Rostomyan, A. | Search NASA

DOE OSTI2022

B-flavor tagging at Belle II

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom (B) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic B decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8fb -1 , collected at the Υ(4S) resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be ε eff = (30.0 ± 1.2(stat) ± 0.4(syst))% for a category-based algorithm and ε eff = (28.8 ± 1.2(stat) ± 0.4(syst))% for a deep learning-based algorithm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos ( Φ–Φ S ) modulations provide evidence for a sizable worm-gear (II) distribution, ${g}_{1\mathrm{T}}^q\left(x,{\mathrm{p}}_T^2\right)$. Most of the other modulations are found to be consistent with zero with the notable exception of large sin ( Φ S ) modulations for charged pions and K + .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗