We investigate the properties of the ground state of strong coupling lattice QCD at finite density. Our starting point is the effective Hamiltonian for color singlet objects, which looks at lowest order as an antiferromagnet, and describes meson physics with a fixed baryon number background. We concentrate on uniform baryon number backgrounds (with the same baryon number on all sites), for which the ground state was extracted in an earlier work, and calculate the dispersion relations of the excitations. Two types of Goldstone boson emerge. The first, antiferromagnetic spin waves, obeys a linear dispersion relation. The others, ferromagnetic magnons, have energies that are quadratic in their momentum. These energies emerge only when fluctuations around the large-$N_c$ ground state are taken into account, along the lines of “order from disorder” in frustrated magnetic systems. Unlike other spectrum calculations in order from disorder, we employ the Euclidean path integral. For comparison, we also present a Hamiltonian calculation using a generalized Holstein-Primakoff transformation. The latter can only be constructed for a subset of the cases we consider.

We investigate the phase structure of lattice QCD for the general number of flavors in the parameter space of gauge coupling constant and quark mass, employing the one-plaquette gauge action and the standard Wilson quark action. Performing a series of simulations for the number of flavors $N_F=6\mathrm{}–360$ with degenerate-mass quarks, we find that when $N_F>~7$ there is a line of a bulk first order phase transition between the confined phase and a deconfined phase at a finite current quark mass in the strong coupling region and the intermediate coupling region. The massless quark line exists only in the deconfined phase. Based on these numerical results in the strong coupling limit and in the intermediate coupling region, we propose the following phase structure, depending on the number of flavors whose masses are less than ${\Lambda }_d$ which is the physical scale characterizing the phase transition in the weak coupling region: When $N_F>~17,$ there is only a trivial IR fixed point and therefore the theory in the continuum limit is free. On the other hand, when $16>~N_F>~7,$ there is a nontrivial IR fixed point and therefore the theory is nontrivial with anomalous dimensions, however, without quark confinement. Theories which satisfy both quark confinement and spontaneous chiral symmetry breaking in the continuum limit exist only for $N_F<~6.$

The high density effective theory recently introduced by Hong and Hsu to describe ultradense relativistic fermionic matter is used to calculate the tree-level forward scattering amplitude between two particles at the Fermi surface. While the direct term correctly reproduces that of the underlying gauge theory, the exchange term has the wrong sign. The physical consequences are discussed in the context of Landau’s theoretical description of the Fermi liquid.

We compute quark-antiquark pair production in the context of the color glass condensate model for central heavy-ion collisions. The calculation is performed analytically to leading order in the density of hard sources present in the projectiles, and is applicable to quarks with a mass large compared to the saturation momentum. The formulas derived in this paper are compared to expressions derived in the framework of collinearly factorized perturbative QCD and in $k_{\perp }$ factorization models. We comment on the breaking of $k_{\perp }$ factorization which occurs beyond leading order in our approach.

We present a theoretical estimation for the cross-section of exclusive two $\rho$-meson production in two photon collision when one of the initial photons is highly virtual. The compatibility of our analysis with recent experimental data obtained by the L3 Collaboration at (CERN) LEP is discussed. We show that these data prove the scaling behavior of the exclusive production amplitude. They are thus consistent with a partonic description of the exclusive process $\gamma {\gamma }^{*}\to {\rho }^0{\rho }^0$ when $Q^2\sim 2–20{\mathrm{GeV}}^2.$

The effect of anomalous right-handed top couplings on the photon polarization in $\overrightarrow{B}{K}_{\mathrm{res}}\gamma$ is investigated. It has recently been reported that the photon polarization can be measured through the up-down asymmetry of the photon direction relative to the subsequent $K_{\mathrm{res}}$ decay plane. We find that the anomalous couplings can severely affect the photon polarization without spoiling the well measured branching ratio of $\overrightarrow{B}{X}_s\gamma .$ Different features from other scenarios are also discussed.

Recently, several surprising experimental observations in the production of heavy quarkonium have been reported. In $e^{+}{e}^{-}$ annihilation at $\sqrt{s}=10.6\mathrm{}$ GeV, the Belle Collaboration finds that $J/\psi$ mesons are predominantly produced in association with an extra $\overline{c}c$ pair, with $\sigma {(e}^{+}{e}^{-}\to J/\psi \overline{c}c)/\sigma {(e}^{+}{e}^{-}\to J/\psi {X)=0.59\mathrm{}}_{-0.13}^{+0.15\mathrm{}}\pm 0.12,$ and the BaBar Collaboration reports that the produced $J/\psi$’s have mostly longitudinal polarization. In $\overline{p}p$ collisions at the Fermilab Tevatron, the CDF Collaboration reported an excess of $J/\psi$ and ${\psi }^{\prime }$ mesons at high $p_{\perp }$ over the perturbative QCD predictions; the nonperturbative approach of nonrelativistic QCD can accommodate the magnitude of the production cross section but not the observed experimental polarization of quarkonia. In this note we propose possible solutions to these puzzles and devise further experimental tests.

We investigate the $J/\psi +c+\overline{c}$ photoproduction in $e^{+}{e}^{-}$ collision at CERN LEP II energies. The physical motivations for this study are the following: (1) such a process was not considered in previous investigations of $J/\psi$ photoproduction in $e^{+}{e}^{-}$ interaction, and we show in this work that it is worthwhile to do so in order to make sound predictions for experimental comparison; (2) from recent Belle experiment results, the process with the same final states at the B factory has a theoretically yet unexplainable large fraction; hence it is interesting to see what may happen at other colliders; (3) the process can be measured with a high accuracy at the planned linear colliders; (4) it is necessary to take this process into consideration in elucidating the quarkonium production mechanism, especially in testing the universality of nonrelativistic QCD nonperturbative matrix elements. We find that the process concerned is really important at LEP experimental energies; within the theoretical uncertainties, it is of similar magnitude to the other color-singlet processes when the transverse momentum $p_T>1\mathrm{}\mathrm{GeV}.$ Nevertheless, to explain the recent DELPHI experimental result, the color-octet mechanism is still necessary, but with a shrunken contribution compared to previous analysis. It is found that the $J/\psi +c+\overline{c}$ photoproduction process cannot be mimicked by the simple fragmentation scheme.

We investigate the vacuum realignment for chiral symmetry breaking and color superconductivity at finite density in the Nambu–Jona-Lasinio model in a variational method. The treatment allows us to investigate the simultaneous formation of condensates in quark-antiquark as well as in diquark channels. The methodology involves an explicit construction of a variational ground state and minimization of the thermodynamic potential. Color and electric charge neutrality conditions are imposed through introduction of appropriate chemical potentials. Color and flavor dependent condensate functions are determined through minimization of the thermodynamic potential. The equation of state is calculated. Simultaneous existence of a mass gap and superconducting gap is seen in a small window of the quark chemical potential within the model when charge neutrality conditions are not imposed. Enforcing color and electric charge neutrality conditions gives rise to the existence of gapless superconducting modes depending upon the magnitude of the gap and the difference of the chemical potentials of the condensing quarks.

We take a fresh look at the analysis of resonance production by neutrinos. We consider three resonances $P_{33},P_{11}$ and $S_{11}$ with a detailed discussion of their form factors. The paper presents results for free proton and neutron targets and discusses the corrections which appear on nuclear targets. The Pauli suppression factor is derived in the Fermi gas model and shown to apply to resonance production. The importance of the various resonances is demonstrated with numerical calculations. The $\Delta$ resonance is described by two form factors and its differential cross sections are compared with experimental data. The article is self-contained and could be helpful to readers who wish to reproduce and use these cross sections.

The FORTE (Fast On-orbit Recording of Transient Events) satellite records bursts of electromagnetic waves arising from near the Earth’s surface in the radio frequency (rf) range of 30 to 300 MHz with a dual polarization antenna. We investigate the possible rf signature of ultrahigh energy cosmic-ray particles in the form of coherent Cherenkov radiation from cascades in ice. We calculate the sensitivity of the FORTE satellite to ultrahigh energy neutrino (UHE $\nu )$ fluxes at different energies beyond the Greisen-Zatsepin-Kuzmin cutoff. Some constraints on supersymmetry model parameters are also estimated due to the limits that FORTE sets on the UHE neutralino flux. The FORTE database consists of over 4 million recorded events to date, including in principle some events associated with UHE $\nu .$ We search for candidate FORTE events in the period from September 1997 to December 1999. The candidate production mechanism is via coherent VHF radiation from a UHE $\nu$ shower in the Greenland ice sheet. We demonstrate a high efficiency for selection against lightning and anthropogenic backgrounds. A single candidate out of several thousand raw triggers survives all cuts, and we set limits on the corresponding particle fluxes assuming this event represents our background level.

We study a combination of amplitudes for neutrino scattering that can isolate a (gauge-invariant) difference of chirality-preserving neutrino electroweak radii for ${\nu }_{\mu }$ and ${\nu }_{\tau }.$ This involves both photon and $Z_{\mu }$ exchange contributions. It is shown that the construction singles out the contributions of the hypercharge gauge field $B_{\mu }$ in the standard model. We comment on how gauge-dependent terms from the charge radii cancel with other terms in the relative electroweak radii.

Inclusive production of $D^{*\pm }$ (2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at DESY HERA using an integrated luminosity of 81.9 ${\mathrm{pb}}^{\mathrm{-}1}$. The decay channel $D^{*+}\to D^0{\pi }^{+}$ with $D^0\to K^{-}{\pi }^{+}$ and corresponding antiparticle decay were used to identify $D^{*}$ mesons. Differential $D^{*}$ cross sections with $1.5<\mathrm{}{Q}^2<1000\mathrm{}{\mathrm{GeV}}^2$ and $0.02<y<\mathrm{}0.7\mathrm{}$ in the kinematic region $1.5<\mathrm{}{p}_T{(D}^{*})<\mathrm{}15\mathrm{}\mathrm{GeV}$ and $|\eta {(D}^{*})|<1.5\mathrm{}$ are compared to different QCD calculations incorporating different parametrizations of the parton densities in the proton. The data show sensitivity to the gluon distribution in the proton and are reasonably well described by next-to-leading-order QCD with the ZEUS NLO QCD fit used as the input parton density in the proton. The observed cross section is extrapolated to the full kinematic region in $p_T{(D}^{*})$ and $\eta {(D}^{*})$ in order to determine the open-charm contribution, $F_2^{c\overline{c}}{(x,Q}^2),$ to the proton structure function, $F_2.$ Since, at low $Q^2,$ the uncertainties of the data are comparable to those from the QCD fit, the measured differential cross sections in y and $Q^2$ should be used in future fits to constrain the gluon density.

The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kamiokande-I was fit to the variations expected from active two-neutrino oscillations. The best fit in the large mixing angle solution has a mixing angle of ${\tan }^2\theta =0.55\mathrm{}$ and a mass squared difference of $\Delta m^2=6.3\mathrm{}\times {10}^{-5}{\mathrm{eV}}^2$ between the two neutrino mass eigenstates. The fitted day-night asymmetry of $-1.8\pm 1.6\left(\mathrm{stat}{)}_{-1.2}^{+1.3\mathrm{}}\right(\mathrm{syst})\%$ has improved statistical precision over previous measurements and agrees well with the expected asymmetry of $-2.1\%.$

We have studied the process $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}\gamma$ at a center-of-mass energy near the $\mathit{{\rm Y}}\mathrm{}\left(4S\right)\mathrm{}$ resonance for a ${\mu }^{+}{\mu }^{-}$ invariant mass range near the $J/\psi$ mass and measured the cross section $\sigma {(e}^{+}{e}^{-}\to J/\psi \overrightarrow{\gamma }{\mu }^{+}{\mu }^{-}\gamma ).\mathrm{}$ The data set, corresponding to an integrated luminosity of $88.4{\mathrm{fb}}^{-1},$ was collected using the BABAR detector at the SLAC PEP-II collider. From the measured cross section we extract the product $\Gamma (J/\overrightarrow{\psi }{e}^{+}{e}^{-})B(J/\overrightarrow{\psi }{\mu }^{+}{\mu }^{-})=0.330\mathrm{}\pm 0.008\pm 0.007\mathrm{keV}.$ Using the world averages for $B(J/\overrightarrow{\psi }{\mu }^{+}{\mu }^{-})$ and $B(J/\overrightarrow{\psi }{e}^{+}{e}^{-}),$ we derive the $J/\psi$ electronic and total widths: $\Gamma (J/\overrightarrow{\psi }{e}^{+}{e}^{-})=5.61\mathrm{}\pm 0.20\mathrm{keV}$ and $\Gamma =94.7\mathrm{}\pm 4.4\mathrm{keV}.$

We present an exactly soluble charged wormhole model in two dimensions by adding infalling chiral fermions on the static wormhole. The infalling energy due to the infalling charged matter requires the classical backreaction of the geometry, which is solved by taking into account the nontrivial nonchiral exotic energy. Finally, we obtain the exact expression for the size of the throat depending on the total amount of the infalling net energy and discuss the interesting transition from the anti–de Sitter spacetime to the wormhole geometry.

We derive a boundary action of $N=2\mathrm{}$ super-Liouville theory which preserves both $N=2\mathrm{}$ supersymmetry and conformal symmetry by imposing explicitly $T=\overline{T}$ and $G=\overline{G}.$ The resulting boundary action shows a new duality symmetry.

Nonuniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a nontrivial hair of the black strings. From the brane point of view, the black string appears as the deformed dilatonic black hole which becomes a dilatonic black hole in the single brane limit and reduces to the Reissner-Nordström black hole in the close limit of two-branes. The stability of solutions is demonstrated using catastrophe theory. From the bulk point of view, the black strings are proved to be nonuniform. Nevertheless, the zeroth law of black hole thermodynamics still holds.

The presence of a bulk viscosity for the cosmic fluid on a single Randall-Sundrum brane is considered. The spatial curvature is assumed to be zero. The five-dimensional Friedmann equation is derived, together with the energy conservation equation for the viscous fluid. These governing equations are solved for some special cases: (i) in the low-energy limit when the matter energy density is small compared with brane tension; (ii) for a matter-dominated universe, and (iii) for a radiation-dominated universe. Rough numerical estimates, for the extreme case when the universe is at its Planck time, indicate that the viscous effect can be significant.

It has been suggested that the observed pulsar velocities are caused by an asymmetric neutrino emission from a hot neutron star during the first seconds after the supernova collapse. We calculate the magnitude of gravitational waves produced by the asymmetries in the emission of neutrinos. The resulting periodic gravitational waves may be detectable by LIGO and LISA in the event of a nearby supernova explosion.