967 research outputs found
Review of direct CP violation in two and three body B decays at LHCb
Charmless B hadrons decays offer rich opportunities to test the Standard
Model. CP violation in charmless charged two-body and three-body B decays
provides ways to measure the CKM angle and to search for New Physics.
Also, vector-vector final states provide additional interesting observables.
Hereby, we present the latest LHCb results on hadronic charmless B decays
putting emphasis on the direct CP violation measurements.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity
Triangle (CKM 2014), Vienna, Austria, September 8-12, 201
A study of the Z production cross-section in pp collisions at sâ=7 TeV using tau final states
A measurement of the inclusive Z â ÏÏ cross-section in pp collisions at sâ=7TeV is presented based on a dataset of 1.0 fbâ1 collected by the LHCb detector. Candidates for Z â Ï Ï decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c 2, which decay to Ï leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be Ï ppâZâÏÏ = 71.4 ± 3.5 ± 2.8 ± 2.5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z â Ï Ï to Z â ΌΌ is determined to be 0.93 ± 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements
Measurement of relative branching fractions of B decays to Ï(2S) and J/Ï mesons
The relative rates of B-meson decays into J/Ï and Ï(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions ( B) are measured to be where the third uncertainty is from the ratio of the Ï(2S) and J/Ï branching fractions to ÎŒ + ÎŒ â
Determination of gamma and -2beta_s from charmless two-body decays of beauty mesons
See paper for full list of authorsInternational audienceUsing the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> \pi^+\pi^- decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2\beta_s. Results from an extended approach, which uses additional inputs on B^0 -> \pi^0\pi^0 and B^+ -> \pi^+\pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value \gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2\beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included
Measurement of the CP-violating phase ÎČ in B0âJ/ÏÏ+Ïâ decays and limits on penguin effects
18 pages, 6 figures - See paper for full list of authorsInternational audienceTime-dependent CP violation is measured in the B0âJ/ÏÏ+Ïâ channel for each Ï+Ïâ resonant final state using data collected with an integrated luminosity of 3.0 fbâ1 in pp collisions using the LHCb detector. The final state with the largest rate, J/ÏÏ0(770), is used to measure the CP-violating angle 2ÎČeff to be (41.7±9.6+2.8â6.3)â. This result can be used to limit the size of penguin amplitude contributions to CP violation measurements in, for example, B0sâJ/ÏÏ decays. Assuming approximate SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the CP-violating phase Ïs is limited to be within the interval [â1.05â, +1.18â] at 95% confidence level. Changes to the limit due to SU(3) symmetry breaking effects are also discussed
Measurement of the lifetime of the B+c meson using the B+câJ/ÏÏ+ decay mode
See paper for full list of authors - 19 pages, 3 figuresInternational audienceThe difference in total widths between the B+c and B+ mesons is measured using 3.0fbâ1 of data collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of B+câJ/ÏÏ+ and B+âJ/ÏK+ decays, the width difference is measured to beÎÎâĄÎB+câÎB+=4.46±0.14±0.07mmâ1c,where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B+c lifetime,ÏB+c=513.4±11.0±5.7fs,where the first uncertainty is statistical and the second systematic
Study of the rare B0s and B0 decays into the Ï+ÏâÎŒ+ÎŒâ final state
See paper for full list of authors - Submitted to Phys. Lett. BInternational audienceA search for the rare decays B0sâÏ+ÏâÎŒ+ÎŒâ and B0âÏ+ÏâÎŒ+ÎŒâ is performed in a data set corresponding to an integrated luminosity of 3.0 fbâ1 collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0sâÏ+ÏâÎŒ+ÎŒâ and the first evidence of the decay B0âÏ+ÏâÎŒ+ÎŒâ are obtained and the branching fractions are measured to be B(B0sâÏ+ÏâÎŒ+ÎŒâ)=(8.6±1.5(stat)±0.7(syst)±0.7(norm))Ă10â8 and B(B0âÏ+ÏâÎŒ+ÎŒâ)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))Ă10â8, where the third uncertainty is due to the branching fraction of the decay B0âJ/Ï(âÎŒ+ÎŒâ)Kâ(890)0(âK+Ïâ), used as a normalisation
Measurement of the branching fraction
The branching fraction is measured in a data sample
corresponding to 0.41 of integrated luminosity collected with the LHCb
detector at the LHC. This channel is sensitive to the penguin contributions
affecting the sin2 measurement from The
time-integrated branching fraction is measured to be . This is the most precise measurement to
date
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
Opposite-side flavour tagging of B mesons at the LHCb experiment
The calibration and performance of the oppositeside
flavour tagging algorithms used for the measurements
of time-dependent asymmetries at the LHCb experiment
are described. The algorithms have been developed using
simulated events and optimized and calibrated with
B
+ âJ/ÏK
+, B0 âJ/ÏK
â0 and B0 âD
ââ
Ό
+
ΜΌ decay
modes with 0.37 fbâ1 of data collected in pp collisions
at
â
s = 7 TeV during the 2011 physics run. The oppositeside
tagging power is determined in the B
+ â J/ÏK
+
channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty
is statistical and the second is systematic
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