45078944
Measurements of production polarization and decay asymmetry for Xi - hyperons.
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.
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.
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
125996066
A MULTIKILOTON DETECTOR TO CONDUCT A SENSITIVE SEARCH FOR NUCLEON DECAY
122693257
Inclusive Production of Lambda0 Hyperons by 300-GeV Protons: A-Dependence
Inclusive production of ${\ensuremath{\Lambda}}^{0}$ hyperons by 300-GeV protons has been measured at fixed production angles in the laboratory between 0 and 9 mrad and laboratory momenta from 65 to 300 GeV/c. Three different solid targets were used: beryllium, copper, and lead. The $A$ dependence of the data is suggestive of a collision model in which the hadron loses energy and gains transverse momentum as it leaves the nucleus. The experimental results are compared to such a model, and the implications are discussed.
44999335
Glueballs and topology in lattice QCD with two light flavors.
We obtain estimates of the lightest glueball masses, the string tension, and the topological susceptibility in an exploratory study of QCD with two light flavors of quarks. Our calculations are performed at {beta}=5.6 with staggered quark masses {ital m}{sub {ital q}}=0.010 and 0.025 and on lattices ranging from 12{sup 4} to 16{sup 4}. Our estimates suggest that, just as in the pure gauge theory, the 0{sup ++} is the lightest glueball with the 2{sup ++} about 50% heavier. Our {ital m}{sub {ital q}}=0.01 results predict a 0{sup ++} glueball mass of about 1.6 times the {rho} mass and the square root of the string tension of about 0.48 times the {rho} mass, which is surprisingly close to the usual phenomenologically motivated estimates of around 0.55. Our value of the topological susceptibility at {ital m}{sub {ital q}}=0.01 is consistent with the prediction, to {ital O}({ital m}{sub {ital q}}) of the standard anomalous Ward identity. However, the variation of this susceptibility between {ital m}{sub {ital q}}=0.01 and {ital m}{sub {ital q}}=0.025 is weaker than the linear dependence one expects at small {ital m}{sub {ital q}} in the broken-chiral-symmetry phase of QCD.
44737686
Hadron spectrum and matrix elements in QCD with dynamical Wilson fermions at 6/g2=5.3.
We present results of a lattice simulation of quantum chromodynamics with two degenerate flavors of dynamic Wilson fermions at $\frac{6}{{g}^{2}}=5.3$ at each of two dynamical fermion hopping parameters $\ensuremath{\kappa}=0.1670 \mathrm{and} 0.1675$ corresponding to pion masses in lattice units of about 0.45 and 0.31. The simulations include three other values of valence quark mass, in addition to the dynamical quarks. We present calculations of masses and of the decay constants of vector mesons and of pseudoscalars, including the $D$-meson decay constant. The effects of sea quarks on matrix elements and spectroscopy are small.
37516641
Simple hadronic matrix elements with Wilson valence quarks and dynamical staggered fermions at 6/g2=5.6.
We have measured some simple matrix elements for pseudoscalar and vector mesons made of Wilson valance quarks and staggered sea quarks at [beta]=5.6 at sea quark masses [ital am][sub [ital q]]=0.01 and 0.025. Our measurements include the decay constants of pseudoscalars (including [ital f][sub [ital D]]), the wave function at the origin (or decay constant) of vector mesons, and the calculation of quark masses from current algebra. The effects of sea quarks on the simulations are small. We make comparisons to quenched simulations at similar values of the lattice spacing (1/[ital a][congruent]2 GeV).
39568649
Evolution of the density parameter in multidimensional cosmology.
Inflation as a dynamical effect of extra dimensions is discussed from the viewpoint of the evolution of the parameters Ω and q in the physical space. By reducing the dynamics of the models FLRW (k=±1)×T D (T D =S 1 ×... ×S 1 ) and FLRW (k=0)×S D , where FLRW denotes Friedmann, Lemaitre, Robertson, and Walker, to two dimensions it is shown that inflation need not imply Ω≃ 1 for the present time, i.e., that it does not solve the flatness problem. The energy-momentum tensor of the form T υ μ =(ρ,mρ,mρ,mρ,nρ,..., nρ) is assumed
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.}