1. Energy production in the Sun: • Solar fusion reactions• The "solar-neutrino problem"

2. The 7Be(p,γ)8B reaction• Direct (p,γ) measurements• Indirect methods

3. Coulomb dissociation of 8B • Pro's and Con's of the method• The GSI experiment• Comparison to other results

4. The solution of the "solar-neutrino problem"• Results from SNO and other neutrino detectors

5. Outlook

Klaus Sümmerer, GSI Darmstadt (Germany)

Coulomb dissociation of 8B and the "solar-neutrino problem"

Coulomb-dissociation experiments of astrophysical interestEnergy production in the Sun: the p-p chain

net result: 4p a + 2e+ + 2ve + 26.7 MeV

plus small contribution by CNO-cyle (≈ 1.5%)

highenergy

neutrinos!

Coulomb-dissociation experiments of astrophysical interestSolar neutrino spectra and detection methods

detection methods:

12 3

1,2:radiochemical(cumulative)detection

3:real-timedetection

Radiochemical ν-detection: The Homestake Cl experiment

The Homestake-Mine chlorine experiment by

Ray Davis and collaborators (1968 bis 2001):

νe+37Cl → 37Ar (T1/2=35 d)+e-

680 t liquid CCl4

located in Homestake Gold-Mine (USA)

(1.5 km below surface)

flush Ar every 100 days

Production: ~0.5 atoms/day

Measured: 2.56 ±0.16(stat) ±0.16(syst) SNU

Predicted: 8.5 ± 0.18 SNU

(Standard Solar Model, Bahcall et al. 2004):

→ only 30% of the predicted flux!

1 SNU (Solar Neutrino Unit) =

1 νe-capture/(1036 atoms of 37Cl∙s)

Is this prediction reliable?

Radiochemical ν-detection: The Gallium experiments

Gallium-based radiochemical experiments:

SAGE, GALLEX

νe + 71Ga → 71Ge (T1/2=11.4 d) + e-

SAGE: 60 t liquid Ga metal (Baksan, Russia)

GALLEX: 30.3 t Ga in GaCl3-HCl solution

Gran Sasso underground laboratory (Italy)

(1.3 km below surface)

Flush liquid with N2, convert GeCl4 into GeH4Result: 70.8±4.5(stat)±3.8(syst) SNU

Predicted: 131 SNU (BP04)

→ only 55% of predicted flux!

GALLEX

Realtime ν-detection: (Super-) Kamiokande

1) Kamiokande (700 t of water, 1983 -1996)

2) Super-Kamiokande (50 kt of water, since 1996)

in Kamioka Mine, Japan (~1 km below surface)

Elastic neutrino scattering from electrons:

νe + e- → e- + νe

(11146 photomultipliers with 50 cm each)

→ Cherenkov – radiation

→ information on direction and energy

Energy threshold: ~ 5 MeVResult: 2.35 ±0.02(stat) ±0.08(syst)×106 cm-2s-1

Prediction: 5.8 ± 1.3×106 cm-2s-1

→ only 40% of the predicted flux !

Sun

The "solar-neutrino problem"

Possible solutions to these solar-neutrino problems:

1) The standard solar model is wrong

or

2) Something is happening to the e-neutrinos between creation in the Sun and

detection on Earth

Cl H2O Ga

Can we trust the Standard Solar Model (SSM)?

Ingredients:

•Measured solar properties:

Radius,Mass,Luminosity,Distance,

Chemical surface composition,

Surface oscillation frequencies,....

•Thermal equilibrium

•Nuclear theory of solar-fusion reactions

•Best estimate for nuclear cross sections

R = 700 000 km

T = 5800 K

Important ingredient for high-energy (8B) neutrino detection:

low-energy cross section of the 7Be(p,γ)8B reaction!

Desired precision: ± 5%!

The low-energy 7Be(p,γ)8B cross section

Thermal fusion in the Sun occurs far below the Coulomb barrier!

C.M. energy of Gamov peak:

E0 = 1.22 (Z12Z2

2∙T62)1/3 keV

p+7Be in the Sun: E0 = 16 keV

S-factor:S=Ecm x σ/exp(-2πη)η=Z1Z2e2/(ћv)

for p+7Be: S17

cross sections σ(Ecm)

p+7Be

The low-energy 7Be(p,γ)8B cross section

7Be (t1/2 = 53 d):Long-lived enough to make a target, but:7Be target areal density: ≈ 10 g/cm2

p intensity: 10 A = 6∙1013/s L ≈ ∙ 5∙1031 cm-2 s-1 large: detection!

0 keV

769

M1E1

137

2+

1+

3/2-

s,d

8B7Be+p

p,f

8Be*

2 αM1 resonant capture

E1 non-resonant capture

769 – 137 = 632 keVProblems with direct-proton-capture:

small cross sections at low Ecm

problems with absolute normalization sensitive to dE/dx at low energies

History of the astrophysical S17 factor

J. BahcallNucl. Phys. B 118 (2003) 77

www.sns.ias.edu/~jnb/

S-factor S17 from modern proton-capture experiments

Up to 2003, all recent S17-results seemed to agree within errors

Can we cross-check these results with an alternate method?

In 2003, the Seattle group (Junghans et al.) published a new dataset with much smaller error bars and a higher S17(0)

Alternate method: Coulomb dissociation

8B

7Be

p

Baur, Bertulani and Rebel (1986):

measure 8B+γ 7Be + p

instead of 7Be + p 8B+γcross sections are related by detailed balance!

virtual-photon spectrum(Weizsäcker-Williams)

detailed balance

σγp = 4/5 k2/kγ2 σpγ kγ = (Ecm+Q)/ћc

k2 = 2μEcm/ћ2

k2/k2 ≈ 1000

dσCD/dEcm = 1/Ecm dnγ/dEcm σγp

virtual photons fromhigh-Z target(best at relativistic energies, 200-500 A MeV)

Pro's and Con's of the Coulomb-dissociation method

Pro CD: Two fast charged particles in exit channelDifferent systematic errors than low-energy direct p-captureMethod applicable also to short-lived nucleiPhase-space factor enhances cross sections

Contra CD:bad cm-energy resolutiondnγ/dEcm depends on multipolarity!Nuclear contribution?Higher-order effects?

Best CD results

for:

CD works best for low Q, high Ecm! Small nuclear, large CD contribution Small higher-order effects

Multipolarity contribution to Coulomb dissociation

Example: 7Be (p,γ)8B

Direct p-capture:

S17(0) is dominated by E1

virtual-photon spectrum:

large number of E2 photons

E2 may play a role!

(theory: ~5-10% effect)

Overview over Coulomb-dissociation experiments of 8B

Author Lab EnergyYear

published

Motobayashi et al.

RIKEN 46.5 A MeV 1996

Kikuchi et al. RIKEN 52 A MeV 1998

Iwasa et al. GSI 254 A MeV 1999

Davids et al. MSU 83 A MeV 2001

Schümann et al.

GSI 254 A MeV 2006

SIS

SIS FRS ESR

KaoS

degrader

production target 9Be, 8 g/cm2

Plastic (TOF-Start)

8B, 254 MeV/u

PPACs(TOF-Stop)

208Pb-target 52 mg/cm2

12C, 353 MeV/u

The GSI 8B Coulomb-dissociation experiment:Preparation of the 8B beam

Analyzing incident 8B and outgoing p and 7Be at the spectrometer "KaoS"

Si microstrip detectors (SSD): pitch 100 μm; identify p,7Be,8B; measure θ17

Magnetic spectrometer KaoS: measure pp,pBe

construct invariant mass from θ17, pp, pBe

Reference: F.Schümann et al., Phys. Rev. C 73 (2006) 015806.

track incoming 8B

Identification of p and 7Be in Si Strip detectors

cou

nts

en ergy loss [M eV ]

He

7Bep

8BIdentification of p,7Be,8B:energy loss in SiStrip detectors

back-ground free measurement!

x

y SSD1/SSD2 SSD3/SSD4

Z

vertex region

target p

7Be17

z-vertexposition

p and 7Be from breakup in Pb target:vertex reconstruction

Results(1): Scattering angles Θ8

.

E1 multipolarity gives perfect fit to data E1+E2 deviates for large θ8

1. nuclear overlap? introduce absorptive potential

2. E2-contribution?

In-plane protonangular distributions: cm

E1-E2 interference? p-7Be angular correlationsResults(2): p-7Be angular correlations

Compare to two theoretical

approaches:

1. first-order perturbation theory

2. dynamical QM-calculation

θcm distributions are symmetric:

E1 describes data sufficiently well!

Results(3): Energy-differential cross sections

Conversion to S factor:• compare exp. and simulated bin contents• adjust S17(E1,theor.) S17(exp)

M1 component:• taken from Filippone et al. (1983)• GEANT simulation to take into account experimental resolution

theoretical prediction:experimental cross sections

S17-factors from Coulomb Dissociation experiments

.

GSI:254 A MeVE1 only

Kikuchi/RIKEN:51 A MeVE1-only

Davids/MSU:83 A MeVE2 componentsubtracted

S17-factors from Coulomb Dissociation experiments

.

Comparsion to S17-factors from (p,γ) experiments

GSI-2:

S17(0) = 20.6 ± 1.5 eV barn

Best fit to Seattle data:S17(0) = 21.5 ± 0.6 eV barn

Very good agreement with (p,γ) data!

Comparison with proton-capture S17 factors

Accepted (p,γ) value from 2009Seattle workshop:S17(0) = 20.9 ± 0.7 eV barn

In certain cases, CD is a useful tool to measure radiative-

capture cross sections.

It works best at high energies (300-500 A MeV).

The 7Be(p,γ)8B reaction is an ideal case: Dominant E1

multipolarity, low Q-value.

We found convincing evidence for a negligible E2

contribution.

The GSI CD experiment agrees very well with the best (p,γ)

experiment. Direct-proton capture seems still to provide more

precise results.

S17 is no longer the largest uncertainty in solar-model

predictions of the 8B solar neutrino flux.

Conclusions from 8B Coul.Diss. experiment

The final solution to the solar-neutrino problems:ν-oscillations

In 2002, the Sudbury Neutrino Observatory (SNO) published direct evidence for e-neutrino flavor oscillations.

More papers from the Sudbury Neutrino Observatory (SNO) have confirmed the earlier results.

The KAMLAND experiment in Japan has directly measured reactor-antineutrino oscillations.

The BOREXINO experiment in Italy has measured the solar 7Be neutrino flux.

Cherenkov detector

1100 t D2O (99.92%)

9456 photomultiplier tubes (20 cm each)

fiducial volume, surrounded by 1700 t H2O

outer volume: 5300 t H2O

2 km below surface near Sudbury, Canada

Aim: Measuring the total v flux

including

τ, μ and e neutrinos!

Neutrino-flux measurements by the Sudbury Neutrino Observatory (SNO, Canada)

Direct neutrino detection in the SNO detector

Charged current interaction:

CC: e + d → p + p + e-

sensitive only to e

Elastic scattering

ES: x + e- → x + e-

mainly sensitive to e

Neutral-current interaction:

NC: x + d → p + n + x

sensitive to all flavors

New: neutrons detected by 3He

counters!

How SNO can detect other neutrino flavors

The SNO results for the 8B solar neutrino flux

experimental total v-flux from the Sun

predicted total v-flux

8B solar neutrino fluxes: SNO experiment vs. SSM calculations

Standard Solar Model solar-neutrino flux: Recent changes (J.N. Bahcall and M.H. Pinsonneault, PRL 92 (2004) 121301)

New 7Be(p,γ) cross section from Seattle exp. increases Φtheo by 15%

New solar-surface composition increase error on Φtheo to ±23%

Φtheo = 5.79 (1 ± 0.23) 106 n/cm2/s

Experimental solar neutrino flux:(B.Aharmin et al., PRL 101 (2008) 111301)

Best value from SNO

Φexp = 5.54 (1 ± 0.09) 106 n/cm2/s

KamLAND: Detecting the disappearance of reactor antineutrinos

KamLAND

ve + p n + e+

KAMLAND results

prompt energy spectrum ve survival probability

L0 = 180 km

7Be neutrinos: Borexino at Gran Sasso (Italy)

Elastic scattering: x + e- → x + e-

recoil e-: < 665 keV

requires ultra-low background!

Result: counts/(day·100 tons)

Exp.: 43 ± 3(stat) ± 4(syst)

Predicted: 48 ± 4 (with ν oscill.)

74 ± 4 (without ν oscill.)

7Be862 keV line

PRL 101, 091302 (2008)

Neutrino oscillation parameters

B.Aharmim et al., PRL 101 (2008) 111301

Confidence limits from SNO

Confidence limits from SNOplus all other neutrino experiments

without withKamLAND

Outlook: Nuclear Physics

All solar-fusion reactions were discussed during an "expert meeting" in Seattle in January 2009, following a similar meeting in 1998.

The low-energy cross section of the 3He(4He,γ)7Be reaction (i.e. S34) has been remeasured with better accuracy.

There is little chance to improve the nuclear-physics input. E.g.:

S34(0) = 0.56 ± 0.02 ± 0.02 keV b

old value:

S34(0) = 0.53 ± 0.05 keV b

3He + 4He

Outlook: Neutrino Physics

Many experiments are under way to elucidate certain aspects of neutrino physics:

Tokai-to-Kamiokande (T2K, Japan): Shoot a μ-neutrino beam from Tokai to the Super-Kamiokande detector (295 km).Look for e-appearance in Super-Kamiokande.

CERN-to-Gran Sasso (CNGS, Europe): Shoot a μ-neutrino beam from CERN to the a detector at Gran Sasso (730 km). Look for τ-appearance at Gran Sasso (OPERA, ICARUS)

exciting results to be expected!

Muchisimas gracias...

to Frank Schümann, Fairouz Hammache, Stefan Typel,

Naohito Iwasa, Peter Senger and the KaoS collaboration for

performing and analyzing the 8B experiment,

to Tom Aumann for lending me many neutrino slides from his

habilitation talk,

to I.Duran, D.Cortina, J.Benlliure and the nuclear-physics

group at USC for very generous hospitality,

to you for your kind attention!

Helioseismology

Pressure waves at the solar surfacecan be detected by Doppler shiftsof optical emission lines sound speeds inside the Sun.

Bahcall's SSM can reproduce themeasured sound speeds to a

remarkable accuracy!

SNO can distinguish between neutrino interactions

Anisotropy

Energy spectrum

direction

Super-Kamiokande: Atmospheric Neutrinos

e-like neutrino

s

Monte-Carlo calculations

assuming → oscillations

μ-like neutrino

s

Advantages of high incident energies

E1 contribution is maximized

higher-order corrections are minimized

S. Typel

GSI: 254 MeV/nucleon

Correction for feeding of excited state in 7Be

In Coul.Diss., the 1st excited state in 7Be can be fed.

This feeding has been measured at RIKEN and reproduced by a calculation by S. Typel.At low Erel, its contribution is small.

0 keV

769

M1

E1

137

2+

1+

8B

7Be+p

429

Check low-θ17 = low-Erel data points

Present analysis condition: sharp cutoff at d = 4 strips

7Be

p

d = 6 strips = 0.6 mm

w

•Simulation of low-θ17 response must be improved!•Low Erel cross sections will increase!

typical single-event hit pattern in SSD p-7Be opening angles θ17

E2 contribution found at MSU

B. Davids and S.Typel, PRC 68, 045802 (2003)

MSU:CD of 8B at 44, 81 A MeV

Inclusive 7Bemomentum spectrawith high resolutionat S800

1st order pert. theory(same as for GSI)44 A MeV: f=1.081 A MeV: f=0.6

dynamical theory

44 A MeV: f=1.681 A MeV: f=1.2

Asymmetries are interpreted as signs for E1-E2 interference!

but:

E2 scaling factor is energy-dependent!

Reaction Significance Laboratory

d(,)6Li big bang GSI

7Be(p,)8B pp chain RIKEN,GSI,MSU

8B(p,)9C hot pp-chain RIKEN*

11C(p,)12N hot pp chain GANIL,RIKEN

12C(p,)13N CNO RIKEN*

12N(p,)13O hot pp chain RIKEN*

13N(p,)14O hot CNO RIKEN,GANIL

14C(n,)15C r-process GSI

22Mg(p,)23Al rp-process RIKEN

26Si(p,)27P rp-process RIKEN

Coulomb-dissociation experiments of astrophysical interestRadiative-capture reactions studied by Coulomb

dissociation

*unpublished