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HK: Fachverband Hadronen und Kerne

HK 72: Nuclear Structure and Dynamics II

HK 72.3: Talk

Thursday, March 19, 2009, 17:15–17:30, H-ZO 50

Isospin symmetry in the A=12 system using both beta decay and M1 gamma decays — •martin alcorta¹ and the 12c-kvi collaboration² — ¹Instituto de Estructura de la Materia, CSIC, Madrid, Spain — ²KVI Rijksuniversiteit Groningen, Zernikelaan 25 9747 AA Groningen, the Netherlands

The A=12 isobars provide an excellent system for testing isospin symmetry. The Gamow-Teller strength to states in ¹²C populated in the β decays of ¹²B and ¹²N can be directly compared. By using the parallels between the Gamow-Teller operator and the operator for M1 γ transitions this isospin symmetry can also be tested in the T₃=0 member of this isospin triplet.

We have precisely measured the branching ratios to unbound states in ¹²C populated in the β decay of both ¹²B and ¹²N by implanting these nuclei in a segmented Si detector at KVI, Groningen. By studying the ¹⁰B(³He,pααα) reaction in complete kinematics we were able to observe M1 γ decay of the 15.11 MeV T=1 IAS of the ¹²B and ¹²N ground states to the same unbound states populated in the β decays. This allows us to improve the values of the overall branching ratios of the γ decay of the T=1 15.11 MeV state. The results from these two experiments gives us a complete picture of branching ratios of the decay from the A=12 isospin triplet leading to an improved test of the isospin symmetry. In this contribution we will present our results on the γ branching intensities from the 15.11 MeV state and the β decay transition rates of ¹²B and ¹²N and compare these to state-of-the-art calculations.