We report a new measurement of the differential cross section for π−p→π0n from pπ=649 to 752 MeV/c, which is around the opening of the η channel (685 MeV/c). Our data support the main features of the π−p charge-exchange differential cross sections generated by the SAID πN partial-wave analysis. The opening of the η channel has a clear effect on the shape of the excitation function for dσ(π−p→π0n), which is most noticeable in the backward direction.
Differential cross section for incident pion momentum 649, 654 and 657 MeV.
Differential cross section for incident pion momentum 661, 666 and 669 MeV.
Differential cross section for incident pion momentum 673, 678 and 681 MeV.
The differential cross section for η production in reaction π−p→ηn has been measured over the full angular range at seven incident π− beam momenta from threshold to pπ−=747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total η production cross section σtot is obtained by integration of dσ/dΩ. Starting at threshold, σtot rises rapidly, as expected for S-wave-dominated production. The features of the π−p→ηn cross section are strikingly similar to those of the SU(3) flavor-related process K−p→ηΛ. Comparison of the π−p→ηn reaction is made with η photoproduction.
Total cross sections.
Differential cross section for the 4 lowest beam momenta.
Differential cross section for the 3 highest beam momenta.
Measured values of the differential cross section for pion-nucleon charge exchange are presented at momenta 148, 174, 188, 212, 238, 271, 298, and 323 MeV/c, a region dominated by the Delta resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically 2-6%, exceptions being the results at the lowest momentum and at the most forward measurements of the five lowest momenta. We estimate the systematic uncertainties to be 3-6%.
The errors shown are statistical only.
The errors shown are statistical only.
The total charge-exchange reaction cross section as a function of pion momentum obtained by integrating the differential cross sections. The errors shown are the total and statistical errors.
Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 87.2 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 68.4 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 57.2 MeV from the data set 1.
High quality analyzing powers for the π−p→→π0n reaction have been obtained with a polarized proton target over a broad angular range at incident kinetic energies of 98.1, 138.8, 165.9, and 214.4 MeV. This experiment nearly doubled the existing πN single-charge-exchange database for energies ranging from 10 to 230 MeV, with 36 new analyzing powers. The Neutral Meson Spectrometer was used to detect the outgoing neutral pions. The data are well described by recent phase-shift analyses. When combined with high-precision and accurate cross section data at the same energies, the data can provide a good test of the degree of isospin breaking in the region of the Δ(1232) resonance. They will also be helpful for constraining the evaluation of the pion-nucleon σ term from the scattering amplitudes.
First error is total uncertainty.
First error is total uncertainty.
First error is total uncertainty.
Inclusive production of ϕ,K*0, and\(\overline {K*^0 } \) mesons has been measured in γp, π±p andK± p collisions at beam energies of 65 GeV
Statistical errors only.
Statistical errors only.
Statistical errors only.. An entry 0.00 indicates a statistical error of < 0.005.
Measurements are reported of inclusivef2(1270) andf0(975) production in γp, π±p andK±p collisions at photon beam energies of 65 to 175 GeV and hadron beam energies of 80 and 140 GeV. Thef2 andf0 mesons were found at masses of 1.250 GeV and 0.961 GeV respectively. Inclusivef2 production at lowxF was found to have a similarpT dependence for each beam type, whereas an additional pion-exchange contribution was found for production by pions at highxF. Cross sections are compared with those for ρ0 production and give no indication of a non-q\(\bar q\) component in eitherf-meson state.
No description provided.
No description provided.
No description provided.
Measurements are reported of inclusive production of η-mesons in the beam fragmentation region in γp, πp andKp collisions. Results include a small but significant departure from VMD, and a pronounced rise in theη/π0 ratio with increasingpT.
No description provided.
No description provided.
No description provided.
The inclusive production of ρ0 mesons was measured in γp andh±p collisions at beam energies of 65 GeV≦Eγ≦175 GeV andEh=80, 140 GeV, respectively, whereh is π orK. Cross sections were determined for all beams and energies as functions ofxF (−0.1≦xF≦1.0),pT (0≦pT≦3.5 GeV/c) and the polar decay angle of the ρ0 by fitting the ρ0 signal in π+π- mass distributions. The ρ0 line shape is found to be distorted from a pure Breit-Wigner distribution throughout most of thexF−pT plane for both photon and hadron beams and a simple explanation is suggested. Throughout the paper emphasis is put on the comparison of photon and hadron beam data. The comparison of cross sections of γp andhp data provides a measure of the Vector Meson Dominance factor throughout thexF−pT range of the ρ0. The ρ0 production at lowpT can be described for both photon and hadron beams by a triple regge model at largexF. Similarly central production is well described by the quark-antiquark fusion model. At largepT there is an excess of ρ0 photoproduction which is consistent with the expected onset of pointlike photon interactions.
No description provided.
No description provided.
No description provided.
Measurements are reported of inclusive production of π0-mesons in the beam fragmentation region in γp, πp andKp collisions. Results include the ratio of π0 production inKp and πp collisions, showing reduced production from fragmentation of theK-meson, and the ratio of π0 production in photon and hadron collisions which shows agreement with modified Vector Meson Dominance at lowPT, and departures at higherPT signalling the onset of direct photon reactions. The pattern of departure from Feynman scaling at highPT points to a contribution of hard parton-parton collisions in both γp and πp collisions.
No description provided.
No description provided.
No description provided.
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