1. Production of elements near the N = 126 shell in hot fusion- evaporation reactions with 48 Ca, 50 Ti, and 54 Cr projectiles on lanthanide targets Dmitriy A. Mayorov Texas A&M University Cyclotron Institute

2. 2 2 1. reduction in P CN for reactions with 50 Ti and beyond on actinide targets Motivation for Present Work A. K. Nasirov et al., Phys. Rev. C 84, 044612 (2011). Picture courtesy of Superheavy Elements Group, GSI 2. how will the predicted closed shell character of Z = 120, N = 184 and the correspond shell correction energy affect production cross section for elements 119 and 120? P CN Ratio ( 48 Ca → 50 Ti) ≈ 10 ( 48 Ca → 54 Cr) ≈ 49

3. 3 3 Previous Research: Reduced Survival Probabilities of Weakly Deformed Nuclei 4 He + 226 Ra → 230 Th * 18 O + 208 Pb → 224 Th * 48 Ca + 172, 173, 176 Yb → 212, 213, 216 Th * 16 O + 206 Pb → 222 Th * 40 Ar + 176, 178, 180 Hf → 216, 218, 220 Th * P. Armbruster, Reports on Progress in Physics 62, 465 (1999). C. C. Sahm et al., Nucl. Phys. A 441, 316 (1985). Calculation excluding collective enhancements Calculation excluding shell effects Calculation including collective enhancements and shell effects

4. 4 4 Schematic Depiction of Collective Enhancements R. Junghans et al., Nucl. Phys. A 629, 635 (1998) V. I. Zagrebaev et al., Phys. Rev. C 65, 014607 (2001) CN β 2 < 0.15 β 2 > 0.15 Fission Saddle Point Neutron Emission CN β 2 ≈ 0.15+ β 2 > 0.15 Fission Saddle Point Neutron Emission fade-out with increasing E * modeled by:

5. 5 5 N = 126 Reaction Systems of Interest A. Sobiczewski and K. Pomorski, Prog. Part. Nucl. Phys. 58, 292 (2007).

6. 6 K500 Cyclotron MARS – Momentum Achromat Recoil Spectrometer 6 R. E. Tribble et al., Nucl. Instrum. Meth. A 285, 441 (1989). C. M. Folden III et al., Nucl. Instrum. Meth. A 678, 1 (2012).

7. 7 Production of 4n EVR in 48 Ca + 162 Dy relative to 54 Cr + 162 Dy upper limits are at an 84% confidence interval pxn evaporation channels are more prominent for neutron-deficient nuclei theoretical calculations based on the statistical codes of the NRV group D. Vermeulen et al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984).

8. 8 8 Production of 4n EVR in 48 Ca + 162 Dy relative to 54 Cr + 162 Dy ≈ 7100 without collective enhancements with collective enhancements Separation between the dashed curves if primary accounted for by the differences in B f -B n (≈ 6 MeV) B n and B f determine the magnitudes of  n  and  f, which determines p sp (E * ) Fade-out is an exponential function of E *, which is affected by B n along the de-excitation cascade ≈ 4 ≈ 270 W. J. Swiatecki et al., Phys. Rev. C 78, 054604 (2008).

9. 9 9 Production of 4n EVR in 50 Ti + 159 Tb Collective enhancements become more pronounced P CN rough estimate based on: Preliminary excitation function for 50 Ti + 159 Tb CN: 210 Rn (N = 124) CN: 209 Fr (N = 122) CN: 216 Th (N = 126) D. Vermeulen et al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984). C. C. Sahm et al., Nucl. Phys. A 441, 316 (1985). K. Siwek-Wilczynska et al., Int. J. Mod. Phys. E 17, 12 (2008). P CN ≈ 0.5 P CN ≈ 0.25 P CN ≈ 0.1* Phenomenological Formula: 48 Ca + 162 Dy/ 50 Ti + 159 Tb 1.7 48 Ca + 162 Dy/ 54 Cr + 162 Dy 3.4

10. 10 MARS – Momentum Achromat Recoil Spectrometer Ongoing Improvements to Experimental Set-Up MCP Rotating Wheel Target K150 Hi-Temp Oven T. Loew et al., IEEE Particle Accelerator Conference, 2963 (2007).

11. 11 Concluding Remarks Previous authors recognized the impact that collective enhancements may have on SHE synthesis. In the present experimental effort: ~ a systematic investigation of projectile on reaction cross section is of interest ~ the behavior of collective enhancements in these systems is of importance Further data needed to deduce systematic trends/behavior Use of more detailed theoretical analysis At present, the current theoretical predictions of the production cross section of tens of fb for 120 seems most reliable.

12. 12 Acknowledgements Special Thanks To: Group Cyclotron Institute Staff NRV Group of JINR (especially A. V. Karpov) Funding: DoE under award numbers DE-FG02-93ER40773 and MUSC09- 100 Welch Foundation under grant number A-1710