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Questions tagged [particle-physics]

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 to know what type of diagram contributes to a two-to-two process?

There are 3 types of diagrams that can contribute to a two-to-two process; the $s$-channel, $u$-channel and $t$-channel. How do I know what diagrams can contribute to a process? I know that in QED, ...
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Predicting the frequency of visible light

Why can't the Standard Model predict the frequency of visible light? For example, were it possible to invent a universally extensive 'field' in which wave properties are inherent, including those of ...
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What are “large hadrons”? Are there also “small hadrons”?

The BBC News article Cern plans even larger hadron collider for physics search says: The difficulty with Cern's proposals for a larger Large Hadron Collider is that no one knows what energies will ...
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How do we know what happened during the Planck epoch era of the big bang?

The Cosmic Microwave Background provides the left over radiation of the big bang. Cosmologists have theorised what happened at the Planck epoch era of the big bang. Where is the evidence of what ...
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Gamma Photons vs. Muons; Which is more expensive [on hold]

Which one takes more energy to produce? I ask as I theorize that keeping the plasma in a fusion reactor is very expensive. Muons, while useful, are too short lived. Maybe... Keeping the plasma at ...
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How to determine the squared average amplitude for $\nu_e(p_1)+d(p_2)\rightarrow e^-(p_3)+u(p_4)$?

I have the following charged current interaction, at quark level, by the process: $$\nu_e(p_1)+d(p_2)\rightarrow e^-(p_3)+u(p_4)$$ By assuming that the energy is such that I can neglect the lepton and ...
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31 views

Alternative particle types?

If we consider mass and charge to be excitations of independent quantum fields, do they necessarily travel together? Can we have objects with only an excitation on the mass field, and objects with ...
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Why the Higgs mass has a upper and a lower bound?

in the above diagram what the $\Lambda$ axis is physically describing? How the graph will look like below 1TeV? why it is called new physics cut off scale?
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Why can a particle decay into two photons but not one?

I recently read an old physics news about the Higgs boson where it was observed to decay into 2 photons and I was wondering why it wouldn't have decayed into a single photon with the combined energy ...
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How would a fast-moving atom interact with a body? [closed]

I found this question on Quora: https://www.quora.com/Can-you-theoretically-shoot-an-atom-fast-enough-to-kill-its-target I think the Quora answer is good but incomplete, and it got me wondering what ...
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SLED SLAC voltage and power profile

Anyone who has read the concept or papers related to sled slac, can tellme how to plot the voltage and power profiles?
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How to analyse the LHC signal for Higgs?

With increasing energy the collision decreases in the plot for signal in LHC. why is that? and at an energy 125GeV the no of events suddenly increases. How this proves that higgs has a mass of 125GeV?
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Electron waves through conductors

I'm not a student, professor, or academic scholar so please excuse me if this question seems "amateur". I'm very curious about how electricity, magnetism, and frequency all work together. From my ...
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Mermin Wagner theorem proof, what does the K stand for ?

I've been reading about the Mermin-Wagner theorem recently. I think I understand pretty much every computation need to derive its result from the Bogoliub inequality, but there is one thing I don't ...
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Is it higgs boson which is responsible for generation of mass? [closed]

From where actually the mass of elementary particles is generated. Is it due to the higgs field or due to ziggs field(i.e chiral symmetry breakdown)
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Computational solution of exponential decaying wavefunction tail

As I am going through some (quite simple) computational physics exercices I have a question concerning one exercise that involves solving the radial Schrodinger equation. This is done with the ...
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1answer
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Can neutrinos change chirality by oscillating?

Active neutrinos are left-handed while sterile neutrinos are right-handed. There are speculations that active neutrinos can oscillate into sterile neutrinos. Can neutrinos change chirality by ...
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Looking for a geometric cosmology model where time behaves like an orientation

This question is literally inspired from seeing the above scene unfold. Let the merging and splitting light spots you saw in the above gif be pairs of particles and anti particles, let the shape of ...
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If negative mass should exist, how would conservation of momentum work?

Imagine that a particle with negative mass has been discovered. It is known to obey both the equivalence principle and Newton's second law. This means that the particle is a subject to repulsive ...
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1answer
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Can the deflection of an electron beam create a Lorentz Force capable of propelling a spacecraft?

Please reference the conceptual drawing below of this spacecraft propulsion idea. In the vacuum of outer space, if a strong electron beam enters a strong magnetic field, as shown in the drawing, it ...
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1answer
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Are Generations and Families of elementary fermions one and the same?

I've seen both terms being used in papers and it seems to me they essentially mean the same thing referring to three generations of leptons and quarks as families. Is this true or are there some ...
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1answer
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Is anything expected to be found at CERN with 14 trillion electron volts that wasn't found at 13?

Based on this article the accelerator has smashed together approximately 16 million billion protons since 2015, when it reached its current energy of 13 trillion electron volts. Planned ...
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Left Handed / Right Handed Particles and the Weak Force

Good Afternoon, I am a 50-year-old guy who was never a scientist or physics student. Just a person who loves to read books on particle physics. I have a question on the Weak Force and particles. (...
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Clarification on statement in “Unitary Symmetry and Elementary Particles” by Lichtenberg

He says that: The set of values of the parameter or parameters which characterize a group element can be considered to be points in some kind of space. The number of parameters characterizes the ...
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1answer
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Majorana Neutrinos in the KamLAND-Zen

I'm reading the following paper concerning the KamLAND-Zen experiment "Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen" In the second paragraph of the first ...
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Why do electrons appear more frequently than it's counterpart, positrons? [duplicate]

Electrons appear in electron clouds of atoms but positrons are found in cosmic rays and radioactive elements. Why do electrons seem more common then positrons? Edit: Is this an example of asymmetry? ...
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Invariance vs. Conservation of the Four-Vector Dot Product

This question refers to example 3.4 of Griffiths Introduction to Elementary Particles Second addition. In the example, a moving proton is collided into a proton at rest, producing 3 protons and 1 ...
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1answer
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What's the mass of $D_1(2430)^{\pm}$?

What's the mass of $D_1(2430)^{\pm}$? The standard reference http://pdglive.lbl.gov/ParticleGroup.action?init=0&node=MXXX035 only shows the data for $D_1(2430)^0$ but not for $D_1(2430)^{\pm}$. ...
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1answer
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Muon neutrino interacting with nucleon's quarks

I'm considering the muon neutrino/anti-quark interaction with the nucleons of ice in the IceCube experiment. The purpose is to decide which antiquarks are $\bar{q}$ and $\bar{q}'$. I have the ...
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Collision of electron beams

How much eV is necessary for electron beams in a collider to get generation of electron-positron pairs in electron-electron collisions ?
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How much does $b_1^-$ meson's mass differ from that of $b_1^0$?

How much does $b_1^-$ meson's mass differ from that of $b_1^0$? From reading http://pdglive.lbl.gov/Particle.action?node=M011, it is not very clear.
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1answer
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Propagator for W boson

I've found in different literature that some write the propagator for the W boson as $\frac{g_{\mu\nu}-\frac{k_\mu k_\nu}{M^2_W}}{k^2-M^2_W+iM_W\Gamma_W}$ and others like $\frac{g_{\mu\nu}-\frac{k_\mu ...
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1answer
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Muon neutrino and down quark interaction diagram

My questions concerns the IceCube experiment, in particular, the interaction between muon neutrino and the down quark. I've drawn the following Feynman diagrams: Are both diagrams correct? Can I say ...
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1answer
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Why can the pion decay into two photons?

The neutral pion belongs to the pseudoscalar meson octet, so it has, in the ground state ($L=0$): \begin{align} P_{\pi^0}&=-1 \\ C_{\pi^0}&=+1. \end{align} And the photon has \begin{align} ...
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1answer
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Number of strings? [duplicate]

Is each particle associated with an unique string and where exactly is the string located, if it's vibration produces the appearance of a particle? What I mean is if I see an electron, does it have an ...
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1answer
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How does the nuclear interaction keep protons and neutrons together?

The strong force holds atoms hadrons together by using gluons to change the color charge of quarks and making the hadrons color nutral. But how does the nuclear force keep protons together, I heard ...
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2answers
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Could this feynmann diagram happen on its own? $e^- \to W^- + \nu_e$

I am starting to learn about Feynman diagrams and I wonder if this reaction could happen as a physical process on its own, as opposed to part of a more complicated diagram: $e^- \to W^- + \nu_e$ ...
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Virtual particles

I use Wikipedia to learn physics. In a recent search I found an ample description of virtual particles in terms of a discontinuous (in the present) and asymptotic distribution of these particles from -...
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Transition amplitude in scalar QED from a point-like charge

I have a problem for you to compute. I have a classical source, $A_\mu = \delta_\mu^0 \frac{Q}{r}$, representing the Coulomb potential generated by a point-like charge. I want to compute the ...
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1answer
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When is $Q= B/2 + I_3$ true in particle physics?

I have seen stated that for unflavoured quarks, the relation between baryon number, electric charge and third component of isospin can be written as $Q= B/2 + I_3$. However, I have also seen this ...
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Fields or Particles [duplicate]

What is more fundamental, particles or fields? I keep reading what appears to be conflicting answers on this, but I am sure it is just a limitation of my understanding. I have heard some physicists ...
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2answers
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Corresponding particle-antiparticle solutions for Klein-Gordon equation

For free particle solutions in a box, the following 4 solutions are possible(Not all 4 are independent though) as $$\psi_+=A_+ \exp{\frac{i}{\hbar}(px-Et)}\\\psi_+^*=A_+^* \exp{\frac{-i}{\hbar}(px-Et)}...
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1answer
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Do electrons have third component of isospin?

From what I've read, it seems like there are two types of isospin: the strong and the weak. I guess this means that leptons have no strong isospin, but they do have weak isospin. Am I right? I am a ...
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Removing zero-counts in exponential decay measurement

I'm doing an experiment where I'm measuring the mean-lifetime of muons. I have a set of data points for the number of decays against time, resembling an exponential distribution (of course). But in ...
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2answers
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Is it possible to add energy to an antiparticle?

The title says most of it but the more drawn out version is. If you were to add energy to a single particle or antiparticle in a pair, what would be the effects, if it is possible to do.
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Why should $\nu_\mu\to \nu_e$ oscillations be expected to be unobservable in short baseline experiments?

The blog here says On the other hand, several rogue experiments refuse to conform to the standard 3-flavor picture. The most severe anomaly is the appearance of electron neutrinos in a muon ...
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Universe under Point Reflection — or why is the Neutrino not its own anti-particle?

The spin of a anti-neutrino points into the same direction as its momentum. The spin is a cross-product, so under point reflection it remains the same, whereas the momentum gains a factor of $(-1)$. ...
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SLED (SLAC energy doubler) vs SLAC

The RF pulse length for SLAC is 2.5 microseconds whereas for SLED is 5microseconds, what is the reason for this? Similarly, I wish to replicate the SLED method for European XFEL - how would it ...
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The simple harmonic oscillator model relating particles and fields in QFT

In all of the introductory Quantum Field Theory texts I gave read so far, (such as Zee, Srednicki, Luke), there is an introduction to the concept of fields as operators, following the simple harmonic ...
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Lecture notes by Rudolf Mössbauer

Rudolf Mössbauer was an excellent lecturer. He gave lectures on Neutrino Physics, Neutrino Oscillations, The Unification of the Electromagnetic and Weak Interactions and The Interaction of Photons and ...