Measurement of Spin-Density Matrix Elements for $\phi$-Meson Photoproduction from Protons and Deuterons Near Threshold

The LEPS collaboration Chang, W.C. ; Ahn, D.S. ; Ahn, J.K. ; et al.
Phys.Rev.C 82 (2010) 015205, 2010.
Inspire Record 859164 DOI 10.17182/hepdata.55768

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\gamma p \to \phi p$, $\gamma d \to \phi p n$ and $\gamma d \to \phi d$ at forward production angles. A linearly polarized photon beam at $E_{\gamma}$=1.6-2.4 GeV was used for the production of $\phi$ mesons. The natural-parity Pomeron exchange processes remains dominant nearthreshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from nucleons but is greatly reduced in the coherent production from deuterons. There is no strong $E_{\gamma}$-dependence, but some dependence on momentum-transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed.

81 data tables

Measurements of the spin density matrix element RHO(JJ=0,MM=00) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

Measurements of the spin density matrix element RE(RHO(JJ=0,MM=10)) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

Measurements of the spin density matrix element RHO(JJ=0,MM=1-1) for the GAMMA P --> PHI P reaction in the helicity system as a function of T-Tmin for 3 incident photon energy regions.

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Measurement of the reaction C-12 (muon-neutrino, mu-) X near threshold

The LSND collaboration Albert, M. ; Athanassopoulos, C. ; Auerbach, L.B. ; et al.
Phys.Rev.C 51 (1995) 1065-1069, 1995.
Inspire Record 378770 DOI 10.17182/hepdata.25973

The reaction $~{12}{\rm C}(\nu_\mu,\mu~-) {\rm X}$ has been measured near threshold using a $\pi ~+$ decay-in-flight $\nu_\mu$ beam from the Los Alamos Meson Physics Facility and a massive liquid scintillator neutrino detector (LSND). In the energy region $123.7 < {\rm E}_\nu < 280$ MeV, the measured spectral shape is consistent with that expected from the Fermi Gas Model. However, the measured flux--averaged inclusive cross section ($(8.3 \pm 0.7 {\rm stat.} \pm 1.6 {\rm syst.}) \times 10~{-40} {\rm cm}~2$) is more than a factor of 2 lower than that predicted by the Fermi Gas Model and by a recent random phase approximation calculation.

1 data table

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