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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). Study of B-c(+) decays to charmonia and three light hadrons. J. High Energy Phys., 01(1), 065–28pp.
Abstract: Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb(-1) collected with the LHCb detector, seven decay modes of the B-C(+) meson into a J/psi or psi(2S) meson and three charged hadrons, kaons or pions, are studied. The decays B-C (+)-> (psi(2S) -> J/psi pi(+)pi(-))pi(+), B+C -> (psi(2S)pi(+)pi(-)pi(+), B+C -> J/psi K+pi(-)pi(+) and B+C -> J/K+K-K+ are observed for the first time, and evidence for the B-C (+)-> (psi(2S)K+K-pi(+), decay is found, where J/psi and psi(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different B-C(+) decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
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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). Centrality determination in heavy-ion collisions with the LHCb detector. J. Instrum., 17(5), P05009–31pp.
Abstract: The centrality of heavy-ion collisions is directly related to the created medium in these interactions. A procedure to determine the centrality of collisions with the LHCb detector is implemented for lead-lead collisions root s(NN) = 5 TeV and lead-neon fixed-target collisions at root s(NN) = 69 GeV. The energy deposits in the electromagnetic calorimeter are used to determine and define the centrality classes. The correspondence between the number of participants and the centrality for the lead-lead collisions is in good agreement with the correspondence found in other experiments, and the centrality measurements for the lead-neon collisions presented here are performed for the first time in fixed-target collisions at the LHC.
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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). Tests of Lepton Universality Using B-0 -> K(S)(0)l(+) l(-) and B+ -> K*(+)l(+)l(-) Decays. Phys. Rev. Lett., 128(19), 191802–15pp.
Abstract: Tests of lepton universality in B-0 -> K(S)(0)l(+)l(-) and B+ -> K*(+)l(+)l(-) decays where l is either an electron or a muon are presented. The differential branching fractions of B-0 -> K(S)(0)e(+)e(-) and B+ -> K*(+)e(+)e(-) decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B-0 -> K(S)(0)e(+)e(-) and B+ -> K*(+)e(+)e(-) decays is reported.
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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). Search for massive long-lived particles decaying semileptonically at root s=13 TeV. Eur. Phys. J. C, 82(4), 373–19pp.
Abstract: A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200 GeV/c(2) is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 GeV/c(2) up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 GeV/c(2). The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at root s = 13 TeV, corresponding to an integrated luminosity of 5.4 fb(-1). No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
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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). Observation of two new excited Ξ0b states decaying to Λ0bK−π+. Phys. Rev. Lett., 128(16), 162001–12pp.
Abstract: Two narrow resonant states are observed in the Λ0bK−π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb−1. The minimal quark content of the Λ0bK−π+ system indicates that these are excited Ξ0b baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m(Ξb(6327)0)=6327.28+0.23−0.21±0.12±0.24 MeV and m(Ξb(6333)0)=6332.69+0.17−0.18±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41+0.26−0.27±0.12 MeV, where the uncertainties are statistical, systematic and due to the Λ0b mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ(Ξb(6327)0)<2.20 (2.56) MeV and Γ(Ξb(6333)0)<1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ0b resonances.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Simultaneous determination of CKM angle gamma and charm mixing parameters. J. High Energy Phys., 12(12), 141–32pp.
Abstract: A combination of measurements sensitive to the CP violation angle gamma of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D-0 and (D) over bar (0) mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN's Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be x = (0.400(-0.053)(+0.052))% and y = (0.630(-0.030)(+0.033))%. The angle gamma is found to be gamma = (65.4(-4.2)(+3.8))degrees and is the most precise determination from a single experiment.
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Biryukov, V. M., & Ruiz Vidal, J. (2022). Improved experimental layout for dipole moment measurements at the LHC. Eur. Phys. J. C, 82(2), 149–11pp.
Abstract: The electric and magnetic dipole moment of charm and bottom baryons can be measured for the first time by using bent crystal technology at the LHC. The experimental method, proposed in recent years, suffers from limited statistics, which dominates the uncertainty of the measurement. In this work, we present an alternative experimental layout, based on the use of crystal lenses, that improves the trapping efficiency by about a factor 15 (35) for a 2-cm (5-mm) target with respect to the nominal layout, with plain crystal faces. The efficiencies are evaluated taking into account the constraints from the LHC machine, and the technical challenges to realize this novel experimental method are discussed.
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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). Study of Z Bosons Produced in Association with Charm in the Forward Region. Phys. Rev. Lett., 128(8), 082001–12pp.
Abstract: Events containing a Z boson and a charm jet are studied for the first time in the forward region of proton-proton collisions. The data sample used corresponds to an integrated luminosity of 6 fb(-1) collected at a center-of-mass energy of 13 TeV with the LHCb detector. In events with a Z boson and a jet, the fraction of charm jets is determined in intervals of Z-boson rapidity in the range 2.0 < y(Z) < 4.5. A sizable enhancement is observed in the forwardmost y(Z) interval, which could be indicative of a valencelike intrinsic-charm component in the proton wave function.
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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 chi(c1) (3872) production in proton-proton collisions at root s=8 and 13 TeV. J. High Energy Phys., 01(1), 131–27pp.
Abstract: The production cross-section of the chi(c1)(3872) state relative to the psi(2S) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of root s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb(-1), respectively. The two mesons are reconstructed in the J/psi pi(+) pi(-) final state. The ratios of the prompt and nonprompt chi(c1)(3872) to psi(2S) production cross-sections are measured as a function of transverse momentum, p(T), and rapidity, y, of the chi(c1)(3872) and psi(2S) states, in the kinematic range 4 < p(T) < 20 GeV/c and 2.0 < y < 4.5. The prompt ratio is found to increase with pT , independently of y. For the prompt component, the double ratio of the chi(c1)(3872) and psi(2S) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of p(T) and centre-of-mass energy.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Search for the doubly charmed baryon Xi(+)(cc) in the Xi(+)(c)pi(-)pi(+) final state. J. High Energy Phys., 12(12), 107–27pp.
Abstract: A search for the doubly charmed baryon Xi(+)(cc) is performed in the Xi(+)(c)pi(-)pi(+ )invariant-mass spectrum, where the Xi(-)(cc) baryon is reconstructed in the pK(-)pi(+) final state. The study uses proton-proton collision data collected with the LHCb detector at a centreof-mass energy of 13 TeV, corresponding to a total integrated luminosity of 5.4 fb(-1). No significant signal is observed in the invariant-mass range of 3.4-3.8 GeV/c(2). Upper limits are set on the ratio of branching fractions multiplied by the production cross-section with respect to the Xi(++)(cc) -> (Xi(+)(c) -> pK(-)pi(+)+/-)pi(+ ) decay for different Xi(+)(cc) mass and lifetime hy- potheses in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 2.5 to 25 GeV/c. The results from this search are combined with a previously published search for the Xi(+)(cc) -> A(c)(+)K(-)pi(+ ) decay mode, yielding a maximum local significance of 4.0 standard deviations around the mass of 3620 MeV/c(2), including systematic uncertainties. Taking into account the look-elsewhere effect in the 3.5-3.7 GeV/c(2) mass window, the combined global significance is 2.9 standard deviations including systematic uncertainties.
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