Observation of in-medium modifications of the omega meson

The photoproduction of omega 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 omega meson via the reaction gamma + A --> omega + X --> pi(0)gamma + X(')....

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Veröffentlicht in:	Physical review letters 2005-05, Vol.94 (19), p.192303-192303, Article 192303
Hauptverfasser:	Trnka, D, Anton, G, Bacelar, J C S, Bartholomy, O, Bayadilov, D, Beloglazov, Y A, Bogendörfer, R, Castelijns, R, Crede, V, Dutz, H, Ehmanns, A, Elsner, D, Ewald, R, Fabry, I, Fuchs, M, Essig, K, Funke, Ch, Gothe, R, Gregor, R, Gridnev, A B, Gutz, E, Höffgen, S, Hoffmeister, P, Horn, I, Hössl, J, Jaegle, I, Junkersfeld, J, Kalinowsky, H, Klein, Frank, Klein, Fritz, Klempt, E, Konrad, M, Kopf, B, Kotulla, M, Krusche, B, Langheinrich, J, Löhner, H, Lopatin, I V, Lotz, J, Lugert, S, Menze, D, Messchendorp, J G, Mertens, T, Metag, V, Morales, C, Nanova, M, Novotny, R, Ostrick, M, Pant, L M, van Pee, H, Pfeiffer, M, Roy, A, Radkov, A, Schadmand, S, Schmidt, Ch, Schmieden, H, Schoch, B, Shende, S, Suft, G, Sumachev, V V, Szczepanek, T, Süle, A, Thoma, U, Varma, R, Walther, D, Weinheimer, Ch, Wendel, Ch
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Sprache:	eng
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Zusammenfassung:	The photoproduction of omega 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 omega meson via the reaction gamma + A --> omega + X --> pi(0)gamma + X('). Results obtained for Nb are compared to a reference measurement on a LH2 target. While for recoiling, long-lived mesons (pi(0), eta, and eta;(')), which decay outside of the nucleus, a difference in the line shape for the two data samples is not observed, we find a significant enhancement towards lower masses for omega mesons produced on the Nb target. For momenta less than 500 MeV/c an in-medium omega meson mass of M(medium) = [722(+4)(-4)(stat)+35-5(syst)] MeV/c(2) has been deduced at an estimated average nuclear density of 0.6rho(0).
ISSN:	0031-9007 1079-7114
DOI:	10.1103/PhysRevLett.94.192303