We analyze the impact of several multiquark interaction channels on the properties of hybrid stars. Four and eight vector interactions were included in the $SU(3)$ Nambu–Jona-Lasinio model to describe the quark matter, and all vectorlike interactions were investigated. The hybrid stars were built starting from an hadronic equation of state that satisfy presently accepted nuclear matter properties and considering the quark model constrained by the vacuum properties of several light mesons. The interplay between the eight-quark vector interaction and the four-quark isovector-vector interaction determine the size of the quark core and its strangeness content. The inclusion of a isovector-vector interaction is essential to obtain large $s$-quark contents and a smaller central speed of sound, although this interaction pushes the onset of quarks to larger densities. It is observed that low mass stars, with a mass below $1.4M_{\odot }$, may contain a quark core but with a small strangeness content. It is shown that the presently existing mass and tidal deformability constraints from neutron stars observations allow for the existence of hybrid stars with a large strangeness content and large quark cores for binary mass ratios $q=M_2/M_1\gtrsim 0.85$.

Relic neutrinos from the big bang decoupled from the hot plasma predominantly in helicity eigenstates. Their subsequent propagation through gravitational inhomogeneities of the Universe alters the helicities of both Dirac and Majorana neutrinos, thus providing an independent probe of the evolving Universe. We determine here the probability that relic neutrinos flip their helicity, in terms of the spectrum of density inhomogeneities measured in the cosmic microwave background. As we find, for Dirac neutrinos the gravitational helicity modifications are intermediate between the effects of magnetic fields if the neutrino magnetic moment is of the magnitude predicted in the standard model and the much larger effects if the magnetic moment is of the scale consistent with the excess of low energy electron events seen by the XENON1T experiment. We give succinct derivations, within general relativity, of the semiclassical response of a spinning particle to a weak gravitational field in an expanding Universe and estimate the helicity modifications of neutrinos emitted by the Sun caused by the Sun’s gravity.

The Large Underground Xenon (LUX) dark matter search was a 250-kg active mass dual-phase time projection chamber that operated by detecting light and ionization signals from particles incident on a xenon target. In December 2015, LUX reported a minimum 90% upper C.L. of $6\times {10}^{-46}{\mathrm{cm}}^2$ on the spin-independent WIMP-nucleon elastic scattering cross section based on a $1.4\times {10}^4\mathrm{kg}·\mathrm{day}$ exposure in its first science run. Tension between experiments and the absence of a definitive positive detection suggest it would be prudent to search for WIMPs outside the standard spin-independent/spin-dependent paradigm. Recent theoretical work has identified a complete basis of 14 independent effective field theory (EFT) operators to describe WIMP-nucleon interactions. In addition to spin-independent and spin-dependent nuclear responses, these operators can produce novel responses such as angular-momentum-dependent and spin-orbit couplings. Here we report on a search for all 14 of these EFT couplings with data from LUX’s first science run. Limits are placed on each coupling as a function of WIMP mass.

By looking at the pseudoscalar-vector meson spectra in the $\overline{B}\to J/\psi \rho \overline{K}$ and $\overline{B}\to J/\psi {\overline{K}}^{*}\pi$ weak decays, we theoretically investigate the double-pole structure of the $K_1(1270)$ resonance by using the chiral unitary approach to account for the final-state interactions between the pseudoscalar ($P$) and vector ($V$) mesons. The $K_1(1270)$ resonance is dynamically generated through these interactions in coupled channels and influences the shape of the invariant mass distributions under consideration. We show how these shapes are affected by the $K_1(1270)$ double-pole structure to confront the results from our model with future experiments that might investigate the $PV$ spectra in these decays.

We first demonstrate theoretically that the computational quantum field theory is equivalent to the quantum kinetic theory for pair creation in a spatially homogeneous and time-dependent electric field, then verify numerically their equivalence for pair creation in one-dimensional time-dependent electric fields, and finally investigate detailedly the effects of the field frequency, spatial width, pulse duration, and relative phase on dynamically assisted Schwinger pair production in an inhomogeneous two-color electric field. It is found that the enhancement effect of pair creation is very sensitive to the field frequency and generally very obvious for a shorter field width, a longer pulse duration, and a relative phase of maximizing the field strength. These results can provide a significant reference for the optimal control theory of pair creation which aims to maximize the created pair yield within a given scope of field parameters.

We perform a systematic study on the interactions of the ${\mathrm{\Sigma }}_c^{(*)}{D}^{(*)}$ systems within the framework of chiral effective field theory. We introduce the contact term, one-pion-exchange and two-pion-exchange contributions to describe the short-, long-, and intermediate-range interactions. The low energy constants of the ${\mathrm{\Sigma }}_c^{(*)}{D}^{(*)}$ systems are estimated from the $N\overline{N}$ scattering data by introducing a quark level Lagrangian. With three solutions of LECs, all the ${\mathrm{\Sigma }}_c^{(*)}{D}^{(*)}$ systems with isospin $I=1/2$ can form bound states, in which different inputs of LECs may lead to distinguishable mass spectra. In addition, we also investigate the interactions of the charmed-bottom ${\mathrm{\Sigma }}_c^{(*)}{\overline{B}}^{(*)}$, ${\mathrm{\Sigma }}_b^{(*)}{D}^{(*)}$, and ${\mathrm{\Sigma }}_b^{(*)}{\overline{B}}^{(*)}$ systems. Among the obtained bound states, the bindings become deeper when the reduced masses of the corresponding systems are heavier.

Particle production by expanding in the future light cone scalar quantum field is studied by assuming that the initial state is associated with the quasiequilibrium statistical operator corresponding to fluid dynamics. We calculate particle production from a longitudinally boost-invariant expanding quantum field designed as a simple but reliable model for the central rapidity region of a relativistic collision. Exact diagonalization of the model is performed by introducing a notion of quasiparticles.

We investigate a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. For this the minimal supersymmetric Standard Model is extended by adding light right-handed neutrinos and their superpartners, the R-sneutrinos. Moreover, we consider the lightest neutralinos to be Higgsino-like. We first update a previous analysis and assess to which extent does existing LHC data constrain the allowed slepton masses. Here we find scenarios where sleptons with masses as low as 175 GeV are consistent with existing data. However, we also show that the upcoming run will either discover or rule out sleptons with masses of 300 GeV, even for these challenging scenarios. We then take a scenario which is on the borderline of observability of the upcoming LHC run assuming a luminosity of $300{\mathrm{fb}}^{-1}$. We demonstrate that a prospective international $e^{+}{e}^{-}$ linear collider with a center of mass energy of 1 TeV will be able to discover sleptons in scenarios which are difficult for the LHC. Moreover, we also show that a measurement of the spectrum will be possible within 1–3 percent accuracy.

We investigate effects of nonzero Dirac and Majorana $CP$-violating phases on neutrino-antineutrino oscillations in a magnetic field of astrophysical environments. It is shown that in the presence of strong magnetic fields and dense matter, nonzero $CP$ phases can induce new resonances in the oscillations channels ${\nu }_e\leftrightarrow {\overline{\nu }}_e$, ${\nu }_e\leftrightarrow {\overline{\nu }}_{\mu }$, and ${\nu }_e\leftrightarrow {\overline{\nu }}_{\tau }$. We also consider all other possible oscillation channels with ${\nu }_{\mu }$ and ${\nu }_{\tau }$ in the initial state. The resonances can potentially lead to significant phenomena in neutrino oscillations accessible for observation in experiments. In particular, we show that neutrino-antineutrino oscillations combined with Majorana-type $CP$ violation can affect the ${\overline{\nu }}_e/{\nu }_e$ ratio for neutrinos coming from the supernovae explosion. This effect is more prominent for the normal neutrino mass ordering. The detection of supernovae neutrino fluxes in the future experiments, such as JUNO, DUNE, and Hyper-Kamiokande, can give an insight into the nature of $CP$ violation and, consequently, provides a tool for distinguishing the Dirac or Majorana nature of neutrinos.

We present a new calculation of next-to-leading order QCD corrections to electroweak top-quark pair hadroproduction in extensions of the Standard Model (SM) with extra heavy neutral and charged spin-1 resonances which considerably extends and improves an earlier calculation performed by some of us. In particular, we allow for flavor-non-diagonal $Z^{\prime }$ couplings and take into account nonresonant production in the SM and beyond including the contributions with $t$-channel $W$ and $W^{\prime }$ bosons. As a result, models with a more complicated flavor structure which have been proposed to explain the flavor anomalies in $B$ decays can now be accommodated in our code. Moreover, the new $t$-channel contributions lead to improved cross sections predictions at higher energies beyond the LHC reach. All amplitudes are generated using the recola2 package. As in our previous work, we include next-to-leading order QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interference effects between the SM and new physics amplitudes. We consider the sequential Standard Model, the topcolor model, as well as the third family hypercharge model featuring non-flavor-diagonal $Z^{\prime }$ couplings and present numerical results for $t\overline{t}$ cross sections at hadron colliders with a center-of-mass energy up to 100 TeV.

Local minima of the potential can be metastable up to cosmologically long times thanks to energy conservation. We explore the possibility that theories with negative kinetic energy (ghosts) can be metastable up to cosmologically long times. In classical mechanics, ghosts undergo spontaneous lockdown rather than run away if weakly coupled and nonresonant. Physical examples of this phenomenon are shown. In quantum mechanics, this leads to metastability similar to vacuum decay. In classical field theory, lockdown is broken by resonances and ghosts behave statistically, drifting toward infinite entropy as no thermal equilibrium exists. We analytically and numerically compute the runaway rate finding that it is cosmologically slow in four-derivative gravity, where ghosts have gravitational interactions only. In quantum field theory, the ghost runaway rate is naively infinite in perturbation theory, analogously to what is found in early attempts to compute vacuum tunnelling; we do not know the true rate.

We study an extended 2 Higgs doublet model (2HDM) in which the Standard Model (SM) Yukawa interactions are forbidden due to a global $U(1{)}^{\prime }$ symmetry, but may arise via mixing with vectorlike families. In this model, the hierarchical structure of Yukawa couplings of quarks and leptons in the SM arises from the heavy masses of the fourth and fifth vectorlike families. Within this model, we consider various nonstandard contributions to the electron and muon anomalous magnetic moments. We first consider the $W$ exchange at one-loop level, consistent with the $\mu \to e\gamma$ constraint, and show that it yields a negligible contribution to both electron and muon anomalous magnetic moments. We then consider Higgs scalar exchange, together with vectorlike leptons, at one-loop level and show that it is possible to have nonstandard contributions to the electron and muon anomalous magnetic moments within the $1\sigma$ constraint of certain experiments. We present some benchmark points for both the muon and the electron anomalies, together with some numerical scans around these points, which indicate the mass regions of the Higgs scalars of the 2HDM in this scenario.

We show how the sphaleron rate (the Minkowski rate for topological charge diffusion) can be determined by analytical continuation of the Euclidean topological-charge-density two-point function, which we investigate on the lattice, using gradient flow to reduce noise and provide improved operators which more accurately measure topology. We measure the correlators on large, fine lattices in the quenched approximation at $1.5T_c$ with high precision. Based on these data we first perform a continuum extrapolation at fixed physical flow time and then extrapolate the continuum estimates to zero flow time. The extrapolated correlators are then used to study the sphaleron rate by spectral reconstruction based on perturbatively motivated models.

This work explores scattering amplitudes that couple two-particle systems via a single external current insertion, $2+\mathcal{J}\to 2$. Such amplitudes can provide structural information about the excited QCD spectrum. We derive an exact analytic representation for these reactions. From these amplitudes, we show how to rigorously define resonance and bound-state form factors. Furthermore, we explore the consequences of the narrow-width limit of the amplitudes as well as the role of the Ward-Takahashi identity for conserved vector currents. These results hold for any number of two-body channels with no intrinsic spin, and a current with arbitrary Lorentz structure and quantum numbers. This work and the existing finite-volume formalism provide a complete framework for determining this class of amplitudes from lattice QCD.

We study scalar fields propagating on Euclidean dynamical triangulations (EDTs). In this work, we study the interaction of two scalar particles, and we show that in the appropriate limit we recover an interaction compatible with Newton’s gravitational potential in four dimensions. Working in the quenched approximation, we calculate the binding energy of a two-particle bound state, and we study its dependence on the constituent particle mass in the nonrelativistic limit. We find a binding energy compatible with what one expects for the ground state energy by solving the Schrödinger equation for Newton’s potential. Agreement with this expectation is obtained in the infinite-volume, continuum limit of the lattice calculation, providing nontrivial evidence that EDT is in fact a theory of gravity in four dimensions. Furthermore, this result allows us to determine the lattice spacing within an EDT calculation for the first time, and we find that the various lattice spacings are smaller than the Planck length, suggesting that we can achieve a separation of scales and that there is no obstacle to taking a continuum limit. This lends further support to the asymptotic safety scenario for gravity.

We present a data-driven analysis of the resonant $S$-wave $\pi \pi \to \pi \pi$ and $\pi K\to \pi K$ reactions using the partial-wave dispersion relation. The contributions from the left-hand cuts are accounted for using the Taylor expansion in a suitably constructed conformal variable. The fits are performed to experimental and lattice data as well as Roy analyses. For the $\pi \pi$ scattering we present both a single- and a coupled-channel analysis by including additionally the $K\overline{K}$ channel. For the latter the central result is the Omnès matrix, which is consistent with the most recent Roy and Roy-Steiner results on $\pi \pi \to \pi \pi$ and $\pi \pi \to K\overline{K}$, respectively. By the analytic continuation to the complex plane, we found poles associated with the lightest scalar resonances $\sigma /f_0(500)$, $f_0(980)$, and $\kappa /K_0^{*}(700)$ for the physical pion mass value and in the case of $\sigma /f_0(500)$, $\kappa /K_0^{*}(700)$ also for unphysical pion mass values.

We investigate $S=-2$ production from the $\mathrm{\Lambda }p\to K^{+}X$ reactions within the effective Lagrangian approach. The $\mathrm{\Lambda }p\to K^{+}\mathrm{\Lambda }\mathrm{\Lambda }$ and $\mathrm{\Lambda }p\to K^{+}{\mathrm{\Xi }}^{-}p$ reactions are considered to find the lightest $S=-2$ system, which is $H$-dibaryon. We assume that the $H(2250)\to \mathrm{\Lambda }\mathrm{\Lambda }$, and $H(2270)\to {\mathrm{\Xi }}^{-}p$ decays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross sections for $\mathrm{\Lambda }p\to K^{+}\mathrm{\Lambda }\mathrm{\Lambda }$ and $\mathrm{\Lambda }p\to K^{+}{\mathrm{\Xi }}^{-}p$ reactions were found to be of the order of a few $\mu \mathrm{b}$ in the $\mathrm{\Lambda }$ beam momentum range of up to $5\mathrm{GeV}/c$. Furthermore, the direct access of information regarding the interference patterns between the $H$-dibaryon and nonresonant contributions was demonstrated.

The impact of the finite-size effects on the vacuum free energy density of full QCD with $N_f$ massless flavors in the presence of a homogeneous (anti-)self-dual Abelian background gluon field is studied. The zero-temperature free energy density of the four-dimensional spherical domain is computed as a function of the background field strength $B$ and domain radius $R$. The calculation is performed in the one-loop approximation improved by accounting for mixing of the quark and gluon quasizero modes with normal modes, with the use of the $\zeta$-function regularization. It is indicated that, under plausible assumptions on the character of the mixing, the quantum correction to the free energy density has a minimum as a function of $B$ and $R$. Within the mean-field approach to the QCD vacuum based on the domain wall network representation of the mean field, the existence of the minimum may prevent infinite growth of individual domains, thus protecting the vacuum from the long-range ordering, and hence serving as the origin of disorder in the statistical ensemble of domain wall networks, driven by the minimization of the overall free energy of the dominant gauge field configurations.

We investigate the nuclear and quark matters at finite real chemical potential (${\mu }_{\mathrm{R}}$) and low temperature from the viewpoint of the canonical sectors constructed via the imaginary chemical potential region. Based on the large $N_{\mathrm{c}}$ estimation, where $N_{\mathrm{c}}$ is the number of colors, we can discuss the confinement-deconfinement nature at finite ${\mu }_{\mathrm{R}}$ from the canonical sectors. We find the expectation that the sharp changes of canonical sectors at ${\mu }_{\mathrm{R}}\sim M_{\mathrm{B}}/N_{\mathrm{c}}$, where $M_{\mathrm{B}}$ is the lowest baryon mass, happens in the large $N_{\mathrm{c}}$ regime, and it is matched with the quarkyonic picture. In addition, we discuss the color superconductivity and the chiral properties from the structure of canonical sectors. Even in the present anatomy from the canonical sectors, we obtain a suitable picture for the dense QCD matter.

Generalized parton distributions are instrumental to study both the three-dimensional structure and the energy-momentum tensor of the nucleon, and motivate numerous experimental programs involving hard exclusive measurements. Based on a next-to-leading order analysis and a careful study of evolution effects, we exhibit nontrivial generalized parton distributions with arbitrarily small imprints on deeply virtual Compton scattering observables. This means that in practice the reconstruction of generalized parton distributions from measurements, known as the deconvolution problem, does not possess a unique solution for this channel. In this paper we discuss the consequences on the extraction of generalized parton distributions from data and advocate for a multichannel analysis.