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.
119237592
The 7-channel FIR HCN interferometer on J-TEXT tokamak
A seven-channel far-infrared hydrogen cyanide (HCN) laser interferometer has been established aiming to provide the line integrated plasma density for the J-TEXT experimental scenarios. A continuous wave glow discharge HCN laser designed with a cavity length 3.4 m is used as the laser source with a wavelength of 337 μm and an output power up to 100 mW. The system is configured as a Mach-Zehnder type interferometer. Phase modulation is achieved by a rotating grating, with a modulation frequency of 10 kHz which corresponds to the temporal resolution of 0.1 ms. The beat signal is detected by TGS detector. The phase shift induced by the plasma is derived by the comparator with a phase sensitivity of 0.06 fringe. The experimental results measured by the J-TEXT interferometer are presented in details. In addition, the inversed electron density profile done by a conventional approach is also given. The kinematic viscosity of dimethyl silicone and vibration control is key issues for the system performance. The laser power stability under different kinematic viscosity of silicone oil is presented. A visible improvement of measured result on vibration reduction is shown in the paper.
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.
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°.
17527105
Four-Fermion theory and the conformal bootstrap
We employ the conformal bootstrap to re-examine the problem of finding the critical behavior of four-fermion theory at its strong coupling fixed point. Existence of a solution of the bootstrap equations indicates self-consistency of the assumption that, in space-time dimensions less than four, the renormalization group flow of the coupling constant of a four-fermion interaction has a nontrivial fixed point which is generally out of the perturbative regime. We exploit the hypothesis of conformal invariance at this fixed point to reduce the set of the Schwinger-Dyson bootstrap equations for four-fermion theory to three equations which determine the scale dimension of the fermion field ψ, the scale dimension of the composite field ψψ and the critical value of the Yukawa coupling constant. We solve the equations assuming this critical value to be small. We show that this solution recovers the fixed point for the four-fermion interaction with N-component fermions in the limit of large N at (Euclidean) dimension d between two and four. We perform a detailed analysis of the 1/N-expansion in d = 3 and demonstrate full agreement with the conformal bootstrap. We argue that this is a useful starting point for more sophisticated computation of the critical indices.
119238888
Mass spectrum of heavy quarkonium hybrids
A bstractWe have extended the calculation of the correlation functions of heavy quarkonium hybrid operators with various JPC quantum numbers to include QCD condensates up to dimension six. In contrast to previous analyses which were unable to optimize the QCD sum-rules for certain JPC, recent work has shown that inclusion of dimension six condensates stabilizes the hybrid sum-rules and permits reliable mass predictions. In this work we have investigated the effects of the dimension six condensates on the remaining channels. After performing the QCD sum-rule analysis, we update the mass spectra of charmonium and bottomonium hybrids with exotic and non-exotic quantum numbers. We identify that the negative-parity states with JPC = (0, 1, 2)−+, 1−− form the lightest hybrid supermultiplet while the positive-parity states with JPC = (0, 1)+−, (0, 1, 2)++ belong to a heavier hybrid supermultiplet, confirming the supermultiplet structure found in other approaches. The hybrid with JPC = 0−− has a much higher mass which may suggest a different excitation of the gluonic field compared to other channels. In agreement with previous results, we find that the JPC = 1++ charmonium hybrid is substantially heavier than the X(3872), which seems to preclude a pure charmonium hybrid interpretation for this state.
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.
33113460
Studies of xi (2230) in J/ psi radiative decays.
2423491
Comparative study of the hadronic production of Bc mesons.
A comparative study of the full {alpha}{sup 4}{sub {ital s}} perturbative QCD calculation of the hadronic production of the {ital B}{sub {ital c}} and {ital B}{sub {ital c}}{sup {asterisk}} mesons and the fragmentation approximation is presented. We examined the various subprocesses in detail and the distribution {ital C}({ital z}), where {ital z} is twice the fraction of the {ital B}{sub {ital c}} or {ital B}{sub {ital c}}{sup {asterisk}} meson energy in the center of mass of the subprocess, which proved insightful and revealed the importance of certain nonfragmentation contributions. We concluded that the condition for the applicability of the fragmentation approximation in hadronic collisions is that the transverse momentum {ital P}{sub {ital T}} of the produced {ital B}{sub {ital c}} and {ital B}{sub {ital c}}{sup {asterisk}} be much larger than the mass of the {ital B}{sub {ital c}} meson: i.e., {ital P}{sub {ital T}}{gt}{ital M}{sub {ital B}{sub {ital c}}}. Numerical results for the cross sections at the Fermilab Tevatron are also presented using updated parton distribution functions with various kinematic cuts. {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.
43756291
Top quark search with the D0 1992-1993 data sample.
We present results on the search for the top quark in {ital p{bar p}} collisions at {radical}{ital s} =1.8 TeV with an integrated luminosity of 13.5{plus_minus}1.6 pb{sup {minus}1}. We have considered {ital t{bar t}} production in the standard model using electron and muon dilepton decay channels ({ital t{bar t}}{r_arrow}{ital e}{mu}+jets, {ital ee}+jets, and {mu}{mu}+jets) and single-lepton decay channels ({ital t{bar t}}{r_arrow}{ital e}+jets and {mu}+jets) with and without tagging of {ital b} quark jets. An analysis of these data optimized for top quark masses below 140 GeV/{ital c}{sup 2} gives a lower top quark mass limit of 128 GeV/{ital c}{sup 2}. An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8{plus_minus}0.9. If we assume that the excess is due to {ital t{bar t}} production, and assuming a top quark mass of 180 GeV/{ital c}{sup 2}, we obtain a cross section of 8.2{plus_minus}5.1 pb.