Motivated by CDF Collaboration recent measurements on di-jet invariant mass spectrum, where di-jet is associated with charged leptons ($e/\mu$) and missing energy, we reexamined the previous proposed massive color-octet axial-vectorlike boson $Z_c$. Our simulation showed that the di-jet bump around 120–160 GeV can be induced by $Z_c$ with effective coupling $g_{Z_{c}q\overline{q}}=0.2g_s$ ($q$ represents the quark other than top and $g_s$ is the strong coupling constant). Moreover our numerical investigation indicated that the top quark forward-backward asymmetry $A_{\mathrm{FB}}^t$ can be reproduced without distorting shape of differential cross section $d\sigma /d{M}_{t\overline{t}}$, provided that the $Z_c$ and top quark coupling is appropriately chosen ($g_{Z_{c}t\overline{t}}\simeq 4.5g_{Z_{c}q\overline{q}}$). Our results also showed that the theoretical $A_{\mathrm{FB}}^t$ as functions of $\Delta y$ and $M_{t\overline{t}}$ can be consistent with data within $1\sigma$ and $1.8\sigma$, respectively.

Possible $2S$ and $1D$ excited $D$ and $D_s$ states are studied, the charmed states $D(2550{)}^0$, $D^{*}(2600)$, $D(2750{)}^0$, and $D^{*}(2760)$ newly observed by the BABAR Collaboration are analyzed. The masses of these states are explored within the Regge trajectory phenomenology, and the strong decay widths are computed within the heavy-quark effective theory. Both the mass and the decay width indicate that $D(2550{)}^0$ is a good candidate for $2{}^{1}S_0$. The strong decay property of $D^{*}(2600)$ and $D_{s1}^{*}(2700{)}^{\pm }$ is described well by pure $2{}^{3}S_1$ states. If a mixing between $2{}^{3}S_1$ and $1{}^{3}D_1$ does exist, the mixing angle $\theta$ is not large and $2{}^{3}S_1$ is predominant. $D^{*}(2760)$ and $D_{\mathrm{sJ}}^{*}(2860{)}^{\pm }$ are possibly the $1{}^{3}D_3$ $D$, and $D_s$, respectively. $D(2750{)}^0$ and $D^{*}(2760)$ seem two different states, and $D(2750{)}^0$ is very possibly the $1D(2^{-},\frac{5}{2})$ though the possibility of $1D(2^{-},\frac{3}{2})$ has not been excluded. There may exist an unobserved meson $D_{\mathrm{sJ}}(2850{)}^{\pm }$ corresponding to $D_{\mathrm{sJ}}^{*}(2860{)}^{\pm }$.

A new expression for the pion form factor $F_{\pi }$ is proposed. It takes into account the pseudoscalar meson loops and the mixing of $\rho (770)$ with heavier $\rho (1450)$ and $\rho (1700)$ resonances. The expression has correct analytical properties and can be used in both timelike and spacelike kinematical regions. The comparison is made with the existing experimental data on $F_{\pi }$, collected with the detectors SND, CMD-2, KLOE, and the BABAR, restricted to energies below 1 GeV. A good description of all four data sets is obtained. In the spacelike region, upon substituting the resonance parameters found in the timelike one, one obtains $F_{\pi }$, in agreement with the measurements of the NA7 Collaboration.

The decays ${\chi }_{cJ}\to \gamma V$ ($V=\varphi$, ${\rho }^0$, $\omega$) are studied with a sample of radiative ${\psi }^{\prime }\to \gamma {\chi }_{cJ}$ events in a sample of $(1.06\pm 0.04)\times {10}^8{\psi }^{\prime }$ events collected with the BESIII detector. The branching fractions are determined to be: $\mathcal{B}({\chi }_{c1}\to \gamma \varphi )=(25.8\pm 5.2\pm 2.3)\times {10}^{-6}$, $\mathcal{B}({\chi }_{c1}\to \gamma {\rho }^0)=(228\pm 13\pm 22)\times {10}^{-6}$, and $\mathcal{B}({\chi }_{c1}\to \gamma \omega )=(69.7\pm 7.2\pm 6.6)\times {10}^{-6}$. The decay ${\chi }_{c1}\to \gamma \varphi$ is observed for the first time. Upper limits at the 90% confidence level on the branching fractions for ${\chi }_{c0}$ and ${\chi }_{c2}$ decays into these final states are determined. In addition, the fractions of the transverse polarization component of the vector meson in ${\chi }_{c1}\to \gamma V$ decays are measured to be ${0.29}_{-0.12-0.09}^{+0.13+0.10}$ for ${\chi }_{c1}\to \gamma \varphi$, $0.158\pm {0.034}_{-0.014}^{+0.015}$ for ${\chi }_{c1}\to \gamma {\rho }^0$, and ${0.247}_{-0.087-0.026}^{+0.090+0.044}$ for ${\chi }_{c1}\to \gamma \omega$, respectively. The first errors are statistical and the second ones are systematic.

To clarify the outstanding problem in charmonium production that existing theories cannot explain the observed cross sections of ${\chi }_{cJ}(J=0,1,2)$ and ratio $R_{{\chi }_c}={\sigma }_{{\chi }_{c2}}/{\sigma }_{{\chi }_{c1}}\approx 0.75$ (in contrast to the spin counting value $5/3$) at the Tevatron, we study the complete next-to-leading order radiative corrections in nonrelativistic QCD, and find next-to-leading order contributions of ${}^{3}P_J^{[1]}$ are more important than leading order at high $p_T$, and ${}^{3}P_1^{[1]}$ decreases slower than ${}^{3}P_2^{[1]}$, implying a natural explanation for the $R_{{\chi }_c}$ puzzle. By fitting $R_{{\chi }_c}$, the predicted cross sections of ${\chi }_{cJ}$ are found to agree with data. The result indicates color-octet contribution is crucially needed, thus providing a unique test for heavy quarkonium production mechanisms. Feed-down contributions of ${\chi }_{cJ}$ to prompt $J/\psi$ production are estimated to be substantial, about 30%–40% at $p_T=20\mathrm{GeV}$. Production of ${\chi }_{cJ}(J=0,1,2)$ at the LHC is also predicted.

We study the process of formation of quark phases in protoneutron stars. After calculating the phase transition between nucleonic matter and the 2SC phase at fixed entropy and lepton fraction, we show that an unpairing transition between the 2SC phase and the normal quark phase occurs for low lepton fractions. We then calculate the process of diffusion of neutrinos in protoneutron stars and show that for intermediate values of the mass of the star, the deleptonization triggers the phase transition between the two quark phases after a temporal delay of a few seconds. In less massive stars instead only the normal quark phase is formed at the end of the deleptonization stage. We also discuss the possible astrophysical implications of our scenario.

We reconsider the spinfoam dynamics that has been recently introduced, in the generalized Kamiński-Kisielowski-Lewandowski (KKL) version where the foam is not dual to a triangulation. We study the Euclidean as well as the Lorentzian case. We show that this theory can still be obtained as a constrained BF theory satisfying the simplicity constraint, now discretized on a general oriented 2-cell complex. This constraint implies that boundary states admit a (quantum) geometrical interpretation in terms of polyhedra, generalizing the tetrahedral geometry of the simplicial case. We also point out that the general solution to this constraint (imposed weakly) depends on a quantum number $r_f$ in addition to those of loop quantum gravity. We compute the vertex amplitude and recover the KKL amplitude in the Euclidean theory when $r_f=0$. We comment on the eventual physical relevance of $r_f$, and the formal way to eliminate it.

We investigate the strong gravitational lensing in a squashed Kaluza-Klein black hole immersed in the Gödel universe with global rotation. Our results show that the strong gravitational lensing in the squashed Kaluza-Klein Gödel black hole spacetime has some distinct behaviors from that in the Kerr case. In the squashed Kaluza-Klein Gödel black hole spacetime, the photon sphere radius, the minimum impact parameter, the coefficient $\overline{a}$, $\overline{b}$, and the deflection angle $\alpha (\theta )$ in the $\varphi$ direction are independent of whether the photon goes with or against the global rotation of the Gödel Universe. While in the Kerr black hole, the values of these quantities for the prograde photons are different from those for the retrograde photons. Moreover, the coefficient of $\overline{b}$ increases with $j$ in the squashed Kaluza-Klein Gödel black hole, but decreases with $a$ in the Kerr case. We also probe the influence of the squashed effect on the strong gravitational lensing in this black hole and find that in the extremely squashed case ${\rho }_0=0$, the coefficient $\overline{a}$ is a constant 1 and is independent of the global rotation of the Gödel Universe. Furthermore, we assume that the gravitational field of the supermassive central object of the Galaxy can be described by this metric and estimate the numerical values of the coefficients and the main observables in the strong gravitational lensing.

We present forecast results for constraining the primordial non-Gaussianity from photometric surveys through a large-scale enhancement of the galaxy clustering amplitude. In photometric surveys, the distribution of observed galaxies at high redshifts suffers from the gravitational-lensing magnification, which systematically alters the number density for magnitude-limited galaxy samples. We estimate size of the systematic bias in the best-fit cosmological parameters caused by the magnification effect, particularly focusing on the primordial non-Gaussianity. For upcoming deep and/or wide photometric surveys like the Hyper Suprime-Cam, the Dark Energy Survey and the Large Synaptic Survey Telescope, the best-fit value of the non-Gaussian parameter, $f_{\mathrm{NL}}$, obtained from the galaxy count data is highly biased, and the true values of $f_{\mathrm{NL}}$ would typically go outside the $3\mathrm{\text{−}}\sigma$ error of the biased confidence region, if we ignore the magnification effect in the theoretical template of angular power spectrum. The additional information from cosmic shear data helps not only to improve the constraint, but also to reduce the systematic bias. As a result, the size of systematic bias on $f_{\mathrm{NL}}$ would become small enough compared to the expected $1\mathrm{\text{−}}\sigma$ error for the Hyper Suprime-Cam and the Dark Energy Survey, but it would still be serious for deep surveys with $z_{\mathrm{m}}\gtrsim 1.5$, like the Large Synaptic Survey Telescope. Tomographic technique improves the constraint on $f_{\mathrm{NL}}$ by a factor of 2–3 compared to the one without tomography, but the systematic bias would increase.

The extragalactic background light (EBL) observed at multiple wavelengths is a promising tool to probe the nature of dark matter. This radiation might contain a significant contribution from gamma-rays produced promptly by dark matter particle annihilation in the many halos and subhalos within our past-light cone. Additionally, the electrons and positrons produced in the annihilation give energy to the cosmic microwave photons to populate the EBL with X-rays and gamma-rays. To study these signals, we create full-sky maps of the expected radiation from both of these contributions using the high-resolution Millennium-II simulation of cosmic structure formation. Our method also accounts for a possible enhancement of the annihilation rate by a Sommerfeld mechanism due to a Yukawa interaction between the dark matter particles prior to annihilation. We use upper limits on the contributions of unknown sources to the EBL to constrain the intrinsic properties of dark matter using a model-independent approach that can be employed as a template to test different particle physics models. These upper limits are based on observational measurements spanning 8 orders of magnitude in energy (from soft X-rays measured by the CHANDRA satellite to gamma-rays measured by the Fermi satellite), and on expectations for the contributions from nonblazar active galactic nuclei, blazars and star-forming galaxies. To exemplify this approach, we analyze a set of benchmark Sommerfeld-enhanced models that give the correct abundance of dark matter, satisfy constraints from the cosmic microwave background, and fit the cosmic ray spectra measured by PAMELA and Fermi without any contribution from local substructure. We find that these models are in conflict with the EBL constraints unless the contribution of unresolved substructure is small and the dark matter annihilation signal dominates the EBL. We conclude that provided the collisionless cold dark matter paradigm is accurate, even for conservative estimates of the contribution from unresolved substructure and astrophysical backgrounds, the EBL is at least as sensitive a probe of these types of scenarios as the cosmic microwave background. More generally, our results disfavor an explanation of the positron excess measured by the PAMELA satellite based only on dark matter annihilation in the smooth Galactic dark matter halo.

We estimate the amount of vorticity generated at second order in cosmological perturbation theory from the coupling between first order energy density and nonadiabatic pressure, or entropy, perturbations. Assuming power law input spectra for the source terms, and working in a radiation background, we calculate the wave number dependence of the vorticity power spectrum and its amplitude. We show that the vorticity generated by this mechanism is non-negligible on small scales, and hence should be taken into consideration in current and future cosmic microwave background experiments.

Coalescing binaries are credited as being relatively abundant sources of gravitational radiation, with a rich content of physical information. Their signals, apart from (important) complications due to higher-order post-Newtonian corrections, spin-orbit and spin-spin couplings, etc., are so-called chirp signals, i.e. a signal modulated both in amplitude and in frequency. The rate at which the frequency changes depends basically on the chirp mass, a particular combination of the masses of the two objets. It is known that the Wigner-Ville transform is an optimal time-frequency distribution in detecting chirping signals whose instantaneous frequency grows linearly in time. We compare the performance of the plain Wigner-Ville transform and of blind source separation-augmented Wigner-Ville transform. We consider a typical chirp of interest for ground-based gravitational wave (GW) detectors and inject it at a $\mathrm{SNR}=12$ into two independent time series of white Gaussian noise. We show that the blind source separation preprocessing acts as a powerful denoising tool, yielding a significant enhancement in the detection capability of the Wigner-Ville transform alone. We report preliminary results, focused on detection performances, which appear to be very promising; the improvement in parameters estimation will be discussed in a forthcoming paper. The possibility to apply our analysis to a network of GW interferometers is briefly discussed. Finally, we stress the fact the our methods are completely independent on the shape of the signal, and thus have broader applications besides chirp gravitational wave signals.

With much higher sensitivities due to coherence effects, it is often assumed that the first evidence for direct dark matter detection will come from experiments probing spin-independent interactions. We explore models that would be invisible in such experiments, but detectable via spin-dependent interactions. The existence of much larger (or even only) spin-dependent tree-level interactions is not sufficient, due to potential spin-independent subdominant or loop-induced interactions. We find that, in such a way, most models with detectable spin-dependent interactions would also generate detectable spin-independent interactions. Models in which a light pseudoscalar acts as the mediator seem to uniquely evade this conclusion. We present a particular viable dark matter model generating such an interaction.

We study the potential to use measurements of the properties of extra neutral gauge bosons ($Z^{\prime }$’s) in $pp$ collisions at the Large Hadron Collider to unravel the underlying physics. We focus on the usefulness of third generation final states ($\tau$, $b$, $t$) in distinguishing between models with nonuniversal $Z^{\prime }$-fermion couplings. We present an update of discovery limits of $Z^{\prime }$’s including the 2010–2011 LHC run and include models with nonuniversal couplings. We show how ratios of $\sigma (pp\to Z^{\prime }\to t\overline{t})$, $\sigma (pp\to Z^{\prime }\to b\overline{b})$, and $\sigma (pp\to Z^{\prime }\to {\tau }^{+}{\tau }^{-})$ to $\sigma (pp\to Z^{\prime }\to {\mu }^{+}{\mu }^{-})$ can be used to distinguish between models and measure parameters of the models. Of specific interest are models with preferential couplings such as models with generation dependent couplings. We also find that forward-backward asymmetry measurements with third generation fermions in the final state could provide important input to understanding the nature of the $Z^{\prime }$. Understanding detector resolution and efficiencies will be crucial for extracting results.

We study the single transverse-spin asymmetry for inclusive light-hadron productions in the proton-proton collision, $p^{\uparrow }p\to hX$ ($h=\pi$, $K$, $\eta$), for the RHIC kinematics based on the twist-3 mechanism in the collinear factorization. The analysis includes all the contributions from the soft-gluon pole and the soft-fermion pole for the twist-3 quark-gluon correlation functions in the transversely polarized proton. After discussing the flavor decomposition and the $P_T$-dependence of the asymmetry obtained in the previous analysis at the center-of-mass energy $\sqrt{S}=62.4$ and 200 GeV, we will give a prediction for the asymmetry at $\sqrt{S}=500\mathrm{GeV}$ and also for the $\eta$-meson production. We found slightly smaller asymmetry at $\sqrt{S}=500\mathrm{GeV}$ for ${\pi }^{\pm ,0}$ and $K^{+}$ compared with those at the lower energies. The asymmetry for the $\eta$-meson turned out to be significantly larger than that for ${\pi }^0$.

We present a study of the Drell-Yan process in pion-proton collisions including next-to-leading-logarithmic threshold-resummed contributions. We analyze rapidity-integrated as well as rapidity-differential cross sections in the kinematic regime relevant for the COMPASS fixed target experiment. We find that resummation leads to a significant enhancement of the cross section compared to fixed-order calculations in this regime. Particularly large corrections arise at large forward and backward rapidities of the lepton pair. We also study the scale dependence of the cross section and find it to be substantially reduced by threshold resummation.

We compute the diagonal isovector axial-vector as well as induced pseudoscalar form factors of nucleon, $\Sigma$, and $\Xi$ baryons by employing the light-cone QCD sum rules to leading order in QCD and including distribution amplitudes up to twist 6. Extrapolating our sum-rules results to low-momentum transfers, we make a comparison with experimental and lattice-QCD results where we can achieve a nice qualitative and quantitative agreement.

The next-to-leading order QCD corrections to ${\rm Y}$ production via $S$-wave color-octet states ${\rm Y}[{}^{1}S_0^{(8)},{}^{3}S_1^{(8)}]$ at the Tevatron and LHC is calculated. The K factors of total cross section (ratio of next-to-leading order to leading order) are 1.313 and 1.379 for ${\rm Y}[{}^{1}S_0^{(8)}]$ and ${\rm Y}[{}^{3}S_1^{(8)}]$ at the Tevatron, while at the LHC they are 1.044 and 1.182, respectively. By fitting the experimental data from the CDF and D0, the matrix elements for $S$-wave color-octet states are obtained. And new predictions for ${\rm Y}(1S)$ production are presented. The prediction for the polarization of inclusive ${\rm Y}$ contains large uncertainty rising from the polarization of ${\rm Y}(1S)$ from feed-down of ${\chi }_b$. The production of ${\rm Y}(3S)$ at the hadron colliders is also studied to avoid the large uncertainty mentioned above. To further clarify the situation, new measurements on the production and polarization for direct ${\rm Y}(1S)$ and ${\rm Y}(3S)$ are expected.

We present an $N=1$ supersymmetric multiplet with a vector-spinor field in three dimensions. We call this the vector-spinor multiplet with the field content $({\psi }_{\mu },A_{\mu },\lambda )$, where ${\psi }_{\mu }$ is a vector spinor, $A_{\mu }$ is a vector, while $\lambda$ is a gaugino. Based on on-shell component field formulation, we can accommodate $N=1$ supersymmetric Dirac-Born-Infeld (SDBI) interactions consistently with supersymmetry. This is possible even in the presence of the vector spinor. The ${\psi }_{\mu }$-field equation contains a nontrivial interaction term with $A_{\mu }$. Moreover, it turns out that in the presence of mass terms, one physical degree of freedom in the original $\lambda$ is transferred to that of ${\psi }_{\mu }$, making the latter propagating. In other words, our model presents nontrivial rewriting of SDBI interaction in terms of $({\psi }_{\mu },A_{\mu })$ instead of $(A_{\mu },\lambda )$.

We discuss corrections to the ratio of shear viscosity to entropy density $\eta /s$ in higher-derivative gravity theories. Generically, these theories contain ghost modes with Planck-scale masses. Motivated by general considerations about unitarity, we propose new boundary conditions for the equations of motion of the graviton perturbations that force the amplitude of the ghosts modes to vanish. We analyze explicitly four-derivative perturbative corrections to Einstein gravity which generically lead to four-derivative equations of motion, compare our choice of boundary conditions to previous proposals and show that, with our new prescription, the ratio $\eta /s$ remains at the Einstein-gravity value of $1/4\pi$ to leading order in the corrections. It is argued that, when the new boundary conditions are imposed on six and higher-derivative equations of motion, $\eta /s$ can only increase from the Einstein-gravity value. We also recall some general arguments that support the validity of our results to all orders in the strength of the corrections to Einstein gravity. We then discuss the particular case of Gauss-Bonnet gravity, for which the equations of motion are only of two-derivative order and the value of $\eta /s$ can decrease below $1/4\pi$ when treated in a nonperturbative way. Our findings provide further evidence for the validity of the KSS bound for theories that can be viewed as perturbative corrections to Einstein gravity.