An analysis of 7.5 years of data in the high-energy starting event sample has been recently published by the IceCube collaboration. The hottest spot in a search for neutrino sources was found far above the Galactic plane and is thus, at first sight, difficult to reconcile with a Galactic origin. In this work, we calculate the cosmic ray (CR) density around nearby, young supernova remnants assuming anisotropic diffusion. Combining the obtained CR densities with the matter distribution deduced from extinction maps, we find two prominent hot spots: The one close to the most significant point in the IceCube search for point sources is created by CRs from the Cygnus loop and has an intensity corresponding to two to four neutrino events. Another, more extended one may be caused by CRs from Vela if CR trajectories are sufficiently disturbed by the magnetic field in the shell around the superbubble loop I.

We present an in depth analysis of the transient events, or glitches, detected at a rate of about one per day in the differential acceleration data of LISA Pathfinder. We show that these glitches fall in two rather distinct categories: fast transients in the interferometric motion readout on one side, and true force transient events on the other. The former are fast and rare in ordinary conditions. The second may last from seconds to hours and constitute the majority of the glitches. We present an analysis of the physical and statistical properties of both categories, including a cross-analysis with other time series like magnetic fields, temperature, and other dynamical variables. Based on these analyses we discuss the possible sources of the force glitches and identify the most likely, among which the outgassing environment surrounding the test-masses stands out. We discuss the impact of these findings on the LISA design and operation, and some risk mitigation measures, including experimental studies that may be conducted on the ground, aimed at clarifying some of the questions left open by our analysis.

We discuss a reformulation of QED in which matter and gauge fields are integrated out explicitly, resulting in a many-body Lorentz covariant theory of $0+1$-dimensional worldlines describing superpairs of spinning charges interacting through Lorentz forces. This provides a powerful, string inspired definition of amplitudes to all-loop orders. In particular, one obtains a more general formulation of Wilson loops and lines, with exponentiated dynamical fields and spin precession contributions, and worldline contour averages exactly defined through first quantized path integrals. We discuss in detail the attractive features of this formalism for high order perturbative computations. We show that worldline S-matrix elements, to all-loop orders in perturbation theory, can be constructed to be manifestly free of soft singularities, with infrared (IR) divergences captured and removed by endpoint photon exchanges at infinity that are equivalent to the soft coherent dressings of the Dyson S-matrix proposed by Faddeev and Kulish. We discuss these IR structures and make connections with soft theorems, the Abelian exponentiation of IR divergences and cusp anomalous dimensions. Follow-up papers will discuss the efficient computation of cusp anomalous dimensions and universal features of soft theorems.

Classical and quantum annealing are computing paradigms that have been proposed to solve a wide range of optimization problems. In this paper, we aim to enhance the performance of annealing algorithms by introducing the technique of degeneracy engineering, through which the relative degeneracy of the ground state is increased by modifying a subset of terms in the objective Hamiltonian. We illustrate this novel approach by applying it to the example of ${\ell }_0$-norm regularization for sparse linear regression, which is, in general, an $\mathsf{NP}$-hard optimization problem. Specifically, we show how to cast ${\ell }_0$-norm regularization as a quadratic unconstrained binary optimization (QUBO) problem, suitable for implementation on annealing platforms. As a case study, we apply this QUBO formulation to energy flow polynomials in high-energy collider physics, finding that degeneracy engineering substantially improves the annealing performance. Our results motivate the application of degeneracy engineering to a variety of regularized optimization problems.

Cosmic ray atmospheric showers provide an effective environment for the production of MeV-scale dark sector particles. We show that, when available, the resonant annihilation of positrons from the shower on atmospheric electrons is the dominant production mechanism by more than an order of magnitude. We provide a quantitative example based on dark photon production and update existing constraints on a corresponding light dark matter model from kilotons neutrino experiments and xenon-based direct detection experiments.

Together with any beyond the Standard Model ultraviolet complete, renormalizable model, one or several exotic particles are usually hypothesized. $CP$-even neutral and doubly charged scalars are common, well-known examples which can contribute to the seven 3-body charged lepton flavor violating decays. The experimental bounds on each branching ratio within this set of processes provide a good test for new physics that can induce powerful constraints on relevant parameter spaces. This is specially true for a third species of particle which, unlike the previous two, is a rare feature of renormalizable models; a doubly charged vector bilepton. We show how these purely leptonic bounds can indeed induce relevant exclusion regions for the corresponding particles masses, stronger than what have been considered in the literature for the alternative flavor-conserving case, and examine how interference effects can influence these regions in a nontrivial way.

For the first time, center vortices are identified on SU(3) lattice ensembles that include dynamical fermions. Using a variational method, the static quark potential is calculated on untouched, vortex-removed, and vortex-only fields. Two dynamical ensembles and one pure gauge ensemble are studied, allowing for an exploration of the impact of dynamical fermions on the center-vortex vacuum. Novel modifications to the standard Coulomb term are introduced to describe the long range behavior of the vortex-removed potential. These modifications remove a source of systematic error in the fitted string tension on the original ensembles. Our pure Yang-Mills result is consistent with previous studies, where projected center-vortex fields only reproduce approximately two thirds of the string tension. Remarkably, we find that the vortex-only fields on both dynamical lattices are able to fully reproduce the respective untouched string tensions.

Precise quantification of the structure of nucleons is one of the crucial aims of hadronic physics for the coming years. The expected progress related to ongoing and planned experiments should be accompanied by calculations of partonic distributions from lattice QCD. While key insights from the lattice are expected to come for distributions that are difficult to access experimentally, it is important that lattice QCD can reproduce the well-known unpolarized parton distribution functions (PDFs) with full control over systematic uncertainties. One of the novel methods for accessing the partonic $x$-dependence is the pseudodistribution approach, which employs matrix elements of a spatially extended nonlocal Wilson line operator of length $z$. In this paper, we address the issue of discretization effects, related to the necessarily nonzero value of the lattice spacing $a$, which start at first order in $a$ as a result of the nonlocal operator. We use twisted mass fermions simulated at three values of the lattice spacing, at a pion mass of 370 MeV, and extract the continuum limit of isovector unpolarized PDFs. We also test, for the first time in the pseudodistribution approach, the effects of the recently derived two-loop matching. Finally, we address the issue of the reliability of the extraction with respect to the maximal value of $z$.

We extend our previous work on the light-quark connected part, $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$, of the leading-order hadronic-vacuum-polarization (HVP) contribution to the muon anomalous magnetic moment $a_{\mu }$, using staggered fermions, in several directions. We have collected more statistics on ensembles with lattice spacings of 0.06, 0.09 and 0.12 fm, and we added two new ensembles, both with lattice spacing 0.15 fm, but with different volumes. The increased statistics allow us to reduce statistical errors on $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$ and related window quantities significantly. We also calculate the current-current correlator from which $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$ is obtained to next-to-next-to-leading order (NNLO) in staggered chiral perturbation theory, so that we can correct lattice values for $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$ to NNLO for finite-volume, pion-mass mistuning and taste-breaking effects. We discuss the applicability of NNLO chiral perturbation theory to $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$ and to the window quantities, emphasizing that it provides a systematic effective-field theory (EFT) approach to $a_{\mu }^{\mathrm{HVP},\mathrm{lqc}}$, but not to short- or intermediate-distance window quantities. This makes it difficult to assess systematic errors on the standard intermediate-distance window quantity that is now widely considered in the literature. In view of this, we investigate a longer-distance window, for which EFT methods should be more reliable. Our most important conclusion is that, especially for staggered fermions, new high-statistics computations at lattice spacings smaller than 0.06 fm are indispensable. Our results are based on configurations provided by the MILC and also by the CalLat collaborations.

We use a version of the instant-form relativistic quantum mechanics of composite systems to obtain the gravitational form factors of the pion in a common approach to its electroweak and gravitational properties. In the preceding work [Phys. Rev. D 103, 014029 (2021)], we formulated the mathematical background, presented the principal scheme of calculation and testified the obtained qualitative results to satisfy the general constraints given by the principles of the theory of hadron structure. In the present work, we give the detailed calculation of the gravitational form factors in the large range of momentum transfer, their static limits, and the slopes at zero value, the mean-square mass and mechanical radii of the pion. Now we take into account the gravitational structure of the constituent quarks. We show that the results are almost insensitive to the type of model two-quark wave function in a close analogy to the case of the pion electromagnetic form factor. We present a correct calculation of the form factor $D$ and corresponding matrix element of the energy-momentum tensor, going beyond the scope of the modified impulse approximation. Most of the parameters that we use for the calculation had been fixed even earlier in our works on the pion electromagnetic form factors. The only free parameter is the $D$-term of the constituent quark, which we fix by fitting the result for the slope at zero of the normalized to pion $D$-term form factor $D$ of the pion, to a chosen experimental value.

We present SKMHS22, a new set of diffractive parton distribution functions (PDFs) and their uncertainties at next-to-leading-order and next-to-next-to-leading-order accuracy in perturbative QCD within the xFitter framework. We describe all available diffractive DIS datasets from HERA and the most recent high-precision H1/ZEUS combined measurements considering three different scenarios. First, we extract the diffractive PDFs considering the standard twist-2 contribution. Then, we include the twist-4 correction from the longitudinal virtual photons. Finally, the contribution of subleading Reggeon exchange to the structure-function $F_2^D$ is also examined. For the contribution of heavy flavors, we utilize the Thorne-Roberts general mass variable number scheme. We show that for those corrections, in particular, the twist-4 contribution allows us to include the high-$\beta$ region and leads to a better description of the diffractive DIS datasets. We find that the inclusion of the subleading Reggeon exchange significantly improves the description of the diffractive DIS cross-section measurements. We then investigate the stability of the SKMHS22 QCD fit upon the inclusion of higher-order QCD corrections and show that it slightly improves the description of the data. The resulting sets are in good agreement with all diffractive DIS data analyzed, which cover a wider kinematical range than in previous fits. The SKMHS22 diffractive PDFs sets presented in this work are available via the LHAPDF interface. We also make suggestions for future research in this area.

Following the observation of the fully heavy tetraquark candidates $X(6900)$ and possible $X(6300)$ in the di-$J/\psi$ spectrum by the LHCb Collaboration, we investigate the near-threshold dynamics of the pseudoscalar quarkonium pairs in a coupled-channel approach in the di-${\eta }_c$ channel. We show that the Pomeron exchange mechanism should be a general dynamics in the near-threshold heavy quarkonium pair interactions. In the di-${\eta }_c$ channel, a coupled-channel system involving the di-${\eta }_c$, ${\eta }_c-{\eta }_c(2S)$ and di-${\eta }_c(2S)$ interactions can be established. Their $S$-wave interactions near threshold via the Pomeron exchange potential can produce near-threshold resonance poles similar to the di-$J/\psi$, $J/\psi -\psi (2S)$, and di-$\psi (2S)$ coupled channels. Interestingly, we find here that the pole positions are more shifted to the corresponding thresholds and turn out to be different from those seen in the di-$J/\psi$ spectrum. Taking into account the suppression of the heavy quark spin flips in the transitions between two vector and two pseudoscalar heavy quarkonium systems, the enhancements in the di-${\eta }_c$ spectrum should be different from those seen in the di-$J/\psi$ channel. Experimental study of the di-${\eta }_c$ channel should be useful for disentangling the nature of the fully heavy tetraquark systems.

In this work we have explored the imaginary part of the heavy quark potential and subsequently the dissociation of heavy quarkonia at finite temperature and in a magnetic field. With respect to earlier investigations on this topic, the present work contains three new ingredients. The first one is considering all Landau level summations, for which the present work can be applicable in the entire magnetic field domain—from weak to strong. The second one is the general structure of the gauge boson propagator in a hot magnetized medium, which is used here in the heavy quark potential problem for the first time. The third one is a rich anisotropic structure of the complex heavy quark potential, which explicitly depends on the longitudinal and transverse distance. By comparing with earlier references, we have attempted to display our new contributions by plotting heavy quark potential tomography and dissociation probability at finite temperature and in a magnetic field.

The properties of the $B_c$-meson family ($c\overline{b}$) are still not well determined experimentally because the specific mechanisms of formation and decay remain poorly understood. Unlike heavy quarkonia, i.e., the hidden heavy quark-antiquark sectors of charmonium ($c\overline{c}$) and bottomonium ($b\overline{b}$), the $B_c$ mesons cannot annihilate into gluons and they are, consequently, more stable. The excited $B_c$ states, lying below the lowest strong-decay $BD$ threshold, can only undergo radiative decays and hadronic transitions to the $B_c$ ground state, which then decays weakly. As a result of this, a rich spectrum of narrow excited states below the $BD$ threshold appear, whose total widths are 2 orders of magnitude smaller than those of the excited levels of charmonium and bottomonium. In a different article, we determined bottom-charmed meson masses using a nonrelativistic constituent quark model which has been applied to a wide range of hadron physical observables, and thus the model parameters are completely constrained. Herein, continuing to our study of the $B_c$ sector, we calculate the relevant radiative decay widths and hadronic transition rates between $c\overline{b}$ states which are below the $BD$ threshold. This shall provide the most promising signals for discovering excited $B_c$ states that are below the lowest strong-decay $BD$ threshold. Finally, our results are compared with other models to measure the reliability of the predictions and point out differences.

Inspired by the recent observation of a new structure, $X(4014)$, in the process $\gamma \gamma \to \gamma \psi (2S)$, we evaluate the possibility of assigning $X(4014)$ as a $D^{*}{\overline{D}}^{*}$ molecular state with $I(J^{PC})=0(0^{++})$ by investigating the hidden charm decays of $X(4014)$. The partial widths of $J/\psi \omega$, ${\eta }_c\eta$ and ${\eta }_c{\eta }^{\prime }$ channels are evaluated to be about (0.41–5.00), (2.05–7.49) and (0.11–0.51) MeV, respectively. Considering the experimental observation and the present estimations, we proposed to search $X(4014)$ in the $\gamma \gamma \to J/\psi \omega$ process in Belle II.

Inflationary cosmology proposes that the early Universe undergoes accelerated expansion, driven, in simple scenarios, by a single scalar field or inflaton. The form of the inflaton potential determines the initial spectra of density perturbations and gravitational waves. We show that constraints on the duration of inflation together with the BICEP3/Keck bounds on the gravitational wave background imply that higher derivatives of the potential are nontrivial with a confidence of 99%. Such terms contribute to the scale dependence, or running, of the density perturbation spectrum. We clarify the “universality classes” of inflation in this limit showing that a very small gravitational wave background can be correlated with a larger running. If pending experiments do not observe a gravitational wave background the running will be at the threshold of detectability if inflation is well described at third order in the slow-roll expansion.

In terms of flavor invariants, we establish the intimate connection between leptonic $CP$ violation in the canonical seesaw model for neutrino masses and that in the seesaw effective field theory (SEFT). For the first time, we calculate the Hilbert series and explicitly construct the primary flavor invariants in the SEFT by considering both the dimension-five Weinberg operator ${\mathcal{O}}_5^{\alpha \beta }=\overline{{\ell }_{\alpha \mathrm{L}}}\tilde{H}{\tilde{H}}^{\mathrm{T}}{\ell }_{\beta \mathrm{L}}^{\mathrm{C}}$ and the dimension-six operator ${\mathcal{O}}_6^{\alpha \beta }=(\overline{{\ell }_{\alpha \mathrm{L}}}\tilde{H})\mathrm{i}\cancel{\partial }({\tilde{H}}^{†}{\ell }_{\beta \mathrm{L}})$ at the tree-level matching. The inclusion of only the Wilson coefficients $C_5^{\alpha \beta }$ and $C_6^{\alpha \beta }$ already enables the SEFT to incorporate all physical information about the full seesaw model. Moreover, the minimal sufficient and necessary conditions for $CP$ conservation both in the SEFT and in the full theory are clarified, and the matching between the flavor invariants in both theories is accomplished. Through the matching of flavor invariants, the $CP$ asymmetries necessary for successful leptogenesis are directly linked to those in neutrino-neutrino and neutrino-antineutrino oscillations at low energies. Surprisingly, it is revealed that the precise measurements of $C_5^{\alpha \beta }$ and $C_6^{\alpha \beta }$ in low-energy experiments are powerful enough to probe the full seesaw model, including $CP$ violation for cosmological matter-antimatter asymmetry.

In this paper we present the first measurements of an exclusive electron neutrino cross section with the MicroBooNE experiment using data from the Booster neutrino beamline at Fermilab. These measurements are made for a selection of charged-current electron neutrinos without final-state pions. Differential cross sections are extracted in energy and angle with respect to the beam for the electron and the leading proton. The differential cross section as a function of proton energy is measured using events with protons both above and below the visibility threshold. This is done by including a separate selection of electron neutrino events without reconstructed proton candidates in addition to those with proton candidates. Results are compared to the predictions from several modern generators, and we find the data agrees well with these models. The data shows best agreement, as quantified by the $p$-value, with the generators that predict a lower overall cross section, such as GENIE v3 and NuWro.

While it is usually stated that dimensional regularization (DR) has no direct physical interpretation, consensus has recently grown on the idea that it might be endowed with special physical properties that would provide the mechanism that solves the naturalness and hierarchy problem. Comparing direct Wilsonian calculations with the corresponding DR ones, we find that DR indeed has a well-defined physical meaning, and we point out its limitations. In particular, our results show that DR cannot provide the solution to the naturalness and hierarchy problem. The absence of too large corrections to the Higgs boson mass is due to a secretly realized fine-tuning, rather than special physical properties of DR. We also investigate these issues within the Wilsonian RG framework, and by comparison with the usual perturbative RG analysis, we show that several popular proposals for the resolution of the problem, commonly considered as physical mechanisms free of fine-tuning, again secretly implement the tuning.

We apply the local composite operator method to construct the three loop effective potential for the dimension two operator $\frac{1}{2}{A_{\mu }^a}^2$ in the Landau gauge in quantum chromodynamics. For $SU(3)$ we show that the three loop value of the effective mass of the gluon is similar to the two loop estimates when the number of massless quarks is strictly less than five for $SU(3)$.