The Present and Future Sun & the s-Process Brian Fields U. of Illinois TALENT School, MSU, May 2014 The pp-II, pp-III Chains Other main pp chains: different 3He fate 7Be branching key: e capture rate ∼ 1000× p capture rate • 7Be: 15% of ν production • 8B ∼ 0.02% of ν production The CNOThe Cycle CNO Cycle pre-existing C, N, O act as 4p→4He catalyst + 12 (p,γ) 13 e νe 13 C → N → C (p, α) ↑↓(p, γ) + 15 e νe 15 (p,γ) 14 N ← O ← N Coulomb barriers high (Z =6, 7, 8): need high T to go 13 c ⇒ CNO cycle minor in Sun (CNO →1.6% L() > but main H-burner for M ∼ 1.5M( Testing the Nuclear-Powered Sun: Solar Neutrinos StandardSolar Solar Neutrino Neutrino Production Production Total SSM Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν 0.420 MeV 0.265 MeV 6.0 gs 7Be e→7Li ν lines: 7Li =0.861MeV;7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeV 5.8 × 10−4 Q: Why are the 7Be neutrinos monoenergetic? www: Bahcall neutrino spectrum pp neutrinos largest flux, but low energies 7 8 Be neutrinos monoenergetic, strong ∼ Tc dependence 8 20 B neutrinos continuum, ultrastrong ∼ Tc dep 2 What should this mean for production vs radius? www: Bahcall fig of production vs R StandardSolar Solar Neutrino Neutrino Production Production Total SSM Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν 0.420 MeV 0.265 MeV 6.0 gs 7Be e→7Li ν lines: 7Li =0.861MeV;7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeV 5.8 × 10−4 Q: Why are the 7Be neutrinos monoenergetic? www: Bahcall neutrino spectrum pp neutrinos largest flux, but low energies 7 8 Be neutrinos monoenergetic, strong ∼ Tc dependence 8 20 B neutrinos continuum, ultrastrong ∼ Tc dep 2 What should this mean for production vs radius? www: Bahcall fig of production vs R Standard Solar Neutrino Production Total SSM Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν Solar0.420 MeV Neutrino 0.265 MeV Production 6.0 Standardgs Solar Neutrino Production 7Be e→7Li ν lines: 7Li =0.861MeV;7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeVTotal 5.8 × SSM10−4 Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν 0.420 MeV 0.265 MeV 6.0 gs Q: Why7Be e→ are7Li theν lines:7Be 7neutrinosLi =0.861MeV; monoenergetic?7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeV 5.8 × 10−4 www: Bahcall neutrino spectrum Q: Why are the 7Be neutrinos monoenergetic? pp neutrinos largest flux, but low energies www: Bahcall neutrino spectrum 7 8 Be neutrinos monoenergetic, strong ∼ Tc dependence 8 20 B ppneutrinosneutrinoscontinuum,largest flux, ultrastrong but low energies∼ Tc dep 7 8 2 Be neutrinos monoenergetic, strong ∼ Tc dependence What8 should this mean for production vs radius?20 B neutrinos continuum, ultrastrong ∼ Tc dep www: Bahcall fig of production vs R 2 What should this mean for production vs radius? www: Bahcall fig of production vs R Standard Solar Neutrino Production Total SSM Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν Solar0.420 MeV Neutrino 0.265 MeV Production 6.0 Standardgs Solar Neutrino Production 7Be e→7Li ν lines: 7Li =0.861MeV;7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeVTotal 5.8 × SSM10−4 Flux 10 −2 −1 Rxn Eν,max = Q !Eν" Φν (10 ν cm s ) pp→deν 0.420 MeV 0.265 MeV 6.0 gs Q: Why7Be e→ are7Li theν lines:7Be 7neutrinosLi =0.861MeV; monoenergetic?7Li∗ =0.383MeV 0.47 8B→8Be e ν 17.98 MeV 9.63 MeV 5.8 × 10−4 www: Bahcall neutrino spectrum Q: Why are the 7Be neutrinos monoenergetic? pp neutrinos largest flux, but low energies www: Bahcall neutrino spectrum 7 8 Be neutrinos monoenergetic, strong ∼ Tc dependence 8 20 B ppneutrinosneutrinoscontinuum,largest flux, ultrastrong but low energies∼ Tc dep 7 8 2 Be neutrinos monoenergetic, strong ∼ Tc dependence What8 should this mean for production vs radius?20 B neutrinos continuum, ultrastrong ∼ Tc dep www: Bahcall fig of production vs R 2 What should this mean for production vs radius? www: Bahcall fig of production vs R StandardStandard Solar Solar Model Model PredictionsPredictions What are key SSM ν ingredients, predictions? • time variations: at source? in detectors? • L! fixes what? 7 8 • what connection between Φν( Be) andΦν( B)? • ν spectra: determined by what? 3 Solar NeutrinoSSM Predictions Predictions SSM Key Predictions: • at source: steady νe flux from Sun • elliptical Earth orbit → annual flux variation ∆Φν/Φν " 2δr⊕/r⊕ ∼ 4e⊕ ∼ 7% • pp flux ∼ fixed by L% 7 8 7 8 • Be, BfluxT -dep, but Φν( Be) > Φν( B) 4 • neutrino spectra fixed by β decay indep of solar model (since Tc,% ∼ 1keV & Qnuke) SolarSolar Neutrino Neutrino Experiments Experiments Original motivation (Davis, Bahcall): • confirm nuke energy generation • measure T!,c Facts of life: 1. ν →small σ < 2. Eν ∼ few MeV → large natural background e.g., radioactivity, cosmic ray muons Q: what is needed for neutrino observatory? 5 NeutrinoNeutrino Observatories: Observatories: Design Design Requirements Requirements 1. Large detector. −44 2 ν-nucleus absorption σνA ∼ 10 cm −36 −1 ⇒ event rate per target Γν(A)=ΦνσνA ∼ 10 s Solar Neutrino Unit:1SNU=10−36 event s−1 target−1 > −1 −5 −1 Want net rate R = NtargΓ ∼ 1day ∼ 10 s 31 ⇒ Need Ntarg = R/Γ ∼ 10 9 A A M = AmuN ∼ 10 g ∼ kiloton targ targ !50" !50" big! 2. Go underground. 6 “Clean” lab, low-background material RadiochemicalRadiochemical Experiments: Experiments: Chlorine Chlorine HomestakeHomestake Mine Mine:Lead, SD, USA: 1967-1995 www:– Lead, Homestake, SD 1967-1995 note Ray Davis Ray Davis target: chlorine (cleaning fluid!, 0.61 kton) 37 37 & John Bahcall process: Cl + νe→ Ar + e (endothermic) threshold: ν must supply |Q| =0.814 MeV ⇒ only measure 7Be, 8B νs procedure: cycle fluid → filter, collect 37Ar atoms: ∼ few/week! Measure: Γobs =2.56 ± 0.16 ± 0.16 SNU (1) Compare to SSM prediction: Γ obs =0.33 ± 0.03 ± 0.05 $ 1! (2) Γ 7 SSM Only see ∼ 1/3 of predicted flux! ⇒original Solar ν problem WaterWater CerenkovCerenkovˇ Experiments Experiements target: water process: electron scattering νe→νe > Infor praiseEν ∼ of0.5MeV,recoilelectron Water Cerenkovˇ ve ∼ c In praise of Water Cerenkovˇ •Indetect praise neutrinos of Water inCerenkovˇ “real time” • detect neutrinos in “real time” but in water, refactive index n =1.34 ⇒ ve > c/n • Edetecte → ν neutrinosenergyenergy →spectrumspectrum in “real time” emit• Ee “sonic→ ν boom”→ photons: Cerenkovˇ radiation • •coneEcone→ orientation orientationν energy→→→ν directionspectrumν direction info! info! “opticale shock wave,” cone of light cone orientation direction info! •cone opening angle depends→ ν on ve → Ee Super-KamiokandeSuper-Kamiokande.KamiokaMine,Japan:1996-.KamiokaMine,Japan:1996- www: Super-K image www:www: Super-K Super-K events image Super-KamiokandeSuper-K fortune cookie .KamiokaMine,Japan:1996- Super-K fortune cookie www:direction: Super-KνspointbacktoSun(check) image 9 Q: advantages of water Cerenkovˇ vs radiochemical? direction:Super-Kwww: Neutrino fortuneνspointbacktoSun(check) image cookie of the Sun www:eν elastic Neutrino scattering image in pure of the water Sun direction: νspointbacktoSun(check) eνEnergyelastic threshold: scattering 5 MeV in pure⇒ see water only 8B νs www: Neutrino image of the Sun Energyspectrum: threshold: shape matches 5 MeV SSM⇒ see only 8B νs ...but Φ(8B) /Φ(8B) ∼ 50%! 10 spectrum:eν elastic scattering shapeSK matchesSSM in pure SSM water Solar ν problem #3 8 ...butEnergyΦ( threshold:8B) /Φ(8B) 5 MeV∼⇒50%see! only B νs 10 SK SSM Solarspectrum:ν problem shape #3 matches SSM ...but Φ(8B) /Φ(8B) ∼ 50%! 10 SK SSM Solar ν problem #3 SudburySudbury Neutrino Neutrino Observatory Observatory (SNO) (SNO) Sudbury, Ontario, Canada: 1999- ultrapure heavy water: D2O Rxns: − νe + d→e + p + p Feynman diagram Charged current: νe only Threshold: 1.4 MeV → 8Bonly # νx + d→νx + p + n Feynman diagram ν# flavor = ν flavor Neutral current: all flavors Threshold: 2.2 MeV → 8Bonly 11 also: Salt phase – dissolve NaCl in SNO tank big σ for 35Cl(n, γ)36Cl → improved NC SNOSNO Results Results Charged-current (νe flux): SNO +0.08 +0.06 6 −2 −1 ΦCC = 1.59−0.07 (stat)−0.08 (sys) × 10 ν cm s (6) ! " Neutral-current (all-ν flux): SNO 6 −2 −1 ΦNC = [5.21 ± 0.27(stat) ± 0.38(sys)] × 10 ν cm s (7) Thus we have SNO ΦCC νe flux SNO = = 0.306 ± 0.026(stat) ± 0.024(sys) (8) ΦNC all ν flux 12 Which means... Implications:Implications: New New Neutrino Neutrino Physics!Physics The Sun makes only νe Q: why? e.g., why not νµ? → if no new ν physics, only νe at Earth → predict ΦCC(νe)=ΦNC(νx) SNO measures ΦCC(νe) > ΦNC(νx)! with very high confidence! non-νe flux arriving in detector! Abigdeal: • demands new neutrino physics 13 • indep. of detailed solar model Nobel Prize 2002 Ray Davis Jr., USA Masatoshi Koshiba, Japan “for the detection of cosmic neutrinos” UofI Astro Society, March 13 2007 The Future Sun Beyond the Main Sequence Main seqeunce: hydrogen burning ‣ M<1.1 Msun: pp chain Evolution of Massive Stars ‣ M>1.1 Msun: CNO in our context, massive core-collapse: M > 8 10M → ∼ − $ Main sequence: Q: what happens when Hshort exhausted MS lifetime in (< core?30 Myr) • 7 ∼ Tc 3 10 K • ∼ × burn p 4He via CNO cycle when core is all He “ash”:• → ‣ no source of thermonuclearwhen energy H exhausted: = heat homologous contraction ‣ loss of pressure support • Hshellburningbegins red giant heat core ignite..