Hydrogen and Helium burning under Gran Sasso Carlo BrogginiINFN-Padova

Men in pits or wells sometimes see the stars…. Aristotle

Stellar Energy+Nucleosynthesis : σ(Estar) with Estar << ECoulomb

Why and how underground

Helium burning

The proton-proton chain: 3He burning in the Sun andsolar neutrinos

Hydrogen burning in AGB stars and classical Novae

The bottleneck reaction of the CNO cycle

Nuclear reactions bw Z1Z2: potential energy due to Coulomb force: Z1Z2e2/R≈1.44•Z1Z2/R MeV (R nuclear radius R1+R2 in fermi)

When the classical turning point is much larger than the nuclear

radius: σσσσ(E) = S(E) e–2πηπηπηπη E-1

E is the CM energyS(E) is the astrophysical factor2πη=31.29•Z1Z2(µ/E)1/2

where µ is the reduced mass in amu and E is in keV

Narrow resonance at E=ER (virtual state in the compound nucleus):

σσσσ(E)÷÷÷÷ΓaΓb / [(E-ER)2+(Γ/2)2]

with Γ=Γa+Γb

Γa (Γb ) is the partial width for the formation (decay) of the compound state

The charged particle width Γa is ruled by the transmission probability through the Coulomb barrier (at very low energy much smaller than Γγ))))

Reaction Rate(star) ÷÷÷÷ ∫ΦΦΦΦ(E) σσσσ(E) dE

Gamow Peak

MaxwellBoltzmann

Extrap. Meas.

σσσσ

Background due to cosmic rays:

- Electromagnetic component- Hadrons- Muons: ionization, spallation,

radioactive nuclei, neutrons- Mu-stop: radioactive nuclei- Gamma rays

In 1979 A. Zichichi makes a proposal to the ItalianParliament for building a large underground laboratory inside the highway tunnel underneath the Gran Sasso.

In 1982 the Parliament approves the construction, then completed in 1987.

In 1989 the first underground experiment, MACRO, is starting data taking.

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are needed to see this picture.

Surface: 17 800 m2

Volume: 180 000 m3

Ventilation: 1 vol / 3 hours

Muon flux: 3.0 10-8 cm-2s-1

Neutron flux, mainly from (αααα,n) : 2.92 10-6 cm-2s-1 (0-1 keV)0.86 10-6 cm-2s-1 (> 1 keV)

Rn in air: 20-80 Bq m-3

Background due natural radioactivity (γ rays):238U (609, 1120, 1764, 2204 keV…), Radon (t1/2 3.8 days)232Th (911, 969, 2615 keV…)40K (1461 keV from E.C. decay 10.5% B.R.)

Large Cu+Pb shielding possible underground (no muon activation)

10-4

10-3

10-2

10-1

100

101

102

103N

orm

alis

ed c

ount

ing

rate

[d-1

keV

-1kg

-1]

Energy [keV]0 1500500 1000 2000 2500 3000

above groundARC SeibersdorfVKTA RossendorfJRC-IRMMLNGS

BGO spectrum

External Lab, 10 cm Pb

Underground

At E˃3.2 MeV γ rays are

from (n,γ) reactions

Voltage Range: 50-400 kVOutput Current: 1 mA (@ 400 kV) Absolute Energy error: ±300 eVBeam energy spread: <100 eVLong term stability (1 h): 5 eVTerminal Voltage ripple: 5 Vpp

Voltage Range:1 - 50 kV

Output Current:1 mA

Beam energy spread:20 eV

Long term stability (8 h):10-4

Terminal Voltage ripple:5 10-5

Resonance?

Hydrogen burning in the Sun@15*106 degrees:

6*1011 kg/s of H He+0.7% MH E

activation=prompt gamma

σ at low energy with 4% error

2H burning in proto-stars @106 degrees

3He (3He,2p)4He

Q = 12.86 MeV

Epmax= 10.7 MeV

Suppression of 7Be and 8B

νe due to a resonance?

σmin=20 fb (2 events/month)No resonance at the Gamow peak

Neutrino oscillations

3He(α,γ)7Be

BBN 7LiSolar Neutrinos:7Be,8B

Q=1.6 MeV

•Cross section from prompt gamma down to 90 keV (CM energy) using 4He beam on 3He target•Activation via off-line radioactive decaymeasurements of the 7Be atoms collected in the beam catcher•All with a final error < 5 %

Activation measurement

o 4He beam @ 350 keVo <I> ~ 230 µAo Recirculated 3He @ 0.7 mbar

T½ =52.2±±±±1.5 d

Prompt γγγγ-spectra

o 4He beam @ 400 keVo <I> ~ 300 µAo Irradiation time: 4.4d

o 4He beam @ 220 keVo <I> ~ 240 µAo Irradiation time: 24.4d

σ down to 93 keV7Be ≈ prompt γS34(0) = 0.567 ± 0.018 keV b

recommended value 0.56 ± 0.02 (expt) ± 0.02 (theory)

0,45

0,47

0,49

0,51

0,53

0,55

0,57

80 100 120 140 160 180

Ecm [keV]

S(E

) [k

eV b

]

activation-PRL+PRC

activation

on-line

νcno Φ ∼∼∼∼ S1,14

Globular Cluster Age

S(0)=3.5-1.6+0.4 keV b (Ad98)

S(0)=3.2-0.8+0.8 keV b (An99)

AgeCluster=F(£turnoff)

£turnoff=F(S1,14)

RedBlue

turnoff

£

Surface colour

13C(p,γ)

14N

(p,γ)

15O

β+

(p,α)12C

(p,γ)

13N

β+

15N

The CNO Cycle

- 504

-21

278

14N+p

72977556

7276

68596793

6176

5241

5183

015O

1/2 +

7/2 +

5/2 +

3/2 +

3/2 -

5/2 +

1/2 +

1/2 -

“High” energy: solid target + HpGe

gamma spectrum of 14N(p,γγγγ)15O at Ep=140 keV

10-7 mbar 10-6 mbar 10-4 mbar

0.5-2 mbar

Windowless gas-targetMax 10 mbar

Low energy: gas target + BGO

Reaction Rate = 10.95 ± 0.83 counts/dayBackground rate = 21.14 ± 0.75 counts/day

∆t = 49.12 daysQ = 927±7 C

beam energy: 80 keV

*½ννννcno from the Sun * Globular Cluster age +1Gy

* more C at the surface of AGB

From a measurement of ννννcno from the Sun

St(0)=1.57±0.13 keV b

Solar composition problem:Z/X ~0.024 ~ 0.018SSM predictions disagreewith Helioseismology results

ννννcno=f(Z,S14), ~30% decrease from high to low metallicity

Metallicity of the Sun core (C+N)Photosphere and core metallicity equal?Correlation with the high C+N of giant planets?

LUNA beyond the Sun: isotope production in the hydrogen burning shell of AGB stars (~30-100 T6), Nova nucleosynthesis (~100-400 T6) and BBN

2H(α,γ)6Li Q=1.47 MeV

15N(p,γ)16O Q=12.13 MeV

17O(p,γ)18F Q=5.6 MeV

23Na(p,γ)24Mg Q=11.7 MeV

22Ne(p,γ)23Na Q=8.8 MeV

18O(p,γ)19F Q=8.0 MeV

25Mg(p,γ)26Al Q=6.3 MeV

............

17O(p,α)14N Q=1.2 MeV

18O(p,α)15N Q=4.0 MeV

Uncertainty on 16O, 17O, 18O, 18F and 19F less

than 10% (from 40-50%)

The Ne-Na Cycle

22Ne(p,γ)23Na Q=8.8 MeV

Only upper limits (µeV) on the strength of the 14 possible resonances below 400 keV (factor 2000 on the rate)

Ne, Na, Mg and Al yield in AGB and Novae (up to a factor 100)

The strength of 5 resonances measured in the first 3 months of the experiment with a neV sensitivity

25Mg(p,γγγγ)26Al Q=6.3 MeV

Production of 26Algs in H-burningregions is less efficient than

previously obtained

First measurement of the 92 keV

resonance: ωγ=(2.9±0.6)x 10-10 eV

26Al T½ = 0.7 My:Nucleosynthesis is still active

Big Bang Nucleosynthesis

Possible nuclear explanation of the 6Li problem?

The 6Li problem: in some very old stars 6Li/7Li measured(from the asymmetry of the 7Li absorption line) ~5*10-2, BBN predicted ~10-5

6Li source: D(α,γ)6Li, measured only down to 711 keV (BBN production below 400 keV)

D(α,γ)6Li Q=1.47 MeV

~3He(α,γ)7Be set-up(similar Q-value) but…

important γγγγ backgrounddue to (n,n’ γ)γ)γ)γ) on Ge, Cu,Fe…..

E1E2

A.M. Mukhamedzhanov et al., 2011

F. Hammache et al., 2010

LUNA results, 2014

J. Kiener et al., 2010

P. Mohr et al., 1994

BBN predictions with LUNA results:6Li/7Li =(1.5±0.3)*10-5, no nuclear solution

R.G.H. Robertson et al., 1981

12C(αααα,γγγγ)16O the most important reaction ofnuclear astrophysics: production of the elements heavier than A=16, star evolution from He burning to the explosive phase (core collapse and thermonuclear SN) and ratio C/O

Sources of the neutrons responsible for the S-process: 50% of the elements beyond Iron

(αααα,γγγγ) on 3He, 14N, 15N, 18O……

What Next: 3.5 MV accelerator mainly devoted to Helium-Burning (in stars: ~100 T6, ~105 gr/cm3)

LUNA-MV accelerator financed by MIUR, to be installed in Hall C of LNGS (Opera space)

22Ne(αααα,n)25Mg: isotopes with A‹90 during He and C burning in massive stars

13C(αααα,n)16O: isotopes with A≥90 during AGB phase of low mass stars

3He(α,γ)7Be:

14N(p,γ)15O: σ down to 70 keV

νcno reduced by ∼ 2 with 8% error Sun core metallicityGlobular cluster age increased by 0.7-1 GyMore carbon at the surface of AGB stars

3He (3He,2p)4He: σ down to 16 keVno resonance within the solar Gamow Peak

, cross section measured with 4% error7Be ≈ prompt γγγγ

25Mg(p,γ)26Al: first measurement of the 92 keV resonance,

strength ωγ=(2.9±0.6)x 10-10 eV

15N(p,γ)16O: σ down to 70 keV, reduced by ∼ 2

D(α,γ)6Li: no nuclear solution to the 6Li problem

17O(p,γ)18F: rate uncertainty @ Novae temperature reduced to 5%

uncertainty on 18O, 18F and 19F less than 10% (from 40-50%)

Future: Hydrogen and Helium burning (3.5 MV accelerator)

LUNA CollaborationINFN - LNGS (Italia): A. Best, A. Formicola, S. Gazzana, M. Junker, L. Leonzi, A. Razeto

HZDR (Germania): D. Bemmerer, T. Szücs, M. Takács

INFN Padova (Italia): C. Broggini, A. Caciolli, R. Depalo, R. Menegazzo

INFN Roma La Sapienza (Italia): C. Gustavino

ATOMKI, Debrecen (Ungheria): Z. Elekes, Zs.Fülöp, Gy. Gyurky, E.Somorjai

Osservatorio di Collurania (Italia): O. Straniero

Ruhr-Universität Bochum (Germania): F. Strieder

University of Edinburgh (UK): M. Aliotta, T. Davinson, C. Bruno

Università di Genova (Italia): F. Cavanna, P. Corvisiero, F. Ferraro, P. Prati

Università e INFN Milano (Italy): A. Guglielmetti, D. Trezzi

Università e INFN Napoli (Italia): G. Imbriani, A. Di Leva

Università e INFN Torino (Italia): G.Gervino