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Observation of a new Xi(b) baryon

Abstract : 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.
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Contributor : Sylvie Flores <>
Submitted on : Friday, April 27, 2012 - 7:31:23 AM
Last modification on : Wednesday, January 6, 2021 - 6:44:02 PM

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S. Chatrchyan, M. Besancon, S. Choudhury, M. Dejardin, D. Denegri, et al.. Observation of a new Xi(b) baryon. Physical Review Letters, American Physical Society, 2012, 108, pp.252002. ⟨10.1103/PhysRevLett.108.252002⟩. ⟨in2p3-00691794⟩



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