In the present work, we perform a coupled-channel analysis of $B_{(s)}^{(*)}{\overline{B}}_{(s)}^{(*)}$ systems with the one-boson-exchange potentials. We first study the $I(J^{PC})=1(1^{+-})$ $B{\overline{B}}^{*}/B^{*}{\overline{B}}^{*}$ system to describe the $Z_b(10610)$ and $Z_b(10650)$ particles as molecular states and determine the reasonable range of cutoff parameter $\mathrm{\Lambda }$. Then, other $B_{(s)}^{(*)}{\overline{B}}_{(s)}^{(*)}$ combinations with different quantum numbers are systematically investigated. Some bound states and resonances appear in the isoscalar systems, while only several shallow bound states exist for isovector systems. Far away from the excited conventional $P$-wave bottomium, these predicted states can be easily identified as exotic particles both theoretically and experimentally. Moreover, the ${\eta }_b(nS)/\mathrm{\Upsilon }(nS)$ plus light mesons are the excellent final states to search for the bound states, while the $B{\overline{B}}^{*}+\mathrm{H}.\mathrm{c}.$ and $B^{*}{\overline{B}}^{*}$ channels are suitable for the resonances. We highly recommend that the LHCb and Belle II Collaborations hunt for these bottomoniumlike states in the future.

Conversions between neutrons $n$ and dark matter candidate sterile neutrons $n^{\prime }$ have been proposed as a mechanism for baryon number $\mathcal{B}$ violation. In the case that there is a small mass difference $\mathrm{\Delta }m$ between the $n$ and the $n^{\prime }$ states, oscillations can be induced by compensating for $\mathrm{\Delta }m$ with a magnetic field. A search for such neutron oscillations was performed at the Spallation Neutron Source by looking for anomalous neutron transmission through a strongly absorbing cadmium wafer inside of a 6.6 T magnet. The approach described here saw no regenerated neutrons above background, which provides an improved limit for neutron–sterile neutron transformations for a range of $\mathrm{\Delta }m$ between 0.1 and 1000 neV.

We investigate the evolution of a homogeneous magnetic field within Bianchi-I loop quantum cosmology, in which the big bang singularity is replaced with an anisotropic quantum bounce. Using effective spacetime description, we conduct extensive numerical simulations with randomized initial conditions for two cases: first in the presence of a pure homogeneous magnetic field and then adding a massless scalar field that effectively captures the bounce regime even in the presence of inflationary potentials. For a cigarlike approach to the classical big bang, which is far more prevalent than a pointlike approach, the nonsingular bounce acts as a seesaw mechanism for magnetic field energy density. Because of the seesaw mechanism, the magnetic field energy density gets amplified by several orders of magnitude across the bounce for a small prebounce value of magnetic field energy density, or vice versa. In the presence of the scalar field, the seesaw mechanism is completely replaced by amplification of the magnetic field across the bounce when the initial energy density of the scalar field significantly dominates. When the universe has a pointlike approach to the classical big bang, the seesaw mechanism is absent, and magnetic field energy density experiences amplification or suppression across the nonsingular bounce depending on initial densities.

We study symmetry reductions in the context of Euclidean Chern-Simons gauge theories to obtain lower dimensional field theories. Symmetry reduction in certain gauge theories is a common tool for obtaining explicit soliton solutions. Although pure Chern-Simons theories do not admit solitonic solutions, symmetry reduction still leads to interesting results. We establish relations at the semiclassical regime between pure Chern-Simons theories on $S^3$ and the reduced quantum field theories, based on actions obtained by the symmetry reduction of the Chern-Simons action, spherical symmetry being the prominent one. We also discuss symmetry reductions of Chern-Simons theories on the disk, yielding a topological theory in two dimensions, which signals a curious relationship between symmetry reductions and the boundary conformal field theories. Finally, we study the Chern-Simons-Higgs instantons and show that under certain circumstances, the reduced action can formally be viewed as the action of a supersymmetric quantum mechanical model. We discuss the extent to which the reduced actions have a fermionic nature at the level of the partition function.

In this study, we investigate the decoherence of a spatially superposed electrically neutral spin-$\frac{1}{2}$ particle in the presence of a relativistic quantum electromagnetic field in Minkowski spacetime. We demonstrate that decoherence due to the spin-magnetic field coupling can be categorized into two distinct factors: local decoherence, originating from the two-point correlation functions along each branch of the superposed trajectories, and nonlocal decoherence, which arises from the correlation functions between the two superposed trajectories. These effects are linked to phase damping and amplitude damping. We also show that if the quantum field is prepared in a thermal state, decoherence monotonically increases with the field temperature.

Using an analytic, static, and spherically symmetric metric for a Schwarzschild black hole immersed in a dark matter (DM) halo with the Hernquist-type profile, we derive analytic expressions for the orbital period and precession of eccentric extreme mass ratio inspirals (EMRIs) surrounded by DM halos, and we show how the precession rates decrease and even undergo a prograde-to-retrograde precession transition if the density of DM halo is large enough. The presence of local DM halos also retards the decrease of the semilatus rectum and the eccentricity. The orbital evolution of EMRIs immersed in DM halos is then calculated numerically by considering the combined effects of gravitational radiation reaction, dynamical friction, and accretion. Comparing the number of orbital cycles accumulated over a one-year evolution for EMRIs with and without DM halos, we find that DM halos with compactness as small as ${10}^{-5}$ can be detected. From the mismatch between gravitational waveforms of EMRIs with and without DM halos, we show that EMRIs in galaxies can be used to probe the existence of DM halos and detect the compactness of DM halos as small as ${10}^{-5}$. Employing the Fisher information matrix method, we find that larger compactness and density values of DM halos help to reduce the estimation error of parameters and further break the degeneracy between the parameters.

Fuzzy dark matter is a promising alternative to the standard cold dark matter. It has quite recently been noticed, that they can not only successfully explain the large-scale structure in the Universe, but can also solve problems of position and flux anomalies in galaxy strong lensing systems. In this paper we focus on the perturbation of time delays in strong lensing systems caused by fuzzy dark matter, thus making an important extension of previous works. We select a specific system HS $0810+2554$ for the study of time delay anomalies. Then, based on the nature of the fuzzy dark matter fluctuations, we obtain theoretical relationship between the magnitude of the perturbation caused by fuzzy dark matter, its content in the galaxy, and its de Broglie wavelength ${\lambda }_{\mathrm{dB}}$. It turns out that, the perturbation of strong lensing time delays due to fuzzy dark matter quantified as standard deviation is ${\sigma }_{\mathrm{\Delta }t}\propto {\lambda }_{\mathrm{dB}}^{1.5}$. We also verify our results through simulations. Relatively strong fuzzy dark matter fluctuations in a lensing galaxy make it possible to destroy the topological structure of the lens system and change the arrival order between the saddle point and the minimum point in the time delays surface. Finally, we stress the unique opportunity for studying properties of fuzzy dark matter created by possible precise time delay measurements from strongly lensed transients like fast radio bursts, supernovae or gravitational wave signals.

Exclusive photoproduction of heavy $J/\psi$ meson is performed within the handbag factorization method. The general parton distributions (GPDs) for gluons, which are an essential ingredient here, are constructed using double distribution (DD) representation. The calculated cross section for few sets of gluon GPDs $H_g$ describe fine $J/\psi$ production experimental data from HERA to LHC energies. Based on this approach we estimate $J/\psi$ spin asymmetries determined by $E_g$ and ${\tilde{H}}_g$. The GPDs factorization approach can be employed to analyze heavy vector meson production in electron-proton scattering. Investigations of this reactions at future electron-ion colliders in USA and China can give essential information on gluon GPDs.

In the standard model, the charged lepton-flavor violation (CLFV) processes are forbidden, so the observation of CLFV represents a clear signal of new physics that goes beyond the standard model. In this work, we focus on the CLFV processes $l_j^{-}\to l_i^{-}\gamma$ and $l_j^{-}\to l_i^{-}{l}_i^{-}{l}_i^{+}$ in the left-right supersymmetric standard model (LRSSM). Considering the constraints of the updated experimental data, the numerical results show that the new contributions of $SU{(2)}_R$ gauge interaction and a large number of other new particles, such as the $Z^{\prime }$ boson and double-charged Higgs bosons in LRSSM can make significant contributions to the CLFV processes $l_j^{-}\to l_i^{-}\gamma$ and $l_j^{-}\to l_i^{-}{l}_i^{-}{l}_i^{+}$, which is much different from the ones predicted in other supersymmetry models. This work provides a theoretical base for finding the lepton-flavor violation phenomena in new physics.

We explore the feasibility of using TeV-energy muons to probe lepton-flavor-violating (LFV) processes mediated by an axionlike particle (ALP) $a$ with mass $\mathcal{O}(10\mathrm{GeV})$. We focus on $\mu \tau$ LFV interactions and assume that the ALP is coupled to a dark state $\chi$, which can be either less or more massive than $a$. Such a setup is demonstrated to be consistent with $\chi$ being a candidate for dark matter, in the experimentally relevant regime of parameters. We consider the currently operating NA64-$\mu$ experiment and proposed $\mathrm{FASER}\nu 2$ detector as both the target and the detector for the process $\mu A\to \tau Aa$, where $A$ is the target nucleus. We also show that a possible future active muon fixed-target experiment operating at a 3 TeV muon collider or in its preparatory phase can provide an impressive reach for the LFV process considered, with future $\mathrm{FASER}\nu 2$ data providing a pilot study towards that goal. The implications of the muon anomalous magnetic moment $(g-2{)}_{\mu }$ measurements for the underlying model, in case of a positive signal, are also examined, and a sample UV completion is outlined.

Why does dark matter (DM) live longer than the age of the Universe? Here we study a novel sub-eV scalar DM candidate whose stability is due to the Pauli exclusion of its fermionic decay products. We analyze the stability of the DM condensate against decays, scatterings (i.e., evaporation), and parametric resonance, delineating the viable parameter regions in which DM is cosmologically stable. In a minimal scenario in which the scalar DM decays to a pair of new exotic fermions, we find that scattering can populate an interacting thermal dark sector component to energies far above the DM mass. This self-interacting dark radiation may potentially alleviate the Hubble tensions. Furthermore, our scenario can be probed through precise measurements of the halo-mass function or the masses of dwarf spheroidal galaxies since scattering prevents the DM from becoming too dense. On the other hand, if the lightest neutrino stabilizes the DM, the cosmic neutrino background ($\mathrm{C}\nu \mathrm{B}$) can be significantly altered from the Lambda cold dark matter prediction and thus be probed in the future by $\mathrm{C}\nu \mathrm{B}$ detection experiments.

Portal matter (PM), having both Standard Model (SM) and dark sector charges, can induce kinetic mixing between the $U(1{)}_D$ dark photon and the SM gauge fields at the 1-loop level offering an attractive mechanism by which light ($\lesssim 1\mathrm{GeV}$) thermal dark matter (DM) can interact with visible matter and obtain its observed relic density. In doing so, if the DM is fermionic, the CMB and other astrophysical observations inform us that it must be Majorana/pseudo-Dirac in nature to avoid velocity/temperature-independent $s$-wave annihilation to SM final states. How does this idea fit into a more UV-complete picture also including the SM interactions? There are some reasons to believe that at least a first step along this path may not lie too far away in energy due to the renormalization group equations running of the dark gauge coupling, which for a significant range of parameters, becomes nonperturbative at/before the $\sim 10$’s of TeV energy range. This implies that $U(1{)}_D$ must become embedded in an asymptotically free, non-Abelian group, $G_D$, before this can occur. The breaking of this larger group then produces the masses for the PM and the additional gauge fields associated with $G_D$ then can lead to new interactions between the SM and the dark sector. Following several bottom-up approaches, we have examined a set of distinctive and testable phenomenological features associated with this general setup, based upon a number of simplifying assumptions. Clearly, it behooves us to explore the impact of these specific assumptions on these predictions for the array of possible experimental tests of this class of models. In most past analyses it has been assumed that DM is a vectorlike, complex singlet under the group $G_D$. If this assumption is relaxed, the dark sector must be augmented by additional fermion(s) and the associated scalar fields needed to break the gauge symmetries while generating the needed Majorana-like mass terms for the DM. In this paper, we analyze the simplest extension of this kind wherein the DM lies in a vectorlike doublet of $G_D$, which we take to have the structure $SU(2{)}_I\times U(1{)}_{Y_I}$ as in earlier work, leading to new phenomenological implications. We find, for example, that given the current LHC search constraints on the masses of heavy gauge bosons, the production of these new dark states with large rates is unlikely to occur at colliders unless they are produced singly in $gg$ fusion or their pair production cross sections are resonantly enhanced. We also find that an additional mechanism arises to generate hierarchal neutrino masses in such a setup.

A scotogenic model can radiatively generate the observed neutrino mass, provide a dark matter candidate, and lead to rare lepton flavor-violating processes. We aim to extend the model to establish a potential connection to the quark flavor-related processes within the framework of scotogenesis, enhancing the unexpectedly large branching ratio (BR) of $B^{+}\to K^{+}\nu \overline{\nu }$ observed by the Belle II Collaboration. Meanwhile, the model can address tensions between some experimental measurements and standard model (SM) predictions in flavor physics, such as the muon $g-2$ excess and the higher BR of $B_s\to {\mu }^{-}{\mu }^{+}$. In the model, we introduce the following dark particles: a neutral singlet Dirac-type lepton ($N$); two inert Higgs doublets (${\eta }_{1,2}$), with one carrying a lepton number; a charged singlet dark scalar $({\chi }^{+})$; and a singlet vectorlike up-type dark quark ($T$). The first two entities are responsible for the radiative neutrino mass, and ${\chi }^{+}$ couples to right-handed quarks and leptons and can resolve the tensions existing in muon $g-2$ and $B_s\to {\mu }^{-}{\mu }^{+}$. Furthermore, the BR of $B^{+}\to K^{+}\nu \overline{\nu }$ can be enhanced up to a factor of 2 compared to the SM prediction through the mediations of the dark $T$ and the charged scalars. In addition, we also study the impacts on the $K\to \pi \nu \overline{\nu }$ decays.

We study the spin-dependent in-medium dynamics of quarkonia by using the potential nonrelativistic QCD (pNRQCD) and the open quantum system framework. We consider the pNRQCD Lagrangian valid up to the order $\frac{r}{M^0}=r$ and $\frac{r^0}{M}=\frac{1}{M}$ in the double power counting. By considering the Markovian condition and applying the Wigner transformation upon the diagonal spin components of the quarkonium density matrix with the semiclassical expansion, we systematically derive the Boltzmann transport equation for quarkonia with polarization dependence in the quantum optical limit. Unlike the spin-independent collision terms governed by certain chromoelectric field correlators, new gauge invariant correlators of chromomagnetic fields determine the recombination and dissociation terms with polarization dependence at the order we are working. We also derive a Lindblad equation describing the in-medium transitions between spin-singlet and spin-triplet heavy quark-antiquark pairs in the quantum Brownian motion limit. The Lindblad equation is governed by new transport coefficients defined in terms of the chromomagnetic field correlators. Our formalism is generic and valid for both weakly coupled and strongly coupled quark gluon plasmas. It can be further applied to study spin alignment of vector quarkonia in heavy ion collisions.

A high-precision measurement of the branching fraction of the decay $J/\psi \to p\overline{p}\eta$ is performed using $(10087\pm 44)\times {10}^{6}J/\psi$ events recorded by the BESIII detector at the BEPCII storage ring. The branching fractions of the two decays $J/\psi \to p\overline{p}\eta (\eta \to \gamma \gamma )$ and $J/\psi \to p\overline{p}\eta (\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0)$ are measured individually to be $\mathcal{B}(J/\psi \to p\overline{p}\eta (\eta \to \gamma \gamma ))=(1.480\pm 0.001\pm 0.024)\times {10}^{-3}$ and $\mathcal{B}(J/\psi \to p\overline{p}\eta (\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0))=(1.557\pm 0.003\pm 0.038)\times {10}^{-3}$, where the first uncertainties are statistical and the second systematic. Both results are compatible within their uncorrelated systematic uncertainties. The combined result is $\mathcal{B}(J/\psi \to p\overline{p}\eta )=(1.495\pm 0.001\pm 0.023)\times {10}^{-3}$, where the first uncertainty is the combined statistical uncertainty and the second one the combined systematic uncertainty of both analyses, incorporating correlations between them. In addition, the $p\overline{p}$ threshold region is investigated for a potential threshold enhancement, and no evidence for one is observed.

The ratio of branching fractions $R(D^{*})=\mathcal{B}(\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}(\overline{B}\to D^{*}{\ell }^{-}{\overline{\nu }}_{\ell })$, where $\ell$ is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of $189{\mathrm{fb}}^{-1}$ at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Data is collected at the $\mathrm{\Upsilon }(4\mathrm{S})$ resonance, and one $B$ meson in the $\mathrm{\Upsilon }(4\mathrm{S})\to B\overline{B}$ decay is fully reconstructed in hadronic decay modes. The accompanying signal $B$ meson is reconstructed as $\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau }$ using leptonic $\tau$ decays. The normalization decay, $\overline{B}\to D^{*}{\ell }^{-}{\overline{\nu }}_{\ell }$, produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields $R(D^{*})={0.262}_{-0.039}^{+0.041}(\mathrm{stat}{)}_{-0.032}^{+0.035}(\mathrm{syst})$. This result is consistent with the current world average and with Standard Model predictions.

Measurements of jet cross-section ratios between inclusive bins of jet multiplicity are performed in $140{\mathrm{fb}}^{-1}$ of proton-proton collisions with $\sqrt{s}=13\mathrm{TeV}$ center-of-mass energy, recorded with the ATLAS detector at CERN’s Large Hadron Collider. These ratios are constructed from double-differential cross-section measurements that are made in bins of jet multiplicity and other observables that are sensitive the energy scale and angular distribution of radiation due to the strong interaction in the final state. Additionally, the scalar sum of the two leading jets’ transverse momenta is measured triple differentially, in bins of the third jet’s transverse momentum and of jet multiplicity. These measurements are unfolded to account for acceptance and detector-related effects. The measured distributions are used to construct ratios of the inclusive jet-multiplicity bins, which have been shown to be sensitive to the strong coupling ${\alpha }_{\mathrm{S}}$ while being less sensitive than other observables to systematic uncertainties and parton distribution functions. The measured distributions are compared with state-of-the-art QCD calculations, including next-to-next-to-leading-order predictions for two- and three-jet events. These predictions are generally found to model the data well and perform best in bins with a modest requirement on the third jet’s transverse momentum. Significant differences between data and Monte Carlo predictions are observed in events with large rapidity gaps and invariant masses of the leading jet pair. Studies leading to reduced jet energy scale uncertainties significantly improve the precision of this work and are documented herein.

I explore various scenarios for the phase transition within neutron-star matter. I do so by generating large model-agnostic ensemble using Gaussian processes, both with and without explicit inclusion of first-order phase transitions (FOPTs). The ensemble is conditioned with state-of-the-art astrophysical and theoretical inputs in a fully Bayesian approach. I study how the current data affect the posterior probability of the location and the strength of FOPT. I find that the previously observed peak structure of the sound speed remains stable against inclusion of FOPTs. While the current data cannot differentiate between a smooth crossover and a first-order phase transition, 95% of the total evidence consists of equations of state with some form of phase changes, such as FOPT occurring within or terminating the stable branch of neutron stars, or an indication of a crossover to quark matter.

The Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality in the vacuum state of a relativistic scalar quantum field is revisited by making use of the Hilbert space $\mathcal{H}\otimes {\mathcal{H}}_{AB}$, where $\mathcal{H}$ and ${\mathcal{H}}_{AB}$ stand, respectively, for the Hilbert space of the scalar field and of a generic bipartite quantum mechanical system. The construction of Hermitian, field-dependent, dichotomic operators is devised as well as the Bell-CHSH inequality. Working out the $AB$ part of the inequality, the resulting Bell-CHSH correlation function for the quantum field naturally emerges from unitary Weyl operators. Furthermore, introducing a Jaynes-Cummings type Hamiltonian accounting for the interaction between the scalar field and a pair of qubits, the quantum corrections to the Bell-CHSH inequality in the vacuum state of the scalar field are evaluated till the second order in perturbation theory.

We study the stability of fracton gravity, a variant of linearized gravity where the gauge symmetry is restricted to longitudinal diffeomorphisms. These transformations can be connected to a spacetime generalization of dipole symmetry, hence the tag fracton. We find that fracton gravity features an instability in the spin-1 sector corresponding to solutions with growing amplitude. This dynamical instability can be removed by tuning the couplings of the theory. Nonetheless, the Hamiltonian for the spin-1 modes remains always unbounded from below when evaluated on the classical solutions. We find no other sources of instability in the spin-2 or spin-0 sectors. We analyze in detail the canonical formulation and the constraints arguing that neither auxiliary fields nor gauge-fixing conditions can be employed to remove the problematic vector modes or stabilize them.