Using data acquired with the CLEO detector at the CESR $e^{+}{e}^{-}$ collider at $\sqrt{s}=3.773\mathrm{GeV}$, we measure the cross section for the radiative return process $e^{+}{e}^{-}\to \gamma J/\psi$, $J/\psi \to {\mu }^{+}{\mu }^{-}$, resulting in $\mathcal{B}(J/\psi \to {\mu }^{+}{\mu }^{-})\times {\Gamma }_{ee}(J/\psi )=0.3384\pm 0.0058\pm 0.0071\mathrm{keV}$, ${\Gamma }_{ee}(J/\psi )=5.68\pm 0.11\pm 0.13\mathrm{keV}$, and ${\Gamma }_{\mathrm{tot}}(J/\psi )=95.5\pm 2.4\pm 2.4\mathrm{keV}$, in which the errors are statistical and systematic, respectively. We also determine the ratio ${\Gamma }_{ee}[\psi (2S)]/{\Gamma }_{ee}(J/\psi )=0.45\pm 0.01\pm 0.02$.

The Penrose transform between twistors and the phase space of massless particles is generalized from the massless case to an assortment of other particle dynamical systems, including special examples of massless or massive particles, relativistic or nonrelativistic, interacting or noninteracting, in flat space or curved spaces. Our unified construction involves always the same twistor $Z^A$ with only four complex degrees of freedom and subject to the same helicity constraint. Only the twistor to phase space transform differs from one case to another. Hence, a unification of diverse particle dynamical systems is displayed by the fact that they all share the same twistor description. Our single twistor approach seems to be rather different and a strikingly economical construction of twistors compared to other past approaches that introduced multiple twistors to represent some similar but far more limited set of particle phase space systems.

High energy neutrino emission from gamma-ray bursts (GRBs) is discussed. In this paper, by using the simulation kit GEANT4, we calculate proton cooling efficiency including pion-multiplicity and proton-inelasticity in photomeson production. First, we estimate the maximum energy of accelerated protons in GRBs. Using the obtained results, neutrino flux from one burst and a diffuse neutrino background are evaluated quantitatively. We also take account of cooling processes of pion and muon, which are crucial for resulting neutrino spectra. We confirm the validity of analytic approximate treatments on GRB fiducial parameter sets, but also find that the effects of multiplicity and high-inelasticity can be important on both proton cooling and resulting spectra in some cases. Finally, assuming that the GRB rate traces the star formation rate, we obtain a diffuse neutrino background spectrum from GRBs for specific parameter sets. We introduce the nonthermal baryon-loading factor, rather than assume that GRBs are main sources of ultra-high energy cosmic rays (UHECRs). We find that the obtained neutrino background can be comparable with the prediction of Waxman and Bahcall, although our ground in estimation is different from theirs. In this paper, we study on various parameters since there are many parameters in the model. The detection of high energy neutrinos from GRBs will be one of the strong evidences that protons are accelerated to very high energy in GRBs. Furthermore, the observations of a neutrino background has a possibility not only to test the internal shock model of GRBs but also to give us information about parameters in the model and whether GRBs are sources of UHECRs or not.

We calculate the $B\to D$ and $B\to D^{*}$ form factors at zero recoil in staggered chiral perturbation theory. We consider heavy-light mesons in which only the light ($u$, $d$, or $s$) quark is staggered; current lattice simulations generally use a highly improved action such as the Fermilab or nonrelativistic QCD action for the heavy ($b$ or $c$) quark. We work to lowest nontrivial order in the heavy-quark expansion and to one-loop order in the chiral expansion. We present results for a partially quenched theory with three sea quarks in which there are no mass degeneracies (the “$1+1+1$” theory) and for a partially quenched theory in which the $u$ and $d$ sea quark masses are equal (the “$2+1$” theory). We also present results for full ($2+1$) QCD, along with a numerical estimate of the size of staggered discretization errors. Finally, we calculate the finite volume corrections to the form factors and estimate their numerical size in current lattice simulations.

The ground state energy of a boundary quantum field theory is derived in planar geometry in $D+1$-dimensional spacetime. It provides a universal expression for the Casimir energy which exhibits its dependence on the boundary conditions via the reflection amplitudes of the low energy particle excitations. We demonstrate the easy and straightforward applicability of the general expression by analyzing the free scalar field with Robin boundary condition and by rederiving the most important results available in the literature for this geometry.

We calculate analytically quasinormal modes of AdS Schwarzschild black holes including first-order corrections. We consider massive scalar, gravitational and electromagnetic perturbations. Our results are in good agreement with numerical calculations. In the case of electromagnetic perturbations, ours is the first calculation to provide an analytic expression for quasinormal frequencies, because the effective potential vanishes at zeroth order. We show that the first-order correction is logarithmic.

We investigate a Bianchi type-I cosmology with $k$-essence and find the set of models which dissipate the initial anisotropy. There are cosmological models with extended tachyon fields and $k$-essence having a constant barotropic index. We obtain the conditions leading to a regular bounce of the average geometry and the residual anisotropy on the bounce. For constant potential, we develop purely kinetic $k$-essence models which are dust dominated in their early stages, dissipate the initial anisotropy, and end in a stable de Sitter accelerated expansion scenario. We show that linear $k$-field and polynomial kinetic function models evolve asymptotically to Friedmann-Robertson-Walker cosmologies. The linear case is compatible with an asymptotic potential interpolating between $V_l\propto {\varphi }^{-{\gamma }_l}$, in the shear dominated regime, and $V_l\propto {\varphi }^{-2}$ at late time. In the polynomial case, the general solution contains cosmological models with an oscillatory average geometry. For linear $k$-essence, we find the general solution in the Bianchi type-I cosmology when the $k$ field is driven by an inverse square potential. This model shares the same geometry as a quintessence field driven by an exponential potential.

Important observables to reveal the nature of dark energy are the equation of state $w$ and its time derivative in units of the Hubble time $w^{\prime }$. Recently, it was shown that the simplest scalar field models of dark energy (quintessence) occupy rather narrow regions in the $w-w^{\prime }$ plane. We extend the $w-w^{\prime }$ plane to $w<-1$ and derive bounds on $w^{\prime }$ as a function of $w$ for tracker phantom dark energy. We also derive bounds on tracker k-essence. The observational window for $w^{\prime }$ for $w<-1$ is not narrow, $\sigma (w^{\prime })\lesssim 6|1+w|$.

We discuss prospects for direct measurement of stochastic gravitational wave background around 0.1–1 Hz with future space missions. It is assumed to use correlation analysis technique with the optimal time-delay-interferometry (TDI) variables for two sets of LISA-type interferometers. The signal to noise for detection of the background and the estimation errors for its basic parameters (amplitude, spectral index) are evaluated for proposed missions.

A model with flavor-triplet Higgs scalars ${\varphi }_i$ ($i=1,2,3$) is investigated under a permutation symmetry ${\mathrm{S}}_3$ and its symmetry breaking. A possible ${\mathrm{S}}_3$ breaking form of the Higgs potential whose vacuum expectation values $v_i=⟨{\varphi }_i⟩$ satisfy a relation $v_1^2+v_2^2+v_3^2=\frac{2}{3}(v_1+v_2+v_3{)}^2$ is investigated, because if we suppose a seesaw-like mass matrix model $M_e=m{M}^{-1}m$ with $m_{ij}\propto {\delta }_{ij}{v}_i$ and $M_{ij}\propto {\delta }_{ij}$, such a model can lead to the well-known charged lepton mass relation $m_e+m_{\mu }+m_{\tau }=\frac{2}{3}(\sqrt{m_e}+\sqrt{m_{\mu }}+\sqrt{m_{\tau }}{)}^2$.

A model is presented to illustrate that vacuum neutrino oscillations can be essentially $T$ and $CP$ invariant up to a certain energy but strongly $T$ and $CP$ noninvariant at much higher energies. Detailed model results for the vacuum probabilities $P({\nu }_{\mu }\to {\nu }_e)$ and $P({\nu }_e\to {\nu }_{\mu })$ are given, which may be relevant to proposed long-baseline neutrino-oscillation experiments.

We study matter effects which arise in the muon neutrino oscillation and survival probabilities relevant to atmospheric neutrino and very long baseline ($>4000\mathrm{Km}$) beam experiments. The interrelations between the three probabilities ${\mathrm{P}}_{\mu \mathrm{e}}$, ${\mathrm{P}}_{\mu \tau }$, and ${\mathrm{P}}_{\mu \mu }$ are examined. It is shown that large and observable sensitivity to the neutrino mass hierarchy can be present in ${\mathrm{P}}_{\mu \mu }$ and ${\mathrm{P}}_{\mu \tau }$. We emphasize that at baselines $>7000\mathrm{Km}$, matter effects in ${\mathrm{P}}_{\mu \tau }$ are important under certain conditions and can be large. The muon survival rates in experiments with very long baselines thus depend on matter effects in both ${\mathrm{P}}_{\mu \tau }$ and ${\mathrm{P}}_{\mu \mathrm{e}}$. We also indicate where these effects provide sensitivity to ${\theta }_{13}$ and identify ranges of energies and baselines where this sensitivity is maximum. The effect of parameter degeneracies in the three probabilities at these baselines and energies is studied in detail and large parts of the parameter space are identified which are free from these degeneracies. In the second part of the paper, we focus on using the matter effects studied in the first part as a means of determining the mass hierarchy via atmospheric neutrinos. Realistic event rate calculations are performed for a charge discriminating 100 kT iron calorimeter which demonstrate the possibility of realizing this very important goal in neutrino physics. It is shown that for atmospheric neutrinos, a careful selection of energy and baseline ranges is necessary in order to obtain a statistically significant signal, and that the effects are largest in bins where matter effects in both ${\mathrm{P}}_{\mu \mathrm{e}}$ and ${\mathrm{P}}_{\mu \tau }$ combine constructively. Under these conditions, up to a $4\sigma$ signal for matter effects is possible (for ${\Delta }_{31}>0$) within a time scale appreciably shorter than the one anticipated for neutrino factories.

Results on a search for pair production of second-generation scalar leptoquark in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ are reported. The data analyzed were collected by the CDF detector during the 2002–2003 Tevatron Run II and correspond to an integrated luminosity of $198{\mathrm{pb}}^{-1}$. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQ production and derive 95% C.L. upper limits on the LQ production cross sections as well as lower limits on their mass as a function of $\beta$, where $\beta$ is the branching fraction for $\mathrm{LQ}\to \mu q$.

We present a search for anomalous semileptonic decays of heavy flavor hadrons produced in association with a $W$ boson in proton-antiproton collisions at $\sqrt{s}=1.96\mathrm{TeV}$. We use $162{\mathrm{pb}}^{-1}$ of data collected with the CDF II detector at the Fermilab Tevatron Collider. We select events with one $W$ boson and at least one jet with an identified secondary vertex. In the jets with a secondary vertex we look for a semileptonic decay to a muon. We compare the number of jets with both a secondary vertex and a semileptonic decay and the kinematic properties of these jets, with the standard model expectation of $W$ plus heavy flavor production and decay. No discrepancy is seen between the observation and the expectation, and we set limits on the production cross section of a $B$-like hadron with an anomalously high semileptonic branching ratio.

We explore the possibilities for scaling violation in gauge theories that have string duals. Like in perturbative QCD, short-distance behavior yields logarithms that violate the scaling.

We explore the possibility that quantum cosmology considerations could provide a selection principle in the landscape of string vacua. We propose that the universe emerged from the string era in a thermally excited state and determine, within a mini-superspace model, the probability of tunneling to different points on the landscape. We find that the potential energy of the tunneling endpoint from which the universe emerges and begins its classical evolution is determined by the primordial temperature. By taking into account some generic properties of the moduli potential we then argue that the tunneling to the tail of the moduli potentials is disfavored, that the most likely emergence point is near an extremum, and that this extremum is not likely to be in the outer region of moduli space where the compact volume is very large and the string coupling very weak. As a concrete example we discuss the application of our arguments to the Kachru, Kallosh, Linde and Trivedi model of moduli stabilization.

The electrical conductivity of a pion gas at low temperatures is studied in the framework of linear response and chiral perturbation theory. The standard ChPT power counting has to be modified to include pion propagator lines with a nonzero thermal width in order to properly account for collision effects typical of kinetic theory. With this modification, we discuss the relevant chiral power counting to be used in the calculation of transport coefficients. The leading order contribution is found and we show that the dominant higher order ladder diagrams can be treated as perturbative corrections at low temperatures. We find that the DC conductivity $\sigma (T)$ is a decreasing function of $T$, behaving for very low $T$ as $\sigma (T)\sim e^2{m}_{\pi }\sqrt{m_{\pi }/T}$, consistently with nonrelativistic kinetic theory. When unitarization effects are included, $\sigma (T)$ increases slowly as $T$ approaches the chiral phase transition. We compare with related works and discuss some physical consequences, especially in the context of the low-energy hadronic photon spectrum in relativistic heavy ion collisions.

Accurate calculation of the gradual inspiral motion in an extreme mass-ratio binary system, in which a compact object inspiral towards a supermassive black hole requires calculation of the interaction between the compact object and the gravitational perturbations that it induces. These metric perturbations satisfy linear partial differential equations on a curved background space-time induced by the supermassive black hole. At the point-particle limit the second-order perturbations equations have source terms that diverge as $r^{-4}$, where $r$ is the distance from the particle. This singular behavior renders the standard retarded solutions of these equations ill defined. Here we resolve this problem and construct well-defined and physically meaningful solutions to these equations. We recently presented an outline of this resolution [E. Rosenthal, Phys. Rev. D 72, 121503 (2005).]. Here we provide the full details of this analysis. These second-order solutions are important for practical calculations: the planned gravitational-wave detector LISA requires preparation of waveform templates for the potential gravitational waves. Construction of templates with desired accuracy for extreme mass-ratio binaries requires accurate calculation of the inspiral motion including the interaction with the second-order gravitational perturbations.

We consider chiral fermion confinement in scalar thick branes, which are known to localize gravity, coupled through a Yukawa term. The conditions for the confinement and their behavior in the thin-wall limit are found for various different BPS branes, including double walls and branes interpolating between different $\mathrm{Ad}{\mathrm{S}}_5$ spacetimes. We show that only one massless chiral mode is localized in all these walls, whenever the wall thickness is keep finite. We also show that, independently of wall’s thickness, chiral fermionic modes cannot be localized in $\mathrm{d}{\mathrm{S}}_4$ walls embedded in a $M_5$ spacetime. Finally, massive fermions in double wall spacetimes are also investigated. We find that, besides the massless chiral mode localization, these double walls support quasilocalized massive modes of both chiralities.

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected gravitational wave (GW) is a quasiperiodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. The time-frequency representation and pattern search algorithm are fully determined by the reformulation. This contrasts with the other time-frequency based methods presented in the literature for the same problem, where these choices are justified by “ad hoc” arguments. In particular, the time-frequency representation has to be unitary. Finally, we assess the performance, robustness and computational cost of the proposed method with several benchmarks using simulated data.