Using the CLEO III detector, we measure absolute cross sections for $e^{+}{e}^{-}\to \mathrm{\text{hadrons}}$ at seven center-of-mass energies between 6.964 and 10.538 GeV. The values of $R$, the ratio of hadronic and muon pair production cross sections, are determined within 2% total root-mean-square uncertainty.

A measurement of the top quark pair production cross section in proton antiproton collisions at an interaction energy of $\sqrt{s}=1.96\mathrm{TeV}$ is presented. This analysis uses $405\pm 25{\mathrm{pb}}^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic $t\overline{t}$ decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The $t\overline{t}$ cross section is measured as ${\sigma }_{t\overline{t}}={4.5}_{-1.9}^{+2.0}(\mathrm{stat}{)}_{-1.1}^{+1.4}(\mathrm{syst})\pm 0.3(\mathrm{lumi})\mathrm{pb}$ for a top quark mass of $m_t=175\mathrm{GeV}/c^2$.

We perform a detailed conformal field theory analysis of $D2$-brane instanton effects in four-dimensional type IIA string vacua with intersecting $D6$-branes. In particular, we explicitly compute instanton induced fermion two-point couplings which play the role of perturbatively forbidden Majorana mass terms for right-handed neutrinos or MSSM $\mu$ terms. These results can readily be extended to higher-dimensional operators. In concrete realizations of such nonperturbative effects, the Euclidean $D2$-brane has to wrap a rigid, supersymmetric cycle with strong constraints on the zero-mode structure. Their implications for type IIA compactifications on the $T^6/({\mathbb{Z}}_2\times {\mathbb{Z}}_2)$ orientifold with discrete torsion are analyzed. We also construct a local supersymmetric GUT-like model allowing for a class of Euclidean $D2$-branes whose fermionic zero modes meet all the constraints for generating Majorana masses in the phenomenologically allowed regime. Together with perturbatively realized Dirac masses, these nonperturbative couplings give rise to the seesaw mechanism.

When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released $ϵ$ and the duration of the emission $\tau$, scaled by the total binary mass $M$. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of $\lesssim {10}^{2}M$. For characteristic emission parameters at the final plunge between binary black holes of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of ${10}^{-3}$. Accounting for the wave distortion would significantly decrease the waveform extraction errors in numerical simulations.

We study collisions of two high-energy closed strings in the framework of $D$-dimensional general relativity. The model of a high-energy closed string is introduced as a $pp$-wave generated by a ring-shaped source with the radius $R$. At the instant of the collision, the positions of two strings are assumed to coincide precisely. In this setup, we study the formation of two kinds of apparent horizons (AHs): the AH of topology $S^{D-2}$ (the black hole AH) and the AH of topology $S^1\times S^{D-3}$ (the black ring AH). These two AHs are solved numerically and the conditions for the formation of the two AHs are clarified in terms of the ring radius $R$. Specifically, we demonstrate that the black ring AH forms for sufficiently large $R$. The effects of an impact parameter and the relative orientation of incoming strings in more general cases are briefly discussed.

Tremendous progress has been made towards the solution of the binary-black-hole problem in numerical relativity. The waveforms produced by numerical relativity will play a role in gravitational wave detection as either test beds for analytic template banks or as template banks themselves. As the parameter space explored by numerical relativity expands, the importance of quantifying the effect that each parameter has on first the detection of gravitational waves and then the parameter estimation of their sources increases. In light of this, we present a study of equal-mass, spinning binary-black-hole evolutions through matched filtering techniques commonly used in data analysis. We study how the match between two numerical waveforms varies with numerical resolution, initial angular momentum of the black holes, and the inclination angle between the source and the detector. This study is limited by the fact that the spinning black-hole binaries are oriented axially and the waveforms only contain approximately two and a half orbits before merger. We find that for detection purposes, spinning black holes require the inclusion of the higher harmonics in addition to the dominant mode, a condition that becomes more important as the black-hole spins increase. In addition, we conduct a preliminary investigation of how well a template of fixed spin and inclination angle can detect target templates of arbitrary but nonprecessing spin and inclination for the axial case considered here.

We study Newtonian cosmological perturbation theory from a field theoretical point of view. We derive a path integral representation for the cosmological evolution of stochastic fluctuations. Our main result is the closed form of the generating functional valid for any initial statistics. Moreover, we extend the renormalization group method proposed by Mataresse and Pietroni to the case of primordial non-Gaussian density and velocity fluctuations. As an application, we calculate the nonlinear propagator and examine how the non-Gaussianity affects the memory of cosmic fields to their initial conditions. It turns out that the non-Gaussianity affects the nonlinear propagator. In the case of positive skewness, the onset of the nonlinearity is advanced with a given comoving wave number. On the other hand, the negative skewness gives the opposite result.

We investigate the enhancement of lepton number, energy, and entropy transport resulting from active-sterile neutrino conversion ${\nu }_e\to {\nu }_s$ deep in the post-bounce supernova core followed by reconversion ${\nu }_s\to {\nu }_e$ further out, near the neutrino sphere. We explicitly take account of shock wave and neutrino heating modification of the active neutrino forward scattering potential which governs sterile neutrino production. We find that the ${\nu }_e$ luminosity at the neutrino sphere could be increased by between $\sim 10\%$ and $\sim 100\%$ during the crucial shock reheating epoch if the sterile neutrino has a rest mass and vacuum mixing parameters in ranges which include those required for viable sterile neutrino dark matter. We also find sterile neutrino transport-enhanced entropy deposition ahead of the shock. This ‘‘preheating” can help melt heavy nuclei and thereby reduce the nuclear photo-dissociation burden on the shock. Both neutrino luminosity enhancement and preheating could increase the likelihood of a successful core collapse supernova explosion.

Two methods of constraining the properties of dark energy are weak lensing tomography and cluster counting. Uncertainties in mass calibration of clusters can be reduced by using the properties of halo clustering (the clustering of clusters). However, within a single survey, weak lensing and halo clustering probe the same density fluctuations. We explore the question of whether this information can be used twice—once in weak lensing and then again in halo clustering to calibrate cluster masses—or whether the combined dark energy constraints are weaker than the sum of the individual constraints. For a survey like the Dark Energy Survey (DES), we find that the cosmic shearing of source galaxies at high redshifts is indeed highly correlated with halo clustering at lower redshifts. Surprisingly, this correlation does not degrade cosmological constraints for a DES-like survey, and in fact, constraints are marginally improved since the correlations themselves act as additional observables. This considerably simplifies the analysis for a DES-like survey: when weak lensing and halo clustering are treated as independent experiments, the combined dark energy constraints (cluster counts included) are accurate if not slightly conservative. Our findings mirror those of Takada and Bridle, who investigated correlations between the cosmic shear and cluster counts.

The detection of neutrinos from SN 1987A by the Kamiokande-II and Irvine-Michigan-Brookhaven detectors provided the first glimpse of core collapse in a supernova, complementing the optical observations and confirming our basic understanding of the mechanism behind the explosion. One long-standing puzzle is that, when fitted with thermal spectra, the two independent detections do not seem to agree with either each other or typical theoretical expectations. We assess the compatibility of the two data sets in a model-independent way and show that they can be reconciled if one avoids any bias on the neutrino spectrum stemming from theoretical conjecture. We reconstruct the neutrino spectrum from SN 1987A directly from the data through nonparametric inferential statistical methods and present predictions for the diffuse supernova neutrino background based on SN 1987A data. We show that this prediction cannot be too small (especially in the 10–18 MeV range), since the majority of the detected events from SN 1987A were above 18 MeV (including 6 events above 35 MeV), suggesting an imminent detection in operational and planned detectors.

The analysis of gravitational wave data involves many model selection problems. The most important example is the detection problem of selecting between the data being consistent with instrument noise alone, or instrument noise and a gravitational wave signal. The analysis of data from ground based gravitational wave detectors is mostly conducted using classical statistics, and methods such as the Neyman-Peterson criteria are used for model selection. Future space based detectors, such as the Laser Interferometer Space Antenna (LISA), are expected to produce rich data streams containing the signals from many millions of sources. Determining the number of sources that are resolvable, and the most appropriate description of each source poses a challenging model selection problem that may best be addressed in a Bayesian framework. An important class of LISA sources are the millions of low-mass binary systems within our own galaxy, tens of thousands of which will be detectable. Not only are the number of sources unknown, but so are the number of parameters required to model the waveforms. For example, a significant subset of the resolvable galactic binaries will exhibit orbital frequency evolution, while a smaller number will have measurable eccentricity. In the Bayesian approach to model selection one needs to compute the Bayes factor between competing models. Here we explore various methods for computing Bayes factors in the context of determining which galactic binaries have measurable frequency evolution. The methods explored include a reverse jump Markov chain Monte Carlo algorithm, Savage-Dickie density ratios, the Schwarz-Bayes information criterion, and the Laplace approximation to the model evidence. We find good agreement between all of the approaches.

The discovery in the last few years of states belonging to the extended charmonium family has highlighted the importance of the closeness of decay channels to an understanding of many of these mesons. We aid this debate by illustrating a simple calculational procedure for including the effect of open and nearby closed channels.

We show that the recent paper [Eur. Phys. J. A 24, 437 (2005)], claiming that the radiative decays $\varphi \to a_0(980)\gamma$ and $\varphi \to f_0(980)\gamma$ should be of the same order of magnitude regardless of whether the $a_0(980)$ and $f_0(980)$ are compact four-quark states or extended $K\overline{K}$ molecule states, is misleading.

In the approximation of neglecting the flavor mixing between $u$ and $d$ quarks in the vector channel, we derive a formula for the quark-number susceptibility based on the external field method. This formula proves to yield exactly the Fermi statistics result of the quark-number susceptibility in the noninteracting situation. Then calculation in an effective interaction model via Dyson-Schwinger equations is performed and it is found that at low temperatures it is zero and it rises sharply to nonzero values across the phase transition point, which is consistent with previous lattice QCD results. The interpretation of this behavior of the quark-number susceptibility as a signal of chiral symmetry restoration and deconfinement is discussed.

The properties of the pseudoscalar Goldstone bosons in the color-flavor locked phase at moderate densities are studied within a model of the Nambu-Jona-Lasinio type. The Goldstone bosons are constructed explicitly by solving the Bethe-Salpeter equation for quark-quark scattering in random phase approximation. The main focuses of our investigations are (i) the weak decay constant in the chiral limit, (ii) the masses of the flavored (pseudo)Goldstone bosons for nonzero but equal quark masses, (iii) their masses and effective chemical potentials for nonequal quark masses, and (iv) the onset of kaon condensation. We compare our results with the predictions of the low-energy effective field theory. The deviations from results obtained in the weak-coupling limit are discussed in detail.

The relation between the deconfinement and chiral phase transition is explored in the framework of a Polyakov-loop-extended two-flavor quark-meson (PQM) model. In this model the Polyakov loop dynamics is represented by a background temporal gauge field which also couples to the quarks. As a novelty an explicit quark chemical potential and $N_f$-dependence in the Polyakov loop potential is proposed by using renormalization group arguments. The behavior of the Polyakov loop as well as the chiral condensate as function of temperature and quark chemical potential is obtained by minimizing the grand canonical thermodynamic potential of the system. The effect of the Polyakov loop dynamics on the chiral phase diagram and on several thermodynamic bulk quantities is presented.

Under the constraints of heavy quark effective theory the equations of motion of heavy meson distribution amplitudes of definite geometric twist, using the knowledge of their off-cone structure, are reformulated as a set of algebraic equations. Together with equations due to various Dirac structures various relations between the (sets of) independent two- and three-particle distribution amplitudes of definite geometric twist are derived and presented using both the notion of (double) Mellin moments and resummed nonlocal distribution amplitudes. Resolving these relations for the independent two-particle moments in terms of three-particle double moments we confirmed the representation of ${\Phi }_{\pm |n}$ by Kawamura et al. [Phys. Lett. B 523, 111 (2001)].

We evaluate baryon wave functions in both the Coulomb and Landau gauges in lattice QCD. These are constructed from quark propagators calculated with the overlap Dirac operator on quenched gauge configurations at $\beta =6$. By comparing baryon states that differ in their diquark content, we find evidence for enhanced correlation in the scalar diquark channel, as favored by quark models. We also summarize earlier results for diquark masses in the Landau gauge, casting them in a form more easily compared with subsequent studies.

Current experimental data allow the zero value for one neutrino mass, either $m_1=0$ or $m_3=0$. This observation implies that a realistic neutrino mass texture can be established by starting from the limit (a) $m_1=m_2=0$ and $m_3\ne 0$ or (b) $m_1=m_2\ne 0$ and $m_3=0$. In both cases, we may introduce a particular perturbation which ensures the resultant neutrino mixing matrix to be the tribimaximal mixing pattern or its viable variations with all entries being formed from small integers and their square roots. We find that it is natural to incorporate this kind of neutrino mass matrix in the minimal type-II seesaw model with only one heavy right-handed Majorana neutrino $N$ in addition to the $\mathrm{SU}(2{)}_L$ Higgs triplet ${\Delta }_L$. We show that it is possible to account for the cosmological baryon number asymmetry in the $m_3=0$ case via thermal leptogenesis, in which the one-loop vertex correction to $N$ decays is mediated by ${\Delta }_L$ and the $CP$-violating asymmetry of $N$ decays is attributed to the electron flavor.

We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks, and $R$-parity breaking interactions. We focus on future proposals to measure coherent neutrino-nuclei scattering and neutrino-electron elastic scattering. We introduce a new comparative analysis between these experiments and show that in different types of new physics it is possible to obtain competitive bounds to those of present and future collider experiments. For the cases of leptoquarks and $R$-parity breaking interactions we found that the expected sensitivity for most of the future low energy experimental setups is better than the current constraints.