1

Neutrino: a spy of the Neutrino: a spy of the innermost solar interiorinnermost solar interior

Nuclear reactions in the Sun Nuclear reactions in the Sun and solar neutrinosand solar neutrinos

2

The spy of nuclear reactions The spy of nuclear reactions in the Sunin the Sun

• The real proof of the occurrence of The real proof of the occurrence of nuclear processes is in the detection of nuclear processes is in the detection of reaction products (holds for Sun & reaction products (holds for Sun & Earth)Earth)

• For the Sun, only neutrinos can escape For the Sun, only neutrinos can escape freely from the production region.freely from the production region.

• By measuring solar neutrinos one can By measuring solar neutrinos one can learn about the deep solar interior (and learn about the deep solar interior (and about neutrinos…)about neutrinos…)

3

The luminosity constraintThe luminosity constraint• The The total neutrino fluxtotal neutrino flux is immediately derived is immediately derived

from the solar constant Kfrom the solar constant Koo::

• If one assumes that Sun is powered by If one assumes that Sun is powered by transforming H into He (transforming H into He (QQ=26,73MeV):=26,73MeV):

4p+2e4p+2e-- -> 4He + -> 4He + ?

• Then one has Then one has 22ee for each for each QQ of radiated of radiated energy, and the total neutrino produced energy, and the total neutrino produced flux is:flux is:

• = if if LL and and LL ee are conserved are conserved2e?

s/cm/104.62/Q

K 211oTOT

4

Towards neutrino energy Towards neutrino energy spectraspectra

• To determine To determine tottot we did not use we did not use

anything about nuclear reactions and anything about nuclear reactions and solar models.solar models.

• In order to determine the components In order to determine the components ((pppp, , Be Be BB…)one has to know the …)one has to know the

relative efficiencies of nuclear reactions relative efficiencies of nuclear reactions in the Sun (branches ppi/ppII/ppIII…)in the Sun (branches ppi/ppII/ppIII…)

5

The pp-chainThe pp-chain99,77%

p + p d+ e+ + e

0,23%p + e - + p d +

e

3He+3He+2p

3He+p+e+

+e

~210-5

%84,7%

13,8%

0,02%13,78%3He + 4He 7Be +

7Be + e- 7Li + e7Be + p 8B

+

d + p 3He +

7Li + p ->+

pp I pp I pp IIIpp III pp IIpp II hephep

8B 8Be*+ e+ +e

2

6

A group pictureA group picture

Neutrino Energy [Mev]

Neutr

ino fl

ux [

cm-2 s

-1 ]

7

Another group pictureAnother group picture

The production region of neutrinos

8

A 40 year long A 40 year long journeyjourney•In 1963 J Bahcall and R Davis, In 1963 J Bahcall and R Davis, based on ideas from Bruno based on ideas from Bruno Pontecorvo, started an exploration Pontecorvo, started an exploration of the Sun by means of solar of the Sun by means of solar neutrinos.neutrinos.

•Their trip had a long detour, Their trip had a long detour, generating the “solar neutrino generating the “solar neutrino puzzle”puzzle”

•All experiments, performed at All experiments, performed at Homestake, Kamioka, Gran Sasso Homestake, Kamioka, Gran Sasso and Baksan exploring different and Baksan exploring different portions of the solar spectrum, portions of the solar spectrum, presented a deficit of presented a deficit of ee..

•Were all experiments Were all experiments wrong?wrong?

•Was the SSM wrong?Was the SSM wrong?

•Was nuclear physics Was nuclear physics wrong?wrong?

•Or did something Or did something happen to neutrinos happen to neutrinos during their trip from during their trip from Sun to Earth? Sun to Earth?

9

Disappearance vs. AppearanceDisappearance vs. Appearance

??

10

SNO: the appearance SNO: the appearance experimentexperimentA 1000 tons heavy water detector sensitive to B-neutrinos by means of:

•CC: CC: ee+d -> p + p + e+d -> p + p + e

sensitive to e only, provides a good measurement of e spectrum with weak directionality

•NC: NC: xx+d -> p + n + +d -> p + n + xx

Equal cross section for allall flavors. It measures the total 8B flux from Sun.

•ES: ES: xx+e -> e + +e -> e + xx

Mainly sensitive to e, strong directionality.

The important point is that SNO can determine both: ((ee) and ) and ((ee + + + + ))

11

SNO resultsSNO results•The measured total B neutrino flux is in excellent agreement with the SSM prediction.

•Only 1/3 of the B-neutrinos survive as e

•2/3 of the produced transform into or

•SSM & N.P are SSM & N.P are rightright

•All experiments All experiments are rightare right

•Neutrinos are Neutrinos are wrongwrong

12

From Sun to Earth:From Sun to Earth:The KamLAND The KamLAND confirmationconfirmation

•anti-e from distant (100 km) nuclear reactors are detected in 1Kton liquid scintillator where:

Antie +p -> n + e+

n + p -> d +

•Obs./Expected= 54/ (86+-5.5)

-> Oscillation of reactor anti-Oscillation of reactor anti-ee

provenproven

- > - > SNO is confirmed with SNO is confirmed with man man made (anti)neutrinosmade (anti)neutrinos

13

The impact of SNO and KamLANDThe impact of SNO and KamLAND

Before Before SNOSNO

After After SNO-ISNO-I

After After KamLANDKamLAND

After After SNO-IISNO-II

14

BrunoBruno PontecorvoPontecorvo

•The Cl-Ar method•Neutrino sources (sun, reactors, accelerators)•Neutrino oscillations

Neutron Well LoggingNeutron Well Logging - A New A New Geological Method Based on Geological Method Based on Nuclear PhysicsNuclear Physics, Oil and Gas Journal, 1941, vol.40, p.32-33.1942.•An application of Rome celebrated study on slow neutrons, the neutron log is an instrument sensitive to water and hydrocarbons. •It contains a (MeV) neutron source and a (thermal) neutron detector. As hydrogen atoms are by far the most effective in the slowing down of neutrons, the distribution of the neutrons at the time of detection is primarily determined by the hydrogen concentration, i.e. water and hydrocarbons.

15

From neutrons to neutrinosFrom neutrons to neutrinos

• We have learnt a lot on neutrinos. Their survival/transmutation probabilities in matter are now understood.

• We have still a lot to learn for a precise description of the mass matrix (and other neutrino properties…)

• Now that we know the fate of neutrinos, we can learn Now that we know the fate of neutrinos, we can learn a lot a lot from from neutrinos.neutrinos.

16

What next?What next?

Neutrinos and SupernovaeNeutrino contribution to DMNeutrino contribution to DM

Neutrinos and the Earth Neutrinos and the Sun

17

The measured The measured boron fluxboron flux

• The total active (e + + boron flux is now a measured quantity. By combining all observational data one has:

= 5.5 (1 ± 7%) 106 cm-2s-1.

• The central value is in good agreement with the SSM calculation

• Note the presentpresent 1 error is // =7% =7%

• In the next few yearsnext few years one can expect to reach //3%3%

BP2000 FRANECC GARSOM

[106s-1cm-2]

5.05 5.20 5.30

18

s33 s34

s17se7 spp

Nuclear

The Boron Flux, Nuclear The Boron Flux, Nuclear Physics and AstrophysicsPhysics and Astrophysics

• depends on nuclear physics nuclear physics

and astrophysics inputs• Scaling laws have been found numerically* and are physically

understood

= (SSM) · ss3333

-0.43 -0.43 ss34 34 0.84 0.84 ss1717

1 1 sse7e7-1 -1 sspppp

-2.7-2.7

· comcom1.41.4 opa opa2.62.6 dif dif 0.340.34 lum lum7.27.2 • These give flux variation with respect to the SSM calculation

when the input X is changed by x = X/X(SSM) .• Can learn astrophysics if nuclear physics is known well

enough.

astro

*Scaling laws derived from FRANEC models including diffusion. Coefficients closer to those of Bahcall are obtained if diffusion is neglected.

19

Uncertainties budgetUncertainties budget• Nuclear physics uncertainties,

particularly on S34 , dominate over the present observational accuracy / =7%.

• The foreseeable accuracy / =3% could illuminate about solar physics if a significant improvement on S34 is obtained.

• For fully exploiting the physics potential of a measurement with 3% accuracy one has to determine S17 and S34 at the level of 3% or better.

Source X/X (1 /(1

S33 0.06* 0.03

S34 0.09 0.08

S17** 0.05 ? ** 0.05

Se7 0.02 0.02

Spp 0.02 0.05

Com 0.06 0.08

Opa 0.02 0.05

Dif 0.10 0.03

Lum 0.004 0.03

*LUNA gift

** See later

20

ProgressProgress on Son S1717S17(0)

[eV b]

Ref.

Adel.-Review. 19-2+4 RMP 70,1265 (1998)

Nacre-Review 21 ± 2 NP 656A, 3 (1999)

Hammache et al 18.8 ± 1.7 PRL 86, 3985 (2001)

Strieder et al 18.4 ± 1.6 NPA 696, 219 (2001)

Hass et al 20.3 ± 1.2 PLB 462, 237 (1999).

Junghans et al. 22.1 ± 0.6 PRL 88, 041101 (2002)+ nucl exp 0308003

Baby et al. 21.2 ± 0.7 PRL. 90,022501 (2003)

Results of direct capture expts**.

•JNB and myself have long been using a conservative uncertainty, however recently high accuracy determinations of S17 have appeared.•Average from low-energy (<425KeV) data of 5 recent determinations yields:

SS1717(0)= 21.4 (0)= 21.4 ±± 0.5 with 0.5 with dof=1.2dof=1.2•A theoretical error of ±A theoretical error of ± 0.5 0.5 has to be added.has to be added.•However all other expts. give somehow smaller S17 than Junghans et al.

**See also Gialanella et al EPJ A7, 303 (2001)

•Note that indirect methods also give somehow smaller values

•In conclusion, it looks that a In conclusion, it looks that a 5% accuracy has been 5% accuracy has been reached.reached.

21

Remark on SRemark on S1717 and S and S3434

• For a long time S17 was the main uncertainty.

• If SS1717(0)= 20.5 (0)= 20.5 ±± 1 eVb 1 eVb a 5% accuracy has been reached.

• The 9% error of S34 is the main source of uncertainty for extracting physics from Boron flux.

• LUNA measurement of S34 will be extremely important.

Source S/S (1 /

S33 0.06* 0.03

S34 0.09 0.08

S17**S17** 0.050.05 0.050.05

Se7 0.02 0.02

Spp 0.02 0.05

Com 0.06 0.08

Opa 0.02 0.05

Dif 0.10*** 0.03

Lum 0.004 0.03

22

Sensitivity to the central temperatureSensitivity to the central temperature

• Boron neutrinos are mainly determined by the central temperature, almost in the way we vary it.

• (The same holds for pp and Be neutrinos)

Bahcall and Ulmer. ‘96

i/

iSS

M

BB

BeBe

pppp

T/TSSM

Castellani et al. ‘97

23

The central solar temperature

• The various inputs to can be grouped according to their effect on the solar temperature.

• All nuclear inputs (but S11) only determine branches ppI/ppII/ppIII without changing solar structure.

• The effect of the others can (largely) be reabsorbed into a variation of the “central” solar temperature:

• = (SSM) [T /T(SSM) ]2020.. .. SS3333

-0.43 -0.43 ss34340.84 0.84 ss17 17

sse7e7-1-1

SourcedlnT/dlnS

dlnB/dlnS

S33 0 -0.43

S34 0 0.84

S17 0 1

Se7 0 -1

Spp -0.14 -2.7 1919

Com +0.08 +1.4 1717

Opa +0.14 2.6 1919

Dif +0.016 0.34 2121

Lum 0.34 7.2 2121

•Boron neutrinos are excellent solar thermometers due to their high ((20)20) power dependence.

24

Present and future for measuring T with Present and future for measuring T with B-neutrinosB-neutrinos

• At present, // =7% =7% and SSnucnuc/ S/ Snucnuc== 10% (cons.) translate into

T/T= 0.6 %T/T= 0.6 %

the main error being due to S17 and S34.

• If nuclear physics were perfect (SSnucnuc/S/Snuc nuc =0=0) already now we could have:

T/T= 0.3 %T/T= 0.3 %

• When // =3% =3% one can hope to reach (for Snuc/Snuc =0) :

T/T= 0.15 %

25

The central solar The central solar temperature and temperature and helioseismologyhelioseismology

• For the innermost part, neutrinos are now (T/T = 0.6%) almost as accurate as helioseismology • They can become more accurate than helioseismology in the future.

• Helioseismology determines sound speed.

•The accuracy on its square is u/u 0.15% inside the sun.

• Accuracy of the helioseismic method degrades to 1% near the centre.

• Boron neutrinos provide a complementary information, as they measure T.

u/u1 3

present

T/Tfuture

26

The Sun as a laboratory The Sun as a laboratory for astrophysics and for astrophysics and fundamental physicsfundamental physics

• A measurement of the solar temperature near the center with 0.15% accuracy can be relevant for many purposes– It provides a new challenge to SSM calculations– It allows a determination of the metal content in the solar

interior, which has important consequences on the history of the solar system (and on exo-solar systems)

• One can find constraints (surprises, or discoveries) on:– Axion emission from the Sun– The physics of extra dimensions

(through Kaluza-Klein axion emission)– Dark matter

(if trapped in the Sun it could change the solar temperature very near the center)

– …

BP-2000 FRANEC GAR-SOM

T6 15.696 15.69 15.7

27

CNO neutrinos, LUNA CNO neutrinos, LUNA and the solar interiorand the solar interior

•The principal error source is SThe principal error source is S1,141,14. The new measurement . The new measurement by LUNA is obviously welcome.by LUNA is obviously welcome.•A measurement of the CNO neutrino fluxes would provide a stringent test of the theory of stellar evolution and unique information about the solar interior.

SourceX/X

(1)/ O/O

S33 0.06 0.001 0.0008

S34 0.09 0.004 0.003

S17 0.05 0 0

Se7 0.02 0 0

Spp 0.02 0.05 0.06

S1,14 +0.11

-0.46

+0.09

-0.38

+0.11

-0.46

Com 0.06 0.12 0.13

Opa 0.02 0.04 0.04

Dif 0.10 0.03 0.03

Lum 0.004 0.02 0.03

•Solar model predictions for CNO Solar model predictions for CNO neutrino fluxes are not precise neutrino fluxes are not precise because the CNO fusion because the CNO fusion reactions are not as well studied reactions are not as well studied as the pp reactions.as the pp reactions.•Also, the Coulomb barrier is Also, the Coulomb barrier is higher for the CNO reactions, higher for the CNO reactions, implying a greater sensitivity to implying a greater sensitivity to details of the solar model.details of the solar model.

28

Solar neutrino experiments and CNO Solar neutrino experiments and CNO cyclecycle

• Solar neutrino experiments set an upper limit (3) of 7.8% to the fraction of energy that the Sun produces via the CNO fusion cycle.

• An order of magnitude improvement upon the previous limit.

• New experiments are required to detect CNO neutrinos and to proof that some 1% of the solar luminosity is generated by the CNO cycle.

Bahcall, Garcia & Pena-Garay Astro-ph 0212331

29

Is the Sun fully powered by Is the Sun fully powered by nuclear reactions?nuclear reactions?

• Are there additional energy sources beyond 4H->He?:• Are there additional energy losses, beyond photons Are there additional energy losses, beyond photons

and neutrinos?and neutrinos?• One can determine the “nuclear luminosity” from One can determine the “nuclear luminosity” from

measured neutrino fluxes , Kmeasured neutrino fluxes , Knucnuc = = tottot Q/2 , and Q/2 , and compare with the observed luminosity K:compare with the observed luminosity K:

KKnucnuc/K= 1.4 (1 +- 25%) (1/K= 1.4 (1 +- 25%) (1))• This means that, within 25%, the Sun is actually This means that, within 25%, the Sun is actually

powered by 4H->He fusion…powered by 4H->He fusion…

30

SummarySummary

• Solar neutrinos are becoming an important tool for studying the solar interior and fundamental physics.

• Better determinations of S34 and S1,14 are needed for fully exploiting the physics potential of solar neutrinos.

• All this brings towards answering fundamental questions:

• Is the Sun fully powered by nuclear reactions?Is the Sun fully powered by nuclear reactions?• Is the Sun emitting something else, beyond Is the Sun emitting something else, beyond

photons and neutrinos?photons and neutrinos?