1,130 research outputs found
Angular analysis and differential branching fraction of the decay B {/s 0} â ÏÎŒ + ÎŒ -
An angular analysis and a measurement of the differential branching fraction of the decay B0 s â Ï”+” â are presented, using data corresponding to an integrated luminosity of 3.0 fbâ1 of pp collisions recorded by the LHCb experiment at â s = 7 and 8 TeV. Measurements are reported as a function of q 2 , the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1 < q2 < 6 GeV2/c4 , where precise theoretical calculations are available, the differential branching fraction is found to be more than 3 Ï below the Standard Model predictions
Observation of the B0 âÏ0Ï0 decay from an amplitude analysis of B0 â (Ï+Ï-) (Ï+Ï-) decays
Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fbâ1 , are analysed to search for the charmless B0 â Ï 0Ï 0 decay. More than 600 B0 â (Ï +Ï â)(Ï +Ï â) signal decays are selected and used to perform an amplitude analysis, under the assumption of no CP violation in the decay, from which the B0 â Ï 0Ï 0 decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0 â Ï 0Ï 0 decays yielding a longitudinally polarised final state is measured to be fL = 0.745+0.048 â0.058(stat) ± 0.034(syst). The B0 â Ï 0Ï 0 branching fraction, using the B0 â ÏKâ (892)0 decay as reference, is also reported as B(B0 â Ï 0Ï 0 ) = (0.94 ± 0.17(stat) ± 0.09(syst) ± 0.06(BF)) Ă 10â6
Searches for Î0b and Î0b decays to K0SpÏâ and K0SpKâ final states with first observation of the Î0bâK0SpÏâ decay
A search for previously unobserved decays of beauty baryons to the final states K0 S pÏâ and K0 S pKâ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fbâ1 of pp collisions. The Î 0 b â K0pÏâ decay is observed with a significance of 8.6 Ï, with branching fraction B(Î 0 b â K0 pÏâ) = (1.26 ± 0.19 ± 0.09 ± 0.34 ± 0.05) Ă 10â5 , where the uncertainties are statistical, systematic, from the ratio of fragmentation fractions fÎ0 b /fd, and from the branching fraction of the B0â K0Ï +Ï â normalisation channel, respectively. A first measurement is made of the CP asymmetry, giving ACP (Î 0 b â K0 pÏâ) = 0.22 ± 0.13 (stat) ± 0.03 (syst). No significant signals are seen for Î 0 b â K0 S pKâ decays, Î0 b decays to both the K0 S pÏâ and K0 S pKâ final states, and the Î 0 b â Dâ s (â K0 SKâ)p decay, and upper limits on their branching fractions are reported
Observation of Z production in proton-lead collisions at LHCb
The first observation of Z boson production in proton-lead collisions at a centreof-mass energy per proton-nucleon pair of â sNN = 5 TeV is presented. The data sample corresponds to an integrated luminosity of 1.6 nbâ1 collected with the LHCb detector. The Z candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV/c. The invariant dimuon mass is restricted to the range 60 â 120 GeV/c2 . The Z production cross-section is measured to be ÏZâ”+”â (fwd) = 13.5 +5.4 â4.0 (stat.) ± 1.2(syst.) nb in the direction of the proton beam and ÏZâ”+”â (bwd) = 10.7 +8.4 â5.1 (stat.) ± 1.0(syst.) nb in the direction of the lead beam, where the first uncertainty is statistical and the second systematic
Quantum numbers of the X (3872 ) state and orbital angular momentum in its Ï0J /Ï decay
Angular correlations in B+ â X(3872)K+ decays, with X(3872) â Ï 0J/Ï, Ï 0 â Ï +Ï â and J/Ï â ” +” â, are used to measure orbital angular momentum contributions and to determine the J P C value of the X(3872) meson. The data correspond to an integrated luminosity of 3.0 fbâ1 of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be J P C = 1++. The X(3872) is found to decay predominantly through S wave and an upper limit of 4% at 95% C.L. is set on the D-wave contribution
Dalitz plot analysis of B0âDÂŻ0Ï+Ï- decays
The resonant substructures of B0 â D0Ï +Ï â decays are studied with the Dalitz plot technique. In this study a data sample corresponding to an integrated luminosity of 3.0 fbâ1 of pp collisions collected by the LHCb detector is used. The branching fraction of the B0 â D0Ï +Ï â decay in the region m(D0Ï Â±) > 2.1 GeV/c2 is measured to be (8.46 ± 0.14 ± 0.29 ± 0.40) Ă 10â4 , where the first uncertainty is statistical, the second is systematic and the last arises from the normalisation channel B0 â Dâ (2010)âÏ +. The Ï +Ï â S-wave components are modelled with the Isobar and K-matrix formalisms. Results of the Dalitz plot analyses using both models are presented. A resonant structure at m(D0Ï â) â 2.8 GeV/c2 is confirmed and its spin-parity is determined for the first time as J P = 3â. The branching fraction, mass and width of this structure are determined together with those of the Dâ 0 (2400)â and Dâ 2 (2460)â resonances. The branching fractions of other B0 â D0h 0 decay components with h 0 â Ï +Ï â are also reported. Many of these branching fraction measurements are the most precise to date. The first observation of the decays B0 â D0f0(500), B0 â D0f0(980), B0 â D0Ï(1450), B0 â Dâ 3 (2760)âÏ + and the first evidence of B0 â D0f0(2020) are presented
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
Measurement of the relative rate of prompt Ïc0, Ïc1 and Ïc2 production at âs=7TeV
Prompt production of charmonium Ïc0, Ïc1 and Ïc2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of âs=7TeV. The Ïc mesons are identified through their decay to J/ÏÎł, with J/ÏâÎŒ+muâ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0fbâ1 collected by the LHCb detector, is used to measure the relative prompt production rate of Ïc1 and Ïc2 in the rapidity range 2.0<y<4.5 as a function of the J/Ï transverse momentum from 3 to 20 GeV/c. First evidence for Ïc0 meson production at a hadron collider is also presented
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
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
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