Kaon semi-leptonic form factor at zero momentum transfer in finite volume

Using Chiral Perturbation Theory, we obtain the kaon semi-leptonic vector form factor in finite volume at a generic momentum transfer, $q^2$, up to one loop order. At first we confirm the lattice observation that the contribution of the heavy Pseudo-Goldstone boson in the finite volume corrections at zero momentum transfer is unimportant. We then evaluate the form factor at $q^2=0$ numerically and compare our results with the present lattice data. It turns out that our ChPT results are comparable with the lattice data to some extend. The formula for the finite volume corrections obtained for the form factor at momentum transfer $q^2$, provides a tool for lattice data in order to extrapolate at large lattice size.Comment: 19 pages, 3 figures: matches published version, comparisons made with more lattice dat

DAMPE Electron-Positron Excess in Leptophilic Z′Z' model

Recently the DArk Matter Particle Explorer (DAMPE) has reported an excess in the electron-positron flux of the cosmic rays which is interpreted as a dark matter particle with the mass about $1.5$ TeV. We come up with a leptophilic $Z'$ scenario including a Dirac fermion dark matter candidate which beside explaining the observed DAMPE excess, is able to pass various experimental/observational constraints including the relic density value from the WMAP/Planck, the invisible Higgs decay bound at the LHC, the LEP bounds in electron-positron scattering, the muon anomalous magnetic moment constraint, Fermi-LAT data, and finally the direct detection experiment limits from the XENON1t/LUX. By computing the electron-positron flux produced from a dark matter with the mass about $1.5$ TeV we show that the model predicts the peak observed by the DAMPE.Comment: 18 pages, 7 figures, matches with the published versio

Electroweak Baryogenesis and Dark Matter via a Pseudoscalar vs. Scalar

We study the electroweak baryogenesis in a fermionic dark matter scenario with a (pseudo)scalar being the mediator in the Higgs portal. It is discussed that the electroweak phase transition turns to be first-order after taking into account the role of the (pseudo)scalar in the thermal effective potential in our extended standard model. Imposing the relic density constraint from the WMAP/Planck and the bounds from the direct detection experiments XENON100/LUX, we show that the dark matter scenario with a scalar mediator is hardly capable of explaining the baryogenesis while the same model with a pseudoscalar mediator is able to explain the baryon asymmetry. For the latter, we constrain more the model with {\it Fermi}-LAT upper limit on dark matter annihilation into $b\bar b$ and $\tau^+\tau^-$. The allowed dark matter mass that leads to correct relic abundance, renders the electroweak phase transition strongly first-order, and respects the {\it Fermi}-LAT limit, will be in the range $110-320$ GeV. The exotic and invisible Higgs decay bounds and the mono-jet search limit at the LHC do not affect the viable space of parameters.Comment: 15 pages, 4 figures. Fermi-LAT constraint on DM DM to b\bar, tau^+ tau^- in the model was imposed. The range of the mediator mass was shown in a figure. Published in JHE