Where has all the anti-matter gone?

[Psnarf]

A new discovery at the Large Hadron Collider at Cern reveals another difference between matter and antimatter.
http://www.bbc.co.uk/news/science-environment-22278389

How do we measure anti-matter outside of the heliopause? My guess is that any anti-matter particle that gets into the heliosphere is more than likely to interact with particles in the solar wind and annihilate. With a density of over 20 protons/cm³ near Earth during a mild solar storm, anti-matter particles couldn't get close enough for detection. How are anti-matter particles detected? Maybe there are clouds of anti-matter particles that we interpret as dark matter?

[Chris Peterson]

A new discovery at the Large Hadron Collider at Cern reveals another difference between matter and antimatter.
http://www.bbc.co.uk/news/science-environment-22278389

How do we measure anti-matter outside of the heliopause? My guess is that any anti-matter particle that gets into the heliosphere is more than likely to interact with particles in the solar wind and annihilate. With a density of over 20 protons/cm³ near Earth during a mild solar storm, anti-matter particles couldn't get close enough for detection. How are anti-matter particles detected? Maybe there are clouds of anti-matter particles that we interpret as dark matter?

There is no reason that we would confuse antimatter for dark matter. Antimatter interacts with EM just like all ordinary matter, meaning it would be visible. Almost certainly, the reason we don't see antimatter clouds is because they don't exist.

[neufer]

A new discovery at the Large Hadron Collider at Cern reveals another difference between matter and antimatter.
http://www.bbc.co.uk/news/science-environment-22278389

How do we measure anti-matter outside of the heliopause?

• 511 keV gamma rays.
  
  . http://en.wikipedia.org/wiki/Annihilation
  . http://asterisk.apod.com/viewtopic.php?t=29776

22 Jul 2009

[b][color=#0000FF]INTEGRAL's map of the Galaxy at 511 keV. Credit: ESA/ INTEGRAL/ MPE[/color][/b]

---

<<INTEGRAL's all-sky map of the 511 keV line emission has been used to conclude that dark matter is not the origin of galactic positron annihilation, contrary to what had been assumed in past years. In a recent paper published in Physical Review Letters Richard Lingenfelter and colleagues argue that no exotic sources are required to explain the spatial and spectral features observed by INTEGRAL.

Since its detection almost 40 years ago on a balloon experiment, the 511 keV line emission from the centre of the Milky Way has been a constant source of theoretical and observational attention.

The line emission and the associated positronium continuum have always appeared to be spatially extended, coinciding with the galactic bulge, the halo, and the inner galactic disk.

That there should be abundant production of positrons in the Galaxy has long been known: the beta decay of radionuclei 56Ni, 44Ti, and 26Al in supernova ejecta and winds of Wolf Rayet stars is well understood, and can easily account for the complete supply of positrons required to account for the observed gamma-ray flux.

Recently, the analysis of more than 50 million seconds of data collected by INTEGRAL produced a detailed map of the 511 keV emission from the centre of our Galaxy. The increase in spectral and spatial resolution delivered by the INTEGRAL instruments (significantly above that of previous gamma-ray detectors) reveals that the emission is strongly peaked towards the centre of the Galaxy, with an asymmetry along the galactic disk (see Weidenspointner et al 2008a,b). Additionally, the ratio of the luminosity of bulge to that of the disk is found to be 4 times higher than that of the Galactic supernovae, the main source of the positrons.

For many years the underlying assumption in the interpretation of the 511-keV data has been that the positrons annihilate close to their sources because the conditions they encounter are such that they cannot propagate for very long distances. Based on this assumption, the expectation is that the distribution of the radiation will closely match the distribution of the sources.

The large discrepancy between the distribution of the assumed sources and that of the radiation brought to light by INTEGRAL has therefore triggered a search for new objects able to produce positrons in a region of the Galaxy devoid of any known sources of positrons. Exotic dark matter objects like new axinos, Q balls, millicharged fermions, and many more have been suggested as possible new sources of positrons in the bulge.

In a paper published in the 17 July issue of Physical Review Letters Richard Lingenfelter and his colleagues James Higdon and Richard Rothschild restore order in the discussion. The main point made by the authors is that it is incorrect to assume that positrons cannot propagate over large distances, which was the central motivation behind the dark matter hypothesis. Just like cosmic ray electrons of the same energy in fact, positrons can travel unhindered over kiloparsec-scale distances because, as the authors show, their interaction with the magnetic fluctuations across most of the Galaxy is too weak to affect them significantly.

Having removed the obstacle to the propagation of the positrons, the authors are now able to explain the observed flux ratio in terms of classical sources of positrons. Additionally, allowing for the propagation of positrons makes it possible to explain another feature of the radiation, namely the ratio between the 511 line flux and the positronium continuum, an aspect neglected by the dark matter solutions to the problem. In an accompanying paper published in the Astrophysical Journal, the authors show that the observed asymmetry can be explained by the asymmetry of the Galactic spiral arm as seen from the Solar System, finally putting to rest the need to invoke an exotic explanation for the experimental observations.>>

[bystander]

LHCb experiment observes new matter-antimatter difference
CERN | Large Hadron Collider beauty (LHCb) | 2013 Apr 24

The LHCb collaboration at CERN today submitted a paper to Physical Review Letters on the first observation of matter-antimatter asymmetry in the decays of the particle known as the B⁰_s. It is only the fourth subatomic particle known to exhibit such behaviour.

Matter and antimatter are thought to have existed in equal amounts at the beginning of the universe, but today the universe appears to be composed essentially of matter. By studying subtle differences in the behaviour of particle and antiparticles, experiments at the LHC are seeking to cast light on this dominance of matter over antimatter.

Now the LHCb experiment has observed a preference for matter over antimatter known as CP-violation in the decay of neutral B⁰_s particles. ...

First observation of CP violation in the decays of B_s mesons - LHCb collaboration

• arXiv.org > hep-ex > arXiv:1304.6173 > 23 Apr 2013

CP Violation and the Information/Anti-Information Asymmetry
Preposterous Universe | Sean Carroll | 2013 Apr 24

[MargaritaMc]

Antimatter results emerge at LHC - but puzzle abides
By Jason Palmer
Science and technology reporter, BBC News
24 April 2013 Last updated at 13:55

The quest to understand why our Universe is made of matter rather than antimatter has received a boost at the Large Hadron Collider.

The LHCb experiment has for the first time observed decays of particles known as Bs mesons that preferentially end up as matter, rather than antimatter.

However, the difference is still not enough to explain the preponderance of matter over antimatter in the cosmos.

The work, published online, has been submitted to Physical Review Letters.

Every member of the zoo of particles we know about has an antimatter cousin, identical in every way except for an opposite electric charge - the electrons and protons that in part make us up have positrons and antiprotons as their antimatter matches.

The current theory for how the Universe got its start holds that equal amounts of matter and antimatter were initially created. But whenever the two meet, they destroy each other in a flash of light.

Simply put, the Universe should have come to a blazing end just then. Something must have made for a slight excess of matter in order to lead to the matter-dominated Universe we see today.

It is the subtle details of this preference for matter that the LHCb experiment is hunting for as it tracks particles created when protons are smashed together.

Just like the long-running hint for the particle called the Higgs boson, clues arise in the showers of particles created by these violent collisions.

'Puzzle continues'

Previous work at the LHCb had seen hints of an excess of matter - called CP violation - in combinations of the fundamental particles called quarks.

At other experiments around the world, the family of particles called mesons had been tackled, and small amounts of CP violation had been seen in two of the four meson types that have no electric charge.

A third type, D0 mesons, showed early hints of CP violation at LHCb in 2011, but more recent studies suggest those hints were mistaken.

"If one decays more often to this final state... than the other one, then it shows a fundamental difference between matter and antimatter," said Chris Parkes of the University of Manchester, spokesperson for the UK contingent of the LHCb collaboration.

"That's what we've seen - a difference of about one in four of these decays," he told the BBC.

But that difference still neatly fits within existing theory - the Standard Model - leaving a mystery unresolved.

"However, the amount that we see is still compatible with the amount inside the Standard Model picture of particle physics, and this amount is just simply too small to explain why we're all here, and why everything is still made of matter - so the puzzle still continues."

The answer to that puzzle will require considering different ways in which these particles and others decay into yet more particles from the zoo that may finally show enough CP violation to close the antimatter question.

"The last thing people want is long lists of particle names - one's got to relate it to the bigger picture, and I think today is sort of a milestone in that picture - it's the first time that we've seen anything in Bs mesons," Prof Parkes told BBC News.
http://bbc.co.uk/news/science-environment-22277685

http://arxiv.org/abs/1304.6173
http://www.sciencedaily.com/releases/20 ... 094512.htm

http://en.m.wikipedia.org/wiki/CP_violation
In particle physics, CP violation (CP standing for Charge Parity) is a violation of the postulated CP-symmetry (or Charge conjugation Parity symmetry): the combination of C-symmetry (charge conjugation symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle were interchanged with its antiparticle (C symmetry), and then left and right were swapped (P symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

It plays an important role both in the attempts of cosmology to explain the dominance of matter over antimatter in the present Universe, and in the study of weak interactions in particle physics.

[JohnD]

Sad that even a specialist journalist can't get it right:
"Every member of the zoo of particles we know about has an antimatter cousin, identical in every way except for an opposite electric charge"
He goes on to cite positrons and antiprotons, but seems to think it's just a matter of charge.

Or else he was trying to keep it simple!

John