In a class of new physics models, an extended Higgs sector and new $CP$-violating sources are simultaneously present in order to explain the baryon asymmetry in the Universe. The aim of this work is to study the implications of beyond the Standard Model (SM) $CP$ violation for the searches of heavy scalars at the LHC. In particular, we focus on the diphoton channel searches in the $CP$-violating two-Higgs-doublet model (CPV 2HDM). To have a sizable CPV in the scalar sector, the two heavy neutral scalars in 2HDM tend to be nearly degenerate. The theoretical constraints of unitarity, perturbativity and vacuum stability are considered, which requires that the heavy scalars $M_H\lesssim 1\mathrm{TeV}$ in a large region of the parameter space. The experimental limits are also taken into account, including the direct searches for heavy neutral scalars in the final state of the SM $h$, $W$ and $Z$ bosons; the differential $t\overline{t}$ data; those from the charged scalar sector which is implied by the oblique $T$ parameter; and the precise measurements of the electric dipole moments of electrons and mercury. The quantum interference effects between the resonances and the SM background are crucially important for the diphoton signals, and the CPV mixing of the quasidegenerate heavy scalars could enhance significantly the resonance peak. With an integrated luminosity of $3000{\mathrm{fb}}^{-1}$ at the LHC, almost the whole parameter space of CPV 2HDM could be probed in the diphoton channel, and the CPV could also be directly detected via the diphoton spectrum.

Light neutral mediators, with mass $\lesssim 1\mathrm{GeV}$, are common features of extensions to the Standard Model. Current astrophysical and terrestrial experiments have constrained the model parameter space, and planned experiments around the world promise continued improvement in sensitivity. In this paper we study the prospects for probing light neutral mediators using terrestrial stopped pion and reactor sources in combination with ultralow threshold nuclear and electron recoil detectors. We show that the coherent neutrino-nucleus and neutrino-electron scattering channels provide complementary sensitivity to light mediators. With low-threshold detectors, we show that most stringent bounds on models arise from the nuclear scattering process, improving upon previous bounds from electron scattering of solar neutrinos by nearly an order of magnitude for mediator masses $\gtrsim 0.1\mathrm{GeV}$.

We study UV complete theories where the standard model (SM) gauge group is extended with a new Abelian $U(1{)}^{\prime }$, and the field content is augmented by an arbitrary number of scalar and fermion SM singlets, potentially including dark matter (DM) candidates. Considerations such as classical and quantum gauge invariance of the full theory and S-matrix unitarity, not applicable within a simplified model approach, are shown to have significant phenomenological consequences. The lack of gauge anomalies leads to compact relations among the $U(1{)}^{\prime }$ fermion charges and puts a lower bound on the number of dark fermions. Contrary to naive expectations, the DM annihilation to $Zh$ is found to be p-wave suppressed, as hinted by the perturbative unitarity of the S-matrix, with dramatic implications for DM thermal relic density and indirect searches. Within this framework, the interplay between dark matter, new vector boson, and Higgs physics is rather natural and generic.

Recently, Nishiura and the author proposed a unified quark-lepton mass matrix model under a family symmetry $\mathrm{U}(3)\times \mathrm{U}(3{)}^{\prime }$. The model can give excellent parameter fitting to the observed quark and neutrino data. The model has a reasonable basis as far as the quark sector, but, in the neutrino sector, the form of the right-handed neutrino mass matrix $M_R$ does not have a theoretical basis; that is, it was nothing but a phenomenological assumption. In this paper, it is pointed out that the form of $M_R$ is originated in the structure of Majorana mass matrix ($4\times 4$ matrix) for the left-handed fields $(({\nu }_L{)}_i,({\nu }_R^c{)}^i,(N_L{)}_{\alpha },(N_R^c{)}^{\alpha })$ where ${\nu }_i$ ($i=1$, 2, 3) and $N_{\alpha }$ ($\alpha =1$, 2, 3) are U(3)-family and ${\mathrm{U}(3)}^{\prime }$-family triplets, respectively.

We study theoretically the $BD\overline{D}$ and $BDD$ systems to see if they allow for possible bound or resonant states. The three-body interaction is evaluated implementing the fixed center approximation to the Faddeev equations which considers the interaction of a $D$ or $\overline{D}$ particle with the components of a $BD$ cluster, previously proved to form a bound state. We find an $I(J^P)=1/2(0^{-})$ bound state for the $BD\overline{D}$ system at an energy around 8925–8985 MeV within uncertainties, which would correspond to a bottom hidden-charm meson. In contrast, for the $BDD$ system, which would be bottom double-charm and hence manifestly exotic, we have found hints of a bound state in the energy region 8935–8985 MeV, but the results are not stable under the uncertainties of the model, and we cannot assure, nor rule out, the possibility of a $BDD$ three-body state.

We present the first fully differential next-to-leading order QCD calculation for lepton production in transversely polarized hadronic collisions, $p\uparrow p\uparrow \to {\ell }^{\pm }X$, where the lepton arises from the decay of an electroweak gauge boson. The calculation is implemented in the Monte-Carlo like code che that already includes the unpolarized and longitudinally polarized cross sections and may be readily used to perform a comparison to experimental data and to extract information on the related parton distributions. We analyze the perturbative stability of the cross-section and double spin asymmetry $A_{TT}$ at RHIC kinematics. We find that the QCD corrections are non-negligible even at the level of asymmetries and that they strongly depend on the lepton kinematics. Furthermore, we present two scenarios for transversely polarized parton distributions, based on the de Florian-Sassot-Stratmann-Vogelsang (DSSV) set of longitudinally parton densities and fully evolved to NLO accuracy, that can be used for the evaluation of different observables involving transverse polarization.

We have systematically studied the strong and radiative decays of the low-lying $1P$-wave doubly charmed baryons. Some interesting observations are: (i) The states ${\mathrm{\Xi }}_{cc}^{*}$ and ${\mathrm{\Omega }}_{cc}^{*}$ with $J^P=3/2^{+}$ have a fairly large decay rate into the ${\mathrm{\Xi }}_{cc}\gamma$ and ${\mathrm{\Omega }}_{cc}\gamma$ channels with a width $\sim 15$ and $\sim 7\mathrm{keV}$, respectively. (ii) The lowest lying excited doubly charmed baryons are dominated by the $1P$ $\rho$ mode excitations, which should be quite narrow states. They decay into the ground state with $J^P=1/2^{+}$ through the radiative transitions with a significant ratio. (iii) The total decay widths of the first orbital excitations of $\lambda$ mode ($1P_{\lambda }$ states with $J^P=1/2^{-}$, $3/2^{-}$, $5/2^{-}$) are about $\mathrm{\Gamma }\sim 100\mathrm{MeV}$, and the ratio between the radiative and hadronic decay widths is about $\mathcal{O}({10}^{-3})$.

Earlier estimates have argued that the baryon number violating scattering cross section in the laboratory is exponentially small so it will never be observed, even for incoming 2-particle energy well above the sphaleron energy of 9 TeV. However, we argue in Ref. [1] that, due to the periodic nature of the sphaleron potential, the event rate for energies above the sphaleron energy may be high enough to be observed in the near future. That is, there is a discrepancy of about 70 orders of magnitude between the two estimates. Here we argue why and how the multisphaleron processes are crucial to the event rate estimate, a very important “resonant tunneling” property that has not been taken into account before. We also summarize the input assumptions and arguments adopted in our estimate when compared to the earlier estimates.

Using a data set with an integrated luminosity of $2.93{\mathrm{fb}}^{-1}$ collected at $\sqrt{s}=3.773\mathrm{GeV}$ with the BESIII detector operating at the BEPCII storage rings, we search for the rare decay $D^{+}\to D^0{e}^{+}{\nu }_e$. No signal events are observed. We set the upper limit on the branching fraction for $D^{+}\to D^0{e}^{+}{\nu }_e$ to be $1.0\times 10^{-4}$ at the 90% confidence level.

Recently several papers extracted $|V_{cb}|$ using the Belle measurement [A. Abdesselam et al. (Belle Collaboration), arXiv:1702.01521.] of the exclusive $\overline{B}\to D^{*}\ell \overline{\nu }$ unfolded differential decay rates, available for the first time. Depending on the theoretical inputs, some of the fits yield higher $|V_{cb}|$ values, compatible with those from inclusive semileptonic $B$ decays. Since these four fits use mostly the same data, if their correlations were close to 100%, the tension between them would be over $5\sigma$. We determine the correlations, find that the tension between the results is less than $3\sigma$, and explore what might lead to improving the consistency of the fits. We find that fits that yield the higher values of $|V_{cb}|$, also suggest large violations of heavy quark symmetry. These fits are also in tension with preliminary lattice QCD data on the form factors. Without additional experimental data or lattice QCD input, there are no set of assumptions under which the tension between exclusive and inclusive determinations of $|V_{cb}|$ can be considered resolved.

The theory of quantum fields propagating on an isotropic cosmological quantum spacetime is reexamined by generalizing the scalar test field to an electromagnetic (EM) vector field. For any given polarization of the EM field on the classical background, the Hamiltonian can be written in the form of the Hamiltonian of a set of decoupled harmonic oscillators, each corresponding to a single mode of the field. In transition from the classical to quantum spacetime background, following the technical procedure given by Ashtekar et al. [Phys. Rev. D 79, 064030 (2009)], a quantum theory of the test EM field on an effective (dressed) spacetime emerges. The nature of this emerging dressed geometry is independent of the chosen polarization, but it may depend on the energy of the corresponding field mode. Specifically, when the backreaction of the field on the quantum geometry is negligible (i.e., a test field approximation is assumed), all field modes probe the same effective background independent of the mode’s energy. However, when the backreaction of the field modes on the quantum geometry is significant, by employing a Born-Oppenheimer approximation, it is shown that a rainbow (i.e., a mode-dependent) metric emerges. The emergence of this mode-dependent background in the Planck regime may have a significant effect on the creation of quantum particles. The production amount on the dressed background is computed and is compared with the familiar results on the classical geometry.

We present the first exact calculations of the time dependence of causal correlations in driven nonequilibrium states in ($2+1$)-dimensional systems using holography. Comparing exact results with those obtained from simple prototype geometries that are parametrized only by a time-dependent temperature, we find that the universal slowly varying features are controlled just by the pump duration and the initial and final temperatures only. We provide numerical evidence that the locations of the event and apparent horizons in the dual geometries can be deduced from the nonequilibrium causal correlations without any prior knowledge of the dual gravity theory.

Using the superfield formalism, we propose a nonlocal extension of the supersymmetric gauge theory coupled to massless chiral matter. Two different nonlocal models are considered. For these models, we explicitly calculate the one-loop Kähler effective potential.

We investigated the regular multihorizon black holes in the Einstein gravity, $F(R)$ gravity, and the 5 dimensional Gauss-Bonnet gravity, all of them coupled with nonlinear electrodynamics. We presented several explicit examples of the actions which admit the solutions describing regular black hole space-time with multihorizons. Thermodynamics of the obtained black hole solutions is studied. The explicit expressions of the temperature, the entropy, the thermodynamical energy and the free energy are obtained. Although the temperature vanishes in the extremal limit where the radii of the two horizons coincide with each other as in the standard multihorizon black hole like the Reissner-Nordström black hole or the Kerr black hole, the larger temperature corresponds to the larger horizon radius. This is different from the standard black holes, where the larger temperature corresponds to the smaller horizon radius. We also found that the specific heat becomes positive for the large temperature, which is also different from the standard black holes, where the specific heat is negative. It should be also noted that the thermodynamical energy is not identical with the ADM mass. Furthermore in case of the Gauss-Bonnet gravity,it is demonstrated that the entropy can become negative.

The cosmological black holes are black holes living not in an asymptotically flat universe but in an expanding spacetime. They have a rich dynamics especially for their mass and horizon. In this article, we perform a natural step in investigating this new type of black hole: we consider the possibility of a charged cosmological black hole. We derive the general equations of motion governing its dynamics and report a new analytic solution for the special case of the charged Lematre-Tolman-Bondi equations of motion that describe a charged cosmological black hole. We then study various relevant quantities for the characterization of the black hole, such as the C-function, the effect of the charge on the black hole flux, and the nature of the singularity. We also perform numerical investigations to strengthen our results. Finally, we challenge a model of gamma ray burst within our framework.

The next generation of cosmological surveys will operate over unprecedented scales, and will therefore provide exciting new opportunities for testing general relativity. The standard method for modelling the structures that these surveys will observe is to use cosmological perturbation theory for linear structures on horizon-sized scales, and Newtonian gravity for nonlinear structures on much smaller scales. We propose a two-parameter formalism that generalizes this approach, thereby allowing interactions between large and small scales to be studied in a self-consistent and well-defined way. This uses both post-Newtonian gravity and cosmological perturbation theory, and can be used to model realistic cosmological scenarios including matter, radiation and a cosmological constant. We find that the resulting field equations can be written as a hierarchical set of perturbation equations. At leading-order, these equations allow us to recover a standard set of Friedmann equations, as well as a Newton-Poisson equation for the inhomogeneous part of the Newtonian energy density in an expanding background. For the perturbations in the large-scale cosmology, however, we find that the field equations are sourced by both nonlinear and mode-mixing terms, due to the existence of small-scale structures. These extra terms should be expected to give rise to new gravitational effects, through the mixing of gravitational modes on small and large scales—effects that are beyond the scope of standard linear cosmological perturbation theory. We expect our formalism to be useful for accurately modeling gravitational physics in universes that contain nonlinear structures, and for investigating the effects of nonlinear gravity in the era of ultra-large-scale surveys.

Recent data released by the Alpha Magnetic Spectrometer (AMS) experiment on the primary spectra and secondary-to-primary ratios in cosmic rays (CRs) can pose tight constraints to astrophysical models of CR acceleration and transport in the Galaxy, thereby providing a robust baseline of the astrophysical background for a dark matter search via antimatter. However, models of CR propagation are affected by other important sources of uncertainties, notably from solar modulation and nuclear fragmentation, that cannot be improved with the sole use of the AMS data. The present work is aimed at assessing these uncertainties and their relevance in the interpretation of the new AMS data on the boron-to-carbon ($\mathrm{B}/\mathrm{C}$) ratio. Uncertainties from solar modulation are estimated using improved models of CR transport in the heliosphere constrained against various types of measurements: monthly resolved CR data collected by balloon-born or space missions, interstellar flux data from the Voyager-1 spacecraft, and counting rates from ground-based neutron monitor detectors. Uncertainties from nuclear fragmentation are estimated using semiempirical cross-section formulas constrained by measurements on isotopically resolved and charge-changing reactions. We found that a proper data-driven treatment of solar modulation can guarantee the desired level of precision, in comparison with the improved accuracy of the recent data on the $\mathrm{B}/\mathrm{C}$ ratio. On the other hand, nuclear uncertainties represent a serious limiting factor over a wide energy range. We therefore stress the need for establishing a dedicated program of cross-section measurements at the $\mathcal{O}(100\mathrm{GeV})$ energy scale.

Perturbation theory of thermodynamic potentials in QCD at $T>T_c$ is considered with the nonperturbative background vacuum taken into account. It is shown that the colormagnetic confinement in the QCD vacuum prevents the infrared catastrophe of the perturbation theory present in the case of the free vacuum (the “Linde problem”). A short discussion is given of the applicability of the nonperturbative formalism at large $T$ and of the relation with hard-thermal-loop theory. The observation of Linde, that the terms $O(g^n),n>6$ contribute to the order $O(g^6)$, is confirmed also with the account of the colormagnetic confinement, and it is shown that the latter ensures that these terms are IR convergent. To make these terms summable, an integral equation is formulated for the ladder graphs, which allows us to define the sum of the $O(g^6)$ terms via a nonsingular kernel. It is argued that the purely nonperturbative term without gluon exchanges may dominate for $T<600\mathrm{Mev}$.

We study the generation of small neutrino masses from the dimension six effective operator at tree level and one-loop level, the neutrinos are assumed to be Dirac particles. We find out all possible tree and one-loop diagrams which lead to finite neutrino masses. The relevant mediator fields and the predictions for neutrino masses are presented. The lower order contributions to neutrino masses can be forbidden by introducing soft breaking Abelian symmetry or finite non-Abelian symmetry. The messengers inside the loop can be dark matter particles. The possible dark matter candidates and the corresponding constraints on the parameter $\alpha$ are analyzed for each model.

The generalized thimble method to treat field theories with sign problems requires repeatedly solving the computationally expensive holomorphic flow equations. We present a machine learning technique to bypass this problem. The central idea is to obtain a few field configurations via the flow equations to train a feed-forward neural network. The trained network defines a new manifold of integration which reduces the sign problem and can be rapidly sampled. We present results for the $1+1$ dimensional Thirring model with Wilson fermions on sizable lattices. In addition to the gain in speed, the parametrization of the integration manifold we use avoids the “trapping” of Monte Carlo chains which plagues large-flow calculations, a considerable shortcoming of the previous attempts.