(Some) Current Topics in Nuclear Astrophysics XLIX International Winter Meeting on Nuclear Physics, Bormio, Italy January, 2011 R.E. Tribble Texas A&M University
The Origin of the Elements Observations provide picture of elemental abundance over time Baryon to Photon ratio fixes BBN – Li is an anomoly
Fate of Massive Pop III Stars White Dwarf G Collapse H G pp-I,II,III Black Hole H G CNO, rp 3a 3a->sufficient 12C?? Critical Mass Fraction of C 1E-9 (A. Heger et al. ) 1E-10 (Weiss et al. 2000) 1E-12 (Siess et al. 2002) Explode
Updated Reaction Sequences in Pop III Stars (p,g) rates known; need (a,g) rates Rap-I,II and III, substitution for 3a and CNO! (Wiescher et al., 1989)
The Origin of the Elements Observations provide picture of elemental abundance over time Quasars among oldest stars seen in universe Baryon to Photon ratio fixes BBN – Li is an anomoly
The Origin of the Elements Observations provide picture of elemental abundance over time Must understand nucleosynthesis sites and events to explain the abundances
The (radio) active Universe [22Na decay?] 1 MeV-30 MeV g-Radiation in Galactic Survey (26Al Half life: 700,0000 years) 44Ti in Supernova Cas-A Location (Half life: 60 years)
Nucleosynthesis: a multitude of mechanisms: p-p chain reactions, CNO cycle, ... 12C(p,g)13N(b+)13C 13C(a,n) H p-process s-process Capture reactions of charged particles Capture reactions of neutrons Fusion reactions between light particles Photo-dissociation reactions Radioactive decay processes electron and neutrino induced reactions at stellar temperature & density conditions!
Radiative p (a) capture at stellar energies Classical barrier penetration problem Direct radiative capture low energies Þ capture at large radii very small cross sections define astrophysical S factor:
Direct Radiative proton capture M is: Integrate over ξ: ANC Þ amplitude for tail of overlap function Low B.E.: Find:
Radiative [p(a)] Capture with resonant and subthreshold states: ANCs Capture through resonance resonance Direct capture subthreshold state Capture to ground state through subthreshold state Interference effects
Techniques to obtain reaction rates in Nuclear Astrophysics Direct Measurements (LUNA, LENA, DRAGON, . . .) Radiative widths for resonance rates* - populate resonance state and measure decay Coulomb dissociation; Knockout reactions - applications with RIBs from fragmentation Trojan Horse Method** - unique way to understand screening Asymptotic Normalization Coefficients* - stable and radioactive beams
rp-process nucleosynthesis Material accreted in binary builds up and eventually undergoes r-p process nucleosynthesis Pulsar distribution of gamma rays from r-p processing 97-98 2000
Explosive H-burning in novae: “22Na puzzle” - novae: explosive H-burning of accreting material in binaries star-WD. ~ 30/yr. - rays from the decay of long-lived isotopes like 26Al have been detected - E=1.275 MeV ray following the decay of 22Na predicted, but not observed by space gamma-ray telescopes NeNa cycle 22Na depletion in novae: how does it happen? what are the stellar reaction rates for the 22Mg(p,)23Al and 22Na(p,)23Mg?
22Mg(p,g)23Al Reaction Rate S(E) – Direct Capture reaction rate Mirror Symmetry Þ S -factor [KeV b] Reaction Rate (cm3/mole/s) EC.M [MeV] T9 (109 K) r=106 gm/cm3, T9=0.4 22Mg(p,g)23Al competes with b+ rate but photodisintegration is issue S(E) – Direct Capture reaction rate
E=207 keV => DE=16 keV 5/2+ β+ 22Mg(p,g)23Al β+ p 22Na(p,g)23Mg Tighe ea, LBL 1995 Perajarvi ea, JYFL 2000 5/2+ 23Al 0.446(4)s Qec=12240keV Proton br. total=?!% β+ 22Mg(p,g)23Al β+ ?!% 9548 8456 8164 8003 7877 p IAS: ft=2140 s +/-5% 7803 IAS 5/2+, T=3/2 7787 (7/2)+ 6985 5/2+ 6575 5/2+ 2905 (3,5/2)+ 2359 1/2+ NO! 2051 7/2+ 450 5/2+ 0 3/2+ E=207 keV => DE=16 keV 22Na Sp=7580 keV It turned out Tighe et al are wrong! Just noise! Our exp: first time the two states 7803 and 7787 keV seen in the same experiment. How is the proton decay? 22Na(p,g)23Mg resonances Most important: wg7787=__._? meV VE Iacob, et al., PRC 74, Oct. 2006 & Y Zhai thesis 23Mg 17
23Al b-delayed p-decay sp – after bkg subtraction Resonances for 22Na(p,g)23Mg Gamow window 848 566 263 206 303 1175 344 394 440 E=223 keV IAS Antti Saastamoinen et al., submitted to PRC “world record”
= studied at TAMU 32Ar 31Ar 33Ar 35Ar 34Ar 36Ar 31Cl 30Cl 32Cl 34Cl also 38Ca, 46V, 57Cu, 62Ga, … 32Ar 31Ar 33Ar 35Ar 34Ar 36Ar = studied at TAMU 31Cl 30Cl 32Cl 34Cl 33Cl 35Cl 28S 27S 29S 31S 30S 32S 33S 34S = planned 25P 27P 26P 28P 30P 29P 31P 23Si 25Si 24Si 26Si 28Si 27Si 29Si 30Si 21Al 22Al 24Al 23Al 25Al 26Al 27Al 24Mg 23Mg 22Mg 21Mg 20Mg 25Mg 26Mg 19Na 20Na 21Na 22Na 23Na 16Ne 17Ne 18Ne 19Ne 20Ne 21Ne 22Ne 14F 15F 16F 17F 18F 19F Prospects with MARS stable 12O 13O 14O 15O 16O 17O 18O used at TAMU 11N 12N 13N 14N 15N (p,n) possible 9C 10C 11C 12C 13C 14C 15C (p,2n) possible 8B 9B 10B 11B 7Be 8Be 9Be 19
r-Process Nucleosynthesis Site?? Mechanisms?? Neutrino-driven wind model Merging neutron star model (n,)-(,n) equilibrium (binding-energy) -decay properties (T1/2, Pn values) Freeze-out (neutron capture) Issues: neutron source(s); nuclear properties
Origin of seed and fuel Hydrogen Burning: 4He, 14N Helium Burning: 12C, 16O, 22Ne, n, s-nuclei Carbon Burning: 16O, 20Ne, 24Mg ... s-nuclei
22Ne(α,n) as a neutron source NACRE lower limit NACRE upper limit Present uncertainty translates into large uncertainty in s-process element production with broad consequences for explosive scenarios of nucleosynthesis such as p-process and r-process
To Do Better underground? Environmental Radioactivity Cosmic Rays background Requires multi-MeV accelerator underground – plus shielding
Neutron Induced Processes [General Considerations] Recent focus on observations in metal poor stars (early generation stars) Evidence for anamolies in nuclear synthesis versus conventional models Expect a lot of interest here in future Need new ways to obtain information for (n,2n), (n,g), ...
Properties of r-process nuclei (n,)-(,n) equilibrium (binding-energy) masses -decay properties (T1/2, Pn values) Need to produce these nuclei in the laboratory!
(Operating or Under Construction) RIB Facilities (Operating or Under Construction) Fragmentation: the path to r-process nuclei?
RIKEN RI Beam Factory (RIBF) Experiment facility To be funded In phase II Old facility Accelerator SHE (eg. Z=113) RIPS GARIS SCRIT 60~100 MeV/nucleon ~5 MeV/nucleon RILAC AVF ZeroDegree SAMURAI fRC RRC SRC SLOWRI IRC RI-ring CRIB (CNS) SHARAQ (CNS) BigRIPS <10 MeV/nucleon 350-400 MeV/nucleon New facility Intense (80 kW max.) H.I. beams (up to U) of 345AMeV at SRC Fast RI beams by projectile fragmentation and U-fission at BigRIPS Operation since 2007
Helmholtzzentrum GmbH Modular Version Helmholtzzentrum GmbH CBM APPA
NSCL to FRIB Project Manager: Thomas Glasmacher Director: Konrad Gelbke TPC estimate $614M CD-4 Range 2018-2020
T-REX [TAMU Reaccelerated Exotics]
New facilities in the U. S New facilities in the U.S. and around the world: a bright future for nuclear astrophysics!
Hot CNO Cycle and 13N(p,g)14O Na Ne F O N C 3 4 5 6 7 8 9 10 CNO Hot CNO (T9=0.2) Hot CNO (T9=0.4) Breakout Reactions Discuss after POP III http://csep10.phys.utk.edu/guidry/NC-State-html/cno.html [Precursor to rp process]
The nuclear trigger of X-ray bursts 15O(,)19Ne, 18Ne(,p)21Na Reaction rate determined by single resonance upper limit lower limit He O C Be Mg Ne 2 8 10 6 4 14 12 18 16 15O(,)19Ne as switch for XRB pattern
22Mg(p,g)23Al from 22Ne + n « 23Ne and mirror symmetry ANCs for 13C(22Ne,23Ne)12C p1/2d5/2 =0.849 ± 0.085 fm-1 p1/2s1/2 =19.2 ± 1.6 fm-1