Photoproduction of ϕ mesons by linearly polarized photons of energy 20–40 GeV and further evidence for a photoproduced high-massKK enhancement

Vector meson photoproduction with a linearly polarized beam

“…In Fig. 7, we compare our model to the data from the Omega-Photon collaboration [22]. Their data are taken in the energy range E γ = 20 − 40 GeV.…”

“…The model is extrapolated to E γ = 2.8 GeV and 4.7 GeV and compared to the three natural components of the SLAC SDMEs at these energies. In Section IV, we compare the model to the nine ω and ρ 0 SDMEs obtained with a polarized beam at SLAC with E γ = 9.3 GeV, to the nine φ SDMEs from LEPS [21] and Omega-Photon [22], and to the three ω SDMEs obtained with a unpolarized beam from CLAS [23,24], LAMP2 [25] and Cornell [26]. Furthermore, we test the Pomeron normalization for the ω and ρ 0 differential cross sections at E γ > 50 GeV, and the Regge exchange normalization for the ω, ρ 0 and φ differential cross sections at E γ = 9.3 GeV from Ref.…”

Improved crystal method for photon beam linear polarization measurement at high energies

“…the integrals of the dw ,⊥ /dy over the interval (2). In difference from the notations of [11] W, R and F calculated for the full interval (0,1) of y in this paper the pair production characteristics integrated over the interval (2) are denoted by small letters w, r and f for absorption coefficients, asymmetry and figure of merit, respectively.…”

“…with the numbers of pairs n ,⊥ produced in the interval (2). The degree of linear polarization is determined by the formula P=a/r where…”

“…At present there is a demand for production of linearly and still more of circularly polarized photons with energies ω ≥ 20 GeV because after the beautiful series of the SLAC [1] and few others photoproduction experiments carried out with linearly and circularly polarized photon beams at ω ≤ 10 GeV no published experimental data exist besides those obtained at CERN SPS on φ-photoproduction with the help of linearly polarized photons with ω = 20-75 GeV [2]. The SLAC beam was produced by Compton scattering of polarized laser photons on SLAC, 20 GeV electrons, and there was no necessity to measure its high polarization P ≈ 90%, while the polarization P ≈ 30% of the CERN beam produced by coherent bremsstrahlung on Si single crystal has been measured [3] with the help of the asymmetry of the decay ρ 0 → π + + π − because some experimental factors could influence and change the expected value of P. Now the operation of these as well as of another polarized photon beam used for few QED experiments only [4] is stopped.…”