Status of the A56 64 and 68 Xray

Status of the A=56, 64, and 68 X-ray burst waiting points Zach Meisel 2016 Ohio University Workshop on Experiments for X-ray Burst Nucleosynthesis Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 1

X-ray counts/second rp-process reaction sequence & waiting points W. Lewin et al. SSRv 1993 56 Ni 64 Ge 68 Se 72 Kr H. Schatz et al. PRL 2001 100 Sn Z Reaction sequence: 3α→HCNO→αp-process →rp-process N Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 2

Waiting point mechanism 120 20 WP Z N Caused by: - low Q-value (easily establish p, γ–γ, p equilibrium) - long half-life (~seconds) Also impacted by p, γ rate on waiting-point proton-capture daughter. Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 3

56 Ni waiting-point H. Schatz et al. PRL 2001 Courtesy of W. Ong Z N Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 4

56 Ni waiting-point: Measured key resonance energies S 800 Spectrograph (recoil detection) Coupled Cyclotrons (58 Ni beam) GRETINA (in-flight γ) Production Target (Be) A 1900 Fragment Separator W. Ong et al. Submitted to Phys. Rev. C (2016) CD 2 target C. Langer et al. Phys. Rev. Lett. (2016) Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 5

Conclusion: 56 Ni stalls the rp-process …but may be bypassed at high ρ, T W. Ong et al. Submitted to Phys. Rev. C (2016) Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 6

64 Ge waiting-point Calculations by C. Langer 64 Ge + 2 p-capture flow uncertain • 65 As mass measured by X. L. Tu et al. Phys. Rev. Lett. 2011 …but relatively large uncertainty (~90 ke. V) remains & systematic bias possibly present • Penning trap mass measurement planned M. Eibach & Z. Meisel NSCL approved expt. e 15026 (≤ 10 ke. V uncertainty expected) • 66 Se mass still needed Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 7

68 Se waiting-point H. Schatz et al. PRL 2001 Z N Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 8

68 Se waiting-point: Measured key Q-value Coupled Cyclotrons A 1900 Fragment Separator Production Target Beta-counting Station Radiofrequency Fragment Separator M. del Santo, Z. Meisel, et al. Phys. Lett B 2014 Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 9

Events detected Conclusion: 68 Se substantially stalls the rp-process Events detected Proton energy [ke. V] Ep = M 69 Br - M 68 Se Proton energy [ke. V] X-ray flux M. del Santo, Z. Meisel, et al. Phys. Lett B 2014 Before expt. After expt. *qualitative conclusion agrees with A. Rogers et al. Phys. Rev. Lett. 2011 Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 10

Summary of waiting-point nuclei status • 56 Ni: • • • Flow through 56 Ni is weak --> strong waiting point [C. Langer et al. Phys. Rev. Lett. 113, 032502 (2014)] • But, a by-pass is possible (need more nuclear data) W. Ong et al. Submitted to Phys. Rev. C (2016) 64 Ge: • Flow from 64 Ge depends on 65 As mass [M. Eibach & Z. Meisel NSCL approved expt. e 15026] (Uncertainty will remain from 66 Se mass) 68 Se: • 68 Se is a strong waiting-point (<13% flow through) [M. del Santo, Z. Meisel, et al. Phys. Lett. B 2014] (Could be stronger, depending on 70 Kr mass) 72 Kr: • Will be investigated similar to 68 Se [A. Rogers NSCL approved expt. e 12024] 100 Sn: • Need t 1/2 [D. Bazin et al. PRL 2008] • Improved half-life would help Z N H. Schatz et al. PRL 2001 *but other reactions also significantly affect the rp-process flow & therefore XRB light-curve + ash composition (R. Cyburt et al. Submitted to Astrophys. J. 2016) Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 11

Thanks to: Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 12

Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 13

The current value for ME(65 As) may be systematically incorrect • There is some evidence which suggests the previous ME(65 As) measurement may have been systematically biased to an over-bound value IMS-SR mass measurement fit residual: IMS-SR mass measurement TOF spectra: highest frev reference 65 As 67 Se 71 Kr Residual for 2012 AME X. L. Tu et al PRL 106, 112501 X. L. Tu et al. NIM A 654, 213 (2011 Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 14

65 As half-life also points to more negative proton separation energy (i. e. less-bound 65 As) Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 15

If ME(65 As) were less bound, this could resolve the ‘coulomb-shift anomaly’ • Systematic overestimating of binding by Tu et al. could cause fp-shell ‘Coulomb-shift anomaly’ X. L. Tu et al. J. Phys G 41 025104 (2014) Coulomb shift trend in fp-shell: Superimpose linear trend: (expected from charged-sphere approximation) (540 ke. V) (shift required to achieve linearity) 67 Se-67 As 71 Kr-71 Br (480 ke. V) 75 Rb (125 ke. V) (250 ke. V) 65 As-65 Ge 63 Ge-63 Ga 75 Sr- 69 Br-69 Se 71 Kr-71 Br 67 Se-67 As 65 As-65 Ge 59 Zn-59 Cu 61 Ga-61 Zn 57 Cu-57 Ni X. L. Tu et al. J. Phys G 41 025104 (2014) Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 16

Rogers et al. 2011 & del Santo et al. 2014 may agree Status of the A=56, 64, and 68 XRB waiting-points Zach Meisel 17