# Observation of $J/ψp$ resonances consistent with pentaquark states in ${Λ_b^0\to J/ψK^-p}$ decays

Abstract : Observations of exotic structures in the J/ψp channel, that we refer to as pentaquark-charmonium states, in Λ0b→J/ψK−p decays are presented. The data sample corresponds to an integrated luminosity of 3/fb acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis is performed on the three-body final-state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29 MeV and a width of 205±18±86 MeV, while the second is narrower, with a mass of 4449.8±1.7±2.5 MeV and a width of 39±5±19 MeV. The preferred JP assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
Type de document :
Article dans une revue
Physical Review Letters, American Physical Society, 2015, 115, pp.072001. 〈10.1103/PhysRevLett.115.072001〉

http://hal.in2p3.fr/in2p3-01177045
Contributeur : Claudine Bombar <>
Soumis le : jeudi 16 juillet 2015 - 14:48:43
Dernière modification le : jeudi 11 janvier 2018 - 06:14:21

### Citation

R. Aaij, L. Beaucourt, M. Chefdeville, D. Decamp, N. Déléage, et al.. Observation of $J/ψp$ resonances consistent with pentaquark states in ${Λ_b^0\to J/ψK^-p}$ decays. Physical Review Letters, American Physical Society, 2015, 115, pp.072001. 〈10.1103/PhysRevLett.115.072001〉. 〈in2p3-01177045〉

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