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Retrospect of GALLEX / GNO

Retrospect of GALLEX / GNO. Retrospect Recent update 3 Why did we stop?. Till Kirsten Max-Planck-Institut für Kernphysik Heidelberg / Germany. 1 RETROSPECT. GALLEX / GNO , SAGE Radiochemical Method (product accumulation) Ga 71 +  e  Ge 71 + e -

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Retrospect of GALLEX / GNO

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  1. Retrospect of GALLEX / GNO • Retrospect • Recent update • 3 Why did we stop? Till Kirsten Max-Planck-Institut für Kernphysik Heidelberg / Germany

  2. 1 RETROSPECT GALLEX / GNO , SAGE Radiochemical Method (product accumulation) Ga71 + e  Ge71+ e- Low threshold! (0.233 MeV) recall: Cl- experiment Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  3. Conception of the Gallium Neutrino Experiment GALLEX (later GNO) detection of low energy solar neutrinos Purpose: Basic interaction: 71Ga(ne,e)71Ge (Ethr = 233 keV) EC, t = 16.49 days 7Be 26% n signal composition: CNO 7% pp+pep 57% 8B 10% 72 SNU 33 SNU 9 SNU Tot: 126+9-7 SNU 12 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): Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  4. Why sub-MeV Neutrinos? • 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 must definitely be measured, as precisely as possible. Stringent limitations (or obser-vation) of departures from the standard solar model can be obtained if the flux of pp neutrinos is deduced, provided that, • as it is now possible, neutrino properties are properly folded in. Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  5. Below ~1-2 MeV, the vacuum oscillation domain takes over from the matter oscillation domain at > 2 MeV. Also there could be hidden effects only at < 2 MeV from C. Pena-Garay Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  6. Radiochemical experiments • cumulative measurement of the integral solar neutrino interaction rate (as opposed to real-time event detection) • no spectral or directional information After long time operation of these first generation experiments (Cl, Ga), the statistical errors equal the intrinsic systematic errors. The success of these experiments implies their end. However, they have been crucial in paving the way into the excitement of the third millenium! Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  7. 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 GNO data taking Apr 1998 – Apr 2003 GALLEX/GNO Time Table 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 PL B490 (2000) 16 PLB B616(2005)174 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  8. Granada, June 8th, 1992 • GALLEX announces first observation • of solar pp-neutrinos at „Neutrino 92“ Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  9. de Rujula Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  10. GALLEX RESULT IMPLICATIONS (1992) PL B285 (1992) 376  60 % of the SSM expectation Definite deficit of 7Be (or pp-) neutrinos observed  105 % of pp- expectation Hydrogen fusion in the solar interior experimentally observed Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  11. Significance of Deficit in Time Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  12. GALLEX Final Result 1594 days – 65 runs: 77.5 ± 7.7 SNU Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  13. Cr source experiments Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  14. Cr source results Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  15. Arsenic Tests • Repeated tests under variable and purposely • unfavorable conditions respective to the • standing time • mixing- and extraction conditions • method and magnitude of carrier addition • to exclude witholdings (classical or ‘hot-atom’-effects) • MethodTriple-batch comparison •  30 000 71As atoms added to: • Tank sample • External sample • Calibration sample (-spectrom.) • Result: • Recovery 99+ % Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  16. GALLEX + GNO results GNO 58 Solar runs = 1713 d 12 Blank runs GALLEX 65 Solar runs = 1594 d 23 Blank runs 77.5 ± 6.2 ± 4.5 SNU 62.9 +5.5–5.3 ± 2.5 SNU 51Cr source-,71Asexperiments Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  17. FINAL RESULTS GNO 62.9 ± 6.05.9 SNU GALLEX 77.5 ± 7.67.8 SNU GALLEX+GNO 69.3 ± 5.5 SNU SAGE 66.9 ±5.35.0SNU Range of SSM predicted rates: No oscillations: 122 – 131 SNU Withoscillations 68 – 72 SNU (global fit) Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  18. 2 RECENT UPDATE • Results of a recent complete re-analysis of the Gallex data * • (using ~105 Ge-decays per counter) not allowed • before completion of the low rate measurment phase • (solar runs) • Improved Rn-cut efficiency (multi-year low-rate • Counter efficiency error reduction after full calibration • experiment) • full PSA instead of RTA • Also for Cr-source data • Counter efficiency error reduction after full calibration • (as above) • solar subtraction to include also GNO data * F. Kaether, PhD Thesis, Heidelberg University, July 2007 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  19. GALLEX Periods(new vs. old) old (RTA) new (PSA ect.) Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  20. Updated Results GALLEX 77.5 ± 7.67.8 SNU re-evaluated 73.1 ± 7.17.3 SNU GNO (unchanged) 62.9 ± 6.05.9 SNU GALLEX+GNO 69.3 ± 5.5 SNU re-evaluated 67.5 ± 5.1 SNU Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  21. Cr- source update Mean S1+S2: 93± 8% (1)Gallex PL (1998) Re-evaluated:88 ± 8% (1) Thesis Kaether (2007) The expectation value for ground state only is 95 ± 1% Bahcall PR C (1997) Our 71As-experiment excludes Ge-yield errors >1% Consequences  The excited state contribution is probably close to 0,instead of (5 ± 3)% as estimated by Bahcall. Supported also by the SAGE Cr-source result.  The 71Ge production rate prediction on Ga (without oscillatons) must be reduced by ~2 SNU from 7Be- (32.7 SNU instead of 34.8 SNU). [no change for pp-] Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  22. Oscillation parameters If the LMA(MSW) solution is the correct explanation of the SNO/SK data, then vacuum oscillations must dominate below 1 MeV and the mixing angle is estimated as  = 32  1.6 degrees (B-PG04) From our data we extract the e-e survival probability Pee for pp-neutrinos after subtraction of the 8B and 7Be contributions based on the experimentally deter-mined 8B- (SNO/SK) and 7Be- (Borexino) neutrino fluxes as Pee(pp only)= 0.52 ± 0.12 THE RESULTS IMPLY THE EXPERIMENTAL VERIFI-CATION OF THE SOLAR MODEL AND OF THE NEUTRINO OSCILLATION MECHANISMNS AT sub-MeV ENERGIES THAT ARE OTHERWISE INACCESSIBLE Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  23. Partitioning of the Gallium Cake (Experiments, SSM and LMA) Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  24. 3 WHY DID WE STOP? • Reasons that existed to continue GNO • as long as real-time pp-neutrino detection was • (and still is) a long way to go • Continous pp-neutrino monitoring is an astrophysical necessity • pp-observations simultaneously with Borexino real-time beryllium neutrino observations • Further neutrino source experiments to improve the knowledge of relevant cross sections Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  25. Reflections on the causes for the termination of the experiment Quote:„The Gallium Neutrino Observatory (GNO) is the price that Italy‘s underground lab is paying to get back on its feet after a small chemical spill nearly two years ago“ (Toni Feder, Physics Today, May 2004) No confusion: The spill occured in Hall C (Borexino) GALLEX/GNO (in Hall A) never spilled a single drop of liquid. Ironically, GALLEX introduced the double spill tray safety conception in 1986, almost 20 years before it now became mandatory for the Laboratory The GALLEX corpse feeded Borexino for survival (the laws of nature) Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  26. The End (Gallium was sold in April 2007 to Recapture Metals Inc., Ontario, Canada) April 6, 2005 : GNO17, the last regular (semi-annual) GNO meeting was held in Assergi Febr 28, 2006: Final Celebration Ceremony for GALLEX/GNO at Gran Sasso, ending a successful fifteen year period that started with the Inauguration Ceremony on November 30, 1990 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  27. GALLEX-Inaugurationat GRAN SASSO 30.11.1990 The Future In n… years: Determine pp-neutrino flux directly with low threshold real-time experiments (Xe, Borexino,…?) n = 3,4,5,6…? Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  28. In memoriam Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  29. Luciano Paoluzi† 2002 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  30. Michael Altmann† 31 July 2006 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  31. Nicola Ferrari† 31 July 2006 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

  32. Keith Rowley† 29 October 2006 Till Kirsten, Max-Planck-Institut für Kernphysik Heidelberg, at TAUP 2007, Sendai September 11–15, 2007

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