Sneha Malde

Abstract:

By analysing e+e− annihilation data corresponding to an integrated luminosity of 368.48 pb−1 collected at the centre-of-mass energies of s = 4.918 and 4.951 GeV with the BESIII detector, we report the first observation of Λc(2595)+ and Λc(2625)+ → Λc+π0π0 with statistical significances of 7.9σ and 11.8σ, respectively. The branching fractions of Λc(2595)+ and Λc(2625)+ → Λc+π0π0 are measured to be (59.5 ± 11.1stat. ± 7.9syst.)% and (41.0 ± 5.2stat. ± 3.3syst.)%, respectively. The absolute branching fraction of Λc(2595)+ is consistent with the expectation of the mechanism referred to as the threshold effect, proposed for the strong decays of Λc(2595)+ within uncertainty.

Abstract:

Using $20.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of $E_{\mathrm{c}\mathrm{.}\mathrm{m}\mathrm{.}}=3.773\mathrm{GeV}$ with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay $D^{+}\to {\mu }^{+}{\nu }_{\mu }$ to be $(4.034\pm 0.080_{\mathrm{stat}}\pm 0.040_{\mathrm{syst}})\times {10}^{-4}$ . Interpreting our measurement with knowledge of the Fermi coupling constant $G_F$ , the masses of the $D^{+}$ and ${\mu }^{+}$ as well as the lifetime of the $D^{+}$ , we determine $f_{D^{+}}|V_{cd}|=(48.02\pm 0.48_{\mathrm{stat}}\pm 0.24_{\mathrm{syst}}\pm 0.12_{\text{input}}\pm 0.15_{\mathrm{EM}})\mathrm{MeV}$ after taking into account necessary radiative corrections. This result is a factor of 2.3 more precise than the previous best measurement. Using the value of the magnitude of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ given by the global standard model fit, we obtain the $D^{+}$ decay constant $f_{D^{+}}=(213.5\pm {2.1}_{\mathrm{stat}}\pm {1.1}_{\mathrm{syst}}\pm {0.8}_{\text{input}}\pm {0.7}_{\mathrm{EM}})\mathrm{MeV}$ . Alternatively, using the value of $f_{D^{+}}$ from a precise lattice quantum chromodynamics calculation, we extract $|V_{cd}|=0.2265\pm 0.0023_{\mathrm{stat}}\pm 0.0011_{\mathrm{syst}}\pm 0.0009_{\text{input}}\pm 0.0007_{\mathrm{EM}}$ .

Abstract:

Using 20.3 fb–1 of annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report on an improved search for the radiative leptonic decay . An upper limit on its partial branching fraction for photon energies MeV was determined to be at a 90% confidence level; this excludes most current theoretical predictions. A sophisticated deep learning approach, which includes thorough validation and is based on the Transformer architecture, was implemented to efficiently distinguish the signal from massive backgrounds.

Abstract:

The first observation of the Ξb0 → J/ψΞ− π+ decay and the most precise measurement of the branching fraction of the Λb0 → J/ψΞ− K+ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1. Using the Λb0 → J/ψΛ and Ξb0 → J/ψΞ− decays as normalisation channels, the ratios of branching fractions are measured to be B(Λb0 → J/ψΞ− K+)/B(Λb0 → J/ψΛ) = (1.17 ± 0.14 ± 0.08) × 10−2, B(Ξb0 → J/ψΞ− π+)/B(Ξb0 → J/ψΞ−) = (11.9 ± 1.4 ± 0.6) × 10−2, where the first uncertainty is statistical and the second systematic

Abstract:

The ratio of prompt production cross-sections of ψ(2S) and J/ψ mesons in their dimuon final state is measured as a function of centrality, using data collected by the LHCb detector in PbPb collisions at sNN = 5.02 TeV, for the first time in the forward rapidity region. The measured ratio shows no dependence on the collision centrality, and is compared to the latest theory predictions and to the recent measurements in literature.