We show that the difference cross sections in unpolarized semi-inclusive deep inelastic scattering $e+N\to e+h+X$ and $pp$ hadron production $p+p\to h+X$ determine independently in a model independent way, in any order in QCD, the two fragmentation functions (FFs): $D_u^{h-\overline{h}}$ and $D_d^{h-\overline{h}}$, $h={\pi }^{\pm }$, $K^{\pm }$ or a sum over charged hadrons. If both $K^{\pm }$ and $K_s^0$ are measured, then $e^{+}{e}^{-}\to K+X$, $e+N\to e+K+X$, and $p+p\to K+X$ present independent measurements of just one FF: $D_{u-d}^{K^{+}+K^{-}}$. The above results allow one to test the existing parametrizations, obtained with various different assumptions about the FFs, and to test the $Q^2$ evolution and factorization.

Chiral symmetry restoration at nonzero temperature and quark densities are investigated in the framework of a linear sigma model with $N_f=3$ light quark flavors. After the derivation of the grand potential in mean-field approximation, the nonstrange and strange condensates, the in-medium masses of the scalar and pseudoscalar nonets are analyzed in hot and dense medium. The influence of the axial anomaly on the nonet masses and the isoscalar mixings on the pseudoscalar $\eta \mathrm{\text{−}}{\eta }^{\prime }$ and scalar $\sigma (600)\mathrm{\text{−}}{f}_0(1370)$ complex are examined. The sensitivity of the chiral phase transition as well as the existence and location of a critical end point in the phase diagram on the value of the sigma mass are explored. The chiral critical surface with and without the influence of the axial $U(1{)}_A$ anomaly is elaborated as a function of the pion and kaon masses for several values of the sigma mass.

Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above $\sim 10\mathrm{GeV}$ PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with the data. The positron excess may be evidence of dark matter annihilation or decay. We compare the positron and antiproton spectra with the data by assuming that dark matter annihilates or decays into different final states. The PAMELA data actually excludes quark pairs being the main final states, and disfavors gauge boson final states. Only in the case of leptonic final states can the positron and antiproton spectra be explained simultaneously. We also compare the decaying and annihilating dark matter scenarios which can account for the PAMELA results and find that the decaying dark matter is preferred. Finally, we consider a decaying neutralino dark matter model in the frame of supersymmetry with R-parity violation. The PAMELA data is well fitted with a neutralino mass of $600\sim 2000\mathrm{GeV}$ and a lifetime of $\sim {10}^{26}$ seconds. We also demonstrate that a neutralino with mass around 2 TeV can fit PAMELA and ATIC data simultaneously.

A step feature in the inflaton potential can model a transient breakdown of slow-roll inflation. Here we generalize the step feature to include space-dependence, allowing it also to model a breakdown of homogeneity and isotropy. The space-dependent inflaton potential generates a classical curvature perturbation mode characterized by the wave number of the step inhomogeneity. For inhomogeneities small compared with the horizon at the step, space-dependence has a small effect on the curvature perturbation. Therefore, the smoothly oscillating quantum power spectrum predicted by the homogeneous step is robust with respect to subhorizon space-dependence. For inhomogeneities equal to or greater than the horizon at the step, the space-dependent classical mode can dominate, producing a curvature perturbation in which modes of wave number determined by the step inhomogeneity are superimposed on the oscillating power spectrum. Generation of a space-dependent step feature may therefore provide a mechanism to introduce primordial anisotropy into the curvature perturbation. Space-dependence also modifies the quantum fluctuations, in particular, via resonancelike features coming from mode coupling to amplified superhorizon modes. However, these effects are small relative to the classical modes.

A search for periodic gravitational waves, from sources such as isolated rapidly spinning neutron stars, was carried out using 510 h of data from the fourth LIGO science run (S4). The search was for quasimonochromatic waves in the frequency range from 50 to 1500 Hz, with a linear frequency drift $\dot{f}$ (measured at the solar system barycenter) in the range $-f/\tau <\dot{f}<0.1f/\tau$, where the minimum spin-down age $\tau$ was 1000 yr for signals below 300 Hz and 10 000 yr above 300 Hz. The main computational work of the search was distributed over approximately 100 000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 h, despite the large parameter space searched. No statistically significant signals were found. The sensitivity of the search is estimated, along with the fraction of parameter space that was vetoed because of contamination by instrumental artifacts. In the 100 to 200 Hz band, more than 90% of sources with dimensionless gravitational-wave strain amplitude greater than ${10}^{-23}$ would have been detected.

Based on general considerations rather than model-dependent fits to specific scenarios, we argue that an increase with energy of the positron fraction in cosmic rays, suggested by several experiments at $E\gtrsim 7\mathrm{GeV}$, most likely requires a primary source of electron-positron pairs. We discuss the possible alternatives, and find none of them plausible on astrophysical or particle physics grounds. Further observational ways to test different scenarios are discussed.

Light bosons can be found in large classes of theories beyond the standard model. These light bosons may not be ruled out by current experiments and, indeed, may even provide an explanation for some anomalous experimental results. The radiative decays of quarkonium ($c\overline{c}$, $b\overline{b}$) states offer a promising opportunity to investigate such light bosons. Specifically, we investigate the reach that current CLEO data can have on models with light scalar and pseudoscalar bosons.

We study the current structure of the lepton flavor violating $\tau \to 3\mu$ decay in the Type-III 2HDM. This model has many coupling constants that affect this decay. We find that each coupling constant corresponds to a different final-state momentum distribution and vice versa. Using this fact, we suggest how to determine the current structure. We also find the upper limit $|{\eta }_{23}^E{\eta }_{22}^E|<0.00022$ in the case that all Higgs bosons except for the lighter $CP$ even neutral $h^0$ are decoupled, $M_{h^0}=115\mathrm{GeV}$ and $\cos \beta =1/\sqrt{2}$. The observable difference between the MSSM and Type-III 2HDM is also discussed.

We calculate the differential cross section for real-photon electroproduction off a spinless hadron which serves as a main probe of the hadrons structure via the concept of generalized parton distributions. Compared to previously available computations performed with twist-three power accuracy, we exactly accounted for all kinematical effects in hadron mass and momentum transfer which arise from leptonic helicity amplitudes. We performed numerical studies of these kinematical effects and demonstrated that in the valence quark region and rather low virtualities of the hard photon which sets the factorization scale, the available approximate results significantly overestimate the cross section rates in comparison to exact formulas.

The properties of pseudoscalar bosonic excitations in the color-flavor locked phase at moderate densities are studied within a model of the Nambu–Jona-Lasinio type. Our previous analysis [V. Kleinhaus, M. Buballa, D. Nickel, and M. Oertel, Phys. Rev. D 76, 074024 (2007).] is extended to Goldstone bosons with hidden flavor and to higher-lying modes which stay massive in the chiral limit. The bosons are constructed explicitly by solving the Bethe-Salpeter equation for quark-quark scattering in random phase approximation. The masses and weak decay constants of the Goldstone bosons are found in good agreement with predictions from the low-energy effective theory. In the non-Goldstone sector we find an $SU(3)$ octet which is weakly bound, while the singlet appears to be unbound.

The radiative decay of the axial-vector resonances into a pseudoscalar meson and a photon is studied using the vector meson Lagrangian obtained from the hidden gauge symmetry (HGS) formalism. The formalism is well suited to study this problem since it deals with pseudoscalar and vector mesons in a unified way, respecting chiral invariance. We show explicitly the gauge invariance of the set of diagrams that appear in the approach and evaluate the radiative decay width of the $a_1(1260)$ and $b_1(1235)$ axial-vector meson resonances into $\pi \gamma$. We also include the contribution of loops involving anomalous couplings and compare the results to those obtained previously within another formalism.

The strong decays of the ${\pi }_2(1880)$ as the $2{}^{1}D_2$ quark-antiquark state are investigated in the ${}^{3}P_0$ model and the flux-tube model, respectively. The results are similar in the two models. It is found that the decay patterns of the conventional $2{}^{1}D_2$ meson and the $2^{-+}$ light hybrid are very different, and the experimental evidence for the ${\pi }_2(1880)$ is consistent with it being the conventional $2{}^{1}D_2$ meson rather than the $2^{-+}$ light hybrid. The possibility of the ${\pi }_2(1880)$ being a mixture of the conventional $q\overline{q}$ and the hybrid is discussed.

Under two different scenarios for the light scalar mesons, we investigate the transition form factors of $B(B_s)$ mesons decay into a scalar meson in the perturbative QCD approach. In the large recoiling region, the form factors are dominated by the short-distance dynamics and can be calculated using perturbation theory. We adopt the dipole parametrization to recast the $q^2$ dependence of the form factors. Since the decay constants defined by the scalar current are large, our predictions on the $B\to S$ form factors are much larger than the $B\to P$ transitions, especially in the second scenario. Contributions from various light-cone distribution amplitudes (LCDAs) are elaborated and we find that the twist-3 LCDAs provide more than one-half of the contributions to the form factors. The two terms of the twist-2 LCDAs give destructive contributions in the first scenario while they give constructive contributions in the second scenario. With the form factors, we also predict the decay width and branching ratios of the semileptonic $B\to Sl\overline{\nu }$ and $B\to S{l}^{+}{l}^{-}$ decays. The branching ratios of $B\to Sl\overline{\nu }$ channels are found to have the order of ${10}^{-4}$ while those of $B\to S{l}^{+}{l}^{-}$ have the order of ${10}^{-7}$. These predictions can be tested by the future experiments.

We compute the leading chiral-logarithmic corrections to the $S$ parameter in the four-site Higgsless model. In addition to the usual electroweak gauge bosons of the standard model, this model contains two sets of heavy charged and neutral gauge bosons. In the continuum limit, the latter gauge bosons can be identified with the first excited Kaluza-Klein states of the $W^{\pm }$ and $Z$ bosons of a warped extra-dimensional model with an $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_X$ bulk gauge symmetry. We consider delocalized fermions and show that the delocalization parameter must be considerably tuned from its tree-level ideal value in order to reconcile experimental constraints with the one-loop results. Hence, the delocalization of fermions does not solve the problem of large contributions to the $S$ parameter in this class of theories and significant contributions to $S$ can potentially occur at one-loop.

Using samples of $(5.93\pm 0.10)\times {10}^6$ ${\rm Y}(3S)$ decays and $(9.11\pm 0.14)\times {10}^6$ ${\rm Y}(2S)$ decays collected with the CLEO detector, we report improved measurements of the following branching fractions: $\mathcal{B}({\rm Y}(3S)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-})=(4.46\pm 0.01\pm 0.13)\%$, $\mathcal{B}({\rm Y}(2S)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-})=(18.02\pm 0.02\pm 0.61)\%$, $\mathcal{B}({\rm Y}(3S)\to {\rm Y}(1S){\pi }^0{\pi }^0)=(2.24\pm 0.09\pm 0.11)\%$, $\mathcal{B}({\rm Y}(2S)\to {\rm Y}(1S){\pi }^0{\pi }^0)=(8.43\pm 0.16\pm 0.42)\%$, and $\mathcal{B}({\rm Y}(3S)\to {\rm Y}(2S){\pi }^0{\pi }^0)=(1.82\pm 0.09\pm 0.12)\%$. In each case, the first uncertainty reported is statistical, while the second is systematic.

In this paper, the dynamical attractor and heteroclinic orbit have been employed to make the late-time behaviors of the model insensitive to the initial condition and thus alleviate the fine-tuning problem in the torsion cosmology. The late-time de Sitter attractor indicates that torsion cosmology is an elegant scheme and the scalar torsion mode is an interesting geometric quantity for physics. The numerical solutions obtained by Nester et al. are not periodic solutions but are quasiperiodic solutions near the focus for the coupled nonlinear equations.

A numerical approach is considered for spherically symmetric spacetimes that generalize Lemaître–Tolman–Bondi dust solutions to nonzero pressure (“LTB spacetimes”). We introduce quasilocal (QL) variables that are covariant LTB objects satisfying evolution equations of Friedman–Lemaître–Robertson–Walker (FLRW) cosmologies. We prove rigorously that relative deviations of the local covariant scalars from the QL scalars are nonlinear, gauge invariant and covariant perturbations on a FLRW formal background given by the QL scalars. The dynamics of LTB spacetimes is completely determined by the QL scalars and these exact perturbations. Since LTB spacetimes are compatible with a wide variety of “equations of state,” either single fluids or mixtures, a large number of known solutions with dark matter and dark energy sources in a FLRW framework (or with linear perturbations) can be readily examined under idealized but nontrivial inhomogeneous conditions. Coordinate choices and initial conditions are derived for a numerical treatment of the perturbation equations, allowing us to study nonlinear effects in a variety of phenomena, such as gravitational collapse, nonlocal effects, void formation, dark matter and dark energy couplings, and particle creation. In particular, the embedding of inhomogeneous regions can be performed by a smooth matching with a suitable FLRW solution, thus generalizing the Newtonian “top hat” models that are widely used in astrophysical literature. As examples of the application of the formalism, we examine numerically the formation of a black hole in an expanding Chaplygin gas FLRW universe, as well as the evolution of density clumps and voids in an interactive mixture of cold dark matter and dark energy.

We present a proposal for performing model-independent jets plus missing energy searches. Currently, these searches are optimized for mSUGRA and are consequently not sensitive to all kinematically accessible regions of parameter space. We show that the reach of these searches can be broadened by setting limits on the differential cross section as a function of the total visible energy and the missing energy. These measurements only require knowledge of the relevant standard model backgrounds and can be subsequently used to limit any theoretical model of new physics. We apply this approach to an example where gluinos are pair-produced and decay to the LSP through a single-step cascade and show how sensitivity to different gluino masses is altered by the presence of the decay chain. The analysis is closely based upon the current searches done at the Tevatron and our proposal requires only small modifications to the existing techniques. We find that within the minimal supersymmetric standard model, the gluino can be as light as 125 GeV. The same techniques are applicable to jets and missing energy searches at the Large Hadron Collider.

The analytic form of the asymptotic behavior of the $S$ matrix in the saturation regime including the running coupling is obtained. To get this result, we solve the Balitsky and Kovchegov-Weigert evolution equations in the saturation regime, which include running coupling corrections. We study also the effect of rare fluctuations on top of the running coupling. We find that the rare fluctuations are less important in the running coupling case as compared to the fixed coupling case.