32857126
Polarization of Xi - and Omega - hyperons produced from neutral beams.
120389291
Study of quark flow in exclusive reactions at 90 degrees in the center of mass (AGS E838)
We report a study of quark flow in 20 exclusive reactions measured at Brookhaven National Laboratory’s AGS with a beam momentum of 5.9 GeV/c at 90° in the center of mass. This experiment confirms the strong quark flow reaction mechanism dependence of two‐body hadron scattering at large angles seen at 9.9 GeV/c. Large differences in cross sections for different reactions are consistent with the dominance of quark interchange in these 90° reactions, and indicate that pure gluon exchange and quark/antiquark annihilation diagrams are less important.
125996066
A MULTIKILOTON DETECTOR TO CONDUCT A SENSITIVE SEARCH FOR NUCLEON DECAY
120960559
New limit on magnetic monopole flux
The underground Soudan-1 nucleon decay experiment can measure the velocities of slowly moving particles if they can be detected by ionization at a level 0.5 times that of a relativistic muon. Magnetic monopoles predicted by grand unified theories should satisfy this condition if their velocities are greater than 10/sup -3/c. During a live time of 0.41 yr, no candidate has been observed, implying a 90%- confidence-level limit on the flux of such objects of <4.1 x 10/sup -13/ cm/sup -2/ sr/sup -1/ s/sup -1/ for velocities between 10/sup -3/c and 10/sup -2/c.
45078944
Measurements of production polarization and decay asymmetry for Xi - hyperons.
45066347
HARD QUARK-QUARK SCATTERING WITH EXCLUSIVE REACTIONS*
We have begun a program designed to study hard quark-quark scattering with exclusive reactions, focusing on quasi-elastic two-body reactions with all possible quark flavor exchanges. Examples are ..pi../sup -/p ..-->.. ..pi../sup -/p, rho/sup -/p, ..pi../sup +/..delta../sup -/, K/sup +/..sigma../sup -/, or K..lambda... Of the two-body exclusives, only elastic scattering had been measured at such large t previous to our experiment. By comparing the relative importance of different final states, the energy dependence of the production ratios of these states, the prominence of resonances such as rho/sup -/ over background in this region, and measuring polarizations where accessible, we have collected a large body of data on hard scattering in a completely new domain. Previously, essential all short distance QCD tests have been for inclusive processes. We have taken data with both negative and positive incident beam at 10 GeV/c on a hydrogen target and will present the first results, for ..pi../sup -/p ..-->.. ..pi../sup -/p and rho/sup -/p at THETA/sub cm/ = 90/sup 0/, -t = 9 GeV/sup 2//c/sup 2/. The apparatus consists of a magnetic spectrometer, with Cerenkov particle identification, which selects stable charged particles (protons in this case) at high momentum near 90/sup 0/ in the center-of-mass. Amore » large aperture array of PWCs observes the recoil particle or charged decay products. Cross sections are extremely low, approximately a 1 nb/(GeV/c)/sup 2/ for elastic scattering. We will report on a sample of more than 1000 ..pi../sup -/p elastic events, and on rho/sup -/p, where the rho/sup -/ decay distribution was observed. We find a surprisingly large rho/sup -/p cross section in this large momentum transfer region, with rho/sup -/p about half the elastic cross section, and a striking spin alignment of the rho/sup -/.« less
21290231
Overrelaxation and mode coupling in sigma models.
An exact overrelaxation algorithm for nonlinear \ensuremath{\sigma} models is presented and practically implemented. Using a new method of analysis the mode-mode coupling mechanism underlying overrelaxation is clearly exhibited. In one dimension our numerical results provide evidence that the critical exponent z is equal to unity.
44295094
Hadron spectrum in QCD with valence Wilson fermions and dynamical staggered fermions at 6/g2=5.6.
We present an analysis of hadronic spectroscopy for Wilson valence quarks with dynamical staggered fermions at a lattice coupling 6/{ital g}{sup 2}={beta}=5.6 at a sea-quark mass of {ital am}{sub {ital q}}=0.01 and 0.025, and of Wilson valence quarks in the quenched approximation at {beta}=5.85 and 5.95, both on 16{sup 3}{times}32 lattices. We make comparisons with our previous results with dynamical staggered fermions at the same parameter values but on 16{sup 4} lattices doubled in the temporal direction.
39094885
Monte Carlo renormalization-group investigation of the two-dimensional O(4) sigma model.
An improved Monte Carlo renormalization-group method is used to determine the ..beta.. function of the two-dimensional O(4) sigma model. While for (inverse) couplings ..beta..approx. >2.2 one obtains agreement with asymptotic scaling according to asymptotic freedom, one can see deviations from it at smaller couplings. They are, however, consistent with the behavior of the correlation length, indicating ''scaling'' according to the full ..beta.. function. These results contradict recent claims that the model has a critical point at finite coupling.
42339487
B spectroscopy from NRQCD with dynamical fermions.
We present a lattice investigation, partially including the effects of dynamical quarks, of the heavy-light mesons using NRQCD for the heavy quark and the Wilson action for the light quark. We perform an extensive calculation of the spectrum employing a multistate, multiexponential fitting analysis which enables us to extract the 2{ital S}-1{ital S} splitting as well as the {sup 1}{ital P}{sub 1}-{ital {bar S}} and hyperfine splittings. The Wilson action introduces a large systematic error into the calculation, and within this uncertainty we obtain agreement with experiment. We perform a comprehensive calculation of the heavy-light meson mass, investigating three methods and their range of validity. The agreement found between these methods confirms that Lorentz invariance can be restored at this order in NRQCD by a constant shift to all masses. We calculated spectroscopic quantities over a wide range in heavy quark mass and are able to perform a detailed investigation of heavy quark symmetry around the {ital b} quark mass. In particular, we extract the nonperturbative coefficients of terms in the heavy quark expansion of the meson binding energy. We demonstrate the importance of using tadpole-improved operators in such a calculation. {copyright} {ital 1996 The American Physical Society.}
35737837
Hadron thermodynamics with Wilson quarks.
We study hadron thermodynamics with Wilson quarks. The crossover curve between the high- and low-temperature phases is determined as a function of gauge coupling and hopping parameter on 8{sup 3}{times}4 lattices. Screening lengths are calculated in the vicinity of the crossover region, and meson masses are calculated along the crossover curve on 8{sup 2}{times}16{times}4 and 8{sup 3}{times}16 lattices, respectively.