The nature and origin of ultrahigh energy (UHE, referring to $>{10}^{19}\mathrm{eV})$ cosmic rays are great mysteries in modern astrophysics. The current theories for their explanation include the so-called top-down decay scenarios whose main signature is a large ratio of UHE gamma rays to protons. An important step in determining the primary composition at ultrahigh energies is the study of air shower development. UHE gamma ray induced showers are affected by the Landau-Pomeranchuk-Migdal (LPM) effect and the geomagnetic cascading process. In this work extensive simulations have been carried out to study the characteristics of air showers from UHE gamma rays. At energies above several times ${10}^{19}\mathrm{eV}$ the shower is affected by geomagnetic cascading rather than by the LPM effect. The properties of the longitudinal development such as the average depth of the shower maximum or its fluctuations depend strongly on both primary energy and incident direction. This feature may provide possible evidence of UHE gamma ray presence by fluorescence detectors.

We report on a study of sub-TeV $(10\mathrm{}\mathrm{GeV}<E_{\gamma }<1\mathrm{}\mathrm{TeV})$ gamma-ray-induced muon secondaries in coincidence with BATSE gamma ray bursts (GRBs). Each TeV gamma ray striking the atmosphere produces $\approx 0.2$ muons whose identity and angle can be measured by the Project GRAND array. Eight GRB candidates were studied; seven were selected based upon the optimum product of (detected BATSE fluence) $\times$ (GRAND’s acceptance). One candidate was added because it was reported as a possible detection by the Milagrito Collaboration. Seven candidates show a positive, though not statistically significant, muon excess. The only significant possible coincidence shows an excess of $466\pm 171$ muons during the BATSE T90 time interval for GRB 971110. The chance probability of such an excess in GRAND’s background at the time of this event is $3\times {10}^{-3}.$ The chance probability of observing such an excess in one of the eight bursts studied here is 0.025. If this event is real, the implied fluence of energetic $(>\mathrm{}10\mathrm{}\mathrm{GeV})$ gamma rays necessary to account for the observed muon excess would require that most of the GRB fluence arrived in the form of energetic gamma rays.

We present results from numerical simulations of the $\mathrm{}(2+1)\mathrm{}\mathrm{D}$ $\mathrm{SU}\left(2\right)\mathrm{}\otimes \mathrm{SU}\left(2\right)\mathrm{}$ Nambu–Jona-Lasinio model with $N_f=4\mathrm{}$ fermion flavors at zero and nonzero temperature T. At zero temperature, critical exponents extracted from the scaling of the order parameter and fermion mass are found to be consistent with next-to-leading order predictions of the ${1/N}_f$ expansion. At nonzero temperature we observe fermion mass generation despite the lack of chiral symmetry breaking, which is forbidden by the Colemann-Mermin-Wagner theorem for all $T>\mathrm{}0.\mathrm{}$ We study the effects of lattice discretization and finite volume on the dynamically generated fermion mass. By studying the lattice dispersion relation we also show that in the hot phase there is no significant temperature induced modification to the speed of light. Studies of the equation of state are made by measuring the pressure as a function of temperature and a comparison is made with large-$N_f$ predictions.

Compact lattice quantum electrodynamics with four species of fermions is simulated with massless quarks by adding a four-Fermi interaction to the action. Simulations in the chiral limit are done on $8^4$ lattices for exploratory purposes, and ${16}^4$ lattices for quantitative purposes, and the phase diagram, parametrized by the gauge and the four-Fermi couplings, is mapped out. The line of monopole condensation transitions is separate from the line of chiral symmetry restoration as long as the four-Fermi coupling is not too small. The simulation results indicate that the monopole condensation transition is first order while the chiral transition is second order. The challenges in determining the universality class of the chiral transition are discussed. If the scaling region for the chiral transition is sufficiently wide, the ${16}^4$ simulations predict critical indices far from mean field values. We briefly discuss a speculative scenario in which antiscreening provided by strands of bound monopole and antimonopole loops is the agent that balances the screening of fermion-antifermion pairs to produce ultraviolet stable fixed points.

In this paper we derive an integral equation for the evolution of unintegrated (longitudinally) polarized quark and gluon parton distributions. The conventional Catani-Ciafaloni-Fiorani-Marchesini (CCFM) framework is modified at small x in order to incorporate the QCD expectations concerning the double ${\ln }^2\mathrm{}(1/x)\mathrm{}$ resummation at low x for the integrated distributions. Complete Altarelli-Parisi splitting functions are included that makes the formalism compatible with the leading order Altarelli-Parisi evolution at large and moderately small values of x. The obtained modified polarized CCFM equation is shown to be partially diagonalized by the Fourier-Bessel transformation. Results of the numerical solution for this modifed polarized CCFM equation for the nonsinglet quark distributions are presented.

The general quasiparticle propagator in dense quark matter including all spin zero diquark condensates is derived for equal mass quarks. Specialized to an NJL model, this propagator includes one new condensate ${\Delta }_3$ in addition to the usual CFL condensate ${\Delta }_1.$ The gap equation is solved in two NJL models and the dependence on the quark mass of the condensates and the gap is presented. Analytic approximations for the condensates are obtained and compared to exact numerical solutions. The results are shown to differ from those obtained by neglecting ${\Delta }_3,$ especially for smaller values of ${\Delta }_1.$ The two different NJL models presented are also shown to give different results when ${\Delta }_3$ is not neglected. The methods used in this paper can be generalized to the physical case where only the strange quark is significantly massive.

Motivated by recent experimental results, we use a factorization approach to study the three-body $\overline{B}\to D^{\left(*\right)}{K}^{-}{K}^0$ decay modes. Two mechanisms are proposed for kaon pair production: current produced (from a vacuum) and transition (from the B meson). The $B^0\to D^{\left(*\right)+}{K}^{-}{K}^0$ decay is governed solely by the current-produced mechanism. As the kaon pair can be produced only by the vector current, the matrix element can be extracted from $e^{+}{e}^{-}\to K\overline{K}$ processes via isospin relations. The decay rates obtained this way are in good agreement with experiment. Both current-produced and transition processes contribute to $B^{-}\to D^{\left(*\right)0\mathrm{}}{K}^{-}{K}^0$ decays. By using QCD counting rules and the measured $B^{-}\to D^{\left(*\right)0\mathrm{}}{K}^{-}{K}^0$ decay rates, the measured decay spectra can be understood.

The process $e^{-}\overrightarrow{\gamma }{e}^{+}{W}_R^{-}{W}_R^{-}$ is studied in the framework of the left-right symmetric model. It is shown that this reaction and $e^{-}\overrightarrow{\gamma }{l}^{+}{W}_R^{-}{W}_R^{-}$ for the arbitrary final lepton are likely to be discovered at the CLIC collider. For a relatively light doubly charged Higgs boson its mass does not have much influence on the discovery potential, while for heavier values the probability of the reaction increases.

We reexamine the proof provided by Vafa and Witten that there is no spontaneous parity breaking in theories with vectorlike fermions. We argue that the various criticisms that have been leveled at the original proof do not invalidate it.

The spectrum of neutrinos produced by the outflow of high temperature matter surrounding microscopic black holes is calculated for neutrino energies between 1 GeV and the Planck energy. The results may be applicable for the last few hours and minutes of a microscopic black hole’s lifetime.

The origin of large scale cosmological magnetic fields remains a mystery, despite the continuous efforts devoted to that problem. We present a new model of magnetic field generation, based on local charge separation provided by an anisotropic and inhomogeneous radiation pressure. In the cosmological context, the processes we explore take place at the epoch of the reionization of the Universe. Under simple assumptions, we obtain results (i) in terms of the order of magnitude of the field generated at large scales and (ii) in terms of its power spectrum. The amplitudes obtained $(B\sim 8\times {10}^{-6}\mu \mathrm{G})$ are considerably higher than those obtained in usual magnetogenesis models and provide suitable seeds for amplification by adiabatic collapse and/or dynamo during structure formation.

The recent data on pp collisions at 158 GeV provide severe constraints on string models: These measurements allow us for the first time to determine how color strings are formed in ultrarelativistic proton-proton collisions.

Static, spherically symmetric solutions of the Einstein-Kalb-Ramond (KR) field equations have been obtained in this paper. In addition to an earlier known exact solution, we also find an approximate, asymptotically flat solution for which the metric coefficients are obtained as an infinite series in $1/r.$ Subsequently, we study gravitational lensing and perihelion precession in these spacetimes and obtain explicit formulas which include corrections to these effects in the presence of the KR field.

In lepton-number-violating supersymmetric models, there is no natural choice of basis to distinguish the down-type Higgs and lepton superfields. We employ basis-independent techniques to identify the massless Majoron and associated light scalar in the case of spontaneously broken lepton number $\mathrm{}\left(L\right).$ When explicit L violation is added, these two scalars can acquire masses of the order of the electroweak scale and can be identified as massive sneutrinos.

We present the details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on lattices of size ${32}^3\times 56–{64}^3\times 112$ at four values of lattice spacings in the range $a\approx 0.1–0.05\mathrm{fm}$ and spatial extent $L_{s}a\approx 3\mathrm{fm}.$ Hadronic observables are calculated at five quark masses corresponding to $m_{\mathrm{PS}}{/m}_V\approx 0.75–0.4,$ assuming the u and d quarks are degenerate, but treating the s quark separately. We find that the presence of quenched chiral singularities is supported from an analysis of the pseudoscalar meson data. The physical values of hadron masses are determined using $m_{\pi },$ $m_{\rho },$ and $m_K$ (or $m_{\phi })$ as input to fix the physical scale of lattice spacing and the u, d, and s quark masses. After chiral and continuum extrapolations, the agreement of the calculated mass spectrum with experiment is at a 10% level. In comparison with the statistical accuracy of 1%–3% and systematic errors of at most 1.7% we have achieved, this demonstrates a failure of the quenched approximation for the hadron spectrum: the hyperfine splitting in the meson sector is too small, and in the baryon sector the octet masses and mass splitting of the decuplet are both smaller than experiment. Light quark masses are calculated using two definitions: the conventional one and the one based on the axial-vector Ward identity. The two results converge toward the continuum limit, yielding $m_{\mathrm{ud}}{=4.29\mathrm{}\left(14\right)\mathrm{}}_{-0.79}^{+0.51\mathrm{}}\mathrm{MeV}$ where the first error is statistical and the second one is systematic due to chiral extrapolation. The s quark mass depends on the strange hadron mass chosen for input: $m_s{=113.8\mathrm{}\left(2.3\right)\mathrm{}}_{-2.9}^{+5.8\mathrm{}}\mathrm{MeV}$ from $m_K$ and $m_s{=142.3\mathrm{}\left(5.8\right)\mathrm{}}_{-0}^{+22.0\mathrm{}}\mathrm{MeV}$ from $m_{\phi },$ indicating again a failure of the quenched approximation. We obtain the scale of QCD, ${\Lambda }_{\overline{\mathrm{MS}}}^{\mathrm{}\left(0\right)\mathrm{}}=219.5\mathrm{}\left(5.4\right)\mathrm{}\mathrm{MeV}$ with $m_{\rho }$ used as input. An $O(10\%)\mathrm{}$ deviation from experiment is observed in the pseudoscalar meson decay constants.

On the lattice we study the gauge boson propagator of three-dimensional compact QED in the Landau gauge at zero and nonzero temperature. The nonperturbative effects are taken into account by the generation of a mass, by an anomalous dimension, and by photon wave function renormalization. All these effects can be attributed to the monopoles: they are absent in the propagator of the singularity-free part of the gauge field. We assess carefully the Gribov copy problem for the propagator and the parameters emerging from the fits.

We present the complete next-to-leading order QCD corrections to the polarized hadroproduction of heavy flavors which soon will be studied experimentally in polarized pp collisions at the BNL Relativistic Heavy Ion Collider (RHIC) in order to constrain the polarized gluon density $\Delta g.\mathrm{}$ It is demonstrated that the dependence on unphysical renormalization and factorization scales is strongly reduced beyond the leading order. The sensitivity of the charm quark spin asymmetry to $\Delta g$ is analyzed in some detail, including the limited detector acceptance for leptons from charm quark decays at the BNL RHIC.

An integral representation for generalized parton distributions of spin-0 hadrons is suggested, which satisfies both polynomiality and positivity constraints.

We study exclusive B decays to final states containing a charmed baryon within the pole model framework. Since the strong coupling for ${\Lambda }_b\overline{B}N$ is larger than that for ${\Sigma }_b\overline{B}N,$ the two-body charmful decay $B^{-}\to {\Sigma }_c^0\overline{p}$ has a rate larger than $B^0\to {\Lambda }_c^{+}\overline{p}$ as the former proceeds via the ${\Lambda }_b$ pole while the latter via the ${\Sigma }_b$ pole. By the same token, the three-body decay $B^0\to {\Sigma }_c^{++}\overline{p}{\pi }^{-}$ receives less of a baryon-pole contribution than $B^{-}\to {\Lambda }_c^{+}\overline{p}{\pi }^{-}.$ However, because the important charmed-meson pole diagrams contribute constructively to the former and destructively to the latter, ${\Sigma }_c^{++}\overline{p}{\pi }^{-}$ has a rate slightly larger than ${\Lambda }_c^{+}\overline{p}{\pi }^{-}.$ It is found that one-quarter of the $B^{-}\to {\Lambda }_c^{+}\overline{p}{\pi }^{-}$ rate comes from the resonant contributions. We discuss the decays $B^0\to {\Sigma }_c^0\overline{p}{\pi }^{+}$ and $B^{-}\to {\Sigma }_c^0\overline{p}{\pi }^0$ and stress that they are not color suppressed even though they can only proceed via an internal W emission.

Future experiments will produce high-resolution temperature maps of the cosmic microwave background (CMB) and are expected to reveal the signature of gravitational lensing by intervening large-scale structures. We construct all-sky maximum-likelihood estimators that use the lensing effect to estimate the projected density (convergence) of these structures, its power spectrum, and cross-correlation with other observables. This contrasts with earlier quadratic-estimator approaches that Taylor expanded the observed CMB temperature to linear order in the lensing deflection angle; these approaches gave estimators for the temperature-convergence correlation in terms of the CMB three-point correlation function and for the convergence power spectrum in terms of the CMB four-point correlation function, which can be biased and nonoptimal due to terms beyond the linear order. We show that for sufficiently weak lensing, the maximum-likelihood estimator reduces to the computationally less demanding quadratic estimator. The maximum likelihood and quadratic approaches are compared by evaluating the root-mean-square (rms) error and bias in the reconstructed convergence map in a numerical simulation; it is found that both the rms errors and bias are of order 1 percent for the case of Planck and of order 10–20 percent for a 1 arcminute beam experiment. We conclude that for recovering lensing information from temperature data acquired by these experiments, the quadratic estimator is close to optimal, but further work will be required to determine whether this is also the case for lensing of the CMB polarization field.