«Ettore Majorana» International School of Subnuclear Physics Erice, 14th-23rd June 2016

Transcription

1 The 22Ne(p,γ)23Na reaction studies at LUNA Denise Piatti for LUNA collaboration University of Padua and INFN of Padua «Ettore Majorana» International School of Subnuclear Physics Erice, 14th-23rd June 2016

2 RELAX YOURSELF: THIS TALK IS EQUATIONS, TENSORS, PARAMETERS, MODELS FREE IT'S FOR EVERYBODY... BUT IF IT'S NOT THE CASE, PLEASE ASK QUESTIONS (SPEAK IN THE MICROPHONE AFTER PUSHING THE BUTTON, ONLY ONCE)!!

3 OUTLINE Why 22Ne(p,γ)23Na? Why going underground? Studies of 22Ne(p,γ)23Na reaction at LUNA Results, consequences and perspectives

4 Why the 22Ne(p,γ)23Na reaction? The NeNa cycle is active in AGB (Asymptotic Giant Branch stars), Novae It's a secondary cycle of hydrogen burning after CNO NOT IMPORTANT ENERGY CONTRIBUTION Responsible for production of isotopes Ne 24Mg ( 27Al) 20

5 Why the 22Ne(p,γ)23Na reaction? The NeNa cycle is active in AGB, Novae It's a secondary cycle of hydrogen burning after CNO NOT IMPORTANT ENERGY CONTRIBUTION Responsible for production of isotopes Ne 24Mg ( 27Al) 20 What about its rate?

6 Why the 22Ne(p,γ)23Na reaction? The NeNa cycle is active in AGB, Novae It's a secondary cycle of hydrogen burning after CNO NOT IMPORTANT ENERGY CONTRIBUTION Responsible for production of isotopes Ne 24Mg ( 27Al) SNIa 20 What about its rate? 20 Ne(p,γ)21Na the slowest reaction...but 22Ne(p,γ)23Na reaction rate is the most uncertain Poorly known contribution of resonances at astrophysical energies Three resonances still under debate LUNA ONLY upper limits from the ONLY ONE direct measurement at Ep < 400keV. Indirect experiments affected by large uncertainties. Direct Capture is unknown at low energy

7 Why the 22Ne(p,γ)23Na reaction? (2) Two mainly adopted reaction rate compilations : NACRE (1999) Iliadis et al. (2010) Discrepancy of about a factor HBB-AGB Large uncertainties affect the adopted reaction rates Different treatment of 71 and 105 kev resonances different amplitude of uncertainties Propagation of uncertainties on models predictions of isotopes abundances HBB-AGB

8 Why going underground? Reaction Rate ~ Φ(E) σ(e) de Reactions possible just in a small energy window = Gamow Peak ~ e-2 πη e-e/kt Great suppression of cross-sections ~ pb σ(e) = S(E) e-2 πη E-1 Extrapolation at low energy is on icy grounds Signal = a needle in a haystack of cosmic rays

9 Why going underground? Reaction Rate ~ Φ(E) σ(e) de Reactions possible just in a small energy window = Gamow Peak ~ e-2 πη e-e/kt Great suppression of cross-sections ~ pb σ(e) = S(E) e-2 πη E-1 Extrapolation at low energy is on icy grounds Signal = a needle in a haystack of cosmic rays What to do?

10 Why going underground? Reaction Rate ~ Φ(E) σ(e) de Reactions possible just in a small energy window = Gamow Peak ~ e-2 πη e-e/kt Great suppression of cross-sections ~ pb σ(e) = S(E) e-2 πη E-1 Extrapolation at low energy is on icy grounds Signal = a needle in a haystack of cosmic rays What to do? Laboratories at Gran Sasso, Italy: Shielding 1400 m of Dolomite rocks μ 10-6, n 10-3, γ Ne(p,γ)23Na 22 Bemmerer et al. 2005

11 LUNA LUNA 400kV Gas target Solid target

12 The 22Ne(p,γ)23Na reaction at LUNA: Germanium Phase LUNA 400kV accelerator Windowless, differentially pumped gas target PROTON BEAM 99,99 % enriched 22Ne gas at 1,5 mbar Calorimetric measure of the current Cavanna et al. (2014) Two large High Purity Germanium Detectors high resolution Two different detection angles : 55 and 90 Copper and lead shielding 3 orders of magnitude reduction of natural background at Eγ < 3 MeV

13 Germanium Phase: Results Three resonances observed for the first time Cavanna et al. (2015)

14 Germanium Phase: Results Three resonances observed for the first time For two of them excitation nuclear levels more precisely obtained Cavanna et al. (2015)

15 Germanium Phase: Results Three resonances observed for the first time For two of them excitation nuclear levels more precisely obtained New upper limits calculated for three other resonances Cavanna et al. (2015)

16 Germanium Phase: Impact New reaction rate : between previously adopted ones......but for 0,08 < T9 < 0,3 in 1σ inconsistent with Iliadis et al The new resonances contribute and the new corresponding excitation levels are responsible of the increase of the reaction rate by a factor respect to Iliadis et al at temperatures 0,12 < T9 < 0,2 Reduction of error bar: BUT: the uncertainty is still high in HBB (Hot Bottom Burning) temperature range non-resonant contribution not investigated The impact of the new reaction rate on AGB star nucleosynthesis is under study and a paper would be published on Monthly Notices of the Royal Astronomical Society 10-50

17 The 22Ne(p,γ)23Na reaction at LUNA: BGO Phase LUNA 400kV accelerator Windowless, differentially pumped gas target 99,99 % enriched 22Ne gas at 2 mbar Calorimetric measure of the current Inorganic scintillator, BGO (Z = 83, ρ = 7,13 gcm-3) high efficiency ~ 70 % (Eγ ~ 9 MeV) Large detector : cylinder Ø = 20cm and l= 28cm Six crystals sorround the gas chamber solid angle ~ 4π Indipendent signals and summed up offline

18 BGO Phase: Analysis in progress a) Pressure and temperature profiles inside the target chamber b) Calorimeter calibration Ibeam = 0,95(ΔW) - 0,76 Calorimeter A B C D E F G K1-3 c) Source Spectra BGO efficiency ROI d) Calibration spectra BGO energy calibration

19 BGO Phase: Analysis in progress e) In order to evaluate the Beam Induced Background spectra acquired with Ar as target f) Non resonant contribution measured at : Ep = 188 kev Ep = 205 kev Ep = 250keV Ep = 310 kev Ep = 360 kev In order to provide a better extrapolation of S(E) at law energies g) Define the contribution to the toatal reaction rate of the 71keV and 105keV resonance: Decrease the Germanium phase Upper Limit or in case of signal calculate the ωγ

20 Summary Studies of the 22Ne(p,γ)23Na reaction under Gran Sasso Germanium phase Three resonances observed for the first time New upper limits for 71,105 and 215 kev resonances BGO phase High sensitive study of the 71 and 105 kev resonances Measurements of the non-resonant contribution at low energies

21 LUNA collaboration INFN LNGS /GSSI, Italy: A. Best, A. Boeltzig, G.F. Ciani, A. Formicola, S. Gazzana, I. Kochanek, M. Junker, L. Leonzi HZDR Dresden, Germany: D. Bemmerer, M. Takacs, T. Szucs INFN and Università di Padova, Italy: C. Broggini, A. Caciolli, R. Depalo, P. Marigo, R. Menegazzo, D. Piatti INFN Roma1, Italy: C. Gustavino MTA-ATOMKI Debrecen, Hungary: Z. Elekes, Zs. FĘlp, Gy. Gyurky INAF Teramo, Italy: O. Straniero Università di Genova and INFN Genova, Italy: F. Cavanna, P. Corvisiero, F. Ferraro, P. Prati, S. Zavatarelli Università di Milano and INFN Milano, Italy: A. Guglielmetti, D. Trezzi Università di Napoli and INFN Napoli, Italy: A. Di Leva, G. Imbriani Università di Torino and INFN Torino, Italy: G. Gervino University of Edinburgh, United Kingdom: M. Aliotta, C. Bruno, T. Davinson Università di Bari and INFN Bari, Italy: G. D Erasmo, E.M. Fiore, V. Mossa, F. Pantaleo,V. Paticchio, R. Perrino, L. Schiavulli, A. Valentini

22 THANK YOU!