# B Properties of antimatter?

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1. Dec 21, 2016

### hsdrop

do we know what the proportions of antimatter is compared to matter ?? like does gravity electromagnetism the strong and weak forces exc.....as well as other thing like does it react to it self the same way matter does to it self??

2. Dec 21, 2016

### Simon Bridge

In the observable Universe, matter vastly outnumbers antimatter ... but, within experiments, antimatter is always accompanied by an equal amount of matter.
Antimatter has the same interactions as regular matter, including the self-interaction ... however, there is this thing called the CP violation which may explain the dominance of matter over antimatter.

Thus: if you search using "CP violation" among your terms, you will find lots of information on the subects you are asking about.

3. Dec 22, 2016

### Orodruin

Staff Emeritus
It is worth mentioning that this is not due to a large asymmetry between matter and antimatter. In the early universe, there was almost equal amounts. What happened was that there was a slight excess of matter and when matter and antimatter annihilated away, this small excess was left as it had nothing to annihilate with. This small excess is all the matter we see today.

As far as we are aware, gravity, electromagnetism, and the strong force affect matter and antimatter in the same way. The weak force displays CP violation. It is worth noticing that the observed CP violation in the weak force is not sufficient to explain why there was slightly more matter in the early universe. This indicates that there should exist another source of CP violation that we do not know about (yet!). This is an open field of research.

4. Jan 30, 2018

### Kagrat

Go to this link and watch this video. It will make you understand more.

5. Feb 1, 2018

### ChrisVer

In general no, we don't. We only know that we love in a matter-dominated (dominated in the sense of matter-antimatter) world. Experiments, like PAMELA, aim in measuring such an asymmetry in the Universe. PAMELA aimed to do that by measuring the flux of antimatter in cosmic rays which would come from the residual antimatter from the Big Bang. As far as I know PAMELA did not observe any kind of primary cosmic ray antiproton result (https://arxiv.org/pdf/1801.10310.pdf Fig.13 and paragraph under it).

Yes most of the times, except for if there is CP-violation in the game. In the CP violation scenario, matter and antimatter interactions differ.
One nice example is shown in this beautiful plot from Babar:

The idea is that you have the production of $B_{\text{tag}}^0\bar{B}^0$ mesons... and you measure the $B_{\text{tag}}^0$ meson's evolution over time (compared to the $\bar{B}^0$)..The nice thing with the neutral B mesons is that there is a possible transition $B\rightarrow \bar{B} \rightarrow B^0 \rightarrow ...$ etc. Now you can measure how much time it takes the $B_\text{tag}^0$ to decay (and also see if it decays as a $B$ or $\bar{B}$) ($t$ or $t'$ respectively) and compare it to the time of decay of $\bar{B}^0$ ($\bar{t}$).
Then you have this variable $\Delta t = \bar{t} - t$ (blue markers) or $=\bar{t}-t'$ (red-markers) (so if the tag decays second, the time difference is negative).
The fact that the $B^0_\text{tag}$ and $\bar{B}_\text{tag}^0$ have so different $\Delta t$ (their asymmetry is shown in the bottom panel) is obviously due to different behavior between matter $B^0_\text{tag}$ and antimatter $\bar{B}^0_\text{tag}$

One day.... Until that one day, when axions are observed...