Can the 750-GeV diphoton resonance be the singlet Higgs boson of custodial Higgs triplet model?

The observation of diphoton excess around the mass of 750 GeV in LHC Run-II motivates us to consider whether the singlet Higgs boson in the custodial Higgs triplet model can serve as a good candidate because an earlier study of comprehensive parameter scan shows that it can have the right mass in the viable mass spectra. By assuming the singlet Higgs mass at 750 GeV, its total width less than 50 GeV and imposing constraints from the LHC 8-TeV data, we identify an approximately linear region on the $(v_\Delta, \alpha)$ plane along which the exotic Higgs boson masses satisfy a specific hierarchy and have lower possible spectra, where $v_\Delta$ denotes the triplet vacuum expectation value and $\alpha$ is the mixing angle between the singlet Higgs boson and the standard model-like Higgs boson. Although the diphoton decay rate can be enhanced by charged Higgs bosons running in the loop in this region, it is mostly orders of magnitude smaller than that required for the observed production rate, except for the small $v_\Delta$ region when the diphoton fusion production mechanism becomes dominant. Nonetheless, this part of parameter space suffers from the problems of breakdown of perturbativity and large uncertainties in the photon parton distribution function of proton.Comment: 14 pages, 2 figures, and 2 tables; bugs in numerical calculations fixed, and discussions and conclusions changed; typo corrected; 16 pages, expanded with more detailed discussions, updated figures and tables, version to appear in the journa

Genes Translocated into the Plastid Inverted Repeat Show Decelerated Substitution Rates and Elevated GC Content.

Plant chloroplast genomes (plastomes) are characterized by an inverted repeat (IR) region and two larger single copy (SC) regions. Patterns of molecular evolution in the IR and SC regions differ, most notably by a reduced rate of nucleotide substitution in the IR compared to the SC region. In addition, the organization and structure of plastomes is fluid, and rearrangements through time have repeatedly shuffled genes into and out of the IR, providing recurrent natural experiments on how chloroplast genome structure can impact rates and patterns of molecular evolution. Here we examine four loci (psbA, ycf2, rps7, and rps12 exon 2-3) that were translocated from the SC into the IR during fern evolution. We use a model-based method, within a phylogenetic context, to test for substitution rate shifts. All four loci show a significant, 2- to 3-fold deceleration in their substitution rate following translocation into the IR, a phenomenon not observed in any other, nontranslocated plastid genes. Also, we show that after translocation, the GC content of the third codon position and of the noncoding regions is significantly increased, implying that gene conversion within the IR is GC-biased. Taken together, our results suggest that the IR region not only reduces substitution rates, but also impacts nucleotide composition. This finding highlights a potential vulnerability of correlating substitution rate heterogeneity with organismal life history traits without knowledge of the underlying genome structure

Radiative corrections to Higgs couplings with weak gauge bosons in custodial multi-Higgs models

We calculate 1-loop radiative corrections to the $hZZ$ and $hWW$ couplings in models with next--to--simplest Higgs sectors satisfying the electroweak $\rho$ parameter equal to 1 at tree level: the Higgs singlet model, the two-Higgs doublet models, and the Georgi-Machacek model. Under theoretical and current experimental constraints, the three models have different correlations between the deviations in the $hZZ$ and $hWW$ couplings from the standard model predictions. In particular, we find for each model predictions with no overlap with the other two models.Comment: 5 pages, 1 figur

The Relationship Between Latent Heating, Vertical Velocity, and Precipitation Processes: the Impact of Aerosols on Precipitation in Organized Deep Convective Systems

A high-resolution, two-dimensional cloud-resolving model with spectral-bin microphysics is used to study the impact of aerosols on precipitation processes in both a tropical oceanic and a midlatitude continental squall line with regard to three processes: latent heating (LH), cold pool dynamics, and ice microphysics. Evaporative cooling in the lower troposphere is found to enhance rainfall in low cloud condensation nuclei (CCN) concentration scenarios in the developing stages of a midlatitude convective precipitation system. In contrast, the tropical case produced more rainfall under high CCN concentrations. Both cold pools and low-level convergence are stronger for those configurations having enhanced rainfall. Nevertheless, latent heat release is stronger (especially after initial precipitation) in the scenarios having more rainfall in both the tropical and midlatitude environment. Sensitivity tests are performed to examine the impact of ice and evaporative cooling on the relationship between aerosols, LH, and precipitation processes. The results show that evaporative cooling is important for cold pool strength and rain enhancement in both cases. However, ice microphysics play a larger role in the midlatitude case compared to the tropics. Detailed analysis of the vertical velocity-governing equation shows that temperature buoyancy can enhance updraftsdowndrafts in the middlelower troposphere in the convective core region; however, the vertical pressure gradient force (PGF) is of the same order and acts in the opposite direction. Water loading is small but of the same order as the net PGF-temperature buoyancy forcing. The balance among these terms determines the intensity of convection