We study an extended Standard Model with a gauged ${\mathrm{U}(1)}^{\prime }$ flavor symmetry, motivated not only by the fermion mass hierarchy but also by the excesses in $B\to K^{(*)}ll$ reported by the LHCb collaborations. The ${\mathrm{U}(1)}^{\prime }$ charges are assigned to quarks and leptons in a flavor-dependent manner, and flavored Higgs doublets are also introduced in order to detail the Yukawa couplings at the renormalizable level. Then, the fermion mass hierarchy is realized by the vacuum alignment of the Higgs doublets. In this model, flavor-changing currents involving the gauge boson of ${\mathrm{U}(1)}^{\prime }$ and the scalars generated by the Higgs doublets are predicted and the observables in the $B\to K^{(*)}ll$ process possibly deviate from the Standard Model predictions. We study the possibility that these new flavor-changing interactions can explain the excesses in the $B\to K^{(*)}ll$ process, and we derive some predictions for the other flavor-violating processes based on the analysis. We specifically investigate the $\mathrm{\Delta }F=2$ processes and the other $B$ decays: e.g., $B\to X_s\gamma$ and $B\to D^{(*)}\tau \nu$, where the deviations are reported by the Belle and BABAR collaborations.

Neutrino masses and the number of light neutrino species can be tested in a variety of laboratory experiments and also can be constrained by particle astrophysics and precision cosmology. A conflict between these various results could be an indication of new physics in the neutrino sector. In this paper, we explore the possibility for reconciliation of otherwise discrepant results in a simple model containing a light scalar field which produces mass-varying neutrinos. We extend previous work on mass-varying neutrinos to consider issues of neutrino clumping, the effects of additional contributions to neutrino mass, and reconciliation of eV mass sterile neutrinos with cosmology.

The confirmation of excess in $R_{D^{*}}$ at the LHCb is an indication of lepton flavor nonuniversality. Various different new physics operators and their coupling strengths, which provide a good fit to $R_D$, $R_{D^{*}}$, and $q^2$ spectra, were identified previously. In this work, we try to find angular observables in $\overline{B}\to D^{*}\tau \overline{\nu }$ which enable us to distinguish between these new physics operators. We find that the $D^{*}$ polarization fraction $f_L(q^2)$ is a good discriminant of scalar and tensor new physics operators. The change in $⟨f_L(q^2)⟩$, induced by scalar and tensor operators, is about 3 times larger than the expected uncertainty in the upcoming Belle measurement.

We present a general analysis of the orbital angular momentum (OAM) distribution of gluons $L_g(x)$ inside the nucleon with particular emphasis on the small-$x$ region. We derive a novel operator representation of $L_g(x)$ in terms of Wilson lines and argue that it is approximately proportional to the gluon helicity distribution $L_g(x)\approx -2\mathrm{\Delta }G(x)$ at small $x$. We also compute longitudinal single-spin asymmetry in exclusive diffractive dijet production in lepton-nucleon scattering in the next-to-eikonal approximation and show that the asymmetry is a direct probe of the gluon helicity/OAM distribution as well as the QCD odderon exchange.

We propose a new model to create a light meson in the heavy quarkonium transition, which is inspired by the Nambu–Jona-Lasinio (NJL) model. Hadronic transitions of $J^{PC}=1^{--}$ higher charmonia with the emission of an $\eta$ meson are studied in the framework of the proposed model. The model shows its potential to reproduce the observed decay widths and make predictions for the unobserved channels. We present our predictions for the decay width of $\mathrm{\Psi }\to J/\psi \eta$ and $\mathrm{\Psi }\to h_c(1P)\eta$, where $\mathrm{\Psi }$ are higher $S$ and $D$ wave vector charmonia, which provide useful references to search for higher charmonia and determine their properties in forthcoming experiments. The predicted branching fraction $\mathcal{B}(\psi (4415)\to h_c(1P)\eta )=4.62\times {10}^{-4}$ is one order of magnitude smaller than the $J/\psi \eta$ channel. Estimates of partial decay width $\mathrm{\Gamma }(Y\to J/\psi \eta )$ are given for $Y(4360)$, $Y(4390)$, and $Y(4660)$ by assuming them as $c\overline{c}$ bound states with quantum numbers $3^3{D}_1$, $3^3{D}_1$, and $5^3{S}_1$, respectively. Our results are in favor of these assignments for $Y(4360)$ and $Y(4660)$. The corresponding experimental data for these $Y$ states has large statistical errors which do not provide any constraint on the mixing angle if we introduce $S-D$ mixing. To identify $Y(4390)$, precise measurements on its hadronic branching fraction are required which are eagerly awaited from BESIII.

Same-sign $W$ boson pair production is a promising channel to look for signatures of double parton interactions at the LHC. The corresponding cross section has been calculated by using double parton distribution functions, encoding two parton correlations, evaluated in a light-front quark model. The obtained result is in line with previous estimates which make use of an external parameter, the so-called effective cross section, not necessary in our approach. The possibility to observe for the first time two-parton correlations, in the next LHC runs, has been established.

We update the leading order in ${\alpha }_s$ QCD amplitude for deep exclusive neutrino and antineutrino production of a light meson on an unpolarized nucleon. The factorization theorems of the collinear QCD approach allow us to write the amplitude as the convolution of generalized parton distributions and perturbatively calculable coefficient functions. We study both the pseudoscalar-meson and longitudinally polarized vector-meson cases. It turns out that, contrarily to the electroproduction case, the leading-twist scattering amplitudes for $\pi$ and ${\rho }_L$ productions are proportional to one another, which may serve as an interesting new test of the leading-twist dominance of exclusive processes at medium scale. The importance of the gluonic contribution to most cross sections is stressed.

Neutrino-induced single-pion production (SPP) provides an important contribution to neutrino-nucleus interactions, ranging from intermediate to high energies. There exists a good number of low-energy models in the literature to describe the neutrino production of pions in the region around the Delta resonance. Those models consider only lowest-order interaction terms and, therefore, fail in the high-energy region (pion-nucleon invariant masses, $W\gtrsim 2\mathrm{GeV}$). Our goal is to develop a model for electroweak SPP off the nucleon, which is applicable to the entire energy range of interest for present and future accelerator-based neutrino-oscillation experiments. We start with the low-energy model of [E. Hernández, J. Nieves, and M. Valverde, Phys. Rev. D 76, 033005 (2007).], which includes resonant contributions and background terms derived from the pion-nucleon Lagrangian of chiral-perturbation theory [S. Scherer and M. R. Schindler, A Primer for Chiral Perturbation Theory (Springer, Berlin, 2012), p. 1.]. Then, from the background contributions, we build a high-energy model using a Regge approach. The low- and high-energy models are combined, in a phenomenological way, into a hybrid model. The hybrid model is identical to the low-energy model in the low-$W$ region, but, for $W>2\mathrm{GeV}$, it implements the desired high-energy behavior dictated by Regge theory. We have tested the high-energy model by comparing with one-pion production data from electron and neutrino reactions. The hybrid model is compared with electron-proton scattering data, with neutrino SPP data and with the predictions of the NuWro Monte Carlo event generator. Our model is able to provide satisfactory predictions of the electroweak one-pion production cross section from pion threshold to high $W$. Further investigation and more data are needed to better understand the mechanisms playing a role in the electroweak SPP process in the high-$W$ region, in particular, those involving the axial current contributions.

We calculate the gauge invariant Drell-Yan-like hadron tensors. In connection with new COMPASS results, we predict the new single spin asymmetry which probes gluon poles together with chiral-odd and time-odd functions. The relevant pion production as a particular case of the Drell-Yan-like process has been discussed. For the meson-induced Drell-Yan (DY) process, we model an analog of the twist-3 distribution function, which is a collinear function in inclusive channel, by means of two noncollinear distribution amplitudes which are associated with exclusive channel. This modeling demonstrates the fundamental duality between different factorization regimes.

We study the singly Cabibbo suppressed decays ${\mathrm{\Lambda }}_c^{+}\to p\eta$ and ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ using ${\mathrm{\Lambda }}_c^{+}{\overline{\mathrm{\Lambda }}}_c^{-}$ pairs produced by $e^{+}{e}^{-}$ collisions at a center-of-mass energy of $\sqrt{s}=4.6\mathrm{GeV}$. The data sample was collected by the BESIII detector at the BEPCII collider and corresponds to an integrated luminosity of $567{\mathrm{pb}}^{-1}$. We find the first evidence for the decay ${\mathrm{\Lambda }}_c^{+}\to p\eta$ with a statistical significance of $4.2\sigma$ and measure its branching fraction to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p\eta )=(1.24\pm 0.28(\text{stat})\pm 0.10(\mathrm{syst}))\times {10}^{-3}$. No significant ${\mathrm{\Lambda }}_c^{+}\to p{\pi }^0$ signal is observed. We set an upper limit on its branching fraction $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{\pi }^0)<2.7\times {10}^{-4}$ at the 90% confidence level.

We study the elastic scattering of a planar wave in the curved spacetime of a compact object such as a neutron star, via a heuristic model: a scalar field impinging upon a spherically symmetric uniform density star of radius $R$ and mass $M$. For $R<r_c$, there is a divergence in the deflection function at the light-ring radius $r_c=3GM/c^2$, which leads to spiral scattering (orbiting) and a backward glory; whereas for $R>r_c$, there instead arises a stationary point in the deflection function which creates a caustic and rainbow scattering. As in nuclear rainbow scattering, there is an Airy-type oscillation on a Rutherford-like cross section, followed by a shadow zone. We show that, for $R\sim 3.5GM/c^2$, the rainbow angle lies close to 180°, and thus there arises enhanced backscattering and glory. We explore possible implications for gravitational wave astronomy and dark matter models.

In this paper we address the two-body problem in massless scalar-tensor (ST) theories within an effective-one-body (EOB) framework. We focus on the first building block of the EOB approach, that is, mapping the conservative part of the two-body dynamics onto the geodesic motion of a test particle in an effective external metric. To this end, we first deduce the second post-Keplerian (2PK) Hamiltonian of the two-body problem from the known 2PK Lagrangian. We then build, by means of a canonical transformation, a ST deformation of the general relativistic EOB Hamiltonian that allows us to incorporate the scalar-tensor (2PK) corrections to the currently best available general relativity EOB results. This EOB-ST Hamiltonian defines a resummation of the dynamics that may provide information on the strong-field regime, in particular, the ISCO location and associated orbital frequency, and can be compared to, other, e.g., tidal, corrections.

Discordance in the $\mathrm{\Lambda }$ cold dark matter cosmological model can be seen by comparing parameters constrained by cosmic microwave background (CMB) measurements to those inferred by probes of large scale structure. Recent improvements in observations, including final data releases from both Planck and SDSS-III BOSS, as well as improved astrophysical uncertainty analysis of CFHTLenS, allows for an update in the quantification of any tension between large and small scales. This paper is intended, primarily, as a discussion on the quantifications of discordance when comparing the parameter constraints of a model when given two different data sets. We consider Kullback-Leibler divergence, comparison of Bayesian evidences and other statistics which are sensitive to the mean, variance and shape of the distributions. However, as a byproduct, we present an update to the similar analysis in [R. A. Battye, T. Charnock, and A. Moss, Phys. Rev. D 91, 103508 (2015)], where we find that, considering new data and treatment of priors, the constraints from the CMB and from a combination of large scale structure (LSS) probes are in greater agreement and any tension only persists to a minor degree. In particular, we find the parameter constraints from the combination of LSS probes which are most discrepant with the $\mathrm{Planck}2015+\mathrm{Pol}+\mathrm{BAO}$ parameter distributions can be quantified at a $\sim 2.55\sigma$ tension using the method introduced in [R. A. Battye, T. Charnock, and A. Moss, Phys. Rev. D 91, 103508 (2015)]. If instead we use the distributions constrained by the combination of LSS probes which are in greatest agreement with those from $\mathrm{Planck}2015+\mathrm{Pol}+\mathrm{BAO}$ this tension is only $0.76\sigma$.

Current measurements of the temperature and polarization anisotropy power spectra of the cosmic microwave background (CMB) seem to indicate that the naive expectation for the slow-roll hierarchy within the most simple inflationary paradigm may not be respected in nature. We show that a primordial power spectrum with localized features could in principle give rise to the observed slow-roll anarchy when fitted to a featureless power spectrum. From a model comparison perspective, and assuming that nature has chosen a featureless primordial power spectrum, we find that, while with mock Planck data there is only weak evidence against a model with localized features, upcoming CMB missions may provide compelling evidence against such a nonstandard primordial power spectrum. This evidence could be reinforced if a featureless primordial power spectrum is independently confirmed from bispectrum and/or galaxy clustering measurements.

We investigate the classical and quantum behavior of a Bianchi I model in the presence of a stiff matter contribution when the Vilenkin interpretation of the wave function of the Universe is taken into account. We study its evolution in the so-called polymer representation of quantum mechanics, in order to characterize the modifications that a discrete nature in the isotropic variable of the Universe induces on the morphology of the cosmological singularity. We demonstrate that in such a model the big-bang singularity is removed at a semiclassical level in favor of a big bounce when a lattice on the isotropic variable is considered. Furthermore, the analysis of the mean values on the quantum degrees of freedom, i.e., the variables ${\beta }_{+},{\beta }_{-}$ in the Misner picture, and the investigation on the evolution of the wave packets show how the typical diverging behavior associated to the anisotropies of the Universe in proximity of the initial singularity disappears in our polymer modified scheme. Indeed, the anisotropies remain finite across the big bounce and they assume a value that depends on the initial conditions fixed far from the turning point. Finally, we demonstrate that the proposed scenario can be extended, with a suitable choice of the configuration parameters, to the Bianchi IX cosmology and therefore it can be regarded as a paradigm for the generic cosmological model.

Dark matter capture and annihilation in the Sun can produce detectable high-energy neutrinos, providing a probe of the dark matter–proton scattering cross section. We consider the case when annihilation proceeds via long-lived dark mediators, which allows gamma rays to escape the Sun and reduces the attenuation of neutrinos. For gamma rays, there are exciting new opportunities, due to detailed measurements of GeV solar gamma rays with Fermi, and unprecedented sensitivities in the TeV range with HAWC and LHAASO. For neutrinos, the enhanced flux, particularly at higher energies $(\sim \mathrm{TeV})$, allows a more sensitive dark matter search with IceCube and KM3NeT. We show that these search channels can be extremely powerful, potentially improving sensitivity to the dark matter spin-dependent scattering cross section by several orders of magnitude relative to present searches for high-energy solar neutrinos, as well as direct detection experiments.

Acoustic quadrupole modes of sunlike stars vibrate when perturbed by a passing gravitational wave generated somewhere in the Universe. Here, we compute the imprint of the gravitational waves on the acoustic spectrum of these stars for gravitational events occurring near the supermassive black hole located at the center of the Milky Way. We found that in most cases the impact of gravitational waves in low-order quadrupole modes is not above the current observational threshold of detectability, although this should be in the reach of the next generation of near infrared observatories and asteroseismology satellite missions. Equally, we found that it is possible to follow the end phase of the coalescence of binaries with large chirp masses, as these phenomena have a unique imprint in the spectra of sunlike stars affecting sequentially several low-order quadrupole modes. Moreover, we discuss the different imprints on the acoustic spectra of the different types of binary systems constituted either by two white dwarfs, two neutron stars, two black holes or a compact star and a massive black hole.

We develop a coordinate version of light-cone-ordered perturbation theory, for general time-ordered products of fields, by carrying out integrals over one light-cone coordinate for each interaction vertex. The resulting expressions depend on the lengths of paths, measured in the same light-cone coordinate. Each path is associated with a denominator equal to a “light-cone deficit,” analogous to the “energy deficits” of momentum-space time- or light-cone-ordered perturbation theory. In effect, the role played by intermediate states in momentum space is played by paths between external fields in coordinate space. We derive a class of identities satisfied by coordinate diagrams, from which their imaginary parts can be derived. Using scalar QED as an example, we show how the eikonal approximation arises naturally when the external points in a Green function approach the light cone, and we give applications to products of Wilson lines. Although much of our discussion is directed at massless fields in four dimensions, we extend the formalism to massive fields and dimensional regularization.

We present a Peccei-Quinn (PQ)-symmetric two-Higgs doublet model that naturally predicts a fermionic singlet dark matter in the mass range 10 keV–1 GeV. The origin of the smallness of the mass of this light singlet fermion arises predominantly at the one-loop level, upon soft or spontaneous breakdown of the PQ symmetry via a complex scalar field in a fashion similar to the so-called Dine-Fischler-Sredniki-Zhitnitsky axion model. The mass generation of this fermionic radiative light dark matter (RLDM) requires the existence of two heavy vectorlike SU(2) isodoublets, which are not charged under the PQ symmetry. We show how the RLDM can be produced via the freeze-in mechanism, thus accounting for the missing matter in the Universe. Finally, we briefly discuss possible theoretical and phenomenological implications of the RLDM model for the strong $CP$ problem and the CERN Large Hadron Collider (LHC).

We study the collider phenomenology of the extended Higgs sector of the next-to-minimal supersymmetric Standard Model (NMSSM). The region of NMSSM parameter space favored by a 125 GeV SM-like Higgs and naturalness generically features a light Higgs and neutralino spectrum as well as a large $\mathcal{O}(1)$ coupling between the Higgs doublets and the NMSSM singlet fields. In such regimes, the heavier Higgs bosons can decay dominantly into lighter Higgs bosons and neutralinos. We study the prospects of observing such decays at the 13 TeV LHC, focusing on mono-Higgs signatures as probes of such regions of parameter space. We present results for the mono-Higgs reach in a framework easily applicable to other models featuring similar decay topologies. In the NMSSM, we find that the mono-Higgs channel can probe TeV scale Higgs bosons and has sensitivity even in the low $\tan \beta$, large $m_A$ regime that is difficult to probe in the MSSM. Unlike for many conventional Higgs searches, the reach of the mono-Higgs channel will improve significantly with the increased luminosity expected to be collected at the LHC in the ongoing and upcoming runs.