Charged hadron production via e + e − → h ± X where h ± = π ± , K ± , p ̄ has been measured for s values between 13 and 25 GeV 2 . Inclusive cross sections and the evidence for scaling are presented.
No description provided.
We have extended our survey of the reaction γ+p→p+e++e− by collecting 20 000 additional e+e− pairs in the invariant-mass region 900<m<1500 MeV. The measured interference pattern shows two enhancements at mass values of 1097 and 1266 MeV. The parameters of those structure, when interpreted as vector mesons in the VDM framework, are given.
No description provided.
We observe a resonancelike structure in the total cross section for hadron production by e+e− colliding beams at a mass of 4414 ± 7 MeV having a total width Γ=33±10 MeV. From the area under this resonance, we deduce the partial width to electron pairs to be Γee=440±140 eV. Further structure of comparable width is present near 4.1 GeV.
No description provided.
The differential cross sections of the proton Compton scattering around the second resonance have been measured at a c.m. angle of 90° for incident photon energies between 450 MeV and 950 MeV in steps of 50 MeV, and at an angle of 60° for energies between 600 MeV and 800 MeV. The results show that the peak of the 2nd resonance agrees with that of the pion photoproduction process. We also calculated the proton Compton scattering based on unitarity and fixed- t dispersion relations. The calculation describes well the data of the cross section and the recoil proton polarization.
No description provided.
No description provided.
Cross sections for e+e−→hadrons, e+e−, and μ+μ− near 3684 MeV are presented. The ψ(3684) resonance is established as having the assignment JPC=1−−. The mass is 3684 ± 5 MeV. The partial width for decay to electrons is Γe=2.1±0.3 keV and the total width is Γ=228±56 keV.
No description provided.
Compton-scattering cross sections from hydrogen (γp→γp) and from deuterium have been measured at four-momentum transfer t in the range 0.014<~−t<~0.17 GeV2 and photon energies of 8 and 16 GeV. Fits to our proton data of the form dσdt=AeBt give B≈7.8 GeV−2 and an intercept A which is in agreement with the optical point. Both coherent scattering from deuterons and incoherent scattering from neutrons and protons are seen from deuterium. A small difference between the neutron and proton cross sections is seen, indicating the presence of about a 3% isovector t-channel exchange amplitude in addition to the predominant isoscalar amplitude. The vector-dominance model predicts lower cross sections (by at least 20%) for both the hydrogen and deuterium cases.
Axis error includes +- 3/3 contribution (SUBTRACTIONS WERE MADE FOR THE REACTIONS GAMMA P --> PI0 N, ETA N, OMEGA N AND PI0 DELTA(1232)).
Axis error includes +- 3/3 contribution (SUBTRACTIONS WERE MADE FOR THE REACTIONS GAMMA P --> PI0 N, ETA N, OMEGA N AND PI0 DELTA(1232)).
We present cross sections for e+e−→hadrons, e+e−, and μ+μ− near 3095 MeV. The ψ(3095) resonance is established as having an assignment JPC=1−−. The mass is 3095 ±4 MeV. The partial width to electrons is Γe=4.8±0.6 keV and the total width Γ=69±15 keV. Total rates and interference measurements for the lepton channels are in accord with μ−e universality.
No description provided.
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.
No description provided.
We have observed a very sharp peak in the cross section for e+e−→hadrons, e+e−, and possibly μ+μ− at a center-of-mass energy of 3.105±0.003 GeV. The upper limit to the full width at half-maximum is 1.3 MeV.
No description provided.
A high-statistics measurement of the reaction π − p→ η n; η →2 γ has been performed at the 70 GeV Serpukhov accelerator for 15, 20, 25, 30 and 40 GeV/ c incident pion momentum using the NICE set-up with its associated 648-channel hodoscope spectrometer for γ-ray detection. It is found that the spin-flip and non-spin-flip amplitudes can be parametrized, for small | t |, as exponentials with the same slopes to within a few percent. For | t | ≳ 1 (GeV/ c ) 2 there is a break in the differential cross section. In addition, the A 2 effective trajectory deviates markedly for | t | ≳ 1 GeV/ c ) 2 from the linear behaviour valid for smaller | t |.
No description provided.
No description provided.
No description provided.