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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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Can supersymmetry be disproved? [duplicate]

Recently there are a lot of news about the plans to build the FCC accelerator, with many claims of possibilities to find new particles, for example like those suggested by theories of supersymmetry. ...
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1answer
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When/Why Did Physics Discard The Point Charge As An Accurate Representation? [closed]

Is there anything about the implications of the "early" quantum theory of Schrodinger equation, wave-particle duality, or the two slit experiment that conflicts with the idea of a point charge? Did ...
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Diagrammatics of a current-current correlation function $\langle 0| T\{J^{\mu}(x) J^{\nu}(0)\}|0\rangle$

Say $J^{\mu} = \bar{\psi} \gamma^{\mu} \psi$ is the QED current. While it is clear to me how to compute something like $$\langle 0 |T\{ \bar \psi(x) \psi(0)\} |0\rangle$$ using a Feynman diagram ...
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What is the difference between a neutrino and an electron neutrino?

So, what is the difference between a neutrino and an electron neutrino? Like how does the term 'electron' made a difference? Also, what is the difference between an antineutrino and an electron ...
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1answer
62 views

The Majorana condition and C violation

Is the Majorana condition $$ \psi = \psi^c = C \overline{\psi}^T, $$ general? The point is often made that Majorana particles should be defined by CPT symmetry and not C as generally theories do not ...
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Are neutrinos just different states of a single particle, in essence?

When Neutrino oscillation phenomenon is analysed quantum mechanically, it is said that, \begin{align} |\nu_e \rangle &= \cos(\theta) | \nu_1 \rangle + \sin(\theta) |\nu_2 \rangle,\\ |\nu_\mu \...
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2answers
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How does particles move in waves? radiation?

I'm reading about particles for a project and had a question. I read that particles don't move forward in a wave, the simply oscillate up and down, and that gives it the wave look. But if they don't ...
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Why does a cloud chamber perform worse if you use too much alcohol?

I have posted here before about the essay I am doing with my cloud chamber and I got a lot of help so here I go again. I know that a cloud chamber should have a felt that is covered with isopropyl ...
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What is hierachy problem in Higgs mass? [duplicate]

What is actually the hierarchy Problem in Higgs mass? And whether we expect the Higgs mass to be huge experimentally or theoretically?
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Is string theory inconsistent with the Standard Model of Elementary Particles?

According to (super)string theory, each fundamental particle represents a different vibrational mode of a relativistic string and each type of vibration pattern represents a different particle. But ...
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1answer
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What is the definition of “force” in quantum field theory?

In quantum field theory, there are certain interactions that we seem to associate with the action of "forces." For example, the exchange of a gauge boson between two matter particles is associated ...
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2answers
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Doesn't dark matter imply a new force?

Given that every particle that we have experimental confirmation of is an oscillation of its field (from what we know), and given dark matter is thought to be a particle yet undiscovered according to ...
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Particle collision and mass relation [closed]

Is mass important in calculations when two particles are collide? or is only the charge that matters? is collision in microscopic world the same with macroscopic world?
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1answer
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Dark Matter gamma-ray flux from hadronic annihilation channels?

For a project I am currently reading into indirect detection of Dark Matter via gamma-rays from DM subhalo's. I understand that there is a possibility of DM annihilating with each other in these ...
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1answer
40 views

What direction would this photon go?

Say a matter-antimatter pair of particles annihilates linearly (from a reference frame where the sum of the momenta is zero) to create a photon. Wouldn't momentum conservation prevent the photon from ...
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1answer
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If strings of matter are of the same substance how can matter carry differing charges?

Considering that a string is a loop of energy composed of the same underlying material how is it possible for it to be either positively or negatively charged? For that matter, how is it possible for ...
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Total heat loss from Human body [duplicate]

I want to calculate total heat loss from human body.Please tell me how I will determine total heat loss from human body?
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20 views

Alternative to Helium-Neon mixture when building a spark chamber

I have a project for building a spark chamber however have no way of procuring the Helium Neon gas mixture as used by http://www.ep.ph.bham.ac.uk/DiscoveringParticles/detection/spark-chamber/ Is there ...
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How to determine exchange particle of two-to-two process?

For the process, $e^+e^- \rightarrow e^+e^-$ I know that the exchange particle is a photon and for the process $\gamma\gamma \rightarrow e^+e^-$, the exchange particle would be an electron but I'm not ...
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1answer
66 views

How much harder is a proton theoretically speaking than a diamond? [closed]

It's generally said that a diamond is the hardest substance known to man (apparently there are a few materials known to be harder). However, one ought to expect that a proton or neutron should be ...
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2answers
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Could we use experimental evidence of micro black holes to prove the existence of additional spatial dimensions?

They are planning to create a new particle accelerator that can smash particles together at a much higher energy than the LHC. If in the process we observe the decay of a micro black hole, would that ...
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1answer
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What physical law(s) are violated by two masses occupying the same space at the same time?

The two masses have equal mass and equal volume. I think the 2nd law of thermo is violated (because there are less ways to arrange a single mass in space than two), but what other laws could be ...
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1answer
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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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2answers
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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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1answer
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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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1answer
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Gamma Photons vs. Muons; Which is more expensive [closed]

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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1answer
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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 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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3answers
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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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1answer
55 views

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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2answers
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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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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
47 views

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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2answers
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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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1answer
66 views

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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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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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 ...