LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Measurement of the eta(c)(1S) production cross-section in p p collisions at root s=13TeV. Eur. Phys. J. C, 80(3), 191–18pp.
Abstract: Using a data sample corresponding to an integrated luminosity of 2.0 fb-1, collected by the LHCb experiment, the production of the.c(1S) state in proton-proton collisions at a centre-of-mass energy of v s = 13 TeVis studied in the rapidity range 2.0 < y < 4.5 and in the transverse momentum range 6.5 < pT < 14.0GeV. The cross-section for prompt production of.c(1S) mesons relative to that of the J/. meson is measured using the p p decay mode and is found to be s.c(1S)/sJ/. = 1.69 +/- 0.15 +/- 0.10 +/- 0.18. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the J/.. p p and.c. p p decays. The prompt.c(1S) production cross-section is determined to be s.c( 1S) = 1.26 +/- 0.11 +/- 0.08 +/- 0.14 μb, where the last uncertainty includes that on the J/. meson cross-section. The ratio of the branching fractions of b-hadron decays to the.c(1S) and J/. states is measured to be Bb..c X /Bb. J/. X = 0.48 +/- 0.03 +/- 0.03 +/- 0.05, where the last uncertainty is due to those on the branching fractions of the J/.. p p and.c. p p decays. The difference between the J/. and.c(1S) masses is also determined to be 113.0 +/- 0.7 +/- 0.1MeV, which is the most precise single measurement of this quantity to date.
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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), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Study of Bc+ meson decays to charmonia plus multihadron final states. J. High Energy Phys., 07(7), 198–26pp.
Abstract: Four decay modes of the B-c(+) meson into a J/psi meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13TeV and corresponding to an integrated luminosity of 9 fb(-1). The decay B-c(+) -> J/psi K+ K- pi(+)pi(+)pi(-) is observed for the first time, and evidence for the B-c(+) -> J/psi 4 pi(+)3 pi(-) decay is found. The decay B-c(+) -> J/psi 3 pi(+)2 pi(-) is observed and the previous observation of the B-c(+) -> psi(2S)pi(+)pi(+)pi(-) decay is confirmed using the psi(2S) -> J/psi pi(+)pi(-) decay mode. Ratios of the branching fractions of these four B-c(+) decay channels are measured.
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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 CP asymmetries and branching fraction ratios of B- decays to two charm mesons. J. High Energy Phys., 09(9), 202–30pp.
Abstract: The CP asymmetries of seven B- decays to two charm mesons are measured using data corresponding to an integrated luminosity of 9 fb(-1) of proton-proton collisions collected by the LHCb experiment. Decays involving a D*(0) or D-s(*-) meson are analysed by reconstructing only the D-0 or D-s(-) decay products. This paper presents the first measurement of A(CP) (B- -> D-s(*-) D-0) and A(CP) (B- -> D-s(-) D*(0)), and the most precise measurement of the other five CP asymmetries. There is no evidence of CP violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.
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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). Amplitude analysis of the D+s → π-π+π+ decay. J. High Energy Phys., 07(7), 204–35pp.
Abstract: A Dalitz plot analysis of the D-s(+) -> pi(-)pi(+)pi(+) decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 1.5 fb(-1). The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the pi(+)pi(-) S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the D-s(+) -> omega(782)pi(+) channel in the D-s(+) -> pi(-)pi(+)pi(+) decay. The resonant structures of the D-s(+) -> pi(-)pi(+)pi(+) and D+ -> pi(-)pi(+)pi(+) decays are compared, providing information about the mechanisms for the hadron formation in these decays.
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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. (2017). Search for massive long-lived particles decaying semileptonically in the LHCb detector. Eur. Phys. J. C, 77(4), 224–16pp.
Abstract: A search is presented formassive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8TeV, corresponding to integrated luminosities of 1 and 2fb(-1), respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80GeV/c(2) and lifetimes from 5 to 100 ps are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23-198 GeV/c(2) range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.
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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). Λc+ polarimetry using the dominant hadronic mode. J. High Energy Phys., 07(7), 228–26pp.
Abstract: The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the Lambda(+)(c) -> pK(-)pi(+) decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the Lambda(+)(c) baryon and eases inclusion of the Lambda(+)(c)-> pK(-)pi(+) decay mode in hadronic amplitude analyses.
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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. (2017). Search for the CP-violating strong decays eta -> pi(+)pi(-) and eta ' (958) -> pi(+)pi(-). Phys. Lett. B, 764, 233–240.
Abstract: A search for the CP-violating strong decays eta -> pi(+)pi(-) and eta ' (958) -> pi(+)pi(-) has been performed using approximately 2.5 x 10(7) events of each of the decays D+ -> pi(+)pi(+)pi(-) and D-s(+) -> pi(+)pi(+)pi(-), recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb(-1) of pp collision data recorded during LHC Run 1 and 0.3fb(-1) recorded in Run 2. No evidence is seen for D-(s)(+) -> pi(+)eta((')) with eta((')) -> pi(+)pi(-), and upper limits at 90% confidence level are set on the branching fractions, B(eta -> pi(+)pi(-)) < 1.6 x 10(-5) and B(eta' -> pi(+)pi(-)) < 1.8 x 10(-5). The limit for the eta decay is comparable with the existing one, while that for the eta' is a factor of three smaller than the previous limit.
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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. (2017). New algorithms for identifying the flavour of B-0 mesons using pions and protons. Eur. Phys. J. C, 77(4), 238–15pp.
Abstract: Two new algorithms for use in the analysis of pp collision are developed to identify the flavour of B mesons at production using pions and protons from the hadronization process. The algorithms are optimized and calibrated on data, using B-0 -> D- pi(+) decays from pp collision data collected by LIICh at centre -of -mass energies of 7 and 8 TeV. The tagging power of the new pion algorithm is 60% greater than the previously available one; the algorithm using protons to identify the flavour of a B-0 meson is the first of its kind.
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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). Search for heavy neutral leptons in W plus . μplus μ+/- jet decays. Eur. Phys. J. C, 81(3), 248–15pp.
Abstract: A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0 fb-1 of proton-proton collision data at centre-of-mass energies of 7 and 8 TeV collected with the LHCb experiment. Both same-sign and opposite-signmuons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at 95% confidence level in the heavy-neutrino mass range from 5 to 50GeV/c2. These are of the order of 10(-3) for lepton-number-conserving decays and of the order of 10(-4) for lepton-number-violating heavy-neutrino decays.
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