We have measured the polarization of Λ and Λ hyperons produced by 800 GeV protons on a Be target at a fixed targeting angle of 4.8 mrad. Comparison with previous data at 400 GeV production energy and twice the targeting angle shows no significant energy dependence for the Λ polarization. This is in striking contrast to the energy dependence found for σ + and Ξ − polarizations. We find no evidence for Λ polarization at 800 GeV.
Errors are combined statistics and systematics.
No description provided.
The excitation of theΔ resonance is observed in proton collisions on C, Nb and Pb targets at 0.8 and 1.6 GeV incident energies. The mass E0 and widthΓ of the resonance are determined from the invariant mass spectra of correlated (p, π±)-pairs in the final state of the collision: The mass E0 is smaller than that of the free resonance, however by comparing to intra-nuclear cascade calculations, this reduction is traced back to the effects of Fermi motion, NN scattering and pion reabsorption in nuclear matter.
WITHIN THE DETECTORS ACCEPTANCE RESULTS.
WITHIN THE DETECTORS ACCEPTANCE RESULTS.
WITHIN THE DETECTORS ACCEPTANCE RESULTS.
Charged pions and light nuclei (p, d, t, He3, and He4) have been measured in the interaction of proton beams with C, Nb, and Pb targets at 0.8 and 1.6 GeV incident energies, using a large solid angle detector. From slices on the multiplicity of protonlike particles (free protons and protons bound in light fragments), the events have been sorted out into two classes corresponding to more peripheral and more central collisions. For each class of events, the mean value and the dispersion of the π+ and π− multiplicity distributions have been studied as a function of target mass and incident energy. Comparisons to the Liege intranuclear cascade predictions exhibit some discrepancies which are discussed.
OBSERVATION OF THE PROTONLIKE MULTIPLICITY.
OBSERVATION OF PERCENTAGE OF THE PROTONLIKE MULTIPLICITY REACTIONS.
OBSERVATION OF PERCENTAGE OF THE PROTONLIKE MULTIPLICITY REACTIONS.
An angular distribution of negative pions produced on 15 N, leading to the ground state of 15 O, has been measured via the (e, π − )-reaction at E e ≈ 170 MeV. Using virtual photon theory, single-differential cross sections are extracted from the measured double-differential cross sections. The measured data is in good agreement with theoretical calculations in the DWIA model. A clear signature of nuclear EO excitation is found in contrast to previous experiments in a similar reaction on 13 C.
No description provided.
We measured the differences in R=σLσT and the cross-section ratio σAσD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤5 (Gev/c)2. Our results for RA−RD are consistent with zero for all x and Q2, indicating that possible contributions to R from nuclear higher-twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q2, are now in agreement.
No description provided.
No description provided.
No description provided.
A search for the 0 + → 2 + neutrinoless double-beta decay of 76 Ge into the first excited state of 76 Se has been carried out using a coincidence technique between Ge and NaI detectors. Since the expected number of counts is very small and mixed with a continuous background of natural radioactivity, special care has been taken to maintain the good energy resolution of the detectors. As a consequence, the experimental data display, after 6207 h statistical time, a coincidence signal of 19.3 ± 5.8 counts, between an energy deposition of 1484.0 ± 0.3 keV in the Ge detectors and 561 ± 10 keV in the NaI detectors. Both Ge and NaI energies are within the experimental errors, compatible with the expected values. No other unidentified coincidence signal has been found in the full Ge-NaI energy matrix, and no similar γγ cascade has been found within our background. Even if the low statistics does not completely rule out the possibility of a statistical fluctuation, this result should encourage further experiments with improved sensitivities.
SE76* IS IN 2+ EXGITED STATE.
An experimental study of $\omega$ photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The $\gamma p\to\omega p$ differential cross sections are measured from threshold to the incident-photon energy $E_\gamma=1.40$ GeV ($W=1.87$ GeV for the center-of-mass energy) with 15-MeV binning in $E_\gamma$ and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the $\omega N$ scattering length $\alpha_{\omega p}$ is provided.
Total cross section as a function of c.m. energy W.
Differential cross section at W= 1.7245 GeV
Differential cross section at W= 1.7319 GeV
We present the first measurement of the Q^2-dependence of the neutron spin structure function g_2^n at five kinematic points covering 0.57 (GeV/c)^2 <= Q^2 <= 1.34 (GeV/c)^2 at x~0.2. Though the naive quark-parton model predicts g_2=0, non-zero values for g_2 occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses or orbital angular momentum. When scattering from a non-interacting quark, $g_2^n$ can be predicted using next-to-leading order fits to world data for g_1^n. Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q^2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g_1^n are consistent with next-to-leading order fits to world data.
Measured values of G1N ang G2N.
The production of the Lambda and Sigma0 hyperons has been measured via the pp->pK+Lambda / Sigma0 reaction at the internal COSY-11 facility in the excess energy range between 14 and 60 MeV. The transition of the Lambda/Sigma0 cross section ratio from about 28 at Q<=13 MeV to the high energy level of about 2.5 is covered by the data showing a strong decrease of the ratio between 10 and 20 MeV excess energy. Effects from the final state interactions in the p-Sigma0 channel seem to be much smaller compared to the p-Lambda one. Estimates of the effective range parameters are given for the N-Lambda and the N-Sigma systems.
Cross section for LAMBDA production.. Statistical errors only.
Cross section for SIGMA0 production.. Statistical errors only.
Energy dependence of the LAMBDA/SIGMA0 ratio.
Neutron-production double-differential cross sections for 870MeVπ+ and π− and 2.1GeVπ+ mesons incident on iron and lead targets were measured with NE213 liquid scintillators by time-of-flight technique. NE213 liquid scintillators 12.7cm in diameter and 12.7cm thick were placed in directions of 15, 30, 60, 90, 120, and 150°. The typical flight path length was 1.5m. Neutron detection efficiencies were evaluated by calculation results of SCINFUL and CECIL codes. The experimental results were compared with JAERI quantum molecular dynamics code. For the meson incident reactions, adoption of NN in-medium effects was slightly useful for reproducing 870MeVπ+-incident neutron yields at neutron energies of 10–30MeV, as was the case for proton incident reactions. The π− incident reaction generates more neutrons than π+ incidence as the number of nucleons in targets decrease.
Neutron production cross section for 870 MeV PI+ on FE.
Neutron production cross section for 870 MeV PI+ on FE.
Neutron production cross section for 870 MeV PI- on FE.
Neutron production, in coincidence with fragments emitted in the 40Ca+H reaction at Elab=357A and 565A MeV, has been measured using a 3-module version of the multifunctional neutron spectrometer MUFFINS. The mean neutron multiplicities for neutrons detected in the angular range covered by MUFFINS (0°−3.2°) have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a preequilibrium emission of prompt neutrons in superposition to a “slower” deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in inclusive rapidity distributions. The energy dependence of the inclusive neutron production cross sections, measured in a previous work, is here interpreted as due to the stronger neutron focusing in the forward direction at the higher energy. Comparison with a BNV+phase space coalescence model is discussed.
No description provided.
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