Motivated by the recent discovery of a charmonium $X(3960)$ in $B$ decays by the LHCb Collaboration, the likely existence of two bound/virtual states (denoted by $X_{s\overline{s}}$ and $X_{q\overline{q}}$) below the $D_s^{+}{D}_s^{-}$ and $\overline{D}D$ mass thresholds has been reexamined recently. In this work, we employ the effective Lagrangian approach to calculate their production rates in $B$ decays utilizing triangle diagrams. Our results show that the production yields of $B^{+}\to X_{s\overline{s}}{K}^{+}$ and $B^{+}\to X_{q\overline{q}}{K}^{+}$ are of the order of ${10}^{-4}$, in agreement with the relevant experimental data, which indicates that, if the $D_s^{+}{D}_s^{-}$ and $\overline{D}D$ bound states indeed exist, they can be detected in $B$ decays. Moreover, we calculate the production rate of $B^{+}\to X(3960)K^{+}$ assuming that $X(3960)$ is a resonant state of $D_s^{+}{D}_s^{-}$ and find that it is also of the order of ${10}^{-4}$ but a bit smaller than that as a $D_s^{+}{D}_s^{-}$ bound state.

In this work, we investigate the viability of a light Higgs ($\eta$) scenario in the Georgi-Machacek (GM) model, where we consider all theoretical and experimental constraints such as the perturbativity, vacuum stability, unitarity, electroweak precision tests, the Higgs diphoton and undetermined decays and the Higgs total decay width. In addition, we consider more recent experimental bounds from the searches for doubly charged Higgs bosons in the vector boson fusion channel $H_5^{++}\to W^{+}{W}^{+}$, Drell-Yan production of a neutral Higgs boson $pp\to H_5^0(\gamma \gamma )H_5^{+}$, and for the light scalars at LEP $e^{-}{e}^{+}\to Z\eta$, and at ATLAS and CMS in different final states such as $pp\to \eta \to 2\gamma$ and $pp\to h\to \eta \eta \to 4\gamma ,2\mu 2\tau ,2\mu 2b,2\tau 2b$. By combining these bounds together, we found a parameter space region that is significant as the case of the SM-like Higgs to be the light $CP$-even eigenstate, and this part of the parameter space would be tightened by the coming analyses.

Spin-dependent exotic interactions can be generated by exchanging hypothetical bosons, which were introduced to solve some puzzles in physics. Many precision experiments have been performed to search for such interactions, but no confirmed observations have been made. We propose new experiments to search for the exotic spin-spin interactions that can be mediated by axions or ${\mathrm{Z}}^{\prime }$ bosons. A sensitive functionalized cantilever is utilized as a force sensor to measure the interactions between the spin-polarized electrons in a periodic magnetic source structure and a closed-loop magnetic structure integrated on the cantilever. The source is set to oscillate during data acquisition to modulate the exotic force signal to high harmonics of the oscillating frequency. This helps to suppress the spurious signals at the signal frequency. Different magnetic source structures are designed for different interaction detections. A magnetic stripe structure is designed for ${\mathrm{Z}}^{\prime }$-mediated interactions, which are insensitive to the detection of axion-mediated interactions. This allows us to measure the coupling constant of both if we assume that both exist. With the force sensitivity achievable at low temperatures, the proposed experiments are expected to search for parameter spaces with much smaller coupling constants than the current stringent constraints from micrometer to millimeter range. Specifically, the lower bound of the parameter space will be 7 orders of magnitude lower than the stringent constraints for ${\mathrm{Z}}^{\prime }$-mediated interactions, and an order of magnitude lower for axion-mediated interactions, at the interaction range of $10\mathrm{\mu }\mathrm{m}$.

Lattice gauge theories are fundamental to such distinct fields as particle physics, condensed matter or quantum information theory. The recent progress in the control of artificial quantum systems already allows for studying Abelian lattice gauge theories in tabletop experiments. However, the realization of non-Abelian models remains challenging. Here, we employ a coherent quantum control scheme to enforce non-Abelian gauge invariance, and discuss this idea in detail for a one-dimensional SU(2) lattice gauge system. We comment on how to extend our scheme to other non-Abelian gauge symmetries and higher spatial dimensions. Because of its wide applicability, the presented coherent control scheme provides a promising route for the quantum simulation of non-Abelian lattice gauge theories.

We calculate azimuthal asymmetries in back-to-back production of $J/\psi$ and a photon in electron-proton scattering process at the future electron-ion collider using the transverse momentum dependent parton distribution (TMD) factorization framework. We consider the cases where the proton is unpolarized or transversely polarized. For the formation of $J/\psi$, nonrelativistic QCD is used. We find that the cross section gets contributions from only one color octet state. As a result, the azimuthal modulations become independent of the long-distance matrix elements, and thus can be used to probe, in particular the gluon TMDs which are dominant in this kinematics. We show estimates of the upper bounds of different azimuthal asymmetries using the positivity bounds on TMDs. In addition, we show an estimate of asymmetries using the Gaussian parametrization of the TMDs.

Generalized parton distributions (GPDs) are important nonperturbative functions that provide tomographic images of partonic structures of hadrons. We introduce a type of exclusive processes, to be referred to as single diffractive hard exclusive processes (SDHEPs). We discuss the necessary and sufficient conditions for SDHEPs to be factorized into GPDs. We demonstrate that the SDHEP is not only sufficiently generic to cover all known processes for extracting GPDs, but is also well motivated for the search of new processes for the study of GPDs. We examine the sensitivity of the SDHEP to the parton momentum fraction $x$ dependence of GPDs.

Very recently, the LHCb Collaboration reported the first observation of the hidden-charm pentaquark with strangeness, $P_{\psi s}^{\mathrm{\Lambda }}(4338{)}^0$. Considering this state is very close to the ${\mathrm{\Xi }}_c^0{\overline{D}}^0$ and ${\mathrm{\Xi }}_c^{+}{D}^{-}$ thresholds, we explore the possible bias of the Breit-Wigner parametrization, with emphasis on the effect of its coupling to the double thresholds ${\mathrm{\Xi }}_c^0{\overline{D}}^0$ and ${\mathrm{\Xi }}_c^{+}{D}^{-}$. We first use a qualitative picture based on the “uniformization” of the Riemann surface of the two-channel system to understand the positions of the enhancement. Then we use the Lippmann-Schwinger equation formalism (equivalent to the $K$-matrix parametrization) with two models, the zero-range model and the Flatté model to investigate the $J/\psi \mathrm{\Lambda }$ line shapes. Our results show that the nominal peak of the $P_{\psi s}^{\mathrm{\Lambda }}(4338{)}^0$ could arise either from the pole well above the ${\mathrm{\Xi }}_c^{+}{D}^{-}$ threshold on the $(-,+)$ sheet or from the pole well below the ${\mathrm{\Xi }}_c^0{\overline{D}}^0$ threshold on the $(-,-)$ sheet in the two-channel system. Using the Breit-Wigner distribution to depict the above two line shapes could be misleading. We also find a novel type of line shapes with the enhancement constrained by the threshold difference. We urge the LHCb Collaboration to perform the refined experimental analysis considering the unitarity and analyticity, e.g., using the $K$-matrix parametrization. As a by-product, we obtain that the ratio of the isospin violating decay ${\mathrm{\Gamma }}_{P_{\psi s}^{\mathrm{\Lambda }}\to J/\psi \mathrm{\Sigma }}/{\mathrm{\Gamma }}_{P_{\psi s}^{\mathrm{\Lambda }}\to J/\psi \mathrm{\Lambda }}$ could be up to 10%.

We present an analysis of the most precise set of Hadron-Electron Ring Accelerator (HERA) data within the color dipole formalism, by using an analytical gluon density, based on the double-logarithm approximation of the Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) equations in the asymptotic limit of the scaling variable, $\sigma =\log (1/x)\log (\log (Q^2/Q_0^2))\to \infty$. Fits to the data, including charm and bottom quarks, are performed and demonstrate the efficiency of the model in describing the reduced cross section, ${\sigma }_r$, in the wide range $Q^2:(1.5,500){\mathrm{GeV}}^2$ for two dipole models including parton saturation effects. We also give predictions to $F_2^{c\overline{c}}$, $F_2^{b\overline{b}}$ and $F_L$, all describing the data reasonably well in the range $Q^2:(2.5,120){\mathrm{GeV}}^2$. Total cross sections of exclusive photoproduction of $J/\psi$ and $\rho$ are also calculated and successfully compared to HERA data and recent measurements at LHCb.

In the context of canonical quantum gravity, we consider the effects of a nonstandard expression for the gravitational wave function on the evolution of inflationary perturbations. Such an expression and its effects may be generated by a sudden variation in the (nearly constant) inflaton potential. The resulting primordial spectra, up to the leading order, are affected in the short and in the long wavelength regime, where an oscillatory behavior with a non-negligible amplitude is superimposed on the standard semiclassical result. Moreover, a novel, nonperturbative, approach is used to study the evolution. Finally, a simplified application is fully illustrated and commented.

Pauli exclusion principle (PEP) violations induced by space-time noncommutativity, a class of universality for several models of quantum gravity, are investigated by the VIP-2 Lead experiment at the Gran Sasso underground National Laboratory of INFN. The VIP-2 Lead experimental bound on the noncommutative space-time scale $\mathrm{\Lambda }$ excludes $\theta$-Poincaré far above the Planck scale for non anishing “electriclike” components of ${\theta }_{\mu \nu }$, and up to $6.9\times {10}^{-2}$ Planck scales if they are null. Therefore, this new bound represents the tightest one so far provided by atomic transitions tests. This result strongly motivates high sensitivity underground x-ray measurements as critical tests of quantum gravity and of the very microscopic space-time structure.

In this paper, we study codimension two holography in flat spacetimes, based on the idea of the wedge holography. We propose that a region in a $d+1$ dimensional flat spacetime surrounded by two end of the world branes, which are given by $d$ dimensional hyperbolic spaces, is dual to a conformal field theory (CFT) on a $d-1$ dimensional sphere. Similarly, we also propose that a $d+1$ dimensional region in the flat spacetime bounded by two $d$ dimensional de Sitter spaces is holographically dual to a CFT on a $d-1$ dimensional sphere. Our calculations of the partition function, holographic entanglement entropy and two point functions, support these duality relations and imply that such CFTs are nonunitary. Finally, we glue these two dualities along null surfaces to realize a codimension two holography for a full Minkowski spacetime and discuss a possible connection to the celestial holography.

We extend previous work on the vacuum energy of a massless scalar field in the presence of singular potentials. We consider a single sphere defined by the so-called $\delta \text{−}{\delta }^{\prime }$ interaction. Contrary to the Dirac $\delta$-potential, we find a nontrivial one-parameter family of potentials such that the regularization procedure gives an unambiguous result for the Casimir self-energy. The procedure employed is based on the zeta function regularization and the cancellation of the heat kernel coefficient $a_2$. The results obtained are in agreement with particular cases, such as the Dirac $\delta$ or Robin and Dirichlet boundary conditions.

We discuss the problem of canonical quantization of a free real massive scalar field in the Schwarzschild spacetime. It is shown that a consistent procedure of canonical quantization of the field can be carried out without taking into account the black hole interior, so that in the resulting theory the canonical commutation relations are satisfied exactly, and the Hamiltonian has the standard form. However, unlike some papers, in which the expansion of the quantum field in spherical harmonics is used, here we use an expansion in scatteringlike states for energies larger than the mass of the field. This reveals a strange property of the resulting quantum field theory—doubling of the quantum states, which look as having the same asymptotic momentum to an observer located far away from the black hole. This purely topological effect cannot be eliminated by moving away from the black hole.

We model vacuum fluctuations in quantum gravity with a scalar field, characterized by a high occupation number, coupled to the metric. The occupation number of the scalar is given by a thermal density matrix, whose form is motivated by fluctuations in the vacuum energy, which have been shown to be conformal near a light-sheet horizon. For the experimental measurement of interest in an interferometer, the size of the energy fluctuations is fixed by the area of a surface bounding the volume of spacetime being interrogated by an interferometer. We compute the interferometer response to these “geontropic” scalar-metric fluctuations, and apply our results to current and future interferometer measurements, such as LIGO and the proposed GQuEST experiment.

We consider a procedure of elimination of cosmological singularities similar to that suggested in the recent paper by Simpson and Visser for the construction of regular black holes. It is shown that by imposing a nonsingular cosmological evolution with a bounce in a flat Friedmann universe filled with a minimally coupled scalar field, we obtain a transition between the standard scalar field and its phantom counterpart. In this case, the potential of the scalar field has a nonanalyticity of the cusp type. This result is also readily reproduced in the case of an anisotropic Bianchi I universe. We have also found a spherically symmetric static solution of the Einstein equations, free of singularities and sustained by a scalar field.

We design a new observable, the expansion rate fluctuation $\eta$, to characterize deviations from the linear relation between redshift and distance in the local universe. We also show how to compress the resulting signal into spherical harmonic coefficients in order to better decipher the structure and symmetries of the anisotropies in the local expansion rate. We apply this analysis scheme to several public catalogs of redshift-independent distances, the Cosmicflows-3 and Pantheon datasets, covering the redshift range $0.01<z<0.05$. The leading anisotropic signal is stored in the dipole. Within the standard cosmological model, it is interpreted as a bulk motion ($307\pm 23\mathrm{km}/\mathrm{s}$) of the entire local volume in a direction aligned at better than 4 degrees with the bulk component of the Local Group (LG) velocity with respect to the cosmic microwave background (CMB). This term alone, however, provides an overly simplistic and inaccurate description of the angular anisotropies of the expansion rate. We find that the quadrupole contribution is non-negligible ($\sim 50\%$ of the anisotropic signal), in fact, statistically significant, and signaling a substantial shearing of gravity in the volume covered by the data. In addition, the 3D structure of the quadrupole is axisymmetric, with the expansion axis aligned along the axis of the dipole. Implications for the determination of the $H_0$ parameter are discussed. We find that Hubble constant estimates may show variation as high as $\mathrm{\Delta }{H}_0=(4.1\pm 1.1)\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ between antipodal directions along the dipole axis. In the case of the Pantheon sample, this systematic difference is reduced to $\mathrm{\Delta }{H}_0=(2.4\pm 1.1)\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ once model-dependent correction for peculiar velocity flows are implemented. Notwithstanding, the axial anisotropy in the general direction of the CMB dipole is still detected. We thus show how to optimally subtract redshift anisotropies from Pantheon data in a fully model-independent way by exploiting the $\eta$ observable. As a result, the value of the best fitting $H_0$ is systematically revised upwards by nearly $0.7\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ (about $2\sigma$) compared to the value deduced from the Hubble diagram using the uncorrected observed redshift. The goodness of fit is also improved.

The temperature measurements, $T$, of the perturbed cosmic microwave background, performed by the cosmic background explorer satellite (COBE), are considered. A dichotomist function, $f=\pm 1$, is defined such that $f=+1$ if $\delta T>0$ and $f=-1$ if $\delta T<0$, where $\delta T$ stands for the fluctuation of $T$. Then, it is assumed that behind the appearance of these fluctuations there is local realism. Under this assumption, some specific Clauser-Horne-Shimony-Holt (CHSH) inequalities are proved for these fluctuation temperatures measured by COBE in the different sky directions. The calculation of these inequalities from the actual temperature measurements shows that these inequalities are not violated. This result cannot be anticipated by calculating the commutators of the cosmic density quantum operators. This must be remarked here since, in the case of a system of two entangled spin $\frac{1}{2}$ particles, its CHSH inequalities violation can be inferred from the nonvanishing value of the corresponding spin measurement commutators. The above nonviolation of the observed cosmic CHSH inequalities is compatible with the existence of local realism behind the cosmic measurement results. Nevertheless, assuming again local realism, some new cosmic CHSH inequalities can be derived for the case of the WMAP measurements whose accuracy is better than the one of the above considered COBE measurements. More specifically, in the WMAP case, some significant cross correlations between the temperature and polarization maps are detected, and the new cosmic CHSH inequalities are the ones built with these cross correlations. Now, the occasional violation of these CHSH inequalities would mean the failure of the assumed local realism in accordance with the quantum origin of the primordial temperature and polarization fluctuations in the framework of standard inflation.

As a promising probe for the new physics beyond the standard model of particle physics in the early Universe, the predictions for the stochastic gravitational wave background from a cosmological first-order phase transition heavily rely on the bubble wall velocity determined by the bubble expansion dynamics. The bubble expansion dynamics is governed by the competition between the driving force from the effective potential difference and the backreaction force from a sum of the thermal force and friction force induced by the temperature jumping and out-of-equilibrium effects across the bubble wall, respectively. In this paper, we propose a hydrodynamic evaluation on this total backreaction force for a nonrunaway steady-state bubble expansion, which, after evaluated at the wall interface, exactly reproduces the pressure difference ${\mathrm{\Delta }}_{\text{wall}}[({\overline{\gamma }}^2-1)w]$ obtained previously from the junction condition of the total energy-momentum tensor at the wall interface, where $w$ is the enthalpy and $\overline{\gamma }\equiv (1-{\overline{v}}^2{)}^{-1/2}$ is the Lorentz factor of the wall-frame fluid velocity $\overline{v}$.

Antimatter cosmic rays are used to probe new phenomena in physics, including dark matter annihilation. We use the cosmic-ray positron fraction spectrum by the Alpha Magnetic Spectrometer, to search for such an annihilation signal in the Galaxy. We focus on dark matter with mass between 5 GeV and 120 GeV, producing high-energy electrons and positrons. In these cosmic-ray energies the interplay of multiple astrophysical sources and phenomena, makes this search highly sensitive to the underlying astrophysical background assumptions. We use a vast public library of astrophysical models for the cosmic-ray positron fraction background, to derive robust upper limits on the dark matter’s annihilation cross section for a number of annihilation channels. This library accounts for different types of cosmic-ray sources and uncertainties on their distribution in space and time. Also, it accounts for uncertainties on those sources’ output, their injected into the interstellar medium cosmic-ray spectra and for uncertainties on cosmic-ray propagation. For any given dark matter particle mass and annihilation channel, upper limits on the annihilation cross section are given by bands that stretch a full order of magnitude in its value. Our work provides weaker limits compared to earlier results, that are however robust to all the relevant astrophysical uncertainties. Between 5 GeV and 15 GeV, we find indications for a possible excess flux of cosmic-ray electrons and positrons. That excess is found for most, but not all of our astrophysical background parameter space, and its significance can vary appreciably. Further scrutiny is necessary to improve the understanding of these lower-energy cosmic rays. Finally, we note that even if an excess signal is found in these energies, the current background uncertainties do not allow us to accurately deduce its underlying particle properties.

Thermal noise in high-reflectivity mirror coatings is a limiting factor in ground-based gravitational wave detectors. Reducing this coating thermal noise improves the sensitivity of detectors and enriches the scientific outcome of observing runs. Crystalline gallium arsenide and aluminum-alloyed gallium arsenide (referred to as AlGaAs) coatings are promising coating candidates for future upgrades of gravitational wave detectors because of their low coating thermal noise. However, AlGaAs-based crystalline coatings may be susceptible to an electro-optic noise induced by fluctuations in an electric field. We investigated the electro-optic effect in an AlGaAs coating by using a Fabry-Perot cavity, and concluded that the noise level is well below the sensitivity of current and planned gravitational-wave detectors.