Observation of In-Medium Modifications of theωMeson

Abstract

The photoproduction of ω mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the ω meson via the reaction γ + A → ω + X → π 0 γ + X ′ . Results obtained for Nb are compared to a reference measurement on a LH2 target. While for recoiling, long-lived mesons (π 0 , η and η ′ ), which decay outside of the nucleus, a difference in the lineshape for the two data samples is not observed, we find a significant enhancement towards lower masses for ω mesons produced on the Nb target. For momenta less than 500 MeV/c an in-medium ω meson mass of M medium = [722 +2 −2 (stat) +35 −5 (syst)] MeV/c 2 has been deduced at an estimated average nuclear density of 0.6 ρ0.

Dielectron production in Ar + KCl collisions at 1.76AGeV

“…One expects that most of the ω's contributing to this peak decayed after having left the reaction zone, that is, after freeze-out. Recently measured ω photoproduction cross sections [31][32][33] have been interpreted [1] in the sense of a strong broadening (up to 150 MeV) of the decay width of this meson in the nuclear medium already at normal nuclear density. We do not observe such a modification in our ω signal: the shape of the observed peak is solely determined by the detector response, that is, by the intrinsic momentum resolution of the HADES tracking system.…”

K̄*mesons in dense matter

“…[21][22][23][24][25][26] for details). Experimentally, a large shift of the mass of the ω was reported in a study of photon-induced ω production in nuclei, with the ω being detected through its π 0 γ decay channel [27]. However, it was shown in Ref.…”

Asymmetric neutron stars in the presence of vacuum fluctuations

“…We note that the on-shell effective meson masses (Fig. 3a) decrease at the normal density, which are indicated in most experiments and theoretical studies [12][13][14][15][16][17][18][19]. As noted in Ref.…”

“…The effective meson masses (on-shell and off-shell) calculated from Eqs. (11)(12)(13)(14)(15)(16)(17) are depicted in Fig. 3.…”

“…[12], it is better to use the in-medium meson masses in such RMF studies of nuclear matter at high density (Actually such in-medium meson masses have been studied in both experimental and theoretical approaches [13][14][15][16][17][18]). Following Refs.…”