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Tevatron teams clash over new physics

Research groups at the Tevatron, the proton-antiproton collider at Fermilab in Batavia, Illinois, have reached starkly different conclusions about a possible sighting of new particles beyond what is expected under the standard model of particle physics.
But today, researchers on the independent D0 experiment, also at Fermilab, announced that their data do not confirm the signal.

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Tests 'reject new particle claim'

Cross-checks on data that hinted at the discovery of a new sub-atomic particle have failed to find support for the observation.
In May, researchers working on the CDF experiment at the US Tevatron "atom smasher" announced they had detected tantalising hints of an unanticipated particle.
But independent checks using a separate experiment called DZero have not been able to corroborate the findings - dealing a blow to the idea.

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Quantum particles
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Rice physicists find reappearing quantum trios

Using atoms at temperatures colder than deep space, Rice University physicists have delivered overwhelming proof for a once-scoffed-at theory that's become a hotbed for research some 40 years after it first appeared. In a paper available online in Science, Rice's team offers experimental evidence for a universal quantum mechanism that allows trios of particles to appear and reappear at higher energy levels in an infinite progression. The triplets, often called trimers, form in special cases where pairs cannot.

"It's such a remarkable phenomena. There are examples, like the Borromean rings, where having a third component is crucial. Any two of the rings will unbind if the third is removed, and these trimers are similar. The particles want to bind, but no two can do it. They need the third one to make it happen" - team leader Randy Hulet.

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While engineers at the Large Hadron Collider (LHC) race to fix its teething problems and start looking for new particles, its ageing predecessor is refusing go silently into the night.
Last week, physicists announced that the Tevatron particle accelerator at Fermilab in Batavia, Illinois, has produced particles that they are unable to explain.

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Physicists at the Tevatron collider at Fermilab in the US, which is enjoying extended status as the worlds most powerful particle collider while CERNs Large Hadron Collider (LHC) awaits repair, have reported signals in their data that hint at the existence of new fundamental particles. Last week members of the CDF experiment, one of the Tevatrons two huge particle detectors, posted a preprint detailing a large sample of protonantiproton collisions that cannot be accounted for either by quirks of the CDF detector or by known processes in the standard model of particle physics.

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Title: Study of multi-muon events produced in p-pbar collisions at sqrt(s)=1.96 TeV
Authors: CDF Collaboration

We report a study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDFII detector. In a data set acquired with a dedicated dimuon trigger and corresponding to an integrated luminosity of 2100 pb^-1, we isolate a significant sample of events in which at least one of the muon candidates is produced outside of the beam pipe of radius 1.5cm. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe are successfully modelled by known QCD processes which include heavy flavour production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDFII detector, trigger, and event reconstruction. Several topological and kinematic properties of these events are presented in this paper. These events offer a plausible resolution to long-standing inconsistencies related to b-bbar production and decay.

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