Carla Maria Cattadori INFN Milano and Milano Bicocca Physics Department

Results from Solar Neutrino Radiochemical Experiments

(with main emphasis on Gallium)

Neutrino 2004, Paris 13-18 June 2004

Carla Maria Cattadori INFN Milano and Milano Bicocca Physics Department

Carla Maria Cattadori 2Neutrino 2004, Paris 13-18 June

Results from Solar Neutrino Radiochemical Experiments

Generalities about solar neutrinos and radiochemical experimentsResults of Chlorine, SAGE, GALLEX/GNOImpact on

Neutrino PhysicsAstrophysics“Technological” results

Are precision measurements possible,with radiochemical experiments ?Conclusions


Generalities on radiochemical experiments

Radiochemical experiments provided at the end of the ´60 the first indication of solar neutrino flux anomaly at Earth. (22 years after the Pontecorvo idea to exploit the reaction e(N,N´)e-) to detect neutrinos.)

Since then, they have continuously performed measurements of solar neutrino capture rate at Earth that, until year 2000 (before SNO), were of invaluable importance both to determine (m2,sin22) and for solar astrophysics.

Nowadays, in the SNO + KamLAND era, their role is changed; having almost no weight in the neutrino oscillation parameters determination (3 values over 44 SK+ 34 SNO + 13 KL +3 Rchem= 94) they are still the only experiments that have detected sub-MeV (7Be, pp) e

Sun. Therefore they are the experimental verification at low energy of

solar models neutrino oscillation mechanism

Sune

R



Nowadays, in the neutrino community, radiochemical experiment are considered like turtles (“protected” ancient animals):

• they are slow, low statistic experiment

• they are sensitive only to e

• they measure only one quantity (the integral solar neutrino interaction rate).

• they do not measure spectrum or incoming direction of solar neutrinos.

It is common opinion that having reached a statistical accuracy almost equal to the systematic accuracy they have almost accomplished their role.



• CC experiments sensitive only to e. Proposed by Pontecorvo in 1946.

N' (unstable) is then separated from the target with physical-chemical techniques and then quantitatively measured

observing its decay back in N.

as

1 Solar Neutrino Unit [SNU] = 1 interaction/sec each 1036 target atoms.

Ntarget = 1029-1030 nuclei, namely O(10-100) tons of target to have O(1) interaction/day

eNNe

-1210i

2-46i ][ 106 ~ ; 10 ~ s cmcm

)()(

)(i)( target dEPdE

EdENRRatenInteractio ee

ii


The interactionThe interaction

Signal Composition:(BP04+N14 SSM+ osc) Signal Composition:(BP04+N14 SSM+ osc)

pep+hep 0.15 SNU ( 4.6%)7Be 0.65 SNU (20.0%)8B 2.30 SNU (71.0%)CNO 0.13 SNU ( 4.0%)Tot 3.23 SNU ± 0.68 1

pep+hep 0.15 SNU ( 4.6%)7Be 0.65 SNU (20.0%)8B 2.30 SNU (71.0%)CNO 0.13 SNU ( 4.0%)Tot 3.23 SNU ± 0.68 1

Expected Signal (BP04 + N14)Expected Signal (BP04 + N14)

8.2 SNU +1.8–1.8 1 8.2 SNU +1.8–1.8 1

37Cl(e,e)37Ar (Ethr = 813 keV) Kshell EC = 50.5 d

37Cl + 2.82 keV (Auger e-, X)

37Cl(e,e)37Ar (Ethr = 813 keV) Kshell EC = 50.5 d

37Cl + 2.82 keV (Auger e-, X)

The Pioneer: Chlorine Experiment


The Chlorine experimentName

Location

e interaction reaction

Target comp. and mass

Exp. Time [d]

[d]

Data taking

Lab overburden

Chlorine

(Homestake Mine);South Dakota USA

e(37Cl,37Ar)e- C2Cl4

615 tons

Liquid

60-120 50.5 1964- 19944200 mwe

Name

LocationData used

for R determinat

ion

N runs

Average

efficiency

Hot chem check

Source calib

Chlorine(Homestake Mine);South Dakota USA

1970-1994

108 <>extr = 95 %

<>synth = (95.8 ± 0.7) %

<>count = 42 %

36Cl No


Results of Chlorine experiment

1. First measurement of solar neutrino interaction rate

2. Raised the problem of missing neutrinos

3. Opened a field of research that is not yet closed. Davis awarded in 2002, with the Nobel prize together with Koshiba and R. Giacconi

“for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos"

R = 2.56 R = 2.56 ± ± 0.16 0.16 ±± 0.16 SNU 0.16 SNU = 2.56 = 2.56 ± 0.23± 0.23

Constancy of the solar neutrino flux (over 23 years): no correlation has been found between R Sun and the solar cycle (many speculation on this item in the ‘90)


Gallium experiments

SAGE - The Russian-American Gallium Experiment


Collaboration e interaction reaction


Exp. Time [d]

Data taking

Lab overburden

GALLEX/

GNO

LNGS Italy

D (MPIK,TUM),

I (INFN),

F (CEA), USA (BNL), Israel

e(71Ga,71Ge)e- GaCl3• HCl in H2O

103 t (30 t Ga)

21-28

28

1991-2003

3500 mwe

0.6 [h m2]-1

SAGE

Baksan

Kabardino Balkaria

RU (INR, RAS)

USA (LNL,BNL)e(71Ga,71Ge)e- Metallic Ga

50 tons

28 1990-ongoing

4800 mwe

0.1 [h m2]-1


The interaction(proposed by Kuzmin in 1966)

The interaction(proposed by Kuzmin in 1966)

71Ga(e,e)71Ge (Ethr = 233 keV)K,L shell EC = 16.5 d

71Ga + 10 keV, 1 keV (Auger e-, X)

71Ga(e,e)71Ge (Ethr = 233 keV)K,L shell EC = 16.5 d

71Ga + 10 keV, 1 keV (Auger e-, X)

Signal Composition:(BP04 +N14 SSM+ osc) Signal Composition:(BP04 +N14 SSM+ osc)

pp + pep 41.7 SNU ( 62 %)7Be 19.0 SNU (28 %)CNO 2.6 SNU ( 3.9 %)8B 4.1 SNU ( 6.1 %)Tot 67.4 SNU +2.6

–2.3 1

No osc 127 SNU +12 –10

pp + pep 41.7 SNU ( 62 %)7Be 19.0 SNU (28 %)CNO 2.6 SNU ( 3.9 %)8B 4.1 SNU ( 6.1 %)Tot 67.4 SNU +2.6

–2.3 1

No osc 127 SNU +12 –10

Expected Signal (SSM + osc)Expected Signal (SSM + osc)

0.6 int. per day in GNO (1 in SAGE), but due to decay during exposure + ineff., 4.7 71Ge decay

detected per extraction (28 days exposure).

0.6 int. per day in GNO (1 in SAGE), but due to decay during exposure + ineff., 4.7 71Ge decay

detected per extraction (28 days exposure).

Gallium ExperimentsGALLIUM ExperimentsGALLIUM Experiments


Gallium ExperimentsGallium Experiments

Data taking

N runs

Average

Efficieny

Tank to counter

Hot chem check

Source calib

Rex

[SNU]

GALLEXGALLEX/GNO/GNOLNGS Italy

1991-2003

stopped

123 97 % 71As Yes

twice51Cr

source

69.3 ± 4.1 ± 3.6

5.9% 5.2%

69.3 69.3 ± ± 5.55.5

SAGESAGEBaksan

Kabardino Balkaria

1990-ongoing

121 90 % No Yes51Cr37Ar

66.9 ± 3.9 ± 3.6

5.8% 5.2%

66.9 66.9 +5.3+5.3 –5.0–5.0

New !!New !!

68.1 68.1 ± 3.75 ± 3.75 (5.5%)(5.5%)New combined valueNew combined value


SAGESAGE January 1990 – December2003

14 years – 121 runs

66.9 66.9 +5.3+5.3-5.0-5.0 SNU SNUSee poster session !

51Cr source experiments


GALLEXGALLEX65 Solar runs = 1594 d23 Blank runs

GNOGNO 58 Solar runs = 1713 d12 Blank runs

62.9 62.9 ++5.55.5 –5.3–5.3 ± 2.5 SNU ± 2.5 SNU

See poster sessio

n !

77.5 77.5 ± 6.2 ± 4.5 SNU± 6.2 ± 4.5 SNU

51Cr source, 71As experiments


Balance of the signal in L/K region

L K L+K

GALLEX 74.4 ± 10 79.5 ± 8.2 77.5 ± 6.2

GNO 68.2 +8.9 –8. 5 59.5 +6.9 –6.6 62.9 +5.5 –5.3

GALLEX/GNO

70.9 ± 6.6 67.8 ± 5.3 69.3 ± 4.1

SAGE 64.0 +5.9-5.7 69.1 +5.3

-5.1 66.9 +3.9-3.8

within 1, events are equally distributed between L and K window, as expected from counting efficiencies


Event energy distribution

Important! No other peaks appear in the spectrum

Event time distribution.

Analysis: M.L. analysis.

Null hypothesys: 1 decaying isotope + flat backgrd (independent /each run)

fit = 16.6 ± 2.1 days

76Ge = 16.5 days

The signal is validated for both SAGE and GALLEX/GNO by

1 keV

10 keV


GALLEX/GNO seasonal variation analysis

peri

helio

n

ap

helio

n

Flat: 2= 2.7 (5 d.o.f.), C.L.: 75%

Elliptical: 2= 3.0 (5 d.o.f.) C.L.: 70%

bi-monthly binning of the whole data set


GALLEX +GNO Seasonal variations

GALLEX +GNO Seasonal variations

Winter-Summer (statistical error only):

GNO only (58 SRs):

Winter (32 SR): 58.7+7.1-6.8 SNU

Summer (26 SR): 69.0+8.8-8.3 SNU

W-S: -10 ± 11 SNU (expected from 1/d2: +2.5)GNO + Gallex (123 SRs):

Winter (66 SR): 66.5+5.6-5.4 SNU

Summer (57 SR): 74.1+6.4-6.2 SNU

W-S: -7.6 ± 9 SNU (expected from 1/d2: +2.5)

Included in the analysis

by Fogli and Lisi

No excess in W-S, as expected for LMA !!No excess in W-S, as expected for LMA !!


SAGE survey of time modulations

No evidence of time modulation binning the all data set monthly, bimonthly, yearly.


Search for time modulations in GALLEX/GNO data

Lomb–Scargle analysis is a Fourier analysis for data not equally spaced in time.

Claim from Sturrock and Caldwell of a significant peak in the periodogram plot of GALLEX data (and also SK)

(1 / years)

Random gaussian fluctuations

astro-ph/0103154 and subsequent

We have repeated the analysis, found the same periodogram, but we don’t agree on the significance of the signal at 13.5 y-1


Lomb-Scargle analysisL.-S. time series analysis of 58 simulated GNO-like runs

40 SNU error on single sun

pow

er

0.1% CL

pow

er

frequency (y-

1)

frequency (y-

1)

25 SNU error on

single sun

0.1% CL


Time modulation exclusion plot from GALLEX/GNO data

Rule out modulations Rule out modulations with frequency < 12 ywith frequency < 12 y-1-1 and amplitude > 40% of and amplitude > 40% of signalsignal

1 = 69.3 SNU


GALLEX GNO

The capture rate published by both experiments has monotonically decreased in the last 5-6 years


GNO

= 63 = 43

= 89 = 55

= 73 = 52

GALLEXGALLEX+GNO

SAGE


combining SAGE and GALLEX/GNO period Jan 1990 – December 2003

68.1 ± 3.75 (5.5%)

SAGEPeriod Jan `90 Oct `99 Jan `90 Dec `03

N runs 70 51 121

R 75.4 +7.0 –6.8 +3.5 –3.0 * < 60 ?? 66.9 +3.9 –3.8 +3.6 –3.2

GALLEX/GNO

Period May `91 – Jan `97 Apr `98 – Mar `03 May `91 – Mar `03

N runs 65 58 123

R 77.5 ± 6.2 +4.3 –4.7 62.9 ± 5.4 ± 2.5 * 69.3 ± 4.1 ± 3.6

* this value is before the efficiencies re-evaluation

* reduction of systematic obtained in GNO has not been propagated back to GALLEX


…. all this means that

•it has been of crucial importance to proceed with the data taking so long.

• RGa published by both experiments, has monotonically decreased in

the last 6-7 years. The statistical significance of this decreasing in each experiment is low, but the joint probability…..

• given the relevance that Gallium capture rate has and will have once the 7Be flux will be available from Borexino or Kamland, it is important that both collaborations investigate once more if necessary to select “golden data set”, (difficult and dangerous action!!) then perform a joint analysis to provide their joint best evaluation of Ron Gallim (debate in the collaborations about this item)


Determination of Gallium-e capture cross section

Ga-e capture cross sections are needed to compute fluxes from rate

At low energy ( < 410 keV, namely for pp s) only g.s.-g.s.transitions are present;for this transition cross sections are evaluated from 71Ge E.C.

good accuracy ( 2.3% at 1)

At the 7Be energies, the first two excited state (at 175 and 500 keV) must be considered; BGT estimated from (p,n) reactions;

estimated accuracy –3% +5%

Direct measurement desirable


Experimental situationTwo GALLEX and one SAGE calibrations,

with strong 51Cr sources

RRmeasmeas = 0.9= 0.93 3 ±± 0.070.07 R Rtheotheo

Improvements are well possible irradiating with a 2MCi source f.i. 20 tons of metallic gallium

Final accuracy 5% or better = theoretical accuracy to addrees the question:

corrections to

g.s.-e.s. only

or to g.s.-g.s. also?

GALLEX sources: 1.71 MCi 1.87 MCi

SAGE source 0.52 MCi


SAGE 37Ar source: see details in SAGE poster

Ca40(n,alfa)Ar37

0

50

100

150

200

250

1.E-02 1.E-01 1.E+00 1.E+01 Energy, ?eV

Cross s

ecti

on

,?b

0.000

0.005

0.010

0.015

0.020

0.025

Barnes75 Knellwolf66Guoyou93 Zhang2000Qaim79 Bormann79

Bartle77 Bartle81JENDL-3.2 ENDF/B-6FOND-2.3 ADL-3FLUX

330 Kg of Ca2O3

SAGE is at the moment irradiating 13.2 tons of its metallic Gallium with a 37Ar source 614 kCi strenght:

E (37Ar) > E (51Cr) improved sensitivity for second 71Ge e.s.


Gas processing efficiencies evaluation

Data from neutrino source experiments can be used to infer on the cross section only once the extraction + gas processing

efficiencies are exactly determined, and “hot chemistry” effect are excluded.

This has been done by the GALLEX collaboration, spiking the target with O(10000) atoms of 37As, that beta decay to 76Ge,

kinematically mimicking the interaction.The processing efficiency has been found to be correctly

extimated (from the methods routinely adopted at each run) =100% with 1% error.


Impact of Gallium experimental results on neutrino oscillation parameters determination.

Almost irrelevant with the actual experimental accuracy in the actual experimental scenario


Allowed (m2,tan2) regions from Radiochemical experiments

-4

1010-4 10-3 10-2 10-1 11010-4 10-3 10-2 10-1 1

Ga experiments are more sensitive to tan212 than to m2


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

00

Theta=35

°

Theta=30

°

Theta=32

.5°

Theta=28

.5°

Theta=37

.5°

0.954

0.970

0.983

1.000

1.016

p

p

Comments: No sensitivity within the presently allowed oscillation parameter region

Oscillation parameters vs (Ga rate + SSM)


Impact of Gallium Results on Astrophysics


Solar Models R previsions for Radiochemical experiments

Flux

(cm-2s-1)

BP00 BP04 BP04 +

N14

BP04+

+ N14

Pee

m2 = 7.1x10-5 eV2

12 = 32.5

pp (109) 59.5 (± 1%) 5.94 (± 1%) 59.8 60.3 0.578 (vac)

pep (108) 1.40 (± 2%) 1.40 (± 2%) 1.42 1.44 0.531(vac)

hep (103) 9.24 7.88 (± 16%) 7.93 8.09 ~ 0.3 matter7Be (109) 4.77 (± 10%) 4.86 (± 12%) 4.86 4.65 0.557 vac8B (106) 5.05 +20%

-16% 5.79 (± 23%) 5.77 5.24 0.324 matter

13N (108) 5.48 +21%-17% 5.71 2.30 0.557 vac

15O (108) 4.80 +25%-19% 5.03 1.79 0.541 vac

17F (106) 5.63 +25%-25% 5.91 3.93

37%35% 3.23

%43%3954.2

%44%4485.5

from LUNA experiment on 14N(p,)15ONew S0(14N+p) = 1.77 keV ± 0.2

increased accuracy in 7Be(p,)8B measurement Columns 2,3,4 from BP04


…… to summarize

BP00 with Z/Xold= 0.0229

BP04 = BP00 + New data on EOS, Nucl Phys.(Cross sections)

N14 = BP04 + S0(14N+p) = 1.77 keV ± 0.2

BP04+ = BP04 + Z/Xnew=0.0176

to be compared with

RRCZ 715.0

RRCZ 725.0

001.0713.0 measR


Solar Models R previsions for Radiochemical experimentsExperimental

m2,

tan212

from experiments

BP00 BP04 BP04

+ N14

BP04+ + N14

SNO/

SK

5.21 ± 0.27(cm-2s-1)

7.1, 0.45 †

7.3, 0.42 *

1.00 +6% -6%

1.01 +6% -6%

no osc 5.05 +20%

-16%

5.79 (± 23%) 5.77 5.24

Cl

2.56 ± 0.23

[SNU]

7.1, 0.45 †

7.3, 0.42 *

3.06 ± 0.04

2.79 ± 0.18 3.35 (± 21%) 3.23 2.95

no osc 7.6 +1.3

–1.1

8.5 +1.8 –1.8 8.2 7.7

Ga

68.1 ± 3.75

[SNU]

7.1, 0.45 †

7.3, 0.42 *

69.4 ± 2.6

65.8 ± 4.5 67.7 ± 5.5 69.3 ± 5.3 67.7 ± 5.3

no osc 128 +9 -7

131 +12 –10 127 +12

–10 127 +12

–10

† (best fit point all solar + KamLAND data. 8B flux free, other fluxes from BP00)* (best fit point all solar + KamLAND data; all fluxes free + lum. constr.)


Comparison of solar model predictions with experimental results

• Neutrinos prefer a Sun having “low metallicity” solar interior, as the recent photospheric measurements indicate

• when this data are included in the SSM tension with helioseismology as the depth of the convective zone goes to 0.726 Rsun (instead of 0.713 as measured i.e. 18% discrepancy).


LCNO estimate from Gallium experimental results imposing the luminosity constraint

neutrinoemittedperphotonsinMeVi

12111053.8 sMeVcmLi

iiSun

)()(

)(itarget dEPdE

EdENR ee

ii

and knowing from experiments RGa which is given by the sum of all the neutrino components, weighted by the cross section and Pee

Assumption: nuclear fusion reactions are the only source of energy in the Sun


Parameter Parameter

Uncertainty

Rga

Uncertainty

(SNU)

Theta +/- 2.5° SNO+kam+SK

2.9

7Be 10% SSM 1.9

Cross section GS -GS 2.3% 1.5

Cross section GS –ES(1,2) 50% 0.7

Cross section GS-ES>2 35% 1.5

8B 9 % SNO 0.4

pep 1.5 % SSM 0.1

4.24.2

GalliumUncertainties for evaluation of pp and CNO flux


…..it is possible to estimate at the same time pp and CNO once

we know the 8B, 7Be, pep fluxes

iii

NNOO

Sun

CNO

L

L

• 8B take from experiments

• 7Be take from SSM

• pep strictly related to pp


Important! Here the solar model N14 (Bahcall nomenclature) is used as reference, i.e. the unity on the Y axis take already into account the reduced flux due to new S0(14N) measurement

3

2 1

best fit

3 limit

luminosity constraint


)%6.06.1(04

BPSun

CNO

L

L

0414

3.22.1 6.02.1

BPSun

CNO

NSun

CNO

fitbest

Sun

CNO

L

L

L

L

L

L

GG

)3(%7

GGSun

CNO

L

L

0414

???? 5.00.1

BPSun

CNO

NSun

CNO

fitbest

Sun

CNO

L

L

L

L

L

L

GGSAGE

)3(%65

GGSAGESun

CNO

L

L


Finally with the listed assumptions and from the capture rate measured in Gallium experiments it is

possible to determine

RRGaGa pppp

[[101099 cm cm-2-2 s s-1 -1 ]]pp pp //

pp pp (BP04+N14)(BP04+N14)

69.3 69.3 OldOld 59.9 59.9 (1(1± ± 0.02 0.02 ± 0.01± 0.01theotheo)) 1.00(2)1.00(2)

68.1 68.1 NewNew 58.8 58.8 (1(1± ± 0.02)0.02) 0.98(4)0.98(4)

Fantastic agreement !!


(8B)meas = (0.89 ± 0.04ex ± 0.23theo) (8B) BP04 + N14

(7Be)meas = (0.91+0.24-0.62 ex ± 0.11theo) (7Be) BP04+N14

…. for 8B and 7Be

from BP04


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

04

0.954

0.970

0.983

1.000

1.016

Fp

p

GALLEX/GNO - all uncertainties

R = 69.3 +- 5.5 SNU

Comments: perfect agreement of Ga rate with SSM + oscillation scenario (pp) probed at 2% level (1 sigma)

(CNO) < 3.5 SSM (2 sigma)But to be totally model independent we need a measurement of (Be) at 10%

Measured

SS

M p

redi

ctio

nE

xper

imen

tal c

onst

rain

t

SSM

pre

dict

ion

Exp

erim

enta

l con

stra

int


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

00

0.954

0.970

0.983

1.000

1.016

Fp

p

GNO- all uncertainties

R = 62.9 +- 6.0 SNU

Comments: GNO is compatible with SSM + oscillation scenario at the level of 1 low values of the CNO flux are favored

GNO is at border GNO is at border of physical regionof physical region

Measured


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

00

0.954

0.970

0.983

1.000

1.016

Fp

p

GALLEX- all uncertainties

R = 77.5 +- 7.7 SNU

Comments: GALLEX is compatible with SSM + oscillation scenario within 2 The effect of GNO is important in the probe of the solar luminosity

Measured


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

00Gallium- 5% error

0.954

0.970

0.983

1.000

1.016

Fp

p B

P00

R = 70.0 +- 3.5 SNU


Are precision measurements possible with Gallium radiochemical experiments?


0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Gallium Rate (SNU)

FC

NO

N14

/BP

00Gallium- 3% error

0.954

0.970

0.983

1.000

1.016

Fp

p

Delta theta 1.5° - cross section measured at 1%Comments: Errors at the level of SSM uncertainties in pp flux


3 years of running; 4 weeks runs; 60% efficency; 70 SNU signal

Systematic error: 2.5 SNU ( GNO); not large improvements possible

30 tons30 tons 80 tons80 tons 160 tons160 tons

(GNO) (available gallium)

Det.evt.s 195 519 1040

Total accuracy 7 SNU7 SNU 4 SNU4 SNU 3 SNU3 SNU

Achievable accuracies


Technological results

•Few atoms chemistry

•Low level counting techniques

•Intense neutrino sources production (intensity calibration, know-how to produce and manipulate safely etc..)

•Radiochemistry techniques

•Radon counting and quantitative determination at level of few atoms.

•Ultra-low activity miniaturized proportional counters


Conclusions

• Radiochemical experiments have provided along the last 40 years measurements of solar e interaction rate on 37Cl and on 71Ga

• they confirm at sub-Mev energies the neutrino oscillation scenario and the standard solar model

•The update value for the neutrino capture rate on Gallium is

68.1 68.1 ± 3.7 ± 3.7 from 244 GALLEX+GNO+SAGE runsfrom 244 GALLEX+GNO+SAGE runs

• Gallium experiments have demonstrated to be reliable and have been calibrated with high intensity neutrino sources.Chlorine and GALLEX experiments has experimentally excluded hot chenistry effects

• No time modulations (seasonal, monthly, bimonthly, yearly) have been found with the actual accuracy we can state that the neutrino flux is constant


Taking (8B)meas = (0.89 ± 0.04ex ± 0.23theo) (8B) BP04 + N14

(7Be)meas = (0.91+0.24-0.62 ex ± 0.11theo) (7Be) BP04+N14

RRGaGa pppp

[10[1099 cm cm-2-2 s s-1 -1 ]]pp pp //

pp pp (BP04+N14)(BP04+N14)

69.3 69.3 OldOld 59.9 59.9 (1± 0.02 (1± 0.02 ± 0.01± 0.01theotheo)) 1.00(2)1.00(2)

68.1 68.1 NewNew 58.8 (1± 0.02)58.8 (1± 0.02) 0.98(4)0.98(4)

0414

3.22.1 )5.0(6.0)0.1(2.1

)( BPSun

CNO

NSun

CNO

fitbest

Sun

CNO

L

L

L

L

L

L

SGG

)3(%)6%5(%7)(

SGGSun

CNO

L

L


Extra slides


Radiochemical experimental techniqueRadiochemical experimental technique

t0

In synthesis lab

Add carrier1mg 72,74,76 Ge in GALLEX250mg 72,74,76 Ge in SAGE0.1 cc STP 36,38Ar in Chlorine exp.

ExtractionGa: GeCl4 with N2 Cl: Ar with Hestream

Wait Exposure time

Gallium (GeH4 + Xe), Chlorine (Ar + CH4)in counter V =1cc

1. Exposure

Counter in shielding

6 months for 76Ge12 months for 37Ar

Stop countingRemove counter

2. Extracted gas in counter

3.





Learning phase of these experiments is very long !


GALLEX – GNO

Test hypothesis of time constancy of signal:

1. Test of Likelihood Ratio C.L. 5.6 %

. 2 flat fit = 13.6 (6 d.o.f.) C.L. 3.4%


ImprovementsImprovements

Item Gallex GNO

Target size 0.8% 0.8%

Chemical yield 2.0% 2.0%

Counting efficiency

(active vol determination)

4.0% 2.2%

Pulse shape cuts 2.0% 1.3%*

Event sel. (others) 0.3% 0.6%

Side reactions 1.2 SNU 1.2 SNU

Rn-cut inefficiency 1.2 SNU 0.5 SNU68Ge contamination +1.8 SNU

-2.6 SNU -

* Neural network analysis

Many improvements resulting in a reduction of a factor of 2 in the systematic error


RGa = pp pp Ppp + CNO CNO PCNO + 8 8 P8 + 7 7 P7 + pep pep Ppep

RGa = 69.3 ± 5.5 SNU

P

(SNO+SK+KAM)

P

(SNU)

pp 59.8 BP04+N14 1.310 11.7 0.578 40.4

7Be 4.86 BP04+N14 1.260 71.7 0.557 19.4

N 0.323 BP04+N14 0.346 60.2 0.557 1.1

O 0.254 BP04+N14 2.157 115 0.541 1.5

8B 0.00521 SNO 0.663 24500 0.324 4.1

pep 0.142 BP04+N14 1.192 15.7 0.531 1.2

TOT 67.7

N = 1.14 O

Composition of the Gallium signal

LSun = pp pp + CNO CNO + 8 8 + 7 7 + pep pep


Solar Models previsions for R (int.rate) in Radiochemical Experiments

RRCZ 715.0

new meas.from LUNA exp. of

S0(14N+p) =

1.77 keV ± 0.2

14N(p,)15O

(Z/X) old

=0.0229


Solar Models R previsions for Radiochemical experiments



e interaction reaction


Exp. Time [d]

[d]

Data taking

Lab overburden

Chlorine

(Homestake Mine);South Dakota USA

e(37Cl,37Ar)e- C2Cl4

600 tons

Liquid

60-120 50.5 1964- 19934400 mwe

GALLEX/

GNO

LNGS Italy

e(71Ga,71Ge)e- GaCl3• HCl in H2O

100 t (30 t Ga)

21-28

28

16 1991-2003

2700 mwe

SAGE

Baksan

Kabardino Balkaria

e(71Ga,71Ge)e- Metallic Ga

55-49 tons

28 16 1990-ongoing

4800 mwe



Data used for R

determination

N runs

Average

efficiency

Hot chem check

Source calib

Rex

[SNU]

Chlorine(Homestake Mine);South Dakota USA

1970-1993

106 0.958

±

0.007

36Cl No 2.55 ± 0.17 ± 0.18

6.6% 7%

2.6 ± 0.3

GALLEX/GNOLNGS Italy

1991-2003

124 ?? 37As Yes

twice51Cr

source

69.3 ± 4.1 ± 3.6

5.9% 5%

SAGEBaksan

Kabardino Balkaria

1990-ongoing

104 ?? No Yes51Cr37Ar

70.5 ± 4.8 ± 3.7

6.8% 5.2%

70.5 ± 6.0

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Carla Maria Cattadori INFN Milano and Milano Bicocca Physics Department

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