Measurement of the incoherent γd→ϕpn photoproduction near threshold

Abstract

We report measurements of differential cross sections and decay asymmetries of incoherent φ-meson photoproduction from the deuteron at forward angles using linearly polarized photons at E γ =1.5-2.4 GeV. The nuclear transparency ratio for the deuteron shows a large suppression, and is consistent with the A-dependence of the ratio observed in a previous measurement with nuclear targets. The reduction for the deuteron cannot be adequately explained in term of isospin asymmetry. The present results suggest the need of refining our understanding of the φ-N interaction within a nucleus.

Theoretical study of incoherent φ photoproduction on a deuteron target

“…Our theoretical results support the findings of Ref. [24] and shed light on the different results claimed for the LEPS experiment [17].…”

“…[24], and point out missing experimental information for a proper comparison of our results with the recent measurements of Ref. [17]. By analogy to the photoproduction in nuclei we also have here effects of Fermi motion and of φ and proton rescatterings, which are studied here in detail and compared to the data.…”

“…Tests on Pomeron exchange in this reaction have also been another one of the motivations. Experimental work on the deuteron has been done at LEPS [17] looking for dσ/dt close to t max and related theoretical work on near threshold φ photoproduction on the deuteron has been done in [18]. Photoproduction of φ mesons in nuclei has also been addressed in [19], looking at the transparency ratio [20], deducing from there an enhanced φN cross section in nuclei with respect to the one on a free proton.…”

Near-threshold photoproduction of ϕ mesons from deuterium

“…[12]. However, they are not consistent with the recent LEPS results [11] from deuterim in a similar photon energy range, but in a smaller momentum transfer region. The corresponding |t − t 0 | range for the LEPS data in a photon energy range of 1.65 to 1.75 GeV is less than 0.2 GeV 2 .…”

“…The deuteron, a loosely bound and the simplest nuclear system, provides an excellent testing ground to study the reaction mechanisms. Such a study has been reported [11] recently by the LEPS collaboration on the measurement of the incoherent γd → φpn photoproduction near threshold at forward angles. The nuclear transparency ratio for φ has been extracted, which shows a large suppression consistent with the nuclear dependence reported [6] by the same collaboration previously using φ-meson photoproduction data from heavier nuclear targets.…”