The width of the ω meson in the nuclear medium

Abstract

We evaluate the width of the ω meson in nuclear matter. We consider the free decay mode of the ω into three pions, which is dominated by ρπ decay, and replace the ρ and π propagators by their medium modified ones. We also take into account the quasielastic and inelastic processes induced by a vector-baryon interaction dominated by vector meson exchange, as well as the contributions coming from the ω → KK mechanism with medium modified K,K propagators. We obtain a substantial increase of the ω width in the medium, reaching a value of 129 ± 10 MeV at normal nuclear matter density for an ω at rest, which comes mainly from ωN → ππN, ωN N → πN N processes associated to the dominant ω → ρπ decay mode. The value of the width increases moderately with momentum, reaching values of around 200 MeV at 600 MeV/c.

Momentum dependence of the imaginary part of the $ \omega$ - and $ \eta^{\prime}$ -nucleus optical potential

“…They differ in the partitioning into the π and ρ modifications and obtain differences in the 3-momentum dependence of the ω width. While Cabrera and Rapp [27] find a moderate momentum dependence, Ramos et al [28] get an almost linear increase of the width with momentum. Alternatively, Klingl et al [29], Lutz et al [30] and Mühlich et al [31] consider the coupling of the ω meson to nucleon resonances as the main effect driving the in-medium broadening of the ω meson.…”

“…4). The solid curves correspond to calculations by Ramos et al [28], the short dashed curves to calculations by Cabrera and Rapp [27] for different model assumptions (see text). The brown dashed-dotted curve shows the momentum dependence of the ω in-medium width calculated in a coupled-channel resonance model [31].…”

“…A further motivation for the present work were recent theoretical studies of the ω width in cold nuclear matter as a function of momentum and nuclear density by Cabrera and Rapp [27] and by Ramos et al [28]. Both groups calculated the in-medium ω width in a hadronic many-body approach, focusing on a detailed treatment of the in-medium modifications of intermediate πρ states.…”

“…At normal nuclear matter density, they found an in-medium ω width of the order of 100-200 MeV, however, with differences in the 3-momentum dependence. The calculations were confined to the momentum ranges below 1000 MeV/c in [27] and 600 MeV/c in [28]. Earlier calculations investigated the direct coupling of the ω meson to nucleon resonances.…”

In-medium properties of mesons

“…[18] ≈ 0 MeV/c 2 ≈ 60 MeV χ unitary [19] 100-200 MeV many-body [20] 150-200 MeV e.g. for a meson at rest in infinitely extended nuclear matter with constant density, a scenario far from reality.…”