The suppressed decay Λ0b→pπ−μ+μ−, excluding the J/ψ and ψ(2S)→μ+μ− resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with ...proton-proton collision data corresponding to an integrated luminosity of 3fb−1 collected with the LHCb experiment. The Λ0b→pπ−μ+μ− branching fraction is measured relative to the Λ0b→J/ψ(→μ+μ−)pπ− branching fraction givingB(Λ0b→pπ−μ+μ−)B(Λ0b→J/ψ(→μ+μ−)pπ−)=0.044±0.012±0.007,where the first uncertainty is statistical and the second is systematic. This is the first observation of a b→d transition in a baryonic decay.
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 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.
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.
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 model-dependent amplitude analysis of the decay B0→D(K0Sπ+π−)K∗0 is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0fb−1, recorded at s√=7 and 8TeV by ...the LHCb experiment. The CP violation observables x± and y±, sensitive to the CKM angle γ, are measured to bex−=−0.15±0.14±0.03±0.01,y−=0.25±0.15±0.06±0.01,x+=0.05±0.24±0.04±0.01,y+=−0.65+0.24−0.23±0.08±0.01,where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the D→K0Sπ+π− amplitude model. These are the most precise measurements of these observables. They correspond to γ=(80+21−22)∘ and rB0=0.39±0.13, where rB0 is the magnitude of the ratio of the suppressed and favoured B0→DK+π− decay amplitudes, in a Kπ mass region of ±50MeV around the K∗(892)0 mass and for an absolute value of the cosine of the K∗0 decay angle larger than 0.4.
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.
The data sample of Λ0b→J/ψpK− decays acquired with the LHCb detector from 7 and 8~TeV pp collisions, corresponding to an integrated luminosity of 3 fb−1, is inspected for the presence of J/ψp or ...J/ψK− contributions with minimal assumptions about K−p contributions. It is demonstrated at more than 9 standard deviations that Λ0b→J/ψpK− decays cannot be described with K−p contributions alone, and that J/ψp contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for P+c→J/ψp charmonium-pentaquark states in the same data sample.
Production cross-sections of prompt charm mesons are measured with the first data from $pp$ collisions at the LHC at a centre-of-mass energy of $13\,\mathrm{TeV}$. The data sample corresponds to an ...integrated luminosity of $4.98 \pm 0.19\,\mathrm{pb}^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^{0}$, $D^{+}$, $D_{s}^{+}$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\mathrm{T}}$, and rapidity, $y$, and cover the range $0 < p_{\mathrm{T}} < 15\,\mathrm{GeV}/c$ and $2.0 < y < 4.5$. The ratios of the integrated cross-sections between charm mesons agree with previously measured fragmentation fractions. The inclusive $c\overline{c}$ cross-section within the range of $0 < p_{\mathrm{T}} < 8\,\mathrm{GeV}/c$ is found to be \ \sigma(pp \to c\overline{c}X) = 2940 \pm 3 \pm 180 \pm 160\,\mu\mathrm{b} \ where the uncertainties are due to statistical, systematic and fragmentation fraction uncertainties, respectively.
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