The effect of the anomalous magnetic moment (AMM) on the chiral restoration is investigated at zero temperature in the strong magnetic fields with the vacuum magnetic regularization scheme. It is shown that the chiral restoration diagram sensitively depends on the AMM in the ultrastrong magnetic fields. In our work, the parametrization of AMM is employed as proportional to the square of the chiral condensate. The critical chemical potential is found to decrease linearly by the increasing coefficient in the AMM scale. At a smaller scale of the AMM, the critical chemical potential could go down and then grow up as the magnetic field increases. But at a larger scale, the magnetic catalysis on the critical chemical potential would not happen anymore.

Very recently, it was pointed out that when basic ideas of the swampland program are combined with the cosmological hierarchy problem (i.e., the smallness of the dark energy in Planck units) and together are confronted to experiment lead to the prediction of the existence of a single extra-dimension (dubbed the dark dimension) with characteristic length-scale in the micron range. We propose a feasible test procedure to probe the dark dimension using the highest energy cosmic rays.

We discuss the experimental reach of the Frascati PADME experiment in searching for new light bosons via their resonant production in positron annihilation on fixed target atomic electrons. A scan in the mass range around 17 MeV will thoroughly probe the particle physics interpretation of the anomaly observed by the ATOMKI nuclear physics experiment. In particular, for the case of a spin-1 boson, the viable parameter space can be fully covered in a few months of data taking.

We perform perturbative computations in a lattice gauge theory with a conformal measure that is quadratic in a noncompact Abelian gauge field and is nonlocal, as inspired by the induced gauge action in massless ${\mathrm{QED}}_3$. In a previous work, we showed that coupling fermion sources to the gauge model led to nontrivial conformal data in the correlation functions of fermion bilinears that are functions of charge $q$ of the fermion. In this paper, we compute such gauge invariant fermionic observables to order $q^2$ in lattice perturbation theory with the same conformal measure. We reproduce the expectations for scalar anomalous dimension from previous estimates in dimensional regularization. We address the issue of the lattice regulator dependence of the amplitudes of correlation functions.

In-medium masses of the $1S$ and $1P$ states of heavy quarkonia are investigated in the magnetized asymmetric nuclear medium, accounting for the Dirac sea effects, using a combined approach of chiral effective model and QCD sum rule method. Masses are calculated from the in-medium scalar and twist-2 gluon condensates, calculated within the chiral model. The gluon condensate is simulated through the scalar dilaton field, $\chi$ introduced in the model through a scale-invariance breaking logarithmic potential. Contribution of the Dirac sea is incorporated through the nucleonic tadpole diagrams. Treating the scalar fields as classical, the dilaton field, $\chi$, the isoscalar nonstrange $\sigma (\sim (⟨\overline{u}u⟩+⟨\overline{d}d⟩))$, strange $\zeta (\sim ⟨\overline{s}s⟩)$ and isovector $\delta (\sim (⟨\overline{u}u⟩-⟨\overline{d}d⟩))$ fields, are obtained by solving their coupled equations of motion as derived from the chiral model Lagrangian. The effects of magnetic field are incorporated through the Dirac sea as well as the Landau energy levels of the protons, and the anomalous magnetic moments of the nucleons. The scalar fields modify appreciably with magnetic field due to the Dirac sea contribution. In-medium masses of the charmonium and bottomonium ground states are observed to have significant modifications with magnetic field due to the effects of (inverse) magnetic catalysis. In presence of an external magnetic field, there is mixing between the longitudinal component of the vector and the pseudoscalar mesons (PV mixing) in both quarkonia sectors, leading to a rise (drop) of the masses of $J/{\psi }^{||}({\eta }_c)$ and ${\mathrm{\Upsilon }}^{||}(1S)({\eta }_b)$ states. These might show in the experimental observables, e.g., the dilepton spectra in the noncentral, ultrarelativistic heavy ion collision experiments at RHIC and LHC, where the produced magnetic field is huge.

Two isosinglet hadron states $X_0(2900)$ and $X_1(2900)$ with $J=0$ and 1, respectively, discovered by the LHCb collaboration in 2020, are identified as molecular bound states of ${\overline{D}}^{*}{K}^{*}$. Recently two structures $T_{cs0}^a(2900{)}^0$ and $T_{cs0}^a(2900{)}^{++}$ have been observed at the hadron spectra, and one would suspect if they also are molecular states of $D^{*}$ and $K^{*}$. As long as they are of the molecular structures of $D^{*}{K}^{*}$, the hadron states must be in an isovector, namely $T_{cs0}^a(2900{)}^0$ and $T_{cs0}^a(2900{)}^{++}$ are $I_3=-1$, 1 components of the isovector. If it is the case, then the corresponding $T_{cs0}^a(2900{)}^{+}$ of $I=1,I_3=0$, and $T_{cs0}^{\prime a}(2900{)}^{+}$ of $I=0,I_3=0$ so far have evaded experimental observation, but should be found by the future experiments. To testify this ansatz, in this paper we study the possible molecular structures of ${\overline{D}}^{*}{K}^{*}$ and $D^{*}{K}^{*}$ within the Bethe-Salpeter framework. With reasonable input parameters it is found that ${\overline{D}}^{*}{K}^{*}$ isoscalar systems with $J^P=0^{+}$ and $1^{+}$ have solutions. The result supports the ansatz of $X_0(2900)$ and $X_1(2900)$ being molecular states of ${\overline{D}}^{*}{K}^{*}$. Whereas for the system of $D^{*}{K}^{*}$ with $I=1$ the corresponding Bethe-Salpeter equation has no solution. Thus we can draw a clear conclusion that $T_{cs0}^a(2900{)}^0$ and $T_{cs0}^a(2900{)}^{++}$ should not be bound states of $D^{*}$ and $K^{*}$. The two structures observed by the LHCb collaboration may be caused by dynamics, such as the well-recognized triangle anomalies or other mechanisms.

Distinct approaches for the treatment of single-photon production in neutrino neutral-current interactions with hadrons at low and intermediate energies have been proposed over the last decades, mainly motivated by the fact that this process is one of the main backgrounds in ${\nu }_{\mu }\to {\nu }_e$ oscillation experiments. Such approaches disregard the contribution of the Pomeron ($\mathbb{P}$) exchange, which becomes dominant at high energies. In this paper, the dipole formalism is extended for the exclusive photon production in the $Z^0$-proton interactions at high energies and the contribution associated with the Pomeron exchange is estimated. Results for the squared transverse momentum distribution and total cross section are presented considering different models for the dipole-proton scattering amplitude, which imply a steep increase of the cross section with the energy.

The gauge singlet right-handed neutrinos (RHNs) are essential fields in several neutrino mass models that explain the observed eV scale neutrino mass. We assume RHN field to be present in the vicinity of the electroweak scale and all the other possible beyond the Standard Model fields arise at high energy scale $\ge \mathrm{\Lambda }$. In this scenario, the beyond the Standard Model physics can be described using effective field theory (EFT) where the set of canonical degrees of freedoms consists of both RHN and SM fields. EFT of this kind is usually dubbed as $N_R$-EFT. We systematically construct relevant operators that can arise at dimension five and six while respecting underlying symmetry. To quantify the phenomenological implication of these EFT operators we calculate different couplings that involve RHN fields. We discuss the constraints on these EFT operators coming from different energy and precision frontier experiments. For $pp$, $e^{-}p$ and $e^{+}{e}^{-}$ colliders, we identify various channels which crucially depends on these operators. We analytically evaluate the decay widths of RHN considering all relevant operators and highlight the differences that arise because of the EFT framework. Based upon the signal cross section we propose different multilepton channels to search for the RHN at 14 TeV LHC as well as future particle colliders.

Fuzzy dark matter is an exciting alternative to the standard cold dark matter paradigm, reproducing its large scale predictions, while solving most of the existing tension with small scale observations. These models postulate that dark matter is constituted by light bosons and predict the condensation of a solitonic core—also known as boson star, supported by wave pressure—at the center of halos. However, solitons which host a parasitic supermassive black hole are doomed to be swallowed by their guest. It is thus crucial to understand in detail the accretion process. In this work, we use numerical relativity to self-consistently solve the problem of accretion of a boson star by a central black hole, in spherical symmetry. We identify three stages in the process, a boson quake, a catastrophic stage and a linear phase, as well as a general accurate expression for the lifetime of a boson star with an endoparasitic black hole. Lifetimes of these objects can be large enough to allow them to survive until the present time.

Relying on the Penrose process mechanism, we study the possibility of energy extraction from a binary system composed of two extreme electrostatic black holes (BHs) oppositely charged, separated by a strut described by Bonnor’s metric. We determined and plotted the generalized ergosphere that surrounds only one of the BHs. We demonstrate the existence of nonclosed orbits of negative energy outside the event horizon; these orbits allow the possibility of energy extraction by particle disintegration from a system described by the Bonnor’s metric. We prove that the extraction process can occur when a charged test particle and the BH have opposite charges; also, we analyze the efficiency of the process.

We implement advanced Riemann solvers, Harten-Lax-van Leer contact and Harten-Lax-van Leer discontinuities [A. Mignone and G. Bodo, Mon. Not. R. Astron. Soc. 364, 126 (2005).; A. Mignone et al., Mon. Not. R. Astron. Soc. 393, 1141 (2009).] together with an advanced constrained transport scheme [T. A. Gardiner and J. M. Stone, J. Comput. Phys. 227, 4123 (2008).] in a numerical-relativity neutrino-radiation magnetohydrodynamics code. We validate our implementation by performing a series of one- and multi- dimensional test problems for relativistic hydrodynamics and magnetohydrodynamics in both Minkowski spacetime and a static black hole spacetime. We find that the numerical solutions with the advanced Riemann solvers are more accurate than those with the Harten-Lax-van Leer-Einfeldt (HLLE) solver [L. Del Zanna et al., Astron. Astrophys. 400, 397 (2003).] which was originally implemented in our code. As an application to numerical relativity, we simulate an asymmetric binary neutron star merger leading to a short-lived massive neutron star both with and without magnetic fields. We find that the lifetime of the rotating massive neutron star formed after the merger and also the amount of the tidally-driven dynamical ejecta are overestimated when we employ the diffusive HLLE solver. We also find that the magnetorotational instability is less resolved when we employ the HLLE solver because of the solver’s large numerical diffusivity. This causes a spurious enhancement both of magnetic winding resulting from large scale poloidal magnetic fields and also of the energy of the outflow induced by magnetic pressure.

The modeling of unequal mass binary black hole systems is of high importance to detect and estimate parameters from these systems. Numerical relativity (NR) is well suited to study systems with comparable component masses, $m_1\sim m_2$, whereas small mass ratio (SMR) perturbation theory applies to binaries where $q=m_2/m_1\ll 1$. This work investigates the applicability for NR and SMR as a function of mass ratio for eccentric nonspinning binary black holes. We produce 52 NR simulations with mass ratios between $1:10$ and $1:1$ and initial eccentricities up to 0.8. From these we extract quantities like gravitational wave energy and angular momentum fluxes and periastron advance, and assess their accuracy. To facilitate comparison, we develop tools to map between NR and SMR inspiral evolutions of eccentric binary black holes. We derive post-Newtonian accurate relations between different definitions of eccentricity. Based on these analyses, we introduce a new definition of eccentricity based on the (2,2)-mode of the gravitational radiation, which reduces to the Newtonian definition of eccentricity in the Newtonian limit. From the comparison between NR simulations and SMR results, we quantify the unknown next-to-leading order SMR contributions to the gravitational energy and angular momentum fluxes, and periastron advance. We show that in the comparable mass regime these contributions are subdominant and higher order SMR contributions are negligible.

The kilometer-square array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO, located at 4410 m above sea level with an atmospheric depth of $600\mathrm{g}/{\mathrm{cm}}^2$) can simultaneously measure air shower sizes of both electromagnetic particles and muon contents with high precision for cosmic rays with energies in the knee region. An advantage of the LHAASO experiment is that it can be performed at the maximum depth of air showers of cosmic rays in the knee region. In this study, different methods to reconstruct the cosmic ray energy are investigated, including those based on traditional and combined parameters. The traditional methods based on $N_{\mathrm{size}}$ or ${\rho }_{50}$ to reconstruct the primary energy are dependent on the cosmic ray components. Based on Heitler’s electromagnetic and Matthews’ hadronic shower models, two combined parameters of $N_{e*\mu }$ and $N_{e\mu }$ are proposed. The examination of cosmic ray energy reconstruction methods based on the LHAASO-KM2A detector by combining the parameters of muons and electromagnetic particles, and the simulation results, confirmed the reduction in component dependence and bias of individual components. The dependence of energy reconstruction on hadronic interaction models is also discussed.

We revisit the derivation of the nonlocal collision term in the Boltzmann equation for spin-$1/2$ particles, using both the Wigner-function approach by de Groot, van Leeuwen, and van Weert, and the Kadanoff-Baym equation in $T$-matrix approximation. Contrary to previous calculations, our results maintain full Lorentz covariance of the nonlocal collision term.

We find all the integer charge solutions to the equations for the cancellation of local gauge anomalies in a class of gauge theories that extend the Standard Model (SM) by a gauge group of the form $G\times \mathrm{U}(1)$, where $G$ is an arbitrary semisimple compact Lie group. The SM fermions are assumed to be neutral under $G\times \mathrm{U}(1)$ gauge interactions, while the new fermions transform in nontrivial representations of both the new and the SM gauge groups. Our analysis is valid also when the latter is embedded in an arbitrary semisimple compact Lie group. Theories with this structure have recently been studied as models of composite axions based on accidental symmetries and can provide a field theory resolution to the axion quality problem. We apply our results to cases of phenomenological interest and prove the existence of charge assignments with Peccei-Quinn symmetry protected up to dimension 18.

We investigate the impact of the finite volume and the thermal fluctuations on the critical end point of the QCD phase diagram. To do so, we implement the super statistics framework with gamma, $F$, and log-normal distributions and their relation with the Tsallis nonextensive thermodynamics. We compute an effective thermodynamic potential as a function of the inverse temperature fluctuations and explicit dependence on the system volume. To find an analytic expression for the effective potential, we expand the modified Boltzmann factor by using the equilibrium thermodynamic potential computed in the linear sigma model coupled to quarks. We find that the pseudocritical temperature of transition at vanishing baryon chemical potential is modified by the size of the system being about 7% lower for small volumes. Additionally, the critical end point moves to higher densities and lower temperatures (about 12% in both cases). Interestingly, the results are quantitatively the same when the parameter that models the out-of-equilibrium situation is modified, indicating that the chiral symmetry restoration is robust against the thermal fluctuations in this approximation.

We explore the connection between tree-level Dirac neutrino masses and axion physics in a scenario where the Peccei-Quinn (PQ) symmetry enforces lepton number conservation perturbatively. Requiring that the PQ scale $f_a$ is the only heavy scale to play a role in neutrino mass generation, we are led to the construction of a Kim–Shifman–Vainshtein–Zakharov-type model where Dirac neutrino masses are inversely proportional to $f_a$, provided a real scalar triplet (zero hypercharge) is added to the standard model scalar sector. We analyze this extended scalar sector, focusing on the stabilization of the electroweak vacuum. The contribution of the triplet vacuum expectation value to the $W$ mass may also be responsible for the recent hint of beyond-the-SM physics by the CDF collaboration.

We propose a novel way to search for feebly interacting massive particles, exploiting two properties of systems involving collisions between high energy electrons and intense laser pulses. The first property is that the electron-laser collision results in a large flux of hard photons, as the laser behaves effectively as a thick medium. The second property is that the emitted photons free-stream inside the laser and thus for them the laser behaves effectively as a very thin medium. Combining these two features implies that the electron-intense-laser collision is an apparatus, which can efficiently convert $\mathcal{O}(10\mathrm{GeV})$ electrons to a large flux of hard, collinear photons. The photons are directed onto a solid dump in which feebly interacting massive particles may be produced. With the much smaller backgrounds induced by the photon beam compared to those expected in electron- or proton-beam dump experiments and combined with a relatively shorter dump used here, the sensitivity to short lifetimes is unparalleled. We denote this novel apparatus as “optical dump” or NPOD (new physics search with optical dump). The proposed LUXE experiment at the European XFEL has all the basic required ingredients to realize this experimental concept for the first time. Moreover, the NPOD extension of LUXE is essentially parasitic to the main experiment and thus, practically it does not have any bearing on its main program. We discuss how the NPOD concept can be realized in practice by adding a detector after the last physical dump of the experiment to reconstruct the two-photon decay of a new spin-0 particle. We show that even with a relatively short dump, the search can still be background-free. Remarkably, even with a few days of data taking with a 40 TW laser corresponding to its initial run, LUXE-NPOD will be able to probe an uncharted territory of models with pseudoscalars and scalars. Furthermore, with a 350 TW laser of the main run, LUXE-NPOD will have a unique reach for these models. In particular it can probe natural scalar theories for masses above 100 MeV. We note that the new NPOD concept may be ported to other existing or future facilities worldwide, including, e.g., future lepton colliders.

We propose a pseudo-Nambu-Goldstone boson (pNGB) dark matter (DM) model based on an additional non-Abelian gauge symmetry $SU(2{)}_D$. The gauge symmetry $SU(2{)}_D$ is spontaneously broken to a global custodial symmetry $U(1{)}_V$ via the nonvanishing vacuum expectation values of $SU(2{)}_D$ doublet and triplet scalar fields. Due to the exact global symmetry $U(1{)}_V$, the lightest $U(1{)}_V$ charged particle becomes stable. We assume that the lightest charged particle in the model is the charged complex pNGB, which we regard as DM. It avoids the strong constraints from current DM direct detection experiments due to the property of NGB. We find that the measured energy density of DM can be reproduced when the DM mass is larger than the half of the Higgs mass, where the lower limit generally comes from the constraint of DM invisible decay and the upper limit from DM direct detection experiments depends on the model parameters.

We present the full one-loop supersymmetry-QCD corrections to stop-antistop annihilation into gluons and light quarks within the Minimal Supersymmetric Standard Model including Sommerfeld enhancement effects from the exchange of multiple gluons between the incoming particles. These corrections are important as stop (co)annihilation becomes the dominant contribution to the relic density for scenarios with a small mass difference between the neutralino and the stop which are less constrained by current LHC searches and consistent with the observation of a 125 GeV SM-like Higgs boson. We discuss important technical details of our one-loop, real emission, and resummation calculations where we pay particular attention to the cancellation of infrared divergences and the associated application of the dipole formalism for massive initial scalars. The corrections have been implemented in the dark matter precision tool dm@nlo which allows us to study numerically the impact of these corrections on the annihilation cross section. We find that for the chosen reference scenario the dominant correction comes from the Sommerfeld effect and that the pure NLO correction is below 3%. The inclusion of these radiative corrections is still large enough to decrease the relic density by more than 10% and shift the cosmologically preferred parameter region by a few GeV relative to the standard micromegas result. Therefore, the inclusion of these corrections is mandatory if the experimental errors are taken as upper and lower bounds of the theory value.