Through a series of simulated observations, we investigate the capability of the instruments aboard the forthcoming THESEUS mission for the detection of a characteristic signal from decaying dark matter (DM) in the keV-MeV energy range. We focus our studies on three well studied Standard Model extensions hosting axionlike particles, dark photon, and sterile neutrino DM candidates. We show that, due to the sensitivity of THESEUS’ x and gamma imaging spectrometer instrument, existing constraints on dark matter parameters can be improved by a factor of up to $\sim 300$, depending on the considered DM model and assuming a zero level of systematic uncertainty. We also show that even a minimal level of systematic uncertainty of 1% can impair potential constraints by one to two orders of magnitude. We argue that nonetheless, the constraints imposed by THESEUS will be substantially better than existing ones and will well complement the constraints of upcoming missions such as eXTP and Athena. Ultimately, the limits imposed by THESEUS and future missions will ensure a robust and thorough coverage of the parameter space for decaying DM models, enabling either a detection of dark matter or a significant improvement of relevant limits.

Dark matter can capture in neutron stars from scattering off ultrarelativistic electrons. We present a method to calculate the capture rate on degenerate targets with ultrarelativistic momenta in a compact astronomical object. Our treatment accounts for the target momentum and the Fermi degeneracy of the system. We derive scaling relations for scattering with relativistic targets and confirm consistency with the nonrelativistic limit and Lorentz invariance. The potential observation of kinetic heating of neutron stars has a larger discovery reach for dark matter–lepton interactions than conventional terrestrial direct detection experiments. We map this reach onto a set of bosonic and fermionic effective contact interactions between dark matter and leptons as well as nucleons. We show the results for the contact operators up to dimension-six for spin-0 and spin-$1/2$ dark matter interactions with relativistic as well as nonrelativistic Standard Model fermions. Highlights of this program in the case of vector mediated interactions are presented in a companion article [Joglekar et al., Phys. Lett. B 809, 135767 (2020)]. Our method is generalizable to dark matter scattering in any degenerate medium where the Pauli exclusion principle leads to relativistic targets with a constrained phase space for scattering.

The present article investigates the impact of muons on core-collapse supernovae, with particular focus on the early muon neutrino emission. While the presence of muons is well understood in the context of neutron stars, until the recent study by Bollig et al. [Phys. Rev. Lett. 119, 242702 (2017) the role of muons in core-collapse supernovae had been neglected—electrons and neutrinos were the only leptons considered. In their study, Bollig et al. disentangled the muon and tau neutrinos and antineutrinos and included a variety of muonic weak reactions, all of which the present paper follows closely. Only then does it becomes possible to quantify the appearance of muons shortly before stellar core bounce and how the postbounce prompt neutrino emission is modified.

Key to the exact solubility of the unitary minimal models in two-dimensional conformal field theory is the organization of their Hilbert space into Verma modules, whereby all eigenstates of the Hamiltonian are obtained by the repeated action of Virasoro lowering operators onto a finite set of highest-weight states. The usual representation-theoretic approach to removing from all modules zero-norm descendant states generated in such a way is based on the assumption that those states form a nested sequence of Verma submodules built upon singular vectors, i.e., descendant highest-weight states. We show that this fundamental assumption breaks down for the Ramond-sector Verma module with highest weight $c/24$ in the even series of $\mathcal{N}=1$ superconformal minimal models with central charge $c$. To resolve this impasse, we conjecture, and prove at low orders, the existence of a nested sequence of linear-dependence relations that enables us to compute the character of the irreducible $c/24$ module. Based on this character formula, we argue that imposing modular invariance of the torus partition function requires the introduction of a non-null odd-parity Ramond-sector ground state. This symmetrization of the ground-state manifold allows us to uncover a set of conformally invariant boundary conditions not previously discussed and absent in the odd series of superconformal minimal models, and to derive for the first time a complete set of fusion rules for the even series of those models.

Scalar fields in the minimal supersymmetric standard model may have large field values during inflation. Because of approximate global symmetry, it is plausible that the phase directions of them are nearly massless during inflation and obtain quantum fluctuations, which may be the origin of the cosmic perturbations. If perturbations are produced through Q-ball formation, baryon asymmetry and dark matter can be consistently generated. Significant baryon and dark matter isocurvature perturbations are produced, but they are predicted to nearly compensate each other. The lepton asymmetry is much larger than the baryon asymmetry. The scenario predicts local non-Gaussianity of $f_{\mathrm{NL}}=5/3$. The implication to the mass spectrum of supersymmetric particles is discussed.

We compute the vacuum polarization energy of kink solitons in the ${\varphi }^8$ model in one space and one time dimensions. There are three possible field potentials that have eight powers of $\varphi$ and that possess kink solitons. For these different field potentials we investigate whether the vacuum polarization destabilizes the solitons. This may particularly be the case for those potentials that have degenerate ground states with different curvatures in field space yielding different thresholds for the quantum fluctuations about the solitons at negative and positive spatial infinity. We find that destabilization occurs in some cases, but this is not purely a matter of the field potential but also depends on the realized soliton solution for that potential. One of the possible field potentials has solitons with different topological charges. In that case the classical mass approximately scales like the topological charge. Even though destabilization precludes robust statements, there are indications that the vacuum polarization energy does not scale as the topological charge.

Loop-induced $ZZ$ production can be enhanced by the large gluon flux at the LHC, and thus should be taken into account in relevant experimental analyses. We present for the first time the results of a fully exclusive simulation based on the matrix elements for loop-induced $ZZ+0$, 1, 2-parton processes at leading order, matched to parton showers. The new description is studied and validated by comparing it with well-established simulation with jets from parton showers. We find that the matched simulation provides a state-of-the-art description of the final-state jets. We also briefly discuss the physics impact on vector boson scattering measurements at the LHC, where event yields are found to be smaller by about 40% in a vector boson scattering $ZZjj$ baseline search region, compared to previous simulations. We hence advocate relevant analyses to employ a more accurate jet description for the modeling of the loop-induced process.

We consider quantum phase transitions with global symmetry breakings that result in the formation of topological defects. We evaluate the number densities of kinks, vortices, and monopoles that are produced in $d=1$, 2, 3 spatial dimensions, respectively, and find that they scale as $t^{-d/2}$ and evolve toward attractor solutions that are independent of the quench timescale. For $d=1$ our results apply in the region of parameters $\lambda \tau /m\ll 1$ where $\lambda$ is the quartic self-interaction of the order parameter, $\tau$ is the quench timescale, and $m$ is the mass parameter.

We calculate the $T$ matrices of elastic pion-nucleon ($\pi N$) scattering up to fourth order in SU(3) heavy baryon chiral perturbation theory. The pertinent low-energy constants are determined by fitting to $\pi N$ phase shifts below the 200 MeV pion laboratory momentum in the physical region. The scattering lengths and scattering volumes are extracted from the chiral amplitudes, and turn out to be in good agreement with those of other approaches and the available experimental values. We also discuss the subthreshold parameters and the related issues. On the basis of the various phase shifts, the threshold parameters and the subthreshold parameters, the convergence of the chiral expansion is analyzed in detail. The calculation provides the possibility to consider explicitly more complex processes involving strangeness.

We construct anomaly-free $U(1{)}_1\times U(1{)}_2\times \dots \times U(1{)}_m$ gauge extensions of the Standard Model. To perform this construction, we put together anomaly-free $U(1)$ extensions of one and two families of fermions. The availability of free parameters that enter linearly in the equations for the fermion charges and the large number of different classes of extensions may help other model builders interested in their use to solve problems of particle physics.

The recent measurements of the cosmological parameter $H_0$ from the direct local observations and the inferred value from the cosmic microwave background show approximately $4\sigma$ discrepancy. This may indicate new physics beyond the standard $\mathrm{\Lambda }\mathrm{CDM}$. We investigate the keV gravitino dark matter that has a small fraction of nonthermal components (e.g., from the late decay of next-to-lightest-supersymmetric-particle bino) under various cosmological constraints. We find such a scenario is highly predictive and can be tested by searching for the dilepton plus missing energy events at the LHC. Besides, we also discuss its implication for Hubble tension, which can be reduced to $3\sigma$ level marginally.

Non-Abelian discrete symmetries provide an interesting opportunity to address the flavor puzzle in the lepton sector. However, the number of currently viable models based on such symmetries is rather large. High-precision measurements of the leptonic mixing parameters by future neutrino experiments, including ESSnuSB, T2HK, DUNE, and JUNO, will be crucial to test such models. We show that the complementarity among these experiments offers a powerful tool for narrowing down this broad class of lepton flavor models.

Neutrinos undergoing stochastic perturbations as they propagate experience decoherence, damping neutrino oscillations over distance. Such perturbations may result from fluctuations in space-time itself if gravity is a quantum force, including interactions between neutrinos and virtual black holes. In this work we model the influence of heuristic neutrino-virtual black hole interaction scenarios on neutrino propagation and evaluate the resulting signals in astrophysical and atmospheric neutrinos. We derive decoherence operators representing these effects in the framework of open quantum systems, allowing experimental constraints on such systems to be connected to quantum gravitational effects. Finally, we consider the energy-dependence of such Planck scale physics at energies observed in current neutrino experiments, and show that sensitivity to Planck scale physics well below the “natural” expectation is achievable in certain scenarios.

In two Higgs doublet models (2HDMs) shaped by some unbroken symmetry, imposing perturbativity requirements on the quartic couplings can imply that the allowed masses of all the fundamental scalars are bounded from above. This important property is analyzed in detail for the only two realistic 2HDMs with an exact symmetry, the case with ${\mathbb{Z}}_2$ symmetry and the case with $CP$ symmetry. It is also noticeable that one exception arises in each case: when the vacuum is assumed to respect the imposed symmetry, a decoupling regime can nevertheless appear without violating perturbativity requirements. In both models with an exact symmetry and no decoupling regime, soft symmetry breaking terms can however lead to a decoupling regime: the possibility that this regime might be unnatural, since it requires some fine-tuning, is also analyzed.

Motivated by models proposed to explain Standard Model anomalies, and the unprecedented ${\tau }^{+}{\tau }^{-}$ data to be collected by the Belle II experiment during the next years, we study the kinematics of tau pair decays and propose a new method to search for lepton flavor violating processes in tau lepton decays to invisible beyond Standard Model particles, such as $\tau \to \ell \alpha$, where $\ell$ is either an electron or a muon, and $\alpha$ is a massive particle that escapes undetected. The new method improves by one order of magnitude the expected upper limit on the $\tau \to \ell \alpha$ production in $3\times 1$ prong tau decays and establishes the possibility of performing this search in $1\times 1$ prong tau decays which has not been previously considered.

We study strong and radiative decays of excited singly heavy baryons (SHBs) using an effective chiral Lagrangian based on the diquark picture proposed in Ref. [1]. The effective Lagrangian contains a $U_A(1)$ anomaly term, which induces an inverse mass ordering between strange and nonstrange SHBs with spin-parity $1/2^{-}$. We find that the effect of the $U_A(1)$ anomaly combined with flavor symmetry breaking modifies the Goldberger-Treiman relation for the mass difference between the ground state ${\mathrm{\Lambda }}_Q(1/2^{+})$ and its chiral partner ${\mathrm{\Lambda }}_Q(1/2^{-})$, and ${\mathrm{\Lambda }}_Q(1/2^{-}){\mathrm{\Lambda }}_Q(1/2^{+})\eta$ coupling, which results in suppression of the decay width of ${\mathrm{\Lambda }}_Q(1/2^{-})\to {\mathrm{\Lambda }}_Q(1/2^{+})\eta$. We also investigate the other various decays such as ${\mathrm{\Lambda }}_Q(1/2^{-})\to {\mathrm{\Sigma }}_Q(1/2^{+},3/2^{+})\pi \pi$, ${\mathrm{\Lambda }}_Q(1/2^{-})\to {\mathrm{\Sigma }}_Q(1/2^{+})\pi$, ${\mathrm{\Lambda }}_Q(1/2^{-})\to {\mathrm{\Sigma }}_Q(1/2^{+},3/2^{+})\gamma$, and ${\mathrm{\Lambda }}_Q(1/2^{-})\to {\mathrm{\Lambda }}_Q(1/2^{+}){\pi }^0$ for a wide mass range of ${\mathrm{\Lambda }}_Q(1/2^{-})$.

We present a study of the central exclusive diffractive production of the $f_1(1285)$ and $f_1(1420)$ resonances in proton-proton collisions. The theoretical results are calculated within the tensor-pomeron approach. Two pomeron-pomeron-$f_1$ tensorial couplings labeled by $(l,S)=(2,2)$ and (4,4) are derived. We adjust the model parameters (coupling constants, cutoff constant) to the WA102 experimental data taking into account absorption effects. Both the $(l,S)=(2,2)$ and (4,4) couplings separately allow one to describe the WA102 differential distributions. We compare these predictions with those of the Sakai-Sugimoto model, where the pomeron-pomeron-$f_1$ couplings are determined by the mixed axial-gravitational anomaly of QCD. We derive an approximate relation between the pomeron-pomeron-$f_1$ coupling constants of this approach and the $(l,S)=(2,2)$ and (4,4) couplings. Then we present our predictions for the energies available at the RHIC and LHC. The total cross sections and several differential distributions are presented. Analysis of the distributions in the azimuthal angle ${\varphi }_{pp}$ between the transverse momenta of the outgoing protons may be used to disentangle $f_1$- and $\eta$-type resonances contributing to the same final channel. We find for the $f_1(1285)$ a total cross section $\sim 38$ $\mu \mathrm{b}$ for $\sqrt{s}=13\mathrm{TeV}$ and a rapidity cut on the $f_1$ of $|{\mathrm{y}}_{\mathrm{M}}|<2.5$. We predict a much larger cross section for production of $f_1(1285)$ than for production of $f_2(1270)$ in the ${\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ decay channel for the LHC energies. This opens a possibility to study the $f_1(1285)$ meson in experiments planned at the LHC.

In this work, a covariant formulation of the gluon self-energy in presence of ellipsoidal anisotropy is considered. It is shown that the general structure of the gluon self-energy can be written in terms of six linearly independent projection tensors. Similar to the spheroidal anisotropy, mass scales can be introduced for each of the collective modes considering the static limits. With a simplified ellipsoidal generalization of the Romatschke-Strickland form, the angular dependencies of the mass scales are studied. It is observed that, compared to the spheroidal case, additional unstable mode may appear in presence of ellipsoidal anisotropy depending upon the choice of the parameters.

We study the properties of fully-heavy tetraquarks at finite temperature and their production in high-energy nuclear collisions. We obtain the masses and wave functions of the exotic hadron states $cc\overline{c}\overline{c}$ and $bb\overline{b}\overline{b}$ by solving the four-body Schrödinger equation in vacuum and strongly interacting matter. In vacuum, the tetraquarks are above the corresponding meson-meson mass threshold, and the newly observed exotic state $X(6900)$ might be a $cc\overline{c}\overline{c}$ state with quantum number $J^{PC}=0^{++}$ or $1^{+-}$. In hot medium, the temperature dependence of the tetraquark masses and the dissociation temperatures are calculated. Taking the wave function at finite temperature, we construct the Wigner function for the tetraquark states and calculate, with coalescence mechanism, the production yield and transverse momentum distribution of $cc\overline{c}\overline{c}$ in heavy-ion collisions at LHC energy. In comparison with nucleon-nucleon collisions, the yield per binary collision is significantly enhanced.

We present a comprehensive analysis of electronic recoil vs nuclear recoil discrimination in liquid/gas xenon time projection chambers, using calibration data from the 2013 and 2014–2016 runs of the Large Underground Xenon experiment. We observe strong charge-to-light discrimination enhancement with increased event energy. For events with $\mathrm{S}1=120$ detected photons, i.e., equivalent to a nuclear recoil energy of $\sim 100\mathrm{keV}$, we observe an electronic recoil background acceptance of $<{10}^{-5}$ at a nuclear recoil signal acceptance of 50%. We also observe modest electric field dependence of the discrimination power, which peaks at a field of around $300\mathrm{V}/\mathrm{cm}$ over the range of fields explored in this study ($50–500\mathrm{V}/\mathrm{cm}$). In the weakly interacting massive particle search region of $\mathrm{S}1=1-80\mathrm{phd}$, the minimum electronic recoil leakage we observe is $(7.3\pm 0.6)\times {10}^{-4}$, which is obtained for a drift field of $240–290\mathrm{V}/\mathrm{cm}$. Pulse shape discrimination is utilized to improve our results, and we find that, at low energies and low fields, there is an additional reduction in background leakage by a factor of up to 3. We develop an empirical model for recombination fluctuations which, when used alongside the Noble Element Scintillation Technique simulation package, correctly reproduces the skewness of the electronic recoil data. We use this updated simulation to study the width of the electronic recoil band, finding that its dominant contribution comes from electron-ion recombination fluctuations, followed in magnitude of contribution by fluctuations in the S1 signal, fluctuations in the S2 signal, and fluctuations in the total number of quanta produced for a given energy deposition.