The LUNA experiment at Gran Sasso Laboratory Alessandra

The LUNA experiment at Gran Sasso Laboratory Alessandra Guglielmetti Università degli Studi di Milano and INFN, Milano, ITALY Laboratory Underground Nuclear Astrophysics Outline: -Nuclear Fusion reactions in stars: why measuring their cross section? -Why going underground to perform these experiments? -The LUNA Experiment at LNGS: recent results - On-going measurements and future perspective: the LUNA-MV project

Nuclear Astrophysics Observational Astronomy Cosmology Nuclear astrophysics Neutrino Physics Nuclear Physics Wigner contribution! Stellar models

Why studying nuclear fusion reaction cross sections? -Stars are powered by nuclear reactions -Among the key parameters (chemical composition, opacity, etc. ) to model stars, reactions cross sections play an important role - They determine the origin of elements in the cosmos, stellar evolution and dynamic - Many reactions ask for high precision data.

Element abundances in the solar system Big Bang 1 E+11 1 H Abundance relative to 106 Si 1 E+10 4 1 E+09 H-burning & He-burning He 1 E+08 a - elements Type II SN 12 16 O C 1 E+07 20 Ne 1 E+06 56 Fe 40 Ca 1 E+05 1 E+04 Fe- peak Type I SN N=82 r -process peak Type II SN 1 E+03 19 F 1 E+02 Nuclear Astrophysics ambitious task is to explain the origin and relative abundance of the elements in the Universe 1 E+01 118 Sn N=82 s- process peak AGB stars N=126 r -process peak Type II SN N=126 s- process peak AGB stars 138 Ba 1 E+00 208 195 Pt 1 E-01 Pb 232 Th 238 U 1 E-02 1 E-03 0 50 100 Mass Number 150 200 250

Neutrino production in stars p+p 2 H + e + + n p + e - + p 2 H + e + + n 3 He + p 4 He + e+ + n 7 Be + e 7 Li + n 8 B 8 Be + e+ + n 13 N 13 C + e+ + n 15 O 15 N + e+ + n 17 F 17 O + e+ + n p-p chain CNO cycle Solar neutrino puzzle: solved! Neutrino flux from the Sun can be used to study: • Solar interior composition • Neutrino properties ONLY if the cross sections of the involved reactions are known with enough accuracy

Big Bang nucleosynthesis Production of the lightest elements (D, 3 He, 4 He, 7 Li, 6 Li) in the first minutes after the Big Bang The general concordance between predicted (BBN) and observed abundances (spanning more than 9 orders of magnitude) gives a direct probe of the Universal baryon density CMB anysotropy measurements (WMAP/Plank satellites) gives an independent measurement of the Universal baryon density The concordance of the two results has to be understood in terms of uncertainties in the BBN predictions

BBN reaction network 1. 2. 3. 4. 5. 6. n p+n D+p D+D 3 H + D p + e- + n D+ 3 He + n 3 H + p 4 He + n 7 12 10 6 13 3 3 He Be 9 4 8 4 He 7 Li 11 7 6 7. p 2 D 5 3 H 8. 9. 10. 1 2 11. 12. n Li 13. + 4 H 7 Li + 3 He + n 3 H + p 3 He + D 4 He + p 3 He + 4 He 7 Be + 7 Li + p 4 He + 4 He 7 Be + n 7 Li + p 4 He + D 6 Li + 3 H Apart from 4 He, uncertainties are dominated by systematic errors in the nuclear cross sections

Nuclear reactions in stars Sun: T= 1. 5 107 K k. T = 1 ke. V<< EC (0. 5 -2 Me. V) Reaction 3 He(3 He, 2 p)4 He E 0 21 ke. V d(p, )3 He 6 ke. V 14 N(p, )15 O 27 ke. V 3 He(4 He, )7 Be 22 ke. V Cross section of the order of fb-pb at the relevant energies!

Sub-Thr resonance Extrapol. Mesurements Tail of a broad resonance Narrow resonance Non resonant process Danger in extrapolations! Resonances described using Breit Wigner formalism!

Sun Luminosity = 2 · 1039 Me. V/s Q-value ( H burning) = 26. 73 Me. V Reaction rate = 1038 s-1 Rlab= Np Nt s e Laboratory Np = number of projectile ions ≈ 1014 pps (100 A q=1+) Nt = number of target atoms ≈ 1019 at/cm 2 s = cross section = 10 -15 barn e= efficiency ≈ 100% for charged particles 1% for gamma rays Rlab ≈ 0. 3 -30 counts/year

Rlab > Bbeam induced + Benv + Bcosmic Bbeam induced : reactions with impurities in the target reactions on beam collimators/apertures Benv : natural radioactivity mainly from U and Th chains Bcosmic : mainly muons

Cross section measurement requirements 3 Me. V < E < 8 Me. V: 0. 5 Counts/s Hp. Ge 3 Me. V < E < 8 Me. V 0. 0002 Counts/s GOING UNDERGROUND E <3 Me. V passive shielding for environmental background radiation underground passive shielding is more effective since μ flux, that create secondary γ’s in the shield, is suppressed Pb Cu

Laboratory for Underground Nuclear Astrophysics LUNA site LNGS (1400 m rock shielding 4000 m w. e. ) LUNA 1 (1992 -2001) 50 k. V LUNA 2 (2000 …) 400 k. V LUNA MV (2013 ->. . . ) Radiation LNGS/surface Muons Neutrons 10 -6 10 -3

Hydrogen burning 4 p 4 He + 2 e+ + 2 e + 26. 73 Me. V pp chain p + p d + e + + ne d + p 3 He + 84. 7 % 3 He 13. 8 % +3 He + 2 p 3 He +4 He 7 Be + 0. 02 % 13. 78 % 7 Be+e- 7 Li + +ne +p + 7 Be 8 B + p 8 B + 2 + e++ ne

17 O(p, )18 F 17 O+p is very important for hydrogen burning in different stellar environments: measurement - Red giants - Massive stars - AGB - Novae 1. production of light nuclei (17 O/18 O abundances. . ); 2. observation of 18 F -ray signal (annihilation 511 ke. V). (Cygni 1992) Classical novae T=0. 1 -0. 4 GK => EGamow = 100 – 260 ke. V Resonant Contribution: 17 O(p, γ)18 F resonance at Ep = 183 ke. V and non resonant contribution

17 O(p, )18 F measurement State of the art before the LUNA measurement: Rolfs et al. , 1973, prompt SDC ≈ 9 ke. V b for Ecm= 100 -500 ke. V Fox et al. , 2005, prompt discovered 183 ke. V resonance w = (1. 2± 0. 2) 10 -6 e. V SDC = 3. 74 + 0. 676 E - 0. 249 E 2 Chafa et al. , 2007, activation w = (2. 2± 0. 4) 10 -6 e. V SDC = 6. 2 + 1. 61 E - 0. 169 E 2 larger than Fox by more than 50% Newton et al. , 2010, prompt SDC measured for Ecm = 260 -470 ke. V Calculated SDC(E) = 4. 6 ke. V b (± 23%) Hager et al. (DRAGON), 2012, recoil separator Ecm = 250 -500 ke. V SDC higher than Newton and Fox. No flat dependence.

17 O(p, )18 F measurement 183 ke. V resonance and direct capture component for E=200 -370 ke. V measured with prompt gammas and activation Gamow window for Novae region explored with the highest precision to-date Enriched (70%) 17 O targets on tantalum backings (anodization process)

17 O(p, )18 F measurement 183 ke. V resonance: w =1. 67± 0. 12 e. V (weighted average of prompt and activation) Several new transitions identified and branching ratios determined

17 O(p, )18 F results The best fit includes the contribution from the E=557 and E=667 broad resonances from literature and a constant direct capture component. Resonances described using Breit-Wigner formalism Improvement of a factor of 4 in the reaction rate uncertainty! D. Scott et al. , Phys Rev Lett 109 (2012) 202501

LUNA 400 k. V program completed under measurement reaction Q-value (Me. V) 17 O(p, )18 F 5. 6 1. 2 17 O(p, )14 N 18 O(p, )19 F 18 O(p, )15 N under measurement completed 8. 0 4. 0 23 Na(p, )24 Mg 11. 7 22 Ne(p, )23 Na 8. 8 D( , )6 Li 1. 47 Still three reactions to be measured to be completed by 2015 A new experimental program under development for 2015 -2018

LUNA MV Project April 2007: a Letter of Intent (Lo. I) was presented to the LNGS Scientific Committee (SC) containing key reactions of the He burning and neutron sources for the s-process: 12 C( , )16 O see M. Wiescher talk 13 C( , n)16 O 22 Ne( , n)25 Mg ( , ) reactions on 14, 15 N and 18 O 3 He( , )7 Be on a wide energy range to reduce uncertainty These reactions are relevant at higher temperatures (larger energies) than reactions belonging to the hydrogenburning studied so far at LUNA Higher energy machine 3. 5 MV single ended positive ion accelerator

Element abundances in the solar system Big Bang 1 E+11 Abundance relative to 106 Si Nuclear Astrophysics ambitious task is to explain the origin and relative abundance of the elements in the Universe 1 H 1 E+10 4 1 E+09 H-burning & He-burning He 1 E+08 a - elements Type II SN 12 16 O C 1 E+07 20 Ne 1 E+06 56 Fe 40 Ca 1 E+05 Fe- peak Type I SN 1 E+04 N=82 r -process peak Type II SN 1 E+03 19 F 1 E+02 1 E+01 118 Sn N=82 s- process peak AGB stars N=126 r -process peak Type II SN N=126 s- process peak AGB stars 138 Ba 1 E+00 208 195 Pt 1 E-01 Pb 232 Th 238 U 1 E-02 1 E-03 0 50 n source reactions 100 Mass Number 150 200 250

13 C( , n)16 O experimental status of the art I=200 µA, Efficiency=50% ΔETarget=10 ke. V 215 counts/h Heil 2008 @ ECM=318 ke. V Big uncertainties in the R-matrix extrapolations. Presence of subthreshold resonances. A low background environment is mandatory for any new study

22 Ne( , n)16 O experimental status of the art I=200 µA, Efficiency=50% ΔETarget=10 ke. V Jaeger 2001 90 counts/h @ ECM=678 ke. V Precise measurement of the known resonances down to the one at E = 831 ke. V to be performed at first, followed by a detailed search for unknown resonances down to E ~ 600 ke. V.

"Progetto Premiale LUNA -MV" Special Project financed from the Italian Research Ministry with 2. 805 Millions of Euros in 2012. 2. 9 Millions of Euros requested in 2013 under final evaluation Schedule: 2014 -2015 Site definition -Tender for the accelerator. Beam lines and detectors R&D 2016 Site preparation - Infrastructures 2017 Accelerator installation – Shielding- Beam lines construction- Detectors installation 2018 Calibration of the apparatus and first tests of beam on target A new collaboration is growing-up…new collaborations are highly welcome!

THE LUNA COLLABORATION Laboratori Nazionali del Gran Sasso A. Best, A. Formicola, M. Junker Helmoltz-Zentrum Dresden-Rossendorf, Germany D. Bemmerer, T. Szucs INFN, Padova, Italy C. Broggini, A. Caciolli, R. De Palo, R. Menegazzo INFN, Roma 1, Italy C. Gustavino Institute of Nuclear Research (ATOMKI), Debrecen, Hungary Z. Elekes, Zs. Fülöp, Gy. Gyurky, E. Somorjai, Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli, Italy O. Straniero Ruhr-Universität Bochum, Germany F. Strieder Università di Genova and INFN, Genova, Italy F. Cavanna, P. Corvisiero, P. Prati Università di Milano and INFN, Milano, Italy A. Guglielmetti, D. Trezzi Università di Napoli ''Federico II'', and INFN, Napoli, Italy A. Di Leva, G. Imbriani Università di Torino and INFN, Torino, Italy G. Gervino University of Edinburgh M. Aliotta, C. Bruno, T. Davinson, D. Scott