Abstract:

The first observation of the B_{s}^{0}→D[over ¯]^{0}K_{S}^{0} decay mode and evidence for the B_{s}^{0}→D[over ¯]^{*0}K_{S}^{0} 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 be B(B_{s}^{0}→D[over ¯]^{0}K[over ¯]^{0})=[4.3±0.5(stat)±0.3(syst)±0.3(frag)±0.6(norm)]×10^{-4},B(B_{s}^{0}→D[over ¯]^{*0}K[over ¯]^{0})=[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 f_{s}/f_{d} and the branching fraction of B^{0}→D[over ¯]^{0}K_{S}^{0}, which is used as a calibration channel.

Abstract:

The TORCH detector is being developed for low-momentum particle identification, combining time-of-flight and Cherenkov techniques to achieve charged particle pi/K/p separation up to 10 GeV/c over a flight distance of 10m. This requires a timing resolution of 70 ps for single photons. Based on an existing scalable design, production and testing of a TORCH readout system has been undertaken over the past year, and a novel customized Micro Channel Plate (MCP) photomultiplier device with 128-channels has been instrumented. This paper will report on the development of the readout system which is being used to measure time-of-flight in a test-beam, and its performance. We will also discuss the communication and data alignment between the TORCH system and the TimePix3 telescope in order to provide track reconstruction.

Abstract:

The first model-independent measurement of the charm mixing parameters in the decay $D^0 \to K_S \pi^+ \pi^-$ is reported, using a sample of $pp$ collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ at a centre-of-mass energy of 7 TeV. The measured values are \begin{eqnarray*} x and=and (-0.86 \pm 0.53 \pm 0.17) \times 10^{-2}, \\ y and=and (+0.03 \pm 0.46 \pm 0.13) \times 10^{-2}, \end{eqnarray*} where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic.

Abstract:

Amplitude models are applied to studies of resonance structure in D0→KS0K-π+ and D0→KS0K+π- decays using pp collision data corresponding to an integrated luminosity of 3.0 fb-1 collected by the LHCb experiment. Relative magnitude and phase information is determined, and coherence factors and related observables are computed for both the whole phase space and a restricted region of 100 MeV/c2 around the K∗(892)± resonance. Two formulations for the Kπ S-wave are used, both of which give a good description of the data. The ratio of branching fractions B(D0→KS0K+π-)/B(D0→KS0K-π+) is measured to be 0.655±0.004(stat)±0.006(syst) over the full phase space and 0.370±0.003(stat)±0.012(syst) in the restricted region. A search for CP violation is performed using the amplitude models and no significant effect is found. Predictions from SU(3) flavor symmetry for K∗(892)K amplitudes of different charges are compared with the amplitude model results.

Abstract:

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 TeV. The data sample corresponds to an integrated luminosity of 4.98 ± 0.19 pb⁻¹ collected by the LHCb experiment. The production cross-sections of D⁰, D⁺, D_s⁺, and D^*+ mesons are measured in bins of charm meson transverse momentum, p_T, and rapidity, y, and cover the range 0 < p_T < 15GeV/c and 2.0 < y < 4.5. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of 1 < p_T < 8 GeV/c are found to be
σ(pp →D⁰X) = 2460 ± 3 ± 130 μb
σ(pp →D⁺X) = 1000 ± 3 ± 110 μb
σ(pp →D⁺_sX) = 460 ± 13 ± 100 μb
σ(pp →D^∗+X)=880 ± 5 ± 140 μb
where the uncertainties are due to statistical and systematic uncertainties, respectively.