In this work, we calculate meson-baryon scattering phase shifts in four channels using lattice QCD methods. From a set of calculations at four volumes, corresponding to spatial sizes of 2, 2.5, 3, and 4 fm, and a pion mass of $m_{\pi }\sim 390\mathrm{MeV}$, we determine the scattering lengths and effective ranges for these systems at the corresponding quark masses. We also perform the calculation at a lighter quark mass, $m_{\pi }\sim 230\mathrm{MeV}$, on the largest volume. Using these determinations, along with those in previous work, we perform a chiral extrapolation of the scattering lengths to the physical point after correcting for the effective range contributions using the multivolume calculations performed at $m_{\pi }\sim 390\mathrm{MeV}$.

QCD and related gauge theories have a sign problem when a $\theta$ term is included; this complicates the extraction of physical information from Euclidean-space calculations as one would do in lattice studies. The sign problem arises in this system because the partition function for configurations with fixed topological charge $Q$, ${\mathcal{Z}}_Q$, are summed weighted by $\exp (iQ\theta )$ to obtain the partition function for fixed $\theta$, $\mathcal{Z}(\theta )$. The sign problem gets exponentially worse numerically as the space-time volume is increased. Here it is shown that, apart from the practical numerical issues associated with large volumes, there are some interesting issues of principle. A key quantity is the energy density as a function of $\theta$, $ϵ(\theta )=-\log (\mathcal{Z}(\theta ))/V$. This is expected to be well defined in the large four-volume limit. Similarly, one expects the energy density for a fixed topological density $\widetilde{ϵ}(Q/V)=-\log ({\mathcal{Z}}_Q)/V$ to be well defined in the limit of large four volumes. Intuitively, one might expect that if one had the infinite volume expression for $\widetilde{ϵ}(Q/V)$ to arbitrary accuracy, then one could reconstruct $ϵ(\theta )$ by directly summing over the topological sectors of the partition function. We show here that there are circumstances where this is not the case. In particular, this occurs in regions where the curvature of $ϵ(\theta )$ is negative.

We discuss single inclusive hadron production from a high-energy quark scattering off a strong target color field in the color glass condensate formalism. Recent calculations of this process at the next-to-leading-order accuracy have led to negative cross sections at large transverse momenta. We identify the origin of this problem as an oversubtraction of the rapidity divergence into the Balitsky-Kovchegov evolution equation for the target. We propose a new way to implement the kinematical restriction on the emitted gluons to overcome this difficulty.

We consider non-Abelian strings in $\mathcal{N}=2$ supersymmetric quantum chromodynamics (QCD) with the $\mathrm{U}(N)$ gauge group and $N_f=N$ quark flavors deformed by a mass term for the adjoint matter. This deformation breaks $\mathcal{N}=2$ supersymmetry down to $\mathcal{N}=1$. Dynamics of orientational zero modes on the string world sheet are described then by $CP(N-1)$ model with $\mathcal{N}=(0,2)$ supersymmetry. We study the string of a finite length $L$ assuming compactification on a cylinder (periodic boundary conditions). The world-sheet theory is solved in the large-$N$ approximation. At $N=\infty$ we find a rich phase structure in the $(L,u)$ plane where $u$ is a deformation parameter. At large $L$ and intermediate $u$ we find a phase with broken $Z_{2N}$ symmetry, $N$ vacua and a mass gap. At large values of $L$ and $u$ still larger we have the $Z_{2N}$-symmetric phase with a single vacuum and massless fermions. In both phases $\mathcal{N}=(0,2)$ supersymmetry is spontaneously broken. We also observe a phase with would-be broken $\mathrm{SU}(N)$ symmetry at small $L$ (it is broken only for $N=\infty$). In the latter phase the mass gap vanishes and the vacuum energy is zero in the leading $1/N$ approximation. We expect that at large but finite $N$ corrections $O(1/N)$ will break $\mathcal{N}=(0,2)$ supersymmetry. Simultaneously, the phase transitions will become rapid crossovers. Finally we discuss how the observed rich phase structure matches the $\mathcal{N}=(2,2)$ limit in which the world-sheet theory has a single phase with the mass gap independent of $L$.

We exploit a connection between the Coulomb/Eikonal phase and the charge distribution in the transverse plane for a transversely polarized nucleon. The known deformation of the charge density in impact parameter space translates into an asymmetry in the Coulomb/Eikonal phase (or the impact parameter electromagnetic potential). The asymmetry in the transverse potential implies an azimuthal asymmetry in the scattering cross section of the scattered electrons in inclusive DIS. We use the transverse potential to calculate the average transverse momentum of the scattered electrons. The sign of the calculated average transverse momentum for a neutron target is consistent with recent Jefferson Lab data.

We present a general formulation to analyze the structure of slowly rotating relativistic stars in a broad class of scalar-tensor theories with disformal coupling to matter. Our approach includes theories with generalized kinetic terms, generic scalar field potentials and contains theories with conformal coupling as particular limits. In order to investigate how the disformal coupling affects the structure of relativistic stars, we propose a minimal model of a massless scalar-tensor theory and investigate in detail how the disformal coupling affects the spontaneous scalarization of slowly rotating neutron stars. We show that for negative values of the disformal coupling parameter between the scalar field and matter, scalarization can be suppressed, while for large positive values of the disformal coupling parameter stellar models cannot be obtained. This allows us to put a mild upper bound on this parameter. We also show that these properties can be qualitatively understood by linearizing the scalar field equation of motion in the background of a general-relativistic incompressible star. To address the intrinsic degeneracy between uncertainties in the equation of state of neutron stars and gravitational theory, we also show the existence of universal equation-of-state-independent relations between the moment of inertia and compactness of neutron stars in this theory. We show that in a certain range of the theory’s parameter space the universal relation largely deviates from that of general relativity, allowing, in principle, to probe the existence of spontaneous scalarization with future observations.

The so-called unimodular version of general relativity is revisited. Unimodular gravity is constructed by fixing the determinant of the metric, which leads to the trace-free part of the equations instead of the usual Einstein field equations. Then a cosmological constant naturally arises as an integration constant. While unimodular gravity turns out to be equivalent to general relativity (GR) at the classical level, it provides important differences at the quantum level. Here we extend the unimodular constraint to some extensions of general relativity that have drawn a lot of attention over the last years—$f(R)$ gravity (or its scalar-tensor picture) and Gauss-Bonnet gravity. The corresponding unimodular version of such theories is constructed as well as the conformal transformation that relates the Einstein and Jordan frames for these nonminimally coupled theories. From the classical point of view, the unimodular versions of such extensions are completely equivalent to their originals, but an effective cosmological constant arises naturally, which may provide a richer description of the evolution of the Universe. Here we analyze the case of Starobisnky inflation and compare it with the original one.

We revisit the physics of transitions from a general equation of state parameter to the final stage of slow-roll inflation. We show that it is unlikely for the modes comprising the cosmic microwave background to contain imprints from a preinflationary equation of state transition and still be consistent with observations. We accomplish this by considering observational consistency bounds on the amplitude of excitations resulting from such a transition. As a result, the physics which initially led to inflation likely cannot be probed with observations of the cosmic microwave background. Furthermore, we show that it is unlikely that equation of state transitions may explain the observed low multipole power suppression anomaly.

The iron $\mathrm{K}\alpha$ line commonly observed in the x-ray spectrum of black hole candidates is produced by x-ray fluorescence of the inner accretion disk. This line can potentially be quite a powerful tool to probe the spacetime geometry around these objects and test the Kerr black hole hypothesis. In a previous paper, we studied the ability to constrain possible deviations from the Kerr solution from the standard time-integrated iron line spectrum within the Cardoso-Pani-Rico framework. In the present work, we expand on that study and consider iron line reverberation mapping in the Cardoso-Pani-Rico framework. That is, we consider the time evolution of the iron line profile in response to fluctuations in the x-ray primary source. Our simulations clearly show that the time information in reverberation mapping can better constrain the background metric than the time-integrated approach, and this is true, notably, for the deformation parameter ${\epsilon }_3^r$, which is only weakly informed by a time-integrated observation.

The Fermi-LAT data accumulated over 7 years of $\gamma$-ray observations, together with the high resolution gas (CO & HI) and the dust opacity maps, are used to study the emissivity of $\gamma$-rays induced by interactions of cosmic rays (CRs) with the interstellar medium. Based on the dust opacity templates, the $\gamma$-ray emissivity was measured for 36 segments of the Galactic plane. Furthermore, the $\gamma$-ray emissivity was evaluated in six Galactocentric rings. Both the absolute emissivity and the energy spectra of $\gamma$-rays derived in the interval 0.2–100 GeV show significant variations along the galactic plane. The density of CRs, derived under the assumption that $\gamma$-rays are predominately produced in CR interactions with the interstellar gas, is characterized by a strong radial dependence. In the inner Galaxy the CR density substantially exceeds the density in the outer parts of the Galaxy: by a factor of a few at 10 GeV, and by more than an order of magnitude at 1 TeV. Remarkably, the energy distribution of CRs appears to be substantially harder than the energy spectrum obtained from direct measurements of local CRs. At the same time, the flux and the energy spectrum of multi-GeV protons derived from $\gamma$-ray data in the outskirts of the Galaxy is quite close to the measurements of local CRs.

We present a Gaussian regression method for time series with missing data and stationary residuals of unknown power spectral density (PSD). The missing data are efficiently estimated by their conditional expectation as in universal Kriging based on the circulant approximation of the complete data covariance. After initialization with an autoregressive fit of the noise, a few iterations of estimation/reconstruction steps are performed until convergence of the regression and PSD estimates, in a way similar to the expectation-conditional-maximization algorithm. The estimation can be performed for an arbitrary PSD provided that it is sufficiently smooth. The algorithm is developed in the framework of the MICROSCOPE space mission whose goal is to test the weak equivalence principle (WEP) with a precision of ${10}^{-15}$. We show by numerical simulations that the developed method allows us to meet three major requirements: to maintain the targeted precision of the WEP test in spite of the loss of data, to calculate a reliable estimate of this precision and of the noise level, and finally to provide consistent and faithful reconstructed data to the scientific community.

In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth’s gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency $\omega$. The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as $t^2$. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of $1.06\times {10}^{-5}$, and hence with a million ultracold neutrons, one should be able to observe transitions.

The problem of nonlinear transport in a two-dimensional superconductor with an applied oscillating electric field is solved by the holographic method. The complex conductivity can be computed from the dynamics of the current for both the near- and nonequilibrium regimes. The limit of weak electric field corresponds to the near-equilibrium superconducting regime, where the charge response is linear and the conductivity develops a gap determined by the condensate. A larger electric field drives the system into a superconducting nonequilibrium steady state, where the nonlinear conductivity is quadratic with respect to the electric field. Increasing the amplitude of the applied electric field results in a far-from-equilibrium nonsuperconducting steady state with a universal linear conductivity of one. In the lower temperature regime we also find chaotic behavior of the superconducting gap, which results in a nonmonotonic field-dependent nonlinear conductivity.

The experimental and theoretical implications of heavy digauge boson resonances that couple to, or are comprised of, new charged and strongly interacting matter are investigated. Observation and measurement of ratios of the resonant digauge boson channels $WW$, $ZZ$, $\gamma \gamma$, $Z\gamma$, and $gg$ in the form of dijets provide a rather direct—and for some ratios a rather robust—probe of the gauge representations of the new matter. For a spin-zero resonance with the quantum numbers of the vacuum, the ratios of resonant $WW$ and $ZZ$ to $\gamma \gamma$ channels, as well as the longitudinal vs transverse polarization fractions in the $WW$ and $ZZ$ channels, provide probes for possible mixing with the Higgs boson, while di-Higgs and ditop resonant channels, $hh$ and $tt$, provide somewhat less sensitivity. We present a survey of possible underlying models for digauge boson resonances by considering various limits for the mass of the new charged and strongly interacting matter fields as well as the confinement scale of new hypergauge interactions under which they may also be charged. In these limits, resonances may be included as elementary weakly coupled spin-zero states or can correspond to hyperglueballs, hyperonia, or pseudoscalar hypermesons. For each of these cases, we make predictions for additional states that could be resonantly or pair produced and observed at the Large Hadron Collider or in future collider experiments. Heavy digauge boson resonances can provide a unified explanation for a number of small discrepancies and excesses in reported data from the Large Hadron Collider.

We explain the recent excess seen by ATLAS and CMS experiments at around 750 GeV in the diphoton invariant mass as a narrow-width sneutrino decaying to diphotons via a stau loop in $R$-parity violating supersymmetry. The stau mass is predicted to be somewhere between half the resonant sneutrino mass and half the sneutrino mass plus 14 GeV. The scenario also predicts further signal channels at an invariant mass of 750 GeV, the most promising being into dijets and $WW$. We also predict a left-handed charged slepton decaying into $WZ$ and $W\gamma$ at a mass 750–754 GeV.

In this paper, we consider a minimal extension to the standard model by a scalar triplet field with hypercharge $Y=2$. This model relies on the seesaw mechanism which provides a consistent explication of neutrino mass generation. We show from naturalness considerations that the Veltman condition is modified by virtue of the additional scalar charged states and that quadratic divergencies at one loop can be driven to zero within the allowed parameter space of the model; the latter is severely constrained by unitarity and boundedness from below, and it is consistent with the di-photon Higgs decay data of the LHC. Furthermore, we analyze the naturalness condition effects to the masses of heavy Higgs bosons $H^0$, $A^0$, $H^{\pm }$ and $H^{\pm \pm }$, providing a drastic reduction of the ranges of variation of $m_{H^{\pm }}$ and $m_{H^{\pm \pm }}$ with an upper bounds at 288 and 351 GeV, respectively, while predicting almost a degeneracy for the other neutral Higgs bosons $H^0$, $A^0$ at about 207 GeV.

The correlations between the modulus of the Polyakov loop, its phase $\theta$, and the Landau gauge gluon propagator at finite temperature are investigated in connection with the center symmetry for pure Yang-Mills SU(3) theory. In the deconfined phase, where the center symmetry is spontaneously broken, the phase of the Polyakov loop per configuration is close to $\theta =0$, $\pm 2\pi /3$. We find that the gluon propagator form factors associated with $\theta \approx 0$ differ quantitatively and qualitatively from those associated to $\theta \approx \pm 2\pi /3$. This difference between the form factors is a property of the deconfined phase and a sign of the spontaneous breaking of the center symmetry. Furthermore, given that this difference vanishes in the confined phase, it can be used as an order parameter associated to the deconfinement transition. For simulations near the critical temperature $T_c$, the difference between the propagators associated to $\theta \approx 0$ and $\theta \approx \pm 2\pi /3$ allows one to classify the configurations as belonging to the confined or deconfined phase. This establishes a selection procedure which has a measurable impact on the gluon form factors. Our results also show that the absence of the selection procedure can be erroneously interpreted as lattice artifacts.

We describe the implementation of quantum electrodynamic (QED) evolution at leading order (LO) along with quantum chromodynamic (QCD) evolution at next-to-leading order (NLO) in the CTEQ-TEA global analysis package. The inelastic contribution to the photon parton distribution function (PDF) is described by a two-parameter ansatz, coming from radiation off the valence quarks, and based on the CT14 NLO PDFs. Setting the two parameters to be equal allows us to completely specify the inelastic photon PDF in terms of the inelastic momentum fraction carried by the photon, $p_0^{\gamma }$, at the initial scale $Q_0=1.295\mathrm{GeV}$. We obtain constraints on the photon PDF by comparing with ZEUS data [S. Chekanov et al. (ZEUS Collaboration), Phys. Lett. B 687, 16 (2010)] on the production of isolated photons in deep inelastic scattering, $ep\to e\gamma +X$. For this comparison we present a new perturbative calculation of the process that consistently combines the photon-initiated contribution with the quark-initiated contribution. Comparison with the data allows us to put a constraint at the 90% confidence level of $p_0^{\gamma }\lesssim 0.14\%$ for the inelastic photon PDF at the initial scale of $Q_0=1.295\mathrm{GeV}$ in the one-parameter radiative ansatz. The resulting inelastic CT14QED PDFs will be made available to the public. In addition, we also provide CT14QEDinc PDFs, in which the inclusive photon PDF at the scale $Q_0$ is defined by the sum of the inelastic photon PDF and the elastic photon distribution obtained from the equivalent photon approximation.

In the nucleon electroexcitation reactions, ${\gamma }^{*}N\to R$, where $R$ is a nucleon resonance ($N^{*}$), the electric amplitude $E$ and the longitudinal amplitude $S_{1/2}$ are related by $E\propto \frac{\omega }{|\mathbf{q}|}{S}_{1/2}$, in the pseudothreshold limit ($|\mathbf{q}|\to 0$), where $\omega$ and $|\mathbf{q}|$ are, respectively, the energy and the magnitude of 3-momentum of the photon. The previous relation is usually referred to as Siegert’s theorem. The form of the electric amplitude, defined in terms of the transverse amplitudes $A_{1/2}$ and $A_{3/2}$, and the explicit coefficients of the relation depend on the angular momentum and parity ($J^P$) of the resonance $R$. The Siegert’s theorem is the consequence of the structure of the electromagnetic transition current, which induces constraints between the electromagnetic form factors in the pseudothreshold limit. In the present work, we study the implications of the Siegert’s theorem for the ${\gamma }^{*}N\to \mathrm{\Delta }(1232)$ and ${\gamma }^{*}N\to N(1520)$ transitions. For the ${\gamma }^{*}N\to N(1520)$ transition, in addition to the relation between the electric amplitude and longitudinal amplitude, we also obtain a relation between the two transverse amplitudes: $A_{1/2}=A_{3/2}/\sqrt{3}$, at the pseudothreshold. The constraints at the pseudothreshold are tested for the MAID2007 parametrizations of the reactions under discussion. New parametrizations for the amplitudes $A_{1/2}$, $A_{3/2}$, and $S_{1/2}$ for the ${\gamma }^{*}N\to \mathrm{\Delta }(1232)$ and ${\gamma }^{*}N\to N(1520)$ transitions, valid for small and large $Q^2$, are proposed. The new parametrizations are consistent with both: the pseudothreshold constraints (Siegert’s theorem) and the empirical data.

Inspired by the 750 GeV diphoton state recently reported by ATLAS and CMS, we propose a $U(1{)}_{B–L}$ extension of the MSSM which predicts the existence of four spin zero resonance states that are degenerate in mass in the supersymmetric limit. Vectorlike fields, a gauge singlet field, as well as the MSSM Higgsinos are prevented from acquiring arbitrary large masses by a $U(1)$ R symmetry. Indeed, these masses can be considerably lighter than the $Z^{\prime }$ gauge boson mass. Depending on kinematics, the resonance states could decay into right-handed neutrinos and sneutrinos, and/or MSSM Higgs fields and Higgsinos with total decay widths in the multi-GeV range.