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Finding a Logo

Finding a Logo. One has to have a logo. To put where the ? Is. Vic is a famous guy, so it should be easy with GOOGLE IMAGE SEARCH!!!!. ?. ?. V 2 - Connection—The Light Elements--LiBeB. LiBeB Properties Rare, Fragile How are they made?. Not in stars—can’t survive T in stellar cores

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Finding a Logo

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  1. Finding a Logo One has to have a logo. To put where the ? Is. Vic is a famous guy, so it should be easy with GOOGLE IMAGE SEARCH!!!! ?

  2. ?

  3. V2- Connection—The Light Elements--LiBeB • LiBeB Properties • Rare, Fragile • How are they made? • Not in stars—can’t survive T in stellar cores • Spallation reactions in stellar winds at surface of T Tauri Stars? • Energies—up to 50 MeV? Aha!! We had a 50 MeV cyclotron at MSU

  4. What We Measured • p + C, N, O Ne  Li Be B, Products low energy • Need only masses 6,7,9,10,11—one isotope of each mass stable on cosmic timescales. • Measure E/v2 E t2  mass At MSU-Laumer, Davids, Panggabean, SMA, to 45 MeV At Maryland- Roche, Clark, Mathews, Moyle, Glagola, V2, to 100 MeV

  5. 12C + p 10 s(mb) GCR--p,  Splat! ISM target 6Li stuff The Results and Cosmic Ray Production Summarized by SMA and, better, by SM Read and V2, ADNDT 31, 1984 T Tauri flares now out as production site, cosmic rays in. Cosmic ray production Make too little 7Li, 11B => other sources: Big Bang and Supernovae?

  6. a + a6,7Li Collaboration Can synthesize 6,7Li before C,N,O made in stars is returned to the interstellar medium. Measurements at U Maryland, IUCF, and MSU, beginning in 1975 and ending in 2001, most of them collaborative, provide quality estimates over the entire interesting range. ???

  7. WMAP  Li Spite Plateau Li B B 6Li Be Log (Li,Be,B)/H 10 10 0 0 - - now now - - 3 3 [Fe/H] [Fe/H] Abundances in Metal Poor Stars and CR Nucleosynthesis Comments and mysteries Li mostly BB, some CR so almost constant. But too low. Stellar destruction? 6Li all CR, so should increase—doesn’t ? B,Be increase linearly-means our classic CR picture is wrong? Many explanations, perhaps too many explanations. Nuclear physics is almost good enough.

  8. a+a  8Be + a12C(7.65) res res 12C (g.s.) +2γ(e+e-) Making Carbon in Stars Triple alpha reaction--a venerable topic Saltpeter, Opik, Hoyle: 3a -> 12C in helium burning stars Efficiency requires a double resonance process • New Interests—effects of 3a in: • SNII (Iron core size, nucleosynthesis) • AGB Stars (Carbon production and carbon stars) • Limits on variation of atomic constants • How to improve (inadequate) 3a accuracy? 12% ->  5%?

  9. I Q1= -92 keV a + a II Gp Q2= -287 keV a +8Be Gg The Triple Alpha Process • Step I: a+a  8Be • Resonant process • Form equilibrium abundance of 8Be • Step II:8Be + a12C(7.65) If resonant, as for our applications: r3aGrad(7.65)e-Q/kt Grad =Gg+Gp , Q = Q1+Q2

  10. ( ) G + G G g p G = G + G = G g p p rad G G p Each arrow a measurement  Ý Ý Ý Experiments 5 3 2 5 Excluded results 1 0 0 0 How Well Do We Know r3a 2 – 3M . a r

  11. How Well Do We Have to Know r3a? • Comments: • Several measurements for all parameters • Generally good agreement • Result is soundly based. • Is it good enough? Some examples • Core collapse supernovae • Competition with following reaction 12C(a,g)16O crucial • Ratio of two rates important at 10% level (Woosley et al) • At 10% level in ratio, r3a needs to be better known • Low mass AGB stars • 12C produced depend strongly on r3a, need better accuracy, to 5% or better.

  12. Heger, Woosley, Boyes 25 M Production Factor 12C(a,g)16O Multiplier SNII Nucleosynthesis A=16-40 Explosion of 25 M star Vary rate of 12C(a,g)16O All else same Production Factor “Same” PF for 1.2 x standard 12C(a,g)16O rate

  13. 25 M Heger, Woosley, Boyes Fe Core Size (Solar Masses) 0.5 1.0 1.5 2.0 1.0 1.5 2.0 2.5 12C(a,g)16O Multiplier(xBuchmann `96) SNII--Pre-collapse Fe Core Size • Pre-supernova evolution • 25 M star • Vary rate of 12C(a,g)16O • Fe core mass changes by 0.2 M over the interesting range • Important? • Naively, yes. If homologous core mass constant, need 3 x 1051 erg to dissociate extra 0.2 M to nucleons Caveat: Is it just the ratio that counts?

  14. Asymptotic Giant Branch Stars Following core H,and He burning thermal flashes in He shell induce convective currents that carry C rich material into the inter-shell region. Then to the convective envelope. Convects to stellar surface, blown off star by strong winds. This 3rd dredge-up Brings 12C to stellar surface, contributes strongly to galactic nucleosynthesis Karakas, et al.

  15. Low 14N(p,g) High 3a Results-NACRE Rates (Falk Herwig and SMA) Results We need to know rates better: Changes to error limits make nearly factor of 2 changes in C/O.

  16. + G G g p G G G Emphasis on and p G p Improving the Triple Alpha Reaction Rate Reminder: G + G G g p G G = + G = G g p p rad G G p  Ý Ý Ý % RATE uncertainty 2.7 9.2 6.4 1.2 (T8 = 2) • From seven consistent exp’ts • Hard to improve. • GOOD ENOUGH Q known to ± 0.2 KeV, from: Er to ± 0.2 KeV (Nolen & Austin (76)--incorrect in tabulations); Ma to ± 0.06 eV) GOOD ENOUGH

  17. 0+ 7.65 MeV (e,e’) Gp 0+ g.s. Measuring Gp • Using electron scattering • Gprelated to cross section for exciting 7.6 MeV state at small momentum transfer q. • Use ratio of elastic and 7.6 MeV form factors, extrapolate to q=0. • Two measurements • Crannell,et al., Strehl: • Gp =60.5 ± 3.9 meV NEW: H. Crannell Based on analysis of all (?) extant data (unpublished): Gp = 52.0 ± 1.4 meV

  18. Top View PM PM Beam Beam PM PM PM PM Side View Liner Liner PM PM Plastic Plastic 12C Target Scint Scint Measuring Gp / G • A hard measurement: Branch is small ~6 x 10-6 • Nevertheless, the three measurements, two from BNL, one from MSU are consistent: 6.74 ± 0.62 (9.2%) New measurement: WMU,MSU WMU Tandem,(p,p’) at 135o, 10.56 MeV (strong resonance for 7.65 state) Gp / G = (#-pairs/#-7.65 protons) Aim: ± 5% accuracy

  19. It was fun trying to figure out where the light elements come from and what they can tell us about the cosmos. But did you come to East Lansing for the physics or for the Free Style Shop? It’s Been Good to Meet Again

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