895 research outputs found
Strong Constraints on the Rare Decays B-s(0) -> mu(+)mu(-) and B-0 -> mu(+)mu(-)
No full textA search for B-s(0) -> mu(+)mu(-) and B-0 -> mu(+)mu(-) decays is performed using 1.0 fb(-1) of pp collision data collected at root s = 7 TeV with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be B(B-s(0) -> mu(+)mu(-)) mu(+)mu(-)) < 1.0(0.81) x 10(-9) at 95% (90%) confidence level
Study of B-(s)(0) -> K(s)(0)h(+)h '(-) decays with first observation of B-s(0) -> (KsK +/-)-K-0 pi(-/+) and B-s(0) -> K-s(0)pi(+)pi(-)
No full textA search for charmless three-body decays of B-0 and B-s(0) mesons with a K-S(0) meson in the final state is performed using the pp collision data, corresponding to an integrated luminosity of 1.0 fb(-1), collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B-(s)(0) -> K(S)(0)h(+)h'(-) decay modes (h(()'()) = pi, K), relative to the well measured B-0 -> K-S(0)pi(+)pi(-) decay, are obtained. First observation of the decay modes B-s(0) -> (KSK +/-)-K-0 pi(-/+) and B-s(0) -> K-S(0)pi(+)pi(-) and confirmation of the decay B-0 -> (KSK +/-)-K-0 pi(-/+) are reported. The following relative branching fraction measurements or limits are obtained B(B-0 -> (KSK +/-)-K-0 pi(-/+))/B(B-0 -> K-S(0)pi(+)pi(-)) = 0.128 +/- 0.017 (stat.) +/- 0.009 (syst.), B(B-0 -> (KSK+K-)-K-0)/B(B-0 -> K-S(0)pi(+)pi(-)) = 0.385 +/- 0.031 (stat.) +/- 0.023 (syst.), B(B-s(0) -> K-S(0)pi(+)pi(-))/B(B-0 -> K-S(0)pi(+)pi(-)) = 0.29 +/- 0.06 (stat.) +/- 0.03 (syst.) +/- 0.02 (f(s)/f(d)), B(B-s(0) -> (KSK +/-)-K-0 pi(-/+))/B(B-0 -> K-S(0)pi(+)pi(-)) = 1.48 +/- 0.12 (stat.) +/- 0.08 (syst.) +/- 0.12 (f(s)/f(d)), B(B-s(0) -> (KSK+K-)-K-0)/B(B-0 -> K-S(0)pi(+)pi(-)) is an element of [0.004; 0.068] at 90% CL
First observation of the decay B-s(0) -> phi(K)over-bar*(0)
No full textThe first observation of the decay B-s(0) -> phi(K) over bar*(0) is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1) of p p collisions at root s = 7 TeV, collected with the LHCb detector. A yield of 30 +/- 6 B-s(0) -> (K+ K-)(K- pi(+)) decays is found in the mass windows 1012.5 < M (K+ K-) < 1026.5MeV/c(2) and 746 < M (K- pi(+)) < 1046MeV/c(2). The signal yield is found to be dominated by B-s(0) -> phi(K) over bar*(0) decays, and the corresponding branching fraction is measured to be B (B-s(0) (->) phi(K) over bar*(0)) = (1.10 +/- 0.24 (stat) +/- 0.14 (syst) +/- 0.08 (f(d)/f(s))) x 10(-6), where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions f(d)/f(s) which accounts for the different production rate of B-0 and B-s(0) mesons. The significance of B-s(0) ->phi (K) over bar*(0) signal is 6.1 standard deviations. The fraction of longitudinal polarization in B-s(0) -> phi(K) over bar*(0) decays is found to be f(0) = 0.51 +/- 0.15 (stat) +/- 0.07 (syst)
Observation of D0-D0 oscillations
No full textWe report a measurement of the time-dependent ratio of D(0) K(+) pi- to D(0) K(-) pi(+) decay rates in D(*+)-tagged events using 1.0 fb(-1) of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x('2) = (-0.9 ± 1.3) * 10(-4), y' = (7.2 ± 2.4) * 10(-3), and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates R(D) = (3.52 ± 0.15) * 10^{-3}, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D0 oscillations from a single measurement
A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states
No full textA first study of CP violation in the decay modes B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-) and B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-), where h labels a K or pi meson and D labels a D-0 or (D) over bar (0) meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb(-1). The analysis is sensitive to the CP-violating CKM phase gamma through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of gamma using other decay modes. (C) 2014 The Authors. Published by Elsevier B.V
Search for the rare decay D-0 -> mu(+) mu(-)
No full textA search for the rare decay D-0 -> mu(+) mu(-) is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb(-1), of pp collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of B(D-0 -> mu(+) mu(-)) < 6.2 (7.6) x 10(-9) at 90% (95%) confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved
Searches for and decays to and final states with first observation of the decay
No full textA search for previously unobserved decays of beauty baryons to the final states K(s)(0)p pi(-) and K(s)(0)pK(-) is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions. The Lambda(0)(b) -> (K) over bar0 p pi(-) decay is observed with a significance of 8.6 sigma, with branching fraction B(Lambda(0)(b) -> (K) over bar0 p pi(-)) = (1.26 +/- 0.19 +/- 0.09 +/- 0.34 +/- 0.05) x 10(-5,) where the uncertainties are statistical, systematic, from the ratio fragmentation fractions f Lambda(0)(b)/fd, and from the branching fraction of the B-0 -> K-0 pi(+)pi(-) normalisation channel, respectively. A first measurement is made of the CP asymmetry, giving A(CP)(Lambda(0)(b) -> (K) over bar0 p pi(-)) = 0.22 +/- 0.13 (stat) +/- 0.03 (syst). No significant signals are seen for Lambda(0)(b) -> K(s)(0)pK(-) decays, Xi(0)(b) decays to both the K(s)(0)p pi(-) and K(s)(0)pK(-) final states, and the Lambda(0)(b) -> D-s(-)(-> (KsK-)-K-0)p decay, and upper limits on their branching fractions are reported
Measurement of D0-D0 mixing parameters and search for CP violation using D0 K+ pi- decays
No full textMeasurements of charm mixing parameters from the decay-time-dependent ratio of D0 K+ pi- to D0 K- pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3fb(-1) of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP ) symmetry, the mixing parameters are determined to be x'2=(5.5±4.9)*10(-5), y'=(4.8±1.0)*10(-3), and RD=(3.568±0.066)*10(-3). Allowing for CP violation, the measurement is performed separately for D0 and D0 mesons yielding AD=(-0.7±1.9)%, for the direct CP-violating asymmetry, and 0.75<|q/p|<1.24 at the 68.3% confidence level, for the parameter describing CP violation in mixing. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation
Search for the Lepton-Flavor-Violating Decays B-s(0) -> e(+/-)mu(-/+) and B-0 -> e(+/-)mu(-/+)
No full textA search for the lepton-flavor-violating decays B-s(0) -> e(+/-)mu(-/+) and B-0 -> e(+/-)mu(-/+) is performed with a data sample, corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions at root s = 7 TeV, collected by the LHCb experiment. The observed number of B-s(0) -> e(+/-)mu(-/+) and B-0 -> e(+/-)mu(-/+) candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B(B-s(0) -> e(+/-)mu(-/+)) < 1.1(1.4) x 10(-8) and B(B-0 -> e(+/-)mu(-/+)) < 2.8(3.7) x 10(-9) at 90% (95%) confidence level (C.L.). These limits are a factor of 20 lower than those set by previous experiments. Lower bounds on the Pati-Salam leptoquark masses are also calculated, M-LQ(B-s(0) -> e(+/-)mu(-/+)) > 101 TeV/c(2) and M-LQ(B-0 -> e(+/-)mu -/+) > 126 TeV/c(2) at 95% C.L., and are a factor of 2 higher than the previous bounds
First measurement of time-dependent CP violation in B-s(0) -> K+K- decays
No full textDirect and mixing-induced CP-violating asymmetries in B-s(0) -> K+K- decays are measured for the first time using a data sample of p p collisions, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C-KK = 0.14 +/- 0.11 +/- 0.03 and S-KK = 0.30 +/- 0.12 +/- 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B-0 -> pi(+)pi(-) decays to be C-pi pi = -0.38 +/- 0.15 +/- 0.02 and S-pi pi = -0.71 +/- 0.13 +/- 0.02, in good agreement with existing measurements
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