We investigate a scenario of cosmological inflation realized along a flat direction of the minimal seesaw model embedded in supergravity with a noncanonical $R$-parity violating Kähler potential. It is shown that with appropriate seesaw parameters the model is consistent with the present observation of the cosmological microwave background as well as with the neutrino oscillation data. It is also shown that the baryon asymmetry of the Universe can be generated through leptogenesis. The model favors supersymmetry breaking with the gravitino as the lightest superparticle, and thus indicates the gravitino dark matter scenario. An interesting feature of this model is that the seesaw parameters are constrained by the cosmological microwave background spectra. The $2\mathrm{\text{−}}\sigma$ constraints from the 9-year WMAP data yield a mild lower bound on the seesaw mass scale $\gtrsim \mathrm{TeV}$. We expect that the observation by the Planck satellite will soon provide more stringent constraints. The phenomenological and cosmological implications of the $R$-parity violation are also discussed.

In this paper we study the hard-thermal-loop effective theory at next-to-leading order. Standard power counting predicts that a large number of diagrams, including 2-loop diagrams, may need to be calculated. In all of the calculations that have been done however, with the exception of the photon self-energy, the full next-to-leading order contribution can be obtained by calculating only soft 1-loop diagrams with effective lines and vertices. It is of interest to know if the photon self-energy is the only exception to this rule, or if there are others, and which ones. In this paper we perform a refined power-counting analysis using real-time finite temperature field theory which is particularly well suited to the task. We show that the standard power-counting rules obtained from the imaginary time formalism usually overestimate the size of the 2-loop diagrams. We argue that the only exceptions to the rule that the 1-loop soft diagrams give the next-to-leading order contribution are $2n$-photon vertices.

We investigate the detailed structure of the solution space of the Bianchi type I spacetime with a massless scalar field in loop quantum cosmology (LQC). To analyze the dynamics we use the effective Hamiltonian written by new gauge-invariant variables which have a more direct physical interpretation. Since the effective equations of motion contain a nontrivial quantum correction, we may regard the universes as classical when the dynamics is well-described by the classical Friedmann equation. In addition to solutions which evolve into the classical universes, we find cyclic and stationary solutions which are dominated by the quantum effect for all time. We also show the asymmetric behavior and completely classify the Kasner transition across the bounce moment. We calculate the “probability” of having a classical isotropic universe by using the measure defined by the volume form in the solution space. Although we find that isotropic classical universes are disfavored in our model with a massless scalar field, we argue that LQC can explain the present isotropy if we consider a more realistic model.

We study how “warm” the Wino dark matter is when it is nonthermally produced by the decays of the gravitino in the early Universe. We clarify the energy distribution of the Wino at the decay of the gravitino and the energy loss process after their production. By solving the Boltzmann equation, we show that a sizable fraction of the Wino dark matter can be warm for the Wino mass $m_{\tilde{w}}\simeq 100–500\mathrm{GeV}$. The warmness of the Wino dark matter leaves imprints on the matter power spectra and may provide further insights on the origin of dark matter via the future 21 cm line survey. Our calculations can be applied to other nonthermal Wino production scenarios such as the Wino dark matter produced by the decay of the moduli fields.

Chiral symmetry breaking patterns are investigated in the $U_L(n)\times U_R(n)$ meson model. It is shown that new classes of minima of the effective potential belonging to the center of the Lie algebra exist for arbitrary flavor number $n$. The true ground state of the system is searched nonperturbatively and although multiple local minima of the effective potential may exist, it is argued that in regions of the parameter space applicable for the strong interaction, strictly a $U_L(n)\times U_R(n)\to U_V(n)$ spontaneous symmetry breaking is possible. The reason behind this is the existence of a discrete subset of axial symmetries, which connects various $U_V(n)$ symmetric vacua of the theory. The results are in agreement with the Vafa-Witten theorem of QCD, illustrating that it remains valid, even without gauge fields, for an effective model of the strong interaction.

We study lepton-number-violating (LNV) decays of heavy flavors ($\tau$ lepton and top quark) induced by a doubly-charged Higgs boson in the Higgs triplet model. It is found that the branching fractions of LNV ${\tau }^{-}\to {\ell }^{+}{M}_1^{-}{M}_2^{-}$ decays are highly suppressed compared with the current experimental limits. On the other hand, for LNV top-quark decays, the most optimistic branching ratios for $t\to b{\ell }^{+}{\ell }^{+}{W}^{-}$ turn out to be at the level of $\sim {10}^{-7}-{10}^{-8}$. The observation of these rare top-quark decays would be a clear signal of LNV processes, and their nonobservation would allow us to constrain the parameters of the Higgs triplet model.

We consider the quark sector of theories containing three scalar $SU(2{)}_L$ doublets in the triplet representation of $A_4$ (or $S_4$) and three generations of quarks in arbitrary $A_4$ (or $S_4$) representations. We show that for all possible choices of quark field representations and for all possible alignments of the Higgs vacuum expectation values that can constitute global minima of the scalar potential, it is not possible to obtain simultaneously nonvanishing quark masses and a nonvanishing $CP$-violating phase in the Cabibbo-Kobayashi-Maskawa quark mixing matrix. As a result, in this minimal form, models with three scalar fields in the triplet representation of $A_4$ or $S_4$ cannot be extended to the quark sector in a way consistent with experiment.

The analysis of the Higgs boson data by the ATLAS and CMS Collaborations appears to exhibit an excess of $h\to \gamma \gamma$ events above the Standard Model (SM) expectations, whereas no significant excess is observed in $h\to Z{Z}^{*}\to \mathrm{\text{four lepton}}$ events, albeit with large statistical uncertainty due to the small data sample. These results (assuming they persist with further data) could be explained by a pair of nearly mass-degenerate scalars, one of which is an SM-like Higgs boson and the other is a scalar with suppressed couplings to $W^{+}{W}^{-}$ and $ZZ$. In the two-Higgs-doublet model, the observed $\gamma \gamma$ and $Z{Z}^{*}\to \mathrm{\text{four lepton}}$ data can be reproduced by an approximately degenerate $CP$-even ($h$) and $CP$-odd ($A$) Higgs boson for values of $\sin (\beta -\alpha )$ near unity and $0.70\lesssim \tan \beta \lesssim 1$. An enhanced $\gamma \gamma$ signal can also arise in cases where $m_h\simeq m_H$, $m_H\simeq m_A$, or $m_h\simeq m_H\simeq m_A$. Since the $Z{Z}^{*}\to 4$ leptons signal derives primarily from an SM-like Higgs boson whereas the $\gamma \gamma$ signal receives contributions from two (or more) nearly mass-degenerate states, one would expect a slightly different invariant mass peak in the $Z{Z}^{*}\to \mathrm{\text{four lepton}}$ and $\gamma \gamma$ channels. The phenomenological consequences of such models can be tested with additional Higgs data that will be collected at the LHC in the near future.

We present a new QCD description of the ATLAS jet veto measurement, using the Banfi-Marchesini-Smye equation to constrain the interjet QCD radiation. This equation resums emissions of soft gluons at large angles, at leading-logarithmic accuracy, and accounts for both the so-called Sudakov and nonglobal logarithms. We show that this approach is able to reproduce, with no fitting parameters, the fraction of high-$p_T$ forward-backward dijet events which do not contain additional hard emissions in the interjet rapidity range. We also compute the gap fraction in fixed-order perturbation theory to $\mathcal{O}({\alpha }_s^2)$ and show that the perturbative series is unstable at large rapidity intervals.

We perform a general parton level analysis for the search of heavy resonant states in the production of $t\overline{t}$ pairs at the LHC with an integrated luminosity of $30{\mathrm{fb}}^{-1}$. We assume the existence of resonances that only couple to quarks and propose kinematic cuts in order to increase the number of events produced through quark annihilation. We study the interplay between different variables and their impact on the purity of the selected sample. We focus on the longitudinal ($\beta$) and transverse ($p_T$) momenta of the $t\overline{t}$ pair and the scattering angle ($\theta$) in the center of mass reference frame. We observe that $\beta$ is replaced by $\theta$ as a suitable discriminating variable of quark-annihilation processes for invariant masses above 1 TeV. Finally, we illustrate the analysis with a gluon resonance of 1.5 TeV and show the improvement in the sensitivity of the signal when cuts on $\theta$ are imposed.

In a recent article [K. Dusling and R. Venugopalan, arXiv:1210.3890 [Phys. Rev. D (to be published)]], we showed that high multiplicity dihadron proton-proton ($\mathrm{p}+\mathrm{p}$) data from the CMS experiment are in excellent agreement with computations in the color glass condensate effective field theory. This agreement of the theory with several hundred data points provides a nontrivial description of both nearside (“ridge”) and awayside azimuthal collimations of long range rapidity correlations in $\mathrm{p}+\mathrm{p}$ collisions. Our prediction in Dusling and Venugopalan [arXiv:1210.3890 [Phys. Rev. D (to be published)]] for proton-lead ($\mathrm{p}+\mathrm{Pb}$) collisions is consistent with results from the recent CMS $\mathrm{p}+\mathrm{Pb}$ run at ${\sqrt{s}}_{\mathrm{NN}}=5.02\mathrm{TeV}$ for the largest track multiplicity $N_{\mathrm{track}}\sim 40$ we considered. The CMS $\mathrm{p}+\mathrm{Pb}$ data shows the following striking features: (i) a strong dependence of the ridge yield on $N_{\mathrm{track}}$, with a significantly larger signal than in $\mathrm{p}+\mathrm{p}$ for the same $N_{\mathrm{track}}$, (ii) a stronger $p_T$ dependence than in $\mathrm{p}+\mathrm{p}$ for large $N_{\mathrm{track}}$, and (iii) a nearside collimation for large $N_{\mathrm{track}}$ comparable to the awayside for the lower $p_T=p_T^{\mathrm{trig}}=p_T^{\mathrm{assoc}}$ dihadron windows. We show here that these systematic features of the CMS $\mathrm{p}+\mathrm{Pb}$ di-hadron data are all described by the color glass condensate (with parameters fixed by the $\mathrm{p}+\mathrm{p}$ data) when we extend our prediction in Dusling and Venugopalan [arXiv:1210.3890 [Phys. Rev. D (to be published)]] to rarer high multiplicity events. We also predict the azimuthally collimated yield for yet unpublished windows in the $p_T^{\mathrm{trig}}$ and $p_T^{\mathrm{assoc}}$ matrix.

We derive holographic anti–de Sitter/quantum chromodynamics distribution amplitudes (DA) for the transversely polarized $\rho$ meson and we use them to predict the branching ratio for the decays ${\overline{B}}^{\circ }\to {\rho }^{\circ }\gamma$ and ${\overline{B}}_s^{\circ }\to {\rho }^{\circ }\gamma$ beyond leading power accuracy in the heavy quark limit. For ${\overline{B}}^{\circ }\to {\rho }^{\circ }\gamma$, our predictions agree with those generated using sum rules distribution amplitudes and with the data from the BABAR and Belle collaborations. In computing the weak annihilation amplitude which is power suppressed in ${\overline{B}}^{\circ }\to {\rho }^{\circ }\gamma$ but is the leading contribution in ${\overline{B}}_s^{\circ }\to {\rho }^{\circ }\gamma$, we find that, in its present form, the anti–de Sitter/quantum chromodynamics DA avoids the end-point divergences encountered with the sum rules DA.

The discovery of leptonic $CP$ violation is one of the primary goals of next-generation neutrino oscillation experiments, which is feasible due to the recent measurement of a relatively large leptonic mixing angle ${\theta }_{13}$. We suggest two new working observables $\Delta A_{\alpha \beta }^{\mathrm{m}}\equiv \max [A_{\alpha \beta }^{CP}(\delta )]-\min [A_{\alpha \beta }^{CP}(\delta )]$ and $\Delta A_{\alpha \beta }^{CP}(\delta )\equiv A_{\alpha \beta }^{CP}(\delta )-A_{\alpha \beta }^{CP}(0)$ to describe the $CP$-violating effects in long-baseline and atmospheric neutrino oscillation experiments. The former signifies the experimental sensitivity to the leptonic Dirac $CP$-violating phase $\delta$ and can be used to optimize the experimental setup, while the latter measures the intrinsic leptonic $CP$ violation and can be used to extract $\delta$ directly from the experimental observations. Both analytical and numerical analyses are carried out to illustrate their main features. It turns out that an intense neutrino beam with sub-GeV energies and a baseline of a few 100 km may serve as an optimal experimental setup for probing leptonic $CP$ violation.

In the context of discrete flavor symmetries, we elaborate a method that allows one to obtain relations between the mixing parameters in a model-independent way. Under very general conditions, we show that flavor groups of the von Dyck type, that are not necessarily finite, determine the absolute values of the entries of one column of the mixing matrix. We apply our formalism to finite subgroups of the infinite von Dyck groups, such as the modular groups, and find cases that yield an excellent agreement with the best fit values for the mixing angles. We explore the Klein group as the residual symmetry of the neutrino sector and explain the permutation property that appears between the elements of the mixing matrix in this case.

We study the possibility of the Higgs boson, which consists of an $SU(2)$ doublet and a septet. The vacuum expectation value of a septet with hypercharge $Y=2$ is known to preserve the electroweak rho parameter unity at the tree level. Therefore, the septet can give a significant contribution to the electroweak symmetry breaking. Because of the mixing with the septet, the gauge coupling of the standard-model-like Higgs boson is larger than that in the standard model. We show the sizable vacuum expectation value of the Higgs septet can be allowed under the constraint from the electroweak precision data. The signal strengths of the Higgs boson for the diphoton and a pair of weak gauge boson decay channels at the LHC are enhanced, while those for the fermionic decay modes are suppressed. The mass of additional neutral Higgs boson is also bounded by the current LHC data for the standard model Higgs boson. We discuss the phenomenology of the multiply charged Higgs bosons, which come from the septet.

A new particle with proprieties similar to those of the Higgs boson in the Standard Model has been recently discovered. The biggest discrepancy is related to its diphoton decay, whose branching ratio seems to be around two times larger with respect to the correspondent Standard Model value; this evidence, even if still affected by large uncertainties, suggests that clues of new physics related to the spontaneous breaking of the electroweak symmetry could be hidden under this loop-induced process. A new strongly coupled sector responsible for this breaking, for instance, could produce in analogy with QCD a charged massive spin-2 state. In light of these arguments we calculate and discuss the role of such a resonance in the diphoton decay width of the Higgs.

We investigate the presence of braneworld solutions in a bimetric theory, with gravity and the scalar field coupling differently. We consider a nonstandard model, with a Cuscuton-like scalar field, and we show how to generate braneworld solutions in this new scenario. In particular, we found no gravitational instabilities for the braneworld solutions.

Padmanabhan [arXiv:1206.4916] argues that the cosmic acceleration can be understood from the perspective that spacetime dynamics is an emergence phenomena. By calculating the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space, he also arrives at the Friedmann equation in a flat universe. In this paper, by modification of his proposal, we are able to derive the Friedmann equation of the Friedmann-Robertson-Walker universe with any spatial curvature. We also extend the study to higher-dimensional spacetime and derive successfully the Friedmann equations not only in Einstein gravity but also in Gauss-Bonnet and more general Lovelock gravity with any spatial curvature. This is the first derivation of Friedmann equations in these gravity theories in a nonflat Friedmann-Robertson-Walker universe by using the novel idea proposed by Padmanabhan. Our study indicates that the approach presented here is powerful enough and further supports the viability of Padmanabhan’s perspective of emergence gravity.

We discuss gauge coupling unification in models with additional one to four complete vectorlike families and derive simple rules for masses of vectorlike fermions required for exact gauge coupling unification. These mass rules and the classification scheme are generalized to an arbitrary extension of the standard model. We focus on scenarios with three or more vectorlike families in which the values of gauge couplings at the electroweak scale are highly insensitive to the grand unification scale, the unified gauge coupling, and the masses of vectorlike fermions. Their observed values can be mostly understood from infrared fixed-point behavior. With respect to sensitivity to fundamental parameters, the model with three extra vectorlike families stands out. It requires vectorlike fermions with masses of order 1–100 TeV, and thus at least part of the spectrum may be within the reach of the LHC. The constraints on proton lifetime can be easily satisfied in these models since the best motivated grand unification scale is at $\sim {10}^{16}\mathrm{GeV}$. The Higgs quartic coupling remains positive all the way to the grand unification scale, and thus the electroweak minimum of the Higgs potential is stable.

We develop a new method for tagging jets produced by hadronically decaying top quarks. The method is an application of shower deconstruction, a maximum information approach that was previously applied to identifying jets produced by Higgs bosons that decay to $\mathrm{b}\overline{\mathrm{b}}$. We tag an observed jet as a top jet based on a cut on a calculated variable $\chi$ that is an approximation to the ratio of the likelihood that a top jet would have the structure of the observed jet to the likelihood that a nontop QCD jet would have this structure. We find that the shower deconstruction based tagger can perform better in discriminating boosted top quark jets from QCD jets than other publicly available tagging algorithms.