Nuclear Data Needs for r- Process Calculations Bradley Meyer Clemson University

Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998) An appropriate astrophysical model of events significant for nucleosynthesis. (“Appropriate” does not necessarily = “correct”!) An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable. The dependency of the value of the observable on the value of a nuclear cross section. An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.

R-Process Observables Production of heavy elements: –Neutron-to-seed ratio (~100) –Dependent on nuclear reactions at T 9 > 4 Details of final abundance distribution –Peaks –Freezeout abundances—smoothing –Dependent on nuclear reactions for T 9 <3

Appropriate Model? Which regime? Low-entropy r-process High-entropy r-process High-entropy, fast expansion r-process

Production of heavy nuclei in the first place (n/s~100) Depends on weak interaction physics—electron capture rates, neutrino-nucleus interaction rates Quasi-equilibrium: nuclear masses and partition functions Three-body reaction rates (α+α+α  12 C, α+α+n  9 Be and 9 Be+α  12 C+n Charged-particle reactions on proton-rich isotopes for the high-entropy, fast expansion regime

Meyer and Wang (2007)

Production of 4 He from n, p (T 9 = 10 – 8 )

Production of 4 He from n, p (T 9 < 8 ) Too few heavy nuclei  neutrons and protons don’t assemble into alpha particles and heavier species  many free neutrons and protons around to bombard the few heavy nuclei present

Meyer and Wang (2007)

Details of the Final R-Process Abundances Depends on: –Nuclear masses –Neutron-capture cross sections –Beta-decay rates –Spins and partition functions –Fission yields

Reference calculation

Neutron-capture cross sections

Beta-decay rates

Spins and Partition Functions

Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998) An appropriate astrophysical model of events significant for nucleosynthesis. (“Appropriate” does not necessarily = “correct”!) An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable. The dependency of the value of the observable on the value of a nuclear cross section or other nuclear property. An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.

What is libnucnet? A C toolkit for storing and managing nuclear reaction network. Built on top of libxml (the gnome XML parser and toolkit) and gsl (the GNU scientific library). Released under the GNU General Public License.

History of libnucnet Original goal—online nucleosynthesis tool Problem—input over the web Solution—XML (eXtensible Markup Language) Libxml as input and output Libxml has powerful built-in data structures (lists, hashes, trees, etc.)—build new nucleosynthesis code on top of libxml Hashes provide easy access to data— particularly useful for experimentalists

Features of libnucnet Intrinsically 3-d Easily handles arbitrary nuclear network (bbn to r- process), including (any number of) isomeric states Reactions are handled the way humans think about them: “c12 + he4  o16 + gamma” or “o15  n15 + positron + neutrino_e” Hierarchically structured Naturally uses xml as input (allows for schemas, stylesheets, xpath selection, etc.) Read and validate data across the web Allows for user-supplied screening and NSE correction factor functions.

Structure of libnucnet Libnucnet__Nuc.c/h: a collection of nuclei –Libnucnet__Species: a species –Libnucnet__Nuc: a collection of species Libnucnet__Reac.c/h: a collection of nuclear reactions –Libnucnet__Reaction: a reaction –Libnucnet__Reac: a collection of reactions Libnucnet.c/h: a network and a collection of zones –Libnucnet__Net: a Libnucnet__Nuc + Libnucnet__Reac –Libnucnet__Zone: a physical zone –Libnucnet: a network plus a collection of zones

XML Data for the nuclear collection 0 1 Tuli (2000) …

XML Data for the nuclear collection (with states) Tuli (2000) + Gupta and Meyer (2001) Tuli (2000) + Gupta and Meyer (2001) ,,,

XML Data for Reactions—a rate table Smith et al. (1993) h1 n h2 gamma E … ….

XML Data for Reactions—a single rate Nuclear Data tables o19 f19 electron anti-neutrino_e e-01

XML Data for Reactions—a non- smoker fit ADNDT (2001) 75, 1 (non-smoker) ne15 n ne16 gamma e e e e e e e e e+01

Zone data …

Where we’re headed Release of libnucnet 0.3 imminent Put network code based on libnucnet on line this fall My research with libnucnet –Study nuclear network equilibria (NSE, QSE, etc.) –Build a multi-zone Galactic chemical evolution network on top of libnucnet.

Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998) An appropriate astrophysical model of events significant for nucleosynthesis. (“Appropriate” does not necessarily = “correct”!) An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable. The dependency of the value of the observable on the value of a nuclear cross section or other nuclear property. An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.