학술논문
Evidence for a 'Narrow' Roper Resonance - the Breathing Mode of the Nucleon
Document Type
Working Paper
Author
Clement, H.; Skorodko, T.; Bashkanov, M.; Bogoslawsky, D.; Calen, H.; Cappellaro, F.; Demiroers, L.; Doroshkevich, E.; Ekstrom, C.; Fransson, K.; Hoistad, L. Gustafsson. B.; Ivanov, G.; Jacewicz, l M.; Jiganov, E.; Johansson, T.; Kaskulov, M.; Khakimova, O.; Keleta, S.; Koch, I.; Kren, F.; Kullander, S.; Kupsc, A.; Kuznetsov, A.; Marciniewski, P.; Martemyanov, B.; Meier, R.; Morosov, B.; Oelert, W.; Pauly, C.; Pettersson, H.; Petukhov, Y.; Povtorejko, A.; Ruber, R. J. M. Y.; Schonning, K.; Scobel, W.; Shwartz, B.; Sopov, V.; Stepaniak, J.; Thorngren-Engholm, P.; Tikhomirov, V.; Turowiecki, A.; Wagner, G. J.; Wolke, M.; Yamamoto, A.; Zabierowski, J.; Zlomanczuk, J.
Source
Proc. CRIMEA06 Int. Conf. "New trends in High Energy Physics", Yalta, Crimea 2006
Subject
Language
Abstract
All the time since its discovery the N$^*$(1440) baryon state, commonly known as Roper resonance, has been a state with many question marks - despite of its 4-star ranking in the particle data book. One reason is that it does not produce any explicit resonance-like structures in the observables of $\pi$N or $\gamma$N reactions. Only in partial wave analyses of $\pi$N scattering data a clear resonance strcuture gets obvious in the $P_{11}$ partial wave. Very recent measurements of the J/$\Psi$ decay by the BES collaboration and of the $pp \to np\pi^+$ reaction at 1.3 GeV by the CELSIUS-WASA collaboration show for the first time a clear resonance structure in the invariant $n\pi^+$ mass spectrum for the Roper resonance at M $\approx$ 1360 MeV with a width of about 150 MeV. These values agree very favorably with the pole position results of recent $\pi$N phase shift analyses. In consequence of this very low-lying pole postion, which is roughly 100 MeV below the nominal value, the decay properties have to be reinvestigated. From our two-pion production data we see that the decay mainly proceeds via N$^* \to $N$\sigma$, i.e. a monopole transition as expected for the breathing mode of the nucleon.
Comment: CRIMEA06
Comment: CRIMEA06