The twin Higgs model is the preeminent example of a theory of neutral naturalness, where the new particles that alleviate the little hierarchy problem are Standard Model (SM) singlets. The most promising collider search strategy, based on rare Higgs decays, is nevertheless not effective in significant regions of the parameter space of the low-energy theory. This underlines the importance of phenomenological studies on ultraviolet completions of the twin Higgs model, which must lie at a scale lower than 5–10 TeV. We pursue this course in the context of nonsupersymmetric completions, focusing on exotic fermions that carry SM electroweak and twin color charges, as well as on exotic vectors that transform as the bifundamental of the electroweak or color groups. Both $Z_2$-preserving and $Z_2$-breaking mass spectra are considered for the exotic fermions. In the former case they must be heavier than $\sim 1\mathrm{TeV}$, but can still be sizably produced in the decays of the color bifundamental vector. In the $Z_2$-breaking scenario, the exotic fermions can have masses in the few hundred GeV range without significantly increasing the fine-tuning. Once pair-produced through the electroweak interactions, they naturally form bound states held together by the twin color force, which subsequently annihilate back to SM particles. The associated resonance signals are discussed in detail. We also outline the phenomenology of the electroweak bifundamental vectors, some of which mix with the SM $W$ and $Z$ and can therefore be singly produced in hadron collisions.

We study the evolution of the coupling in SU(2) gauge field theory with $N_f=8$ fundamental fermion flavors on the lattice. This model is expected to have an infrared fixed point at high coupling. We use HEX-smeared Wilson-clover action, and measure the gradient flow running coupling with Dirichlet boundary conditions. Extrapolating our results to continuum, we find an infrared fixed point at $g_{*}^2=8.24(59{)}_{-1.64}^{+0.97}$, with statistical and systematic error estimates. We also measure the anomalous dimension of the quark mass operator, and find its value at the fixed point ${\gamma }_{*}\simeq 0.15\pm 0.02$, although for this quantity a reliable continuum limit is still lacking.

We introduce a technique to study double parton scattering (DPS) in the color-glass-condensate (CGC) approach. We show that the cross section of the DPS in the CGC approach is calculable in terms of new nonperturbative objects, generalized double transverse momentum-dependent parton distribution (2GTMD) functions. We investigate the production of pairs of prompt photons from two partons in the projectile hadron in high-energy proton-nucleus collisions. We show that even for independent partons in the projectile, the prompt photon correlation function exhibits Hanbury Brown and Twiss (HBT) correlations. The width of the HBT peak is controlled by the transverse distance between the partons of the pair, which is of the order of the proton size. Thus, the HBT measurements in two-particle production such as prompt photon pairs provide useful information about the nonperturbative 2GTMDs.

We revisit the calculation of rapidity dependence of the average transverse momentum $⟨p_T⟩$ of single inclusive jet production or particle in a $p+p$ and $p-\mathrm{Pb}$ collision, using the high energy factorization. We update previous predictions for the $⟨p_T⟩$ both in central and forward rapidity region using parton densities following from extended Balitsky-Kovchegov and Balitsky-Fadin-Kuraev-Lipatov evolution equations to account for corrections of higher orders as well as one obtained by Sudakov resummation. Furthermore, we demonstrate that in the midrapidity region the saturation based formalisms predict increase of the transversal momentum while in the forward rapidity region the $⟨p_T(y)⟩$ decreases.

We present a full evaluation of the deeply virtual Compton scattering cross section in the dipole framework in the small-$x$ region. The result features the $\cos \varphi$ and $\cos 2\varphi$ azimuthal angular correlations, which have been missing in previous studies based on the dipole model. In particular, the $\cos 2\varphi$ term is generated by the elliptic gluon Wigner distribution of which the measurement at the planned electron-ion collider provides important information about the gluon tomography at small $x$. We also show the consistency with the standard collinear factorization approach based on the quark and gluon generalized parton distributions.

The Lam-Tung relation breaking coefficient $A_{\mathrm{LT}}=A_0-A_2$ in the Drell-Yan dilepton angular distributions in the $Z^0$ boson mass region at the LHC is analyzed in the $k_T$-factorization approach. This observable was recently measured with high precision by the ATLAS Collaboration. Within the $k_T$-factorization approach we perform an approximate $\mathcal{O}({\alpha }_{\mathrm{em}}{\alpha }_s^2)$ calculation of the off-shell parton hard matrix elements in which we include the leading tree-level contributions of valence quarks and off-shell gluons: the $q_{\mathrm{val}}{g}^{*}\to q{Z}^0$ channel and the $g^{*}{g}^{*}\to q\overline{q}{Z}^0$ channel. The resulting $A_{\mathrm{LT}}$ exhibits high sensitivity to the gluon transverse momentum distribution (TMD). Several gluon TMDs are probed derived from the Catani-Ciafaloni-Fiorani-Marchesini and Balisky-Fadin-Kuraev-Lipatov evolution equations, and given by QCD-inspired phenomenological parameterizations. The ATLAS data favor a simple “Weizsäcker-Williams” (WW) hard gluon TMD with the asymptotic behavior of one-gluon exchange at large gluon transverse momenta and moderate $x$. It is verified that the proposed approach with the WW gluon TMD describes well also the $A_0$ and $A_2$ angular coefficients at the $Z^0$ peak, as well as the Drell-Yan dilepton mass distribution at lower masses. We conclude that the inclusion of gluon transverse momentum effects improves the description of the angular distributions of Drell-Yan dileptons and that the Drell-Yan scattering provides an excellent probe of the parton TMDs.

Hadronic decay widths of the newly observed charmed strange baryons, ${\mathrm{\Omega }}_c(3000{)}^0$, ${\mathrm{\Omega }}_c(3050{)}^0$, ${\mathrm{\Omega }}_c(3066{)}^0$, ${\mathrm{\Omega }}_c(3090{)}^0$, and ${\mathrm{\Omega }}_c(3119{)}^0$ have been calculated in a ${}^3{P}_0$ model. Our results indicate that ${\mathrm{\Omega }}_c(3066{)}^0$ and ${\mathrm{\Omega }}_c(3090{)}^0$ can be interpreted as the $1P$–wave ${\mathrm{\Omega }}_{c2}({\frac{3}{2}}^{-})$ or ${\mathrm{\Omega }}_{c2}({\frac{5}{2}}^{-})$. Though the measured masses of ${\mathrm{\Omega }}_c(3000{)}^0$, ${\mathrm{\Omega }}_c(3050{)}^0$, and ${\mathrm{\Omega }}_c(3119{)}^0$ are lower than existed theoretical predictions of $1D$–wave ${\mathrm{\Omega }}_c$, the hadronic decay features of these ${\mathrm{\Omega }}_c$ favor assignments of the $1D$–wave states. ${\mathrm{\Omega }}_c(3000{)}^0$ is possibly ${\mathrm{\Omega }}_{c1}({\frac{1}{2}}^{+})$ or ${\mathrm{\Omega }}_{c1}({\frac{3}{2}}^{+})$, ${\mathrm{\Omega }}_c(3050{)}^0$ is possibly ${\widehat{\mathrm{\Omega }}}_{c3}({\frac{5}{2}}^{+})$ or ${\widehat{\mathrm{\Omega }}}_{c3}({\frac{7}{2}}^{+})$, and ${\mathrm{\Omega }}_c(3119{)}^0$ is possibly ${\widehat{\mathrm{\Omega }}}_{c3}({\frac{5}{2}}^{+})$, ${\widehat{\mathrm{\Omega }}}_{c3}({\frac{7}{2}}^{+})$, ${\mathrm{\Omega }}_{c3}({\frac{5}{2}}^{+})$ or ${\mathrm{\Omega }}_{c3}({\frac{7}{2}}^{+})$. The predicted total decay widths in these assignments are consistent with experiment under theoretical and experimental uncertainties.

A class of extensions of the Standard Model allows Lorentz and $CPT$ violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and $CPT$-violating terms from the Standard Model extension have been derived by taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than $10^{20}$ at the GeV scale.

We study the emission of soft photons coupling to high energy fixed angle scattering processes at first order in the electromagnetic coupling but to all loop orders in a class of theories without soft divergences, including massive and massless Yukawa and scalar theories. We adapt a method introduced by del Duca for quantum electrodynamics to show that subleading corrections to the soft photon theorem are sensitive to the structure of nonleading external jets of collinear lines. Our techniques are based on a power counting analysis of loop integrals and an application of jet Ward identities. We also apply Grammer and Yennie’s decomposition to isolate separately gauge invariant contributions to the soft photon expansion. These are interpreted as infrared sensitive matrix elements coupling to a field strength tensor.

In this paper, we revisit the issue of static hairs of black holes in gravitational theories with broken Lorentz invariance in the case that the speed $c_{\varphi }$ of the khronon field becomes infinitely large, $c_{\varphi }=\infty$, for which the sound horizon of the khronon field coincides with the universal horizon, and the boundary conditions at the sound horizon reduce to those given normally at the universal horizons. As a result, fewer boundary conditions are present in this extreme case in comparison with the case $c_{\varphi }=\mathrm{finite}$. Consequently, it is expected that static hairs might exist. However, we show analytically that, even in this case, static hairs still cannot exist, based on a decoupling limit analysis. We also consider the cases in which $c_{\varphi }$ is finite but with $c_{\varphi }\gg 1$, and we obtain the same conclusion.

We study the gravitational collapse of radiating stars in the context of the cosmic censorship conjecture. We consider a generalized Vaidya spacetime with three concentric regions. The local internal atmosphere is a two-component system consisting of standard pressure-free, null radiation and an additional string fluid with energy density and nonzero pressure obeying all physically realistic energy conditions. The middle region is purely radiative which matches to a third region which is the Schwarzschild exterior. We outline the general mathematical framework to study the conditions on the mass function so that future-directed nonspacelike geodesics can terminate at the singularity in the past. Mass functions for several equations of state are analyzed using this framework and it is shown that the collapse in each case terminates at a locally naked central singularity. We calculate the strength of these singularities to show that they are strong curvature singularities which implies that no extension of spacetime through them is possible.

The validity of the cosmic censorship conjecture for the Kerr-Sen black hole, which is a solution to the low-energy effective field theory for four-dimensional heterotic string theory, is investigated using charged particle absorption. When the black hole absorbs the particle, the charge on it changes owing to the conserved quantities of the particle. Changes in the black hole are constrained to the equation for the motion of the particle and are consistent with the laws of thermodynamics. Particle absorption increases the mass of the Kerr-Sen black hole to more than that of the absorbed charges such as angular momentum and electric charge; hence, the black hole cannot be overcharged. In the near-extremal black hole, we observe a violation of the cosmic censorship conjecture for the angular momentum in the first order of expansion and the electric charge in the second order. However, considering an adiabatic process carrying the conserved quantities as those of the black hole, we prove the stability of the black hole horizon. Thus, we resolve the violation. This is consistent with the third law of thermodynamics.

We consider the parametrized post-Newtonian (PPN) limit of ghost-free massive bimetric gravity with two mutually noninteracting matter sectors coupled to the two metrics. Making use of a gauge-invariant differential decomposition of the metric perturbations, we solve the field equations up to the linear PPN order for a static, pointlike mass source. From the result, we derive the PPN parameter $\gamma$ for spherically symmetric systems, which describes the gravitational deflection of light by visible matter. By a comparison to its value measured in the Solar System, we obtain bounds on the parameters of the theory. We further discuss the deflection of light by dark matter and find an agreement with the observed light deflection by galaxies. We finally speculate about a possible explanation for the observed distribution of dark matter in galactic mergers such as Abell 520 and Abell 3827.

We examined the viability of a new type of charged $Q$-ball dark matter scenario. We considered the case where the relics can be treated as ordinary ions, to which we applied the observational constraint from the MICA experiment, where no trail of heavy ionlike object is observed in $10^9$ year-old ancient muscovite mica. We have found that the allowed parameter region exists but is smaller than the neutral $Q$-ball dark matter case. We have also discussed whether our scenario is actually consistent with Affleck-Dine mechanism.

Diphoton resonance was a crucial discovery mode for the 125 GeV Standard Model Higgs boson at the Large Hadron Collider (LHC). This mode or the more general diboson modes may also play an important role in probing for new physics beyond the Standard Model. In this paper, we consider the possibility that a diphoton resonance is due to a composite scalar or pseudoscalar boson, whose constituents are either new hyperquarks $Q$ or scalar hyperquarks $\tilde{Q}$ confined by a new hypercolor force at a confinement scale ${\mathrm{\Lambda }}_h$. Assuming the mass $m_Q$ (or $m_{\tilde{Q}}$) $\gg {\mathrm{\Lambda }}_h$, a diphoton resonance could be interpreted as either a $Q\overline{Q}({{}^{1}S}_0)$ state ${\eta }_Q$ with $J^{PC}=0^{-+}$ or a $\tilde{Q}{\tilde{Q}}^{†}({}^1{S}_0)$ state ${\eta }_{\tilde{Q}}$ with $J^{PC}=0^{++}$. For the $Q\overline{Q}$ scenario, there will be a spin-triplet partner ${\psi }_Q$ which is slightly heavier than ${\eta }_Q$ due to the hyperfine interactions mediated by hypercolor gluon exchange; while for the $\tilde{Q}{\tilde{Q}}^{†}$ scenario, the spin-triplet partner ${\chi }_{\tilde{Q}}$ arises from higher radial excitation with nonzero orbital angular momentum. We consider productions and decays of ${\eta }_Q$, ${\eta }_{\tilde{Q}}$, ${\psi }_Q$, and ${\chi }_{\tilde{Q}}$ at the LHC using the nonrelativistic QCD factorization approach. We discuss how to test these scenarios by using the Drell-Yan process and the forward dijet azimuthal angular distributions to determine the $J^{PC}$ quantum number of the diphoton resonance. Constraints on the parameter space can be obtained by interpreting some of the small diphoton “excesses” reported by the LHC as the composite scalar or pseudoscalar of the model. Another important test of the model is the presence of a nearby hypercolor-singlet but color-octet state like the ${}^1{S}_0$ state ${\eta }_Q^8$ or ${\eta }_{\tilde{Q}}^8$, which can also be constrained by dijet or monojet plus monophoton data. Both possibilities of a large or small width of the resonance can be accommodated, depending on whether the hyper-glueball states are kinematically allowed in the final state or not.

Realizing that couplings related by supersymmetry (SUSY) can be disentangled when SUSY is broken, it is suggested that unwanted flavor and $CP$-violating SUSY couplings may be suppressed via quenched gaugino-flavor interactions, which may be accomplished by power-law running of sfermion anomalous dimensions. A simple theoretical framework to accomplish this is exemplified, where a strongly coupled conformal field theory is achieved after SUSY is softly broken. The defeated constraints are tallied. One key implication of the scenario is the expectation of enhanced top, bottom and tau production at the LHC, accompanied by large missing energy. Also, direct detection signals of dark matter may be more challenging to find than in conventional SUSY scenarios.

We study analytically the one-loop contribution to the chiral magnetic effect (CME) using lattice regularization with a Wilson fermion field. In the continuum limit, we find that the chiral magnetic current vanishes at nonzero temperature but emerges at zero temperature consistent with that found by Pauli-Villas regularization. For finite lattice size, however, the chiral magnetic current is nonvanishing at nonzero temperature. But the numerical value of the coefficient of CME current is very small compared with that extracted from the full QCD simulation for the same lattice parameters. The possibility of higher-order corrections from QCD dynamics is also assessed.

We consider the conversion of an electric field into photons as a secondary probe of the dynamical Schwinger process. In spatially homogeneous electric fields, quantum fluctuations of electron-positron ($e^{+}{e}^{-}$) pairs are lifted on the mass shell leaving asymptotically a small finite pair density. The $e^{+}{e}^{-}$ dynamics, in turn, couples to the quantized photon field and drives its on-shell mode occupation. The spectral properties of the emerging asymptotic photons accompanying the Schwinger process are calculated in lowest-order perturbation theory. Soft photons in the optical range are produced amass in the subcritical region, thus providing a promising discovery avenue, e.g. for laser parameters of the Extreme Light Initiative (ELI-NP) to be put in operation soon.