Λb decays into Λ-vector Ajaltouni, Z.J.; Conte, E.; Leitner, O.
Physics letters. B,
05/2005, Letnik:
614, Številka:
3-4
Journal Article
Recenzirano
Odprti dostop
A complete study of the angular distributions of the processes, Λb→ΛV(1−), with Λ→pπ− and V(J/Ψ)→ℓ+ℓ− or V(ρ0)→π+π−, is performed. Emphasis is put on the initial Λb polarization produced in the ...proton–proton collisions. The polarization density-matrices as well as angular distributions are derived and help to construct T-odd observables which allow us to perform tests of both time-reversal and CP violation.
A study of the angular distributions of the processes
Λ
b
→
Λ
V
(
1
−
)
with
V
(
J
/
Ψ
,
ρ
0
)
is performed. Emphasis is put on the initial
Λ
b
polarization and the polarization density-matrices are ...derived to perform tests of both Time-Reversal (TR) and
CP violation.
The decay B¯¯¯0s→ψ(2S)K+π− is observed using a data set corresponding to an integrated luminosity of 3.0fb−1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 ...TeV. The branching fraction relative to the B0→ψ(2S)K+π− decay mode is measured to beB(B¯¯¯0s→ψ(2S)K+π−)B(B0→ψ(2S)K+π−)=5.38±0.36(stat)±0.22(syst)±0.31(fs/fd)%,where fs/fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into a B0s or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate K∗(892)0 meson is measured to be 0.645±0.049(stat)±0.049(syst) and its longitudinal polarisation fraction is 0.524±0.056(stat)±0.029(syst). The relative branching fraction for this component is determined to beB(B¯¯¯0s→ψ(2S)K∗(892)0)B(B0→ψ(2S)K∗(892)0)=5.58±0.57(stat)±0.40(syst)±0.32(fs/fd)%.In addition, the mass splitting between the B0s and B0 mesons is measured asM(B0s)−M(B0)=87.45±0.44(stat)±0.07(syst)MeV/c2.
A search for the rare decays B0s→π+π−μ+μ− and B0→π+π−μ+μ− is performed in a data set corresponding to an integrated luminosity of 3.0 fb−1 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 B0s→π+π−μ+μ− and the first evidence of the decay B0→π+π−μ+μ− are obtained and the branching fractions are measured to be B(B0s→π+π−μ+μ−)=(8.6±1.5(stat)±0.7(syst)±0.7(norm))×10−8 and B(B0→π+π−μ+μ−)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))×10−8, where the third uncertainty is due to the branching fraction of the decay B0→J/ψ(→μ+μ−)K∗(890)0(→K+π−), used as a normalisation.
Using 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.
The difference in total widths between the B+c and B+ mesons is measured using 3.0fb−1 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+c→J/ψπ+ and B+→J/ψK+ decays, the width difference is measured to beΔΓ≡ΓB+c−ΓB+=4.46±0.14±0.07mm−1c,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,τB+c=513.4±11.0±5.7fs,where the first uncertainty is statistical and the second systematic.
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