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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), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of the decay B-c(+) -> psi(2S)pi(+). Phys. Rev. D, 87(7), 071103–7pp.
Abstract: The decay B-c(+) -> psi(2S)pi(+) with psi(2S) -> mu(+)mu(-) is observed with a significance of 5.2 sigma using pp collision data corresponding to an integrated luminosity of 1.0 fb(-1) collected by the LHCb experiment. The branching fraction of B-c(+) -> psi(2S)pi(+) decays relative to that of the B-c(+) -> J/psi pi(+) mode is measured to be B(B-c(+) -> psi(2S)pi(+))/B(B-c(+) -> J/psi pi(+)) = 0.250 +/- 0.068(stat) +/- 0.014(syst) +/- 0.006(B). The last term is the uncertainty on the ratio B(psi(2S) -> mu(+)mu(-))/B(J/psi -> mu(+)mu(-)).
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for the decay B-s(0) -> D*(-/+)pi(+/-). Phys. Rev. D, 87(7), 071101–8pp.
Abstract: A search for the decay B-s(0) -> D*(-/+)pi(+/-) is presented using a data sample corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help us to understand the mechanism behind related decays such as B-s(0) -> pi(+)pi(-) and B-s(0) -> D (D) over bar. Systematic uncertainties are minimized by using B-0 -> D*(-/+)pi(+/-) as a normalization channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(B-s(0) -> D*(-/+)pi(+/-) < 6.1(7.8) x 10(-6) at 90% (95%) confidence level.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). First observations of (B)over-bar(s)(0) -> D+D-, Ds+D- and D-0(D)over-bar(0) decays. Phys. Rev. D, 87(9), 092007–12pp.
Abstract: First observations and measurements of the branching fractions of the (B) over bar (0)(s) -> D+D-, (B) over bar (0)(s) -> Ds+D- and (B) over bar (0)(s) -> D-0(D) over bar (0) decays are presented using 1.0 fb(-1) of data collected by the LHCb experiment. These branching fractions are normalized to those of (B) over bar (0) -> D+D-, B-0 -> D-Ds+ and B- -> (DDs-)-D-0, respectively. An excess of events consistent with the decay (B) over bar (0) -> D-0(D) over bar (0) is also seen, and its branching fraction is measured relative to that of B- -> D0Ds-. Improved measurements of the branching fractions B((B) over bar (0)(s) -> Ds+Ds-) and B(B- -> (DDs-)-D-0) are reported, each relative to B(B-0 -> D-Ds+). The ratios of branching fractions are B((B) over bar (0)(s) -> D+D-)/B((B) over bar (0) -> D+D-) = 1.08 +/- 0.20 +/- 0.10, B((B) over bar (0)(s) -> Ds+D-)/B(B-0 -> D-Ds+) = 0.050 +/- 0.008 +/- 0.004, B((B) over bar (0)(s) -> D-0(D) over bar (0))/B((B) over bar (-) -> (DDs-)-D-0) = 0.019 +/- 0.003 +/- 0.003, B((B) over bar (0) -> D-0(D) over bar (0))/B(B- -> (DDs-)-D-0) < 0.0024 at 90% CL, B(<(B)over bar>(0)(s) -> D-s(+)(D) over bar (-)(s))/B(B-0 -> D-Ds+) = 0.56 +/- 0.03 +/- 0.04, B(B -> (DDs)-D-0)/B(B-0 -> D-Ds+) = 1.22 +/- 0.02 +/- 0.07, where the uncertainties are statistical and systematic, respectively.
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