Narrow Results

A brief review on the theoretical status of hadronic charm decays is presented. We emphasize the analyses based on the diagrammatic approach and the connection of weak annihilation with final-state rescattering. The topics on the mixing and the baryonic charm decay are sketched.

Mixing and CP violation in charm meson decays provide a unique probe of possible physics beyond the standard model. In this paper, we give a brief review of the current measurements from the BABAR experiment.

Based on 2.92 fb^-1 of e⁺e^- collision data collected with the BESIII detector at GeV, we measured the asymmetry of the branching fractions of D^CP± → K^-π⁺ (D^CP± are the CP-odd and CP-even eigenstates) to be . is used to extract the strong phase difference δ_Kπ between the doubly Cabibbo-suppressed process and Cabibbo-favored D⁰ → K^-π⁺. By taking inputs of other parameters in world measurements, we obtain cosδ_Kπ = 1.03 ± 0.12 ± 0.04 ± 0.01. This is the most accurate result of cosδ_Kπ to date and can improve the world constrains on the mixing parameters and on γ/ϕ₃ in the CKM matrix.

Recent results on mixing, CP violation and rare decays in charm physics from the LHCb experiment are presented. Study of "wrong-sign" D⁰ → K⁺π^- decays provides the highest precision measurements to date of the mixing parameters x′² and y′, and of CP violation in this decay mode. Direct and indirect CP violation in the D⁰ system are probed to a sensitivity of around 10^-3 using D⁰ → K⁺K⁻ and D⁰ → π⁺π⁻ decays and found to be consistent with zero. Searches for the rare decays , and D⁰ → μ⁺μ⁻ find no evidence of signal, but set the best limits on branching fractions to date. Thus, despite many excellent results in charm physics from LHCb, no evidence for physics beyond the Standard Model is found.

Since the discovery of neutrino oscillations, for which Takaaki Kajita and Arthur B. McDonald were awarded the 2015 Nobel prize in physics, tremendous progresses have been made in measuring the mixing angles which determine the oscillation pattern. A lot of theoretical efforts have been made to understand how neutrinos mix with each other. Present data show that in the standard parameterization of the mixing matrix, ${\theta }_{23}$ is close to $\pi /4$ and the CP violating phase is close to $-\pi /2$. In this talk I report results obtained in arXiv:1505.01932 (Phys. Lett. B750(2015)620) and arXive:1404.01560 (Chin. J. Phys.53(2015)100101) and discuss some implications for theoretical model buildings for such mixing pattern. Specific examples for neutrino mixing based on $A_4$ family symmetry are given.

The upper ocean mixing in the Bay of Bengal (BoB) gets substantial influence from the local winds, huge fresh water influx and tidal forcing that makes the mixing more complex and dynamic. This study aims to understand the role of tidal forcing on upper ocean mixing in the BoB and how this mixing process changes in presence of river fresh water. Moreover, it is also seen that how this tidal forcing modulates the air-sea interactions in the region. The analysis includes three high resolution (1/12°) Regional Ocean Modelling System (ROMS) simulations, a control run, a tide run and a river-tide run. In the tide forcing simulations, the tidal components included are M2, S2, N2, K2, K1, O1, P1, Q1, Mf and Mm. Again, the river-tide simulation additionally has the discharge from the major rivers (Ganges, Brahmaputra, Irrawaddy, Godavari, Krishna, Mahanadi and Subarnarekha) in the region. The analyses show that the tidal buoyancy deepens the mixed layer increasing the integrated upper ocean temperature, while the surface temperature reduces. The upper ocean temperature profile further reduces in the tidal vertical mixing process in presence of river fresh water. The tidal mixing increases the surface salinity, whereas the addition of low saline river discharge largely reduces the surface and subsurface salinity. The warmer upper ocean layers in the tidal forcing simulation radiates more surface longwave, sensible and latent surface heat fluxes over the region. Therefore, the study shows that the tidal forcing has major influence in the upper ocean mixing as well as the air-sea fluxes over the BoB.