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 ...
Foutch Levi's user avatar
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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 ...
Kevin Kostlan's user avatar
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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 ...
Kaushal Timilsina's user avatar
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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 ...
Vincent's user avatar
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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 ...
Juan Perez's user avatar
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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-...
cav3's user avatar
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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 ...
The Shepard's user avatar
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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) ...
Tomas McIlroy's user avatar
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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^{\...
Bababeluma's user avatar
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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 ...
Curiosity_killing_me's user avatar
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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 ...
manubrio's user avatar
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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....
Grchinook's user avatar
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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 ...
Wayne's user avatar
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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 ...
John Eastmond's user avatar
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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 ...
Nancy Hope's user avatar
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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?
BananaRepublic's user avatar
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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" ...
user371157's user avatar
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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 ...
Arnaldo Maccarone's user avatar
4 votes
1 answer
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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 ...
vyali's user avatar
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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 ...
Antonio De Angelis's user avatar
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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 ...
niket's user avatar
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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 ...
James's user avatar
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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 ...
Shep's user avatar
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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 ...
g s's user avatar
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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 ...
Pradyuman's user avatar
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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?...
Jungwoon Song's user avatar
3 votes
1 answer
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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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5 answers
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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?
Hadi's user avatar
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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 ...
Belal Bahaa's user avatar
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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 ...
Jannik Pitt's user avatar
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4 answers
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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 ...
David Motlagh's user avatar
2 votes
2 answers
158 views

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 ...
NonPartisanObservor's user avatar
1 vote
2 answers
51 views

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?
blacktopshaman's user avatar
1 vote
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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 ...
TopoLynch's user avatar
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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. ...
random person's user avatar
5 votes
2 answers
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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 ...
Charles's user avatar
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6 votes
1 answer
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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 ...
Redirectk's user avatar
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