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Paper   IPM / Particles / 12405
School of Particles and Accelerator
  Title:   Observation of an excited Xi(b) baryon
  Author(s): 
1.  Hessamadin Arfaei
2.  Hamed Bakhshiansohi
3.  Seyed Mohsen Etesami
4.  Ali Fahim
5.  Majid Hashemi
6.  Hoda Hesari
7.  Abideh Jafari
8.  Mohsen Khakzad
9.  A Mohammadi
10.  Mojtaba Mohammadi Najafabadi
11.  Saeid Paktinat
12.  Batool Safarzadeh
13.  Maryam Zeinali
  Status:   Published
  Journal: Phys. Rev. Lett.
  No.:  252002
  Vol.:  108
  Year:  2012
  Supported by:  IPM
  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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