32 research outputs found
Quantum numbers of the state and orbital angular momentum in its decay
Angular correlations in decays, with , and , are used to measure
orbital angular momentum contributions and to determine the value of
the meson. The data correspond to an integrated luminosity of 3.0
fb 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 .
The is found to decay predominantly through S wave and an upper limit
of at C.L. is set on the fraction of D wave.Comment: 16 pages, 4 figure
Model-independent evidence for contributions to decays
The data sample of decays acquired with the
LHCb detector from 7 and 8~TeV collisions, corresponding to an integrated
luminosity of 3 fb, is inspected for the presence of or
contributions with minimal assumptions about
contributions. It is demonstrated at more than 9 standard deviations that
decays cannot be described with
contributions alone, and that contributions play a dominant role in
this incompatibility. These model-independent results support the previously
obtained model-dependent evidence for charmonium-pentaquark
states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the
end
Measurement of CP Asymmetries and Branching Fractions in Charmless Two-Body B-Meson Decays to Pions and Kaons
We present improved measurements of CP-violation parameters in the decays
, , and , and of
the branching fractions for and . The
results are obtained with the full data set collected at the
resonance by the BABAR experiment at the PEP-II asymmetric-energy factory
at the SLAC National Accelerator Laboratory, corresponding to
million pairs. We find the CP-violation parameter values and
branching fractions where in each case, the first uncertainties are statistical
and the second are systematic. We observe CP violation with a significance of
6.7 standard deviations for and 6.1 standard deviations for
, including systematic uncertainties. Constraints on the
Unitarity Triangle angle are determined from the isospin relations
among the rates and asymmetries. Considering only the solution
preferred by the Standard Model, we find to be in the range
at the 68% confidence level.Comment: 18 pages, 11 postscript figures, submitted to Phys. Rev.
Observation of Z production in proton-lead collisions at LHCb
The first observation of Z boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of root(s) N N = 5TeV is presented. The data sample corresponds to an integrated luminosity of 1.6 nb(-1) 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 60-120 GeV/c. The Z production cross-section is measured to be sigma(Z ->mu+mu-) (fwd) = 13.5(-4.0)(+5.4)(stat.) +/- 1.2(syst.) nb in the direction of the proton beam and sigma(Z ->mu+mu-) (bwd) = 10.7(-5.1)(+8.4)(stat.) +/- 1.0(syst.) nb in the direction of the lead beam, where the first uncertainty is statistical and the second systematic
Measurement of the branching fraction and angular amplitudes
A search for the decay with is performed with 0.37 fb of collisions at
= 7 TeV collected by the LHCb experiment, finding a \Bs \to J\psi
K^-\pi^+ peak of signal events. The mass spectrum of
the candidates in the peak is dominated by the contribution.
Subtracting the non-resonant component, the branching fraction of
\BsJpsiKst is , where the first
uncertainty is statistical and the second systematic. A fit to the angular
distribution of the decay products yields the \Kst polarization fractions and
Measurement of CP violation and constraints on the CKM angle Îł in B± â DK± with D â K0SÏ+Ïâ decays
A model-dependent amplitude analysis of B± â DK± with D â K0
SÏ+Ïâ decays is performed using
protonâproton collision data, corresponding to an integrated luminosity of 1 fbâ1, recorded by LHCb at
a centre-of-mass energy of 7 TeV in 2011. Values of the CP violation observables x± and y±, which are
sensitive to the CKM angle Îł, are measured to be
xâ = +0.027 ± 0.044+0.010 â0.008 ± 0.001,
yâ = +0.013 ± 0.048+0.009 â0.007 ± 0.003,
x+ = â0.084 ± 0.045 ± 0.009 ± 0.005,
y+ = â0.032 ± 0.048+0.010 â0.009 ± 0.008,
where the first uncertainty is statistical, the second systematic and the third arises from the uncertainty of
the D â K0
SÏ+Ïâ amplitude model. The value of Îł is determined to be (84+49
â42)âŠ, including all sources
of uncertainty. Neutral D meson mixing is found to have negligible effect
Framework TDR for the LHCb Upgrade
This document is a Framework Technical Design Report for the upgrade of the LHCb experiment. It adds to the information in the Letter of Intent, in particular concerning the foreseen schedule, cost and participating institutes. Updates are given for the physics performance, based on the experience gained with the first full year of data taking, on the detector requirements and the progress of the sub-system R&D. Within the framework presented here, it is expected that the individual sub-system TDRs will follow on completion of the R&D phase in the next year
Observation of Excited Lambda(0)(b) Baryons
Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda0b pi+ pi- spectrum with masses 5911.97+-0.12(stat)+-0.02(syst)+- 0.66(Lambda0b mass) MeV/c2 and 5919.77+-0.08(stat)+-0.02(syst)+-0.66(Lambda0b mass) MeV/c2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally excited Lambda0b baryons, Lambda*0b(5912) and Lambda*0b(5920)
Precision measurement of the ratio of the Lambda(0)(b) to (B)over-bar(0) lifetimes
The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the (B) over bar (0) lifetime, the Lambda(0)(b) lifetime is found to be 1.479 +/- 0.009 +/- 0.010 ps