We are reporting an improved determination of the electroweak mixing angle sin 2 Θ w from the ratio of ν μ e to ν μ e scattering cross sections. The CHARM II detector was exposed to neutrino and antineutrino wide band beams at the 450 GeV CERN SPS. Including new data collected in 1989 we have obtained 1316 ± 56 ν μ e and 1453 ± 62 ν μ e events. From the ratio of the visible cross sections we determined sin 2 Θ 0 =0.239 ± 0.009(stat) ± 0.007(syst) without radiative corrections and g V e g A e =0.047 ± 0.046 . Combining this last result with recent results on g A e at LEP we obtain g V e = −0.023 ± 0.023.
Systematic error presented includes error from flux normalization 'F'=1.030+- 0.022, no detaled description of the other sources and of the combination pr ocedure.. 'F'.
Without radiative corrections, systematic error combined in quadrature fromconponents listed under SYSTEMATICS.
With radiative corrections as defined by Marciano-Sirlin scheme, see Phys.Rev.D22(1980)2695, Phys.Rev.Lett.46(1981)163, Phys.Rev.D29(1984)945, Phys.Rev.D31(1985)213E, Nucl.Phys.B217(1983)84. CENTRAL VALUE IS FOR M(TOP)=100 GEV, M(HIGGS)=100 GEV.
The polarization PΞ− of Ξ− hyperons produced by 800-GeV protons has been measured for xF from 0.3 to 0.7 and pT from 0.5 to 1.5 GeV/c. PΞ− has a pT dependence similar to that of the Λ but has a different xF behavior. Also, an energy dependence of PΞ− has been observed.
1.3 mv production angle was horizontal. Others are vertical.
The first spin-transfer observables for the πd→pp reaction have been measured at a number of energies spanning the Δ resonance in this system. These parameters correspond to KSL and KSS of the pp→dπ reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.
No description provided.
No description provided.
Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004<x<0.8 and 0.4<Q2<190 GeV2, together with the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x)-F2n(x). The value of the Gottfried sum F(F2p-F2n)dx/x=0.240±0.016 is below the quark-parton-model expectation of 1/3.
No description provided.
The production of π±,K±,p has been measured in p+Be and p+Au collisions for comparison with central Si+Au collisions. The inverse slope parameters T0 obtained by an exponential fit to the invariant cross sections in transverse mass are found to be, T0p,K+,ππ∼140–160 MeV in p+A collisions, whereas in central Si+Au collisions, T0p,K+∼200–220 MeV >T0ππ∼140–160 MeV at midrapidity. The π± and K+ distributions are shifted backwards in p+Au compared with p+Be. A gradual increase of (dn/dy)K+ per projectile nucleon is observed from p+Be to p+Au to central Si+Au collisions, while pions show no significant increase.
No description provided.
No description provided.
No description provided.
We report on a systematic study of midrapidity transverse energy production and forward energy flow in interactions of16O and32S projectiles with S, Cu, Ag and Au targets at 60 and 200 GeV/nucleon. The variation of the shape of theET distributions with target and projectile mass can be understood from collision geometry. AverageET values determined for central collisions show an increasing stopping power for heavier target nuclei. A higher relative stopping is observed at 60 GeV/nucleon than at 200 GeV/nucleon. Bjorken estimates of the energy density reach approximately 3 GeV/fm3 in highET events at 200 GeV/nucleon with16O and32S projectiles. The systematics of the data and the shapes ofET and pseudorapidity distributions are well described by the Lund model Fritiof.
No description provided.
No description provided.
No description provided.
The production of μ−e+ dileptons by muon neutrinos is studied in a high-statistics bubble-chamber experiment. The experiment consisted of exposing the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mix to a wideband neutrino beam. In a total sample of 146 700±11 700 charged-current interactions, 461 events with an e+(Pe+>300 MeV/c) and a μ− are observed. The rate for μ−e+ dilepton production in measured to be (0.42±0.06)%. The energy dependence of this rate is presented. The kinematic distributions for the μ−e+ events are consistent with charm production and subsequent semileptonic decay. A total of 60 KS0 and 31 Λ0 decays were observed in the μ−e+ event sample. The measured rates for neutral-strange-particle production are 0.78±0.12 K0K¯0's and 0.19±0.04 Λ0's per μ−e+ event. Finally, rates for Λc+, D0, and D+ production in charged-current νμ interactions are derived. They are found to be (4−2+10)%, (1.7−0.7+0.5)%, and (1.3−0.5+0.4)%, respectively.
No description provided.
No description provided.
No description provided.
We have measured the polarization of D*, the energy dependence of the polarization, and the spin-density matrix of D* in e+e− annihilation at a center-of-mass energy of 29 GeV using the Time Projection Chamber detector at the SLAC storage ring PEP. In 147 pb−1 of data we see no strong evidence for polarization, alignment, or final-state interactions in this fragmentation process.
Polarization is the factor alpha(z) in the expression d width (D*-->D pi)/domega = C(1+alpha(z)cos(theta)**2).
Spin density matrices for D* --> D0 pi+.
We present preliminary results on the measurement of a variety of exclusive hadron interactions at center of mass scattering angles of 90°. Data are also presented which show the relative transparency of nuclei to πp and pp elastic scattering in this kinematic range.
No description provided.
No description provided.
No description provided.
A measurement of Δσ L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. Data were taken for five energies between 500 and 800 MeV, with statistical errors of ≈ 1.5 mb and an estimated normalization error of 6%. The data, combined with other results, show some evidence for an elastic I =0 spin-singlet resonance with mass ∼ 2213 MeV and width ∼ 74 MeV, or a coupled-triplet resonance with similar mass and width.
SIG(C=PARALLEL)-SIG(C=ANTIPARALLEL) means the difference in the total crosssection with initial parallel and antiparallel longitudinal spin states. The I0 means I=0, these values were found using interpolated Delta(sigma(pp)) data.
Forum