TY - JOUR
T1 - Encounters with Di-Baryons - From the ABC effect to a new resonance?
AU - Del Rio, Elena Perez
AU - Bashkanov, M.
AU - Clement, H.
AU - Doroshkevich, E.
AU - Pricking, A.
AU - Skorodko, T.
AU - Wagner, G. J.
PY - 2013/11/18
Y1 - 2013/11/18
N2 - The ABC effect, an intriguing low-mass enhancement in the ππ invariant mass spectrum, is known from inclusive measurements of two-pion production in nuclear fusion reactions to the few-body systems d, 3He and 4He. It was first observed 1960 by Abashian, Booth and Crowe in the inclusive pd →3He X reaction. Its explanation has been a puzzle since then. In an effort to solve this long-standing problem by exclusive and kinematically complete high-statistics experiments, we have measured the fusion reactions to d, 3He and 4He with WASA-at-COSY. These measurements cover the full energy region, where the ABC effect has been observed previously in inclusive reactions. In a recent kinematically complete measurement of the pn → dπ0π0 reaction we have shown that the ABC effect in this basic double-pionic fusion reaction is correlated with a narrow structure in the total cross section with quantum numbers I(JP) = 0(3+), a mass of 2.37 GeV and a width of about 70 MeV. The mass is about 90 MeV below 2 times the mass of δ, the mass of a δδ system, and the width is three times narrower than expected from a conventional t-channel δδ process. In the double-pionic fusion reaction to the helium isotope dd →4Heπ 0π0 again the ABC effect is observed to be correlated with the appearance of a resonance-like structure in the total cross section at the same excess energy. From a previous exclusive experiment at CELSIUS-WASA it is known that the double-pionic fusion to 3He also exhibits a pronunced ABC effect. New data from COSY on the pd →3Heπ 0π0 reaction scanning the full ABC region are presented as well as the status of measurements in other reaction channels, where the new resonance might contribute.
AB - The ABC effect, an intriguing low-mass enhancement in the ππ invariant mass spectrum, is known from inclusive measurements of two-pion production in nuclear fusion reactions to the few-body systems d, 3He and 4He. It was first observed 1960 by Abashian, Booth and Crowe in the inclusive pd →3He X reaction. Its explanation has been a puzzle since then. In an effort to solve this long-standing problem by exclusive and kinematically complete high-statistics experiments, we have measured the fusion reactions to d, 3He and 4He with WASA-at-COSY. These measurements cover the full energy region, where the ABC effect has been observed previously in inclusive reactions. In a recent kinematically complete measurement of the pn → dπ0π0 reaction we have shown that the ABC effect in this basic double-pionic fusion reaction is correlated with a narrow structure in the total cross section with quantum numbers I(JP) = 0(3+), a mass of 2.37 GeV and a width of about 70 MeV. The mass is about 90 MeV below 2 times the mass of δ, the mass of a δδ system, and the width is three times narrower than expected from a conventional t-channel δδ process. In the double-pionic fusion reaction to the helium isotope dd →4Heπ 0π0 again the ABC effect is observed to be correlated with the appearance of a resonance-like structure in the total cross section at the same excess energy. From a previous exclusive experiment at CELSIUS-WASA it is known that the double-pionic fusion to 3He also exhibits a pronunced ABC effect. New data from COSY on the pd →3Heπ 0π0 reaction scanning the full ABC region are presented as well as the status of measurements in other reaction channels, where the new resonance might contribute.
UR - http://www.scopus.com/inward/record.url?scp=84887452392&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:84887452392
SN - 1824-8039
JO - Proceedings of Science
JF - Proceedings of Science
ER -