BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2017). Measurement of the D* (2010)(+) -D+ Mass Difference. Phys. Rev. Lett., 119(20), 202003–7pp.
Abstract: We measure the mass difference, Delta m(+), between the D* (2010)(+) and the D+ using the decay chain D* (2010)(+) -> D+ pi(0) with D+ -> K- pi(+)pi(+). The data were recorded with the BABAR detector at center-of-mass energies at and near the (sic)(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb(-1). We measure Delta m(+) = (140601.0 +/- 6.8[stat] +/- 12.9[syst]) keV. We combine this result with a previous BABAR measurement of Delta m(0) = m(D* (2010)(+)) – m(D-0) to obtain Delta m(D) = m(D+) – m(D-0) = (4824.9 +/- 6.8[stat] +/- 12.9[syst]) keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages.
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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). chi(c1) and chi(c2) Resonance Parameters with the Decays chi(c1,c2) -> J/psi mu(+)mu(-). Phys. Rev. Lett., 119(22), 221801–9pp.
Abstract: The decays chi(c1) -> J/psi mu(+)mu(-) and chi(c1) -> J/psi mu(+)mu(-) are observed and used to study the resonance parameters of the chi(c1) and chi(c2) mesons. The masses of these states are measured to be m(chi(c1)) = 3510.71 +/- 0.04(stat) +/- 0.09(syst) MeV and m(chi(c2)) = 3556.10 +/- 0.06(stat) +/- 0.11(syst) MeV, where the knowledge of the momentum scale for charged particles dominates the systematic uncertainty. The momentum-scale uncertainties largely cancel in the mass difference m(chi(c2)) – m(chi(c1)) = 45.39 +/- 0.07(stat) +/- 0.03(syst) MeV. The natural width of the chi(c2) meson is measured to be Gamma(chi(c2)) = 2.10 +/- 0.20(stat) +/- 0.02(syst) MeV. These results are in good agreement with and have comparable precision to the current world averages.
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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). First Observation of the Rare Purely Baryonic Decay B0 -> p p-bar. Phys. Rev. Lett., 119(23), 232001–10pp.
Abstract: The first observation of the decay of a B0 meson to a purely baryonic final state, B-0 -> p$(p)over-bar-$ , is reported. The proton-proton collision data sample used was collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb(-1). The branching fraction is determined to be B(B-0 -> p$(p)over-bar-$) = (1.25 +/- 0.27 +/- 0.18) x 10(-8), where the first uncertainty is statistical and the second systematic. The decay mode B-0 -> p$(p)over-bar-$ is the rarest decay of the B-0 meson observed to date. The decay B-s(0 )-> p$(p)over-bar-$ is also investigated. No signal is seen and the upper limit B(B-s(0) -> p$(p)over-bar-$) < 1.5 x 10(-8) at 90% confidence level is set on the branching fraction.
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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 D-0 meson decays to pi(+) pi(-) mu(+) mu(-) and K+ K- mu(+) mu(-) final states. Phys. Rev. Lett., 119(18), 181805–10pp.
Abstract: The first observation of the D-0 -> pi(+) pi(-) mu(+) mu(-) and D-0 -> K+ K- mu(+) mu(-) decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 fb(-1) of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D-0 -> K- pi(+) [mu(+) mu(-)](rho 0/omega), where the two muons are consistent with coming from the decay of a rho(0) or omega meson. The results are B(D-0 -> pi(+) pi(-) mu(+) mu(-)) = (9.64 +/- 0.48 +/- 0.51 +/- 0.97) x 10(-7) and B(D-0 -> K+ K- mu(+) mu(-)) = (1.54 +/- 0.27 +/- 0.09 +/- 0.16) x 10(-7), where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
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MoEDAL Collaboration(Acharya, B. et al), Bernabeu, J., Garcia, C., Mamuzic, J., Mitsou, V. A., Ruiz de Austri, R., et al. (2017). Search for Magnetic Monopoles with the MoEDAL Forward Trapping Detector in 13 TeV Proton-Proton Collisions at the LHC. Phys. Rev. Lett., 118(6), 061801–6pp.
Abstract: MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV proton-proton collisions using the trapping technique, extending a previous publication with 8 TeV data during LHC Run 1. A total of 222 kg of MoEDAL trapping detector samples was exposed in the forward region and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges exceeding half the Dirac charge are excluded in all samples and limits are placed for the first time on the production of magnetic monopoles in 13 TeV pp collisions. The search probes mass ranges previously inaccessible to collider experiments for up to five times the Dirac charge.
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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 Five New Narrow Omega(0)(c) States Decaying to Xi K-+(c)-. Phys. Rev. Lett., 118(18), 182001–10pp.
Abstract: The Xi K-+(c)- mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3 fb(-1), collected by the LHCb experiment. The Xi(+)(c) is reconstructed in the decay mode pK(-)pi(vertical bar) . Five new, narrow excited Omega(0)(c) states are observed: the Omega(c)(3000)(0), Omega(c)(3050)(0), Omega(c)(3066)(0), Omega(c) (3090)(0), and Omega(c)(3119)(0). Measurements of their masses and widths are reported.
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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). Measurement of the B-s(0)-> mu(+) mu(-) Branching Fraction and Effective Lifetime and Search for B-0 ->mu(+) mu(-) Decays. Phys. Rev. Lett., 118(19), 191801–11pp.
Abstract: A search for the rare decays B-s(0)->mu(+)mu(-) and B-0 -> mu(+)mu(-) is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb(-1). An excess of B-s(0) -> mu(+)mu- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B-s(0) -> mu(+)mu(-)) = (3.0 +/- 0.6(-0.2)(+)(0.3)) x 10(-9), where the first uncertainty is statistical and the second systematic. The first measurement of the B-s(0) -> mu(+)mu(-) effective lifetime, tau(B-s(0)-> mu(+) mu(-)) = 2.04 +/- 0.44 +/- 0.05 ps, is reported. No significant excess of B-0 -> mu(+)mu(-) decays is found, and a 95% confidence level upper limit, B(B-0 -> mu(+)mu(-) ) < 3.4 x 10(-10), is determined. All results are in agreement with the standard model expectations.
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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). Study of J/psi production in jets. Phys. Rev. Lett., 118(19), 192001–11pp.
Abstract: The production of J/psi mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/psi meson, z(J/psi) p(T) (J/psi) / p(T)(jet) is measured using jets with p(T)(jet) > 20 GeV in the pseudorapidity range 2.5 < eta(jet) < 4.0. The observed z(J/psi) distribution for J/psi mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/psi production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the p(T) fraction carried by prompt J/psi mesons in jets at any experiment.
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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). Search for the Decays B-S(0) -> tau(+) tau(-) and B-0 -> tau(+) tau(-). Phys. Rev. Lett., 118(25), 251802–10pp.
Abstract: A search for the rare decays B-S(0) -> tau(+) tau(-) and B-0 -> tau(+) tau(-) is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb(-1) collected in 2011 and 2012. The tau leptons are reconstructed through the decay tau(-) -> pi(-) pi(+)pi(-) nu(tau). Assuming no contribution from B-S(0) -> tau(+) tau(-) decays, an upper limit is set on the branching fraction B(B-S(0) -> tau(+) tau(-)) < 6.8 x 10(-3) at the 95% confidence level. If instead no contribution from B-S(0) -> tau(+) tau(-) decays is assumed, the limit is B(B-s(0) -> tau(+) tau(-)) < 2.1 x 10(-3) at the 95% confidence level. These results correspond to the first direct limit on B(B-S(0) -> tau(+) tau(-)) and the world's best limit on B(B-S(0) -> tau(+) tau(-))
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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). Measurement of the CP Violation Parameter A(r) in D-0 -> K+K- and D-0 -> pi(+)pi(-) Decays. Phys. Rev. Lett., 118(26), 261803–9pp.
Abstract: Asymmetries in the time-dependent rates of D-0 -> K+K- and D-0 -> pi(+)pi(-)decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3 fb(-1). The asymmetries in effective decay widths between D-0 and (D) over bar (0) decays, sensitive to indirect CP violation, are measured to be A(r)(K+K-) = (-0.30 +/- 0.32 0.10) x 10(-3) and A(r) pi(+)pi(-)) = (0.46 +/- 0.58 +/- 0.12) x 10(-3), where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.
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