LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Study of Gamma production in pPb collisions at root s(NN) = 8.16 TeV. Journal of High Energy Physics, 11(11), 194–36pp.
Abstract: The production of (nS) mesons (n = 1; 2; 3) in p Pb and Pb p collisions at a centre-of-mass energy per nucleon pair p sNN = 8 : 16TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb. The (nS) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the di ff erential production cross-sections of the (1 S) and (2 S) states, their forward-to-backward ratios and nuclear modi fi cation factors. The measurements are performed as a function of the transverse momentum pT and rapidity in the nucleon-nucleon centre-of-mass frame y of the (nS) states, in the kinematic range pT < 25 GeV/ c and 1 : 5 < y < 4 : 0 (5 : 0 < y < 2 : 5) for p Pb (Pb p) collisions. In addition, production cross-sections for (3 S) are measured integrated over phase space and the production ratios between all three (nS) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of the prompt-production cross-section ratio sigma(chi(c2))/sigma(chi(c1)) in pPb collisions at root s(NN)=8.16 TeV. Phys. Rev. C, 103(6), 064905–10pp.
Abstract: This article reports the first measurement of prompt chi(c1) and chi(c2) charmonium production in nuclear collisions at Large Hadron Collider energies. The cross-section ratio sigma(chi(c2))/sigma(chi(c1)) is measured in pPb collisions at root s(NN) = 8.16 TeV, collected with the LHCb experiment. The chi(c1,2) states are reconstructed via their decay to a J/psi meson, subsequently decaying into a pair of oppositely charged muons, and a photon, which is reconstructed in the calorimeter or via its conversion in the detector material. The cross-section ratio is consistent with unity in the two considered rapidity regions. Comparison with a corresponding cross-section ratio previously measured by the LHCb Collaboration in pp collisions suggests that chi(c1) and chi(c2) states are similarly affected by nuclear effects occurring in pPb collisions.
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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). Search for Rare Decays of D0 Mesons into Two Muons. Phys. Rev. Lett., 131(4), 041804–13pp.
Abstract: A search for the very rare D^{0}mu^{+}mu^{-} decay is performed using data collected by the LHCb experiment in proton-proton collisions at sqrt[s]=7, 8, and 13TeV, corresponding to an integrated luminosity of 9fb^{-1}. The search is optimized for D^{0} mesons from D^{*+}D^{0}pi^{+} decays but is also sensitive to D^{0} mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at B(D^{0}mu^{+}mu^{-})<3.1*10^{-9} at a 90% C.L. This represents the world's most stringent limit, constraining models of physics beyond the standard model.
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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). Test of lepton flavor universality using B0→D*−τ+ντ decays with hadronic τ channels. Phys. Rev. D, 108, 012018–18pp.
Abstract: The branching fraction B(B0→D*−τ+ντ) is measured relative to that of the normalization mode B0→D*−π+π−π+ using hadronic τ+→π+π−π+(π0)¯ντ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb−1. The measured ratio is B(B0→D*−τ+ντ)/B(B0→D*−π+π−π+)=1.70±0.10+0.11−0.10, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0→D*−π+π−π+ and B0→D*−μ+νμ modes, the lepton universality test R(D*−)≡B(B0→D*−τ+ντ)/B(B0→D*−μ+νμ) is calculated, R(D*−)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.
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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). First observation of the B+→D+sD−sK+ decay. Phys. Rev. D, 108, 034012–14pp.
Abstract: The B+→D+sD−sK+ decay is observed for the first time using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. Its branching fraction relative to that of the B+→D+D−K+ decay is measured to be B(B+→D+sD−sK+)B(B+→D+D−K+)=0.525±0.033±0.027±0.034, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the D±s→K∓K±π± and D±→K∓π±π± decays. This measurement fills an experimental gap in the knowledge of the family of Cabibbo-favored ¯b→¯cc¯s transitions and opens the path for unique studies of spectroscopy in future.
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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). Search for K0S(L)→μ+μ−μ+μ− decays at LHCb. Phys. Rev. D, 108, L031102–12pp.
Abstract: A search for K0S(L)→μ+μ−μ+μ− decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb−1. No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(K0S→μ+μ−μ+μ−)<5.1×10−12 and B(K0L→μ+μ−μ+μ−)<2.3×10−9.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Evidence for Exotic Hadron Contributions to Lambda(0)(b) -> J/psi p pi(-) Decays. Phys. Rev. Lett., 117(8), 082003–10pp.
Abstract: A full amplitude analysis of Lambda(0)(b) -> J/psi pi(-) decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb(-1). A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations N -> p pi(-), either the P-c(43800)(+) and P-c(4450)(+) -> J/psi p states, previously observed in Lambda(0)(b) -> J/psi pK(-) decays, or the Z(c)(4200)(-) -> J/psi pi(-) state, previously reported in B-0 -> J/psi K+pi(-) decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the P-c(4380)(+) and P-c(4 450)(+) production rates expected from their previous observation taking account of Cabibbo suppression.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the CP Asymmetry in B-s(0) – (B)over-bar(s)(0) Mixing. Phys. Rev. Lett., 117(6), 061803–9pp.
Abstract: The CP asymmetry in the mixing of B-s(0) and (B) over bar (0)(s) mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb(-1), recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV. Semileptonic B-s(0) and (B) over bar (s) (0) decays are studied in the inclusive mode D-s(-/+)mu(+/-)nu((-)) X-mu with the D-s(-/+) mesons reconstructed in the K+K-pi(-/+) final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be a(sl)(s) = (0.39 +/- 0.26 +/- 0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of a(sl)(s) to date. It is consistent with the prediction from the standard model and will constrain new models of particle physics.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Amplitude analysis of B- -> D+pi(-)pi(-) decays. Phys. Rev. D, 94(7), 072001–23pp.
Abstract: The Dalitz plot analysis technique is used to study the resonant substructures of B- -> D+pi(-)pi(-) decays in a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D+pi(-) mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D+pi(-) S wave together with virtual contributions from the D*(2007)(0) and B*(0) states, and components corresponding to the D-2*(2460)(0), D-1*(2680)(0), D-3*(2760)(0) and D-2*(3000)(0) resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B- -> D+pi(-)pi(-) decays. The D+pi(-) S wave has phase motion consistent with that expected due to the presence of the D-0*(2400)(0) state. These results constitute the first observations of the D-3*(2760)(0) and D-2*(3000)(0) resonances, with significances of 10 sigma and 6.6 sigma, respectively.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Search for Structure in the B-s(0)pi(+/-) Invariant Mass Spectrum. Phys. Rev. Lett., 117(15), 152003–9pp.
Abstract: The B-s(0)pi(+/-) invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb(-1) of pp collision data at root s 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B-s(0)pi(+/-) final state. The same limits also apply to a possible exotic meson decaying through the chain B-s(*0)pi(+/-), B-s(*0) -> B-s(0) gamma where the photon is excluded from the reconstructed decays.
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