Neutrino physics and nuclear astrophysics:

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1 Neutrino physics and nuclear astrophysics: the LUNA MV project at Gran Sasso Sandra Zavatarelli, INFN - Genoa - Italy On behalf of the Luna Collaboration HEP-EPS 2017, Venice (Italy)

2 Nuclear Astrophysics Observational Astronomy Cosmology Nuclear astrophysics Nuclear Physics Neutrino Physics Stellar models

3 Neutrino production in the Sun p + p 2 H + e + + ν p + e - + p 2 H + e + + ν 3 He + p 4 He + e + + ν 7 Be + e - 7 Li + ν 8 B 8 Be + e + + ν 13 N 13 C + e + + ν 15 O 15 N + e + + ν 17 F 17 O + e + + ν p-p chain CNO cycle A. Serenelli, Eur. Phys. J. A (2016) 52: 78 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

4 Nuclear cross sections & stellar models S [MeV b ] Davids1968 Bair1973 Kellogg1989 Drotleff1993 Harrissopulos2005 Heil fits/theory Hale1987 Kubono2003 Heil C(α,n)16O Ec.m.[MeV] Many key reactions for stellar modelling are still lacking precision data!!

5 Underground nuclear astrophysics: Why? Sun: kt = 1 kev E C MeV E kev for reactions of H burning kt but also E 0 << E C!! 1 σ(e) = exp(-31.29z 1Z2 E Cross sections in the range of pb-fb at stellar energies µ/e) S(E) Astrophysical factor with typical laboratory conditions reaction rate R can be as low as few events per month

6 Laboratory for Underground Nuclear LUNA site Astrophysics LUNA 1 ( ) 50 kv LUNA MV (2015->...) LUNA 2 (2000à ) 400 kv Radiation LNGS/surface Muons Neutrons

7 LUNA 50 kv accelerator detectors

8 LUNA kV accelerator LUNA kv accelerator E beam kev I max 500 µa protons I max 250 µa alphas Energy spread 70 ev Long term stability 5eV/h

9 LUNA MV accelerator (3.5 MV) A new 3.5 MV accelerator will be installed in 2018 the north part of Hall B at Gran Sasso which is now being cleared

10 LUNA : background reduction 1,00E+00 1,00E+00 1,00E-01 1,00E-02 HPGe 1,00E-01 1,00E-02 HPGe counts 1,00E-03 1,00E-04 counts 1,00E-03 1,00E-04 1,00E-05 1,00E-05 1,00E E γ [kev] 1,00E E γ [kev] 3MeV < Eγ < 8MeV: 0.5 Counts/s 3MeV < Eγ < 8MeV: Counts/s E γ >3MeV: reduction of a factor 2000 simply going underground E γ <3MeV passive shielding Underground passive shielding is more effective since µ flux, that create secondary γ s in the shield, is suppressed. Cu Pb Shielding µ HPGe A background reduction of 5 o.o.m. was obtained at E < 3 MeV

11 25 LUNA : H burning 4p 4 He + 2e + + 2ν e MeV CNO cycle Ne-Na cycle Mg-Al cycle Reactions of interest for neutrino physics LUNA: 3 He( 3 He,2p) 4 He 3 He( 4 He,γ) 7 Be 14 N(p,γ) 15 O

12 First milestone: 3He+3He at solar energies p + p d + e+ + νe d + p 3He + γ 84.7 % 3He +3He α + 2p PP-I 3He 13.8 % +4He 7Be + γ 0.02 % % 7Be+e- 7Li 7Li + γ +νe +p α + α 7Be PP-II + p 8B + γ 8B 2α + e++ νe Suppression of 7Be and 8B νe due to a resonance? 3He+3He è p + p + 4He Q-value = MeV Neutrino less branch

13 First milestone: 3He+3He at solar energies Luna 50 kv accelerator detectors Detectors : Si array 3He+3He è p + p + 4He

14 First milestone: 3 He+ 3 He at solar energies σ min ~ 20 fb 2 events/month No resonance at the Gamow peak R. Bonetti et al., Phys. Rev. Lett. 82, (1999) 2700 J.N. Bahcall : A thrill that I had never believed possible..

15 3 He( 4 He,γ) 7 LUNA 400 kv Solar neutrinos: 7 Be, 8 B p + p d + e + + ν e PP-I d + p 3 He + γ 84.7 % 13.8 % 3 He + 3 He α + 2p 3 He + 4 He 7 Be + γ % 0.02 % 7 Be+e - 7 Li + γ +ν e 7 Be + p 8 B + γ PP-II 7 Li + p α + α 8 B 2α + e + + ν e Cross section from prompt gamma down to 90 kev (CM energy) using 4 He beam on 3 He target Off-line radioactive decay measurements of the 7 Be atoms collected in the beam catcher Before LUNA the results from the two techniques showed a 9% discrepancy

16 3 He( 4 He,γ) 7 LUNA 400 kv 3 He recirculating gas target HpGe detector in close geometry for online γ detection Removable calorimeter cap for offline 7 Be counting Si-monitor for target density measurements (beam heating effect) 0.3 m 3 Pb-Cu shield around detector chamber in OFC to reduce background on the detector Hp-Ge

17 3 He( 4 He,γ) 7 LUNA 400 kv F. Confortola et al., Phys. Rev. C 75 (2007) <S a -S p >=-0.014±0.042 Uncertainty due to S 34 on neutrinos flux: Φ( 8 B) 7.5% 4.3% Φ( 7 Be) 8% 4.6% S(E)=0.560±0.017 kev barn

18 14 N(p,γ) 15 O at LUNA 400 kv Bottle neck of CNO cycle: - 13 N and 15 O ν fluxes σ 14 ; - Globular Clusters turn-off age.

19 14 N(p,γ) 15 O at LUNA 400 kv N+p /2 + 7/2 + 5/2 + 3/2 + 3/2 - High energy: solid target + HpGe Low" energy: gas target + BGO / / O 0 1/2 - gamma spectrum of 14 N(p,γ) 15 O at Ep=140 kev

20 14 N(p,γ) 15 O at LUNA 400 kv S 1,14 (0)=1.66±0.12 kev b For a review : A. Formicola et al., Eur. Phys. J. A (2016) M. Marta et al, Phys.Rev C. 78, (R) 2008 * ½ν cno from the Sun * Globular Cluster age +0.7Gy

21 Solar metallicity and cross sections A. Serenelli, Eur. Phys. J. A (2016) 52: 78 Dominant sources of theoretical errors for solar ν fluxes. The cross section of the 14 N(p,γ) 15 O reaction is one of the main contributor in the global uncertainty on the SSM model prediction for CNO ν fluxes; Φ ν (CNO) depends on S 1,14 and (C+N) abundance in the core; Φ ν 3% => (C+N) abundance at 11% (uncertainty dominated by nucl. cross sections)

22 14 N(p,γ) 15 O at LUNA In 2016 measured by Li et al. also over a wide energy range Still a complete and clear picture is not available: A low background measurement over a wide energy range is highly desirable to reduce the present uncertainty of 7.5% on the S factor New effort : benchmark LUNA - MV Q. Li et al., Phys. Rev.C 93 (2016)

23 LUNA 400kV accelerator The LUNA-MV accelerator In-line Cockcroft Walton accelerator In the energy range MeV H + beam: eµa He + beam: eµa C + beam: eµa C ++ beam: 100 eµa Beam energy reproducibility : 10-4 * TV or 50 V The accelerator hall will be shielded by 80 cm thick concrete walls: no perturbation of the LNGS natural neutron flux

24 The scientific program for the first 14 N(p,γ) 15 O: the bottleneck reaction of the CNO cycle in connection with the solar abundance problem. Also commissioning measurement for the LUNA MV facility 12 C+ 12 C: energy production and nucleosynthesis in Carbon burning. Global chemical evolution of the Universe 13 C(α,n) 16 O and 22 Ne(α,n) 25 Mg : neutron sources for the s-process (nucleosynthesis beyond Fe) Later on 12 C(α,γ) 16 O: key reaction of Helium burning: determines C/O ratio and stellar evolution.. 5 years ( )..from H to He, and C burning

25 12C+12C 400kV impact accelerator :LUNA astrophysical Trigger of C burning 12C+12Cà 20Ne + α+ γ Q = 4.62 MeV 12C+12Cà 23Na + p + γ Q = 2.24 MeV Coulomb barrier: EC= 6.7 MeV Its rate determines the value of Mup : If Mstar>Mup: quiescent Carbon burningà core-collapse type II supernovae, neutron stars, stellar mass black holes If Mstar<Mup: no Carbon burningà white dwarfs, nova, type Ia supernovae The reaction produces protons and alphas in a hot environmentà nucleosynthesis in massive stars

26 12 C+ 12 C : measurement strategy T. Spillane PRL 2007 Several resonances spaced by kev Typical width Γ 10keV Factor 100 uncertainty in the cross section at low energy energies!!! LUNA will be able to explore the Gamow peak down to MeV Total time needed 2.5 y

27 Conclusions Nuclear astrophysics play a fundamental role in the understanding of stellar evolution, neutrino generation, supernova engine mechanism and the Big Bang The LUNA Collaboration has demontrated in 25 years of activity that the unique low background conditions of Gran Sasso is the perfect blend for the study of most of the proton capture reactions involved in the H burning; A new accelerator facility (LUNA-MV) will be installed in the Hall B of LNGS starting from 2018 and it will be devoted to the study of the key reactions of He and C burning that determine the evolution of massive stars and the nucleosythesis of most of the elements in the Universe; Thank to new facility we will be able to improve our knowledge of key reactions of H burning and of importance for solar neutrinos. Huge work in front of us but very important!!

28 LUNA 400kV accelerator Thank you for your attention!!! The LUNA Collaboration A. Boeltzig*, G.F. Ciani*, L. Csedreki, A. Formicola, I. Kochanek, M. Junker INFN LNGS /*GSSI, Italy D. Bemmerer, K. Stoeckel, M. Takacs, HZDR Dresden, Germany C. Broggini, A. Caciolli, R. Depalo, P. Marigo, R. Menegazzo, D. Piatti Università di Padova and INFN Padova, Italy C. Gustavino INFN Roma1, Italy Z. Elekes, Zs. Fülöp, Gy. Gyurky,T. Szucs MTA-ATOMKI Debrecen, Hungary M. Lugaro Konkoly Observatory, Hungarian Academy of Sciences, Budapest, 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. Best, 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. D Erasmo, E.M. Fiore, V. Mossa, F. Pantaleo, V. Paticchio, R. Perrino*, L. Schiavulli, A. Valentini Università di Bari and INFN Bari/*Lecce, Italy

29 Backup

30 The neutron source reactions for the s-process: 13 C(α,n) 16 O and 22 Ne(α,n) 25 Mg Nucleosynthesis of half of the elements heavier than Fe Main s-process ~90<A<210 Weak s-process A<~90 TP-AGB stars shell H-burning He-flash T 9 ~ 0.1 K 0.25 T 9 ~ 0.4 K cm cm C(α,n) 16 O 22 Ne(α,n) 25 Mg massive stars > 10 M Sun core He-burning shell C-burning K ~10 9 K 10 6 cm cm Ne(α,n) 25 Mg 13 C(α,n) 22 Ne(α,n)

31 LUNA 400kV accelerator The 13 C(α,n) 16 O reaction S [ M e V b ] E = kev (T = K) Davids1968 Bair1973 Kellogg1989 Drotleff1993 Harrissopulos2005 Heil2008 fits/theory Hale1987 Kubono2003 Heil2008 large statistical uncertainties at low energies large scatter in absolute values (normalization problem) unknown systematic uncertainties uncertainties in detection efficiencies contribution from sub-threshold state (E=6.356 MeV in 17 O) contribution from electron screening E c.m. [MeV] LUNA400 range No data at low energy because of high neutron background in surface laboratories. Extrapolations differ by a factor ~4 (10% accuracy would be required).

32 LUNA 400kV accelerator The 13 C(α,n) 16 O reaction at LUNA-400 and LUNA MV Direct kinematics ( 4 He beam on 13 C target): 210 kev<e cm <300 kev (275 kev<e beam <400 kev) at LUNA 400 kv 240 kev<e cm <1060 kev (300 kev<e beam <1.4 MeV) at LUNA MV 13 CH 4 gas target (drawbacks: limit on the density, possible molecule cracking). With typical conditions: atoms/cm 2 13 C enriched solid target (drawbacks: degradation, possible carbon deposition). Typically atoms/cm 2 Beam induced background: (α,n) reaction on impurities ( 10 B, 11 B, 17 O, 18 O) in the target and beam line E n = MeV 3 He counters embedded in a polyethylene matrix Inverse kinematics ( 13 C beam on 4 He target): only possible at LUNA MV 4 He gas target atoms/cm 2 Beam induced background: 13 C induced reaction on 2 H, 6 Li, 7 Li, 10 B, 11 B, 16 O, 19 F E n = MeV: same detector as above

33 LUNA 400kV accelerator 12 C+ 12 C : astrophysical impact 12 C+ 12 Cà 20 Ne + α Q = 4.62 MeV 12 C+ 12 Cà 23 Na + p Q = 2.24 MeV 12 C+ 12 Cà 24 Mg + γ Q = MeV negligible 12 C+ 12 Cà 23 Mg + n Q = MeV endothermic for low energies 12 C+ 12 Cà 16 O + 2α Q = MeV three particlesà reduced prob. 12 C+ 12 Cà 16 O + 8 Be Q= MeV higher Coulomb barrier Coulomb barrier: E C = 6.7 MeV Its rate determines the value of M up : If M star >M up : quiescent Carbon burningà core-collapse Type II supernovae, neutron stars, stellar mass black holes If M star <M up : no Carbon burningà white dwarfs, nova, type Ia supernovae The reaction produces protons and alphas in a hot environmentà nucleosynthesis in massive stars

34 12 C+ 12 C : measurement strategy Quiescent carbon burning: 0.9 MeV<E CM <3.4 MeV Type Ia supernovae: E CM 0.7 MeV 12 C+ 12 Cà 20 Ne + α i + γ i E γ = 440 kev 12 C+ 12 Cà 23 Na + p i + γ i E γ = 1634 kev Particle detection: Si or ΔE/E telescopes Gamma detection: HpGe At LUNA MV the γ natural background can be reduced by 5 o.o.m.

35 LUNA 400kV accelerator The 22 Ne(a,n) 25 Mg reaction E th = 0.57 MeV Level scheme of 26 Mg is very complex The lowest well studied resonance at E α =832 kev dominates the rate The influence of a possible resonance at 635 kev has been ruled out because of parity conservation Only upper limits (~10 pb) at: 570<E α <800 kev (energy region of interest for AGB stars) Extrapolations may be affected by unknown resonances At T 9 < 0.18 the competing reaction 22 Ne(α,γ) 26 Mg (Q=10.6 MeV) should become dominant (now measured at LUNA 400 kv) At LUNA MV: 22 Ne windowless gas target + 3 He counters inside moderator To fully exploit LNGS low background: shielded detector, selected tubes, pulse shape discrimination, remove 11 B (because of 11 B(α,n) 14 N) to reach the level of ~10 n/day.

36 LUNA 400kV accelerator The LUNA-MV time schedule Action Date Beginning of the clearing works in Hall B February 2017 Beginning of the construction works in Hall B September 2017 Beginning of the construction of the plants in the LUNA-MV building December 2017 Completion of the new LUNA-MV building and plants April 2018 LUNA-MV accelerator delivering at LNGS May 2018 Conclusion of the commissioning phase December 2018 Beginning First Experiment January 2019

37 LUNA 400kV accelerator LUNA and the others Bck. Acceler. Beam intensity Program Expected start Notes LUNA LNGS LUNA 400 JUNA ~ 2 OoM better 400 kv ECR ~300 µa 13 C(α,n) et al., 10 ma! 25 Mg(p,γ) 13 C(α,n) 12 C(α,γ) CASPAR ~ LUNA Old 1 MV 150 µa 14 N(p,γ)? 13 C(α,n) 22 Ne(α,n) LUNA MV LNGS 3.5 MV + ECR 1 ma 14 N(p,γ)? 13 C(α,n) 22 Ne(α,n) 12 C(α,γ) 12 C + 12 C 2017 Solid target Mid Gas target + 3 He tubes in liq. Scint. Mid 2016?? 2019???? Gas target + 3 He tubes

38 14 N(p,γ) 15 O & Sun metallicity