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تسجيل مستخدم جديدObservation of a new $Xi_b^-$ resonance
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From samples of $pp$ collision data collected by the LHCb experiment at $sqrt{s}=7$, $8$ and $13$ TeV corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb$^{-1}$, respectively, a peak in both the $Lambda_b^0K^-$ and $Xi_b^0pi^-$ invariant mass spectra is observed. In the quark model, radially and orbitally excited $Xi_b^-$ resonances with quark content $bds$ are expected. Referring to this peak as $Xi_b(6227)^-$, the mass and natural width are measured to be $m_{Xi_{b}(6227)^-}=6226.9pm2.0pm0.3pm0.2$ MeV/$c^2$ and $Gamma_{Xi_b(6227)^-}=18.1pm5.4pm1.8$ MeV/$c^2$, where the first uncertainty is statistical, the second is systematic, and the third, on $m_{Xi_b(6227)^-}$, is due to the knowledge of the $Lambda_b^0$ baryon mass. Relative production rates of the ${Xi_b(6227)^-toLambda_b^0K^-}$ and ${Xi_b(6227)^-toXi_b^0pi^-}$ decays are also reported.
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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 $Xi_b^0$ resonance decaying to the $Xi_b^-pi^+$ final state is presented. The s
tate, referred to as $Xi_b(6227)^0$, has a measured mass and natural width of $m(Xi_b(6227)^0) = 6227.1^{,+1.4}_{,-1.5}pm0.5$ MeV, $Gamma(Xi_b(6227)^0) = 18.6^{,+5.0}_{,-4.1}pm1.4$ MeV, where the uncertainties are statistical and systematic. The production rate of the $Xi_b(6227)^0$ state relative to that of the $Xi_b^-$ baryon in the kinematic region $2<eta<5$ and $p_{rm T}<30$ GeV is measured to be $frac{f_{Xi_b(6227)^0}}{f_{Xi_b^-}}{mathcal{B}}(Xi_b(6227)^0toXi_b^-pi^+) = 0.045pm0.008pm0.004$, where ${mathcal{B}}(Xi_b(6227)^0toXi_b^-pi^+)$ is the branching fraction of the decay, and $f_{Xi_b(6227)^0}$ and $f_{Xi_b^-}$ represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed $Xi_b(6227)^-$ state, along with the mass of the $Xi_b^-$ baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.
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