Motivated by the ATLAS and CMS announcements of the excesses of diphoton events, we discuss the production and decay processes of diphoton resonance at future $e^{+}{e}^{-}$ colliders. We assume that the excess of the diphoton events at the LHC is explained by a scalar resonance decaying into a pair of photons. In such a case, the scalar interacts with standard model gauge bosons and, consequently, the production of such a scalar is possible at the $e^{+}{e}^{-}$ colliders. We study the production of the scalar resonance via the associated production with the photon or $Z$, as well as via the vector-boson fusion, and calculate the cross sections of these processes. We also study the backgrounds, and discuss the detectability of the signals of scalar production with various decay processes of the scalar resonance. We also consider the case where the scalar resonance has an invisible decay mode, and study how the invisible decay can be observed at the $e^{+}{e}^{-}$ colliders.

In models with multiple nondegenerate Higgs bosons, the decay chain $H/A\to A/HZ\to t\overline{t}Z$ may have a partial width comparable to the $t\overline{t}$ decay mode. We recast the ATLAS standard model $t\overline{t}Z$ measurement to put limits on the rate for this process. Limits are also set on the two Higgs doublet model at low $\tan \beta$ that are sensitive to a heavy Higgs mass as high as $\sim 750\mathrm{GeV}$. We then discuss the 750 GeV diphoton excess in terms of a pseudoscalar that also has the decays $A\to HZ$ and $A\to H^{\pm }{W}^{\mp }$. These decays strongly constrain the partial widths for $A\to \gamma \gamma$ and $A\to gg$ when combined with the $t\overline{t}$ resonance search limits. In a benchmark model the mass of $H$ should be close to 650 GeV.

In the present paper, we discuss how to maximize the double-parton scattering (DPS) contribution in four-jet production by selecting kinematical cuts. Here both single-parton and double-parton scattering effects are calculated in the $k_T$-factorization approach, following our recent developments of relevant methods and tools. Several differential distributions are shown and discussed in the context of future searches for DPS effects, such as rapidity of jets, rapidity distance, and azimuthal correlations between jets. The dependence of the relative DPS amount is studied as a function of those observables. The regions with an enhanced DPS contribution are identified. Future experimental explorations could extract more precise values of ${\sigma }_{\mathrm{eff}}$ and its potential dependence on kinematical variables.

Radiative ${\overline{B}}^0({\overline{B}}_s^0)\to J/\psi \gamma$ decays provide an interesting case to test our understanding of (non)perturbative QCD and eventually to probe physics beyond the standard model. Recently, the LHCb Collaboration reported an upper bound, updating the results of the BABAR Collaboration. Previous theoretical predictions based on QCD factorization or perturbative QCD have shown large variations due to different treatment of nonfactorizable contributions and meson-photon transitions. In this paper, we report on a novel approach to estimate the decay rates, which is based on a recently proposed model for $B$ decays and the vector meson dominance hypothesis, widely tested in the relevant energy regions. The predicted branching ratios are $\mathrm{Br}[{\overline{B}}^0\to J/\psi \gamma ]=(3.50\pm {0.34}_{-0.63}^{+1.12})\times {10}^{-8}$ and $\mathrm{Br}[{\overline{B}}_s^0\to J/\psi \gamma ]=(7.20\pm {0.68}_{-1.30}^{+2.31})\times {10}^{-7}$. The first uncertainty is systematic and the second is statistical, originating from the experimental ${\overline{B}}_s^0\to J/\psi \varphi$ branching ratio.

In this paper we present the full next-to-leading-order (NLO) $\mathrm{QCD}+\mathrm{NLO}$ electroweak (EW) corrections to the $Z$-boson pair production in association with a hard jet at the LHC. The subsequent $Z$-boson leptonic decays are included by adopting both the naive narrow-width approximation and madspin methods for comparison. Since the $ZZ+\text{jet}$ production is an important background for single Higgs boson production and new physics searches at hadron colliders, the theoretical predictions with high accuracy for the hadronic production of $ZZ+\text{jet}$ are necessary. We present the numerical results of the integrated cross section and various kinematic distributions of final particles, and conclude that it is necessary to take into account the spin correlation and finite-width effects from the $Z$-boson leptonic decays. We also find that the NLO EW correction is quantitatively non-negligible in matching the experimental accuracy at the LHC, particularly in the high-transverse-momentum region.

We present a search for a non-Standard-Model invisible particle $X^0$ in the mass range $0.1–1.8\mathrm{GeV}/c^2$ in $B^{+}\to e^{+}{X}^0$ and $B^{+}\to {\mu }^{+}{X}^0$ decays. The results are obtained from a $711{\mathrm{fb}}^{-1}$ data sample that corresponds to $772\times 10^{6}B\overline{B}$ pairs, collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. One $B$ meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner $B$ meson. We find no evidence of a signal and set upper limits on the order of ${10}^{-6}$.

Using the eight time dependences ${\mathrm{e}}^{-\mathrm{\Gamma }t}(1+C_i\cos \mathrm{\Delta }mt+S_i\sin \mathrm{\Delta }mt)$ for the decays $\mathrm{{\rm Y}}(4S)\to B^0{\overline{B}}^0\to f_j{f}_k$, with the decay into a flavor-specific state $f_j={\ell }^{\pm }X$ before or after the decay into a $CP$ eigenstate $f_k=c\overline{c}{K}_{S,L}$, as measured by the BABAR experiment, we determine the three $CPT$-sensitive parameters $\mathrm{Re}(\mathsf{z})$ and $\mathrm{Im}(\mathsf{z})$ in $B^0\text{−}{\overline{B}}^0$ mixing and $|\overline{A}/A|$ in $B^0\to c\overline{c}{K}^0$ decays. We find $\mathrm{Im}(\mathsf{z})=0.010\pm 0.030\pm 0.013$, $\mathrm{Re}(\mathsf{z})=-0.065\pm 0.028\pm 0.014$, and $|\overline{A}/A|=0.999\pm 0.023\pm 0.017$, in agreement with $CPT$ symmetry.

We investigate finite ${\alpha }^{\prime }$ effects in string theory on a black hole background. By explicitly computing tree-level scattering amplitudes, we confirm a duality between seemingly different states recently conjectured by Giveon, Itzhaki, and Kutasov. We verify that the relevant 3-point functions factorize in such a way that the duality between oscillator and winding states becomes manifest. This leads us to determine the precise normalization of the dual vertex operators, and confirms at the level of the interacting theory the identification of states suggested by the analysis of the spectrum. This result implies a duality between two seemingly distinct mechanisms driving the violation of the string winding number in the black hole atmosphere.

We consider six-dimensional supergravity with Abelian bulk flux compactified on an orbifold. The effective low-energy action can be expressed in terms of $\mathcal{N}=1$ chiral moduli superfields with a gauged shift symmetry. The $D$-term potential contains two Fayet-Iliopoulos terms which are induced by the flux and by the Green-Schwarz term canceling the gauge anomalies, respectively. The Green-Schwarz term also leads to a correction of the gauge kinetic function which turns out to be crucial for the existence of Minkowski and de Sitter vacua. Moduli stabilization is achieved by the interplay of the $D$-term and a nonperturbative superpotential. Varying the gauge coupling and the superpotential parameters, the scale of the extra dimensions can range from the GUT scale down to the TeV scale. Supersymmetry is broken by $F$- and $D$-terms, and the scale of gravitino, moduli, and modulini masses is determined by the size of the compact dimensions.

In this paper, we study the RG flow in the nonlinear sigma models obtained from a 2D $\mathcal{N}=(0,2)$ supersymmetric QCD. The sigma model is parametrized by a single Kahler modulus. We determine its exact nonperturbative beta function using holomorphy, triality and the knowledge of the infrared fixed point.

We present an analysis of an $f(T,\mathcal{T})$ extension of the Teleparallel Equivalent of General Relativity, where $T$ denotes the torsion and $\mathcal{T}$ denotes the trace of the energy-momentum tensor. This extension includes nonminimal couplings between torsion and matter. In particular, we construct two specific models that recover the usual continuity equation, namely, $f(T,\mathcal{T})=T+g(\mathcal{T})$ and $f(T,\mathcal{T})=T\times g(\mathcal{T})$. We then constrain the parameters of each model by fitting the predicted distance modulus to that measured from type Ia supernovae and find that both models can reproduce the late-time cosmic acceleration. We also observe that one of the models satisfies well the observational constraints and yields a goodness-of-fit similar to the $\mathrm{\Lambda }\mathrm{CDM}$ model, thus demonstrating that $f(T,\mathcal{T})$ gravity theory encompasses viable models that can be an alternative to $\mathrm{\Lambda }\mathrm{CDM}$.

It is expected that the cosmological black holes are the closest realistic solutions of gravitational theories and they evolve with time. Moreover, the natural way of defining thermodynamic entities for the stationary ones is not applicable in the case of a time dependent spacetime. Here we confine our discussion within the Sultana-Dyer metric, which is a cosmological black hole solution of Einstein’s gravity. In the literature, there exist two expressions of horizon temperature—one is time dependent and the other does not depend on time. To single out the correct one we find the temperature by studying the Hawking effect in the tunneling formalism. This leads to time dependent structure. After identifying the correct one, Einstein’s equations are written on the horizon and we show that this leads to the first law of thermodynamics. In this process the expressions for horizon entropy and energy, obtained earlier by explicit calculations, are being used. This provides the evidence that Einstein’s equations have thermodynamic structure even for a cosmological black hole spacetime. Moreover, this study further clarifies the correctness of the expressions for the thermodynamic quantities, like temperature, entropy, and internal energy.

Dark matter (DM) annihilations have been widely studied as a possible explanation of excess gamma rays from the Galactic Center seen by Fermi/LAT. However most such models are in conflict with constraints from dwarf spheroidals. Motivated by this tension, we show that $p$-wave annihilating dark matter can easily accommodate both sets of observations due to the lower DM velocity dispersion in dwarf galaxies. Explaining the DM relic abundance is then challenging. We outline a scenario in which the usual thermal abundance is obtained through $s$-wave annihilations of a metastable particle, that eventually decays into the $p$-wave annihilating DM of the present epoch. The couplings and lifetime of the decaying particle are constrained by big bang nucleosynthesis, the cosmic microwave background and direct detection, but significant regions of parameter space are viable. A sufficiently large $p$-wave cross section can be found by annihilation into light mediators, that also give rise to Sommerfeld enhancement. A prediction of the scenario is enhanced annihilations in galaxy clusters.

We analyze the lowest spectral moments of the left-right two-point correlation function, using all known short-distance constraints and the recently updated ALEPH $V-A$ spectral function from $\tau$ decays. This information is used to determine the low-energy couplings $L_{10}$ and $C_{87}$ of chiral perturbation theory and the lowest-dimensional contributions to the operator product expansion of the left-right correlator. A detailed statistical analysis is implemented to assess the theoretical uncertainties, including violations of quark-hadron duality.

The enigmatic charged states $Z_c(3900)$, $Z_c(4020)$, $Z_c(4050)$, $Z_b(10610)$, and $Z_b(10650)$ are studied within a coupled-channel Schrödinger model, where radially excited quark-antiquark pairs, with the same angular momenta and isospin as the $a_1(1260)$ and $b_1(1235)$, are strongly coupled to their Okubo-Zweig-Iizuka–allowed decay channels $D{\overline{D}}^{*}+\overline{D}{D}^{*}$ and $D^{*}{\overline{D}}^{*}$, or $B{\overline{B}}^{*}+\overline{B}{B}^{*}$ and $B^{*}{\overline{B}}^{*}$, in $S$ and $D$ waves. Poles, matching the experimental mass and width of the above states, are found by varying only two free parameters. From the wave-function analysis of each resonance, the probability of each of the components contributing to the coupled system is estimated, and predictions can be made for the relative decay fractions among the coupled open-charm or open-bottom decay channels.

To date, the nature of $Z_c(3900)/Z_c(4025)$ is not clear. In this work, we propose to study the internal structure of $Z_c(3900)/Z_c(4025)$ by exploring the charmless decays. Compared to charmed decays, charmless decay channels may play a unique role since they request the annihilation of the heavy constituents. We calculate the decay width for $Z_c(3900)/Z_c(4025)\to VP$, where $P$ and $V$ denote the pseudoscalar and light vector meson, respectively. Here, the $Z_c(3900)$ and $Z_c(4025)$ are the molecular states of $D^{*}\overline{D}$ and $D^{*}{\overline{D}}^{*}$. The decay process occurs through intermediate $D{D}^{*}/D^{*}{D}^{*}$ meson loops. Based on an effective Lagrangian, we obtain sizable predictions for the branching ratios, which are accessible in experiments. The experimental measurements in the future will not only shed light on the decay mechanism but will also lead to a deeper understanding of the mysterious structure of the $Z_c(3900)/Z_c(4025)$.

Recently it has been shown that the peak of the quarkonium entropy at the deconfinement transition is related to the emergent entropic force which destructs the quarkonium. Using the AdS/CFT correspondence, we consider dissociation of a moving heavy quarkonium by entropic force. For larger distance of quark and antiquark, the entropy of moving quarkonium increases, monotonically. We find that the entropic force destructs the moving quarkonium easier than the static case. By considering the Maxwell charge, we study the effect of the medium on the destruction of heavy quarkonium. It is shown that the quarkonium dissociates easier in the medium. Our results imply that the quarkonium dissociates easier when it moves orthogonal to the plasma wind rather than parallel.

Using numerical and analytic methods, we study quantum tunneling from a Minkowski false vacuum to an anti-de Sitter true vacuum. Scanning the parameter space of theories with quartic and nonpolynomial potentials, we find that for any given potential tunneling is completely quenched if gravitational effects are made sufficiently strong. For potentials where $\epsilon$, the energy density difference between the vacua, is small compared to the barrier height, this occurs in the thin-wall regime studied by Coleman and De Luccia. However, we find that other potentials, possibly with $\epsilon$ much greater than the barrier height, produce a new type of thin-wall bounce when gravitational effects become strong. We show that the critical curve that bounds the region in parameter space where the false vacuum is stable can be found by a computationally simple overshoot/undershoot argument. We discuss the treatment of boundary terms in the bounce calculation and show that, with proper regularization, one obtains an identical finite result for the tunneling exponent regardless of whether or not these are included. Finally, we briefly discuss the extension of our results to transitions between anti-de Sitter vacua.

There is a host of alternative theories of gravitation in the literature, among them the $f(R,T)$ and $f(R,T^{\varphi })$ theories recently elaborated by Harko et al. In these theories, $R$, $T$ and $T^{\varphi }$ are respectively the Ricci scalar and the traces of the energy-momentum tensors of matter and of a scalar field. There is already in the literature a series of studies of different forms of the $f(R,T)$ and $f(R,T^{\varphi })$ functions as well as their cosmological consequences. However, there have been no studies so far related to gravitational waves. Here we consider such an issue, in particular, studying the putative extra polarization modes that can appear in the scope of such theories. Different functional forms of $f(R,T^{\varphi })$ are considered and the gravitational waveforms are found for the extra polarization modes in the cases in which they are present.