Sneha Malde

Abstract:

A comprehensive study of the local and nonlocal amplitudes contributing to the decay B0 → K*0(→ K+π−)μ+μ− is performed by analysing the phase-space distribution of the decay products. The analysis is based on pp collision data corresponding to an integrated luminosity of 8.4 fb−1 collected by the LHCb experiment. This measurement employs for the first time a model of both one-particle and two-particle nonlocal amplitudes, and utilises the complete dimuon mass spectrum without any veto regions around the narrow charmonium resonances. In this way it is possible to explicitly isolate the local and nonlocal contributions and capture the interference between them. The results show that interference with nonlocal contributions, although larger than predicted, only has a minor impact on the Wilson Coefficients determined from the fit to the data. For the local contributions, the Wilson Coefficient C9, responsible for vector dimuon currents, exhibits a 2.1σ deviation from the Standard Model expectation. The Wilson Coefficients C10, C9′ and C10′ are all in better agreement than C9 with the Standard Model and the global significance is at the level of 1.5σ. The model used also accounts for nonlocal contributions from B0→ K*0[τ+τ−→ μ+μ−] rescattering, resulting in the first direct measurement of the bsττ vector effective-coupling C9τ.

Abstract:

Using e+e− annihilation data sets corresponding to an integrated luminosity of 4.5 fb−1, collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions BΛc+→pKL0 = (1.67 ± 0.06 ± 0.04)%, BΛc+→pKL0π+π− = (1.69 ± 0.10 ± 0.05)%, and BΛc+→pKL0π0 = (2.02 ± 0.13 ± 0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of Λc+→pKS0, Λc+→pKS0π+π−, and Λc+→pKS0π0, we present the first measurements of the KS0-KL0 asymmetries RΛc+KS, L0X=BΛc+→KS0X−BΛc+→KL0XBΛc+→KS0X+BΛc+→KL0X in charmed baryon decays: RΛc+pKS, L0=−0.025±0.031, RΛc+pKS, L0π+π−=−0.027±0.048 and RΛc+pKS, L0π0=−0.015±0.046. No significant asymmetries with statistical significance are observed.

Abstract:

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×106.