LHCb Collaboration, Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Observation of a New Xi(-)(b) Resonance. Phys. Rev. Lett., 121(7), 072002–12pp.
Abstract: From samples of pp collision data collected by the LHCb experiment at root s = 7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb(-1), respectively, a peak in both the Lambda(0)(b) K- and Xi(0)(b)pi(-) invariant mass spectra is observed. In the quark model, radially and orbitally excited Xi(-)(b) resonances with quark content bds are expected. Referring to this peak as Xi(b)(6227)(-), the mass and natural width are measured to be m(Xi b(6227))(-) = 6226.9 +/- 2.0 +/- 0.3 +/- 0.2 MeV/c(2) and Gamma(Xi b(6227))- = 18.1 +/- 5.4 +/- 1.8 MeV/c(2), where the first uncertainty is statistical, the second is systematic, and the third, on m(Xi b(6227))(-), is due to the knowledge of the Lambda(0)(b) baryon mass. Relative production rates of the Xi(b)(6227)(-) -> Lambda K-0(b)- and Xi(b)(6227)(-) -> Xi(0)(b)pi(-) decays are also reported.
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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. (2017). Observation of the Decay Xi(-)(b) -> pK(-)K(-). Phys. Rev. Lett., 118(7), 071801–11pp.
Abstract: Decays of the Xi(-)(b) and Omega(-)(b) baryons to the charmless final states ph(-)h'(-), where h((')) denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The decay Xi(-)(b) -> pK(-)K(-) is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Xi(-)(b) -> pK(-)pi(-) decay. Results are reported, relative to the B- -> K+K-K- normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Xi(-)(b) -> pK(-)pi(-) and Xi(-)(b) -> p pi(-)pi(-) relative to Xi(-)(b) -> pK(-)K(-) decays are also measured.
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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). Observation of B-s(0) -> (D)over-bar*(0)phi and search for B-0 -> (D)over-bar(0)phi decays. Phys. Rev. D, 98(7), 071103–10pp.
Abstract: The first observation of the B-s(0) -> (D) over bar*(0)phi decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb -1 , collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B-0 -> (D) over bar (0)pi(+)pi(-) and is found to be B(B-s(0) -> (D) over bar*(0)phi) = (3.7 +/- 05 +/- 0.3 +/- 0.2) x 10(-5), where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B-0 -> (D) over bar (0)pi(+)pi(-) decay. The fraction of longitudinal polarization in this decay is measured to be f(L) = (73 +/- 15 +/- 4)%. The most precise determination of the branching fraction for the B-s(0) -> (D) over bar (0)phi decay is also obtained, B(B-s(0) -> (D) over bar (0)phi) = (3.0 +/- 0.3 +/- 0.2 +/- 0.2) x 10(-5). An upper limit, B(B-s(0) -> (D) over bar (0)phi) < 2.0 (2.3) x 10(-6) at 90% (95%) confidence level is set. A constraint on the omega – phi mixing angle delta is set at vertical bar delta vertical bar < 5.2 degrees (5.5 degrees) at 90% (95%) confidence level.
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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 long-lived scalar particles in B+-> K+chi(mu(+) mu(-)) decays. Phys. Rev. D, 95(7), 071101–9pp.
Abstract: A search for a long-lived scalar particle. is performed, looking for the decay B+ -> K+chi with chi ->mu(+)mu(-) pp collision data corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment at center-of-mass energies of root s = 7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250 < m(chi) < 4700 MeV/c(2) and lifetime 0.1 < tau(chi) < 1000 ps. Upper limits on the branching fraction B(B-broken vertical bar -> K-broken vertical bar chi(mu(vertical bar) mu(-))) at 95% confidence level are set as a function of m(chi) and tau(chi), varying between 2 x 10(-10) and 10(-7). These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
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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. (2020). First branching fraction measurement of the suppressed decay Xi(0)(c) -> pi(-) Lambda(+)(c). Phys. Rev. D, 102(7), 071101–11pp.
Abstract: The Xi(0)(c) baryon is unstable and usually decays into charmless final states by the c -> sud transition. It can, however, also disintegrate into a pi(-) meson and a Lambda(+)(c) baryon via s quark decay or via cs -> dc weak scattering. The interplay between the latter two processes governs the size of the branching fraction B(Xi(0)(c) -> pi(-) Lambda(+)(c)), first measured here to be (0.55 +/- 0.02 +/- 0.18)%, where the first uncertainty is statistical and second systematic. This result is compatible with the larger of the theoretical predictions that connect models of hyperon decays using partially conserved axial currents and SU(3) symmetry with those involving the heavy-quark expansion and heavy-quark symmetry. In addition, the branching fraction of the normalization channel, B(Xi(+)(c) -> pK(-) pi(+)) = (1.135 +/- 0.002 +/- 0.387)% is measured.
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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. (2017). Observation of the Decays Alpha(0)(b) -> chi(c1)pK(-) and Alpha(0)(b) ->chi(c2)pK(-). Phys. Rev. Lett., 119(6), 062001–11pp.
Abstract: The first observation of the decays Lambda(b)(0) -> chi(c1)pK(-) and Lambda(0)(b) -> chi(c2)pK(-) is reported using a data sample corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV The following ratios of branching fractions are measured: B(Lambda(0)(b) -> chi(c1)pK(-))/B(Lambda(0)(b) -> J/psi pK(-)) = 0.242 +/- 0.014 +/- 0.013 +/- 0.009, B(Lambda(0)(b) -> chi(c2)pK(-))/B(Lambda(0)(b) -> J/psi pK(-)) = 0.248 +/- 0.020 +/- 0.014 +/- 0.009, B(Lambda(0)(b) -> chi(c2)pK(-))/B(Lambda(0)(b) -> chi(c1)pK(-)) = 1.02 +/- 0.010 +/- 0.02 +/- 0.05, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the x(c1) -> J/psi gamma and chi(c2) -> J/psi gamma decays. Using both decay modes, the mass of the Ab baryon is also measured to be m(Lambda b0) = 5619.44 +/- 0.28 +/- 0.26 MeV/c(2), where the first and second uncertainties are statistical and systematic, respectively.
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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). Search for Dark Photons Produced in 13 TeV pp Collisions. Phys. Rev. Lett., 120(6), 061801–11pp.
Abstract: Searches are performed for both promptlike and long-lived dark photons, A', produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A' -> mu(+)mu(-) decays and a data sample corresponding to an integrated luminosity of 1.6 fb(-1) collected with the LHCb detector. The promptlike A' search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A' search is restricted to the low-mass region 214 < mo(A') < 350 MeV. No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the gamma-A' kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6 < m(A') < 70 GeV, and are comparable to the best existing limits for m(A') < 0.5 GeV. The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.
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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 B+, B-0 and Lambda(0)(b) production in pPb collisions at, root(NN)-N-s=8.16 TeV. Phys. Rev. D, 99(5), 052011–21pp.
Abstract: The production of B+, B-0 and Lambda(0)(b), hadrons is studied in proton-lead collisions at a center-of-mass energy per nucleon pair of root(NN)-N-s T = 8.16 TeV recorded with the LHCb detector at the LHC. The measurement uses a dataset corresponding to an integrated luminosity of 12.2 +/- 0.3 nb(-1) for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and 18.6 +/- 0.5 nb(-1) for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Double-differential cross sections are measured and used to determine forward-backward ratios and nuclear modification factors, which directly probe nuclear effects in the production of beauty hadrons. The double-differential cross sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon center-of-mass frame. Forward-to-backward cross section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of Lambda(0)(b), over B-0 production cross sections is reported and is consistent with the corresponding measurement in pp collisions.
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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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