This work gives a general overview of phenomenology developed for neutral-meson searches for $CPT$ violation in the framework of the Standard-Model Extension with focus on meson factories. It gives a comparison of notations and fundamental approach in the formalism used by the different experiments. Asymmetries and possible experimental investigations are presented for tests of the momentum-dependent phenomenological parameter of $CPT$ violation in correlated neutral-meson oscillations. The general results apply to any mesons produced as correlated meson pairs and address the issue of decoherence as a consequence of direction dependence. An analysis is given considering kinematics and orientation of the improved Belle II experiment.

In this addendum to Phys. Rev. D 95, 054018 (2017) we recompute the rates for the decays of the Higgs boson to a vector quarkonium plus a photon, where the vector quarkonium is $J/\psi$, $\mathrm{\Upsilon }(1S)$, $\mathrm{\Upsilon }(2S)$, or $\mathrm{\Upsilon }(3S)$. We correct an error in the Abel-Padé summation formula that was used to carry out the evolution of the quarkonium light-cone distribution amplitude in Phys. Rev. D 95, 054018 (2017). We also correct an error in the scale of quarkonium wave function at the origin in Phys. Rev. D 95, 054018 (2017) and introduce several additional refinements in the calculation.

Motivated by the recent observation of lepton universality violation in the flavor changing charged current transitions $b\to cl{\overline{\nu }}_l$, we intend to scrutinize the lepton nonuniversality effects in rare semileptonic $B$ meson decays involving the quark-level transitions $b\to ul{\overline{\nu }}_l$. In this regard, we envisage the model-independent approach and consider the generalized effective Lagrangian in the presence of new physics and constrain the new parameters by using the experimental branching fractions of $B_u^{+}\to l^{+}{\nu }_l$ and $B^{-}\to {\pi }^0{\mu }^{-}{\overline{\nu }}_{\mu }$ processes, in which $l=e$, $\mu$, $\tau$. We then estimate the branching ratios and forward-backward asymmetries of $B_{(s)}\to P(V)l{\overline{\nu }}_l$ processes, in which $P(=K,\pi ,{\eta }^{(\prime )})$ denotes the pseudoscalar meson and $V(=K^{*},\rho )$ is the vector meson. We also find out various lepton nonuniversality parameters in these processes in the presence of new physics.

We investigate the phenomenology of QCD axions and axionlike particles in a scenario with two eras of inflation. In particular, we describe the possible solutions for the QCD axion field equation after the second inflation and reheating. We calculate the dilution numerically for QCD axions and give an analytic approximation for axionlike particles. While it has been realized before that such a scenario can dilute the axion energy density and open up the parameter space for the axion decay constant $f_A$, we find that even a small increase in the relative QCD axion energy density is possible.

The relaxion mechanism provides a potentially elegant solution to the hierarchy problem without resorting to anthropic or other fine-tuning arguments. This mechanism introduces an axion-like field, dubbed the relaxion, whose expectation value determines the electroweak hierarchy as well as the QCD strong $CP$-violating $\overline{\theta }$ parameter. During an inflationary period, the Higgs mass squared is selected to be negative and hierarchically small in a theory which is consistent with ’t Hooft’s technical naturalness criteria. However, in the original model proposed by Graham, Kaplan, and Rajendran [Phys. Rev. Lett. 115, 221801 (2015)], the relaxion does not solve the strong $CP$ problem, and in fact contributes to it, as the coupling of the relaxion to the Higgs field and the introduction of a linear potential for the relaxion produces large strong $CP$ violation. We resolve this tension by considering inflation with a Hubble scale which is above the QCD scale but below the weak scale, and estimating the Hubble temperature dependence of the axion mass. The relaxion potential is thus very different during inflation than it is today. We find that provided the inflationary Hubble scale is between the weak scale and about 3 GeV, the relaxion resolves the hierarchy, strong $CP$, and dark matter problems in a way that is technically natural.

Encouraged by the recent discovery of the ${\mathrm{\Xi }}_{cc}$ baryon, we investigate two-body nonleptonic weak decays of doubly charmed, ${\mathrm{\Xi }}_{cc}$, baryons. We calculate the branching ratios for Cabibbo-Kobayashi-Maskawa–favored and–suppressed modes in factorization and pole model approaches. The preliminary estimates of nonfactorizable W-exchange contributions are obtained using the pole model. We find that the W-exchange contributions to ${\mathrm{\Xi }}_{cc}$ decays, being sizable, cannot be ignored.

Using a sample of $448.1\times {10}^6\psi (3686)$ events collected with the BESIII detector, a search for the isospin violating decay ${\eta }_c\to {\pi }^{+}{\pi }^{-}{\pi }^0$ via $\psi (3686)\to \gamma {\eta }_c$ is presented. No signal is observed, and the upper limit on $\mathcal{B}(\psi (3686)\to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to {\pi }^{+}{\pi }^{-}{\pi }^0)$ is determined to be $1.6\times {10}^{-6}$ at the 90% confidence level. In addition, a search for $\eta (1405)\to f_0(980){\pi }^0$ in $\psi (3686)$ radiative decays is performed. No signal is observed, and the branching fraction $\mathcal{B}(\psi (3686)\to \gamma \eta (1405))\times \mathcal{B}(\eta (1405)\to f_0(980){\pi }^0)\times \mathcal{B}(f_0(980)\to {\pi }^{+}{\pi }^{-})$ is calculated to be less than $5.0\times {10}^{-7}$ at the 90% confidence level.

We introduce recursive jigsaw reconstruction, a technique for analyzing reconstructed particle interactions in the presence of kinematic and combinatoric unknowns associated with unmeasured and indistinguishable particles, respectively. By factorizing missing information according to decays and rest frames of intermediate particles, an interchangeable and configurable set of jigsaw rules, algorithms for resolving these unknowns, are applied to approximately reconstruct decays with arbitrarily many particles, in their entirety. That the recursive jigsaw reconstruction approach can be used to analyze any event topology of interest, with any number of ambiguities, is demonstrated through twelve different simulated LHC physics examples. These include the production and decay of $W$, $Z$, Higgs bosons, and supersymmetric particles including gluinos, stop quarks, charginos, and neutralinos.

We derive a positivity bound on the right-chiral tensor coupling $\mathrm{Im}{g}_R$ in polarized top quark decay by analyzing the angular decay distribution of the three-body polarized top quark decay $t(\uparrow )\to b+{\ell }^{+}+{\nu }_{\ell }$ in next-to-leading order QCD. We obtain the bound $-0.0420\le \mathrm{Im}{g}_R\le 0.0420$.

We discuss the entropy carried by a quark-antiquark pair, in particular across the deconfinement transition. We therefore rely on a self-consistent solution to Einstein-Maxwell-dilaton gravity, capable of mimicking essential features of QCD. In particular we introduce a novel model that still captures well the QCD confinement and deconfinement phases, while allowing the introduction of a temperature in a phase which resembles the confined phase, this thanks to it being dual to a small black hole. We pay due attention to some subtleties of such a model. We confirm the lattice picture of a strong build-up of thermal entropy towards the critical temperature $T_c$, both coming from below or above $T_c$. We also include a chemical potential, confirming this entropic picture and we consider its effect on the speed of sound. Moreover, the temperature dependent confinement phase from the holography side allows us to find a string tension that does not vanish at $T_c$, a finding also supported by lattice QCD.

We consider a multistring configuration that provides a new way to compute the expectation value of the Polyakov loop in a five-dimensional framework known as AdS/QCD. The obtained results are in reasonably good agreement with those obtained by lattice simulations for pure $SU(3)$ gauge theory and also by the usual single string configuration.

It is generically believed that higher-order curvature corrections to the Einstein-Hilbert action might cure the curvature singularities that plague general relativity. Here we consider Einstein-scalar-Gauss-Bonnet gravity, the only four-dimensional, ghost-free theory with quadratic curvature terms. For any choice of the coupling function and of the scalar potential, we show that the theory does not allow for bouncing solutions in the flat and open Friedmann universe. For the case of a closed universe, using a reverse-engineering method, we explicitly provide a bouncing solution which is nevertheless linearly unstable in the scalar gravitational sector. Moreover, we show that the expanding, singularity-free, early-time cosmologies allowed in the theory are unstable. These results rely only on analyticity and finiteness of cosmological variables at early times.

The detection of gravitational waves (GWs) from black hole (BH) mergers provides an inroad toward probing the interior of astrophysical BHs. The general-relativistic description of the BH interior is that of empty spacetime with a (possibly) singular core. Recently, however, the hypothesis that the BH interior does not exist has been gaining traction, as it provides a means for resolving the BH information-loss problem. Here, we propose a simple method for answering the following question: Does the BH interior exist and, if so, does it contain some distribution of matter or is it mostly empty? Our proposal is premised on the idea that, similar to the case of relativistic, ultracompact stars, any BH-like object whose interior has some matter distribution should support fluid modes in addition to the conventional spacetime modes. In particular, the Coriolis-induced Rossby (r-) modes, whose spectrum is mostly insensitive to the composition of the interior matter, should be a universal feature of such BH-like objects. In fact, the frequency and damping time of these modes are determined by only the object’s mass and speed of rotation. The r-modes oscillate at a lower frequency, decay at a slower rate, and produce weaker GWs than do the spacetime modes. Hence, they imprint a model-insensitive signature of a nonempty interior in the GW spectrum resulting from a BH merger. We find that future GW detectors, such as Advanced LIGO with its design sensitivity, have the potential of detecting such r-modes if the amount of GWs leaking out quantum mechanically from the interior of a BH-like object is sufficiently large.

In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic equation of state (EoS) $p=\omega \rho$, in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form $\xi ={\xi }_0{\rho }^{1/2}$. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, $c_b$. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for $\omega$, ${\xi }_0$, $c_b$ accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions $dS/dt>0$ (growth of the entropy) and $d^{2}S/d{t}^2<0$ (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations.

Using electromagnetism to study analogue space-times is tantamount to considering consistency conditions for when a given (meta-) material would provide an analogue space-time model or—vice versa—characterizing which given metric could be modeled with a (meta-) material. While the consistency conditions themselves are by now well known and studied, the form the metric takes once they are satisfied is not. This question is mostly easily answered by keeping the formalisms of the two research fields here in contact as close to each other as possible. While fully covariant formulations of the electrodynamics of media have been around for a long while, they are usually abandoned for ($3+1$)- or six-dimensional formalisms. Here we use the fully unified and fully covariant approach. This enables us even to generalize the consistency conditions for the existence of an effective metric to arbitrary background metrics beyond flat space-time electrodynamics. We also show how the familiar matrices for permittivity $\epsilon$, permeability ${\mu }^{-1}$, and magnetoelectric effects $\zeta$ can be seen as the three independent pieces of the Bel decomposition for the constitutive tensor $Z^{abcd}$, i.e., the components of an orthogonal decomposition with respect to a given observer with four-velocity $V^a$. Finally, we use the Moore-Penrose pseudoinverse and the closely related pseudodeterminant to then gain the desired reconstruction of the effective metric in terms of the permittivity tensor ${\epsilon }^{ab}$, the permeability tensor ${[{\mu }^{-1}]}^{ab}$, and the magnetoelectric tensor ${\zeta }^{ab}$, as an explicit function $g_{\mathrm{eff}}(\epsilon ,{\mu }^{-1},\zeta )$.

We investigate whether effective field theory (EFT) approaches, which have been useful in examining inflation and dark energy, can also be used to establish a systematic approach to inflationary reheating. We consider two methods. First, we extend Weinberg’s background EFT to the end of inflation and reheating. We establish when parametric resonance and decay of the inflaton occurs, but also find intrinsic theoretical limitations, which make it difficult to capture some reheating models. This motivates us to next consider Cheung et al.’s EFT approach, which instead focuses on perturbations and the symmetry breaking induced by the cosmological background. Adapting the latter approach to reheating implies some new and important differences compared to the EFT of inflation. In particular, there are new hierarchical scales, and we must account for inflaton oscillations during reheating, which lead to discrete symmetry breaking. Guided by the fundamental symmetries, we construct the EFT of reheating, and as an example of its usefulness we establish a new class of reheating models and the corresponding predictions for gravity wave observations. In this paper we primarily focus on the first stages of preheating. We conclude by discussing challenges for the approach and future directions. This paper builds on ideas first proposed in the paper [O. Ozsoy, G. Sengor, K. Sinha, and S. Watson, arXiv:1507.06651.].

Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the $\sim 20–100M_{\odot }$ mass range. PBH binaries were recently suggested as the possible source of LIGO’s first detections. In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries. We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations. We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger. Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries. We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to significantly affect the eccentricity of typical PBH binaries. We also revisit the PBH-binary merger rate resulting from gravitational capture in present-day halos, accounting for Poisson fluctuations. If binaries formed in the early Universe survive to the present time, as suggested by our analytic estimates, they dominate the total PBH merger rate. Moreover, this merger rate would be orders of magnitude larger than LIGO’s current upper limits if PBHs make a significant fraction of the dark matter. As a consequence, LIGO would constrain $\sim 10–300M_{\odot }$ PBHs to constitute no more than $\sim 1\%$ of the dark matter. To make this conclusion fully robust, though, numerical study of several complex astrophysical processes—such as the formation of the first PBH halos and how they may affect PBH binaries, as well as the accretion of gas onto an extremely eccentric binary—is needed.

Hitomi observations of Perseus with the Soft X-ray Spectrometer (SXS) provide a high-resolution look at the 3.5 keV feature reported by multiple groups in the Perseus cluster. The Hitomi spectrum—which involves the sum of diffuse cluster emission and the pointlike central active galactic nucleus (AGN)—does not show any excess at $E\sim 3.5\mathrm{keV}$, giving an apparent inconsistency with previous observations of excess diffuse emission. We point out that 2009 Chandra data reveals a strong dip in the AGN spectrum at $E=(3.54\pm 0.02)\mathrm{keV}$ (cluster frame)—the identical energy to the diffuse excess observed by XMM-Newton. Scaling this dip to the 2016 AGN luminosity and adding it to the diffuse XMM-Newton excess, this predicts an overall dip in the SXS field of view of $(-5.9\pm 4.4)\times {10}^{-6}\mathrm{ph}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ at $E=3.54\mathrm{keV}$—a precise match to the Hitomi data when broadened by the dark matter virial velocity. We describe models of fluorescent dark matter that can reproduce this physics, in which dark matter absorbs and then reemits 3.5 keV photons emitted from the central AGN.

We detail the calculation of two-loop all-plus-helicity amplitudes for pure Yang-Mills theory. The four-dimensional unitarity methods and augmented recursion techniques we have developed, together with a knowledge of the singular structure of the amplitudes, allow us to compute these in compact analytic forms. Specifically we present the computation and analytic results for the six- and seven-gluon leading color two-loop amplitudes, these being the first QCD two-loop amplitudes beyond five points.

Nonhelical tracks are the smoking gun signature of charged and/or colored quirks, which are pairs of particles bound by a new, long-range confining force. We propose a method to efficiently search for these nonhelical tracks at the LHC, without the need to fit their trajectories. We show that the hits corresponding to quirky trajectories can be selected efficiently by searching for coplanar hits in the inner layers of the ATLAS and CMS trackers, even in the presence of on average 50 pile-up vertices. We further argue that backgrounds from photon conversions and unassociated pile-up hits can be removed almost entirely, while maintaining a signal reconstruction efficiency as high as $\sim 70\%$. With the $300{\mathrm{fb}}^{-1}$ dataset, this implies a discovery potential for string tension between 100 eV and 30 keV, and colored (electroweak charged) quirks as heavy as 1600 (650) GeV may be discovered.