In this work, we calculate the one-loop contribution to the polarization tensor for photons (and gluons) in the presence of a classical background magnetic field with white-noise stochastic fluctuations. The magnetic field fluctuations are incorporated into the fermion propagator in a quasiparticle picture, which we developed in previous works using the replica trick. By focusing on the strong-field limit, here we explicitly calculate the polarization tensor. Our results reveal that it does not satisfy the transversality conditions outlined by the Ward identity, thus breaking the $U(1)$ symmetry. As a consequence, in the limit of vanishing photon four-momenta, the tensor coefficients indicate the emergence of an effective magnetic mass induced on photons (and gluons) by these stochastic fluctuations, leading to the interpretation of a dispersive medium with a noise-dependent index of refraction.

In the limit of large nuclear charge, $Z\gg 1$, or small lepton velocity, $\beta \ll 1$, Coulomb corrections to nuclear beta decay and related processes are enhanced as $Z\alpha /\beta$ and become large or even nonperturbative (with $\alpha$ the QED fine structure constant). We provide a constructive demonstration of factorization to all orders in perturbation theory for these processes and compute the all-orders hard and soft functions appearing in the factorization formula. We clarify the relationship between effective field theory amplitudes and historical treatments of beta decay in terms of a Fermi function.

SO(10) grand unified theory with minimum parameters in the Yukawa sector employs the Peccei-Quinn symmetry that solves the strong $CP$ problem. Such an economical Yukawa sector is highly appealing and has been extensively studied in the literature. However, when the running of the renormalization group equations of the Yukawa couplings are considered, this scenario shows some tension with the observed fermion masses and mixing. In this work, we propose an extension of the minimal framework that utilizes lower dimensional representations and alleviates this tension by introducing only a few new parameters. The proposed model consists of a fermion in the fundamental and a scalar in the spinorial representations. While the latter is needed to implement the Peccei-Quinn symmetry successfully, the presence of both is essential in obtaining an excellent fit to the fermion mass spectrum. In our model, axions serve the role of dark matter, and the out-of-equilibrium decays of the right-handed neutrinos successfully generate the matter-antimatter symmetry of the Universe.

Dopant atoms in semiconductors can be ionized with $\sim 10\mathrm{meV}$ energy depositions, allowing for the design of low-threshold detectors. We propose using doped semiconductor targets to search for sub-MeV dark matter scattering or sub-eV dark matter absorption on electrons. Currently unconstrained cross sections could be tested with a 1 g-day exposure in a doped detector with backgrounds at the level of existing pure semiconductor detectors, but improvements would be needed to probe the freeze-in target. We discuss the corresponding technological requirements and lay out a possible detector design.

We study the prospects for observing exotic decays of the Standard Model Higgs boson $h$ into light beyond the Standard Model scalars $a$ with mass $m_a\lesssim m_h/2$ in the single Higgs and Higgs pair production channels at the high luminosity run of the Large Hadron Collider (HL-LHC). Discovery prospects for single Higgs production in the gluon-gluon fusion and vector boson fusion modes with the Higgs boson decaying via the exotic mode $h\to aa\to 4\tau$ are analyzed at the HL-LHC. The projected sensitivity for exotic Higgs decays in the nonresonant Higgs pair production channel $pp\to hh\to (h\to b\overline{b})(h\to aa\to 4\tau )\to 2b4\tau$ at the HL-LHC and a future $\sqrt{s}=100\mathrm{TeV}$ hadron collider (FCC-hh) are also estimated. Furthermore, we study HL-LHC’s potential reach for the Higgs-strahlung process in the $2b4\tau$ channel, taking into account the contamination from nonresonant Higgs pair production. Finally, the potential reach for resonant Higgs pair production in the $2b4\tau$ channel at the HL-LHC is also explored for several choices of $\{m_H,m_a\}$. Our studies suggest that significant improvements over existing bounds are achievable in several production channels, motivating new dedicated searches for $h\to aa\to 4\tau$ at the HL-LHC and future colliders.

Current long-baseline accelerator experiments, NOvA and T2K, are making excellent measurements of neutrino oscillations and the next generation of experiments, DUNE and HK, will make measurements at the $\mathcal{O}(1\%)$ level of precision. These measurements are a combination of the appearance channel which is more challenging experimentally but depends on many oscillation parameters, and the disappearance channel which is somewhat easier and allows for precision measurements of the atmospheric mass splitting and the atmospheric mixing angle. It is widely recognized that the matter effect plays a key role in the appearance probability, yet the effect on the disappearance probability is surprisingly small for these experiments. Here we investigate both exactly how small the effect is and show that it just begins to become relevant in the high statistics regime of DUNE.

We derive the electromagnetic response of a particular fermionic sector in the minimal QED contribution to the Standard Model Extension (SME), which can be physically realized in terms of a model describing a tilted and anisotropic Weyl semimetal (WSM). The contact is made through the identification of the Dirac-like Hamiltonian resulting from the SME with that corresponding to the WSM in the linearized tight-binding approximation. We first calculate the effective action by computing the nonperturbative vacuum polarization tensor using thermal field theory techniques, focusing upon the corrections at finite chemical potential and zero temperature. Next, we confirm our results by a direct calculation of the anomalous Hall current within a chiral kinetic theory approach. In an ideal Dirac cone picture of the WSM (isotropic and nontilted) such response is known to be governed by axion electrodynamics, with the space-time dependent axion angle $\mathrm{\Theta }(\mathit{r},t)=2(\mathit{b}·\mathit{r}-b_{0}t)$, being $2\mathit{b}$ and $2b_0$ the separation of the Weyl nodes in momentum and energy, respectively. In this paper we demonstrate that the node tilting and the anisotropies induce novel corrections at a finite density which however preserve the structure of the axionic field theory. We apply our results to the ideal Weyl semimetal ${\mathrm{EuCd}}_2{\mathrm{As}}_2$ and to the highly anisotropic and tilted monopnictide TaAs.

We propose a cosmological model in the framework of Poincaré gauge gravity, in which the cosmological constant, the inflaton, and the dark matter candidate all naturally originate. The cosmological constant originates in the process of breaking of the Poincaré symmetries down to the Lorentz symmetries. We select a gauge Lagrangian without any additional matter fields, which can be regarded as a minimum extension of general relativity with two more massive modes from the Lorentz connection. Numerical analysis shows that the scalar dominates a slow-rolling inflation and the pseudoscalar behaves as a dark matter candidate.

The physics of primordial black holes can be affected by the non-Gaussian statistics of the density fluctuations that generate them. Therefore, it is important to have good theoretical control of the higher-order correlation functions for primordial curvature perturbations. By working at leading order in a $1/|\eta |$ expansion, we analytically determine the bispectrum of curvature fluctuations for single field inflationary scenarios producing primordial black holes. The bispectrum has a rich scale and shape dependence, and its features depend on the dynamics of the would-be decaying mode. We apply our analytical results to study gravitational waves induced at second order by enhanced curvature fluctuations. Their statistical properties are derived in terms of convolution integrals over wide momentum ranges, and they are sensitive on the scale and shape dependence of the curvature bispectrum we analytically computed.

In turbulent magnetized plasmas, charged particles can be accelerated to high energies through their interactions with the turbulent motions. As they do so, they draw energy from the turbulence, possibly up to the point where they start modifying the turbulent cascade. Stochastic acceleration then enters a nonlinear regime because turbulence damping backreacts in turn on the acceleration process. This article develops a phenomenological model to examine this situation in detail and to explore its consequences for the particle and turbulent energy spectra. We determine a criterion that specifies the threshold of nonthermal particle energy density and the characteristic momentum beyond which backreaction becomes effective. Once the backreaction sets in, the turbulence cascade becomes damped below a length scale that keeps increasing in time. The accelerated particle momentum distribution develops a near power-law of the form $\mathrm{d}n/\mathrm{d}p\propto p^{-s}$ with $s\sim 2$ beyond the momentum at which backreaction first sets in. At very high energies, where the gyroradius of accelerated particles becomes comparable to the outer scale of the turbulence, the energy spectrum can display an even harder spectrum with $s\sim 1.3–1.5$ over a short segment. The low-energy part of the spectrum, below the critical momentum, is expected to be hard ($s\sim 1$ or harder), and shaped by any residual acceleration process in the damped region of the turbulence cascade. This characteristic broken power-law shape with $s\sim 2$ at high energies may find phenomenological applications in various high-energy astrophysical contexts.

We investigate the $P$-wave states $T_{bb}^{-}$ in the isospin singlet and three excited modes [excitation occurring in the diquark $[bb{]}_{c_1}^{s_1}$ ($\rho$-mode), antidiquark $[\overline{u}\overline{d}{]}_{c_2}^{s_2}$ ($r$-mode), or between them ($\lambda$-mode)] from diquarks in a quark model. We analyze the dynamical behaviors of the diquark $[bb{]}_{c_1}^{s_1}$, antidiquark $[\overline{u}\overline{d}{]}_{c_2}^{s_2}$, and their correlations in the states $T_{bb}^{-}$ by decomposing the interactions from various sources in the model. The absolute dominant color-spin configuration, more than 99%, in the $\rho$-mode with $1{{}^{1}P}_1$ is $[bb{]}_{\overline{\mathbf{3}}}^0[\overline{u}\overline{d}{]}_{\mathbf{3}}^0$. Its energy is lower by about 18 MeV than the threshold $\overline{B}\overline{B}$ so that it can establish a compact bound state. The chromomagnetic and meson-exchange interactions in the antidiquark $[\overline{u}\overline{d}{]}_{\mathbf{3}}^0$ are responsible for its binding mechanism. Two other excited modes are higher than their respective threshold. The color configuration $\mathbf{6}\otimes \overline{\mathbf{6}}$ need to be handled discreetly in the tetraquark states.

We present an analysis of the heavy quark structure functions from the $k_t$ factorization scheme, using unifying the color dipole picture and double asymptotic scaling approaches at small $x$. The gluon distribution is obtained from the Golec-Biernat-Wüsthoff and Bartels, Golec-Biernat and Kowalski models. The main elements are based on the color dipole picture and the generalized double asymptotic scaling approach for usual parton distribution functions. The comparisons with the HERA data are made and predictions for the proposed LHeC and FCC-he colliders are also provided in a wide range of the transverse separation $r$. In particular, the ratio $R^h=F_L^h/F_2^h,h=c,b,t$ is well described by the dipole models and is sensitive to the collider energies from HERA until FCC-he. We derive correlated bounds on the ratio $F_2^c/F_2$ and $F_2^b/F_2$ and compared them with the BGK and impact-parameter dependent saturation models. The uncertainties are due to the renormalization and factorization scales at large and low $r$ values. The Sudakov form factor into the heavy quark structure functions is incorporated and the results are considered, which are dependent on the hard scale in a wide range of the transverse separation $r$.

The creation of a quark-gluon plasma (QGP) is expected in heavy-ion collisions. It came as a surprise that proton-proton collisions at ultrarelativistic energies show as well a “QGP-like” behavior and signs of the creation of a fluid, although the corresponding system size is not more than a few cubic femtometers. Even more surprisingly, also heavy-flavor particles seem to be part of the fluid or at least interact with it. In this paper, we will investigate in a quantitative way this “collective behavior” of heavy flavor, by employing the newly developed EPOS4HQ approach, which has proven to be compatible with basic experimental data of light-flavor hadrons. We will investigate all observables, which may manifest collectivity, as particle spectra, elliptic flow, baryon-to-meson ratios, and two-particle correlations, and compare the results with experimental data. We will try to disentangle initial-state effects, those being due to interactions between charm quarks and plasma partons, and final-state effects (hadronization).

We revisit the application of the Froissart-Gribov (FG) projections in the analysis of amplitudes for deeply virtual Compton scattering (DVCS), providing essential information on generalized parton distributions (GPDs). The pivotal role of these projections in a systematic description of a hadron’s response to the stringlike QCD probes characterized by different values of angular momentum $J$ is emphasised. For the first time, we establish a relationship between the FG projections and GPDs for spin-½ targets, and we investigate these quantities in various GPD models. Finally, we provide the first numerical estimates for the FG projections based on the DVCS amplitudes directly extracted from experimental data. We argue the method of the FG projections deserves a broad application in the DVCS phenomenology.

Choosing which properties of the data to use as input to multivariate decision algorithms—also known as feature selection—is an important step in solving any problem with machine learning. While there is a clear trend towards training sophisticated deep networks on large numbers of relatively unprocessed inputs (so-called automated feature engineering), for many tasks in physics, sets of theoretically well-motivated and well-understood features already exist. Working with such features can bring many benefits, including greater interpretability, reduced training and run time, and enhanced stability and robustness. We develop a new feature selection method based on distance correlation, and demonstrate its effectiveness on the tasks of boosted top- and $W$-tagging. Using our method to select features from a set of over 7,000 energy flow polynomials, we show that we can match the performance of much deeper architectures, by using only ten features and two orders-of-magnitude fewer model parameters.

The Cabbibo-favored decay ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Xi }}^0{K}^{+}{\pi }^0$ is studied for the first time using $6.1{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Xi }}^0{K}^{+}{\pi }^0$ is measured to be $(7.79\pm 1.46\pm 0.95)\times {10}^{-3}$, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Xi }(1530{)}^0{K}^{+}$ is $(5.99\pm 1.04\pm 0.32)\times {10}^{-3}$, which is consistent with the previous result of $(5.02\pm 0.99\pm 0.31)\times {10}^{-3}$. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to n{K}^{+}{\pi }^0$ is $7.1\times {10}^{-4}$ at the 90% confidence level. The upper limits on the branching fractions of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{K}^{+}{\pi }^0$ and $\mathrm{\Lambda }{K}^{+}{\pi }^0$ are also determined to be $1.8\times {10}^{-3}$ and $2.0\times {10}^{-3}$, respectively.

We propose a holographic dictionary which comes from reducing the bulk theories in an asymptotically flat spacetime to its null infinity. A general boundary theory is characterized by a fundamental field, an infinite tower of descendant fields, constraints among the fundamental field and its descendants, as well as a symplectic form. For the Carrollian diffeomorphisms, we can construct the corresponding Hamiltonians which are also the fluxes from the bulk, and whose quantum operators realize this algebra with a divergent central charge. This central charge reflects the propagating degrees of freedom and can be regularized. For the spinning theory, we need a helicity flux operator to close the algebra which relates to the duality transformation.

Modifications to the Mukhanov-Sasaki equation in loop quantum cosmology (LQC) have been phenomenologically explored using polymerization of the connection and related variables in the classical expressions in order to capture the quantum gravity effects in cosmological perturbations which replace the classical big bang by a big bounce. Examples of this strategy include the dressed metric and the hybrid approaches whose interrelationship at an effective level was demonstrated by the authors recently. In this manuscript, we propose a new family of the effective mass functions in the modified Mukhanov-Sasaki equation of LQC by investigating the polymerization of a particular form of the classical mass function in terms of variable $z_s(=a\dot{\varphi }/H)$ which relates the Mukhanov-Sasaki variable with the comoving curvature perturbation. Using a generalized Ansatz motivated by quantum gravity effects in the background dynamics we find alternative effective mass functions which are distinct from those used in the dressed metric and the hybrid approaches with differences originating from the noncommutativity of the evaluation of the Poisson brackets and the polymerization procedures. The new effective mass functions acquire four correction terms in the effective potential whose exact forms are closely tied up with the Ansatz used for polymerizing the inverse Hubble rate. In contrast to earlier works, one of these correction terms can in principle produce sizable effects even when the bounce is kinetic dominated. Our investigation opens a new window to explore the phenomenological implications of a large family of effective mass functions in LQC which can potentially lead to significant departures from the dressed metric and the hybrid approaches in the bounce regime.

We consider the $d$-wave holographic superconductor model with full backreaction on the metric, addressing a missing part in the literature. We have identified the gap function by comparing the fermionic spectral function with the momentum-dependent order parameter. By numerical investigations of the fermionic spectral function in the presence of a tensor condensate, we find the Fermi arc and the gapped behavior, which closely resembles angle resolved photoemission spectrum data. Moreover, we have examined the influence of the coupling constant, chemical potential, and temperature on the spectral function. We find that $d$-wave fermionic spectral function can be obtained through $p_x$ and $p_y$ condensates combined with two fermion flavors. Similarly, combining $d_{x^2-y^2}$ and $d_{xy}$ orbitals symmetry with two fermion flavors leads to a $g$-wave spectral function.

Chiral form fields in $d$ dimensions can be effectively described as edge modes of topological Chern-Simons theories in $d+1$ dimensions. At the same time, manifestly Lorentz-invariant Lagrangian description of such fields directly in terms of a $d$-dimensional field theory is challenging and requires introducing nontrivial auxiliary gauge fields eliminated on shell with extra gauge symmetries. A recent work by Arvanitakis et al. demonstrates (emphasizing the case of 2d chiral bosons) that the two approaches are related, and a peculiar reduction on the ($d+1$)-dimensional topological Lagrangian automatically leads to $d$-dimensional Lagrangians with appropriate sets of auxiliary fields. We develop this setup in three distinct directions. First, we demonstrate how arbitrary Abelian self-interactions for chiral forms can be included using nonlinear boundary terms in the Chern-Simons theory. Second, by generalizing the Chern-Simons theory to the BF-theory, we obtain an analogous democratic description of nonchiral form fields, where electric and magnetic potentials appear as explicit dynamical variables. Third, we discuss the effects of introducing topological interactions in the higher-dimensional bulk, which produce extra interaction terms in the boundary theory. When applied to a topological 4-form field in 12 dimensions, this construction results in a democratic description of the 3-form gauge field of the eleven-dimensional supergravity.