Candidate for the Double Gamow–Teller Giant Resonance in ⁴⁸Ca Studied by the (¹²C, ¹²Be(0⁺₂)) Reaction at 250 MeV/Nucleon

Abstract

A new experimental method to search for the double Gamow-Teller giant resonance using the double charge exchange (¹²C, ¹²Be(0⁺₂)) reaction is proposed and applied, for the first time, to a ⁴⁸Ca target at 250 MeV/nucleon using a ¹²C primary beam at the RIKEN RI Beam Factory. The events with double isospin- and spin-flip in ⁴⁸Ca were selected by measuring decay γ -rays from ¹²Be(0⁺₂). A forward-peaking component in the measured double-differential cross sections was observed with an integrated 0◦ cross section of 1.33 ± 0.12 μb/sr in the excitation energy region below 34 MeV in ⁴⁸Ti. Reaction analyses based on distorted-wave Born approximation calculations and the multipole decomposition based thereon indicate that ∼40% of the forward-peaking component originates from the double Gamow-Teller transitions. The transition strength of the double Gamow-Teller transition is evaluated from the extracted forward-peaking cross section.