Gno and the pp neutrino challenge
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T.Kirsten/GNO. GNO and the pp - Neutrino Challenge. Till A. Kirsten Max-Planck-Institut für Kernphysik, Heidelberg for the GNO Collaboration NDM03 Nara/Japan June 9-14, 2003 a. Solar Neutrino Energy Spectrum. GNO - Gallium Neutrino Observatory. detection of low energy solar neutrinos.

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GNO and the pp - Neutrino Challenge

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Gno and the pp neutrino challenge

T.Kirsten/GNO

GNO and the pp - Neutrino Challenge

Till A. Kirsten

Max-Planck-Institut für Kernphysik, Heidelberg

for the

GNO Collaboration

NDM03 Nara/Japan

June 9-14, 2003

  • a


Solar neutrino energy spectrum

Solar Neutrino Energy Spectrum


Gno gallium neutrino observatory

GNO - Gallium Neutrino Observatory

detection of low energy solar neutrinos

Purpose:

Basic interaction:

71Ga(ne,e)71Ge (Ethr = 233 keV)

EC, t = 16.49 days

7Be 27%

n signal composition:

CNO 8%

pp+pep 55%

8B 10%

72 SNU

35 SNU

10 SNU

Tot: 128+9-7 SNU

13 SNU

Technique:

Radiochemical

Target: 103 tons of GaCl3 acidic solution containing 30 tons of natural gallium

Chemical extraction of 71Ge every 3-4 weeks

Detection of 71Ge decay with gas proportional counters

 9 71Ge counts detected per extraction

Expected signal (SSM):

More details can be found on the webpage www.lngs.infn.it/site/exppro/gno/Gno_home.htm


Gno collaboration

GNO Collaboration

  • Dip. Di Fisica dell’Università di Milano “La Bicocca” e INFN sez. Milano

  • INFN Laboratori Nazionali del Gran Sasso

  • Dip. Di Fisica dell’Università di Roma “Tor Vergata” e INFN sez. Roma II

  • Dip. Di Ingegneria Chimica e dei Materiali Università dell’Aquila

  • Max Planck Institut fur Kernphysik – Heidelberg

  • Physik Dep. E15 – Technische Universitaet – Muenchen


Gallex

Jun 1994 – Oct 1994

1st51Cr source experiment

PL B342 (1995) 440

PL B447 (1999) 127

Feb. 1997

End of Solar Data Taking

Oct 1995 – Feb 1996

2nd source 51Cr experiment

PL B420 (1998) 114

Feb 1997 – Apr 1997

Test of the detector with 71As

PL B436 (1998) 158

Start of GNO data taking

Apr 1998 – Now

GALLEX

Construction of the detector

1986 - 1990

GALLEX I data taking

15 Solar runs, 5 Blanks

PL B285 (1992) 376

PL B285 (1992) 390

May 1991 – May 1992

83.4 ± 19 SNU

GALLEX Final Result

1594 days – 65 runs: 77.5± 7.7 SNU


Significance of deficit in time

Significance of Deficit in Time


Neutrino source exposure

Neutrino Source Exposure


Source results

Source results


Arsenic tests

Arsenic Tests

Repeated tests under variable respectively purposely unfavorable

conditions with respect to:

method and magnitude of carrier addition

Mixing-and extraction conditions

standing time

to exclude witholdings (classical or ‘hot-atom’-effects)

Method:

Triple-batch comparison:

 30 000 71As atoms in:

Tank sample

External sample

Calibration sample

(-spectrometry)

Result:

Recovery 99+ %


Gno results

GNO – Results

completed52 solar runs1547 days

still counting 7 solar runs 200 days

blanks 10 +2

GNO65.2 ± 6.4 ± 3.0 SNU

(L 70. ± 10. K 62. ± 8.)

GALLEX77.5 ± 6.2 +4.3-4.7SNU

GALLEX+GNO70.8 ± 4.5 ± 3.8 SNU


Gallex gno davis plot

GALLEX - GNODavis plot

GNO

52 solar runs

GALLEX

65 solar runs


Gallex gno seasonal variations

GALLEX +GNO Seasonal variations

Winter-Summer(statistical error only):

GNO only (52 SRs):

Winter (26 SR): 59.6+8.1-7.7 SNU

Summer (26 SR): 67.7+8.7-8.3 SNU

W-S: -8 ± 16 SNU

GNO + Gallex (117 SRs):

Winter (60 SR): 68.1+6.0-5.8 SNU

Summer (57 SR): 73.5+6.4-6.2 SNU

W-S: -5 ± 12 SNU


Improvements

Improvements

* Neural network analysis


Why sub mev neutrinos

Why sub-MeV Neutrinos?

  • Solar Physics

  • 98 % of all solar neutrinos are sub-MeV

  • ( 7 ~ 7 % , pp ~ 91 % )

  • The pp- neutrino flux is coupled to the solar luminosity. It is a fundamental astrophysical parameter that should definitely be measured, as precisely as possible. Stringent limitations (or observation) of departures from the standard solar model are obtained if the flux of pp neutrinos could be deduced.


2 neutrino physics

2. Neutrino Physics

(a) Below 1 MeV, the vacuum oscillation domain takes over from the matter oscillation domain at >1 MeV. Also there could be hidden effects only at < 1MeV (e.g., sterile admix-tures?)

(b) Narrow down on tang2θ12 .

To obtain Δ  15%, the pp-flux must be determined to  3 %


Depression factor vs energy

Depression Factor vs. Energy


Ga snu contours in the lma region

Ga SNU contours in the LMA region

Holanda + Smirnov PRD 66(2002)113005


Gno and the pp neutrino challenge

How?

The best promise is with low threshold real time experiments like

(n-e) scattering or (n, e-γ)

(e.g. Xe) e.g. In-Lens

Yet:When ???

7Be :soon (Borexino, Kamland?)pp :> 4 years (at least)

Meanwhile :

pp = GNO(pp+7Be) minus BOREXINO (7Be)!


An important a sset

An important Asset:

GNO is a running experiment. Continuation and improvements are (relatively) low cost and effort.

Yet:

How precisely can we get before the advent of real time sub-MeV data ?


Outset on which we must improve

Outset on which we must improve

(see Bahcall and Pena-Garay, hep-ph 0305159)

pp-flux: (1.01  0.02) x BP00 SSM (1)

(with luminosity constraint)

7Be-flux:(0.97 +0.28-0.54) x BP00 SSM (1)

tang2θ12 = = 0.42 +0.08-0.06

(LMA: Δm2 = ( 7.3 +0.4-0.5) x 10-5 eV2 ;

no hope to improve on this from GNO/Borexino)

fGa,cc = 0.55  0.03 (1)


Cc nc response

CC / NC Response


Determination of the pp neutrino flux from gno and borexino

Determination of the pp-neutrino flux from GNO and Borexino


Deduction of the pp flux

Deduction of the pp-flux


Survival probabilities

Survival probabilities

Survival probabilities

2

3

P (ne ne)

4

3

5

4

1

2

5

1

Ppp = 0.57 +- 10%

Ppep = 0.53 +- 5%

P7 = 0,56 +- 8%

P8 = 0.33 +- 20%

PCNO = 0.55 +- 8%

E (MeV)

C. Cattadori, N. Ferrari


Capture cross sections

Capture cross sections

Capture cross sections

n typesErr% TransitionsSignal/SSM % Errors from s

10-46 cm2%GS 1,2 >2(with MSW LMA) GS 1,2 >2

pp11.72+- 2.3100 - - 0.311

pep204-7 +17 82 6 12 0.012

7Be71.7-3 +7 94 6 - 0.150

8B24000-15 +32 12 6 82 0.030

N60.4-3 +6 94 6 - 0.014

O113.7-5 +12 86 6 8 0.023

TOT 0.541 +-2.1 -0.4+1.7 -0.9 +3.5


Future plans in gno

Future Plans in GNO


Future neutrino source exposures

Future Neutrino Source Exposures


Source feasibility and status

Source Feasibility and Status

An intense feasibility study, including test irradiations with actual GALLEX enriched chromium, revealed that the RIAR reactor research institute at Dimitrovgrad (Russia) can produce sources up to 6.5MegaCurie with the available material.

The immediate project is a 3MCi source for GNO (next major experimental step)


Quotation of j bahcall

Quotation of J. Bahcall

„Simple neutrino scenarios fit well the existing data, which – with the exception of the chlorine and gallium radiochemical experiments – all detect only solar neutrinos with energies above 5 MeV.

Perhaps these higher energy data have not yet revealed the full richness of the weak interaction phenomena.”

Nucl.Phys. Proc. Suppl. B118 (2003) 86


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