We study spatial correlation functions of charmonium in $2+1$ flavor QCD using an improved staggered formulation. Contrary to the temporal correlation functions the spatial correlation functions exhibit a strong temperature dependence above the QCD transition temperature. Above this temperature they are sensitive to temporal boundary conditions. Both features become significant at a temperature close to $1.5T_c$ and suggest corresponding modifications of charmonium spectral functions.

If the $c$ quark has an anomalous color-electric dipole moment (CEDM), it may serve as a new source of $CP$ violation. The strength of such a $CP$ violation depends on the size of the CEDM, $d_c^{\prime }$. We propose two effective ways of testing it from the large sample of ${\psi }^{\prime }\to J/\psi +{\pi }^{+}+{\pi }^{-}$ at the Beijing Spectrometer, and the obtained result, $|d_c^{\prime }|<3\times {10}^{-14}\mathrm{e}\mathrm{cm}$ (95% confidence level), gives the first experimentally determined upper bound on the CEDM of the $c$ quark.

We derive a factorization formula for the double Drell-Yan cross section in terms of double parton distribution functions (dPDFs). Diparton flavor, spin and color correlations and parton-exchange interference terms contribute, even for unpolarized beams. Soft radiation effects are nontrivial for the color correlation and interference contributions and are described by nonperturbative soft functions. We provide a field-theoretic definition of the quark dPDFs and study some of their basic properties, including discrete symmetries and their interpretation in a nonrelativistic quark model. We calculate the renormalization group evolution of the quark dPDFs and of the soft functions. The evolution receives contributions from both ultraviolet and rapidity divergences. We find that color correlation and interference effects are Sudakov suppressed, greatly reducing the number of dPDFs needed to describe double parton scattering at high-energy experiments.

We investigate chiral symmetry breaking and strong $CP$ violation effects in the phase diagram of strongly interacting matter. We demonstrate the effect of strong $CP$ violating terms on the phase structure at finite temperature and densities in a three-flavor Nambu-Jona-Lasinio model including the Kobayashi-Maskawa-t’ Hooft determinant term. This is investigated using an explicit structure for the ground state in terms of quark-antiquark condensates for both the scalar and the pseudoscalar channels. $CP$ restoring transition with temperature at zero baryon density is found to be a second order transition at $\theta =\pi$ while the same at finite chemical potential and small temperature turns out to be a first order transition. Within the model, the tricritical point is found to be $({\mu }_c,T_c)\simeq (273,94)\mathrm{MeV}$ at $\theta =\pi$ for such a transition.

The strong-isospin violation in $\psi (3770)\to J/\psi +{\pi }^0$ via intermediate $D$ meson loops is investigated in an effective Lagrangian approach. In this process, there is only one $D$-meson loop contributing to the absorptive part, and the uncertainties due to the introduction of form factors can be minimized. With the help of QCD spectral sum rules (QSSR), we extract the $J/\psi D{D}^{*}$ form factor as an implement from the first principle of QCD. The $D{D}^{*}{\pi }^0$ form factor can be well determined from the experimental data for $D\to \pi l\nu$. The exploration of the dispersion relation suggests the dominance of the dispersive part via the intermediate $D$ meson loops even below the open charm threshold. This investigation could provide further insights into the puzzling question on the mechanisms for $\psi (3770)\to$ non-$D\overline{D}$ transitions.

Within the framework of the perturbative QCD approach, we study the two-body charmless decays $B\to a_1(1260)(b_1(1235))\rho (\omega ,\varphi )$ and $B_s\to a_1(1260)(b_1(1235))P(V)$, where, $P$, $V$ stand for any light pseudoscalar meson and vector meson, respectively. We find the following results: (a) With the exception of the decays ${\overline{B}}^0\to a_1^0{\rho }^0(\omega )$, other tree-dominated decays $B\to a_1\rho (\omega )$ have larger branching ratios of order ${10}^{-5}$. With the exception of the decays $\overline{B}\to b_1^{+}{\rho }^{-}$ and $B^{-}\to b_1^0{\rho }^{-}$, other $B\to b_1\rho (\omega )$ decays have smaller branching ratios of order ${10}^{-6}$. The decays $B\to a_1(b_1)\varphi$ are highly suppressed and have very small branching ratios of order ${10}^{-9}$. (b) The decays ${\overline{B}}_s^0\to a_1^{-}{K}^{+}(K^{*+})$ have contributions from the factorization emission diagrams with a large Wilson coefficient $C_2+C_1/3$, so they have the largest branching ratios and arrive at the order of ${10}^{-5}$. For the decays ${\overline{B}}_s^0\to b_{1}K(K^{*})$, $a_1\pi$, all of their branching ratios are of order a few times ${10}^{-6}$. The branching ratios of other decays fall in the order of ${10}^{-7}-{10}^{-9}$. (c) For the decays ${\overline{B}}^0\to a_1^0{\rho }^0$ and $B^{-}\to b_1^{-}{\rho }^0$, their two transverse polarizations are larger than their longitudinal polarizations, which are about 43.3% and 44.9%, respectively. (d) With the exception of the decays ${\overline{B}}_s^0\to a_1^0{K}^{*0}$, $a_1^0\omega$, $b_1^0\omega$, the longitudinal polarization fractions of other ${\overline{B}}_s^0\to a_1(b_1)V$ decays are very large and more than 90%. (e) For the decays $B^{-}\to a_1^0{\rho }^{-}$, $b_1^0{\rho }^{-}$ and ${\overline{B}}^0\to b_1^0{\rho }^0$, $b_1^0\omega$, where the transverse polarization fractions range from 4.7 to 7.5%, we calculate their direct $CP$-violating asymmetries, neglecting the transverse polarizations and find that those for two charged decays have smaller values, which are about 11.8% and $-3.7\%$, respectively. Compared with the decays ${\overline{B}}_s^0\to a_1(b_1)P$, most of the ${\overline{B}}_s^0\to a_1(b_1)V$ decays have smaller direct $CP$ asymmetries.

We revisit our previous results on the matter suppression of self-induced neutrino flavor conversions during a supernova (SN) accretion phase, performing a linearized stability analysis of the neutrino equations of motion, in the presence of realistic SN density profiles. In our previous numerical study, we used a simplified model based on an isotropic neutrino emission with a single typical energy. Here, we take into account realistic neutrino energy and angle distributions. We find that multienergy effects have a subleading impact in the flavor stability of the SN neutrino fluxes with respect to our previous single-energy results. Conversely, realistic forward-peaked neutrino angular distributions would enhance the matter suppression of the self-induced oscillations with respect to an isotropic neutrino emission. As a result, in our models for iron-core SNe, collective flavor conversions have a negligible impact on the characterization of the observable neutrino signal during the accretion phase. Instead, for a low-mass O-Ne-Mg core SN model, with lower matter density profile and less forward-peaked angular distributions, collective conversions are possible also at early times.

We consider scalar field perturbations about asymptotically Lifshitz black holes with dynamical exponent $z$ in $D$ dimensions. We show that, for suitable boundary conditions, these Lifshitz black holes are stable under scalar field perturbations. For $z=2$, we explicitly compute the quasinormal mode frequencies, which result to be purely imaginary, and then obtain the damping-off of the scalar field perturbation in these backgrounds. The general analysis includes, in particular, the $z=3$ black hole solution of three-dimensional massive gravity.

The effect of some possible nonstandard weakly interacting massive particle velocity distributions, like the debris flows recently proposed, on the direct dark matter detection rates is investigated. We find that such distributions may be deciphered from the data, especially if the time variation of the event rates due to the annual motion of the Earth is observed.

We investigate the cosmic evolution of the linear bias in the framework of a flat Friedmann-Lemaître-Robertson-Walker spacetime. We consider metric perturbations in the Newtonian gauge, including Hubble scale effects. Making the following assumptions, (i) scale-independent current epoch bias $b_0$, (ii) equal accelerations between tracers and matter, (iii) unimportant halo merging effects (which is quite accurate for $z<3$), we analytically derive the scale-dependent bias evolution. The identified scale dependence is only due to Hubble scale evolution general relativity effects, while other scale dependence contributions are ignored. We find that up to galaxy cluster scales the fluctuations of the metric do not introduce a significant scale dependence in the linear bias. Our bias evolution model is then used to derive a connection between the matter growth index $\gamma$ and the observable value of the tracer power spectrum normalization ${\sigma }_8(z)$. We show how this connection can be used as an observational test of general relativity on extragalactic scales.

We study Higgs boson production from gluon-gluon fusion at midrapidity in high energy proton-nucleus collisions. For this process the presently still little known gluon distribution function $h_1^{\perp g}(x,k_{\perp })$ might give a numerically relevant contribution. We show by explicit calculation that using color glass condensate model input the result obtained in the naive $k_t$ factorization approach matches the result obtained in the transverse momentum dependent factorization framework for a dilute medium. We also verify the earlier finding [P. Sun, B.-W. Xiao, and F. Yuan, Phys. Rev. D 84, 094005 (2011)] that the $k_t$ factorization formalism for Higgs production breaks down in a dense medium. In doing so, we formulate a hybrid model which allows one to treat such reactions theoretically.

With nonrelativistic QCD factorization, we calculate the ${\rm Y}(1S)$ prompt production at hadron colliders at next-to-leading order in ${\alpha }_s$. In addition to the color-singlet contribution, color-octet channels (especially the $P$-wave channel) up to $O(v^4)$ are all considered. Aside from direct production, the feed-down contributions from higher excited $S$-wave and $P$-wave $b\overline{b}$ states to ${\rm Y}(1S)$ production are also included. We use the potential model estimates as input for color-singlet long-distance matrix elements (LDMEs). While for color-octet contributions, we find they can be approximately described by three LDMEs: $⟨\mathcal{O}({}^{3}S_1^{[8]})⟩$, $⟨\mathcal{O}({}^{1}S_0^{[8]})⟩$ and $⟨\mathcal{O}({}^{3}P_0^{[8]})⟩$. By fitting the Tevatron data we can determine some linear combinations of these LDMEs, and then use them to predict ${\rm Y}(1S)$ production at the LHC. Our predictions are consistent with the new experimental data of CMS and LHCb.

Radiative decays of $X(3872)$ with $J^{\mathrm{PC}}=1^{++}$ are studied in the coupled-channel approach, where the $c\overline{c}$ states are described by the relativistic string Hamiltonian, while for the decay channels $D{D}^{*}$ a string-breaking mechanism is used. Within this method a sharp peak and correct mass shift of the $2{}^{3}P_1$ charmonium state just to the $D^0{D}^{*0}$ threshold was already obtained for a prescribed channel coupling to the $D{D}^{*}$ decay channels. For the same value of coupling the normalized wave function (w.f.) of $X(3872)$ acquires admixture of the $1{}^{3}P_1$ component with the weight $c_1=0.153$ ($\theta =8.8°$), which increases the transition rate $\Gamma (X(3872)\to J/\psi \gamma )$ up to 50–70 keV, making the ratio $R=\frac{\mathcal{B}(X(3872)\to {\psi }^{\prime }\gamma )}{\mathcal{B}(X(3872)\to J/\psi \gamma )}=0.8\pm 0.2(\mathrm{th})$ significantly smaller, as compared to $R\simeq 5$ for $X(3872)$ as a purely $2{}^{3}P_1$ state.

Quark contact interactions are an important signal of new physics. We introduce a model in which the presence of a symmetry protects these new interactions from giving large corrections in flavor changing processes at low energies. This minimal model provides the basic set of operators which must be considered to contribute to the high-energy processes. To discuss their experimental signature in jet pairs produced in proton-proton collisions, we simplify the number of possible operators down to two. We show (for a representative integrated luminosity of $200{\mathrm{pb}}^{-1}$ at $\sqrt{s}=7\mathrm{TeV}$) how the presence of two operators significantly modifies the bound on the characteristic energy scale of the contact interactions, which is obtained by keeping a single operator.

We present the exact neutral black string solution in locally conformal invariant Weyl gravity. As a special case, the general relativity analogue still can be attained; however, only as a subfamily of solutions. Our solution contains a linear term that would thus result in a potential that grows linearly over large distances. This may have implications for exotic astrophysical structures as well as matter fields on the extremely small scale.

We discuss the model selection problem for inflationary cosmology. We couple ModeCode, a publicly available numerical solver for the primordial perturbation spectra, to the nested sampler MultiNest, in order to efficiently compute Bayesian evidence. We pay particular attention to the specification of physically realistic priors, including the parametrization of the post-inflationary expansion and associated thermalization scale. It is confirmed that, while present-day data tightly constrain the properties of the power spectrum, they cannot usefully distinguish between the members of a large class of simple inflationary models. We also compute evidence using a simulated Planck likelihood, showing that while Planck will have more power than WMAP to discriminate between inflationary models, it will not definitively address the inflationary model selection problem on its own. However, Planck will place very tight constraints on any model with more than one observationally distinct inflationary regime—e.g. the large- and small-field limits of the hilltop inflation model—and put useful limits on different reheating scenarios for a given model.

Some time ago, an accurate phenomenological approach, the BSW model, was developed for proton-proton and antiproton-proton elastic scattering cross sections at center-of-mass energies above 10 GeV. This model has been used to give successful theoretical predictions for these processes, at successive collider energies. The BSW model involves a combination of integrals that, while computable numerically at fairly high energies, require some mathematical analysis to reveal the high-energy asymptotic behavior. In this paper we present a high-energy asymptotic representation of the scattering amplitude at moderate momentum transfer, for the leading order in an expansion parameter closely related to the logarithm of the center-of-mass energy. The fact that the expansion parameter goes as the logarithm of the energy means that the asymptotic behavior is accurate only for energies greatly beyond any foreseeable experiment. However, we compare the asymptotic representation against the numerically calculated model for energies in a less extreme region of energy. The asymptotic representation is given by a simple formula which, in particular, exhibits the oscillations of the differential cross section with momentum transfer. We also compare the BSW asymptotic behavior with the Singh-Roy unitarity upper bound for the diffraction peak.

We consider a model combining technicolor with the top-quark condensation. As a concrete model for technicolor, we use the minimal walking technicolor, and this will result in the appearance of a novel fourth generation whose leptons constitute a usual weak doublet while the QCD quarks are vectorlike singlets under the weak interactions. We carry out an analysis of the mass spectra and precision measurement constraints, and find the model viable. We contrast the model with present LHC data and discuss the future prospects.

We present an analytic description of numerical results for the Landau-gauge SU(2) gluon propagator $D(p^2)$, obtained from lattice simulations (in the scaling region) for the largest lattice sizes to date, in $d=2$, 3 and 4 space-time dimensions. Fits to the gluon data in $3d$ and in $4d$ show very good agreement with the tree-level prediction of the refined Gribov-Zwanziger (RGZ) framework, supporting a massive behavior for $D(p^2)$ in the infrared limit. In particular, we investigate the propagator’s pole structure and provide estimates of the dynamical mass scales that can be associated with dimension-two condensates in the theory. In the $2d$ case, fitting the data requires a noninteger power of the momentum $p$ in the numerator of the expression for $D(p^2)$. In this case, an infinite-volume-limit extrapolation gives $D(0)=0$. Our analysis suggests that this result is related to a particular symmetry in the complex-pole structure of the propagator and not to purely imaginary poles, as would be expected in the original Gribov-Zwanziger scenario.

We evaluate exclusive semileptonic decays of ground-state spin-$1/2$ and spin-$3/2$ doubly heavy $cb$ baryons driven by a $c\to s$, $d$ transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model-independent, though approximate, predictions for ratios of decay widths.