Observation of Rare Particles May Shed Light On Why the Universe Has More Matter Than Antimatter


cosmology, antimatter,cern

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ScienceDaily (June 19, 2011) — Shortly after experiments on the Large Hadron Collider (LHC) at the CERN laboratory near Geneva, Switzerland began yielding scientific data last fall, a group of scientists led by a Syracuse University physicist became the first to observe the decays of a rare particle that was present right after the Big Bang.



By studying this particle, scientists hope to solve the mystery of why the universe evolved with more matter than antimatter.

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Hunt for dark matter closes in at Large Hadron Collider


Wednesday 26 January 2011

Physicists are closer than ever to finding the source of the Universe's mysterious dark matter, following a better than expected year of research at the Compact Muon Solenoid (CMS) particle detector, part of the Large Hadron Collider (LHC) at CERN in Geneva.


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Max Braun on Flickr



The scientists have now carried out the first full run of experiments that smash protons together at almost the speed of light.


When these sub-atomic particles collide at the heart of the CMS detector, the resultant energies and densities are similar to those that were present in the first instants of the Universe, immediately after the Big Bang some 13.7 billion years ago.


The unique conditions created by these collisions can lead to the production of new particles that would have existed in those early instants and have since disappeared.


The researchers say they are well on their way to being able to either confirm or rule out one of the primary theories that could solve many of the outstanding questions of particle physics, known as Supersymmetry (SUSY).


Many hope it could be a valid extension for the Standard Model of particle physics, which describes the interactions of known subatomic particles with astonishing precision but fails to incorporate general relativity, dark matter and dark energy.


Dark matter is an invisible substance that we cannot detect directly but whose presence is inferred from the rotation of galaxies.


Physicists believe that it makes up about a quarter of the mass of the Universe whilst the ordinary and visible matter only makes up about 5% of the mass of the Universe.


Its composition is a mystery, leading to intriguing possibilities of hitherto undiscovered physics.


Professor Geoff Hall from the Department of Physics at Imperial College London, who works on the CMS experiment, said:

"We have made an important step forward in the hunt for dark matter, although no discovery has yet been made.


These results have come faster than we expected because the LHC and CMS ran better last year than we dared hope and we are now very optimistic about the prospects of pinning down Supersymmetry in the next few years."


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Lightening the dark

About 96% of the Universe is in the form of unknown matter and energy. The rest – only 4% – is the ‘ordinary matter’ that we are made of and that makes up all the planets, the stars and the galaxies we observe. The LHC experiments have the potential to discover new particles that could make up a large fraction of the Universe.In recent years, scientists have collected various evidence of the existence of a new type of matter in the Universe. They call it ‘dark’ because it does not emit or absorb electromagnetic radiation. "One of the main proofs of its existence comes from the measurement of the rotational speed of astronomical bodies in spiral galaxies", explains Gian Giudice, a member of CERN's Theory group and the author of "A Zeptospace Odyssey", a recent book on LHC physics aimed at the general public.According to the Newtonian laws of motion, this value varies as a function of the distance from the centre of the galaxy: more distant objects should rotate at a lower speed than those situated nearer the centre. However, back in the 1970s, astronomers found that outer stars move at a higher rotational speed than expected. “With such a velocity, the attractive gravitational force exerted by the observable mass would not be enough to keep those stars in the galaxy,and stars would simply escape”, continues Gian Giudice. Therefore, something must exist that keeps the galaxy together by exerting gravitational attraction."The second strong piece of evidence suggesting the existence of dark matter comes from the 'gravitational lensing' effect, in which galactic clusters bend the light coming from more distant objects. The way the light is deviated shows that the total mass contained in the clusters must be much larger than what we observe”, explains Giudice. Moreover, studies on the way in which the initial atoms and molecules formed in the Universe show that ordinary matter cannot account for more than 4% of the Universe. This fact allows scientists to exclude the possibility that invisible matter is made of massive objects such as Jupiter-sized planets. On the other hand, theory and observations do not exclude that dark matter is made of primordial black holes in which large amounts of matter could be trapped. However, this latter possibility seems very remote, and scientists tend to think that dark matter is made of a new type of particle.How could the LHC help enlighten physicists?"The yet undiscovered dark matter has to meet some requirements imposed by observations and theory", says Gian Giudice. "It has to be stable, it has to carry no charge, and it has to be relatively heavy”.Through studies on the evolution of the Universe, scientists have been able to infer the mass of the dark matter constituents, situating it between 100 GeV and 1 TeV (for reference, the mass of the proton is about 1 GeV). Interestingly enough, this is exactly the same mass range in which theories beyond the Standard Model anticipate the existence of new particles.“The LHC will explore exactly that range of energies. Therefore, if new particles exist, the LHC has a big chance of finding them”, confirms Gian Giudice. He adds: “The theoretical supersymmetric model suggests three possible candidates for dark matter: the neutralino, the gravitino and the sneutrino. However, it is important to note that supersymmetry is not the only possible scenario".Besides the whole plethora of possible alternative scenarios, even if the LHC experiments find evidence of new particles, it will not be possible to claim that they are the actual components of dark matter. For this, confirmation will be needed from other dedicated experiments.From deep inside the Earth to outer spaceOther experiments are searching for the elusive dark matter particles. Some of them, such as the CDMS experiment at the Soudan Underground Laboratory in Minnesota, and the XENON and DAMA experiments at the Gran Sasso Laboratory in Italy, are installed underground. Others, such as Pamela and Fermi (also at Gran Sasso), are in orbit around our planet.by Francesco PoppiCopyright CERN 2010 - CERN Publications, DG-COhttp://cdsweb.cern.ch/journal/CERNBulletin/2010/18/News%20Articles/1261775?ln=enbild_LHC_Cern



For many years, the absence of antimatter in the Universe has tantalised particle physicists and cosmologists: while the Big Bang should have created equal amounts of matter and antimatter, we do not observe any primordial antimatter today. Where has it gone? The LHC experiments have the potential to unveil natural processes that could hold the key to solving this paradox. Every time that matter is created from pure energy, equal amounts of particles and antiparticles are generated. Conversely, when matter and antimatter meet, they annihilate and produce light. Antimatter is produced routinely when cosmic rays hit the Earth's atmosphere, and the annihilations of matter and antimatter are observed during physics experiments in particle accelerators. If the Universe contained antimatter regions, we would be able to observe intense fluxes of photons at the boundaries of the matter/antimatter regions. “Experiments measuring the diffuse gamma-ray background in the Universe would be able to observe these light emissions”, confirms Antonio Riotto of CERN's Theory group. “In the absence of such evidence, we can conclude that matter domains are at least the size of the entire visible Universe”, he adds. What caused the disappearance of antimatter in favour of matter? “In 1967, the Russian physicist Andrej Sakharov pointed out that forces discriminating between matter and antimatter, called “CP-violating” effects, could have modified the initial matter-antimatter symmetry when deviations from the thermal equilibrium of the Universe occured”, says Antonio Riotto. In the cold Universe today, we can only observe very rare CP-violating effects in which Nature prefers the creation of matter over antimatter. Following their discovery in the decays of K-mesons containing strange quarks, they have now also been observed in the decays of B mesons, which contain bottom quarks. Today, scientists think that the early Universe might have gone through a transition phase in which the thermodynamic equilibrium was broken, when the density of the Universe was very high and the average temperature was one billion or more times that inside the Sun. "Some physicists think that this might have happened through the formation of ‘bubbles’ which have progressively expanded, thus ‘imposing’ their new equilibrium on the whole pre-existent Universe", explains Antonio Riotto. Whatever the real dynamics of this phase actually were, the important thing is that one particle of matter in every 10 billion survived, while all the others annihilated with the corresponding antiparticles. How can the LHC help to solve the mystery? By studying rare decays, experiments can bring us more accurate information about phenomena related to CP-violation involving both known and new particles, such as mesons containing both bottom and strange quarks. Moreover, if new supersymmetric particles are discovered at the LHC, some of the possible scenarios leading to a non-equilibrium phase could find experimental support. "If the LHC finds a Higgs boson with a mass less than about 130 GeV, and if this discovery comes with the detection of a light supersymmetric particle called ‘stop‘, this could be the experimental proof that the non-equilibrium phase happened through the formation of bubbles", concludes Antonio Riotto. In any case, since the disappearance of primordial antimatter cannot be explained by the current Standard Model theory, it is clear that we have to look for something new. Scientists are exploring different avenues but, given the fact that what we observe represents only about 4% of the total energy and matter that the Universe is made of, one can guess that part of the key to solving the antimatter mystery could be held in the yet unknown part of the Universe. With its very high discovery potential, the LHC will certainly help shed light on the whole issue.antimatterCOPYRIGHT CERN BULLETIN URL :http://cdsweb.cern.ch/journal/CERNBulletin/2010/16/News%20Articles/1255394?ln=en


The LHC is asking some Big Questions about the universe we live in

How did our universe come to be the way it is? The Universe started with a Big Bang – but we don’t fully understand how or why it developed the way it did. The LHC will let us see how matter behaved a tiny fraction of a second after the Big Bang. Researchers have some ideas of what to expect – but also expect the unexpected!What kind of Universe do we live in? Many physicists think the Universe has more dimensions than the four (space and time) we are aware of. Will the LHC bring us evidence of new dimensions? Gravity does not fit comfortably into the current descriptions of forces used by physicists. It is also very much weaker than the other forces. One explanation for this may be that our Universe is part of a larger multi dimensional reality and that gravity can leak into other dimensions, making it appear weaker. The LHC may allow us to see evidence of these extra dimensions - for example, the production of mini-black holes which blink into and out of existence in a tiny fraction of a second.What happened in the Big Bang? What was the Universe made of before the matter we see around us formed? The LHC will recreate, on a microscale, conditions that existed during the first billionth of a second of the Big Bang.At the earliest moments of the Big Bang, the Universe consisted of a searingly hot soup of fundamental particles - quarks, leptons and the force carriers. As the Universe cooled to 1000 billion degrees, the quarks and gluons (carriers of the strong force) combined into composite particles like protons and neutrons. The LHC will collide lead nuclei so that they release their constituent quarks in a fleeting ‘Little Bang’. This will take us back to the time before these particles formed, re-creating the conditions early in the evolution of the universe, when quarks and gluons were free to mix without combining. The debris detected will provide important information about this very early state of matter.Where is the antimatter? The Big Bang created equal amounts of matter and antimatter, but we only see matter now. What happened to the antimatter?Every fundamental matter particle has an antimatter partner with equal but opposite properties such as electric charge (for example, the negative electron has a positive antimatter partner called the positron). Equal amounts of matter and antimatter were created in the Big Bang, but antimatter then disappeared. So what happened to it? Experiments have already shown that some matter particles decay at different rates from their anti-particles, which could explain this. One of the LHC experiments will study these subtle differences between matter and antimatter particles.Why do particles have mass? Why do some particles have mass while others don’t? What makes this difference? If the LHC reveal particles predicted by theory it will help us understand this. Particles of light (known as photons) have no mass. Matter particles (such as electrons and quarks) do – and we’re not sure why. British physicist, Peter Higgs, proposed the existence of a field (the Higg’s Field), which pervades the entire Universe and interacts with some particles and this gives them mass. If the theory is right then the field should reveal itself as a particle (the Higg’s particle). The Higg’s particle is too heavy to be made in existing accelerators, but the high energies of the LHC should enable us to produce and detect it.What is our Universe made of? Ninety-six percent of our Universe is missing! Much of the missing matter is stuff researchers have called ‘dark matter’. Can the LHC find out what it is made of?The theory of ‘supersymmetry’ suggests that all known particles have, as yet undetected, ‘superpartners’. If they exist, the LHC should find them. These ‘supersymmetric’ particles may help explain one mystery of the Universe – missing matter. Astronomers detect the gravitational effects of large amounts of matter that can’t be seen and so is called ‘Dark Matter’. One possible explanation of dark matter is that it consists of supersymmetric particles.Copyright http://www.lhc.ac.uk/the-big-questions.htmlLHC_hall


Het heelal onderzoeken op aarde in het CERN

In het CERN is de Large Hadron Collider (LHC) en o.a. de Atlas geïnstalleerd en klaar om in gebruik te nemen. Het gaat om een zoektocht naar elementaire deeltjes die men tot op heden niet heeft kunnen waarnemen...Een zoektocht naar het Higgs deeltje (deeltje dat massa heeft aan de andere gekende deeltjes) en naar donkere materie deeltjes...Het wordt een boeiende zoektocht en hopelijk slaagt men erin om het vooropgestelde te ontdekken. Wat is jou mening hierover ? Geloof je in de kennis die het CERN heeft en de nu geïnstalleerde apparatuur ? Of denk je dat het maar niks wordt ? Weer een geldverslindend wetenschappelijk project ...??? Graag je reactie hierop ...lhc