Chinese Physics C > 2016, Vol. 40 > Issue(1): 011001 DOI: 10.1088/1674-1137/40/1/011001

Study of the production of Λ_b⁰and B⁰hadrons in pp collisions and first measurement of the Λ_b⁰→J/ψpK^-branching fraction

R. Aaij^R.38,
et al (LHCb Collaboration)

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The product of the Λ _b ⁰( B ⁰) di erential production cross-section and the branching fraction of the decay Λ _b ⁰→J/ψpK ^-( B ⁰→J/ψp K ^*(892) ⁰) is measured as a function of the beauty hadron transverse momentum, pT, and rapidity, y. The kinematic region of the measurements is p _T<20 GeV/ cand 2.0< y< 4.5. The measurements use a data sample corresponding to an integrated luminosity of 3fb ^-1collected by the LHCb detector in pp collisions at centre-of-mass energies √ s= 7 TeV in 2011 and √ s= 8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio, f _{Λ_b⁰}/ f _d, the branching fraction of the decay Λ _b ⁰→J/ψpK ^-is measured to be
B(Λ _b ⁰→J/ψpK ^-)=(3.17±0.04±0.07±0.34 _-0.28 ^+0.45)×10 ^-4,
where the rst uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay B ⁰→J/ψp K ^*(892) ⁰, and the fourth is due to the knowledge of f _{Λ_b⁰}/ f _d. The sum of the asymmetries in the production and decay between Λ _b ⁰and Λ _b ⁰is also measured as a function of p _Tand y. The previously published branching fraction of Λ _b ⁰→J/ψp π ^-, relative to that of Λ _b ⁰→J/ψpK ^-, is updated. The branching fractions of Λ _b ⁰→P _c ⁺(→J/ψp)K ^-are determined.
- production cross-section,
- branching fraction,
- b hadrons,
- proton-proton collisions

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R. Aaij and et al (LHCb Collaboration). Study of the production of Λ _b ⁰and B ⁰hadrons in pp collisions and first measurement of the Λ _b ⁰→J/ψpK ^-branching fraction[J]. Chinese Physics C, 2016, 40(1): 011001. doi: 10.1088/1674-1137/40/1/011001

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Received: 2015-09-01

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Supported by CERN and national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil)

NSFC (China)

CNRS/IN2P3 (France)

BMBF, DFG, HGF and MPG (Germany)

INFN (Italy)

FOM and NWO (The Netherlands)

MNiSW and NCN (Poland)

MEN/IFA (Romania)

MinES and FANO (Russia)

MinECo (Spain)

SNSF and SER (Switzerland)

NASU (Ukraine)

STFC (United Kingdom)

NSF (USA). The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). Individual groups or members have received support from EPLANET, Marie Sklodowska-Curie Actions and ERC (European Union), Conseil generalde Haute-Savoie, Labex ENIGMASS and OCEVU, Region Auvergne (France), RFBR (Russia), XuntaGal and GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851 (United Kingdom).

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通讯作者:陈斌, bchen63@163.com

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沈阳化工大学材料科学与工程学院沈阳 110142

Study of the production of Λ_b⁰and B⁰hadrons in pp collisions and first measurement of the Λ_b⁰→J/ψpK^-branching fraction

Received Date:2015-09-01

Available Online:2016-01-20

Fund Project:Supported by CERN and national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil) NSFC (China) CNRS/IN2P3 (France) BMBF, DFG, HGF and MPG (Germany) INFN (Italy) FOM and NWO (The Netherlands) MNiSW and NCN (Poland) MEN/IFA (Romania) MinES and FANO (Russia) MinECo (Spain) SNSF and SER (Switzerland) NASU (Ukraine) STFC (United Kingdom) NSF (USA). The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). Individual groups or members have received support from EPLANET, Marie Sklodowska-Curie Actions and ERC (European Union), Conseil generalde Haute-Savoie, Labex ENIGMASS and OCEVU, Region Auvergne (France), RFBR (Russia), XuntaGal and GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851 (United Kingdom).

Abstract:The product of the Λ_b⁰(B⁰) di erential production cross-section and the branching fraction of the decay Λ_b⁰→J/ψpK^-(B⁰→J/ψpK^*(892)⁰) is measured as a function of the beauty hadron transverse momentum, pT, and rapidity,y. The kinematic region of the measurements isp_T<20 GeV/cand 2.0<y< 4.5. The measurements use a data sample corresponding to an integrated luminosity of 3fb^-1collected by the LHCb detector in pp collisions at centre-of-mass energies √s= 7 TeV in 2011 and √s= 8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio,f_{Λ_b⁰}/f_d, the branching fraction of the decay Λ_b⁰→J/ψpK^-is measured to be
B(Λ_b⁰→J/ψpK^-)=(3.17±0.04±0.07±0.34_-0.28^+0.45)×10^-4,
where the rst uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decayB⁰→J/ψpK^*(892)⁰, and the fourth is due to the knowledge off_{Λ_b⁰}/f_d. The sum of the asymmetries in the production and decay between Λ_b⁰andΛ_b⁰is also measured as a function ofp_Tandy. The previously published branching fraction of Λ_b⁰→J/ψpπ^-, relative to that of Λ_b⁰→J/ψpK^-, is updated. The branching fractions of Λ_b⁰→P_c⁺(→J/ψp)K^-are determined.

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Study of the production of Λ_b⁰and B⁰hadrons in pp collisions and first measurement of the Λ_b⁰→J/ψpK^-branching fraction

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