status and perspectives Laboratory Underground Nuclear Astrophysics LUNA & LUNA-MV status and perspectives

The importance of going underground… Sun: kT = 1 keV EC ≈ 0.5-2 MeV E0 ≈ 5-30 keV for reactions of H burning kT but also E0 << EC !! Cross sections in the range of pb-fb at stellar energies with typical laboratory conditions reaction rate R can be as low as few events per month

Background reduction – HPGe detectors - gamma Cross section measurement requirem-ents Overground 3MeV < Eg < 8MeV 0.5 Counts/s 0.0002 Counts/s Underground   E<3MeVpassive shielding for environmental bck Pb Cu Secondary gammas created by m interactions are reduced underground passive shielding is more effective!

Laboratory for Underground Nuclear Astrophysics LUNA site From an idea of E. Bellotti, G. Fiorentini & C. Rolfs LUNA MV (2015->...) LUNA 1 (1992-2001) 50 kV LUNA 2 (2000…) 400 kV Radiation LNGS/surface Muons Neutrons 10-6 10-3 LNGS (1400 m rock shielding  4000 m w.e.)

LUNA 400kV accelerator E beam  50 – 400 keV I max  500 A protons I max  250 A alphas Energy spread  70 eV Long term stability  5eV/h

Hydrogen burning at LUNA 4p  4He + 2e+ + 2e + 26.73 MeV p + p  d + e+ + ne d + p  3He + g 3He +3He  a + 2p 3He +4He  7Be + g 7Be+e- 7Li + g +ne 7Be + p  8B + g 7Li + p  a + a 8B 2a + e++ ne 84.7 % 13.8 % 13.78 % 0.02 % pp chain

BBN reaction network at LUNA He 3 4 Be 7 Li H D p n 2 1 8 9 6 11 12 10 5 13 1. n p + e- + n p + n  D + g D + p  3He + g D + D  3He + n D + D  3H + p 3H + D  4He + n 3H + 4H  7Li + g 3He + n  3H + p 3He + D  4He + p 3He + 4He  7Be + g 7Li + p  4He + 4He 7Be + n  7Li + p 4He + D  6Li + g

LUNA 400 kV new program 2016-2019: a bridge toward LUNA MV 13C(a,n)16O – neutron source (LUNA MV) 12C(p,g)13N and 13C(p,g)14N – relative abundance of 12C-13C in the deepest layers of H-rich envelopes of any star 2H(p,g)3He – 2H production in BBN (feasibility test already performed) 22Ne(a,g)26Mg – competes with 22Ne(a,n)25Mg neutron source (LUNA MV) 6Li(p,g)7Be – improves the knowledge of 3He(a,g)7Be key reaction of p-p chain (LUNA MV)

13C(a,n)16O experimental status of the art Heil 2008 Big uncertainties in the R-matrix extrapolations. Presence of subthreshold resonances. A low background environment is mandatory for any new study

LUNA MV project LUNA MV accelerator will be installed in the south part of Hall C of LNGS laboratory (OPERA location) Provisionary dimensions of the hall: 27x11x5 m3 OPERA decommissioning started in Jan 2015. Should be finished by October 2016

LUNA MV Project- building and accelerator Funded by the Italian Research Ministry as a “premium project” with 5 Meuro The shielding should guarantee a neutron flux of the order of 1% of the LNGS neutron flux just outside it. Different configurations are under consideration

LUNA MV Project- Timeline Accelerator tender: Intense H+, 4He+, 12C+ e 12C++ beams in the energy range: 350 keV-3.5 MeV. One beam line with all necessary elements also included. Contract signed by 12/2015. Total budget about 3.9 Meuro: from LUNA MV Premium projects (total 5.3 Meuro)

LUNA MV- scientific program (2019 ) 13C(a,n)16O: enriched 13C solid target. Neutron detector Data taking at LUNA 400 kV in 2018. 22Ne(a,n)25Mg: enriched 22Ne gas target. Neutron detector. 12C(a,g)16O: 12C solid target depleted in 13C and alpha beam or a jet gas target and 12C beam. 12C+12C: solid state target. Gamma and particle detectors Possible commissioning measurement: 14N(p,g)15O. Solid target with known characteristics and production process. Already available HPGe detectors. High scientific interest for revised data covering a wide energy range (400 keV- 3.5 MeV) Produce scientific results of high impact but reduced risk immediately after commissioning phase.

LUNA MV- scientific program A full proposal will be submitted to LNGS-SC and to INFN within summer 2016. In the next months a final «Call for Collaborators» will be open. Next fall LUNA will start working on the new proposal

The LUNA collaboration A. Best, A. Boeltzig*, A. Formicola, S. Gazzana, I. Kochanek, M. Junker, L. Leonzi | INFN LNGS /*GSSI, Italy D. Bemmerer, M. Takacs, T. Szucs | HZDR Dresden, Germany C. Broggini, A. Caciolli, R. Depalo, R. Menegazzo, D. Piatti | Università di Padova and INFN Padova, Italy C. Gustavino | INFN Roma1, Italy Z. Elekes, Zs. Fülöp, Gy. Gyurky| MTA-ATOMKI Debrecen, Hungary O. Straniero | INAF Osservatorio Astronomico di Collurania, Teramo, Italy F. Cavanna, P. Corvisiero, F. Ferraro, P. Prati, S. Zavatarelli | Università di Genova and INFN Genova, Italy A. Guglielmetti, D. Trezzi | Università di Milano and INFN Milano, Italy A. Di Leva, G. Imbriani, | Università di Napoli and INFN Napoli, Italy G. Gervino | Università di Torino and INFN Torino, Italy M. Aliotta, C. Bruno, T. Davinson | University of Edinburgh, United Kingdom G.F. Ciani, G. D’Erasmo, E.M. Fiore, V. Mossa, F. Pantaleo, V. Paticchio, R. Perrino, L. Schiavulli, A. Valentini| Università di Bari and INFN Bari, Italy

The LUNA group in Genova Paolo Prati, 70%, Resp. Naz. e Spokesperson Sandra Zavatarelli, 20% Francesca Cavanna, 100% - AR Federico Ferraro, 100% - PhD Piero Corvisiero, 100% (0% !) – Primo LUNA SP (ed inventore della sigla…) Richieste: Travel ≈ 30 k€ Costruzione Apparati ≈ 30 k€ Manutenzione ≈ 60 k€ (di cui 50 sub judice per modifica HPGe-ULB

2H(a,g)6Li measurement - motivation The two «Lithium problems» BBN 7Li predictions are a factor 2-4 higher than observations: a nuclear physics solution is highly improbable (e.g 3He(4He,g)7Be meas. at LUNA) The amount of 6Li predicted by BBN is about 3 oom lower than the observed one in metal poor stars (debated but still «true» for a few metal poor stars) BBN predicts 6Li/7Li = 2 * 10-5 much below the detected levels of about 6Li/7Li= 5 * 10-2 Necessary to constrain nuclear physics input 2H(a,g)6Li

2H(a,g)6Li measurement - setup Strong beam induced background due to: Rutherford scattering of 4He beam on 2H target 2H(d,n)3He reaction Inelastic neutron scattering on different materials (Cu, Pb, Ge,…) g background in the 2H(a,g)6Li RoI The beam induced background weakly depends on the beam energy

2H(a,g)6Li measurement- g spectra An irradiation at one given beam energy can be used as a background monitor for an irradiation at a different beam energy, if the two ROIs do not overlap Natural background subtracted 400 keV data (grey filled) 280 keV data (red empty) rescaled to take into account the weak energy dependence of the beam induced background

2H(a,g)6Li measurement - available data Upper limits (indirect meas) No data in the BBN energy range!

2H(a,g)6Li measurement- results M. Anders et al., Phys. Rev. Lett. 113 (2014) 042501 New LUNA data From the new data on the 2H(a,g)6Li reaction: 6Li/7Li = (1.5 ± 0.3) * 10-5 Standard BBN production as a possible explanation for the reported 6Li detections is ruled out. “Non standard” physics solutions?

17O(p,g)18F measurement – available data State of the art before the LUNA measurement: Rolfs et al., 1973, prompt g SDC ≈ 9 keV b for Ecm= 100-500 keV Fox et al., 2005, prompt g discovered 183 keV resonance wg = (1.2±0.2) 10-6 eV SDC = 3.74 + 0.676E - 0.249E2 Chafa et al., 2007, activation wg = (2.2±0.4) 10-6 eV SDC = 6.2 + 1.61E - 0.169E2 larger than Fox by more than 50% Newton et al., 2010, prompt g SDC measured for Ecm = 260-470 keV Calculated SDC(E) = 4.6 keV b (±23%) Hager et al.(DRAGON), 2012, recoil separator Ecm = 250-500 keV SDC higher than Newton and Fox. No flat dependence.

17O(p,g)18F measurement - setup 183 keV resonance and direct capture component for E=160-370 keV measured with prompt gammas and activation Gamow window for Novae region explored with the highest precision to-date Enriched (70%) 17O targets on tantalum backings (anodization process)

17O(p,g)18F measurement - spectra 183 keV resonance: wg=1.67±0.12 meV (weighted average of prompt and activation) Several new transitions identified and branching ratios determined

Background reduction - Si detectors - alpha Underground+Pb vs. Overground: factor ~10-15 reduction in the range 200 keV - 2.5 MeV PRELIMINARY

1991: First Background Test in LNGS SSB Detector thickness = 2 mm

17O(p,g)18F measurement - motivation 17O+p is very important for hydrogen burning in different stellar environments: - Red giants - Massive stars - AGB - Novae - light nuclei (17O/18O/18F …) abundances - observation of 18F g-ray signal (b+ decay, annihilation with e-, 511 keV gamma) Classical novae T=0.1-0.4 GK => EGamow = 100 – 260 keV For 17O(p,γ)18F: resonance at Ep = 183 keV and non resonant contribution

17O(p,g)18F measurement - results The new reaction rate allows to calculate abundances of 18O, 18F, 19F and 15N using nova models with 10% precision D. Scott et al., Phys. Rev. Lett. 109 (2012) 202501 A. Di Leva et al., Phys. Rev. C 89 (2014) 015803

On going activities at LUNA 400 kV: 17O(p,a)14N and 18O(p,a)15N reactions In AGB stars ( T=0.03-0.1 GK ) CNO cycle takes place in H burning shell Measured 17O/16O and 18O/16O abundances in pre-solar grain give information on AGB surface composition Information on mixing processes if cross sections are well known

On going activities at LUNA 400 kV: 17O(p,a)14N and 18O(p,a)15N reactions 18O(p,a)15N 17O(p,a)14N Q = 4 MeV Two narrow resonances at 95 and 152 keV Main goals: rescan excitation function 95 keV resonance (strength and energy) Measure below 70 keV Q = 1.2 MeV Two narrow resonances at 70 and 193 keV Main goal: 70 keV resonance

On going activities at LUNA 400 kV: 17O(p,a)14N and 18O(p,a)15N reactions proton beam from LUNA 400 kV enriched 17O or 18O targets 8 silicon detectors foils of Al Mylar to stop backscattered protons low alpha particle energy (200-250 keV for 17O(p,a)14N reaction) Silicon detector Solid target position

The 17O(p,a)14N reaction: 70 keV res PRELIMINARY Very preliminary analysis favours a larger strength value compared with literature If confirmed, it would have an astrophysical impact Analysis is still ongoing

The 18O(p,a)15N reaction PRELIMINARY Data taking completed. Data analysis on going PRELIMINARY 152 keV resonance 334 keV resonance 216 keV resonance In agreement with previous data Might improve precision on resonance energy and strength 95 keV resonance strength: precision about 10% (20-30% literature) energy determined with 0.5 keV precision (2.2 keV literature) 60 keV measured with about 20% statistical uncertainty

On going activities at LUNA 400 kV: 22Ne(p,g)23Na reaction NeNa cycle of H burning. Active in astrophysical novae Impact on the abundances of: 22Ne (factor 100) 23Na (factor 7) 24Mg (factor 70)

The 22Ne(p,g)23Na reaction The “red” resonances have been directly observed for the first time For the resonances at 71, 105 and 215 keV in “black” an upper limit has been found 2 oom or more lower with respect to previous direct measurements On going BGO phase (71 and 105 res. plus DC from 200 to 360 keV)

Now “on beam”: the 23Na(p,g)24Mg and 18O(p,g)19F reactions - AGB nucleosynthesis NeNa Cycle 20Ne 23Na (p,g) (p,a) 22Na 22Ne e+n 3 yr 21Ne 21Na 22 s 19F (p, 24Mg 27Al (p, 27Si e+ 4 s 26Al 26Mg 6 s 25Mg 25Al 7 s MgAl Cycle Goal of 23Na(p,g)24Mg measurement: 144 keV resonance and DC component. BGO detector first. HPGe if feasible Goal of 18O(p,g)19F measurement: 95 keV resonance and DC component. BGO detector first, HPGe if feasible