17975331
ZN phases in hot gauge theories.
We argue that the {ital Z}{sub {ital N}} phases of hot gauge theories cannot be realized as a real system with a Hermitian density matrix.
119850463
Charged Pion Photoproduction
We extracted the differential cross section for the γn→π−p process from a deuterium target using the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center‐of‐mass (c.m.) angles (θc.m.) between 50° and 115°. We confirm a previous indication of a broad enhancement around a c.m. energy (s) of 2.1 GeV at θc.m. = 90° in the scaled differential cross section, s7dσdt and a rapid fall‐off in a center‐of‐mass energy region of about 400 MeV following the enhancement. Our data show an angular dependence of this enhancement as the suggested scaling region is approached for θc.m. from 70° to 105°.
44727684
BRST quantization of topological field theory.
The canonical quantization of the topological field-theory model {Sigma}, proposed by Horowitz, is examined through the Becchi-Rouet-Stora-Tyutin approach. With this approach we have a manifestly covariant description of a certain class of topological quantum field theories. However, if {ital M} in the present model is any orientable four-dimensional manifold, one would end up with different theories when different polarizations are chosen. Therefore a restriction {ital M}={ital R}{sup 1}{times}{Sigma}, as pointed out by Horowitz, is required for consistency.
119207670
PHASE-RESOLVED SPECTRAL ANALYSIS OF 4U 1901+03 DURING ITS OUTBURST
The high-mass X-ray binary 4U 1901+03 is reported to have a pulse profile evolving with the X-ray luminosity and energy during its outburst in 2003 February-July: the pulse peak changed from double to single along with the decreasing luminosity. We have carried out a detailed analysis on the contemporary phase-resolved energy spectrum of 4U 1901+03 as observed by the Rossi X-ray Timing Explorer. We find that the spectra are phase dependent. At the beginning of the outburst, the maximum of the optical depth for Compton scattering is near the major phase peak. During the decay of the outburst, the optical depth has the maximum away from the main peak of the pulse profile. For each observation, Fe Kα emission line is detected in the phase-resolved spectra, and its flux is constant across the pulse phases. This suggests that the origin of the Fe emission is from the accretion disk, not the surface of the neutron star.
16855657
Critical statistical charge for anyonic superconductivity.
We examine a criterion for the anyonic superconductivity at zero temperature in Abelian matter-coupled Chern-Simons gauge-field theories in three dimensions. By solving the Dyson-Schwinger equations, we obtain a critical value of the statistical charge for the superconducting phase in a massless fermion-Chern-Simons model. {copyright} {ital 1996 The American Physical Society.}
28535306
Implications of a cosmological constant varying as R-2.
We advocate the possibility that the (effective) cosmological constant {Lambda} varies in time as {ital R}{sup {minus}2}, {ital R} being the scale factor of our expanding Universe. This behavior can be obtained under some simple and general assumptions in conformity with quantum cosmology. After pointing out several advantages worth noticing, we show that such a time-varying {Lambda} leads to no conflict with existing observations. However, it does change the predictions of the standard cosmology in the matter-dominated epoch and alleviates some problems in reconciling observations with the inflationary scenario. In particular, this medium'' time variation of {Lambda} leads to creation of matter with a rate at present which is comparable to that in the steady-state cosmology.
28164273
General theory of quantum statistics with internal degrees of freedom in two dimensions.
The general theory of θ statistics with internal degrees of freedom is presented. The intrinsic parts of wave functions are expressed by means of the irreducible representations of the quantum group SU(2,q) with q=e −iθ . We show that the violation of P or T reflection symmetry is involved in two kinds of coproduct for constructing these representations
22668459
Chiral-symmetry breaking in two-dimensional SU(2) QCD with fermions.
We have studied the chiral symmetry of SU(2) Yang-Mills theory coupled to an unflavored fermion on a two-dimensional lattice using a hybrid algorithm based on the projector hamiltonian Monte-Carlo method. We found chiral symmetry breaking in the continuum limit. The theory is predicted to reside in only one phase in which chiral symmetry is broken.
46325047
Helicity decomposition for inclusive J/ psi production.
We present a general method for calculating inclusive cross sections for the production of heavy quarkonium states with definite polarization within the NRQCD factorization approach. Cross sections for polarized production can involve additional matrix elements that do not contribute to cross sections for unpolarized production. They can also include interference terms between parton processes that produce {ital Q{bar Q}} pairs with different total angular momentum. The interference terms cancel upon summing over polarizations. Our method can be generalized to {ital N} dimensions and is, therefore, compatible with the use of dimensional regularization to calculate radiative corrections. We illustrate the method by applying it to the production of {ital J}/{psi} via the parton processes {ital q{bar q}}{r_arrow}{ital c{bar c}} and {ital gg}{r_arrow}{ital c{bar c}}. {copyright} {ital 1996 The American Physical Society.}
36892867
Perturbative QCD predictions for the fragmentation functions of the P- wave mesons with two heavy quarks.
The fragmentation functions for the heavy mesons of [ital S] and [ital P] waves are calculated in the framework of perturbative QCD and the nonrelativistic quark model. The results are manifestly process independent. As applications, the production ratios for [ital P]-wave [ital [bar b]c] mesons to the [ital b[bar b]] production at high energy colliders are predicted. The spin dependence of the fragmentation functions for various states is discussed and the predicted results for the [ital D] ([ital D][sup *]) mesons are consistent with the recent experimental data.
40500552
Measurement of the bottom-quark production cross section in 800 GeV/c proton-gold collisions.
Using a silicon-microstrip detector array to identify secondary vertices, we have observed {ital b}{r_arrow}{ital J}/{psi}{r_arrow}{mu}{sup +}{mu}{sup {minus}} decays in 800 GeV/{ital c} proton-gold interactions. The doubly differential cross section for {ital J}/{psi} mesons originating from {ital b}-quark decays, assuming linear dependence on nucleon number, is {ital d}{sup 2}{sigma}/{ital dx}{sub {ital Fdp}}{sup 2}{sub {ital T}}=107{plus_minus}28{plus_minus}19/nucleon at {ital x}{sub {ital F}}=0.05 and {ital p}{sub {ital T}}=1GeV/{ital c}. This measurement is compared to next-to-leading-order QCD predictions. The integrated {ital b}-quark production cross section, obtained by extrapolation over all {ital x}{sub {ital F}} and {ital p}{sub {ital T}}, is {sigma}({ital pN}{r_arrow}{ital bb}{ovr bar}+{ital X})=5.7{plus_minus}1.5{plus_minus}1.3 nb/nucleon.