920 research outputs found
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Search for the decay Bs0âD*âϱ
A search for the decay Bs0âD*âϱ is presented using a data sample corresponding to an integrated luminosity of 1.0ââfb-1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help us to understand the mechanism behind related decays such as Bs0âÏ+Ï- and Bs0âDD- . Systematic uncertainties are minimized by using B0âD*âϱ as a normalization channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(Bs0âD*âϱ)<6.1(7.8)Ă10-6 at 90% (95%) confidence level
Study of DJ meson decays to D+Ïâ, D0Ï+ and Dâ+Ïâ final states in pp collisions
A study of D+Ïâ, D0Ï+ and Dâ+Ïâ final states is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fbâ1, collected at a centre-of-mass energy of 7 TeV with the LHCb detector. The D1(2420)0 resonance is observed in the Dâ+Ïâ final state and the Dâ2(2460) resonance is observed in the D+Ïâ, D0Ï+ and Dâ+Ïâ final states. For both resonances, their properties and spin-parity assignments are obtained. In addition, two natural parity and two unnatural parity resonances are observed in the mass region between 2500 and 2800 MeV. Further structures in the region around 3000 MeV are observed in all the Dâ+Ïâ, D+Ïâ and D0Ï+ final states
Measurements of the branching fractions of B+âppK+ decays
The branching fractions of the decay B+ â ppÌK+ for different intermediate states are measured using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment. The total branching fraction, its charmless component MppÌ < 2.85 GeV/c2 and the branching fractions via the resonant ccÌ states η c(1S) and Ï(2S) relative to the decay via a J/Ï intermediate state are [Equation not available: see fulltext.] Upper limits on the B + branching fractions into the η c(2S) meson and into the charmonium-like states X(3872) and X(3915) are also obtained
Measurement of B meson production cross-sections in proton-proton collisions at âs= 7 TeV
The production cross-sections of B mesons are measured in pp collisions at a centre-of-mass energy of 7 TeV using data collected with the LHCb detector corresponding to a integrated luminosity of 0.36fbâ1. The B+, B0 and B0s mesons are reconstructed in the exclusive decays B+âJ/ÏK+, B0âJ/ÏKâ0 and B0sâJ/ÏÏ, with J/ÏâÎŒ+ÎŒâ, Kâ0âK+Ïâ and ÏâK+Kâ. The differential cross-sections are measured as functions of B meson transverse momentum pT and rapidity y, in the range 0 < pT<40GeV/c2 and 2.0<y<4.5. The integrated cross-sections in the same pT and y ranges, including charge-conjugate states, are measured to be
Ï(ppâB++X)=38.9±0.3(stat.)±2.5(syst.)±1.3(norm.)ÎŒb,
Ï(ppâB0+X)=38.1±0.6(stat.)±3.7(syst.)±4.7(norm.)ÎŒb,
Ï(ppâB0s+X)=10.5±0.2(stat.)±0.8(syst.)±1.0(norm.)ÎŒb,
where the third uncertainty arises from the pre-existing branching fraction measurements
Study of B0(s)âK0Sh+hâČâ decays with first observation of B0sâK0SK±Ïâ and B0sâK0SÏ+Ïâ
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 fbâ1, collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B0(s)âK0Sh+hâČâ decay modes (h (âČ) = Ï, K), relative to the well measured B0âK0SÏ+Ïâ decay, are obtained. First observation of the decay modes B0sâK0SK±Ïâ and B0sâK0SÏ+Ïâ and confirmation of the decay B0âK0SK±Ïâ are reported. The following relative branching fraction measurements or limits are obtained B(B0âK0SK±Ïâ)B(B0âK0SÏ+Ïâ)=0.128±0.017(stat.)±0.009(syst.), B(B0âK0SK+Kâ)B(B0âK0SÏ+Ïâ)=0.385±0.031(stat.)±0.023(syst.), B(B0sâK0SÏ+Ïâ)B(B0âK0SÏ+Ïâ)=0.29±0.06(stat.)±0.03(syst.)±0.02(fs/fd), B(B0sâK0SK±Ïâ)B(B0âK0SÏ+Ïâ)=1.48±0.12(stat.)±0.08(syst.)±0.12(fs/fd)B(B0sâK0SK+Kâ)B(B0âK0SÏ+Ïâ)â[0.004;0.068]at90%CL
Observation of Bc+âJ/ÏDs+ and Bc+âJ/ÏDs*+ decays
The decays Bc+âJ/ÏDs+ and Bc+âJ/ÏDs*+ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3ââfb-1, collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of âs=7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be B(Bc+âJ/ÏDs+)/B(Bc+âJ/ÏÏ+)=2.90±0.57±0.24, B(Bc+âJ/ÏDs*+)/B(Bc+âJ/ÏDs+)=2.37±0.56±0.10, where the first uncertainties are statistical and the second systematic. The mass of the Bc+ meson is measured to be mBc+=6276.28±1.44(stat)±0.36(syst)ââMeV/c2, using the Bc+âJ/ÏDs+ decay mode
Observation of the decay
The decay is observed for the first
time, using proton-proton collisions collected with the LHCb detector
corresponding to an integrated luminosity of 3fb. A signal yield of
decays is reported with a significance of 6.2 standard deviations.
The ratio of the branching fraction of \B_c \rightarrow J/\psi K^+ K^- \pi^+
decays to that of decays is measured to be
, where the first uncertainty is statistical and the
second is systematic.Comment: 18 pages, 2 figure
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
- âŠ