The impact of momentum anisotropy of the medium on the heavy quarks (HQs) dynamics has been investigated in a hot QCD medium while considering both collisional and radiative processes within the ambit of the Fokker-Planck approach. The relative orientation of the HQs motion (momentum vector) with respect to the direction of anisotropy is responsible for the character of transport coefficients. Therefore, the drag and diffusion coefficients of the HQs are decomposed, respectively, into two and four components by considering a general tensor basis. The transport coefficients of the HQs are decomposed into two (drag coefficients) and four (diffusion coefficients) components by assuming a general tensor basis. Each component of the drag and diffusion coefficient of the HQs has been analyzed in detail. It is observed that the anisotropy has a significant impact on the transport coefficients of the HQ for both the collisional and the radiational processes. The nuclear suppression factor, $R_{AA}$, has been computed considering the anisotropic medium. It is observed that the momentum anisotropy affects the $R_{AA}$ of the HQs significantly in both elastic and inelastic cases.

We explore the impact of highly excited bound states on the evolution of number densities of new physics particles, specifically dark matter, in the early Universe. Focusing on dipole transitions within perturbative, unbroken gauge theories, we develop an efficient method for including around a million bound state formation and bound-to-bound transition processes. This enables us to examine partial-wave unitarity and accurately describe the freeze-out dynamics down to very low temperatures. In the non-Abelian case, we find that highly excited states can prevent the particles from freezing out, supporting a continuous depletion in the regime consistent with perturbativity and unitarity. We apply our formalism to a simplified dark matter model featuring a colored and electrically charged $t$-channel mediator. Our focus is on the regime of superWIMP production which is commonly characterized by a mediator freeze-out followed by its late decay into dark matter. In contrast, we find that excited states render mediator depletion efficient all the way until its decay, introducing a dependence of the dark matter density on the mediator lifetime as a novel feature. The impact of bound states on the viable dark matter mass can amount to an order of magnitude, relaxing constraints from Lyman-$\alpha$ observations.

Some properties of a neutrino may differ significantly depending on whether it is Dirac or Majorana type. The type is determined by the relative size of Dirac and Majorana masses, which may vary if they arise from an oscillating scalar dark matter. We show that the change can be significant enough to convert the neutrino type between Dirac and Majorana periodically while satisfying constraints on the dark matter. This neutrino type oscillation predicts periodic modulations in the event rates in various neutrino phenomena including the neutrinoless double beta decay. As the energy density and, thus, the oscillation amplitude of the dark matter evolves in the cosmic timescale, the neutrino masses change accordingly, which provides an interesting link between the present-time neutrino physics to the early universe cosmology including the leptogenesis.

We obtain two-dimensional relativistic densities and currents of energy and momentum in a proton at rest. These densities are obtained at surfaces of fixed light front time, which physically corresponds to using an alternative synchronization convention. Mathematically, this is done using tilted light front coordinates, which consist of light front time and ordinary spatial coordinates. In this coordinate system, all 16 components of the energy-momentum tensor (EMT) obtain clear physical interpretations, and the nine Galilean components reproduce results from standard light front coordinates. We find angular modulations in several densities that are absent in the corresponding instant form results, which are explained as optical effects arising from using fixed light front time when motion is present within the target. Additionally, transversely polarized spin-half targets exhibit an energy dipole moment—which evaluates to $-1/4$ for all targets if the Belinfante EMT is used, but which is target dependent and vanishes for pointlike fermions if the asymmetric EMT is instead used.

We revisit some aspects of the stringy approach to dipole-dipole interactions, scattering and entanglement in QCD, using the Nambu-Goto (NG) string, without recourse to holography. We first show that the potential between two static dipoles exchanging closed NG strings is attractive at all separations. Underlining the exchange there is an emergent entropy, that is dominated by the tachyon at large separation, and vanishes at short separation, a measure of the confinement-deconfinement transition. The same tachyon is dominant in the scattering amplitude, as a correlator of two Wilson loops for two fixed dipolelike hadrons separated at large rapidity gap, where the contribution of the world sheet fermions is included. While the tachyon causes the mean string bit density to grow exponentially with the rapidity, the total scattering cross section still satisfies the Froissart bound by quantum shadowing. The stringy scattering exchange also carries an entanglement entropy, that saturates when the bound is reached. For hadrons with varying dipole sizes, the tachyon exchange takes place in hyperbolic space in the conformal limit. The result for the full $S$-matrix is reminiscent of the one from Mueller’s evolved dipole wave function, for the total dipole-dipole cross section in perturbative QCD.

We extract transverse-momentum-dependent feed-down fractions for bottomonium production using a data-driven approach. We use data published by the ATLAS, CMS, and LHCb Collaborations for $\sqrt{s}=7\mathrm{TeV}$ proton-proton collisions. Based on this collected data, we produce fits to the differential cross sections for the production of both $S$- and $P$-wave bottomonium states. Combining these fits with branching ratios for excited state decays from the Particle Data Group, we compute the feed-down fractions for both the $\mathrm{\Upsilon }(1S)$ and $\mathrm{\Upsilon }(2S)$ as a function of transverse momentum. Our results indicate a strong dependence on transverse momentum, which is consistent with prior extractions of the feed-down fractions. When evaluated at the average momentum of the states, we find that approximately 75% of $\mathrm{\Upsilon }(1S)$ and $\mathrm{\Upsilon }(2S)$ states are produced directly. Our results for the transverse-momentum-dependent feed-down fractions are provided in tabulated form so that they can be used by other research groups.

This study investigates the properties of the $T_{\psi \psi }$ tetraquark candidates within a coupled-channels calculation of the $c\overline{c}-c\overline{c}$ system, specifically focusing on the $J^P=0^{\pm }$, $1^{\pm }$, and $2^{\pm }$ sectors. The analysis includes various channels containing a $J/\psi$, ${\psi }^{\prime }$, ${\eta }_c$, and ${\eta }_c^{\prime }$ meson. By searching for poles in the scattering matrix, a total of 29 states in different $J^P$ sectors with masses ranging from 6.1 to $7.6\mathrm{GeV}/{\mathrm{c}}^2$ are identified. The study further investigates the masses, widths, and branching ratios of these states, leading to the identification of two potential candidates for the experimental $T_{\psi \psi }(6200)$ tetraquark, one candidate for $T_{\psi \psi }(6600)$, two for $T_{\psi \psi }(6700)$, four for $T_{\psi \psi }(6900)$, and three for $T_{\psi \psi }(7200)$ tetraquarks. Additionally, the paper discusses strategies to discriminate between different candidates and explores possible detection channels for further $c\overline{c}-c\overline{c}$ states.

We report the results of a search for inelastic scattering of weakly interacting massive particles (WIMPs) off ${}^{127}\mathrm{I}$ nuclei using NaI(Tl) crystals with a data exposure of $97.7\mathrm{kg}·\mathrm{years}$ from the COSINE-100 experiment. The signature of inelastic $\mathrm{WIMP}\text{−}{}^{127}\mathrm{I}$ scattering is a nuclear recoil accompanied by a 57.6 keV $\gamma$-ray from the prompt deexcitation, producing a more energetic signal compared to the typical WIMP nuclear recoil signal. We found no evidence for this inelastic scattering signature and set a 90% confidence level upper limit on the WIMP-proton spin-dependent, inelastic scattering cross section of $1.2\times {10}^{-37}{\mathrm{cm}}^2$ at the WIMP mass $500\mathrm{GeV}/{\mathrm{c}}^2$.

This is the second of two companion papers in which we continue to develop the construction of the doubly heavy pentaquark systems using the gauge/string duality. In this paper, we propose a stringy description of the $Q\overline{Q}qqq$ system in the case of two light flavors. Our goal is to explore the lower-lying Born-Oppenheimer potentials as a function of the separation distance between the heavy quark-antiquark pair. The analysis shows that the ground state Born-Oppenheimer potential is described in terms of both hadro-quarkonia and hadronic molecules. Meanwhile a standard pentaquark configuration, which describes a genuine five-quark interaction, makes the dominant contribution to a higher lying potential. This configuration has an antiquark-diquark-diquark structure $\overline{Q}[qq][Qq]$ for separations larger than 0.1 fm. The latter enables us to establish a relation among the masses of hadrons in the heavy quark limit. To describe the structure of the potentials more clearly, we define some critical separations that are related to the processes of string reconnection, breaking, and junction annihilation. Additionally, we consider the generalized baryon vertices, where more than three strings can meet, and explore their implications for the pentaquark systems.

In this paper, we study tree-level scattering amplitudes of scalar particles in the context of effective field theories. We use tools similar to the soft bootstrap to build an ansatz for cyclically ordered amplitudes and impose the Bern-Carrasco-Johansson (BCJ) relations as a constraint. We obtain a set of BCJ-satisfying amplitudes as solutions to our procedure, which can be thought of as special higher-derivative corrections to SU(N) nonlinear sigma model amplitudes satisfying BCJ relations to arbitrary multiplicity at leading order. The surprising outcome of our analysis is that BCJ conditions on higher-point amplitudes impose constraints on lower-point amplitudes, and they relate coefficients at different orders in the derivative expansion. This shows that BCJ conditions are much more restrictive than soft limit behavior, allowing only for a very small set of solutions.

In this paper we study quantum field theory in impulsive plane wave spacetimes. We first analyze the geodesics and the formation of conjugate planes in these spacetimes. The behaviors of the world function and the van Vleck determinant near conjugate plane are also considered. For the quantum field, we work out the mode functions, their Bogoliubov transformations, and the construction of the Wightman functions. By examining the Wightman function near and on the conjugate plane, we show how the twofold and fourfold singularity structure of the Wightman function arise when crossing this plane. Lastly, we come to the stochastic gravity noise kernel which is also the correlation function of the stress energy tensor of the quantum field. Its explicit form is given in terms of the world function and the van Vleck determinant. We investigate its limits for small and large geodesic distances. The leading divergent term of the noise kernel on the conjugate plane are expressed in terms of derivatives of delta functions. Similar to that of the Wightman functions, we also examine how the singularity structure of the noise kernel near the light cone changes when crossing the conjugate plane.

In this paper, the study of canonical quantization of a free real massive scalar field in the Schwarzschild spacetime is continued. The normalization constants for the eigenfunctions of the corresponding radial equation are calculated, providing the necessary coefficients for the doubly degenerate scatteringlike states that are used in the expansion of the quantum field. It is shown that one can pass to a new type of states such that the spectrum of states with energies larger than the mass of the field splits into two parts. The first part consists of states that resemble properly normalized plane waves far away from the black hole, so they just describe the theory for an observer located in that area. The second part consists of states that live relatively close to the horizon and whose wave functions decrease when one goes away from the black hole. The appearance of the second part of the spectrum, which follows from the initial degeneracy of the scatteringlike states, is a consequence of the topological structure of the Schwarzschild spacetime.

There is compelling evidence that the Universe is undergoing a late phase of accelerated expansion. One of the simplest explanations for this behavior is the presence of dark energy. A plethora of microphysical models for dark energy have been proposed. The hope is that, with the ever increasing precision of cosmological surveys, it will be possible to precisely pin down the model. We show that this is unlikely and that, at best, we will have a phenomenological description for the microphysics of dark energy. Furthermore, we argue that the current phenomenological prescriptions are ill-equipped for shedding light on the fundamental theory of dark energy.

In Q. Vigneron, Non-relativistic regime and topology: Topological term in the Einstein equation, we proposed and motivated a modification of the Einstein equation as a function of the topology of the Universe in the form of a biconnection theory. The new equation features an additional “topological term” related to a second nondynamical reference connection and chosen as a function of the spacetime topology. In the present paper, we analyze the consequences for cosmology of this modification. First, we show that expansion becomes blind to the spatial curvature in this new theory; i.e., the expansion laws do not feature the spatial curvature parameter anymore (i.e., ${\mathrm{\Omega }}_{\ne K}=1,\forall {\mathrm{\Omega }}_K$), while this curvature is still present in the evaluation of distances. Second, we derive the first order perturbations of this homogeneous solution. Two additional gauge invariant variables coming from the reference connection are present compared with general relativity: a scalar and a vector mode, both sourced by the shear of the cosmic fluid. Finally, we confront this model with observations. The differences with the Lambda cold dark matter model are negligible; in particular, the Hubble and curvature tensions are still present. Nevertheless, since the main difference between the two models is the influence of the background spatial curvature on the dynamics, an increased precision on the measure of that parameter might allow us to observationally distinguish them.

Black holes (BHs) traversing a dark matter cloud made out of a self-interacting scalar soliton are slowed down by two complementary effects. At low subsonic speeds, the BH accretes dark matter, and this is the only source of dragging along its motion, if we neglect the backreaction of the cloud’s self-gravity. The situation changes at larger supersonic speeds where a shock appears. This leads to the emergence of an additional friction term, associated with the gravitational and scalar pressure interactions and with the wake behind the moving BH. This is a long distance effect that can be captured by the hydrodynamical regime of the scalar flow far away from the BH. This dynamical friction term has the same form as the celebrated Chandrasekhar collisionless result, albeit with a well-defined Coulomb logarithm and a prefactor that is smaller by a factor $2/3$. The infrared cutoff is naturally provided by the size of the scalar cloud, which is set by the scalar mass and coupling, whilst the ultraviolet behavior corresponds to the distance from the BH where the velocity field is significantly perturbed by the BH, which is determined by pressure effects. As a result, supersonic BHs are slowed down by both the accretion drag and the dynamical friction. This effect will be potentially detectable by future gravitational wave experiments as it influences the phase of the gravitational wave signal from inspiralling binaries.

The accuracy of Bayesian inference can be negatively affected by the use of inaccurate forward models. In the case of gravitational-wave inference, accurate but computationally expensive waveform models are sometimes substituted with faster but approximate ones. The model error introduced by this substitution can be mitigated in various ways, one of which is by interpolating and marginalizing over the error using Gaussian-process regression. However, the use of Gaussian-process regression is limited by the curse of dimensionality, which makes it less effective for analyzing higher-dimensional parameter spaces and longer signal durations. In this work, to address this limitation, we focus on gravitational-wave signals from extreme-mass-ratio inspirals as an example, and propose several significant improvements to the base method: an improved prescription for constructing the training set, graphics processing units-accelerated training algorithms, and a new likelihood that better adapts the base method to the presence of detector noise. Our results suggest that the new method is more viable for the analysis of realistic gravitational-wave data.

We study the electromagnetic radiation by a fermion carrying an electric charge $q$ embedded in a medium rotating with constant angular velocity $\mathbf{\Omega }$ parallel or antiparallel to an external constant magnetic field $\mathit{B}$. We assume that the rotation is “relatively slow”; namely, that the angular velocity $\mathrm{\Omega }$ is much smaller than the inverse magnetic length $\sqrt{qB}$. In practice, such angular velocity can be extremely high. The fermion motion is a superposition of two circular motions: one due to its rigid rotation caused by forces exerted by the medium, another due to the external magnetic field. We derive an exact analytical expression for the spectral rate and the total intensity of this type of synchrotron radiation. Our numerical calculations indicate very high sensitivity of the radiation to the angular velocity of rotation. We investigate its dependence on the sign of electric charge, direction of the magnetic field and the sense of rotation and show that the radiation intensity is strongly enhanced if $q\mathit{B}$ and $\mathbf{\Omega }$ point in the opposite direction and is suppressed otherwise.

We report calculations of a wave-packet amplitude of the two-body scattering $\varphi \varphi \to \mathrm{\Phi }\to \varphi \varphi$, which leads to the measured probability in realistic experiments. We elucidate the decay amplitude of $\mathrm{\Phi }\to \varphi \varphi$ from this. In such an amplitude of wave packets, there are in and out time boundaries for the initial $\mathrm{\Phi }$ and final $\varphi \varphi$ configurations, respectively. In this paper, we prove that the effect of the in time boundary of $\mathrm{\Phi }\to \varphi \varphi$ emerges from $\varphi \varphi \to \mathrm{\Phi }\to \varphi \varphi$ without assuming any time boundary a priori. This effect has been overlooked in the standard plane-wave formulation and can exhibit distinct phenomena in wide areas of science. We confirm the result in different integration orders. The result is also interpreted as a Stokes phenomenon in the Lefschetz-thimble decomposition.

We consider the flavor structure of the $S_1$ leptoquark model and derive conservative constraints on the elements of the left- and right-handed coupling matrices in a number of representative scenarios. We focus on the cases where the muon $g-2$ deviation is explained by real muon couplings to either the top-quark or to the charm-quark or to all up-type quarks. The most significant constraints arise from charged lepton flavor-violating decays of the muon and the $\tau$ lepton and from the $\mu –e$ conversion process. Kaon decays and perturbativity provide further constraints. We find strong constraints on almost all coupling matrix elements, implying a very hierarchical matrix structure, where individual entries must differ by at least four orders of magnitude. The flexiblesusy program was used with appropriate model files incorporating the parametrization of the couplings in the up-type mass diagonal basis. The expressions for the leptonic observables were generated and cross-checked with the help of the NPointFunctions extension of the flexiblesusy program.

We present a detailed theoretical study of nonfactorizable contributions of the charm-quark loop to the amplitude of the $B_s\to \gamma \gamma$ decay. This contribution involves the $B$-meson three-particle Bethe-Salpeter amplitude, $⟨0|\overline{s}(y)G_{\mu \nu }(x)b(0)|{\overline{B}}_s(p)⟩$, for which we take into account constraints from analyticity and continuity. The charming-loop contribution of interest may be described as a correction to the Wilson coefficient $C_{7\gamma }$, $C_{7\gamma }\to C_{7\gamma }(1+\delta C_{7\gamma })$. We calculate an explicit dependence of $\delta C_{7\gamma }$ on the parameter ${\lambda }_{B_s}$. Taking into account all theoretical uncertainties, $\delta C_{7\gamma }$ may be predicted with better than 10% accuracy for any given value of ${\lambda }_{B_s}$. For our benchmark point ${\lambda }_{B_s}=0.45\mathrm{GeV}$, we obtain $\delta C_{7\gamma }=0.045\pm 0.004$. Presently, ${\lambda }_{B_s}$ is not known with high accuracy, but its value is expected to lie in the range $0.3\le {\lambda }_{B_s}(\mathrm{GeV})\le 0.6$. The corresponding range of $\delta C_{7\gamma }$ is found to be $0.02\le \delta C_{7\gamma }\le 0.1$. One therefore expects the correction given by charming loops at the level of at least a few percent.