The Particle Data Group Meson Summary Table lists the $X(3915)$ meson, an $\omega J/\psi$ mass peak seen in $B\to K\omega J/\psi$ decays and $\gamma \gamma \to \omega J/\psi$ two-photon fusion reactions, as the ${\chi }_{c0}(2P)$, the $2^3{P}_0$ charmonium state. Here, with some reasonable assumptions, it is shown that if the $X(3915)$ is the ${\chi }_{c0}(2P)$, the measured strength of the $\gamma \gamma \to X(3915)$ signal implies an upper limit on the branching fraction $\mathcal{B}({\chi }_{c0}(2P)\to \omega J/\psi )$ that is below a lower limit inferred for the same quantity from the $B\to KX(3915)$ decay rate. Also, the absence any signal for $X(3915)\to D^0{\overline{D}}^0$ in $B^{+}\to K^{+}{D}^0{\overline{D}}^0$ decays is used to infer the limit $\mathcal{B}(X(3915)\to D^0{\overline{D}}^0)<1.2\times \mathcal{B}(X(3915)\to \omega J/\psi )$. This contradicts expectations that ${\chi }_{c0}(2P)$ decays to $D^0{\overline{D}}^0$ should be a dominant process, while decays to $\omega J/\psi$, which are Okubo-Zweig-Iizuka suppressed, should be relatively rare. These, plus reasons given earlier by Guo and Meissner, raise concerns about the $X(3915)={\chi }_{c0}(2P)$ assignment.

Among laboratory probes of dark matter, fixed-target neutrino experiments are particularly well suited to search for light weakly coupled dark sectors. In this paper, we show that the DAEδALUS source setup—an 800 MeV proton beam impinging on a target of graphite and copper—can improve the present LSND bound on dark photon models by an order of magnitude over much of the accessible parameter space for light dark matter when paired with a suitable neutrino detector such as LENA. Interestingly, both DAEδALUS and LSND are sensitive to dark matter produced from off-shell dark photons. We show for the first time that LSND can be competitive with searches for visible dark photon decays and that fixed-target experiments have sensitivity to a much larger range of heavy dark photon masses than previously thought. We review the mechanism for dark matter production and detection through a dark photon mediator, discuss the beam-off and beam-on backgrounds, and present the sensitivity in dark photon kinetic mixing for both the DAEδALUS/LENA setup and LSND in both the on- and off-shell regimes.

We compute the axial, scalar, tensor and pseudoscalar isovector couplings of the nucleon as well as the induced tensor and pseudoscalar charges in lattice simulations with $N_{\mathrm{f}}=2$ mass-degenerate nonperturbatively improved Wilson-Sheikholeslami-Wohlert fermions. The simulations are carried out down to a pion mass of 150 MeV and linear spatial lattice extents of up to 4.6 fm at three different lattice spacings ranging from approximately 0.08 fm to 0.06 fm. Possible excited state contamination is carefully investigated and finite volume effects are studied. The couplings, determined at these lattice spacings, are extrapolated to the physical pion mass. In this limit we find agreement with experimental results, where these exist, with the exception of the magnetic moment. A proper continuum limit could not be performed, due to our limited range of lattice constants, but no significant lattice spacing dependence is detected. Upper limits on discretization effects are estimated and these dominate the error budget.

The Horndeski theory of gravity is known as the most general scalar-tensor theory with second-order field equations. Recently, it was demonstrated by Gleyzes et al. that the Horndeski theory can further be generalized in such a way that although field equations are of third order, the number of propagating degrees of freedom remains the same. We study small-scale gravity in the generalized Horndeski theory, focusing in particular on an impact of the new derivative interaction beyond Horndeski on the Vainshtein screening mechanism. In the absence of the quintic Galileon term and its generalization, we show that the new interaction does not change the qualitative behavior of gravity outside and near the source: the two metric potentials coincide, $\mathrm{\Phi }=\mathrm{\Psi }(\sim r^{-1})$, while the gravitational coupling is given by the cosmological one and hence is time dependent in general. We find, however, that the gravitational field inside the source shows a novel behavior due to the interaction beyond Horndeski: the gravitational attraction is not determined solely from the enclosed mass and two potentials do not coincide, indicating breaking of the screening mechanism.

Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the $154{\mathrm{deg}}^2$ CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models covering broad ranges of the three parameters ${\mathrm{\Omega }}_m$, ${\sigma }_8$, and $w$, and replicating the Galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of $\le 5\%$, and compute the likelihood in the three-dimensional parameter space (${\mathrm{\Omega }}_m$, ${\sigma }_8$, $w$) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain $w$ without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (${\mathrm{\Omega }}_m$, ${\sigma }_8$) plane reduces by a factor of $\approx 2$, compared to using the power spectrum alone. For a flat $\mathrm{\Lambda }$ cold dark matter model, combining both statistics, we obtain the constraint ${\sigma }_8({\mathrm{\Omega }}_m/0.27{)}^{0.63}={0.85}_{-0.03}^{+0.03}$.

We study gravitational lensing by a recently proposed black hole solution in loop quantum gravity. We highlight the fact that the quantum gravity corrections to the Schwarzschild metric in this model evade the “mass suppression” effects (that the usual quantum gravity corrections are susceptible to) by virtue of one of the parameters in the model being dimensionless, which is unlike any other quantum gravity motivated parameter. Gravitational lensing in the strong and weak deflection regimes is studied, and a sample consistency relation is presented which could serve as a test of this model. We discuss that, though the consistency relation for this model is qualitatively similar to what would have been in Brans–Dicke, in general it can be a good discriminator between many alternative theories. Although the observational prospects do not seem to be very optimistic even for a galactic supermassive black hole case, time delay between relativistic images for a billion solar mass black holes in other galaxies might be within reach of future relativistic lensing observations.

The Pontecorvo–Maki–Nakagawa–Sakata and Cabibbo–Kobayashi–Maskawa matrices are phenomenologically close to symmetric, and a symmetric form could be used as zeroth-order approximation for both matrices. We study the possible theoretical origin of this feature in flavor symmetry models. We identify necessary geometric properties of discrete flavor symmetry groups that can lead to symmetric mixing matrices. Those properties are actually very common in discrete groups such as $A_4$, $S_4$, or $\mathrm{\Delta }(96)$. As an application of our theorem, we generate a symmetric lepton mixing scheme with ${\theta }_{12}={\theta }_{23}=36.21°$; ${\theta }_{13}=12.20°$, and $\delta =0$, realized with the group $\mathrm{\Delta }(96)$.

Within the framework of Dyson-Schwinger equations , we discuss the chiral phase transition of QCD with a chiral chemical potential ${\mu }_5$ as an additional scale. We focus especially on the issues related to the widely accepted as well as interesting critical end point (CEP). With the help of a scalar susceptibility, we find that there might be no ${\mathrm{CEP}}_5$ in the $T-{\mu }_5$ plane, and the phase transition in the $T-{\mu }_5$ plane might be totally crossover when $\mu <50\mathrm{MeV}$, which has apparent consistency with the lattice QCD calculation. Our study may also provide some useful hints to some other studies related to ${\mu }_5$.

We explore the explanation of the Fermi Galactic Center excess (GCE) in the next-to-minimal supersymmetric Standard Model. We systematically consider various experimental constraints including the dark matter (DM) relic density, DM direct detection results, and indirect searches from dwarf galaxies. We find that, for DM with mass ranging from 30 to 40 GeV, the GCE can be explained by the annihilation $\chi \chi \to a^{*}\to b\overline{b}$ only when the $CP$-odd scalar satisfies $m_a\simeq 2m_{\chi }$, and in order to obtain the measured DM relic density, a sizable $Z$-mediated contribution to DM annihilation must intervene in the early universe. As a result, the Higgsino mass $\mu$ is upper bounded by about 350 GeV. Detailed Monte Carlo simulations on the $3\ell +E_T^{\text{miss}}$ signal from neutralino/chargino associated production at 14-TeV LHC indicate that the explanation can be mostly (completely) excluded at 95% C.L. with an integrated luminosity of $100(200){\mathrm{fb}}^{-1}$. We also discuss the implication of possible large $Z$ coupling to DM for the DM-nucleon spin dependent (SD) scattering cross section, and find that although the current experimental bounds on ${\sigma }_p^{\mathrm{SD}}$ is less stringent than the spin independent results, the future XENON-1T and LZ data may be capable of testing most parts of the GCE-favored parameter region.

We propose a new electroweak baryogenesis scenario in high-scale supersymmetric (SUSY) models. We consider a singlet extension of the minimal SUSY standard model introducing additional vectorlike multiplets. We show that the strongly first-order phase transition can occur at a high temperature comparable to the soft SUSY breaking scale. In addition, the proper amount of the baryon asymmetry of the Universe can be generated via the lepton number violating process in the vectorlike multiplet sector. The typical scale of our scenario, the soft SUSY breaking scale, can be any value. Thus our new electroweak baryogenesis scenario can be realized at arbitrary scales, and we call this scenario scale free electroweak baryogenesis. This soft SUSY breaking scale is determined by other requirements. If the soft SUSY breaking scale is $\mathcal{O}(10)\mathrm{TeV}$, our scenario is compatible with the observed mass of the Higgs boson and the constraints by electric dipole moment measurements and flavor experiments. Furthermore, the singlino can be a good candidate for dark matter.

In this paper we consider the coherence properties of neutrinos produced by the decays of pions in conventional neutrino beams. Using a multiparticle density matrix formalism we derive the oscillation probability for neutrinos emitted by a decaying pion in an arbitrary quantum state. Then, using methods from decoherence theory, we calculate the pion state which evolves through interaction with decay-pipe gases in a typical accelerator neutrino experiment. These two ingredients are used to obtain the distance scales for neutrino beam coherence loss. We find that for the known neutrino mass splittings, no nonstandard oscillation effects are expected on terrestrial baselines. Heavy sterile neutrinos may experience terrestrial loss of coherence, and we calculate both the distance over which this occurs and the energy resolution required to observe the effect. By treating the pion-muon-neutrino-environment system quantum mechanically, neutrino beam coherence properties are obtained without assuming arbitrary spatial or temporal scales at the neutrino production vertex.

We use $772\times 10^6$ $B\overline{B}$ meson pairs collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector to measure the branching fraction for $\overline{B}\to X_s\gamma$. Our measurement uses a sum-of-exclusives approach in which 38 of the hadronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<2.8\mathrm{GeV}/c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be $\mathcal{B}(\overline{B}\to X_s\gamma )=(3.51\pm 0.17\pm 0.33)\times 10^{-4}$, where the first uncertainty is statistical and the second is systematic.

We study flux tubes (strings) on the Higgs branches in supersymmetric gauge theories. In generic vacua on the Higgs branches, strings were shown to develop long-range “tails” associated with massless fields, a characteristic feature of the Higgs branch (the only exception is the vacuum at the base of the Higgs branch). A natural infrared regularization for the above tails is provided by a finite string length $L$. We perform a numerical study of these strings in generic vacua. We focus on the simplest example of strings in $\mathcal{N}=1$ supersymmetric QED with the Fayet-Iliopoulos term. In particular, we examine the accuracy of a logarithmic approximation (proposed earlier by Evlampiev and Yung) for the tension of such string solutions. In the Evlampiev-Yung formula, the dependence of tension on the string length is logarithmic, and the dependence on the geodesic length from the base of the Higgs branch is quadratic. We observe a remarkable agreement of our numerical results for the string tension with the Evlampiev-Yung analytic expression.

The spin-charge-family theory [1–13], in which spinors, besides the Dirac spin, also carry the second kind of Clifford object—no charges—is a type of Kaluza-Klein theory [14]. The Dirac spinors of one Weyl representation in $d=(13+1)$ manifest [1,3,4,10,13,15] in $d=(3+1)$ at low energies all of the properties of quarks and leptons assumed by the standard model. The second kind of spin explains the origin of families. Spinors interact with the vielbeins and the two kinds of spin connection fields, the gauge fields of the two kinds of Clifford objects, which, besides the gravity and known gauge vector fields, manifest in $d=(3+1)$ also several scalar gauge fields. Scalars with the space index $s\in (7,8)$ carry the weak charge and the hypercharge ($\mp \frac{1}{2},\pm \frac{1}{2}$, respectively), thereby explaining the origin of the Higgs and Yukawa couplings. It is demonstrated in this paper that the scalar fields with the space index $t\in (9,10,\dots ,14)$ carry the triplet color charges, causing transitions of antileptons and antiquarks into quarks and back, thus enabling the appearance and the decay of baryons. These scalar fields show themselves in the presence of the right-handed neutrino condensate, which breaks the $CP$ symmetry, the answer to the question about matter-antimatter asymmetry.

Wave functions and energy eigenvalues of the path integral Hamiltonian are studied in the Lorentz frame moving with velocity $v$. The instantaneous interaction produced by the Wilson loop is shown to be reduced by an overall factor $\sqrt{1-(\frac{v}{c}{)}^2}$. As a result, one obtains the boosted energy eigenvalues in the Lorentz covariant form $E=\sqrt{{\mathbf{P}}^2+M_0^2}$, where $M_0$ is the c.m. energy, and this form is tested for two free particles and for the Coulomb and linear interaction. Using Lorentz-contracted wave functions of the bound states, one obtains the scaled-parton wave functions and valence quark distributions for large $P$. Matrix elements containing wave functions moving with different velocities strongly decrease with growing relative momentum; e.g., for the timelike form factors, one obtains $F_h(Q_0)\sim {(\frac{M_h}{Q_0})}^{2n_h}$ with $n_h=1$ and 2 for mesons and baryons, as in the “quark counting rule.”

Theories of modified gravity attempt to reconcile physics at the largest and the smallest scales by explaining the accelerated expansion of our Universe without introducing the cosmological constant. One class of such theories, known as Galileon theories, predicts lensing potentials of spherically symmetric bodies, such as dark matter halos, to receive a featurelike modification at the 5% level. With the advent of next-generation photometric surveys, such modifications can serve as novel probes of modified gravity. Assuming an Large Synoptic Survey Telescope-like fiducial data set, we produce halo-shear power spectra for cold dark matter and Galileon scenarios and perform a Fisher analysis including cosmological, nuisance, and Galileon parameters to study the detectability of the aforementioned modifications. With the cold dark matter scenario as our null hypothesis, we conclude, with a number of idealized assumptions and approximations, that the detection of Galileon modifications could in principle reach up to $4\text{−}\sigma$ if present, or strongly excluded in a nondetection, with a tomography of four redshift bins and four mass bins, an Large Synoptic Survey Telescope-like set of survey parameters, and Planck priors on cosmological parameters.

We propose a way of including the next-to-leading (NLO) order spin-spin coupling in an effective-one-body (EOB) Hamiltonian. This work extends by S. Balmelli and P. Jetzer, [Phys. Rev. D 87, 124036 (2013)], which is restricted to the case of equatorial orbits and aligned spins, to general orbits with arbitrary spin orientations. This is done by applying appropriate canonical phase-space transformations to the NLO spin-spin Hamiltonian in Arnowitt-Deser-Misner (ADM) coordinates, and systematically adding effective quantities at NLO to all spin-squared terms appearing in the EOB Hamiltonian. As required by consistency, the introduced quantities reduce to zero in the test-mass limit. We expose the result both in a general gauge and in a gauge-fixed form. The last is chosen such as to minimize the number of new coefficients that have to be inserted into the effective spin squared. As a result, the 25 parameters that describe the ADM NLO spin-spin dynamics get condensed into only 12 EOB terms.

In general relativity, local cosmic strings are well known to produce a static, locally flat spacetime with a wedge removed. If the tension exceeds a critical value, the deficit angle becomes larger than $2\pi$, leading to a compact exterior that ends in a conical singularity. In this paper, we investigate dynamical solutions for cosmic strings with super-critical tensions. To this end, we model the string as a cylindrical shell of finite and stabilized transverse width and show that there is a marginally super-critical regime in which the stabilization can be achieved by physically reasonable matter. We show numerically that the static deficit angle solution is unstable for super-critical string tensions. Instead, the geometry starts expanding in the axial direction at an asymptotically constant rate, and a horizon is formed in the exterior spacetime, which has the shape of a growing cigar. We are able to find the analytic form of the attractor solution describing the interior of the cosmic string. In particular, this enables us to analytically derive the relation between the string tension and the axial expansion rate. Furthermore, we show that the exterior conical singularity can be avoided for dynamical solutions. Our results might be relevant for theories with two extra dimensions, modeling our Universe as a cosmic string with a three-dimensional axis. We derive the corresponding Friedmann equation, relating the on-brane Hubble parameter to the string tension or, equivalently, brane cosmological constant.

Einstein gravities in general dimensions coupled to a cosmological constant and extended with quadratic curvature invariants admit a variety of black holes that may asymptote to Minkowski, anti–de Sitter or Lifshitz spacetimes. We adopt the Wald formalism to derive an explicit formula for calculating the thermodynamical first law for the static black holes with spherical, toric, or hyperbolic isometries in these theories. This allows us to derive or rederive the first laws for a wide range of black holes in the literature. Furthermore, we construct many new exact solutions and obtain their first laws.

We use the feature that the gravitational Compton scattering amplitude factorizes in terms of Abelian QED amplitudes to evaluate various gravitational Compton processes. We examine both the QED and gravitational Compton scattering from a massive spin-1 system by the use of helicity amplitude methods. In the case of gravitational Compton scattering we show how the massless limit can be used to evaluate the cross section for graviton-photon scattering and discuss the difference between photon interactions and the zero mass spin-1 limit. We show that the forward scattering cross section for graviton photoproduction has a very peculiar behavior, differing from the standard Thomson and Rutherford cross sections for a Coulomb-like potential.