Sneha Malde

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.

Abstract:

Study of ψ(2S) production and cold nuclear matter effects in pPb collisions at √s_NN = 5 TeV

The production of ψ(2S) mesons is studied in dimuon final states using proton-lead (pPb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1.6 nb⁻¹. The nucleon-nucleon centre-of-mass energy of the pPb collisions is √s_NN = 5 TeV. The measurement is performed using ψ(2S) mesons with transverse momentum less than 14 GeV/c and rapidity y in the ranges 1.5 < y < 4.0 and −5.0 < y < −2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for ψ(2S) mesons. Using the production cross- section results of ψ(2S) and J/ψ mesons from b-hadron decays, the bb̅ cross-section in pPb collisions at √s_NN = 5 TeV is obtained.

Abstract:

Observation of the B_s⁰ → J/ψϕϕ decay

The B_s⁰ → J/ψϕϕ 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_s⁰ meson is measured to be 5367.08 ± 0.38 ± 0.15 MeV/c². The branching fraction ratio 𝓑(B_s⁰ → J/ψϕϕ)/𝓑(B_s⁰ → J/ψϕ) is measured to be 0.0115 ± 0.0012 _−0.0009^+0.0005. In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant B_s⁰ → J/ψϕK⁺K⁻ or B_s⁰ → J/ψK⁺K⁻K⁺K⁻ decays is found.