BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2019). Search for a Stable Six-Quark State at BABAR. Phys. Rev. Lett., 122(7), 072002–7pp.
Abstract: Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in (sic) > S (Lambda) over bar(Lambda) over bar decays based on a sample of 90 x 10(6)(sic)(2S) and 110 x 10(6)(sic)(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined (sic)(2S, 3S) -> S (Lambda) over bar(Lambda) over bar branching fraction in the range (1.2-1.4) x 10(-7) are derived for m(s) < 2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.
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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), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). First Measurement of Charm Production in its Fixed-Target Configuration at the LHC. Phys. Rev. Lett., 122(13), 132002–12pp.
Abstract: The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/psi and D-0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of root s(NN) = 86.6 and 110.4 GeV, respectively. The J/psi and D-0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be sigma(J/psi) = 652 +/- 33(stat) +/- 42(syst) nb/nucleon and sigma(D0) = 80.8 +/- 2.4(syst) +/- 6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.
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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). Search for CP violation through an amplitude analysis of D-0 K+K-+- decays. J. High Energy Phys., 02(2), 126–34pp.
Abstract: A search for CP violation in the Cabibbo-suppressed D-0 K+K-+- decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb(-1). The D-0 mesons are reconstructed from semileptonic b-hadron decays into D0-X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D-0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.
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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). Search for the rare decay B+ -> mu(+) mu(-) mu(+)nu(mu). Eur. Phys. J. C, 79(8), 675–12pp.
Abstract: A search for the rare leptonic decay B +. μ+ μ- μ+.mu is performed using proton- proton collision data corresponding to an integrated luminosity of 4.7 fb – 1 collected by the LHCb experiment. The search is carried out in the region where the lowest of the two μ+ μ- mass combinations is below 980 MeV/ c2. The data are consistent with the background- only hypothesis and an upper limit of 1.6x10 – 8 at 95% confidence level is set on the branching fraction in the stated kinematic region.
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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). Study of the B-0 (770)degrees K-*(892)(0) decay with an amplitude analysis of B-0 ((+-))(K+pi(-)) decays. J. High Energy Phys., 05(5), 026–31pp.
Abstract: An amplitude analysis of B-0 ((+-))(K+-) decays is performed in the two-body invariant mass regions 300 < m((+-)) < 1100 MeV/c(2), accounting for the (0), , f(0)(500), f(0)(980) and f(0)(1370) resonances, and 750 < m(K+-) < 1200 MeV/c(2), which is dominated by the K-*(892)(0) meson. The analysis uses 3 fb(-1) of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The CP averages and asymmetries are measured for the magnitudes and phase differences of the con- tributing amplitudes. The CP-averaged longitudinal polarisation fractions of the vector-vector modes are found to be fK*0 = 0.164 +/- 0.015 +/- 0.022 and fK*0 = 0.68 +/- 0.17 +/- 0.16, and their CP asymmetries, AK*0 = -0.62 +/- 0.09 +/- 0.09 and AK*0 = -0.13 +/- 0.27 +/- 0.13, where the first uncertainty is statistical and the second systematic.
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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. (2019). Measurement of the branching fraction and CP asymmetry in B plus . J/.. plus decays. Eur. Phys. J. C, 79(6), 537–13pp.
Abstract: The branching fraction and direct CP asymmetry of the decay B +. J/.. + are measured using protonproton collision data collected with the LHCb detector at centre- of- mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3 fb – 1. The following results are obtained: ( B +. J/.. +) = ( 3.81 + 0.25 – 0.24 +/- 0.35) x 10 – 5, ACP ( B +. J/.. +) = – 0.045 + 0.056 – 0.057 +/- 0.008, where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date.
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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). Model-Independent Observation of Exotic Contributions to B degrees -> J/psi K+pi(-) Decays. Phys. Rev. Lett., 122(15), 152002–10pp.
Abstract: An angular analysis of B degrees -> J/psi K+pi(-) decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected with the LHCb detector. The m(K+pi(-) ) spectrum is divided into fine bins. In each m(K+pi(-)) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+pi(-) system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J/psi pi(-)) vs m(K+pi(-)) plane suggests structures near m(J/psi pi(-)) = 4200 and 4600 MeV.
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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). Observation of the doubly Cabibbo-suppressed decay Xi(+)(c) -> p phi. J. High Energy Phys., 04(4), 084–18pp.
Abstract: The doubly Cabibbo- suppressed decay Xi(+)(c) -> p phi with ! K+K is observed for the fi rst time, with a statistical signi fi cance of more than fi fteen standard deviations. The data sample used in this analysis corresponds to an integrated luminosity of 2 fb recorded with the LHCb detector in pp collisions at a centre- of- mass energy of 8TeV. The ratio of branching fractions between the decay + c ! p and the singly Cabibbo- suppressed decay + c ! pK is measured to be B (Xi(+)(c) -> p phi) B (Xi(+)(c) -> p phi) = (19 : 8 0 : 7 0 : 9 0 : 2) 10 where the fi rst uncertainty is statistical, the second systematic and the third due to the knowledge of the Xi(+)(c) -> pK(+)pi(+) branching fraction.
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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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