Abstract
Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5 fb−1, the observation of a new excited Ξb0 resonance decaying to the Ξb−π+ final state is presented. The state, referred to as Ξb(6227)0, has a measured mass and natural width of m(Ξb(6227)0)=6227.1−1.5+1.4±0.5 MeV and Γ(Ξb(6227)0)=18.6−4.1+5.0±1.4 MeV, where the uncertainties are statistical and systematic. The production rate of the Ξb(6227)0 state relative to that of the Ξb− baryon in the kinematic region 2<η<5 and pT<30 GeV is measured to be fΞb(6227)0fΞb−B(Ξb(6227)0→Ξb−π+)=0.045±0.008±0.004, where B(Ξb(6227)0→Ξb−π+) is the branching fraction of the decay, and fΞb(6227)0 and fΞb− represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed Ξb(6227)− state, along with the mass of the Ξb− baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.Received 28 October 2020Accepted 23 November 2020DOI:https://doi.org/10.1103/PhysRevD.103.012004Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2021 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Physical SystemsBottom baryonsParticles & Fields
Highlights
In the constituent quark model [1,2], baryonic states form multiplets according to the symmetry of their flavor, spin and spatial wave functions
The particle identification (PID) response of charged hadrons produced in simulated signal decays is obtained from dedicated calibration samples from the data where no PID requirements are imposed [48,49]
Charged hadrons used to reconstruct the Hb candidates are required to be significantly detached from all primary vertex (PV) in the event using the quantity χ2IP, which is the difference in χ2 of the vertex fit of a given PV when the particle is included or excluded from the fit
Summary
In the constituent quark model [1,2], baryonic states form multiplets according to the symmetry of their flavor, spin and spatial wave functions. The Ξ0b and Ξ−b states form an isodoublet of bsq bound states, where q is a u or d quark, respectively Three such isodoublets, which are neither radially nor orbitally excited, should exist [4], and include the jqs. Three of the four jqs 1⁄4 1 states have been observed through their decays to Ξ0bπ− and Ξ−b πþ final states [5,6,7] Beyond these lowest-lying Ξb states, a spectrum of heavier states is expected [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22], where there are either radial or orbital excitations among the constituent quarks.
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