Unified TeV Scale Picture of Baryogenesis and Dark Matter

We present a simple extension of MSSM which provides a unified picture of cosmological baryon asymmetry and dark matter. Our model introduces a gauge singlet field $N$ and a color triplet field $X$ which couple to the right--handed quark fields. The out--of equilibrium decay of the Majorana fermion $N$ mediated by the exchange of the scalar field $X$ generates adequate baryon asymmetry for $M_N \sim 100$ GeV and $M_X \sim$ TeV. The scalar partner of $N$ (denoted $\tilde{N}_1$) is naturally the lightest SUSY particle as it has no gauge interactions and plays the role of dark matter. $\tilde{N}_1$ annihilates into quarks efficiently in the early universe via the exchange of the fermionic $\tilde{X}$ field. The model is experimentally testable in (i) neutron--antineutron oscillations with a transition time estimated to be around $10^{10}$ sec, (ii) discovery of colored particles $X$ at LHC with mass of order TeV, and (iii) direct dark matter detection with a predicted cross section in the observable range.Comment: 10 pages, one reference updated. Version to appear in Phys. Rev. Let

New vector-scalar contributions to neutrinoless double beta decay and constraints on R-parity violation

We show that in minimal supersymmetric standard model (MSSM) with R-parity breaking as well as in the left-right symmetric model, there are new observable contributions to neutrinoless double beta decay arising from hitherto overlooked diagrams involving the exchange of one W boson and one scalar boson. In particular, in the case of MSSM, the present experimental bounds on neutrinoless double beta decay lifetime improves the limits on certain R-parity violating couplings by about two orders of magnitude. It is shown that similar diagrams also lead to enhanced rates for $\mu^-\rightarrow e^+$ conversion in nuclei, which are in the range accessible to ongoing experiments.Comment: Latex file; 9 pages; 3 figures available on reques

A Theory of R(D∗,D)R(D^*,D) Anomaly With Right-Handed Currents

We present an ultraviolet complete theory for the $R(D^*)$ and $R(D)$ anomaly in terms of a low mass $W_R^\pm$ gauge boson of a class of left-right symmetric models. These models, which are based on the gauge symmetry $SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$, utilize vector-like fermions to generate quark and lepton masses via a universal seesaw mechanism. A parity symmetric version as well as an asymmetric version are studied. A light sterile neutrino emerges naturally in this setup, which allows for new decay modes of $B$-meson via right-handed currents. We show that these models can explain $R(D^*)$ and $R(D)$ anomaly while being consistent with LHC and LEP data as well as low energy flavor constraints arising from $K_L-K_S, B_{d,s}-\bar{B}_{d,s}$, $D-\bar{D}$ mixing, etc., but only for a limited range of the $W_R$ mass: $1.2\, (1.8)~{\rm TeV} \leq M_{W_R}\leq 3~ {\rm TeV}$ for parity asymmetric (symmetric) Yukawa sectors. The light sterile neutrinos predicted by the model may be relevant for explaining the MiniBoone and LSND neutrino oscillation results. The parity symmetric version of the model provides a simple solution to the strong CP problem without relying on the axion. It also predicts an isospin singlet top partner with a mass $M_T = (1.5-2.5)$ TeV.Comment: 43 pages, 7 figures, references added, model slightly modifie