We present differential cross-section data for the reaction π+p→π+p near 180° in the center-of-mass system at beam momenta between 3.25 GeVc and 10 GeVc.
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We have observed a second sharp peak in the cross section for e+e−→hadrons at a center-of-mass energy of 3.695±0.004 GeV. The upper limit of the full width at half-maximum is 2.7 MeV.
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We report observation of the S* meson in the reaction π−+p→S*+n. The S* decays into ππ and KK and is seen most clearly in the 2π0 channel. A fit to the data gives a sheet-II pole at 987±7−i(24±7) MeV and a relative coupling gS→KKgS→ππ of 3.8 ± 1.0.
AT AROUND K+ K- THRESHOLD.
A novel form of mass spectrometer has been used to measure the masses, widths, and cross sections of the η, ω, X0(958), and φ mesons near their respective thresholds in the reaction π−+p→missingmass+n. The incident momentum is varied in small steps through the threshold while neutrons of a given momentum are detected near zero degrees. The lower limit of the c.m. momentum P* at which measurements have been made ranges from about 50 MeV/c at the φ to about 30 MeV/c at the η. A somewhat low value for the ω mass, 782.3 ± 0.6 MeV, is found. The width of the X0 is < 1.9 MeV (95% confidence level). All four mesons show evidence of S-wave production, with values of σP* of 21.2 ± 1.8, 0.35 ± 0.03, and 0.29 ± 0.06 μb/(MeV/c) for the η, X0, and φ, respectively. A rapid rise in the ω cross section appears to be modified by a final-state interaction. The effect of this rise can probably be seen in some S11 pion-nucleon phase-shift solutions. Evidence is also presented of a sudden drop in the π+π− mass spectrum just above the threshold for the production of a K+K− pair. The paper includes a comprehensive discussion of the method and of the details of the spectrometer.
CROSS SECTIONS NEAR THRESHOLD.
Experimental results are presented for the available channels in the 1.2 GeV/ c π + p interaction. An isobaric model with incoherent addition of the amplitudes is used to determine the π, Δ and N ∗ abundance rates in the π + π o p final state. The multipole parameters in the density matrix of the Δ ++ are determined as functions of its production angle.
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LEGENDRE POLYNOMIAL FIT USED TO CORRECT FOR ELASTIC EVENTS LOST FROM THE FORWARD BIN.
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In an experiment with the CERN 2 metre DBC the reaction K$^+$d $\to$ K$^0 \pi^+$d is studied at an incident momentum of 4.6 GeV/c. The cross section is found to be (66 ± 10) μb for four-momentum transfer squared from target to recoil deuteron greater than 0.02 GeV 2 , and the reaction is dominated by the production of K$^*+$ (892) via natural parity exchange. Using data for the reactions K$^\pm$d $\to$ K$^{*\pm}$(892)d in the incident momentum range 2–13 GeV/ c the parameters of the effective exchanged trajectory are estimated.
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We present an analysis, in the framework of the triple Regge model, of our recent experimental results on the reaction p+p→p+X between 50 and 400 GeV.
The cross sections is fitted in the framework of the triple Regge model. The symbols P and R in the (C=...) denote pomeron and reggeon, respectively. For fit I and II the authors used conventional trajectories alpha(P) = 1 +0.25*T, alpha(R) = 0.5 + T. Fit II is restricted to data with (1 - M(P=4)**2/S) > 0.84. In fit III they use alpha(R) = 0.2 + T for the RRP term. Fit IV is like fit I with additional fixed (pion pion P) term.
The cross sections is fitted in the farmework of the triple Regge model. The symbols P and R in teh (C=...) denote pomeron and reggeon, respectively. CONST(C=C) and SLOPE are from the replacement of the RRP term by the exponential one : CONST(C=C)*(SLOPE*(1-x)). See text for detail.
We have measured muon-proton deep inelastic scattering in the range 0.4<q2<3.6 (GeV/c)2. The data are consistent with muon-electron universality, and if the ratio ρ=νW2(μ−p)νW2(e−p) is fitted with the form ρ=N(1+q2Λ2)−2, we obtain N=0.997±0.043 and Λ−2=+0.006±0.016 (GeV/c)2. This result establishes that |Λ|>~5.1 GeV/c with 95% confidence.
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The energy dependence of backward π+p elastic scattering has been measured for incident π momenta 2.0-6.0 GeV/c in steps of typically 100 MeV/c. Values are presented for both the differential cross section extrapolated to 180° and the slope of the backward peak as a function of momentum. In the s channel we see the effects of the established Δ++ resonances and evidence for the Δ(3230). Also, the data show the existence of a negative-parity Δ resonance with mass ∼2200 MeV/c2.
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We have measured total cross sections for p−p scattering with the results σT=40.42±0.27 mb at 200 GeV/c and 40.40 ± 0.28 mb at 300 GeV/c. Our 300-GeV/c result is significantly higher than published data from the CERN intersecting storage rings. Our data, taken together with the Serpukhov data, indicate that the cross section rises ≅ 2 mb between 60 and 250 GeV. The variation of the cross section with energy may be more complicated than the a+blnsα behavior commonly assumed for Elab≳50 GeV.
Axis error includes +- 0.0/0.0 contribution (QUOTED ERRORS ARE COMBINED STATISTICAL AND SYSTEMATIC).
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