The NA24 experiment at CERN investigated inclusive γγ, π0π0, and γπ0 final states in the mass range between 4 and 9 GeV/c2 produced in π−p, π+p, and pp reactions at a c.m.-system energy s=23.7 GeV. The π0π0 cross sections agree well with expectations of the quark-parton model. For γπ0 production in π−p and pp reactions, a clear signal is observed and cross sections are shown. The production of γγ events was observed with a statistical significance of 2.9σ in π−p reactions. The cross section is in agreement with a higher-order QCD prediction.
Cross sections are averaged over the transverse momentum differences up to a value which is 1.10 GeV for all points except the first two which are 0.5 and 0.75 GeV respectively.
No description provided.
Maximum accepted transverse momentum difference of pi0 pair is 1 GeV. Inclusive cross section integrated over the total geometrical acceptance of the detector.
The analyzing power of π−p→π0n has been measured for pπ=301−625 MeV/c with a transversely polarized target, mainly in the backward hemisphere. The final-state neutron and a γ from the π0 were detected in coincidence with two counter arrays. Our results are compared with predictions of recent πN partial-wave analyses by the groups of Karlsruhe-Helsinki, Carnegie-Mellon University-Lawrence Berkeley Laboratory (CMU-LBL), and Virginia Polytechnic Institute (VPI). At the lower incident energies little difference is seen among the three analyses, and there is excellent agreement with our data. At 547 MeV/c and above, our data strongly favor the VPI phases, and disagree with Karlsruhe-Helsinki and CMU-LBL analyses, which are the source of the πN resonance parameters given in the Particle Data Group table.
Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).
Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).
Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).
A proton-proton bremsstrahlung experiment has been carried out at TRIUMF using a 280-MeV polarized proton beam impinging on a liquid-hydrogen target. All three outgoing particles were detected: the higher-energy proton in a magnetic spectrometer, the lower-energy proton with plastic scintillators, and the photon in lead-glass Cherenkov detectors. The experiment shows the first unambiguous evidence for off-shell effects in the free nucleon-nucleon interaction, in that the analyzing powers disagree strongly with the predictions of the soft-photon approximation (which incorporates only on-shell information) but are consistent with the results of calculations using the Bonn and Paris potentials.
Estimated scale uncertainty is 1.5 pct.
Estimated scale uncertainty is 1.5 pct.
Estimated scale uncertainty is 1.5 pct.
We have measured the analyzing power in π+, π−, and KS0 production by a polarized proton beam at 13.3 and 18.5 GeV/c. The data cover the central and the beam fragmentation region, in the transverse-momentum range up to 2 GeV/c. The results indicate that sizable effects are present at high xF and also persist into the hard-scattering region for KS0 and π+. A zero value of the analyzing power was observed for π− production.
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.
The study of the J ψ transverse momentum distribution in oxygen-uranium reactions at 200 GeV/nucleon shows that 〈 P T 〉 and 〈 P T 2 〉 increase with the transverse energy of the reaction. Muon pairs in the mass continuum do not exhibit the same behaviour. The comparison of the J ψ production rates in central and peripheral collisions shows a significant diminution for low P T central events.
Two parametrization of the D(SIG)/D(PT) are used: first is : PT*exp(-SLOPE*PT**CONST(C=PT)) and second is : PT*exp(-2*MT/CONST(C=MT)).
D(SIG)/D(PT) is parameterized as PT*exp(-SLOPE*PT**CONST).
D(SIG)/D(PT) is parameterized as PT*exp(-SLOPE*PT**CONST).
Using data onvp and\(\bar vp\) charged current interactions from a bubble chamber experiment with BEBC at CERN, the average multiplicities of charged hadrons and pions are determined as functions ofW2 andQ2. The analysis is based on ∼20000 events with incidentv and ∼10000 events with incident\(\bar v\). In addition to the known dependence of the average multiplicity onW2 a weak dependence onQ2 for fixed intervals ofW is observed. ForW>2 GeV andQ2>0.1 GeV2 the average multiplicity of charged hadrons is well described by〈n〉=a1+a2ln(W2/GeV2)+a3ln(Q2/GeV2) witha1=0.465±0.053,a2=1.211±0.021,a3=0.103±0.014 for thevp anda1=−0.372±0.073,a2=1.245±0.028,a3=0.093±0.015 for the\(\bar vp\) reaction.
No description provided.
No description provided.
No description provided.
Relativistic iron, lanthanum, holmium, and gold projectile nuclei with several different energies have been fragmented in targets of polyethylene, carbon, aluminum, copper, and lead. Our detectors cleanly resolve the individual charges of the heaviest of these fragments and provide some limited information on the masses. We have measured 1256 elemental partial cross sections for the production of fragments from interactions in these target materials. Values have been derived for another 417 cross sections in a hydrogen medium. These cross sections depend on the energy and mass of the projectile nuclei as well as on the nature of the target. Total charge-changing cross sections were also found, but only in a composite target, and have been shown to be weakly dependent on energy. The mean mass losses observed for fragments that have lost a few protons show that typically many neutrons are lost with each proton, producing fragment nuclei that must be highly proton rich, and consequently very unstable. The cross sections for charge pickup on heavy targets show a rapid increase with decreasing energy, particularly for the heaviest targets. The systematics of the dependencies of the partial cross sections will be discussed in a companion paper.
TARGET NUCLEUS=CH2.
No description provided.
No description provided.
Measurements of the partial charge-changing cross sections for the fragmentation of relativistic iron, lanthanum, holmium, and gold nuclei of several different energies incident on targets of polyethylene, carbon, aluminum, and copper have been reported in an accompanying paper. This paper describes the systematics of the variations of these cross sections with energy, projectile, target, and fragment. We have been able to generate a seven-parameter global fit to 795 measured cross sections for the heavy targets which fits the data with a standard deviation of 7%. We have also generated a similar global fit to 303 measured cross sections for a hydrogen target which fits the data with a standard deviation of 10%. These representations imply that the hypothesis of limiting fragmentation is only accurate to some 20–30 %. Weak factorization can apply, but fits that are marginally better, and more physically plausible, can be obtained without factorization. We have identified, and discussed, a number of caveats to the applicability of these fits outside, and inside, the range of energies and masses covered. Excessively large cross sections for the loss of a single proton from the projectile nuclei suggest electromagnetic dissociation. The cross sections for fragments that experience large charge changes appear to become independent of the size of the charge change. Very heavy projectiles have a significant probability of experiencing fission.
No description provided.
No description provided.
No description provided.
In an experiment using the CERN SPS hyperon beam, we have measured the cross sections for inclusive production of Ξ0 (accompanied by a charged particle), Ξ(1530)- and Ξ(1530)0 in Ξ--beryllium collisions at 116 GeV/c. All differential cross sections are found to be well described by the from (1−xF)n exp (−bpT2) over the whole accessible kinematical region (xF>0.3). The invariant production spectra for Ξ0, Ξ(1530)- and Ξ(1530)0, as well as those for Ξ-, and Ω- (obtained previously from the same data), are compared to theoretical predictions deduced from a two-component quark-diquark cascade model.
Total Inelastic Cross Section. This is an estimate based on the measurements of N BE --> INELASTIC and N P --> INELASTIC (T J Roberts et al., NP B159 (1979), 56) and the measurement of XI- P --> INELASTIC (S F Biagi et al., NP B186 (1981), 1).
The XI- and OMEGA- data were computed from Biagi et al., ZP C34 (87) 187.
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