Hope College Physics Department Research Experiences for Undergraduates Summer 2007 Project Summary

Recent studies have brought into question the structure of neutron-rich ⁷He. In an effort to contribute to this discussion, the MoNA (Modular Neutron Array) collaboration has made a measurement of the ⁷He ground state energy using MoNA at the National Superconducting Cyclotron Laboratory in tandem with a large high-field sweeper magnet and charged particle detectors. A 41 MeV/A ⁸Li beam was directed toward a beryllium target and proton stripping produced the nuclei of interest. The neutrons and ⁶He fragments resulting from the breakup of the unstable ⁷He were then detected in coincidence. From the decay energy spectrum, parameters were then extracted (E = 415 +/- 10 keV, Γ = 200 +/- 15 keV) by comparison with Monte Carlo simulations modeling a Breit-Wigner distribution with energy-dependent width that takes into account experimental acceptances and thermal background contributions. Comparing this measurement with others, the energy resolution of the experimental setup was also determined and the accuracy of the method verified.
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Publications and Presentations:
"First observation of excited states in ¹²Li", C.C. Hall*, E.M. Lunderberg*, P.A. DeYoung, T. Baumann, D. Bazin, G. Blanchon, A. Bonaccorso, B.A. Brown, J. Brown, G. Christian, D.H. Denby*, J. Finck, N. Frank, A. Gade, J. Hinnefeld, C.R. Hoffman, B. Luther, S. Mosby, W.A. Peters, A. Spyrou, and M. Thoennessen. Phys. Rev. C 81, 021301(R) (2010).

"Evidence for a Doubly Magic ²⁴O",  C.R. Hoffman, T. Baumann, D. Bazin, J. Brown, G. Christian, D.H. Denby*, P.A. DeYoung, J.E. Finck, N. Frank, J. Hinnefeld, S. Mosby*, W.A. Peters, W.F. Rogers, A. Schiller, A. Spyrou, M.J. Scott, S.L. Tabor, M. Thoennessen, and P.J. Voss*. Phys. Lett. B672, 17 (2009).

"Efficiency of the Modular Neutron Array (MoNA).”W.A. Peters, T. Baumann, G.A. Christian, D.Denby*, P.A. DeYoung, J.E. Finck, C.C. Hall*, J. Hinnefeld, A. Schiller, M.J. Strongman, and M. Thoennessen. Proceedings of the 20th International Conference of the Application of Accelerators in Research and Industry CAARI 2008, AIP Conference Proceedings 1099, 807 (2009).

"Ground Stake Energy and Width of the ⁷He from ⁸Li Proton Knockout", D.L. Denby*, P.A. DeYoung, T. Baumann, D. Bazin, E. Breitback*, J. Brown, N. Frank, A. Gade, C.C. Hall*, J. Hinnefeld, C.R. Hoffman, R. Howes, R.A. Jenson*, B. Luther, S.M. Mosby, C.W. Olson*, W.A. Peters, A. Schiller, A. Spyrou, and M. Thoennessen. Phys. Rev. C 78, 044303 (2008).

"Production of Nuclei in Neutron Unbound States via Primary Fragmentation of ⁴⁸Ca", G. Christian, W.A. Peters, D. Absalon*, D. Albertson*, T. Baumann, D. Bazin, E. BreitbachI, J. Brown, P.L. Cole*, D. Denby*, P.A. DeYoung, J.E. Finck, H. Frank, A. Fritsch*, C. Hall*, A.M. Hayes, J. Hinnefeld, C.R. Hoffman, R. Howes, B. Luther, E. Mosby*, S. Mosby*, D. Padilla*, P.V. Pancella, G. Peaslee, W.F. Rogers, A. Schiller, M.J. Strongman, M. Thoennessen, and L.O. Wagner*. Nucl. Phys. A801, 101, (2008)

" BaF Array for γ-tagged Studies with Radioactive Nuclear Beams", H. Amro, F.D. Becchetti, Hao Jing, M. Ojaruega, J.J. Kolata, B. Skorodumov, G. Peaslee, P. DeYoung, D. Denby*, and J.D. Hinnefeld. Nucl. Instr. and Meth. A579, 31, (2007).

^"7Be-Induced alpha-Transfer Reaction on ¹²C", H. Amro, F.D. Becchetti, Yu Chen, Hao Jiang, M. Ojaruega, M.J. Golobish, H.C. Griffin, J.J. Kolata, B. Skorodumov, G. Peaslee, P.A. DeYoung, P. Mears, D. Denby*, J. Brown, J.D. Hinnefeld, and A.M. Moro. Euro. Phys. Jour. 150, 1, (2007).

"Analysis of Kinematics and Decay Energy in the Breakup of ⁷He". Deborah Denby*, Paul A. DeYoung, Graham F. Peaslee, and the MoNA Collaboration. Bull. Am. Phys. Soc. 51, 52 (2006). CEU session at the Division of Nuclear Physics of the APS meeting, Poster 3A.00022, Nashville, TN, October 2006.

G. Audi et al., Nucl. Phys. A729 , 337 (2003)

F. Skaza et al., Phys. Rev. C73 , 044301 (2000).