Lepton Masses in a Minimal Model with Triplet Higgs Bosons and S3S_3 Flavor Symmetry

Viable neutrino and charged lepton masses and mixings are obtained by imposing a $S_3 \times Z_4 \times Z_3$ flavor symmetry in a model with a few additional Higgs. We use two $SU(2)_L$ triplet Higgs which are arranged as a doublet of $S_3$, and standard model singlet Higgs which are also put as doublets of $S_3$. We break the $S_3$ symmetry in this minimal model by giving vacuum expectation values (VEV) to the additional Higgs fields. Dictated by the minimum condition for the scalar potential, we obtain certain VEV alignments which allow us to maintain $\mu-\tau$ symmetry in the neutrino sector, while breaking it maximally for the charged leptons. This helps us to simultaneously explain the hierarchical charged lepton masses, and the neutrino masses and mixings. In particular, we obtain maximal $\theta_{23}$ and zero $\theta_{13}$. We allow for a mild breaking of the $\mu-\tau$ symmetry for the neutrinos and study the phenomenology. We give predictions for $\theta_{13}$ and the CP violating Jarlskog invariant $J_{CP}$, as a function of the $\mu-\tau$ symmetry breaking parameter. We also discuss possible collider signatures and phenomenology associated with lepton flavor violating processes.Comment: 29 pages, 5 figures. Version to be appeared in PRD. Phenomenology of Lepton flavor violation and possible collider signatures of this model have been include

Effect of Atomic Coherence on Absorption in Four-level Systems: an Analytical study

Absorption profile of a four-level ladder atomic system interacting with three driving fields is studied perturbatively and analytical results are presented. Numerical results where the driving field strengths are treated upto all orders are presented. The absorption features is studied in two regimes, i) the weak middle transition coupling, i.e. $\Omega_2 << \Omega_{1,3}$ and ii) the strong middle transition coupling $\Omega_2 >>\Omega_{1,3}$. In case i), it is shown that the ground state absorption and the saturation characteristics of the population of level 2 reveal deviation due to the presence of upper level couplings. In particular, the saturation curve for the population of level 2 shows a dip for $\Omega_1 = \Omega_3$. While the populations of levels 3 and 4 show a maxima when this resonance condition is satisfied. Thus the resonance condition provides a criterion for maximally populating the upper levels. A second order perturbation calculation reveals the nature of this minima (maxima). In the second case, I report two important features: a) Filtering of the Aulter-Townes doublet in the three-peak absorption profile of the ground state, which is achieved by detuning only the upper most coupling field, and b) control of line-width by controlling the strength of the upper coupling fields. This filtering technique coupled with the control of linewidth could prove to be very useful for high resolution studies.Comment: 15 pages 12 figure

Bacteriophages as a model for studying carbon regulation in aquatic system

The interconversion of carbon in organic, inorganic and refractory carbon is still beyond the grasp of present environmentalists. The bacteria and their phages, being the most abundant constituents of the aquatic environment, represent an ideal model for studing carbon regulation in the aquatic system. The refractory dissolved organic carbon (DOC), a recently coined terminology from the microbe-driven conversion of bioavailable organic carbon into difficult-to-digest refractory DOC by microbial carbon pump (MCP), is suggested to have the potential to revolutionize our view of carbon sequestration. It is estimated that about 95% of organic carbon is in the form of refractory DOC, which is the largest pool of organic matter in the ocean. The refractory DOC is supposed to be the major factor in the global carbon cycle whose source is not yet well understood. A key element of the carbon cycle is the microbial conversion of dissolved organic carbon into inedible forms. The time studies of phage-host interaction under control conditions reveal their impact on the total carbon content of the source and their interconversion among organic, inorganic and other forms of carbon with respect to control source. The TOC- analysis statistics stipulate an increase in inorganic carbon content by 15-25 percent in the sample with phage as compared to the sample without phage. The results signify a 60-70 fold increase in inorganic carbon content in sample with phage, whereas, 50-55 fold in the case of sample without phages as compared with control. This increase in inorganic carbon content may be due to lysis of the host cell releasing its cellular constituents and utilization of carbon constituent for phage assembly and development. It also proves the role of phages in regulating the carbon flow in aquatic systems like oceans, where their concentration outnumbered other species