New source of asymmetry between matter and antimatter

New source of asymmetry between matter and antimatter
A view of the LHCb experimental cavern. Credit: Maximilien Brice/CERN

The LHCb experiment has found hints of what could be a new piece of the jigsaw puzzle of the missing antimatter in our universe. They have found tantalising evidence of a phenomenon dubbed charge-parity (CP) violation in particles known as baryons – a family of particles whose best-known members are the protons and neutrons that make up all the matter in the universe.

The idea that the baryons made of matter behave exactly like their antimatter counterparts is related to the idea of CP symmetry. Any violation of this symmetry would imply that the laws of physics are not the same for matter and .

This is important because a detailed understanding of how this symmetry is violated in nature can contribute to explaining the overwhelming excess of matter over antimatter observed in our universe, despite the fact that the Big Bang should have created equal amounts of matter and antimatter in the first place.

The Standard Model (SM) of particle physics predicts that a tiny amount of CP violation exists also in the baryon sector. Although CP-violating processes have been studied for over 50 years, no significant effects had been seen with baryonic particles. Moreover, CP violation as described in the SM is not large enough to account for the much larger matter-antimatter unbalance. Therefore, other CP violation sources must contribute, and one of the main goals of LHCb is precisely to search for new sources of CP violation.

The new LHCb result is based on an analysis of data collected during the first three years of the Large Hadron Collider (LHC) operations. Among all the possible short-living particles created as a result of a proton-proton collision, the collaboration compared the behavior of the Λb0 baryon and its antimatter counterpart, Λb0-bar, when they decay into a proton (or antiproton) and three charged called pions. This process is extremely rare and has never previously been observed. The high production rate of these baryons at the LHC and the specialised capabilities of the LHCb detector allowed the collaboration to collect a pure sample of around 6000 such decays.

The LHCb collaboration compared the distribution of the four decay products of the Λb0and Λb0-bar baryons and computed specific quantities that are sensitive to the CP symmetry. Any significant difference, or asymmetry, between such quantities for the matter and cases would be a manifestation of CP violation.

The LHCb data revealed a significant level of asymmetries in those CP-violation-sensitive quantities for the Λb0 and Λb0-bar baryon decays, with differences in some cases as large as 20 percent.

Overall, the statistical significance – which is how physicists refer to the probability that this result hasn't occurred by chance – is at the level of 3.3 standard deviations, and a discovery is claimed when this value reaches five standard deviations. These results, published today in Nature Physics, will soon be updated with the larger data set collected so far during the second run of the LHC. If this earlier evidence for CP violation is seen again with greater significance in the larger sample, the result will be an important milestone in the study of CP violation.


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More information: R. Aaij et al. Measurement of matter–antimatter differences in beauty baryon decays, Nature Physics (2017). DOI: 10.1038/nphys4021
Journal information: Nature Physics

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Citation: New source of asymmetry between matter and antimatter (2017, January 31) retrieved 21 August 2019 from https://phys.org/news/2017-01-source-asymmetry-antimatter.html
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KBK
Jan 31, 2017
CP violation exists within our notice every where and every when.

It exists as the experience of unidirectional time.

Oh. Wait... We can't really describe time on it's own. Time is a bit of a paradox. Hmmm.

Time is apparently 'emergent'. Time is relational, or differential. Two to tango.

We have all the evidence that could possibly be required to illustrate that CP violation is all encompassing in the human experience.

Why some cannot make that simple connection, is a bit of a mystery.

Jan 31, 2017
Please be aware that Einstein's relativity has been disproved both theoretically and experimentally (see "Challenge to the special theory of relativity" March 1, 2016 Physics Essays). The most obvious and indisputable evidence is the absolute time shown by the universally synchronized clocks on the GPS satellites which are moving with huge velocities relative to each other (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks.) while special relativity claims that time is relative (i.e. different on different reference frame) and can never be synchronized on clocks with relative velocities.

That is, the Standard Model of particles is wrong and should be abandoned in order to avoid its misleading.

Jan 31, 2017
Time is not a physical entity. It emerges from Energy and causality. An energy particle is just an excitation on a discrete field propagating thanks to the interaction with another discrete field. Time emerges as the number of these interactions between two events. Example: An EM wave is caused by an excitation in an electrical field wich then causes magnetic field to change which then causes electrical field to change again and so, thus creating the wave pattern. The primary "time" is just the total number of these "then". But you can not measure it as this happens at plank scale. What you can measure is only the number of wave peaks, which is different. Waves can be warped and are reference frame dependent. What exist is space, energy and causality, not time. And the speed of light is just the speed of causality

Feb 01, 2017
Anyone got any idea on how they are able to rule out any impact from the experiment being performed in an environment consisting of mostly matter (and vice versa, if this experiment would be done in an antimatter environment would you see the same results or the opposite?)

I read the positron was detected in a cloud chamber which made me wonder how all these other particles are detected, can we be sure that the detection mechanism is not somehow interfering with the results?

Very interesting subject.

Feb 01, 2017
if this experiment would be done in an antimatter environment would you see the same results or the opposite?

Depends on what you're looking at. The gammas would be the same (since mass of particles and antoparticles are identical). Created secondary particles would be charge reversed (you also get products with opposite baryon/lepton numbers).

The point of these experiments is to see whether you'd get *exactly* these result or a slight deviation.

Feb 01, 2017
Just say anything when what you are talking about does not exist. No particles exist, only the field. How can you define diametrical spherical fields that exist from the center to infinity as anti? or define particles that are made of particles and still be inline with your entire measurement system based upon Maxwell where only charge exist. Recall that "mass" is only an experimental constant and modern physics is theory supported by erroneous empirical interpretations. Let's begin with an optical connector that sends a clear signal with a 2 nano-second delay. Well, in my instrumentation this does not apply! It's fantasy!

Feb 03, 2017
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