We propose the study of the inclusive production of two $\mathrm{\Lambda }$ hyperons or a single $\mathrm{\Lambda }$-particle in association with a jet, featuring high transverse momenta and large separation in rapidity, as a probe channel of the resummation of energy logarithms in the QCD perturbative series. We give predictions, shaped on kinematic ranges typical of CMS and of the backward CASTOR detector, for cross section and azimuthal-correlation moments between the two emitted objects, showing how considering the tag of $\mathrm{\Lambda }$ baryons eases the comparison between theoretical results and experimental data in the phenomenological context of semihard reactions.

We study solutions to the Dirac equation in Minkowski space ${\mathbb{R}}^{1,d+1}$ that transform as $d$-dimensional conformal primary spinors under the Lorentz group $SO(1,d+1)$. Such solutions are parametrized by a point in ${\mathbb{R}}^d$ and a conformal dimension $\mathrm{\Delta }$. The set of wave functions that belong to the principal continuous series, $\mathrm{\Delta }=\frac{d}{2}+i\nu$, with $\nu \ge 0$ and $\nu \in \mathbb{R}$ in the massive and massless cases, respectively, form a complete basis of delta-function normalizable solutions of the Dirac equation. In the massless case, the conformal primary wave functions are related to the wave functions in momentum space by a Mellin transform.

We develop an effective framework for the $\overline{\mu }$ scheme of holonomy corrections motivated by loop quantum gravity for vacuum spherically symmetric space-times. This is done by imposing the areal gauge in the classical theory and then expressing the remaining components of the Ashtekar-Barbero connection in the Hamiltonian constraint in terms of holonomies of physical length ${\ell }_{\mathrm{Pl}}$. The stationary solutions to the effective Hamiltonian constraint can be found exactly, and we give the explicit form of the effective metric in Painlevé-Gullstrand coordinates. This solution has the correct classical limit, the quantum gravity corrections decay rapidly at large distances, and curvature scalars are bounded by the Planck scale, independently of the black hole mass $M$. In addition, the solution is valid for radii $x\ge x_{\min }\sim ({\ell }_{\mathrm{Pl}}^{2}M{)}^{1/3}$ indicating the need for a matter field, with an energy density bounded by the Planck scale, to provide a source for the curvature in the space-time. Finally, for $M\gg m_{\mathrm{Pl}}$, the space-time has an outer and also an inner horizon, within which the expansion for outgoing radial null geodesics becomes positive again. On the other hand, for sufficiently small $M\sim m_{\mathrm{Pl}}$, there are no horizons at all in the effective metric.

We discuss the conditions under which Higgs and confining regimes in gauge theories with fundamental representation matter fields can be sharply distinguished. It is widely believed that these regimes are smoothly connected unless they are distinguished by the realization of global symmetries. However, we show that when a $U(1)$ global symmetry is spontaneously broken in both the confining and Higgs regimes, the two phases can be separated by a phase boundary. The phase transition between the two regimes may be detected by a novel topological vortex order parameter. We first illustrate these ideas by explicit calculations in gauge theories in three spacetime dimensions. Then we show how our analysis generalizes to four dimensions, where it implies that nuclear matter and quark matter are sharply distinct phases of QCD with an approximate $SU(3)$ flavor symmetry.

We present a general framework with which the Schwarzschild-Tangherlini metric of a point particle in arbitrary dimensions can be derived from a scattering amplitude to all orders in the gravitational constant, $G_N$, in covariant gauge (i.e. $R_{\xi }$ gauge) with a generalized de Donder–type gauge function, $G_{\sigma }$. The metric is independent of the covariant gauge parameter $\xi$ and obeys the classical gauge condition $G_{\sigma }=0$. We compute the metric with the generalized gauge choice explicitly to second order in $G_N$ where gravitational self-interactions become important and these results verify the general framework to one-loop order. Interestingly, after generalizing to arbitrary dimension, a logarithmic dependence on the radial coordinate appears in space-time dimension $D=5$.

We address the homogeneous in space and time Gödel-type metrics within the cubic Galileon theory, a particular class of generalized Galileon theories. We check the consistency of such space-times for a physically well-motivated matter content, namely, a perfect fluid and an electromagnetic field. In this scenario, we find that the admissible solutions impose constraints on the constant couplings ($c_i\mathrm{s}$) of the cubic Galileon theory to ensure the consistency. Also, we show the existence of a vacuum completely causal solution.

From a parametrized post-Newtonian (PPN) perspective, we address the question of whether or not the new degrees of freedom represented by the PPN potentials can lead to significant modifications in the dynamics of galaxies in the direction of rendering dark matter obsolete. Here, we focus on the study of rotation curves associated with spherically symmetric configurations. The values for the post-Newtonian parameters, which help us to classify the different metric theories of gravity, are tightly constrained, mainly by Solar System experiments. Such restrictions render the modifications of gravitational effects, with respect to general relativity (GR), to be insignificant, making attempts to find alternative metrical theories rather fruitless. However, in recent years, metric theories characterized by screening mechanisms have become popular, due to the fact that they lead to the possibility of modifications in larger scales than the Solar System while retaining the success of GR on it, allowing for violations of the constraints of the post-Newtonian parameters. In such a context, we consider here two kinds of solutions for field equations: (i) Vacuum solutions (i.e., when no matter fields are present) and (ii) fields in the presence of a polytropic distribution of matter. For case (i), we find that the post-Newtonian corrections do not lead to modifications significant enough to be considered an alternative to the dark matter hypothesis. In case (ii), we find that for a wide range of values for the PPN parameters $\gamma$, $\beta \le 1$, $\xi \ge 0$, ${\alpha }_3$, ${\zeta }_1$, and ${\zeta }_2$, the need for dark matter is unavoidable in order to find flat rotation curves. It is only for theories in which ${\zeta }_3>0$, or $\beta >1$, or $\xi <0$ that some resemblance of flat rotation curves is found. But the latter two require some direct fine-tuning of the screening radius $r_c$, while ${\zeta }_3>0$ implies the most sound modifications. The latter suggests, at least for the models considered, that these are the only theories (consistent with the usual PPN approach) capable of replacing dark matter as a possible explanation for the dynamics of galaxies.

It is well known that the Klein Gordon (KG) equation $\square \mathrm{\Phi }+m^2\mathrm{\Phi }=0$ has tachyonic unstable modes on large scales ($k^2<|m{|}^2$) for $m^2<m_{\mathrm{cr}}^2=0$ in a flat Minkowski spacetime with maximum growth rate ${\mathrm{\Omega }}_F(m)=|m|$ achieved at $k=0$. We investigate these instabilities in a Reissner-Nordström-deSitter (RN-dS) background spacetime with mass $M$, charge $Q$, cosmological constant $\mathrm{\Lambda }>0$ and multiple horizons. By solving the KG equation in the range between the event and cosmological horizons, using tortoise coordinates $r_{*}$, we identify the bound states of the emerging Schrodinger-like Regge-Wheeler equation corresponding to instabilities. We find that the critical value $m_{\mathrm{cr}}$ such that for $m^2<m_{\mathrm{cr}}^2$ bound states and instabilities appear, remains equal to the flat space value $m_{\mathrm{cr}}=0$ for all values of background metric parameters despite the locally negative nature of the Regge-Wheeler potential for $m=0$. However, the growth rate $\mathrm{\Omega }$ of tachyonic instabilities for $m^2<0$ gets significantly reduced compared to the flat case for all parameter values of the background metric ($\mathrm{\Omega }(Q/M,M^2\mathrm{\Lambda },mM)<|m|$). This increased lifetime of tachyonic instabilities is maximal in the case of a near extreme Schwarzschild-deSitter (SdS) black hole where $Q=0$ and the cosmological horizon is nearly equal to the event horizon ($\xi \equiv 9M^2\mathrm{\Lambda }\simeq 1$). The physical reason for this delay of instability growth appears to be the existence of a cosmological horizon that tends to narrow the negative range of the Regge-Wheeler potential in tortoise coordinates.

A dark photon may kinetically mix with the Standard Model photon, leading to observable cosmological signatures. The mixing is resonantly enhanced when the dark photon mass matches the primordial plasma frequency, which depends sensitively on the underlying spatial distribution of electrons. Crucially, inhomogeneities in this distribution can have a significant impact on the nature of resonant conversions. We develop and describe, for the first time, a general analytic formalism to treat resonant oscillations in the presence of inhomogeneities. Our formalism follows from the theory of level crossings of random fields and only requires knowledge of the one-point probability density function (PDF) of the underlying electron number density fluctuations. We validate our formalism using simulations and illustrate the photon-to-dark photon conversion probability for several different choices of PDFs that are used to characterize the low-redshift Universe.

There is a robust signal for a 511 keV photon line from the Galactic Center, which may originate from dark matter particles with masses of a few MeV. To avoid the bounds from the delayed recombination and from the absence of the line from dwarf galaxies, in 2017, we have proposed a model in which dark matter first decays into a pair of intermediate pico-charged particles $C\overline{C}$ with a lifetime much larger than the age of the Universe. The Galactic magnetic field accumulates the relativistic $C\overline{C}$ that eventually annihilate, producing the $e^{-}{e}^{+}$ pair that gives rise to the 511 keV line. The relativistic pico-charged $C$ particles can scatter on the electrons inside the direct dark matter search detectors imparting a recoil energy of $E_r\sim \mathrm{keV}$. We show that this model can account for the electron recoil excess recently reported by the XENON1T experiment. Moreover, we show that the XENON1T electron recoil data set the most stringent bound on the lifetime of the dark matter within this model.

We calculate the matrix elements of the color-spin interaction for all possible multiquark states of tribaryons in flavor SU(3) broken case. For that purpose, we construct the $\mathrm{flavor}\otimes \mathrm{color}\otimes \mathrm{spin}$ wave functions of the tribaryons, which are taken to be antisymmetric to satisfy the Pauli exclusion principle. Furthermore, we analyze the diquark structure of the tribaryon configurations using the symmetric and antisymmetric basis set of flavor, color, and spin states.

Mixed-dimensional theories have been used to describe condensed matter systems where fermions are constrained to a plane while the gauge fields they interact with remain four dimensional. Here we investigate dynamical breaking of chiral symmetry in the framework of a mixed-dimensional theory that has been successful in describing graphene and other planar Dirac materials and has been dubbed pseudo or reduced quantum electrodynamics. We explore the interplay between the gauge and fermion sectors when a Chern-Simons term is considered and, by exploring the tensor structure of the fermion self-energy, we show that the radiative corrections may induce both a Dirac and a Haldane mass term. Furthermore, by solving the corresponding Schwinger-Dyson equation in a suitable truncation, we nonperturbatively explore the dynamical generation of fermion masses for different values of the electromagnetic coupling and the Chern-Simons coefficient. We also show that for definite parameter values, the contributions from each chirality cancel out and the chiral symmetry may be restored. Possible implications of this result for physical systems, in particular on what concerns the chiral magnetic effect, are discussed.

We compute the soft real photon emission rate from the QCD matter in the vicinity of the critical line at moderate density and the temperature approaching the critical one from above. The obtained production rate exhibits a steep rise close to $T_c$ due to the formation of the slow fluctuation mode.

We show that it is possible to use gravitational wave detectors to observe the occurrence of a first order phase transition in Pati-Salam extensions of the Standard Model. We show that the peak frequency of the expected gravitational wave signals ranges within 0.1–10 Hz. We find amusing that the next generation of gravity waves detectors are able to explore time-honored extensions of the Standard Model occurring at energy scales inaccessible by present and future particle physics accelerators.

We discuss new physics phenomenology of hidden scalar ($S$), pseudoscalar ($P$), vector ($V$) and axial-vector ($A$) particles coupled to nucleons and leptons, which could give contributions to proton charge radius, $(g-2{)}_{\mu }$, ${}^8\mathrm{Be}\text{−}{}^4\mathrm{He}$ anomaly and electric dipole moment (EDM) of Standard Model (SM) particles. In particular, we estimate sensitivity of $\mathrm{NA}64\mu$ experiment to observe muon missing energy events involving hidden scalar and vector particles. That analysis is based on geant4 Monte Carlo simulation of the signal process of muon scattering off target nuclei $\mu N\to \mu NS(V)$ followed by invisible boson decay into dark matter (DM) particles, $S(V)\to \chi \chi$. The existence of light sub-GeV bosons could possibly explain the muon ($g-2$) anomaly observed. We also summarize existing bounds on ATOMKI $X17(J^P=0^{-},1^{\pm })$ boson coupling with neutron, proton, and electron. We implement these constraints to estimate the contribution of $P$, $V$. and $A$ particles to proton charge radius via direct 1-loop calculation of Sachs form factors. The analysis reveals the corresponding contribution is negligible. We also calculate bounds on dark axion portal couplings of dimension-five operators, which contribute to the EDMs of leptons and neutron.

We present the first lattice QCD determination of the $B_c\to J/\psi$ vector and axial-vector form factors. These will enable experimental information on the rate for $B_c$ semileptonic decays to $J/\psi$ to be converted into a value for $V_{cb}$. Our calculation covers the full physical $q^2$ range of the decay and uses nonperturbatively renormalized lattice currents. We use the highly improved staggered quark (HISQ) action for all valence quarks on the second generation MILC ensembles of gluon field configurations including $u$, $d$, $s$ and $c$ HISQ sea quarks. Our HISQ heavy quarks have masses ranging upwards from that of $c$; we are able to reach that of the $b$ on our finest lattices. This enables us to map out the dependence on heavy quark mass and determine results in the continuum limit at the $b$. We use our form factors to construct the differential rates for $B_c^{-}\to J/\psi {\mu }^{-}{\overline{\nu }}_{\mu }$ and obtain a total rate with 7% uncertainty: $\mathrm{\Gamma }(B_c^{-}\to J/\psi {\mu }^{-}{\overline{\nu }}_{\mu })/|{\eta }_{\mathrm{EW}}{V}_{cb}{|}^2=1.73(12)\times {10}^{13}{\mathrm{s}}^{-1}$. Including values for $V_{cb}$, ${\eta }_{\mathrm{EW}}$ and ${\tau }_{B_c}$ yields a branching fraction for this decay mode of 0.0150(11)(10)(3) with uncertainties from lattice QCD, ${\eta }_{\mathrm{EW}}{V}_{cb}$ and ${\tau }_{B_c}$ respectively.

The phenomena of critical slowing down in the iterative solution of the Dirac equation presents a major challenge to further applications of lattice field theory in the approach to the continuum solution. We propose a new multigrid approach for chiral fermions, applicable to both the 5D domain wall or 4D overlap operator. The central idea is to directly coarsen the 4D Wilson kernel, giving an effective domain wall or overlap operator on each level. We provide here an explicit construction for the Shamir domain wall formulation with numerical tests for the 2D Schwinger prototype, demonstrating near ideal multigrid scaling. The framework is designed for a natural extension to 4D lattice QCD chiral fermions, such as the Möbius, Zolotarev or Borici domain wall discretizations or directly to a rational expansion of the 4D overlap operator. For the Shamir operator, the effective overlap operator is isolated by the use of a Pauli-Villars preconditioner in the spirit of the Kähler-Dirac spectral map used in a recent staggered multigrid algorithm [R. C. Brower, E. Weinberg, M. A. Clark, and A. Strelchenko, Phys. Rev. D 97, 114513 (2018)].

In this work we study the radiative decays of heavy-light quarkonia through $M1$ and $E1$ transitions that involve quark-triangle diagrams with two hadron-quark vertices in the framework of 4x4 Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz (CIA). We have expressed the transition amplitude $M_{fi}$ as a linear superposition of terms involving all possible combinations of $++$ and $--$ components of Salpeter wave functions of final and initial hadron, with coefficients being related to the results of pole integrations over a complex $\sigma$ plane. We evaluate the decay widths for $M1$ transitions (${{}^{3}S}_1\to {{}^{1}S}_0+\gamma$) and $E1$ transitions (${{}^{3}S}_1\to {{}^{1}P}_0+\gamma$ and ${{}^{1}P}_0\to {{}^{3}S}_1+\gamma$). We have used algebraic forms of Salpeter wave functions obtained through analytic solutions of mass spectral equations for ground and excited states of $0^{++},1^{--}$, and $0^{-+}$ heavy-light quarkonia in an approximate harmonic oscillator basis to calculate their decay widths. The input parameters used by us were obtained by fitting to their mass spectra. We have compared our results with experimental data and other models and found reasonable agreements.

Using truth-level Monte Carlo simulations of particle interactions in a large volume of liquid argon, we demonstrate physics capabilities enabled by reconstruction of topologically compact and isolated low-energy features, or “blips,” in large liquid argon time projection chamber (LArTPC) events. These features are mostly produced by electron products of photon interactions depositing ionization energy. The blip identification capability of the LArTPC is enabled by its unique combination of size, position resolution precision, and low energy thresholds. We show that consideration of reconstructed blips in LArTPC physics analyses can result in substantial improvements in calorimetry for neutrino and new physics interactions and for final-state particles ranging in energy from the MeV to the GeV scale. Blip activity analysis is also shown to enable discrimination between interaction channels and final-state particle types. In addition to demonstrating these gains in calorimetry and discrimination, some limitations of blip reconstruction capabilities and physics outcomes are also discussed.

Covariant models of loop quantum gravity generically imply dynamical signature change at high density. This article presents detailed derivations that show the fruitful interplay of this new kind of signature change with wave-function proposals of quantum cosmology, such as the no-boundary and tunneling proposals. In particular, instabilities of inhomogeneous perturbations found in a Lorentzian path-integral treatment are naturally cured. Importantly, dynamical signature change does not require Planckian densities when off-shell instantons are relevant.