We point out that the relative Heisenberg uncertainty relations vanish for noncompact spaces in homogeneous loop quantum cosmology. As a consequence, for sharply peaked states quantum fluctuations in the scale factor never become important, even near the bounce point. This shows why quantum backreaction effects remain negligible and explains the surprising accuracy of the effective equations in describing the dynamics of sharply peaked wave packets. This also underlines the fact that minisuperspace models—where it is global variables that are quantized—do not capture the local quantum fluctuations of the geometry.

The gamma-ray excess observed from the Galactic Center can be interpreted as dark matter particles annihilating into standard model fermions with a cross section near that expected for a thermal relic. Although many particle physics models have been shown to be able to account for this signal, the fact that this particle has not yet been observed in direct detection experiments somewhat restricts the nature of its interactions. One way to suppress the dark matter’s elastic scattering cross section with nuclei is to consider models in which the dark matter is part of a hidden sector. In such models, the dark matter can annihilate into other hidden sector particles, which then decay into standard model fermions through a small degree of mixing with the photon, $Z$, or Higgs bosons. After discussing the gamma-ray signal from hidden sector dark matter in general terms, we consider two concrete realizations: a hidden photon model in which the dark matter annihilates into a pair of vector gauge bosons that decay through kinetic mixing with the photon, and a scenario within the generalized next-to-minimal supersymmetric standard model in which the dark matter is a singlino-like neutralino that annihilates into a pair of singlet Higgs bosons, which decay through their mixing with the Higgs bosons of the minimal supersymmetric standard model.

We propose a novel model-independent method to search for $W^{\prime }$ bosons at the Large Hadron Collider by looking at dijets where one jet is identified as a boosted-top jet and another jet is tagged as a boosted-bottom jet. Performing a detector-simulated signal and background study, we demonstrate that the reach in effective coupling $g^{\prime }$ is improved over existing analysis methods by up to factor of 2 for $W^{\prime }$ masses above 1.5 TeV, and the reach in mass is extended by 600 GeV to 2.6 TeV at an 8-TeV Large Hadron Collider. We introduce a method for distinguishing high-energy $b$ jets from light-quark jets and describe an important set of backgrounds to top jets. We propose a series of data-driven samples that might be used to measure the efficiencies for these new backgrounds in the LHC data.

In this paper we study Yukawa-unified SO(10) supersymmetric (SUSY) grand unified theories (GUTs) with two types of SO(10) boundary conditions: (i) universal gaugino masses and (ii) nonuniversal gaugino masses with effective “mirage” mediation. With these boundary conditions, we perform a global ${\chi }^2$ analysis to obtain the parameters consistent with 11 low energy observables, including the top, bottom, and tau masses. Both boundary conditions have universal scalar masses and “just so” splitting for the up- and down-type Higgs masses. In these models, the third family scalars are lighter than the first two families and the gauginos are lighter than all the scalars. We therefore focus on the gluino phenomenology in these models. In particular, we estimate the lowest allowed gluino mass in our models coming from the most recent LHC data and compare this to limits obtained using simplified models. We find that the lower bound on $M_{\tilde{g}}$ in Yukawa-unified SO(10) SUSY GUTs is generically $\sim 1.2\mathrm{TEV}$ at the $1\sigma$ level unless there is considerable degeneracy between the gluino and the lightest supersymmetric particle, in which case the bounds are much weaker. Hence many of our benchmark points are not ruled out by the present LHC data and are still viable models which can be tested at LHC 14.

We investigate constraints on the properties of light dark matter which can be obtained from analysis of invisible quarkonium decays at high intensity electron-positron colliders in the framework of a low energy effective field theory. A matrix element analysis of all contact operators pertinent for these meson decays allows for a model-independent calculation of associated dark-matter–nucleon scattering and dark matter annihilation cross sections. Assuming dark matter couples universally to all quark flavors, we then obtain bounds on nucleon scattering which complement direct dark matter detection searches. In contrast to similar analyses of monojet searches at high energy colliders, B and charm factories are more suitable probes of light dark matter interactions with less massive mediators. Relevant bounds on dark matter annihilation arising from gamma ray searches of dwarf spheroidal galaxies are also presented.

We perform a $N_f=2+1$ lattice QCD simulation to determine the quark spin fractions of hadrons using the Feynman-Hellmann theorem. By introducing an external spin operator to the fermion action, the matrix elements relevant for quark spin fractions are extracted from the linear response of the hadron energies. Simulations indicate that the Feynman-Hellmann method offers statistical precision that is comparable to the standard three-point function approach, with the added benefit that it is less susceptible to excited-state contamination. This suggests that the Feynman-Hellmann technique offers a promising alternative for calculations of quark line disconnected contributions to hadronic matrix elements. At the SU(3)-flavor symmetry point, we find that the connected quark spin fractions are universally in the range 55%–70% for vector mesons and octet and decuplet baryons. There is an indication that the amount of spin suppression is quite sensitive to the strength of SU(3) breaking.

We study the single-spin asymmetries with the $\sin {\varphi }_S$ and $\sin (2{\varphi }_h-{\varphi }_S)$ angular dependences for charged and neutral pions produced in semi-inclusive deep inelastic scattering on the transversely polarized proton target. The theoretical interpretations of the two asymmetries are presented in terms of the convolution of the twist-3 quark transverse momentum dependent distributions and twist-2 fragmentation functions. Specifically, we investigate the role of the distributions $f_T$, $h_T$, and $h_T^{\perp }$ in the $\sin {\varphi }_S$ asymmetry, as well as the role of the distributions $f_T^{\perp }$, $h_T$, and $h_T^{\perp }$ in the $\sin (2{\varphi }_h-{\varphi }_S)$ asymmetry. We calculate these distributions in a spectator-diquark model and predict the corresponding asymmetries for the first time, considering the kinematics at HERMES, JLab, and COMPASS. The numerical estimates show that the asymmetries are sizable, and the dominant contribution to the $\sin {\varphi }_S$ asymmetry comes from the T-odd distribution $f_T$, while $f_T^{\perp }$ gives the main contribution to the $\sin (2{\varphi }_h-{\varphi }_S)$ asymmetry. The future measurements on these asymmetries can shed light on the information of twist-3 transverse momentum dependent distributions.

We construct a theoretical framework to match the formulas for forward inclusive hadron productions in $pA$ collisions in the small $x$ saturation formalism and collinear factorization. The small $x$ calculation can be viewed as a power series in $Q_s^2/k_{\perp }^2$, in which the collinear factorization result corresponds to the leading term. At high transverse momentum, the subleading correction terms are insignificant, whereas at low $p_{\perp }$, the power corrections become important and the small $x$ resummation is essential to describe the differential cross section. We show that the familiar collinear factorization calculation can smoothly match the results from small $x$ factorization at next-to-leading order in ${\alpha }_s$ when we use exact kinematics, as opposed to the approximate kinematics in previous work. With this matching, we can describe the experimental data from the RHIC very well at high $p_{\perp }$.

The most natural supersymmetric solution to the hierarchy problem prefers the scalar top partner to be close in mass to the top quark. Experimental searches exclude top squarks across a wide range of masses, but a gap remains when the difference between the masses of the stop and the lightest supersymmetric particle is close to the top mass. We propose to search for stops in this regime by exploiting the azimuthal angular correlation of forward tagging jets in (s)top pair production. As shown in earlier work, this correlation is sensitive to the spin of the heavy states, allowing one to distinguish between top and stop pair production. Here, we demonstrate that this angular information can give a statistically significant stop pair production signal in the upcoming LHC run. While the appropriate simulation including parton showering and detector simulation requires some care, we find stable predictions for the angular correlation using multijet merging.

We systematically calculate the relativistic corrections to prompt $J/\psi$ photoproduction and hadroproduction using the factorization formalism of nonrelativistic QCD. Specifically, we include the ${{}^{3}S}_1^{[1]}$ and ${{}^{3}P}_J^{[1]}$ color-singlet and the ${{}^{3}S}_1^{[8]}$, ${{}^{1}S}_0^{[8]}$, and ${{}^{3}P}_J^{[8]}$ color-octet channels as well as the effects due to the mixing between the ${{}^{3}S}_1^{[8]}$ and ${{}^{3}D}_1^{[8]}$ channels. We provide all the squared hard-scattering amplitudes in analytic form. Assuming the nonrelativistic-QCD long-distance matrix elements to satisfy the velocity scaling rules, we find the relativistic corrections to be appreciable, except in the ${{}^{3}S}_1^{[1]}$ color-singlet channel of hadroproduction. We also observe significant differences in the line shapes of the relativistic corrections between photoproduction and hadroproduction.

Many of the $XYZ$ mesons discovered in the last decade can be identified as bound states in Born-Oppenheimer (B-O) potentials for a heavy quark and antiquark. They include quarkonium hybrids, which are bound states in excited flavor-singlet B-O potentials, and quarkonium tetraquarks, which are bound states in flavor-nonsinglet B-O potentials. We present simple parametrizations of the deepest flavor-singlet B-O potentials. We infer the deepest flavor-nonsinglet B-O potentials from lattice QCD calculations of static adjoint mesons. Selection rules for hadronic transitions are used to identify $XYZ$ mesons that are candidates for ground-state energy levels in the B-O potentials for charmonium hybrids and tetraquarks. The energies of the lowest-energy charmonium hybrids are predicted by using the results of lattice QCD calculations to calculate the energy splittings between the ground states of different B-O potentials and using the Schrödinger equation to determine the splittings between energy levels within a B-O potential.

Gluon-initiated double Higgs production is the most important channel to extract the Higgs self-coupling at hadron colliders. However, new physics could enter into this channel in several distinctive ways including, but not limited to, the Higgs self-coupling, a modified top Yukawa coupling, and an anomalous Higgs-top quartic coupling. In this work we initiate a study on the interplay of these effects in the kinematic distributions of the Higgs bosons. More specifically, we divide the $p_T$ and the total invariant mass spectra into two bins and use the differential rates in each bin to constrain the magnitude of the aforementioned effects. Significantly improved results could be obtained over those using the total cross section alone. However, some degeneracy remains, especially in the determination of the Higgs trilinear coupling. Therefore, an accurate measurement of the Higgs self-coupling in this channel would require precise knowledge of the magnitudes of other new physics effects. We base our analysis on a future $pp$ collider at $\sqrt{s}=100\mathrm{TeV}$.

With the advent of detectors with sub-keV sensitivities, atomic ionization has been identified as a promising avenue to probe possible neutrino electromagnetic properties. The interaction cross sections induced by millicharged neutrinos are evaluated with the ab initio multiconfiguration relativistic random-phase approximation. There is significant enhancement at atomic binding energies compared to that when the electrons are taken as free particles. Positive signals would distinctly manifest as peaks at specific energies with known intensity ratios. Selected reactor neutrino data with germanium detectors at an analysis threshold as low as 300 eV are studied. No such signatures are observed, and a combined limit on the neutrino charge fraction of $|{\delta }_{\mathrm{Q}}|<1.0\times {10}^{-12}$ at 90% confidence level is derived.

We study the dynamics of classical correlation, quantum discord, and measurement-induced disturbance of Dirac fields in the background of a dilaton black hole. We present an alternative physical interpretation of single mode approximation for Dirac fields in black hole spacetimes. We show that the classical and quantum correlations are degraded as the increase of black hole’s dilaton. We find that, comparing to the inertial systems, the quantum correlation measured by the one-side measuring discord is always not symmetric with respect to the measured subsystems, while the measurement-induced disturbance is symmetric. The symmetry of classical correlation and quantum discord is influenced by gravitation produced by the dilaton of the black hole.

Strings at $T\approx T_c$ are known to be subject to the so-called Hagedorn phenomenon, in which a string’s entropy (times $T$) and energy cancel each other and result in the evolution of the string into highly excited states, or “string balls.” Intrinsic attractive interaction of strings—gravitational for fundamental strings or in the context of holographic models of the AdS/QCD type, or $\sigma$ exchanges for QCD strings—can significantly modify properties of the string balls. If heavy enough, those start approaching properties of the black holes. We generate self-interacting string balls numerically, in a thermal string lattice model. We found that in a certain range of the interaction coupling constants they morph into a new phase, the “entropy-rich” string balls. These objects can appear in the so-called mixed phase of hadronic matter, produced in heavy ion collisions, as well as possibly in the high multiplicity proton-proton or proton-nucleus collisions. Among discussed applications are jet quenching in the mixed phase and also the study of angular deformations of the string balls.

This paper discusses the relationships between gauge theories defined by gauge groups with finite trivially acting centers and theories with restrictions on nonperturbative sectors, in two and four dimensions. In two dimensions, these notions seem to coincide. Generalizing old results on orbifolds and Abelian gauge theories, we propose a decomposition of two-dimensional non-Abelian gauge theories with center-invariant matter into disjoint sums of theories with rotating discrete theta angles; for example, schematically, $SU(2)=SO(3{)}_{+}+SO(3{)}_{-}$. We verify that decomposition directly in pure nonsupersymmetric two-dimensional Yang-Mills as well as in supersymmetric theories. In four dimensions, by contrast, these notions do not coincide. To clarify the relationship, we discuss theories obtained by restricting nonperturbative sectors. These theories violate cluster decomposition, but we illustrate how they may at least in special cases be understood as disjoint sums of well-behaved quantum field theories, and how dyon spectra can be used to distinguish, for example, an $SO(3)$ theory with a restriction on instantons from an $SU(2)$ theory. We also briefly discuss how coupling various analogues of Dijkgraaf-Witten theory, as part of a description of instanton restriction via coupling topological field theories to quantum field theories, may modify these results.

We present stable de Sitter solutions of $\mathcal{N}=1$ supergravity in a geometric type IIB duality frame with the addition of nonperturbative contributions. Contrary to the standard approach, we retain the moduli dependence of both the tree-level superpotential and its nonperturbative contribution. This provides the possibility for a single-step stabilization of all moduli simultaneously in a de Sitter vacuum. Using a genetic algorithm we find explicit solutions with different features.

We calculate the singular field of an accelerated point particle (scalar charge, electric charge or small gravitating mass) moving on an accelerated (nongeodesic) trajectory in a generic background spacetime. Using a mode-sum regularization scheme, we obtain explicit expressions for the self-force regularization parameters. We use a Lorentz gauge for the electromangetic and gravitational cases. This work extends the work of Barack and Ori [1] who demonstrated that the regularization parameters for a point particle in geodesic motion in a Schwarzschild spacetime can be described solely by the leading and subleading terms in the mode-sum (commonly known as the $A$ and $B$ terms) and that all terms of higher order in $\ell$ vanish upon summation (later they showed the same behavior for geodesic motion in Kerr [2], [3]). We demonstrate that these properties are universal to point particles moving through any smooth spacetime along arbitrary (accelerated) trajectories. Our renormalization scheme is based on, but not identical to, the Quinn-Wald axioms. As we develop our approach, we review and extend work showing that that different definitions of the singular field used in the literature are equivalent to our approach. Because our approach does not assume geodesic motion of the perturbing particle, we are able use our mode-sum formalism to explicitly recover a well-known result: The self-force on static scalar charges near a Schwarzschild black hole vanishes.

We investigate the tensor perturbation in the inflation model driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. For short-wavelength modes, the perturbation feature is very similar to that of the usual chaotic inflation. For long-wavelength modes, the perturbation exhibits a peculiar rise in the power spectrum which may leave a signature in the cosmic microwave background radiation.