The extraction of the magnetic form factor of the nucleon at zero momentum transfer is usually performed by adopting a parametrization for its momentum dependence and fitting the results obtained at finite momenta. We present a position space method that allows us to remove the momentum prefactor in the form factor decomposition and hence compute the magnetic form factor directly at zero momentum without the need to assume a functional form for its momentum dependence. The method is explored on one ensemble using $N_f=2+1+1$ Wilson twisted mass fermions with a light quark mass corresponding to $M_{\pi }=373\mathrm{MeV}$ and a lattice spacing of $a\approx 0.082\mathrm{fm}$. We obtain results for the isovector magnetic moment and for the proton and neutron magnetic moments. The value we find for the isovector magnetic moment is larger as compared to fitting the form factor at the discrete values of the lattice momentum transfers using a dipole Ansatz, bringing it closer to the experimental value.

Results obtained by various experiments show that the $D_{s0}^{*}(2317)$ and $D_{s1}(2460)$ mesons are very narrow states located below the $DK$ and $D^{*}K$ thresholds, respectively. This is markedly in contrast with the expectations of naive quark models and heavy quark symmetry. Motivated by a recent lattice study which addresses the mass shifts of the $c\overline{s}$ ground states with quantum numbers $J^P=0^{+}$ [$D_{s0}^{*}(2317)$] and $J^P=1^{+}$ [$D_{s1}(2460)$] due to their coupling with $S$-wave $D^{(*)}K$ thresholds, we perform a similar analysis within a nonrelativistic constituent quark model in which quark-antiquark and meson-meson degrees of freedom are incorporated. The quark model has been applied to a wide range of hadronic observables, and thus the model parameters are completely constrained. The coupling between quark-antiquark and meson-meson Fock components is done using a ${}^3{P}_0$ model in which its only free parameter $\gamma$ has been elucidated, performing a global fit to the decay widths of mesons that belong to different quark sectors, from light to heavy. We observe that the coupling of the $0^{+}$ $(1^{+})$ meson sector to the $DK$ $(D^{*}K)$ threshold is the key feature to simultaneously lower the masses of the corresponding $D_{s0}^{*}(2317)$ and $D_{s1}(2460)$ states predicted by the naive quark model and describe the $D_{s1}(2536)$ meson as the $1^{+}$ state of the $j_q^P=3/2^{+}$ doublet predicted by heavy quark symmetry, reproducing its strong decay properties. Our calculation allows us to introduce the coupling with the $D$-wave $D^{*}K$ channel and the computation of the probabilities associated with the different Fock components of the physical state.

We propose a modified definition for a quasiparton distribution function (QPDF) with an equal-time correlator in the large momentum limit, whose two pieces of spacelike Wilson links are oriented in orthogonal directions. It is explicitly shown at the one-loop level that the linear divergence in the original QPDF with dipolar Wilson links, which complicates its matching to the standard light-cone parton distribution function (LPDF), is removed. The LPDF can then be extracted reliably from Euclidean lattice data for the QPDF with the nondipolar Wilson links.

We systematically study light ($<\text{few}\mathrm{GeV}$) dark matter (DM) models that thermalize with visible matter through the Higgs portal and identify the remaining gaps in the viable parameter space. Such models require a comparably light scalar mediator that mixes with the Higgs to avoid DM overproduction and can be classified according to whether this mediator decays (in)visibly. In a representative benchmark model with Dirac fermion DM, we find that, even with conservative assumptions about the DM-mediator coupling and mass ratio, the regime in which the mediator is heavier than the DM is fully ruled out by a combination of collider, rare meson decay, and direct detection limits; future and planned experiments including NA62 can further improve sensitivity to scenarios in which the Higgs portal interaction does not determine the DM abundance. The opposite regime in which the mediator is lighter than the DM and the latter annihilates to pairs of visibly decaying mediators is still viable, but much of the parameter space is covered by rare meson decay, supernova cooling, beam dump, and direct detection constraints. Nearly all of these conclusions apply broadly to the simplest variations (e.g., scalar or asymmetric DM). Future experiments including SHiP, NEWS, and Super-CDMS SNOLAB can greatly improve coverage to this class of models.

Forward single ${\pi }^0$ production by coherent neutral-current interactions, $\nu \mathcal{A}\to \nu \mathcal{A}{\pi }^0$, is investigated using a $2.8\times 10^{20}$ protons-on-target exposure of the MINOS Near Detector. For single-shower topologies, the event distribution in production angle exhibits a clear excess above the estimated background at very forward angles for visible energy in the range 1–8 GeV. Cross sections are obtained for the detector medium comprised of 80% iron and 20% carbon nuclei with $⟨\mathcal{A}⟩=48$, the highest-$⟨\mathcal{A}⟩$ target used to date in the study of this coherent reaction. The total cross section for coherent neutral-current single ${\pi }^0$ production initiated by the ${\nu }_{\mu }$ flux of the NuMI low-energy beam with mean (mode) $E_{\nu }$ of 4.9 GeV (3.0 GeV), is $77.6\pm 5.0(\mathrm{stat}{)}_{-16.8}^{+15.0}(\mathrm{syst})\times {10}^{-40}{\mathrm{cm}}^2\mathrm{per}\mathrm{nucleus}$. The results are in good agreement with predictions of the Berger-Sehgal model.

We consider a theory with isotropic nonbirefringent Lorentz violation in the photon sector and explore the effects on the development of the electromagnetic component of extensive air showers in the Earth atmosphere. Specifically, we consider the case of a “fast” photon with a phase velocity larger than the maximum attainable velocity of a massive Dirac fermion (this case corresponds to a negative Lorentz-violating parameter $\kappa$ in the action). Shower photons with above-threshold energies decay promptly into electron-positron pairs, instead of decaying by the conventional production of electron-positron pairs in the background fields of atomic nuclei. This rapid production of charged leptons accelerates the shower development, decreasing the atmospheric depth of the shower maximum ($X_{\max }$) by an amount which could be measured by cosmic-ray observatories. Precise measurements of $X_{\max }$ could then improve existing limits on the negative Lorentz-violating parameter $\kappa$ by several orders of magnitude.

We study the finite volume effects on the electric polarizability for the neutron, neutral pion, and neutral kaon using eight dynamically generated two-flavor nHYP-clover ensembles at two different pion masses: 306(1) and 227(2) MeV. An infinite volume extrapolation is performed for each hadron at both pion masses. For the neutral kaon, finite volume effects are relatively mild. The dependence on the quark mass is also mild, and a reliable chiral extrapolation can be performed along with the infinite volume extrapolation. Our result is ${\alpha }_{K^0}^{\text{phys}}=0.356(74)(46)\times {10}^{-4}{\mathrm{fm}}^3$. In contrast, for neutron, the electric polarizability depends strongly on the volume. After removing the finite volume corrections, our neutron polarizability results are in good agreement with chiral perturbation theory. For the connected part of the neutral pion polarizability, the negative trend persists, and it is not due to finite volume effects but likely sea quark charging effects.

The extraction of hadron matrix elements in lattice QCD using the standard two- and three-point correlator functions demands careful attention to systematic uncertainties. One of the most commonly studied sources of systematic error is contamination from excited states. We apply the variational method to calculate the axial vector current $g_A$, the scalar current $g_S$, the scalar current $g_T$ and the quark momentum fraction $⟨x⟩$ of the nucleon and we compare the results to the more commonly used summation and two-exponential fit methods. The results demonstrate that the variational approach offers a more efficient and robust method for the determination of nucleon matrix elements.

We report on a two-flavor lattice QCD study of the axial, charge, and matter distributions of the $B$ meson and its first radial excitation. As our framework is the static limit of heavy quark effective theory (HQET), taking their Fourier transform gives access to several form factors at the kinematical point $q^2=0$ while our previous computations in that framework were performed at $q_{\max }^2$. Moreover, they provide some useful information on the nature of an excited state, i.e., a radial excitation of a quark-antiquark bound state or a multihadron state.

Semileptonic ${\mathrm{\Lambda }}_b$ decays are investigated in the framework of the relativistic quark model based on the quasipotential approach and the quark-diquark picture of baryons. The decay form factors are expressed through the overlap integrals of the initial and final baryon wave functions. All calculations are done without employing nonrelativistic and heavy quark expansions. The momentum transfer dependence of the decay form factors is explicitly determined in the whole accessible kinematical range without any extrapolations or model assumptions. Both the heavy-to-heavy ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c\ell {\nu }_{\ell }$ and heavy-to-light ${\mathrm{\Lambda }}_b\to p\ell {\nu }_{\ell }$ decay branching fractions are calculated. The results agree within error bars with the experimental value of the branching fraction of the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c^{+}{l}^{-}{\overline{\nu }}_l$ decay. From the recent LHCb data on the ratio of the branching fractions of the heavy-to-light and heavy-to-heavy semileptonic ${\mathrm{\Lambda }}_b$ decays the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements $|V_{ub}|/|V_{cb}|$ is obtained. It is consistent with the corresponding ratio determined from the inclusive $B$ meson decays.

We present a feasibility study, to search for dark matter at the LHC, in events with one soft hadronically decaying tau lepton and missing transverse energy recoiling against a hard $p_T$ jet from initial state radiation. This methodology allows the search for supersymmetry in compressed mass spectra regions, where the mass difference between the lightest neutralino, ${\tilde{\chi }}_1^0$, and the stau (the tau superpartner), $\tilde{\tau }$, is small. Several theoretical models predict a direct connection between thermal bino dark matter and staus within this scenario. We show that compressed regions, not excluded by ATLAS nor CMS experiments, are opened up with the increase in experimental sensitivity reached with the proposed methodology. The requirement of a hard jet from initial state radiation combined with a soft tau lepton is effective in reducing Standard Model backgrounds, providing expected significances greater than $3\sigma$ for ${\tilde{\chi }}_1^{\pm }$ masses up to 300 GeV and $\tilde{\tau }-{\tilde{\chi }}_1^0$ mass gaps below 25 GeV with only $30{\mathrm{fb}}^{-1}$ of 13 TeV data from the LHC.

Including the generalized $CP$ symmetry, we have performed a comprehensive scan of leptonic mixing patterns that can be obtained from finite discrete groups with order less than 2000. Both the semidirect approach and its variant are considered. The lepton mixing matrices that can admit a good agreement with experimental data can be organized into eight different categories up to possible row and column permutations. These viable mixing patterns can be completely obtained from the discrete flavor groups $\mathrm{\Delta }(6n^2)$, $D_{9n,3n}^{(1)}$, $A_5$ and $\mathrm{\Sigma }(168)$ combined with $CP$ symmetry. We perform a detailed analytical and numerical analysis for each possible mixing pattern. The resulting predictions for lepton mixing parameter, neutrinoless double beta decay, and flavored leptogenesis are studied.

We study asymptotically AdS Brans-Dicke (BD) backgrounds, where the Ricci tensor R is coupled to a scalar in the radial dimension, as effective models of metals with a varying coupling constant. We show that, for translationally invariant backgrounds, the regular part of the dc conductivity ${\sigma }_Q$ deviates from the universal result of Einstein-Maxwell-dilaton (EMD) models. However, the shear viscosity to entropy ratio saturates the Kovtun-Son-Starinets (KSS) bound. Similar results apply to more general f(R) gravity models. In four bulk dimensions we study momentum relaxation induced by gravitational and electromagnetic axion-dependent couplings. For sufficiently strong momentum dissipation induced by the former, a recently proposed bound on the dc conductivity $\sigma$ is violated for any finite electromagnetic axion coupling. Interestingly, in more than four bulk dimensions, the dc conductivity for strong momentum relaxation decreases with temperature in the low temperature limit. In line with other gravity backgrounds with momentum relaxation, the shear viscosity to entropy ratio is always lower than the KSS bound. The numerical computation of the optical conductivity reveals a linear growth with the frequency in the limit of low temperature, low frequency and large momentum relaxation. We have also shown that the module and argument of the optical conductivity for intermediate frequencies are not consistent with cuprates’ experimental results, even assuming several channel of momentum relaxation.

We study the vacuum (i.e., zero-temperature) Casimir energy for a system of neutral conductors which are isolated, as opposed to grounded. The former is meant to describe a situation where the total charge on each conductor, as well as all of its fluctuations, vanishes, while the latter describes a situation where the conductors are connected to a charge reservoir. We compute the difference between the vacuum energies for a given system of conductors, but subjected to the two different conditions stated above. The results can be written in terms of a generalized, frequency-dependent capacitance matrix of the system. Using a multipolar expansion, we show that the grounded Casimir energy includes a monopole-monopole interaction term that is absent in the isolated case in the large distance limit.

Based on the Son-Yamamoto relation obtained for the transverse part of the triangle axial anomaly in ${\mathrm{QCD}}_4$, we derive its analog in a two-dimensional system. It connects the transverse part of the mixed vector-axial current two-point function with the diagonal vector and axial current two-point functions. Being fully nonperturbative, this relation may be regarded as anomaly matching for conductivities or certain transport coefficients depending on the system. We consider the holographic renormalization group flows in holographic Yang-Mills-Chern-Simons theory via the Hamilton-Jacobi equation with respect to the radial coordinate. Within this holographic model, it is found that the renormalization group flows for the following relations are diagonal: the Son-Yamamoto relation and the left-right polarization operator. Thus, the Son-Yamamoto relation holds at a wide range of energy scales.

We investigate the static and spherically symmetric solutions in a class of the generalized Proca theory with the nonminimal coupling to the Einstein tensor. First, we show that the solutions in the scalar-tensor theory with the nonminimal derivative coupling to the Einstein tensor can be those in the generalized Proca theory with the vanishing field strength. We then show that when the field strength takes the nonzero value, the static and spherically symmetric solutions can be found only for the specific value of the nonminimal coupling constant. Second, we investigate the first-order slow-rotation corrections to the static and spherically symmetric background. We find that for the background with the vanishing electric field strength the slowly rotating solution is identical to the Kerr–(anti-)de Sitter solutions in general relativity. On the other hand, for the background with the nonvanishing electric field strength the stealth property can be realized at the first order in the slow-rotation approximation.

We construct a $T$-axisymmetric, spacelike, spherically symmetric, constant mean curvature (CMC) hypersurface foliation in the Kruskal extension with properties such that the mean curvature varies in each slice and ranges from minus infinity to plus infinity. This family of hypersurfaces extends the CMC foliation discussions by Malec and Ó Murchadha in 2009 [Phys. Rev. D 80, 024017 (2009)].

Five-dimensional Lovelock gravity is investigated in the first order formalism. A new class of exact solutions is constructed: the Bañados, Teitelboim, Zanelli black rings with and without torsion. We show that our solution with torsion exists in a different sector of the Lovelock gravity, as compared to the Lovelock Chern-Simons sector or the one investigated by Canfora et al. The conserved charges of the solutions are found using Nester’s formula, and the results are confirmed by the canonical method. We show that the theory linearized around the background with torsion possesses two additional degrees of freedom with respect to general relativity.

General relativity extensions based on renormalization group effects are motivated by a known physical principle and constitute a class of extended gravity theories that have some unexplored unique aspects. In this work we develop in detail the Newtonian and post-Newtonian limits of a realization called renormalization group extended general relativity (RGGR). Special attention is given to the external potential effect, which constitutes a type of screening mechanism typical of RGGR. In the Solar System, RGGR depends on a single dimensionless parameter ${\overline{\nu }}_{\odot }$, and this parameter is such that for ${\overline{\nu }}_{\odot }=0$ one fully recovers GR in the Solar System. Previously this parameter was constrained to be $|{\overline{\nu }}_{\odot }|\lesssim {10}^{-21}$, without considering the external potential effect. Here we show that under a certain approximation RGGR can be cast in a form compatible with the parametrized post-Newtonian (PPN) formalism, and we use both the PPN formalism and the Laplace-Runge-Lenz technique to put new bounds on ${\overline{\nu }}_{\odot }$, either considering or not the external potential effect. With the external potential effect the new bound reads $|{\overline{\nu }}_{\odot }|\lesssim {10}^{-16}$. We discuss the possible consequences of this bound on the dark matter abundance in galaxies.