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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Measurement of the lifetimes of promptly produced Omega(0)(c) and Xi(9)(c) baryons. Sci. Bull., 67(5), 479–487.
Abstract: A measurement of the lifetimes of the Omega(0)(c) and Xi(0)(c) baryons is reported using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb(-1) collected by the LHCb experiment. The Omega(0)(c) and Xi(0)(c) baryons are produced directly from proton interactions and reconstructed in the pK(-)K(-)pi(+) final state. The Omega(0)(c) lifetime is measured to be 276.5 +/- 13.4 +/- 4.4 +/- 0.7 fs, and the Xi(0)(c) lifetime is measured to be 148.0 +/- 2.3 +/- 2.2 +/- 0.2 fs, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the D-0 lifetime. These results confirm previous LHCb measurements based on semileptonic beauty-hadron decays, which disagree with earlier results of a four times shorter Omega(c)0 lifetime, and provide the single most precise measurement of the Omega(0 )(c)lifetime.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of the mass and production rate of Xi(-)(b)( )baryons. Phys. Rev. D, 99(5), 052006–13pp.
Abstract: The first measurement of the production rate of Xi(-)(b) baryons in pp collisions relative to that of Lambda(0 )(b)baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6 fb(-1) at root s = 7, 8 and 13 TeV, respectively. In the kinematic region 2 < eta < 6 and p(T) < 20 GeV/c, we measure f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda)= (10.8 +/- 0.9 +/- 0.8) x 10(-2) [root s = 7,8 TeV], f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda) =(13.1 +/- 1.1 +/- 1.0) x 10(-2) [root s = 13 TeV], where and f(Xi b-) and f(Lambda)(b0) the fragmentation fractions of b quarks into Xi(-)(b) and Lambda(0)(b) baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of f(Xi b-)/f(Lambda b0) are obtained by invoking SU(3) symmetry in the Xi(-)(b)-> J/psi Xi(-) and Lambda(0)(b)-> J/psi Lambda decays. Production asymmetries between Xi(-)(b) and (Xi) over bar (+)(b) baryons are also reported. The mass of the Xi(-)(b) baryon is also measured relative to that of the Lambda(0)(b) baryon, from which it is found that m(Xi(-)(b)) = 5796.70 +/- 0.39 +/- 0.15 +/- 0.17 MeV/c(2), where the last uncertainty is due to the precision on the known Lambda(0)(b) mass. This result represents the most precise determination of the Xi(-)(b) mass.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of the mass difference and relative production rate of the Ωb- and Ξb- baryons. Phys. Rev. D, 108(5), 052008–16pp.
Abstract: The mass difference between the Omega -b and Xi -b baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb-1, and is found to be mo Omega -bthorn – mo Xi -bthorn 1/4 248.54? 0.51ostatthorn ? 0.38osystthorn MeV=c2. The mass of the Omega -b baryon is measured to be mo Omega -bthorn 1/4 6045.9 ? 0.5ostatthorn ? 0.6osystthorn MeV=c2. This is the most precise determination of the Omega -b mass to date. In addition, the production rate of Omega -b baryons relative to that of Xi -b baryons is measured for the first time in pp collisions, using an LHCb dataset collected at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 6 fb-1. Reconstructing beauty baryons in the kinematic region 2 < <eta> < 6 and pT < 20 GeV=c with their decays to a J=psi meson and a hyperon, the ratio f Omega- b f Xi- b tation fractions of b quarks into Omega -b and Xi -b baryons, respectively, and B represents the branching fractions of their respective decays. Bo Omega- b -> J=psi Omega -thorn x Bo Xi- b -> J=psi Xi -thorn 1/4 0.120 ? 0.008ostatthorn ? 0.008osystthorn, is obtained, where f Omega- b and f Xi -b are the fragmen-
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of the Mass Difference Between Neutral Charm-Meson Eigenstates. Phys. Rev. Lett., 122(23), 231802–10pp.
Abstract: We report a measurement of the mass difference between neutral charm-meson eigenstates using a novel approach that enhances sensitivity to this parameter. We use 2.3 x 10(6) D-0 -> K-S(0)pi(+)pi(-) decays reconstructed in proton-proton collisions collected by the LHCb experiment in 2011 and 2012. Allowing for CP violation in mixing and in the interference between mixing and decay, we measure the CP-averaged normalized mass difference x(cp)= [2.7 +/- 1.6(stat) +/- 0.4(syst)] x 10(-3) and the CP-violating parameter Delta x = [-0.53 +/- 0.70(stat) +/- 0.22(syst)] x 10(-3). The results are consistent with CP symmetry. These determinations are the most precise from a single experiment and, combined with current world-average results, yield the fast evidence that the masses of the neutral charm-meson eigenstates differ.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Measurement of the Nuclear Modification Factor and Prompt Charged Particle Production in p-Pb and pp Collisions at root s(NN )=5 TeV. Phys. Rev. Lett., 128(14), 142004–12pp.
Abstract: The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon center-of-mass energy root s(NN) = 5 TeV is studied at LHCb as a function of pseudorapidity (eta) and transverse momentum (p(T) ) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of eta between -4.8 < eta < -2.5 (backward region) and 2.0 < eta < 4.8 (forward region), and p(T) between 0.2 < p(T) < 8.0 GeV/c. The results show a suppression of charged particle production in proton-lead collisions relative to proton-proton collisions in the forward region and an enhancement in the backward region for p(T) larger than 1.5 GeV/c. This measurement constrains nuclear PDFs and saturation models at previously unexplored values of the parton momentum fraction down to 10(-6).
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