Empirical determination of charm quark energy loss and its consequences for azimuthal anisotropy

We propose an empirical model to determine the form of energy loss of charm quarks due to multiple scatterings in quark gluon plasma by demanding a good description of production of D mesons and non-photonic electrons in relativistic collision of heavy nuclei at RHIC and LHC energies. Best results are obtained when we approximate the momentum loss per collision $\Delta p_T \propto \alpha \, p_T$, where $\alpha$ is a constant depending on the centrality and the centre of mass energy. Comparing our results with those obtained earlier for drag coefficients estimated using Langevin equation for heavy quarks we find that up to half of the energy loss of charm quarks at top RHIC energy could be due to collisions while that at LHC energy at 2760 GeV/A the collisional energy loss could be about one third of the total. Estimates are obtained for azimuthal anisotropy in momentum spectra of heavy mesons, due to this energy loss. We further suggest that energy loss of charm quarks may lead to an enhanced production of D-mesons and single electrons at low $p_T$ in AA collisions.Comment: 11 pages, 3 figures, Typographical errors corrected, Key-words and PACS indices added, sequence of figures corrected, references added in section 3, discussions expande

Explicitly broken lepton number at low energy in the Higgs triplet model

We suppose that lepton number is explicitly broken at low energy scale(M) in the framework of the Higgs triplet($\Delta$) model. The scalar sector of the model is developed considering the particular assumption $M=v_\Delta \approx$ eV. We show that such assumption infers a particular mass spectrum for the scalars that compose the triplet and cause a decoupling of these scalars from those that compose the standard scalar doublet.Comment: Minor changes, New references added, To appear at MPL

Lifetime determination of the 5d2^{2}~3^{3}F2_{2} state in barium using trapped atoms

Magneto-optically trapped atoms enable the determination of lifetimes of metastable states and higher lying excited states like the $\rm{5d^{2}~^{3}F_{2}}$ state in barium. The state is efficiently populated by driving strong transitions from metastable states within the cooling cycle of the barium MOT. The lifetime is inferred from the increase of MOT fluorescence after the transfer of up to $30\,\%$ of the trapped atoms to this state. The radiative decay of the $\rm{5d^{2}~^{3}F_{2}}$ state cascades to the cooling cycle of the MOT with a probability of $96.0(7)\,\%$ corresponding to a trap loss of $4.0(7)\,\%$ and its lifetime is determined to $\rm{160(10)~\mu s}$. This is in good agreement with the theoretically calculated lifetime of $\rm{190~\mu s}$ [J. Phys. B, {\bf 40}, 227 (2007)]. The determined loss of $4.0(7)\,\%$ from the cooling cycle is compared with the theoretically calculated branching ratios. This measurement extends the efficacy of trapped atoms to measure lifetimes of higher, long-lived states and validate the atomic structure calculations of heavy multi-electron systems.Comment: 5 pages, accepted for publication in Physical Review

The Finslerian quantum cosmology

We present a Friedmann-Robertson-Walker (FRW) quantum cosmological model within the framework of Finslerian geometry. In this work, we consider a specific fluid. We obtain the corresponding Wheeler-DeWitt equation as the usual constraint equation as well as Schr\"odinger equation following Dirac, although the approaches yields the same equation of time independent equation for the wave function of the universe. We provide exact classical and quantum mechanical solutions. We use the eigenfunctions to study the time evolution of the expectation value of the scale factor. Finally we discuss the physical meaning of the results.Comment: To appear in Can.J.Phy