Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

R. Thies et al.; 9 pags., 7 figs., 1 tab.
Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions. Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes. Method: We have measured projectile fragments from C10,12-18 and B10-15 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations. Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic C10,12-18 and B10-15 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well. Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study. ©2016 American Physical Society
We thank the FRS and the GSI accelerator staff for their efforts. This work was supported by the Swedish Research Council. O.T. was supported by the Spanish Research Council under project FPA2012-32443, C.A.B. acknowledges support from the U.S. DOE Grant No. DE-FG02-08ER41533 and the U.S. NSF Grant No. 1415656. L.M.F. acknowledges support by the Spanish Research Council under project FPA2013-41267-P and M.R. was supported by GSI (F&E, DR-ZUBE), German BMBF (06DR134I and 05P09CRFN5), the Nuclear Astrophysics Virtual Institute (NAVI, HGF VHVI- 417) and the Helmholtz Association Detector Technology and Systems Platform. T.K. acknowledges support by the German BMBF No. 06DA9040I, No. 05P12RDFN8, and No. 05P15RDFN1. C.W. acknowledges funding by the UK STFC No. ST/E500651/1, while N.A. and M.F. acknowledge funding by the UK STFC No. ST/F011989/1.