Measurement of the in-medium phi-meson width in proton-nucleus collisions

TL;DR

This study measures phi meson production in proton-nucleus collisions at 2.83 GeV, revealing that the in-medium phi width is significantly larger than its free-space value, indicating strong in-medium effects.

Contribution

It provides the first experimental evidence that the in-medium phi meson width is substantially increased compared to its free width in proton-nucleus collisions.

Findings

Phi production cross section scales as A^0.56.

In-medium phi width is about ten times larger than free width.

Data supports strong in-medium modifications of phi mesons.

Abstract

The production of phi mesons in the collisions of 2.83 GeV protons with C, Cu, Ag, and Au at forward angles has been measured via the phi -> K+K- decay using the COSY-ANKE magnetic spectrometer. The phi meson production cross section follows a target mass dependence of A^0.56+/-0.02 in the momentum region of 0.6-1.6 GeV/c. The comparison of the data with model calculations suggests that the in-medium phi width is about an order of magnitude larger than its free value.