2,272 research outputs found
Measurement of the CKM angle Îł from a combination of B±âDh± analyses
A combination of three LHCb measurements of the CKM angle Îł is presented. The decays B±âD K± and
B±âDϱ are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+Kâ, Ï+Ïâ, K±Ïâ, K±ÏâϱÏâ, K0SÏ+Ïâ, or K0S K+Kâ ïŹnal states. All measurements use a dataset corresponding to 1.0 fbâ1 of integrated luminosity. Combining results from B±âD K± decays alone a best-ïŹt value of
Îł =72.0⊠is found, and conïŹdence intervals are set
Îł â [56.4,86.7]⊠at 68% CL,
Îł â [42.6,99.6]⊠at 95% CL.
The best-ïŹt value of Îł found from a combination of results from B±âDϱ decays alone, is Îł =18.9âŠ,
and the conïŹdence intervals
Îł â [7.4,99.2]⊠âȘ [167.9,176.4]⊠at 68% CL
are set, without constraint at 95% CL. The combination of results from B± â D K± and B± â Dϱ
decays gives a best-ïŹt value of Îł =72.6⊠and the conïŹdence intervals
Îł â [55.4,82.3]⊠at 68% CL,
Îł â [40.2,92.7]⊠at 95% CL
are set. All values are expressed modulo 180âŠ, and are obtained taking into account the effect of D0âD0
mixing
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
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
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+Ï+Ï- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bcâ(2S31)+ state reconstructed without the low-energy photon from the Bcâ(1S31)+âBc+Îł decay following Bcâ(2S31)+âBcâ(1S31)+Ï+Ï-. A second state is seen with a global (local) statistical significance of 2.2Ï (3.2Ï) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
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
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at âs=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
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
Searches for B0(s)âJ/ÏppË and B+âJ/ÏppËÏ+ decays
The results of searches for B0(s)âJ/Ï ppÂŻ and B + â J/Ï p pÂŻ Ï+ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fbâ1 of pp collisions, collected with the LHCb detector. An excess with 2.8 Ï significance is seen for the decay B0sâJ/Ï ppÂŻ and an upper limit on the branching fraction is set at the 90 % confidence level: B(B0sâJ/Ï ppÂŻ) < 4.8 Ă 10â6, which is the first such limit. No significant signals are seen for B0 â J/Ï ppÂŻ and B+ â J/Ï ppÂŻ Ï + decays, for which the corresponding limits are set: B(B0âJ/Ï ppÂŻ) < 5.2 Ă 10â7, which significantly improves the existing limit; and B(B+âJ/Ï ppÂŻÏ+) < 5.0 Ă 10â7, which is the first limit on this branching fraction
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
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