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.
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.
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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.
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Data are presented on the inclusive production of π±, K±, p, and p¯ for π+, K+, and protons incident on nuclear targets at 100 GeV. The results cover the kinematic range 30≤P≤88 GeV/c for Pt=0.3 and 0.5 GeV/c. The observed A dependence of the invariant cross sections exhibits remarkable simplicity, which does not naturally follow from current models of particle production. The results show that the hypothesis of limiting fragmentation can be extended to include collisions with nuclei.
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We present measurements of the production symmetric high-mass hadron and pion pairs by protons of 200, 300, and 400 GeV, incident on a beryllium target. The two-particle invariant cross section for pion production can be described by the function E1E2d6σdp13dp23=(1.7×10−28)pt−8.4(1−xt)14 cm2/GeV4 (where pt is the mean pt of the two hadrons). Functions of the same form have been used in describing single-pion inclusive production. Equality of the exponents of pt in the two processes is observed, confirming the role of smearing contributions to single-hadron cross sections.
E*D3(SIG)/D3(P) is fitted by CONST*(1-XT)**POWER*PT**POWER.
E1*E2*D6(SIG)/D3(P1)/D3(P2) is fitted by CONST*(1-XT)**POWER*PT**POWER, where PT is (pt1 + pt2)/2.
Measurements of the invariant cross section Ed3σd3p are presented for the production of hadrons (π, K, p, and p¯) at large transverse momentum (p⊥) by 200-, 300-, and 400-GeV protons incident on H2, D2, Be, Ti, and W targets. The measurements were made at a laboratory angle of 77 mrad, which corresponds to angles near 90° in the c.m. system of the incident proton and a single nucleon at rest. The range in p⊥ for the data is 0.77≤p⊥≤6.91 GeV/c, corresponding to values of the scaling variable x⊥=2p⊥s from 0.06 to 0.64. For p−p collisions, the pion cross sections can be represented in the region x⊥>35 by the form (1p⊥n)(1−x⊥)b, with n=8 and b=9. The ratio of π+ to π− production grows as a function of x⊥ to a value larger than 2 at x⊥≳0.5. The ratios of the production of K+ and protons to π+ and of K− and antiprotons to π− also scale with x⊥ for p−p collisions. The K±, p, and p¯ fitted values for n and b are given. Particle ratios are also presented for D2, Be, Ti, and W targets and the dependences on atomic weight (A) are discussed.
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We have observed muon pairs with effective masses in the range 7<~Mμμ<~11 GeV/c2 produced by 300- and 400-GeV protons incident on a Cu target at Fermilab. The production cross section per nucleon, dσdMμμ, for 400-GeV incident protons is found to fall from 1 × 10−36 cm2/(GeV/c2) at Mμμ=7.7 GeV/c2 to 2.7 × 10−38 cm2/(GeV/c2) at Mμμ=11.2 GeV/c2. We find that a significant fraction of the observed direct single muons come from high-mass dimuons.
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We have measured, as a function of transverse momentum (p⊥), the invariant cross section Edσd3p for the production of π±, K±, p, p¯, d, and d¯ in proton collisions with a tungsten (W) target at incident proton energies of 200, 300, and 400 GeV. The measurements were made in the region of 90° in the c.m. system of the incident proton and a single nucleon at rest. Measurements were also made with 300-GeV protons incident on Be, Ti, and W targets of equal interaction length. These p-nucleus measurements, which show a strong dependence on atomic number at high p⊥, were used to extract effective proton-nucleon cross sections by extrapolation to atomic number unity. At large values of the scaling variable x⊥=2p⊥s, where s is the square of the c.m. energy, the pion data are found to be well represented by the expression (s)−ne−ax⊥, with n=11.0±0.4 and a=36.0±0.4. x⊥<0.35, where similar measurements have been made at the CERN ISR, our data are in good agreement with the ISR data.
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We have observed muons produced directly in Cu and W targets by 300-GeV incident protons. We find a yield of muons which is approximately a constant fraction (0.8·10−4) of the pion yield for both positive and negative charges and for transverse momenta between 1.5 and 5.4 GeV/c.
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Differential cross sections as a function of transverse momentum are presented for the production at ∼90° (in the c.m. system) of π±, K±, p, and p¯ in p-nucleus collisions at incident proton energies of 200 and 300 GeV.
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