Introduction to Experimental Nuclear Astrophysics 한인식이화여자대학교 2007 년 2 월 일 APCTP 포항

Outline Introduction –Nuclear Astrophysics –Experimental considerations Selective experiments –Nuclear reactions in the Sun –Neutrinos from the Sun Explosive environment –Nuclear reactions in supernovae –Nu-SNS Project Conclusions

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Some of the most compelling questions in nature Some of the most compelling questions in nature How were the elements from iron to uranium made? How were the elements from iron to uranium made? How does the sun shine for so many years? How does the sun shine for so many years? What is the total density of matter in the universe? What is the total density of matter in the universe? How did the stars, galaxies evolve? How did the stars, galaxies evolve? Require a considerable amount of nuclear physics information as input Require a considerable amount of nuclear physics information as input Nuclear Astrophysics

Is insufficient to explain the observed abundance Proposed O + at 7.68 MeV in 1953 Measured at 7.65 MeV in 1957

“ It is a remarkable fact that humans, on the basis of experiments and measurements carried out in the lab, are able to understand the universe in the early stages of its evolution, even during the first three minutes of its existence.” Fowler (Nobel prize 1983)

Nucleosynthesis in Cosmos 2, NNDC (BNL, 2000) 3,064 Nuclear reactions in stars produce energy generate the elements

Nucleosynthetic reactions are typically dominated by Coulomb barriers

Thermonuclear reactions in stars Gamow peak tunnelling through Coulomb barrier  exp(- ) Maxwell-Boltzmann distribution  exp(-E/kT) relative probability energy kTE0E0 E0E0

SOHO, 171A Fe emission line Nuclear Reactions in the Sun

PP-I Q eff = MeV proton-proton chain p + p  d + e + + p + d  3 He +  3 He + 3 He  4 He + 2p 86%14% 3 He + 4 He  7 Be +  2 4 He 7 Be + e -  7 Li + 7 Li + p  2 4 He 7 Be + p  8 B +  8 B  8 Be + e %0.3% PP-II Q eff = MeV PP-III Q eff = MeV net result: 4p  4 He + 2e Q eff proton-proton chain From M. Aliotta

From P. Yale Univ.

First experimental detection of solar neutrinos: 1964 John Bahcall and Ray Davis have the idea to detect solar neutrinos using the reaction: 1967 Homestake experiment starts taking data 100,000 Gallons of cleaning fluid in a tank 4850 feet underground 37 Ar extracted chemically every few months (single atoms !) and decay counted in counting station (35 days half-life) event rate: ~1 neutrino capture per day ! 1968 First results: only 34% of predicted neutrino flux ! solar neutrino problem is born - for next 20 years no other detector ! Neutrino production in solar core ~ T 25 nuclear energy source of sun directly and unambiguously confirmed solar models precise enough so that deficit points to serious problem From

Direct Coulomb dissociation ANC NaBoNA (Napoli Bochum Nuclear Astrophysics) From L. INFN

Art Champagne for ENAM04

Solar Neutrino Problem p + p  2 H + e + + e p + e - + p  2 H + e 2 H + p  3 He +  3 He + 3 He  4 He + 2p 3 He + p  + e + + e 3 He +   7 Be +  7 Be + e -  7 Li +  + e 7 Be + p  8 B +  7 Be + p   +  8 B + 2  + e SOLAR NEUTRINO PROBLEM either Solar Models are Incomplete/incorrect or Neutrinos undergo flavor changing oscillation Gallium flux = 57% SSM Chlorine flux = 34% SSM Super-K flux = 47% SSM EXPERIMENTAL RESULTS FUSION REACTIONS From P. Doe, J. Wilkerson, H. Rebertson

Sudbury Neutrino Observatory 1700 tonnes Inner Shielding H 2 O 1000 tonnes D 2 O 5300 tonnes Outer Shield H 2 O 12 m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage Urylon Liner and Radon Seal From P. Doe, J. Wilkerson, H. Rebertson

The SNO Detector during Construction From P. Doe, J. Wilkerson, H. Rebertson

Comparison of results

The Nobel Prize in Physics 2002 "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos"

Astrophysically Important Nuclear Reactions 7 Be(p,  ) 8 B 8 Li( ,n) 11 B 12 C( ,  ) 16 O 14 O( ,p) 17 F 15 O( ,  ) 19 Ne 17,18 F(p,  ) 14,15 O 25 Al(p,  ) 26 Si 44 Ti( ,p) 47 V 56 Ni(p,  ) 57 Cu 85 Kr(n,  ) 86 Kr 134 Cs(n,  ) 135 Cs …

Nuclear reactions in stars produce energy generate the elements Experimental Nuclear Astrophysics Lab studies of reaction cross-sections

A Better Set of Models for Explosive Events Hydrodynamic Properties Temperature Density Flow Etc.

Requires a Better Understanding of Nuclear Processes Unstable Isotopes Reaction rates Excited states Decay rates Bounds of Stability Proton drip-line Neutron drip-line Understanding Nucleosynthesis & Energy Generation in Explosive Events To study unstable isotopes we need radioactive beams!

Supernova Simulations First 300 ms: A. Burrows 300 km 10 km

t = 0 Neutrino-driven wind forms right after SN core collapse. n + p n +  t = 18 ms Seeds form. Exotic neutron-rich 78 Ni t = 568 ms – 1 s Heavy r-elements synthesize. SUPERNOVA R-PROCESS Otsuki, Tagoshi, Kajino & Wanajo 2000, ApJ 533, 424 Wanajo, Kajino, Mathews & Otsuki 2001, ApJ 554, 578 t = 0 Fe ○ Fe ○ Pb ○ Pb208 ○ Pb ○ Fe56 ○ Ni78 N Z

M.S. Smith and K.E. Rehm, Ann. Rev. Nucl. Part. Sci, 51 (2001) In many cosmic phenomena, radioactive nuclei play an influential role, hence the need for In many cosmic phenomena, radioactive nuclei play an influential role, hence the need for Radioactive Ion Beams 2, NNDC (BNL, 2000) 3,064

X-ray burst and novae

25 Al 24 Mg 23 Na 22 Ne 21 Ne 20 Ne 22 Na 23 Mg 24 Al 21 Na 22 Mg 19 F 18 O 21 Mg 20 Na 19 Ne 18 F 17 O 18 Ne 17 F 16 O 15 N 15 O 14 O 13 N 12 C 13 C 14 N   p  HCNO cycle CNO cycle Stable Unstable  Z N rp process

Measurements Direct measurements are desirable ways to measure the 15 O( ,  ) 19 Ne and 14 O( ,p) 17 F reactions over indirect methods. Only became possible after new generation of accelerators that can make 14,15 O and 17 F beams in the late 90’s. There are still large uncertainties of the reaction relevant to X-ray burst and novae.

O

OUTLOOK Measurements using radioactive beams have given us a deeper understanding Measurements using radioactive beams have given us a deeper understanding Big Bang, the sun, novae, supernovae Big Bang, the sun, novae, supernovae More intense radioactive RIKEN, MSU, ANL, ORNL, RIA(future) More intense radioactive RIKEN, MSU, ANL, ORNL, RIA(future) We expect to obtain more experimental results of the important reactions that are relevant to both interesting stellar sites and big bang nucleosynthesis in the future. We expect to obtain more experimental results of the important reactions that are relevant to both interesting stellar sites and big bang nucleosynthesis in the future.

U H M E P The Nu-SNS Project Ed Hungerford University of Houston

SNS is the world’s brightest intermediate energy pulsed neutrino source Nuclear Reactors SNSParticle Accelerators Energy

Right energy range Supernova neutrino spectra, 100 ms post-bounce SNS neutrino spectra spectra from the SNS are JUST RIGHT, having significant overlap with the spectra of neutrinos generated in a supernova explosion! This gives us a unique opportunity to study neutrino interactions relevant to the region of interest for Supernova spectra from nuclear reactors are TOO COLD! spectra from accelerators are TOO HOT!

U H M E P The Oak Ridge Spallation Neutron Source

U H M E P SNS Parameters Primary proton beam energy GeV Intensity  protons/sec Number of protons on the target 0.687x10 16 s -1 (1.1 ma) Pulse duration - 380ns(FWHM) Repetition rate - 60Hz Total power – 1.4 MW Liquid Mercury target 0.13 neutrinos of each flavor produced by one proton (9 x s -1 ) Number of neutrinos produced ~ 1.9  /year There is a larger flux of ~MeV anti-neutrinos from radioactive decay from the target

U H M E P Motivation for  -SNS Important Energy Window Just right for supernovae studies SN detector calibration Almost no data Extremely high neutrino flux Potential for precision measurements Can address a number of new physics issues Nuclear Physics processes Can begin with small detectors

U H M E P The SNS Layout

U H M E P Concluding Remarks  N reactions are important for supernovae  Influence core collapse  Affect shock dynamics  Modify the distribution of A>56 elements  Affects r process - nucleosynthesis  May be the dominant source of B, F, 138 La, 180 Ta  N cross sections are interesting nuclear physics  Sensitive to nuclear structure  In medium modifications of weak coupling constants  Only  + C cross sections have been measured (10%)  The SNS provides a unique opportunity to measure N cross sections at energies most relevant for supernovae and nuclear structure  Cross section measurements on 2 targets to < 10% accuracy in 1 year!  We have a strong collaboration of experimentalists and theorists: - SNS  Modest cost ~$10M  Proposal submitted DOE in early August of 2005  3 yrs required for construction (FY09-FY11)  Operations could begin by FY12 감사합니다. Thank you for your attention!