Global analysis has been performed within the next-to-leading order in quantum chromodynamics (QCD) to determine polarized parton distributions with new experimental data in spin asymmetries. The new data set includes J-Lab, HERMES, and COMPASS measurements on spin asymmetry $A_1$ for the neutron and deuteron in lepton scattering. Our new analysis also utilizes the double-spin asymmetry for ${\pi }^0$ production in polarized $pp$ collisions, $A_{LL}^{{\pi }^0}$, measured by the PHENIX Collaboration. Because of these new data, uncertainties of the polarized PDFs are reduced. In particular, the J-Lab, HERMES, and COMPASS measurements are valuable for determining $\Delta d_v(x)$ at large $x$ and $\Delta \overline{q}(x)$ at $x\sim 0.1$. The PHENIX ${\pi }^0$ data significantly reduce the uncertainty of $\Delta g(x)$. Furthermore, we discuss a possible constraint on $\Delta g(x)$ at large $x$ by using the HERMES data on $g_1^d$ in comparison with the COMPASS ones at $x\sim 0.05$.

Using a sample of $3.08\times {10}^6$ $\psi (2S)$ decays collected at $\sqrt{s}=3.686\mathrm{GeV}$ with the CLEO detector at the Cornell Electron Storage Ring, we have measured the branching fractions for $\psi (2S)$ decays to pseudoscalar pairs ${\pi }^{+}{\pi }^{-}$, $K^{+}{K}^{-}$ and $K_S^0{K}_L^0$. We obtain $\mathcal{B}(\psi (2S)\to {\pi }^{+}{\pi }^{-})<2.1\times {10}^{-5}$ (90% C.L.), $\mathcal{B}(\psi (2S)\to K^{+}{K}^{-})=(6.3\pm 0.6(\mathrm{stat})\pm 0.3(\mathrm{syst}))\times {10}^{-5}$, and $\mathcal{B}(\psi (2S)\to K_S^0{K}_L^0)=(5.8\pm 0.8(\mathrm{stat})\pm 0.4(\mathrm{syst}))\times {10}^{-5}$. The branching fractions allow extraction of the relative phase $\Delta =(95\pm 15)°$ and strength ratio $R=(2.5\pm 0.4)$ of the three-gluon and one-photon amplitudes for these modes.

An apparent contradiction in the leading order correction to noncommutative (NC) gravity reported in the literature has been pointed out. We show by direct computation that actually there is no such controversy and all perturbative NC corrections start from the second order in the NC parameter. The role of symmetries in the vanishing of the first order correction is manifest in our calculation.

It has been proposed recently that, within the framework of split supersymmetry, long lived gluinos generated in astrophysical sources could be detected using the signatures of the air showers they produce, thus providing a lower bound for their lifetime and for the scale of supersymmetry breaking. We present the longitudinal profile and lateral spread of $G$-hadron induced extensive air showers and consider the possibility of measuring them with a detector with the characteristics of the Pierre Auger Observatory.

We start this work by revisiting the problem of the soldering of two chiral Schwinger models of opposite chiralities. We verify that, different from what one can conclude from the current literature, the usual sum of these models is, in fact, gauge invariant and corresponds to a composite model, where the component models are the vector and axial Schwinger models. As a consequence, we reinterpret this formalism as a kind of degree of freedom reduction mechanism. This result has led us to discover a second soldering possibility giving rise to the axial Schwinger model. This new result is seemingly rather general. We explore it here in the soldering of two Maxwell-Chern-Simons theories with different masses.

Even though the energy carried by a gravitational wave is not itself gauge invariant, the interaction with a gravitational antenna of the gravitational wave which carries that energy is. It therefore has to be possible to make some statements involving the energy which are in fact gauge invariant, and it is the objective of this paper to provide them. In order to develop a gauge invariant treatment of the issues involved, we construct a specific action for gravitational fluctuations which is gauge invariant to second perturbative order. Then, via variation of this action, we obtain an energy-momentum tensor for perturbative gravitational fluctuations around a general curved background whose covariant conservation condition is also fully gauge invariant to second order. Contraction of this energy-momentum tensor with a Killing vector of the background conveniently allows us to convert this covariant conservation condition into an ordinary conservation condition which is also gauge invariant through second order. Then, via spatial integration we are able to obtain a relation involving the time derivative of the total energy of the fluctuation and its asymptotic spatial momentum flux which is also completely gauge invariant through second order. It is only in making the simplification of setting the asymptotic momentum flux to zero that one would actually lose manifest gauge invariance, with only invariance under those particular gauge transformations which leave the asymptotic momentum flux zero then remaining. However, if one works in an arbitrary gauge where the asymptotic momentum flux is nonzero, the gravitational wave will then deliver both energy and momentum to a gravitational antenna in a completely gauge invariant manner, no matter how badly behaved at infinity the gauge function might be.

Weak lensing distortion of the background cosmic microwave background (CMB) temperature and polarization patterns by the foreground density fluctuations is well studied in the literature. We discuss the gravitational lensing modification to CMB anisotropies and polarization by a stochastic background of primordial gravitational waves between us and the last scattering surface. While density fluctuations perturb CMB photons via gradient-type deflections only, foreground gravitational waves distort CMB anisotropies via both gradient- and curl-type displacements. The latter is a rotation of background images, while the former is related to the lensing convergence. For a primordial background of inflationary gravitational waves, with an amplitude corresponding to a tensor-to-scalar ratio below the current upper limit of $\sim 0.3$, the resulting modifications to the angular power spectra of CMB temperature anisotropy and polarization are below the cosmic variance limit. At tens of arcminute angular scales and below, these corrections, however, are above the level at which systematics must be controlled in all-sky anisotropy and polarization maps with no instrumental noise and other secondary and foreground signals.

Cosmological issues of the gravitino production by the decay of a heavy scalar field $X$ are examined, assuming that the damped coherent oscillation of the scalar once dominated the energy of the universe. The coupling of the scalar field to a gravitino pair is estimated both in spontaneous and explicit supersymmetry breaking scenarios, with the result that it is proportional to the vacuum expectation value of the scalar field in general. Cosmological constraints depend on whether the gravitino is stable or not, and we study each case separately. For the unstable gravitino with $M_{3/2}\sim 100\mathrm{GeV}–10\mathrm{TeV}$, we obtain not only the upper bound, but also the lower bound on the reheating temperature after the $X$ decay, in order to retain the success of the big-bang nucleosynthesis. It is also shown that it severely constrains the decay rate into the gravitino pair. For the stable gravitino, similar but less stringent bounds are obtained to escape the overclosure by the gravitinos produced at the $X$ decay. The requirement that the free-streaming effect of such gravitinos should not suppress the cosmic structures at small scales eliminates some regions in the parameter space, but still opens a new window for the gravitino warm dark matter. Implications of these results to inflation models are discussed. In particular, it is shown that modular inflation will face serious cosmological difficulty when the gravitino is unstable, whereas it can escape the constraints for the stable gravitino. A similar argument offers a solution to the cosmological moduli problem, in which the moduli is relatively heavy while the gravitino is light.

Faced by recent evidence for a flat universe dominated by dark energy, cosmologists grapple with deep cosmic enigmas such as the cosmological constant problem, extreme fine-tuning and the cosmic coincidence problem. The extent to which we observe the dimming of distant supernovae suggests that the cosmic acceleration is as least as severe as in cosmological constant models. Extrapolating this to our cosmic future implies terrifying visions of either a cold and empty universe or an explosive demise in a “Big Rip.” We construct a class of dynamical scalar field models of dark energy and dark matter. Within this class we can explain why supernovae imply a cosmic equation of state $w\lesssim -1$, address fine-tuning issues, protect the universe from premature acceleration and predict a constant fraction of dark energy to dark matter in the future (thus solving the coincidence problem), satisfy the dominant energy condition, and ensure that gravitationally bound objects remain so forever (avoid a Big Rip). This is achieved with a string theory inspired Lagrangian containing standard kinetic terms, exponential potentials and couplings, and parameters of order unity.

We study the oblique corrections to the electroweak interaction in the holographic model of technicolor theories. The oblique $S$ parameter is expressed in terms of a solution to the equations of motion for the anti de Sitter bulk gauge fields. By analyzing the solution, we establish a rigorous proof that the $S$ parameter is positive and is reduced by walking. We also present the precise numerical values for the $S$ parameter of various technicolor models by solving the equations numerically.

If one takes naturalness seriously and also assumes a weakly coupled extension of the standard model (SM) then there are expectations for phenomenology that can be inferred in a model-independent framework. The first such expectation is that there is likely to be some colored particle with mass $\mathcal{O}(\mathrm{TeV})$ that cancels the top loop contribution to the quadratic divergence of the Higgs mass. In this paper we begin a model-independent analysis of the phenomenology of this “top partner,” $t^{\prime }$. We make one additional assumption that it is odd under a parity which is responsible for the stability of a WIMP dark matter candidate, $N$. We focus on three questions to be explored at the LHC: discovery opportunities, mass determination, and spin determination of this top partner. We find that within a certain region of masses for the $t^{\prime }$ and $N$, $t^{\prime }{\overline{t}}^{\prime }$ is easily discovered in the $t\overline{t}+2N$ decay with the tops decaying fully hadronically. We show that without having to rely on other channels for new physics that for a given $t^{\prime }$ spin the masses of $t^{\prime }$ and $N$ can be measured using kinematic information (e.g. average ${\mathrm{E̸}}_{\mathrm{T}}$ or $H_T$) and total cross section. A degeneracy due to the spin remains, but with several hundred ${\mathrm{fb}}^{-1}$ of luminosity we demonstrate potentially useful new methods for determining the $t^{\prime }$ spin over a wide range of masses. Our methods when could be useful for distinguishing supersymmetric and nonsupersymmetric models.

We present two methods for computing dimensionally regulated nonrelativistic QCD heavy-quarkonium matrix elements that are related to the second derivative of the heavy-quarkonium wave function at the origin. The first method makes use of a hard-cutoff regulator as an intermediate step and requires knowledge only of the heavy-quarkonium wave function. It involves a significant cancellation that is an obstacle to achieving high numerical accuracy. The second method is more direct and yields a result that is identical to the Gremm-Kapustin relation, but it is limited to use in potential models. It can be generalized to the computation of matrix elements of higher order in the heavy-quark velocity and can be used to resum the contributions to decay and production rates that are associated with those matrix elements. We apply these methods to the Cornell potential model and compute a matrix element for the $J/\psi$ state that appears in the leading relativistic correction to the production and decay of that state through the color-singlet quark-antiquark channel.

The neutrino mixing matrix appears to be close to bimaximal mixing, but for the solar mixing angle which is definitively smaller than 45 degrees. Whereas it seems quite easy to understand bimaximal mixing with the use of new global symmetries, as in models using $L_e-L_{\mu }-L_{\tau }$, understanding the about to 11 degrees of deviation in the observed solar angle seems less simple. We suggest that such a deviation could be due to a light sterile neutrino that mixes with the active sector. The mass scale needed to produce the effect has to be smaller than atmospheric scale, and it would introduce a new mass squared difference which should be smaller than the solar scale. We present a toy model that exemplifies these features.

We prove that the Moyal product is covariant under linear affine spacetime transformations. From the covariance law, by introducing an $(x,\Theta )$-space where the spacetime coordinates and the noncommutativity matrix components are on the same footing, we obtain a noncommutative representation of the affine algebra, its generators being differential operators in $(x,\Theta )$-space. As a particular case, the Weyl Lie algebra is studied and known results for Weyl invariant noncommutative field theories are rederived in a nutshell. We also show that this covariance cannot be extended to spacetime transformations generated by differential operators whose coefficients are polynomials of order larger than 1. We compare our approach with the twist-deformed enveloping algebra description of spacetime transformations.

We study the semiclassical fluctuation problem around bounce solutions for a self-interacting scalar field in curved space. As in flat space, the fluctuation problem separates into partial waves labeled by an integer $l$, and we determine the large $l$ behavior of the fluctuation determinants, a quantity needed to define a finite fluctuation prefactor. We also show that while the Coleman-De Luccia bounce solution has a single negative mode in the $l=0$ sector, the oscillating bounce solutions also have negative modes in partial waves higher than the $s$-wave, further evidence that they are not directly related to quantum tunneling.

We provide a quantum field theoretical derivation of the Abraham-Lorentz-Dirac (ALD) equation, describing the motion of an electric point charge sourcing an electromagnetic field, which backreacts on the charge as a self-force, and the Mino-Sasaki-Tanaka-Quinn-Wald (MSTQW) equation describing the motion of a point mass with self-force interacting with the linearized metric perturbations caused by the mass off an otherwise vacuous curved background spacetime. We regularize the formally divergent self-force by smearing the direct part of the retarded Green’s function and using a quasilocal expansion. We also derive the ALD-Langevin and the MSTQW-Langevin equations with a classical stochastic force accounting for the effect of the quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. These equations will be useful for studying the stochastic motion of charges and small masses under the influence of both quantum and classical noise sources, derived either self-consistently or put in by hand phenomenologically. We also show that history-dependent noise-induced drift motions could arise from such stochastic sources on the trajectory that could be a hidden feature of gravitational wave forms hitherto unknown.

The detection of nonbaryonic dark matter through its gamma-ray annihilation in the center of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the international space station. Under the assumption that the dark matter is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of minimal supergravity models, show that with a cuspy dark matter halo profile or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the anomaly mediated supersymmetry breaking (AMSB) model. The latter leads also to a cosmologically important ${}^2\mathrm{Li}$ abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.

We review some decays that require knowledge of the decay constants of $0^{+}$ heavy-light mesons. We compute the decay constants of $P$-wave heavy-light mesons from unquenched lattice QCD, with two degenerate flavours of sea quarks, at a single lattice spacing. The lightest sea quark mass used in the calculation is a third of the strange quark mass. For the charm-strange meson we obtain the decay constant: $f_{D_{s{0}^{+}}}=340(110)\mathrm{MeV}$ using our normalization conventions. We obtain the $f_{P_s}^{\mathrm{static}}$ (static-strange $P$-wave) decay constant as $302(39)\mathrm{MeV}$.

Using $14\times {10}^6$ $\psi (2S)$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the branching fractions of $\psi (2S)$ decays to $p\overline{n}{\pi }^{-}$ and $\overline{p}n{\pi }^{+}$ and the branching fractions of the main background channels $\psi (2S)\to p\overline{n}{\pi }^{-}{\pi }^0$, $\psi (2S)\to \gamma {\chi }_{c0}\to \gamma p\overline{n}{\pi }^{-}$, $\psi (2S)\to \gamma {\chi }_{c2}\to \gamma p\overline{n}{\pi }^{-}$, and $\psi (2S)\to \gamma {\chi }_{cJ}\to \gamma p\overline{n}{\pi }^{-}{\pi }^0$ are determined. The contributions of the $N^{*}$ resonances in $\psi (2S)\to p\overline{n}{\pi }^{-}+c.c.$ are also discussed.

We point out that the universality of free-fall can be tested by observing surface-gravity changes of the Earth. The Earth’s inner core is weakly coupled to the rest part of the Earth by mainly gravitational forces. If there were a violation of the universality of free-fall, because of their different chemical compositions and/or of different mass fractions of binding energies, the inner core and the rest part of the Earth would fall at different rates towards the Sun and other sources of gravitational fields. The differential acceleration could be observed as surface-gravity effects. By assuming a simple Earth model, we discuss the expected surface-gravity effects of violations of the universality and experiments to search for such effects by using superconducting gravimeters. It is shown that the universality can be tested to a level of ${10}^{-9}$ using currently operating superconducting gravimeters. Some improvements can be expected from combinations of global measurements and applications of advanced data analyses.