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.
The $B_s^0 \rightarrow J/\psi \phi \phi$ decay is observed in $pp$ collision data corresponding to an integrated luminosity of 3 fb$^{-1}$ recorded by the LHCb detector at centre-of-mass energies of ...7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the $B_s^0$ meson is measured to be $5367.08\,\pm \,0.38\,\pm\, 0.15$ MeV/c$^2$. The branching fraction ratio $\mathcal{B}(B_s^0 \rightarrow J/\psi \phi \phi)/\mathcal{B}(B_s^0 \rightarrow J/\psi \phi)$ is measured to be $0.0115\,\pm\, 0.0012\, ^{+0.0005}_{-0.0009}$. In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant $B_s^0 \rightarrow J/\psi \phi K^+ K^-$ or $B_s^0 \rightarrow J/\psi K^+ K^- K^+ K^-$ decays is found.
An angular analysis of the $B^{0}\rightarrow K^{*0}(\rightarrow K^{+}\pi^{-})\mu^{+}\mu^{-}$ decay is presented. The dataset corresponds to an integrated luminosity of $3.0\,{\mbox{fb}^{-1}}$ of $pp$ ...collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine $C\!P$-averaged observables and $C\!P$ asymmetries, taking account of possible contamination from decays with the $K^{+}\pi^{-}$ system in an S-wave configuration. The angular observables and their correlations are reported in bins of $q^2$, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for $q^2$-dependent decay amplitudes in the region $1.1<q^{2}<6.0\mathrm{\,Ge\kern -0.1em V}^{2}/c^{4}$, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of $C\!P$-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
A search for B0(s)→K0SK∗(892)0 decays is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 ...TeV. The B0s→K0SK∗(892)0 decay is observed for the first time, with a significance of 7.1 standard deviations. The branching fraction is measured to beB(B0s→K0SK∗(892)0)=(10.9±2.5±1.2)×10−6,where the first uncertainty is statistical and the second is systematic. No evidence is found for the decay B0→K0SK∗(892)0 and an upper limit is set on the branching fraction, B(B0→K0SK∗(892)0)<0.64 ×10−6, at 90% confidence level. All results are consistent with Standard Model predictions.
The first observation of the B0s→D¯0K0S decay mode and evidence for the B0s→D¯∗0K0S decay mode are reported. The data sample corresponds to an integrated luminosity of 3.0 fb−1 collected in pp ...collisions by LHCb at center-of-mass energies of 7 and 8 TeV. The branching fractions are measured to beB(B0s→D¯0K¯0)B(B0s→D¯∗0K¯0)=(4.3±0.5(stat)±0.3(syst)±0.3(frag)±0.6(norm))×10−4,=(2.8±1.0(stat)±0.3(syst)±0.2(frag)±0.4(norm))×10−4,where the uncertainties are due to contributions coming from statistical precision, systematic effects, and the precision of two external inputs, the ratio fs/fd and the branching fraction of B0→D¯0K0S, which is used as a calibration channel.
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