Nuclear Astrophysics with fast radioactive beams Hendrik Schatz Michigan State University National Superconducting Cyclotron Laboratory Joint Institute for Nuclear Astrophysics JINA Outline: rp-process r-process

Neutron star (H and He burn into heavier elements) Companion star (H + He envelope) Accretion disk (H and He fall onto neutron star) Accreting neutron stars X-ray bursts Superbursts Bursts and other nuclear processes probe M,R, cooling  dense matter EOS, superfluidity, meson condensates, quark matter strange matter

Precision X-ray observations (NASA’s RXTE) Need much more precise nuclear data to make full use of high quality observational data Galloway et al Woosley et al astro/ph Uncertain models due to nuclear physics Burst models with different nuclear physics assumptions  GS burst shape changes ! (Galloway 2003 astro/ph ) Reality check: Burst comparison with observations

Nuclear physics needed for rp-process: some experimental information available (most rates are still uncertain) Theoretical reaction rate predictions difficult near drip line as single resonances dominate rate: Hauser-Feshbach: not applicable Shell model: available up to A~63 but large uncertainties (often x x10000) (Herndl et al. 1995, Fisker et al. 2001)  Need radioactive beam experiments  -decay half-lives masses reaction rates mainly (p,  ), ( ,p) (ok – but corrections needed) (in progress) (just begun) (various methods, ISOL and fast beams)

33 Ar 32 Cl + p Shell model calculation: 3.56 MeV 7/ MeV 5/2 + Ground state Dominate rate in rp-process H. Schatz New experimental techniques at NSCL applied to 32 Cl(p,g) 33 Ar Herndl et al gs keV  (~ 2.6 MeV)  (1.359 MeV) predicted level experimentally known level Experimental Goal: Measure excitation energies of the relevant states

Focal plane: identify 33Ar S800 Spectrometer at NSCL: Plastic target Radioactive 34 Ar beam 84 MeV/u T 1/2 =844 ms (from 150 MeV/u 36 Ar) 33 Ar 34 Ar SEGA Ge array (14 Detectors) Beam blocker H. Schatz Setup for 34Ar(p,d)33Ar measurement 34 Ar 34 Ar(p,d) 33 Ar*

x10000 uncertainty shell model only  -rays from predicted 3.97 MeV state Doppler corrected  -rays in coincidence with 33Ar in S800 focal plane: 33 Ar level energies measured: 3819(4) keV (150 keV below SM) 3456(6) keV (104 keV below SM) 33 Ar level energies measured: 3819(4) keV (150 keV below SM) 3456(6) keV (104 keV below SM) H. Schatz reaction rate (cm 3 /s/mole) temperature (GK) x 3 uncertainty with experimental data stellar reaction rate New 32 Cl(p,  ) 33 Ar rate – Clement et al. PRL 92 (2004) 2502 Typical X-ray burst temperatures

Burst peak (~7 GK) ~ 45% Energy ~ 55% Energy Carbon can explode deep in ocean/crust (but need x10 enhancement) (Cumming & Bildsten 2001) (Schatz, Bildsten, Cumming, ApJ Lett. 583(2003)L87 crust made of Fe/Ni ? Heavy nuclei in rp-ashes Disintegration can be main source of energy ! Increased opacity leads to correct ignition depth H. Schatz Ashes to ashes – the origin of superbursts ?

r (apid neutron capture) process Supernovae ? n driven wind ? prompt explosions of ONeMg core ? jets ? explosive He burning ? What is the origin of about half of elements > Fe (including Gold, Platinum, Silver, Uranium) Neutron star mergers ? graph by J. Cowan H. Schatz The r(apid neutron capture) process) Abundance Observations Nuclear Physics + Abundance Observations  only direct experimental constraint on r-process itself Nuclear Physics

Pt Xe 78 Ni, 79 Cu first bottle necks in n-capture flow ( 80 Zn later) 79 Cu: half-life measured 188 ms (Kratz et al, 1991) 78 Ni : half-life predicted 130 – 480 ms 3 GSI (Bernas et al. 1997) Ni

H. Schatz Some recent r-process motivated experiments GSI (in-flight fission) Half-lives, Pn values (Schatz, Santi, Stolz et al.) ISOLDE (ISOL) Decay spectroscopy (Dillmann, Kratz et al. 2003) GSI (in-flight fission) Masses (IMS) (Matos & Scheidenberger et al.) GANIL (fragmentation) Decay spectroscopy, Sorlin et al. ANL/CPT (Cf source) (Clark & Savard et al.) Remeasured masses with high precision ORNL (ISOL) (d,p) and Coulex MSU/NSCL (fragmentation) Half-lives, Pn values “Fast beam experiments”

NSCL Neutron detector NERO R-process Beam Si Stack neutron 3 He + n -> t + p Measure:  -decay half-lives Branchings for  -delayed n-emission Measure:  -decay half-lives Branchings for  -delayed n-emission Detect: Particle type (TOF, dE, p) Implantation time and location  -emission time and location Neutron-  coincidences Detect: Particle type (TOF, dE, p) Implantation time and location  -emission time and location Neutron-  coincidences H. Schatz First experiment: r-process in the Ni region (Hosmer et al.) ~ 100 MeV/u

Energy loss in Si ~ Z r-process nuclei Time of flight ~ m/q Particle Identification: time (ms) Total 78 Ni yield: 11 events in 104 h 77Ni 78Ni 75Co 74Co 73Co

P. Hosmer H. Schatz Preliminary results 78Ni half-life (11 events) Half-life (s) Mass number Ni half-lives as a function of mass number – comparison with “global” models

H. Schatz Impact of 78 Ni half-life on r-process models  need to readjust r-process model parameters

Known half-life NSCL covers large fraction of A<130 r-process big discrepancies among r-process models possibility of multiple r-processes First NSCL experiments completed H. Schatz NSCL and future facilities reach Rare Isotope Accelerator (RIA) Experimental Nuclear Physics + Observations  Experimental test of r-process models is within reach  Vision: r-process as precision probe

H. Schatz Conclusions Interesting time in Nuclear Astrophysics where observations and experiments zoom in on most extreme (but common) scenarios Need a complementary approach to nuclear astrophysics need a variety of experiment types for a wide range of data need a variety of facilities (ISOL and fragmentation beams, and stable beams too !) need experiment and nuclear theory to: fill in gaps correct for astrophysical environment understand nuclear physics A range of nuclei in the r- and rp-process are now accessible at the NSCL Coupled Cyclotron Facility. Need a next generation radioactive beam facilities such as RIA or FAIR to address most of the nuclear physics relevant for astrophysics. Fundamental questions to be answered: The origin of the elements Properties of matter under extreme conditions.  Collaboration

Collaboration MSU: P. Hosmer F. Montes R.R.C. Clement A. Estrade S. Liddick P.F. Mantica C. Morton W.F. Mueller M. Ouellette E. Pellegrini P. Santi H. Schatz M. Steiner A. Stolz B.E. Tomlin Mainz: O. Arndt K.-L. Kratz B. Pfeiffer Notre Dame: A. Aprahamian A. Woehr Maryland: W.B. Walters PNNL P. Reeder H. Schatz Collaborations MSU: R.R.C. Clement D. Bazin W. Benenson B.A. Brown A.L. Cole M.W. Cooper A. Estrade M.A. Famiano N.H. Frank A. Gade T. Glasmacher P.T. Hosmer W.G. Lynch F. Montes W.F. Mueller P. Santi H. Schatz B.M. Sherrill M.-J. van Goethem M.S. Wallace Hope College P.A. DeYoung G.F. Peaslee r-process rp-process