There exist several recent studies of the top-quark chromoelectric dipole moment (CEDM) in the context of searching for charge parity violating signals in top-quark pair production at the LHC. Most of these studies constrain the CEDM either from deviations in the top-pair cross section from its standard model value, or from T-odd asymmetries in the dimuon channel. Motivated by ATLAS and CMS interest, we extend the study of T-odd asymmetries to the lepton plus jets channel. At the parton level, using madgraph5, we identify the most promising signals and their statistical sensitivity. We find that the signals with larger sensitivity to the CEDM require distinguishing between $b$ and $\overline{b}$ jets and propose a simple way to address this.

We propose a scheme, based on $\mathrm{\Delta }(27)$ flavor symmetry and supplemented by other discrete symmetries and the inverse seesaw mechanism, where both the light neutrino masses and the deviation from tribimaximal mixing matrix can be linked to the source of lepton number violation. The hierarchies of the charged leptons are explained. We find that the quark masses including their hierarchies and the mixing can also be constructed in a similar way.

The decay rate of neutrinoless double beta ($0\nu \beta \beta$) decay contains terms from heavy particle exchange, which lead to dimension-9 ($d=9$) six fermion operators at low energies. Limits on the coefficients of these operators have been derived previously neglecting the running of the operators between the high scale, where they are generated, and the energy scale of $0\nu \beta \beta$ decay, where they are measured. Here we calculate the leading-order QCD corrections to all possible $d=9$ operators contributing to the $0\nu \beta \beta$ amplitude and use renormalization group running to calculate 1-loop improved limits. Numerically, QCD running dramatically changes some limits by factors of the order of or larger than typical uncertainties in nuclear matrix element calculations. For some specific cases, operator mixing in the running changes limits even by up to 3 orders of magnitude. Our results can be straightforwardly combined with new experimental limits or improved nuclear matrix element calculations to rederive updated limits on all short-range contributions to $0\nu \beta \beta$ decay.

We calculate the unpolarized transverse momentum dependent fragmentation function at next-to-next-to-leading order, evaluating separately the transverse momentum dependent (TMD) soft factor and the TMD collinear correlator. For the first time, the cancellation of spurious rapidity divergences in a properly defined individual TMD beyond the first nontrivial order is shown. This represents a strong check of the given TMD definition. We extract the matching coefficient necessary to perform the transverse momentum resummation at next-to-next-to-next-to-leading-logarithmic accuracy. The universal character of the soft function, which enters the definition of all (un)polarized TMD distribution/fragmentation functions, facilitates the future calculation of all the other TMDs and their coefficients at next-to-next-to-leading order, pushing forward the accuracy of theoretical predictions for the current and next generation of high energy colliders.

The generalized $CP$ transformations can only be consistently defined in the context of $\mathrm{\Delta }(3n^2)$ lepton symmetry if a certain subset of irreducible representations are present in a model. We perform a comprehensive analysis of the possible automorphisms and the corresponding $CP$ transformations of the $\mathrm{\Delta }(3n^2)$ group. It is sufficient to only consider three automorphisms if $n$ is not divisible by 3 while an additional eight types of $CP$ transformations could be imposed for the case of $n$ divisible by 3. We study the lepton mixing patterns which can be derived from the $\mathrm{\Delta }(3n^2)$ family symmetry and generalized $CP$ in the semidirect approach. The PMNS matrix is determined to be the trimaximal pattern for all the possible $CP$ transformations, and it can only take two distinct forms.

The Collins-Williams Regge calculus models of Friedmann-Lemaître-Robertson-Walker (FLRW) space-times and Brewin’s subdivided models are applied to closed vacuum $\mathrm{\Lambda }$-FLRW universes. In each case, we embed the Regge Cauchy surfaces into 3-spheres in ${\mathbf{E}}^4$ and consider possible measures of Cauchy surface radius that can be derived from the embedding. Regge equations are obtained from both global variation, where entire sets of identical edges get varied simultaneously, and local variation, where each edge gets varied individually. We explore the relationship between the two sets of solutions, the conditions under which the Regge Hamiltonian constraint would be a first integral of the evolution equation, the initial value equation for each model at its moment of time symmetry, and the performance of the various models. It is revealed that local variation does not generally lead to a viable Regge model. It is also demonstrated that the various models do satisfy their respective initial value equations. Finally, it is shown that the models reproduce the correct qualitative dynamics of the space-time. Furthermore, the approximation’s accuracy is highest when the universe is small but improves overall as we increase the number of tetrahedra used to construct the Regge Cauchy surface. Eventually though, all models gradually fail to keep up with the continuum FLRW model’s expansion, with the models with lower numbers of tetrahedra falling away more quickly. We believe this failure to keep up is due to the finite resolution of the Regge Cauchy surfaces trying to approximate an ever expanding continuum Cauchy surface; each Regge surface has a fixed number of tetrahedra and as the surface being approximated gets larger, the resolution would degrade. Finally, we note that all Regge models end abruptly at a point when the timelike struts of the skeleton become null, though this end point appears to get delayed as the number of tetrahedra is increased.

In a realistic interacting system described by ($2+1$)-dimensional quantum electrodynamics (${\mathrm{QED}}_3$), there is always a certain number of impurities by which fermions are scattered. In general, impurity scattering can generate a finite density of states at the Fermi level, which screens the temporal component of the gauge field. This effect is expected to weaken dynamical fermion mass generation. Within the Born approximation, by introducing a damping term in the energy component of the fermion propagator, the influences of finite temperature and impurity scattering on the chiral phase transition in ${\mathrm{QED}}_3$ are investigated. Pursuing this aim, we solve the Dyson-Schwinger equations for the fermion and boson propagators to the leading order in $1/N_f$ expansion at zero frequency and then calculate the chiral condensate, the chiral susceptibility, and the thermal susceptibility within a range of the impurity scattering rates $\mathrm{\Gamma }$ and the numbers of fermion flavors $N_f$. It is found that impurity scattering leads to an obvious suppression of the dynamical fermion mass generation and critical temperature $T_c$.

The Galactic Center excess of gamma ray photons can be naturally explained by light Majorana fermions in combination with a pseudoscalar mediator. The next-to-minimal supersymmetric Standard Model (NMSSM) provides exactly these ingredients. We show that for neutralinos with a significant singlino component the Galactic Center excess can be linked to invisible decays of the Standard Model–like Higgs at the LHC. We find predictions for invisible Higgs branching ratios in excess of 50%, easily accessible at the LHC. Constraining the NMSSM through grand-unified-theory (GUT)-scale boundary conditions only slightly affects this expectation. Our results complement earlier NMSSM studies of the Galactic Center excess, which link it to heavy Higgs searches at the LHC.

We calculate the energy of the state closest to threshold for two and three identical, spinless particles confined to a cubic spatial volume with periodic boundary conditions and with zero total momentum in the finite-volume frame. The calculation is performed in relativistic quantum field theory with particles coupled via a $\lambda {\varphi }^4$ interaction, and we work through order ${\lambda }^3$. The energy shifts begin at $\mathcal{O}(1/L^3)$, and we keep subleading terms proportional to $1/L^4$, $1/L^5$ and $1/L^6$. These terms allow a nontrivial check of the results obtained from quantization conditions that hold for arbitrary interactions, namely that of Lüscher for two particles and our recently developed formalism for three particles. We also compare to previously obtained results based on nonrelativistic quantum mechanics.

We present a detailed study of the production and decay of the excited quark at the QCD next-to-leading order (NLO) level at the Large Hadron Collider, using the narrow width approximation and helicity amplitudes method. We find that the QCD NLO corrections can tighten the constraints on the model parameters and reduce the scale dependencies of the total cross sections. We discuss the signals of the excited quark production with decay mode $q^{*}\to q\gamma$ and $q^{*}\to qg$, and present several important kinematic distributions. Moreover, we give the upper limits of the excited quark excluded mass range and the allowed parameter space for the coupling constants and the excited quark mass.

Jet substructure observables play a central role at the Large Hadron Collider for identifying the boosted hadronic decay products of electroweak scale resonances. The complete description of these observables requires understanding both the limit in which hard substructure is resolved, as well as the limit of a jet with a single hard core. In this paper we study in detail the perturbative structure of two prominent jet substructure observables, $N$-subjettiness and the energy correlation functions, as measured on background QCD jets. In particular, we focus on the distinction between the limits in which two-prong structure is resolved or unresolved. Depending on the choice of subjet axes, we demonstrate that at fixed order, $N$-subjettiness can manifest myriad behaviors in the unresolved region: smooth tails, end point singularities, or singularities in the physical region. The energy correlation functions, by contrast, only have nonsingular perturbative tails extending to the end point. We discuss the effect of hadronization on the various observables with Monte Carlo simulation and demonstrate that the modeling of these effects with nonperturbative shape functions is highly dependent on the $N$-subjettiness axes definitions. Our study illustrates those regions of phase space that must be controlled for high-precision jet substructure calculations, and emphasizes how such calculations can be facilitated by designing substructure observables with simple singular structures.

We study the processes $\gamma \gamma \to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $\gamma \gamma \to K^{+}{K}^{-}{\pi }^0$ using a data sample of $519{\mathrm{fb}}^{-1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at center-of-mass energies at and near the $\mathrm{{\rm Y}}(nS)$ ($n=2$, 3, 4) resonances. We observe ${\eta }_c$ decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the $I=1/2$ $K\pi \mathcal{S}$-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of $1.5\mathrm{GeV}/c^2$. In contrast, the amplitudes show very marked differences. The data require the presence of a new $a_0(1950)$ resonance with parameters $m=1931\pm 14\pm 22\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=271\pm 22\pm 29\mathrm{MeV}$.

We studied the evolution of the Wightman correlator in a thermalizing state modeled by ${\mathrm{AdS}}_3$-Vaidya background. We gave a prescription for calculating the Wightman correlator in coordinate space without using any approximation. For equal-time correlator $⟨O(v,x)O(v,0)⟩$, we obtained an enhancement factor $v^2$ due to long range correlation present in the initial state. This was missed by previous studies based on geodesic approximation. We found that the long range correlation in initial state does not lead to significant modification to thermalization time as compared to known results with generic initial state. We also studied the spatially integrated Wightman correlator and showed evidence on the distinction between long distance and small momentum physics for an out-of-equilibrium state. We also calculated the radiation spectrum of particles weakly coupled to $O$ and found that lower frequency mode approaches thermal spectrum faster than high frequency mode.

In this work, we perform a detailed dynamical analysis for the cosmological applications of a nonminimal torsion-matter coupled gravity. Two alternative formalisms are proposed, which enable one to choose between the easier approach for a given problem, and furthermore, we analyze six specific models. In general, we extract fixed points corresponding either to dark-matter-dominated, scaling decelerated solutions, or to dark-energy-dominated accelerated solutions. Additionally, we find that there is a small parameter region in which the model can experience the transition from the matter epoch to the dark-energy era. These features are in agreement with the observed evolution of the Universe, and make the theory a successful candidate for the description of nature.

The emergence of the I-Love-Q relations, revealing that the moment of inertia, the tidal Love number (deformability) and the spin-induced quadrupole moment of compact stars are, to high accuracy, interconnected in a universal way disregarding the wide variety of equations of state (EOSs) of dense matter, has attracted much interest recently. However, the physical origin of these relations is still a debatable issue. In the present paper, we focus on the I-Love relation for self-bound stars (SBSs) such as incompressible stars and quark stars. We formulate perturbative expansions for the moment of inertia, the tidal Love number (deformability) and the I-Love relation of SBSs. By comparing the respective I-Love relations of incompressible stars and a specific kind of SBSs, we show analytically that the I-Love relation is, to relevant leading orders in stellar compactness, stationary with respect to changes in the EOS about the incompressible limit. Hence, the universality of the I-Love relation is indeed attributable to the proximity of compact stars to incompressible stars, and the stationarity of the relation as unveiled here. We also discover that the moment of inertia and the tidal deformability of a SBS with finite compressibility are, to leading order in compactness, equal to their counterparts of an incompressible star with an adjusted compactness, thus leading to a novel explanation for the I-Love universal relation.

Classical as well as quantum features of the late-time evolution of cosmological models with fluids obeying a Shan-Chen-like equation of state are studied. The latter is of the type $p=w_{\text{eff}}(\rho )\rho$ and has been used in previous works to describe, e.g., a possible scenario for the growth of the dark-energy content of the present Universe. At the classical level, the fluid dynamics in a spatially flat Friedmann-Robertson-Walker background implies the existence of two possible equilibrium solutions depending on the model parameters associated with (asymptotic) finite pressure and energy density. We show that no future cosmological singularity is developed during the evolution for this specific model. The corresponding quantum effects in the late-time behavior of the system are also investigated within the framework of quantum geometrodynamics, i.e., by solving the (minisuperspace) Wheeler-DeWitt equation in the Born-Oppenheimer approximation, constructing wave packets and analyzing their behavior.

The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. Simulations indicated a very nonlinear dependence of the signal strength in the frequency window of 30–80 MHz on the magnitude of the atmospheric electric field. In this work we present an explanation of this dependence based on Monte Carlo simulations, supported by arguments based on electron dynamics in air showers and expressed in terms of a simplified model. We show that by extending the frequency window to lower frequencies, additional sensitivity to the atmospheric electric field is obtained.

We study the process of radiative neutrino pair emission $|e⟩\to |g⟩+\gamma +\nu \overline{\nu }$ from coherently excited heavy ions (quantum mixture of two ionic states—ground and excited states) in circular motion. Determination of the neutrino mass is found to be possible with simultaneous detection of the photon and one of the neutrinos in the pair down to the level of the smallest neutrino mass of order 5 meV in the three-flavor scheme.

A search for fermionic top quark partners $T$ of charge $2/3$ is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of $19.7{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ with the CMS detector at the LHC. The $T$ quarks are assumed to be produced strongly in pairs and can decay into $tH$, $tZ$, and $bW$. The search is performed in five exclusive channels: a single-lepton channel, a multilepton channel, two all-hadronic channels optimized either for the $bW$ or the $tH$ decay, and one channel in which the Higgs boson decays into two photons. The results are found to be compatible with the standard model expectations in all the investigated final states. A statistical combination of these results is performed and lower limits on the $T$ quark mass are set. Depending on the branching fractions, lower mass limits between 720 and 920 GeV at 95% confidence level are found. These are among the strongest limits on vectorlike $T$ quarks obtained to date.