A study of B+c→K+K−π+ decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in pp collisions at centre-of-mass ...energies of 7 and 8 TeV. Evidence for the decay B+c→χc0(→K+K−)π+ is reported with a significance of 4.0 standard deviations, resulting in the measurement of σ(B+c)σ(B+)×B(B+c→χc0π+) to be (9.8+3.4−3.0(stat)±0.8(syst))×10−6. Here B denotes a branching fraction while σ(B+c) and σ(B+) are the production cross-sections for B+c and B+ mesons. An indication of b¯c weak annihilation is found for the region m(K−π+)<1.834GeV/c2, with a significance of 2.4 standard deviations.
Amorphous hydrogenated carbon−lead films (a-Pb X C Y :H) were produced by plasma chemical vapor deposition (PE CVD) in an audio-frequency (af) three-electrode reactor using tetraethyllead as a source ...compound. The negative amplitude of af voltage, V ( - ), measured on a small electrode, on which the films were deposited, with respect to the ground was the only operational parameter of the deposition process. V ( - ) was changed in the range of 0−1150 V. Investigations on electrical and optical properties, chemical structure, and morphology of the films were carried out. It has been found that a change in V ( - ) of about 100 V brings about rapid changes in the electrical conductivity (from 10-14 to 10-4 S/m), its activation energy (from 0.5 eV to the nonactivated process), and the optical gap (from about 3.0 to 1.3 eV). On the other hand, any drastic changes have not been observed in the chemical structure. This effect has been attributed to the amorphous insulator−amorphous semiconductor transition. It has been suggested that the transition effect is closely connected with the film cross-linking and Pb−C bonds play an important part in this process. The role of oxygen that is embedded into the film structures during the deposition process and the aging processes proceeding in the films under air treatment have been also discussed.
The CP asymmetry in the mixing of B0s and B̅0s mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, recorded by the LHCb experiment at ...centre-of-mass energies of 7 and 8 TeV. Semileptonic B0s and B̅0s decays are studied in the inclusive mode D∓sμ±νμX with the D∓s mesons reconstructed in the K+K−π∓ final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be assl=(0.39±0.26±0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of assl to date, and is consistent with the prediction from the Standard Model of particle physics.
Using a data set corresponding to an integrated luminosity of 3fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the ...B0s→J/ψη decay mode, τeff, is measured to be τeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the lifetime of the light B0s mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.
Measurements of the differential branching fraction and angular moments of the decay B0→K+π−μ+μ− in the K∗0,2(1430)0 in the K+π− invariant mass range 1330<m(K+π−)<1530 MeV/c2 are presented. ...Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q2, between 0.1 and 8.0 GeV2/c4. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q2 range 1.1--6.0 GeV2/c4.
The polarization of photons produced in radiative B-s(0) decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity ...of 3 fb(-1) at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B-s(0) ->phi gamma decay rate is conducted to determine the parameter A(Delta), which is related to the ratio of right-over left-handed photon polarization amplitudes in b -> s gamma transitions. A value of A(Delta) = -0.98(-0.52)(-0.20)(+0.46)(+0.23) is measured. This result is consistent with the standard model prediction within 2 standard deviations.
A measurement of the cross-section for W→eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2fb−1 collected by the LHCb experiment at a centre-of-mass ...energy of s√=8TeV. The electrons are required to have more than 20GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be \sigma_{W^{+} \to e^{+}\nu_{e}}&=1124.4\pm 2.1\pm 21.5\pm 11.2\pm 13.0\,\mathrm{pb}, \sigma_{W^{-} \to e^{-}\bar{\nu}_{e}}&=\,\,\,809.0\pm 1.9\pm 18.1\pm\,\,\,7.0\pm \phantom{0}9.4\,\mathrm{pb}, where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W+/W− cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be \mathcal{B}(W \to e\nu)/\mathcal{B}(W \to \mu\nu)=1.020\pm 0.002\pm 0.019, where the first uncertainty is statistical and the second is systematic.
Two-Particle correlations in pp, pbarpbar and K0sK0s pairs have been studied in hadronic Z decays recorded at LEP with the ALEPH detector. The correlations were measured as a function of the ...four-momentum difference Q of the pair. For pp, pbarpbar pairs a depletion of events is observed in the region Q < 3 GeV, and for K0sK0s pairs an enhancement of events is observed in the region Q < 0.5 GeV. These features are consistent with expectations from Fermi-Dirac and Bose-Einstein statistics, respectively.
A time-dependent angular analysis of B0s→ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0\invfb collected during Run ...1 of the LHC. The CP-violating phase and decay-width difference of the B0s system are measured to be ϕs=0.23+0.29−0.28±0.02 rad and ΔΓs=0.066+0.041−0.044±0.007 ps−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the ψ(2S) resonance.
PDF
