Questions tagged [antimatter]
Analogous to matter, but with charge of the particles opposite to their ordinary matter counterparts.
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When an electron and a positron annihilate each other are they deleted from existence entirely? Does this follow the conservation of energy?
When an electron and a positron annihilate each other and release gamma rays, is that just changing the energy into something else (following the conservation of energy), or is energy actually being ...
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Does CERN produce more matter than antimatter?
CERN's LHC has seen matter-antimatter asymmetry, such as CP symmetry breaking and $B_s^0$ meson decay.
The universe produced about 1 part per billion excess of baryons over anti-baryons. My ...
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Particle Anti-Particle annihilation in Quantum Field Theory
What special distinction does the interaction of a particle with its anti particle have compared to an interaction with some other particle?
People often say when a particle and an anti-particle ...
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If an equation describes some physical phenomenon is the assumption that it works in all cases? [closed]
I may be misunderstanding the general idea and the following specific example, but I was told that Dirac predicted the existence of the positron based on a formula for the motion of the electron(?) ...
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Are electrons and positrons part of a family of 4 (8? 16?) similar particles?
EDIT: Completely rewritten because of the 'needs clarity' tag and some useful related questions appearing in the side-bar. I hope this is clear now
This answer gives a long list of properties of ...
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Are two oppositely charged black holes, matter & antimatter?
Let's say we have 2 identical black holes, except that their charges are opposite in sign.
Can we consider one to be matter, and the other antimatter? After all, I heard that anti-particles are the ...
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Observation of the effect of gravity on the motion of antimatter
In a recent paper (https://www.nature.com/articles/s41586-023-06527-1), the authors state that
we find that the local gravitational acceleration of antihydrogen is directed towards the Earth and has ...
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Drawing appropriate Feynman graphs
I have learned to compute the corresponding mathematical expressions for a Feynman graph, however, I am yet to conceive the idea of drawing them properly for example
describes the nucleon-antinucleon ...
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Effect of Gravitational Field During Anti-Matter/Matter Collision
This may be a very basic question, please excuse my lack of knowledge but I don't seem to understand the concept of anti-matter gravity.
Upon research, many sources align with the conclusion that anti-...
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Why does the Matter Anti-Matter imbalance require breaking CP symmetry? Why can't it occur if time symmetry is broken?
I understand the general argument that, without some breaking of symmetry, all the matter in the universe would annihilate all the anti-matter and we'd be left with nothing but photons and some other ...
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Angle of emmitted photons from antiparticle and particle annihilation
I have been given a lengthy question regarding the angle that two equal energy photons will emit from an axis if an antiparticle moving with speed v collides with a stationary (to the lab) ...
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Conservation of momentum with antiparticle annihilation
I'm confused about how momentum can be conserved when a particle and its antiparticle collide. For example, if an electron and positron collide and annihilate to form two photons, then there should be ...
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What are the differences between electron-positron annihilation and electron-positron scattering?
Reading the wikipedia of Bhabha scattering, I see that the electron-positron annihilation and electron-positron scattering are analyzed seperately. What are the differences between these two processes?...
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Which spinor should be used for an outgoing proton if we treated it like a point particle? $\bar{u}(p)$ (as for electron) or $v(p)$ (as for positron)
Consider the Rutherford scattering $e^-p^+ \rightarrow e^-p^+$
If a proton is a treated as a heavier positron:
$i\mathcal{M}=(-ie)\bar{u}(p_3)\gamma^{\mu}u(p_1)i\Pi_{\mu\nu}(-ie)\bar{v}(p_2)\gamma^{\...
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Matter and Antimatter coexistence [closed]
Isn't it possible that matter and antimatter coexist? Recently, the ALPHA experiment at CERN has been looking into this topic. And I read about it from Fermilab's website, so they are saying how our ...
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True efficiency of an ordinary photovoltaic cell
While learning about antimatter and the conservation of energy, I found that fission reactions convert about 0.1% of mass into energy, fusion reactions convert about 0.7%. I also found a similar ...
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What problems might somebody encounter when trying to use the Breit-Wheeler process to produce positron gas?
Let's take a hypothetical an experimental scenario where a stream of high-energy photons from a powerful source is directed via a system of mirrors and lenses in a two coherent rays to a vacuum camera....
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Are Feynman Diagrams Concealing the True Nature of Particle Scattering? [closed]
I've recently delved back into some alternative interpretations of quantum field theory.
While Richard Feynman often emphasized that calculations were sufficient and discouraged fixation on the "...
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Antiparticles of spinors
As far as I know, to couple scalar fields with photons, the fields must be complex, and have two degrees of freedom, which explains why the antiparticles exist. In the spinor cases, spinors themselves ...
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Left-handed antiphotons in negative-index material?
Do “left-handed” antiphotons propagate in negative-index metamaterials?
https://pubs.aip.org/physicstoday/article/57/6/37/914849/Reversing-Light-With-Negative-RefractionMaterials
Some quotes from the ...
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Meaning of annihilate
As a naive person I thought annihilate meant destroy. Matter and antimatter destroy each other, cancel each other, nothing left over. This pure energy idea is a big surprise also it fits no category ...
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Are there any black holes made of antimatter? [duplicate]
And what would happen if an antimatter black hole and a matter black hole would collide?
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Color vectors for antiquarks
For a single quark, the colour vectors are given by
$$r=\begin{pmatrix}
1 \\ 0 \\0
\end{pmatrix} \qquad
g=\begin{pmatrix} 0 \\ 1 \\ 0 \end{pmatrix}
\qquad b=\begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix}$$
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Making sense of particles going backwards in time [duplicate]
Physicists sometimes talk about particles going backwards in time. Help me make sense of this. I thought things don't "go" in any particular direction in time. They just "are" ...
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Has Anti-beta decay been observed?
I am looking for references or resources regarding the transition of an anti-neutron through weak decay, into an anti-proton, positron, and electron-neutrino.
Have such studies been conducted or ...
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Negative energy solutions not a problem for Klein-Gordon equation?
I already posed this question Negative energy solutions in Klein-Gordon and Dirac equations but I am not satisfied with the answers.
Trying to be very sharp:
does Klein-Gordon equation have negative ...
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Is the charge-conjugation symmetry in cond-mat physics different from that in QFT?
In condensed matter physics, the terms "particle-hole symmetry" and "charge-conjugation symmetry" are often used interchangeably. As far as I understand, they refer to the ...
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Why do same-charge particles repel each other? Would anti-particles exhibit the contrary behaviour? [closed]
Coulomb's Law states that same-charge particles repel each other and opposite-charge particles attract each other.
Coulomb's Law formula is:
This is related to Maxwell's equations:
An example of an ...
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Mass of $B$ Meson
This is a question from Griffith's Introduction to Elementary Particles, Chapter 2: The upsilon meson, $b\bar b$, is the bottom-quark analog to the $\psi$, $c\bar c$. Its mass is 9460
MeV/$c^2$ and ...
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Dirac neutrinos?
How can Dirac neutrinos exist if neutrinos have no charge? As far as I'm aware, the antiparticle of a particle is its charge conjugate while all of its other characteristics remain same. How then can ...
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Particle-Antiparticle of Klein-Gordon equation
When we solve Klein-Gordon equation, it gives both positive energy solution and negative energy solution. These two solutions are responsible for positive and negative value of $\rho$ which was ...
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In the production of antiprotons with an iridium target, does the mass of the target matters?
In CERN, 0.0003% of the protons that collide with a 0.01 kg iridium plate result in antiprotons.
Wouldn't increasing the mass of the plate result in a higher collision rate? Wouldn't be proportional?
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During the production of antiprotons with an iridium target, does the target have to be replaced?
I mean, to keep producing the same amount of antiprotons for every proton beam.
If so, what's the maximum total amount of antiprotons that can be produced (not trapped) with a target with a certain ...
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Klein-Gordon particles and Feynman-Stueckelberg interpretation
The solutions of the Klein-Gordon equation for free particles are $e^{-iE_p t+i\vec{p}.\vec{x}}$ and $e^{iE_p t+i\vec{p}.\vec{x}}$ for energy eigenvalues of $E=E_p$ and $E=-E_p$ respectively. The ...
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Can we save Feynman's martian rendez-vous with $CP$ violation?
There's a short part in The Feynman Lectures where he explains the why you should never shake a martian's left hand. He introduces a "martian" who we can only communicate with in some ...
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Antimatter structures and chirality
I'm curious whether the reversal of spin number in antiparticles vis-a-vis their matter counterparts would have a corresponding reversal of the chirality of structures made of antimatter (over scales ...
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How do we know that there is matter-anti-matter asymmetry? [duplicate]
It is often said that there's more matter than anti-matter, How do we know that there is more matter,
Can't there be a galaxy made up of antihydrogen? Will that galaxy be any different from ours?
How ...
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Matter-antimatter conversion in quarks
If in beta plus decay, regular matter such as the up quark can decay into a positron, I have to wonder under high pressure, could it be possible for a quark to decay into the antiquark of its opposite?...
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Weinberg on the Dirac Equation
I am searching for a reference I read and then misplaced, in which Weinberg asserts that the Dirac equation's prediction of the positron is a characteristic of any equation which has the general form ...
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Annihilation radiation
Can photons of microwave wavelengths be emitted from electron-positron annihilation? If not, which processes, preferably other annihilations or particle collisions, produce microwave photons?
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Does CP symmetry dictates that a particle and its antiparticle behave the same when moving in opposite directions and how can I observe CP asymmetry?
I have started reading in particle physics very recently. I have been reading a bit about tau particles, and I came across the idea of CP symmetry and how it’s violation may present an explanation for ...
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Why are there no antimatter-antimatter collisions in CERN?
The labs at CERN create anti-Protons, and have collided them with Protons. Anti-Hydrogen is used to study matter-antimatter asymmetry.
Were there any attempts to collide anti-Protons with anti-Protons?...
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Dirac spinors vs. Wigner classification
As I understand, from Wigner's classification of particles it follows that for every $m > 0$ and $s \in \left\{ 0, \frac{1}{2}, 1, \frac{3}{2}, \dots \right\}$ there is an irreducible, unitary ...
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Possibility of anti-time
I was just wondering if every particle has an anti-particle (or so I've read/heard), are there other things which could be candidates to have an anti- "form" as well? My example is focused ...
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Does particle parity play any role in matter anti-matter annihilation?
If a left handed electron and a right handed antimatter electron were to meet, would they still annihilate?
In the same way, if a left handed electron and a left handed antimatter electron meet, will ...
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If the electromagnetic force did not exist before it froze out, how could there have been a meaningful distinction between matter and antimatter?
If electrons and positrons are identical except for their opposing charges, what was the nature of these particles before the EM force separated out?
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Particle and antiparticle operators in position space
I need to study the two-point correlation functions of the creation/annihilation operators of particle/antiparticle, $\hat{a}^{(\dagger)}$ and $\hat{b}^{(\dagger)}$, in position space. It is customary ...
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Interaction between an electron and an antiproton
I have read in many sources that particles and their respective antiparticles annihilate, but a particle and another particle's antiparticle (for example, an electron and an antiproton) do not. ...
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Current bounds on the value of $g$ for antimatter
In 2011, the ALPHA experiment showed that the gravitational acceleration for antihydrogen was between -65 and 110 times the normal gravitational acceleration. Has there been any improvement on the ...
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How would the universe look like without matter?
I was wondering how the universe would look like if it would have been perfectly symmetrical in terms of matter and antimatter. If I understand correctly, there would be no "particle" but ...
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