6958720
Precise measurement of the Xi - magnetic moment.
With 4.36{times}10{sup 6} events, spin precession in a magnetic field has been used to measure the magnetic moment of the {Xi}{sup {minus}} hyperon as {minus}0.6505{plus minus}0.0025 nuclear magnetons.
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.
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
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.
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
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.
14517731
QCD beta function with two flavors of dynamical Wilson fermions.
We test the asymptotic scaling behavior of state-of-the-art simulations of QCD with two flavors of light Wilson fermions. This is done by matching {pi} and {rho} masses on lattices of size 16{sup 3}{times}32 and 8{sup 3}{times}16. We find that at {beta}=6/{ital g}{sup 2}=5.3 matching is not possible over a range extending down to {beta}=3.5. The large lattice data at {beta}=5.5 matches the small lattice values at {beta}=4.9(1) leading to a shift {Delta}{beta}=0.6(1), considerably larger than the perturbative prediction of 0.45. In both cases we conclude that the simulations are very far from the asymptotic scaling region. {copyright} {ital 1996 The American Physical Society.}
33991730
More on the two-dimensional O(4) sigma model.
New measurements of the correlation length and magnetic susceptibility for the two-dimensional O(4) sigma model are reported. They corroborate the conclusion from a recent Monte Carlo renormalization-group investigation that the standard, asymptotic-freedom picture holds for this model. A finite-size scaling analysis also supports this conclusion.
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.