We study the reaction $e^{+}{e}^{-}\to e^{+}{e}^{-}{\eta }_c$, ${\eta }_c\to K_S{K}^{\pm }{\pi }^{\mp }$ and obtain ${\eta }_c$ mass and width values $2982.2\pm 0.4\pm 1.6\mathrm{MeV}/c^2$ and $31.7\pm 1.2\pm 0.8\mathrm{MeV}$, respectively. We find $\Gamma ({\eta }_c\to \gamma \gamma )\mathcal{B}({\eta }_c\to K\overline{K}\pi )=0.374\pm 0.009\pm 0.031\mathrm{keV}$, and measure the $\gamma {\gamma }^{*}\to {\eta }_c$ transition form factor in the momentum transfer range from 2 to $50{\mathrm{GeV}}^2$. The analysis is based on $469{\mathrm{fb}}^{-1}$ of integrated luminosity collected at PEP-II with the BABAR detector at $e^{+}{e}^{-}$ center-of-mass energies near 10.6 GeV.

An updated global analysis within the standard model (SM) of all relevant electroweak precision and Higgs boson search data is presented with special emphasis on the implications for the Higgs boson mass, $M_H$. Included are, in particular, the most recent results on the top quark and $W$ boson masses, updated and significantly shifted constraints on the strong coupling constant, ${\alpha }_s$, from $\tau$ decays and other low-energy measurements such as from atomic parity violation and neutrino deep inelastic scattering. The latest results from searches for Higgs production and decay at the Tevatron are incorporated together with the older constraints from LEP 2. I find a trimodal probability distribution for $M_H$ with a fairly narrow preferred 90% C.L. window, $115\mathrm{GeV}\le M_H\le 148\mathrm{GeV}$.

We present a search for the decay $B^{+}\to {\ell }^{+}{\nu }_{\ell }(\ell =\tau ,\mu ,\mathrm{\text{or}}e)$ in $(458.9\pm 5.1)\times {10}^6$ $B\overline{B}$ pairs recorded with the BABAR detector at the PEP-II $B$-factory. We search for these $B$ decays in a sample of $B^{+}{B}^{-}$ events where one $B$-meson is reconstructed as $B^{-}\to D^0{\ell }^{-}\overline{\nu }X$. Using the method of Feldman and Cousins, we obtain $\mathcal{B}(B^{+}\to {\tau }^{+}{\nu }_{\tau })=(1.7\pm 0.8\pm 0.2)\times {10}^{-4}$, which excludes zero at $2.3\sigma$. We interpret the central value in the context of the standard model and find the $B$ meson decay constant to be $f_B^2=(62\pm 31)\times {10}^3{\mathrm{MeV}}^2$. We find no evidence for $B^{+}\to e^{+}{\nu }_e$ and $B^{+}\to {\mu }^{+}{\nu }_{\mu }$ and set upper limits at the 90% C.L. $\mathcal{B}(B^{+}\to e^{+}{\nu }_e)<0.8\times {10}^{-5}$ and $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<1.1\times {10}^{-5}$.

We study a generalized version of Chaplygin gas as unified model of dark matter and dark energy. Using realistic theoretical models and the currently available observational data from the age of the universe, the expansion history based on the type Ia supernovae, the matter power spectrum, the cosmic microwave background radiation anisotropy power spectra, and the perturbation growth factor we put the unified model under observational test. As the model has only two free parameters in the flat Friedmann background [$\Lambda \mathrm{CDM}$ (cold dark matter) model has only one free parameter] we show that the model is already tightly constrained by currently available observations. The only parameter space extremely close to the $\Lambda \mathrm{CDM}$ model is allowed in this unified model.

The clustering of matter on cosmological scales is an essential probe for studying the physical origin and composition of our Universe. To date, most of the direct studies have focused on shear-shear weak lensing correlations, but it is also possible to extract the dark matter clustering by combining galaxy-clustering and galaxy-galaxy-lensing measurements. In order to extract the required information, one must relate the observable galaxy distribution to the underlying dark matter distribution. In this study we develop in detail a method that can constrain the dark matter correlation function from galaxy clustering and galaxy-galaxy-lensing measurements, by focusing on the correlation coefficient between the galaxy and matter overdensity fields. Our goal is to develop an estimator that maximally correlates the two. To generate a mock galaxy catalogue for testing purposes, we use the halo occupation distribution approach applied to a large ensemble of $N$-body simulations to model preexisting SDSS luminous red galaxy sample observations. Using this mock catalogue, we show that a direct comparison between the excess surface mass density measured by lensing and its corresponding galaxy clustering quantity is not optimal. We develop a new statistic that suppresses the small-scale contributions to these observations and show that this new statistic leads to a cross-correlation coefficient that is within a few percent of unity down to $5h^{-1}\mathrm{Mpc}$. Furthermore, the residual incoherence between the galaxy and matter fields can be explained using a theoretical model for scale-dependent galaxy bias, giving us a final estimator that is unbiased to within 1%, so that we can reconstruct the dark matter clustering power spectrum at this accuracy up to $k\sim 1h{\mathrm{Mpc}}^{-1}$. We also perform a comprehensive study of other physical effects that can affect the analysis, such as redshift space distortions and differences in radial windows between galaxy clustering and weak lensing observations. We apply the method to a range of cosmological models and explicitly show the viability of our new statistic to distinguish between cosmological models.

We present data analysis methods used in the detection and estimation of parameters of gravitational-wave signals from the white dwarf binaries in the mock LISA data challenge. Our main focus is on the analysis of challenge 3.1, where the gravitational-wave signals from more than $6\times {10}^7$ Galactic binaries were added to the simulated Gaussian instrumental noise. The majority of the signals at low frequencies are not resolved individually. The confusion between the signals is strongly reduced at frequencies above 5 mHz. Our basic data analysis procedure is the maximum likelihood detection method. We filter the data through the template bank at the first step of the search, then we refine parameters using the Nelder-Mead algorithm, we remove the strongest signal found and we repeat the procedure. We detect reliably and estimate parameters accurately of more than ten thousand signals from white dwarf binaries.

A search for lepton-flavor-violating process $e^{+}{e}^{-}\to e\mu$ in the energy region $\sqrt{s}=984–1060\mathrm{MeV}$ with the SND detector at the VEPP-2M $e^{+}{e}^{-}$ collider is reported. The model independent 90% C.L. upper limits on the $e^{+}{e}^{-}\to e\mu$ cross section, ${\sigma }_{e\mu }<8\mathrm{pb}$, as well as on the corresponding $\varphi \to e\mu$ branching fraction, $B(\varphi \to e\mu )<2\times {10}^{-6}$ have been obtained, for the polar angles $55°<\theta <125°$ of the final particles.

A search for muon neutrinos from Kaluza-Klein dark matter annihilations in the Sun has been performed with the 22-string configuration of the IceCube neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured lightest Kaluza-Klein particle (LKP) WIMPs in the Sun and converted to limits on the LKP-proton cross sections for LKP masses in the range 250–3000 GeV. These results are the most stringent limits to date on LKP annihilation in the Sun.

Recent results from the CDF Collaboration favor a large $CP$ asymmetry in $B_s\to K^{-}{\pi }^{+}$ decay, while the standard model prediction is very small. Moreover, the measurement of its branching ratio is lower than the standard model prediction based on the QCD factorization. We compute the gluino-mediated supersymmetry contributions to $B_s\to K^{(*)-}{\pi }^{+}$, $K^{(*)-}{\rho }^{+}$ decays in the framework of the mass insertion method, and find that for $\frac{m_{\tilde{g}}^2}{m_{\tilde{q}}^2}\le 2$, the theoretical predictions including the $LR$ and $RL$ mass insertion contributions are compatible with the measurements of $B_s\to K^{-}{\pi }^{+}$ decay and $B^0\mathrm{\text{−}}{\overline{B}}^0$ mixing within $2\sigma$ ranges. Using the constrained $LR$ and $RL$ mass insertion parameter spaces, we explore the supersymmetry mass insertion effects on the branching ratios, the direct $CP$ asymmetries, and the polarization fractions in $B_s\to K^{*-}{\pi }^{+}$, $K^{-}{\rho }^{+}$, $K^{*-}{\rho }^{+}$ decays. We find the constrained $LR$ and $RL$ insertions can provide sizable contributions to the branching ratios of $B_s\to K^{*-}{\pi }^{+}$, $K^{(*)-}{\rho }^{+}$ as well as the direct $CP$ asymmetry and the longitudinal polarization of $B_s\to K^{*-}{\rho }^{+}$ decay without conflict with all related data within $2\sigma$ ranges. Near future experiments at Fermi Lab and CERN LHC-b can test our predictions and shrink/reveal the mass insertion parameter spaces.

In the framework of the instanton vacuum model we evaluate the chiral perturbation theory low-energy constants $h_3$, $l_7$. We found that in the instanton vacuum model the constant $l_7$ is very sensitive to the shape of the instanton and the instanton vacuum parameters. We evaluated the constant $l_7$ for two different zero-mode profiles and as a function of the average instanton size $\rho$ and interinstanton distance $R$. Our result agrees with an old “order of magnitude” estimate of this constant from Gasser and Leutwyler [Ann. Phys. (N.Y.) 158, 142 (1984).]. The obtained value of $l_7$ implies that the pure QCD contribution to the pion mass difference is small, $\sim 1\%$ of the observed experimental value.

I present the next-to-next-to-leading-logarithm (NNLL) resummation of soft and collinear gluon corrections to single top quark production in the $s$ channel. Attaining NNLL accuracy involves the calculation of the two-loop soft anomalous dimension for the partonic subprocesses. Finite-order expansions of the resummed cross section are calculated through next-to-next-to-leading order. Numerical results are presented for $s$-channel single top quark production at the Tevatron and the LHC, including the dependence of the cross sections on the top quark mass and the uncertainties in the theoretical prediction. The higher-order corrections are significant for energies at both colliders and they decrease the theoretical uncertainty.

The quark condensate is calculated in terms of the effective string tension and the constituent quark mass. For 3 colors and 2 light flavors, the constituent mass is bounded from below by the value of 460 MeV. This value is only accessible when the string tension decreases linearly with the Schwinger proper time. For this reason, the Hausdorff dimension of a light-quark trajectory is equal to 4, indicating that these trajectories are similar to branched polymers, which can describe a weak first-order deconfinement phase transition in SU(3) Yang-Mills theory. Using this indication, we develop a gluon-chain model based on such trajectories.

We develop methods for computing the dynamics of fermion pair production by strong color electric fields including backreaction using the semiclassical Boltzmann-Vlasov (B-V) equation. We implement the Schwinger pair production by inserting a source term in the B-V equation which includes Pauli-Blocking effects. We present numerical results for a model with $SU(2)$ symmetries in ($1+1$) Cartesian dimensions.

Invisible $\psi$ and ${\rm Y}$ decays into light neutralinos, within the minimal or next-to-minimal supersymmetric standard model, are smaller than for $\nu \overline{\nu }$ production, even if light spin-0 particles are coupled to quarks and neutralinos. In a more general way, light dark matter particles are normally forbidden, unless they can annihilate sufficiently through a new interaction stronger than weak interactions (at lower energies), as induced by a light spin-1 $U$ boson, or heavy-fermion exchanges in the case of scalar dark matter. We discuss the possible contributions of $U$-boson, heavy-fermion, or spin-0 exchanges to invisible $\psi$ and ${\rm Y}$ decays. $U$ exchanges could lead, but not necessarily, to significant branching fractions for invisible decays into light dark matter. We show how one can get the correct relic density together with sufficiently small invisible branching fractions, and the resulting constraints on the $U$ couplings to ordinary particles and dark matter, in particular $|c_{\chi }{f}_{bV}|<5\times {10}^{-3}$ from ${\rm Y}$ decays, for $2m_{\chi }$ smaller than a few GeV. We also explain why there is no model-independent way to predict $\psi$ and ${\rm Y}$ branching fractions into light dark matter, from dark matter annihilation cross sections at freeze-out time.

The recent detection of secondary CMB anisotropy by the South Pole Telescope limits temperature fluctuations from the optical depth-modulated Doppler effect to $T_{3000}<\sqrt{13}\mu \mathrm{K}$ at multipoles $\ell \sim 3000$. This bound is the first empirical constraint on optical depth fluctuations at arcminute scales, ${\tau }_{3000}=0.001T_{3000}/\mu \mathrm{K}$, implying that these fluctuations are no more than a few percent of the mean. Modulation of the quadrupole source to polarization generates $B$ modes that are bounded as $B_{3000}=0.003T_{3000}$. The maximal extrapolation to the $\ell \sim 100$ gravitational wave regime yields $B_{100}=0.1T_{3000}$ and remains in excess of gravitational lensing if the comoving size of ionized regions is $R\gtrsim 80\mathrm{Mpc}$. If patchy reionization produces much of the observed arcminute scale temperature fluctuations, current bounds on $B_{100}$ already require $R\lesssim 200\mathrm{Mpc}$, and limits on both $T_{3000}$ and $B_{100}$ can be expected to improve rapidly.

We continue exploring free strings in the background of null Kasner-like cosmological singularities, following K. Narayan, arXiv:0904.4532. We study the free string Schrodinger wave functional along the lines of K. Narayan, arXiv:0807.1517. We find the wave functional to be nonsingular in the vicinity of singularities whose Kasner exponents satisfy certain relations. We compare this with the description in other variables. We then study certain regulated versions of these singularities where the singular region is replaced by a substringy but nonsingular region and study the string spectra in these backgrounds. The string modes can again be solved for exactly, giving some insight into how string oscillator states get excited near the singularity.

We consider the Casimir-Helmholtz free energy at nonzero temperature $T$ for a circular cylinder and perfectly conducting wedge closed by a cylindrical arc, either perfectly conducting or isorefractive. The energy expression at nonzero temperature may be regularized to obtain a finite value, except for a singular corner term in the case of the wedge which is present also at zero temperature. Assuming the medium in the interior of the cylinder or wedge be nondispersive with refractive index $n$, the temperature dependence enters only through the nondimensional parameter $2\pi naT$, $a$ being the radius of the cylinder or cylindrical arc. We show explicitly that the known zero-temperature result is regained in the limit $aT\to 0$ and that previously derived high-temperature asymptotics for the cylindrical shell are reproduced exactly.

We apply the decoherence formalism to an interacting scalar field theory. In the spirit of the decoherence literature, we consider a “system field” and an “environment field” that interact via a cubic coupling. We solve for the propagator of the system field, where we include the self-energy corrections due to the interaction with the environment field. In this paper, we consider an environment in the vacuum state ($T=0$). We show that neglecting inaccessible non-Gaussian correlators increases the entropy of the system as perceived by the observer. Moreover, we consider the effect of a changing mass of the system field in the adiabatic regime, and we find that at late times no additional entropy has been generated.

We present a model-independent method of dealing with fermion flavor mixing in the case when instead of constant, momentum-independent mass matrices one has rather momentum-dependent self-energies. This situation is typical for strongly coupled models of dynamical fermion mass generation. We demonstrate our approach on the example of quark mixing. We show that quark self-energies with a generic momentum dependence lead to an effective Cabibbo–Kobayashi–Maskawa matrix, which turns out to be in general nonunitary, in accordance with previous claims of other authors, and to nontrivial flavor changing electromagnetic and neutral currents. We also discuss some conceptual consequences of the momentum-dependent self-energies and show that in such a case the interaction basis and the mass basis are not related by a unitary transformation. In fact, we argue that the latter is merely an effective concept, in a specified sense. While focusing mainly on the fermionic self-energies, we also study the effects of momentum-dependent radiative corrections to the gauge bosons and to the proper vertices. Our approach is based on an application of the Lehmann–Symanzik–Zimmermann reduction formula and for the special case of constant self-energies it gives the same results as the standard approach based on the diagonalization of mass matrices.