We have measured π±p and pp elastic differential cross sections in the range |cosθc.m.|<0.35 for incident momenta from 2 to 9.7 GeV/c for π−p and pp and from 2 to 6.3 GeV/c for π+p. We find that the fixed-c.m.-angle πp differential cross sections cannot be described as simple functions of s. The data are compared to the energy and angular dependence predicted by the constituent model of Gunion, Brodsky, and Blankenbecler.
No description provided.
No description provided.
No description provided.
None
No description provided.
No description provided.
No description provided.
Baryon resonance production in quasi-two-body reactions has been studied for the channels K + p→K°p π + , K + n π + and K + p π ° at beam momenta of 2.53, 2.76 and 3.20 GeV/ c . The production cross sections, four-momentum transfer distributions and density matrix elements are given for the Δ(1236), N ∗ (1400), N ∗ (1500) and N ∗ (1680) states. The reaction K + p→K° Δ ++ (1236) is compared to the line reversed reaction K − n → K °Δ − and the charge-exchange SU(3) sum rule for pseudo-scalar meson plus Δ(1236) is tested.
No description provided.
No description provided.
No description provided.
A systematic study of p p and p d reactions producing strange particles between 1.09 and 3.45 GeV/ c has been completed. Reaction and resonance cross-section data are presented at 11 p p and 13 p d momentum settings. Evidence for a broad shoulder in the K K 3π final state near 1.8 GeV/ c is presented and contrasted to previously published work on a portion of the final data sample. No evidence for a p n → K 0 K − ω effect near 1.3 GeV/ c is found, ruling out an association of K K ω effects with the nearby isospin one enhancement in the total cross section. Finally, we find no evidence for a p p → K K ω enhancement near 1.8 GeV/ c .
No description provided.
No description provided.
No description provided.
In a bubble chamber experiment, we have measured p p elastic scattering at nine momenta in the range 1.51–2.90 GeV/ c . The extrapolation of the small angle region to t = 0 is discussed and compared with results of other experiments. The differential cross sections are fitted to an adaptation of the Frahn-Venter optical model and also compared to Regge-pole model predictions.
'1'. '2'. '3'.
'1'. '3'.
'2'.
Results on charged pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV are presented and compared to data at lower and higher energies. A rapid change of the energy dependence is observed around 30A GeV for the yields of pions and kaons as well as for the shape of the transverse mass spectra. The change is compatible with the prediction that the threshold for production of a state of deconfined matter at the early stage of the collisions is located at low SPS energies.
Transverse mass spectra for pion production in the central rapidity region for collisions at 20 GeV per nucleon.
Transverse mass spectra for pion production in the central rapidity region for collisions at 30 GeV per nucleon.
Transverse mass spectra for kaon production in the central rapidity region for collisions at 20 GeV per nucleon.
We have measured the total cross-section difference for pp scattering in initial spin states parallel to the beam direction at beam momenta of 1.17, 1.47, 1.69, 1.97 and 2.49 GeV/ c . This measurement was done in a standard transmission experiment. A striking energy dependence is observed with a maximum difference of −16.9 mb at P lab = 1.47 GeV/ c .
PRELIMINARY RESULTS.
PRELIMINARY RESULTS.
The total cross section for hadron production by high-energy photons has been measured from a number of nuclei ranging from hydrogen to uranium. Some shadowing is observed at a level considerably less than predicted by conventional vector-meson dominance but consistent with a modified theory. The energy dependence predicted by vectormeson dominance is observed. The shadowing in heavy nuclei shows a smooth transition from electroproduction to photoproduction.
No description provided.
The π+—photoproduction cross section is found to have a peak in the forward direction in disagreement with simple Regge pole models.
No description provided.
Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical accuracy of a few percent. The scaling power for the s-dependence of the cross section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.
Cross section of proton Compton Scattering at centre of mass energy squared of 4.82 GeV.
Cross section of proton Compton Scattering at centre of mass energy squared of 6.79 GeV.
Cross section of proton Compton Scattering at centre of mass energy squared of 8.90 GeV.
We have measured the differential cross section for the gamma n --> pi- p and gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon energies greater than 3.3 GeV exhibit a global scaling behavior for both pi- and pi+ photoproduction, consistent with the constituent counting rule and the existing pi+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi- to pi+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.
Differential cross section at THETA(CM) = 90 degrees.
Final state resonance production and single particle momentum spectra are presented for p p annihilations into K K and π's between 1.09 and 3.45 GeV/ c . Resonance production generally agrees with the Lamb statistical model. Momentum spectra of K's and π's are independent of incident energy, while the mean multiplicity increases in proportion to the c.m. energy, supporting the annihilation model of Jacob and Nussinov.
THESE CROSS SECTIONS WERE GIVEN IN DETAIL IN B. Y. OH ET AL., NP B51, 57 (1973).
No description provided.
A systematic study of p p and p d resonance production cross sections in non-strange annihilation channels between 1.51 and 2.90 GeV/ c has been completed. The data have been analysed in relation to the three known structures at c.m. N N energies of 2190, 2350 and 2375 MeV. Several resonance intermediate states may have broad maxima near the isopin one 2350 MeV structure. However, more data below 1.6 GeV/ c are required to better describe the background in this region before firm conclusions may be drawn.
No description provided.
No description provided.
A systematic study of p p and p d topological and reaction cross sections between 1.51 and 2.90 GeV/ c has been completed. The data have been analysed in relation to the three known structures at c.m. N N energies of 2190, 2350 and 2375 MeV. The data suggest that four- and six-pion annihilations of antiprotons on neutrons may be the source of the 2350 MeV effect. Further data below 1.60 GeV/ c are required to verify this tentative conclusion.
No description provided.
INCLUDING 3 PCT SYSTEMATIC ERROR.
No description provided.
Polarization and differential cross-section data are presented for elastic scattering of antiprotons on polarized protons at eight momenta between 0.9 and 2.5 GeV/ c . The data are fitted with a diffraction model.
COMBINED 0.88 AND 0.95 GEV/C DATA.
COMBINED 1.00 AND 1.04 GEV/C DATA.
COMBINED 1.01 AND 1.055 GEV/C DATA.
Photoproduction of the cascade resonances has been investigated in the reactions $\gamma p \to K^+ K^+ (X)$ and $\gamma p \to K^+ K^+ \pi^- (X)$. The mass split of the $\Xi$ doublet is measured to be $5.4\pm 1.8$ MeV/c$^2$, consistent with existing measurements. The differential (total) cross sections for the $\Xi^{-}$ have been determined for photon beam energies from 2.75 to 3.85 (4.75) GeV, and are consistent with a possible production mechanism of $Y^*\to K^+\Xi^-$ through a $t$-channel process. The reaction $\gamma p \to K^+ K^+ \pi^-[\Xi^0]$ has also been investigated in search of excited cascade resonances. No significant signal of excited cascade states other than the $\Xi^-(1530)$ is observed. The cross section results of the $\Xi^-(1530)$ have also been obtained for photon beam energies from 3.35 to 4.75 GeV.
Differential cross section for XI- production as a function of the invariant mass of the XI- with either of the K+ mesons for incident photon energy 2.79 Gev.
Differential cross section for XI- production as a function of the invariant mass of the XI- with either of the K+ mesons for incident photon energy 2.89 Gev.
Differential cross section for XI- production as a function of the invariant mass of the XI- with either of the K+ mesons for incident photon energy 2.99 Gev.
The differential cross sections of the elastic p p reaction have been measured at 1.2, 1.4, 1.8 and 2.6 GeV/ c incident p momentum. The measurements have been performed at the CERN PS using a system of multiwire proportional chambers. The angular region covers scattering angles from 0 to ∼200 mrad. Interference effects between the Coulomb and the nuclear amplitudes are used to derive the ratio of the real to imaginary part of the forward nuclear amplitude. These ratios are compared with theoretical predictions.
'MS'. 'TBIN'.
'MS'. 'TBIN'.
'MS'. 'TBIN'.
Substantial production of the resonances ϱ, f and ω has been observed in this reaction. In contrast with the channel p p → 2π + 2π − , associated production of resonances was found to occur. The behaviour of the associated production of ω-mesons with other resonances is shown to be consistent with some very simple assumptions. Alternative methods of displaying data for p p → ππω are discussed; it is shown that the longitudinal phase plot for this reaction is unlike that obtained for any previously reported reaction. Reasonable agreement for the behaviour of this channel is found with the multiperipheral model of Chan, Łoskiewicz and Allison.
STATISTICAL ERRORS ONLY. FOR MULTIPLE PI0 PRODUCTION, RESULTS ARE MODEL DEPENDENT.
ANALYSIS OF 5PION FINAL STATE. DISTRIBUTION FITTED WITH FIXED MASS AND WIDTH RESONANCES, THEN ONLY EVENTS ABOVE (FITTED) BACKGROUND TAKEN. CROSS SECTIONS CALCULATED BY PDG (COMPILATION PDG3).
None
Preliminary data.
The energy dependence of the pp elastic analyzing power has been measured using an internal target during polarized beam acceleration. The data were obtained in incident-energy steps varying from 4 to 17 MeV over an energy range from 0.5 to 2.0 GeV. The statistical uncertainty of the analyzing power is typically less than 0.01. A narrow structure is observed around 2.17 GeV in the two-proton invariant mass distribution. A possible explanation for the structure with narrow resonances is discussed.
Statistical errors only.
None
No description provided.
No description provided.
No description provided.
Threshold measurements of the associated strangeness production reactions pp --> p K(+) Lambda and pp --> p K(+) Sigma(0) are presented. Although slight differences in the shapes of the excitation functions are observed, the most remarkable feature of the data is that at the same excess energy the total cross section for the Sigma(0) production appears to be about a factor of 28 smaller than the one for the Lambda particle. It is concluded that strong Sigma(0)-p final state interactions, and in particular the Sigma-N --> Lambda-p conversion reaction, are the likely cause of the depletion for the yield in the Sigma signal. This hypothesis is in line with other experimental evidence in the literature.
The given errors are statistical only. The cross section presented as a function of the nominal excess energy.
Data on multiplicities of charged particles produced in proton-nucleus and nucleus-nucleus collisions at 200 GeV per nucleon are presented. It is shown that the mean multiplicity of negative particles is proportional to the mean number of nucleons participating in the collision both for nucleus-nucleus and proton-nucleus collisions. The apparent consistency of pion multiplicity data with the assumption of an incoherent superposition of nucleon-nucleon collisions is critically discussed.
No description provided.
No description provided.
No description provided.
Data on the mean multiplicity ofπ- produced in minimum bias proton-proton, proton-neutron and proton-nucleus interactions as well as central nucleus-nucleus collisions at momenta of 1.4–400 GeV/c per nucleon have been compiled and studied. The results for neutron-neutron and nucleon-nucleon interactions were then constructed. The dependence of the mean pion multiplicity in proton-nucleus interactions and central collisions of identical nuclei are studied as a function of the collision energy and the nucleus mass number. The number of produced pions per participant nucleon in central collisions of identical nuclei is found to be independent of the number of participants at a fixed incident momentum per nucleon. The mean multiplicity of negatively charged hadrons per participant nucleon for central nucleus-nucleus collisions is lower by about 0.12 than the corresponding multiplicity for nucleon-nucleon interactions atpLAB≲15 A·GeV/c, whereas the result at 200 A·GeV/c is above the corresponding nucleon-nucleon multiplicity. This may indicate change of the collision dynamics at high energy.
No description provided.
No description provided.
MEAN MULTIPLICITY OF N N COLLISIONS IS DEDUCED FROM PROTON-PROTON DATA.
None
No description provided.
No description provided.
No description provided.
Forum