closed]

This question may appear stupid but I really do have to understand. Maybe it's just semantic and nothing else. Why do we say that photons are (elementary) particles? They are pure radiation, since ...
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1answer
81 views

How can neutrinos have both mass and helicity?

If a neutrino has mass it must travel at less than the speed of light. So how can it possess helicity, which can change depending on relative velocity?
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0answers
38 views

What are the essential pure mathematics branches applied in theoretical high energy physics [closed]

I am a physics graduate student.I am interested in theoretical high energy physics.Very often people say that to be a good theoretical physicist you need to know mathematics very well.Now although we ...
3
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0answers
21 views

Physical inituition for axial and vector form factors of a hadron

I often see a decomposition of the matrix element $\langle V|\bar{q}\Gamma^{\mu} Q |P\rangle$, where $V$ is a vector particle, for example a vector meson or a photon, $P$ is a pseudoscalar meson, and ...
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125 views

Do photons generate gravitational waves since they affect with their energy the stress tensor?

The gravitational waves are fact. They are produced in a way predicted 100 years before by Einstein. Anything with energy affecting stress tensor of space time produces them. What does it happen with ...
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2answers
50 views

Questions about particles and their forces

Consider the hypothetical scenario where 2 particles are headed for each other in a collision course but neither interact with a common force. Do these particles simply pass through each other?
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34 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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1answer
22 views

How to calculate the decay rate of Higgs to lepton pair?

In class, the generic formula we've been given for calculating scattering amplitudes for the weak decay (at low energies so that the interaction is effectively point-like) is $$ M= ...
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3answers
120 views

How can we conciliate the structure of a proton and Coulomb/strong force? [closed]

I was told in answers to my questions that the schematic picture at wikipedia is misleading, that the 3 (valence) quarks are point particles, sit in on the outer edge of a proton (r = .85 ftm) and ...
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0answers
43 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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0answers
13 views

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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0answers
35 views

What is the difference between Breit-Wigner mass and pole mass in PDG?

In Review of Particle Physics 2014, page 81, in the baryon summary table, there are usually noticeable differences between Re(pole position) and Breit-Wigner mass, for example, for $N(1440)$, ...
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68 views

Do all particles have radiative transitions?

Everybody knows that excited electrons can emit photons upon relaxation. A nucleus too (which is not an elementary particle), can be in an excited state and emit gamma rays upon relaxation: (source) ...
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23 views

Ideas for experiments on the Beamline for Schools at CERN? [closed]

I'm thinking of participating in CERN's Beamline for schools competition. To those who do not know, they offer a batch from a school to conduct their own experiment on a small scale particle ...
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1answer
32 views

Particle lifetime doesn't depend upon longitudinal momentum

I am writing a report on an analysis of the $B_{s}$ meson from CDF data, and as part of the lifetime analysis, I have noted down that: $$\tau = \frac{l_{xy} m_{B_{s}}}{p_{T}}$$ Where $l_{xy}$ is the ...
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1answer
31 views

What is the likelihood of pair production for a high energy photon?

Wikipedia says that pair production is the dominant form of light-matter interaction for photons with a mass equivalence of at least twice the rest mass of the target particle, implying that not all ...
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0answers
31 views

Decay rate and differential cross-section

If I have a $pp-$beam producing an on-shell particle $A$, which then decays into particle $B+C$, then I can find the total cross-section $pp \to A \to B+C+Y$ ($Y$ being inclusive particle which should ...
2
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1answer
173 views

Confirming an inconsistency of the Balitsky-Kovchegov equation between references

I'm comparing the form of the Balitsky-Kovchegov equation, which describes the splitting of low-momentum gluons, between different references, and I'm finding an inconsistency: most sources (1, 2, 3, ...
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2answers
97 views

Proof that 1d lattice displacement by phonons is given $u_{n\pm 1}(t) = A_ke^{i\omega_k t} e^{i knd}e^{\pm i k d}$

I looked in «Kittel - Introduction to solid state physics», Wikipedia and Google for the derivation that: A phonon of wavenumber $k$ displaces the $s$-th atom in a monoatomic 1d crystal lattice by a ...
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55 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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1answer
60 views

Is Electron decay period less than stated?

Phys. Rev. Lett. 115, 231802 – Published 3 December 2015 sets a limit on the stability of the electron for decay into a neutrino and a single monoenergetic photon in $\tau\ge6.6\ 10^{28}\ ...
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30 views

Cloud chamber and observations [closed]

What are the best ways to use a cloud chamber to study particles. What would you gain from observations done in a cloud chamber.
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1answer
38 views

Understanding wave functions of matter waves

The wave functions of matter waves give the probability density of the particle being at a certain location. Does this arise because as an outside observer, we have incomplete information about the ...
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4answers
94 views

Where does the energy lost due to light emission come from?

If an object lose energy when it emits light, does that energy come from the mass of the object? Examples: Does a flashlight lose mass when it's turned on? Does a regular object (like a pencil or a ...
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2answers
55 views

Helicities in electron-positron annihilation

Consider the massless limit of a process in which an electron-positron pair annihilates into a virtual photon - the final state doesn't matter. If the electron is massless (or if the energy is high ...
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0answers
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
34 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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1answer
60 views

Collision of electron and proton of high energy [closed]

What will happen when proton and electron with high energy like in 100 TeV collide?
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21 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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1answer
61 views

Charged particle/cosmic ray track on sunglasses

I left my (polarized) sunglasses on car dashboard .. . Returned, and immediately noticed a strongly lightened, partially dotted streak across entire left lens, cutting diagonally from "northwest" to ...
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1answer
51 views

Couplings of fields in the Standard Model

Could someone please explain what this task implies: Calculate coupling of fields: $\bar{e}_{R}e_{R}Z, HW^{+}W^{-}, W^{+}\bar{c}_{L}d_{L}$? (Exercise refers to the Standard Model Lagrangian). What do ...
2
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1answer
63 views

Conceptually speaking, why does synchrotron radiation arrise?

First, a bit of background. I'm a chemist who works with synchrotron-based techniques, but I'm focussed on materials analysis rather than synchrotron physics. I'm struggling to work out where ...
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0answers
32 views

How many Cherenkov photons on the track of the electron? [closed]

I have this problem where a neutrino interacting with deuterium decay in 2 protons and 1 electron. This electron will produced Cherenkov photon. The specific energy loss of heavy water is ...
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3answers
53 views

Photocurrent's dependence on frequency [duplicate]

Sounds like a rookie question, this, but could someone please explain to me why doesn't photocurrent increase when we increase the frequency of the incident radiation? I mean, an increase in frequency ...
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1answer
24 views

Relativistic blast waves in medium of non uniform density

The relativistic outflow of a gamma ray burst drives a shock into the circumburst medium. This medium could have a uniform density $n_0$ or a density profile of the form, $n(r) \propto r^{-2}$. For ...
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3answers
123 views

String models of particle physics

What general features of particle physics are derived/replicated by constructing string models of particle models? How do such models address the fixing of free parameters like the masses and the ...
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0answers
46 views

Can a photon be captured in a grid space representation at a fractional Planck position?

Consider a photon, positioned in space in a finite portion of a grid. Any point of the grid is vertically or horizontally aligned, each distanced by a Planck unit. $l_P = 1.616 199(97) × 10−35 m$ ...
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105 views

Feynman diagram; $\pi^0+\pi^0\rightarrow \pi^++\pi^-$

For the reaction below draw three Feynman diagrams, one that proceeds through exchange of a gluon, one through a photon and one exchanging a weak W-Boson. $\pi^0+\pi^0\rightarrow \pi^++\pi^-$ Which ...