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Friday, April 27, 2012

Observation of an excited Xi(b) baryon

Schematic diagram of the decay chain explored in this analysis.
The CMS experiment has submitted a paper for publication describing the firstobservation of a new, excited beauty baryon known as the Ξ*b0, with a statistical significance of more than 5 standard deviations (5σ) above the expected background. The mass is measured to be 5945.0 ± 2.8 MeV.
in PhysOrg 

Observation of an excited Xi(b) baryon

The observation of an excited b baryon via its strong decay into Xi(b)^- pi^+ (plus charge conjugates) is reported. The measurement uses a data sample of pp collisions at sqrt(s) = 7 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5.3 inverse femtobarns. The known Xi(b)^- baryon is reconstructed via the decay chain Xi(b)^- to J/psi Xi^- to mu^+ mu^- Lambda^0 pi^-, with Lambda^0 to p pi^-. A peak is observed in the distribution of the difference between the mass of the Xi(b)^- pi^+ system and the sum of the masses of the Xi(b)^- and pi^+, with a significance exceeding five standard deviations. The mass difference of the peak is 14.84 +/- 0.74 (stat.) +/- 0.28 (syst.) MeV. The new state most likely corresponds to the Xi(b)^{*0} baryon, the J^P=3/2^+ excitation of the Xi(b)^0.
in arXiv
read more in CERN and Quantum Diaries
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