Measurement of the relative rate of prompt χc0, χc1 and χc2 production at √s=7TeV

Prompt production of charmonium χc0, χc1 and χc2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of √s=7TeV. The χc mesons are identified through their decay to J/ψγ, with J/ψ→μ+mu− using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0fb−1 collected by the LHCb detector, is used to measure the relative prompt production rate of χc1 and χc2 in the rapidity range 2.0<y<4.5 as a function of the J/ψ transverse momentum from 3 to 20 GeV/c. First evidence for χc0 meson production at a hadron collider is also presented

Improving efficiency of analysis jobs in CMS

Hundreds of physicists analyze data collected by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider using the CMS Remote Analysis Builder and the CMS global pool to exploit the resources of the Worldwide LHC Computing Grid. Efficient use of such an extensive and expensive resource is crucial. At the same time, the CMS collaboration is committed to minimizing time to insight for every scientist, by pushing for fewer possible access restrictions to the full data sample and supports the free choice of applications to run on the computing resources. Supporting such variety of workflows while preserving efficient resource usage poses special challenges. In this paper we report on three complementary approaches adopted in CMS to improve the scheduling efficiency of user analysis jobs: automatic job splitting, automated run time estimates and automated site selection for jobs

Measurement of the differential branching fraction of the decay Λb0→Λμ+μ-

The differential branching fraction of the decay Λ0 b → Λμ+μ− is measured as a function of the square of the dimuon invariant mass, q2. A yield of 78 ± 12 Λ0 b → Λμ+μ− decays is observed using data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. A significant signal is found in the q2 region above the square of the J /ψ mass, while at lower-q2 values upper limits are set on the differential branching fraction. Integrating the differential branching fraction over q2, while excluding the J /ψ and ψ(2S) regions, gives a branching fraction of B(Λ0 b → Λμ+μ−) = (0.96 ± 0.16(stat) ± 0.13(syst) ± 0.21(norm)) × 10−6, where the uncertainties are statistical, systematic and due to the normalisation mode, Λ0 b → J /ψΛ, respectively

First measurement of time-dependent CP violation in B0s→K+K− decays

Direct and mixing-induced CP-violating asymmetries in B0s→K+K− decays are measured for the first time using a data sample of pp 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 → π + π − decays to be C ππ  = −0.38 ± 0.15 ± 0.02 and S ππ  = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements

Study of B0(s)→K0Sh+h′− decays with first observation of B0s→K0SK±π∓ and B0s→K0Sπ+π

A search for charmless three-body decays of B 0 and B0s mesons with a K0S 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 B0(s)→K0Sh+h′− decay modes (h (′) = π, K), relative to the well measured B0→K0Sπ+π− decay, are obtained. First observation of the decay modes B0s→K0SK±π∓ and B0s→K0Sπ+π− and confirmation of the decay B0→K0SK±π∓ are reported. The following relative branching fraction measurements or limits are obtained $ B(B0→K0SK±π∓)B(B0→K0Sπ+π−)=0.128±0.017(stat.)±0.009(syst.),B(B0→K0SK+K−)B(B0→K0Sπ+π−)=0.385±0.031(stat.)±0.023(syst.),B(B0s→K0Sπ+π−)B(B0→K0Sπ+π−)=0.29±0.06(stat.)±0.03(syst.)±0.02(fs/fd),B(B0s→K0SK±π∓)B(B0→K0Sπ+π−)=1.48±0.12(stat.)±0.08(syst.)±0.12(fs/fd)B(B0s→K0SK+K−)B(B0→K0Sπ+π−)∈[0.004;0.068]at90%CL

Search for the Lepton-Flavor-Violating Decays Bs0→e±μ∓ and B0→e±μ∓

A search for the lepton-flavor-violating decays B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0     fb − 1 of p p collisions at √ s = 7     TeV , collected by the LHCb experiment. The observed number of B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B ( B 0 s → e ± μ ∓ ) 101     TeV / c 2 and M LQ ( B 0 → e ± μ ∓ ) > 126     TeV / c 2 at 95% C.L., and are a factor of 2 higher than the previous bounds

First observation of B¯0 → J/ψK+K- and search for B¯0 → J/ψϕ decays

The first observation of the ¯¯¯ B 0 → J / ψ K + K − decay is presented with a data sample corresponding to an integrated luminosity of 1.0     fb − 1 of p p collisions at a center-of-mass energy of 7 TeV collected with the LHCb detector. The branching fraction is measured to be B ( ¯¯¯ B 0 → J / ψ K + K − ) = ( 2.53 ± 0.31 ± 0.19 ) × 10 − 6 , where the first uncertainty is statistical and the second is systematic. An amplitude analysis of the final state in the ¯¯¯ B 0 → J / ψ K + K − decay is performed to separate resonant and nonresonant contributions in the K + K − spectrum. Evidence of the a 0 ( 980 ) resonance is reported with statistical significance of 3.9 standard deviations. The corresponding product branching fraction is measured to be B ( ¯¯¯ B 0 → J / ψ a 0 ( 980 ) , a 0 ( 980 ) → K + K − ) = ( 4.70 ± 3.31 ± 0.72 ) × 10 − 7 , yielding an upper limit of B ( ¯¯¯ B 0 → J / ψ a 0 ( 980 ) , a 0 ( 980 ) → K + K − ) < 9.0 × 10 − 7 at 90% confidence level. No evidence of the resonant decay ¯¯¯ B 0 → J / ψ ϕ is found, and an upper limit on its branching fraction is set to be B ( ¯¯¯ B 0 → J / ψ ϕ ) < 1.9 × 10 − 7 at 90% confidence level

Measurement of Form-Factor-Independent Observables in the Decay B0→K*0μ+μ−

We present a measurement of form-factor-independent angular observables in the decay B 0 → K ∗ ( 892 ) 0 μ + μ − . The analysis is based on a data sample corresponding to an integrated luminosity of 1.0     fb − 1 , collected by the LHCb experiment in p p collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q 2 in the range 0.1 < q 2 < 19.0     GeV 2 / c 4 . Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q 2 bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%

Observation of the Decay B+c→B0sπ+

The result of a search for the decay B + c → B 0 s π + is presented, using the B 0 s → D − s π + and B 0 s → J / ψ ϕ channels. The analysis is based on a data sample of p p collisions collected with the LHCb detector, corresponding to an integrated luminosity of 1     fb − 1 taken at a center-of-mass energy of 7 TeV, and 2     fb − 1 taken at 8 TeV. The decay B + c → B 0 s π + is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is [ σ ( B + c ) / σ ( B 0 s ) ] × B ( B + c → B 0 s π + ) = [ 2.37 ± 0.31   ( stat ) ± 0.11   ( syst ) + 0.17 − 0.13 ( τ B + c ) ] × 10 − 3 , in the pseudorapidity range 2 < η ( B ) < 5 , where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the B + c lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction