NOSTOS Neutrino studies with a tritium source

1. NOSTOSNeutrino studies with a tritium source • Neutrino Oscillations with triton neutrinos • The concept of a spherical TPC • Measurement of the angleq13 ,Neutrino magnetic moment, Neutrino decay, Weinberg angle measurement at low energy, Supernova sensitivity • The first prototype • Conclusions I. Giomataris

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3. The idea Study neutrino-electron elastic scattering with very-low energy neutrinos from a strong tritium source (En≈14 keV) Detect low energy electron recoils (Tmax = 1.27 keV) by a spherical gaseous TPC surrounding the tritium source The oscillation length is shorter than the length of the detector The modulation will be contained and seen in the TPC Reconstruction of the relevant oscillation parameters by a single experiment I. Giomataris, J. Vergados, hep-ex/0303045 J. Bouchez, I Giomataris DAPNIA-01-07 I. Giomataris

4. The new strategy (I. Giomataris, J. Vergados, hep-ex/0303045) L13 = 4pEn/dm232dm232= 2.510-3, En=14 keV L13 = L12/50 = 13 mfully contained in the TPC (radius=10m) New challenge : q13 measurement The sensitivity depends on statistics, backgrounds and systematics >104 neutrino-electron interactions must be detected and localized Tritium source activity can be measured on-line at <1% Background level can be measured and subtracted (source on-off) Fitting the oscillation will suppress systematics I. Giomataris

5. NOSTOS Neutrino OScillation Tritium Outgoing Source • 200 Mcurie T2 source • 3000 m3 spherical TPC volume • 5x1030 e- with Xe at p=1 bar I. Giomataris

6. The advantages of the spherical TPC • Natural focusing system reasonable size detector • Provides a full 4p coverage enhancement of the detected signal • Allows a good determination of the depth of the interaction point by measuring the time dispersion of the signal: • The electric field isV0 = the applied high voltage, • R1= the internal radius, • R2 = the external radius • st = sL/vd,sL = D√r • At low fields: vd ≈ E and D ≈1/√ Est ≈ 1/E3/2 ≈ r3 • The time dispersion is highly enhanced in the spherical case • Estimation of the depth of the interaction < 10 cm I. Giomataris

7. Two Micromegas signals at 3 mm distance in depth 3 mm drift Precise determination of the depth I. Giomataris

8. Low energy spectrum from Micromegas in CAST Cu Fe Cu escape Ar Fe escape I. Giomataris

9. Energy distribution of detected neutrinos, Eth = 200 eV 14 keV I. Giomataris

10. Detected neutrinos-versus distance, sin22q13=.17, Eth=200 eV The effect of the unknown neutrino energy distribution is small Fitting the curve we extract the oscillation parameters with a single experiment I. Giomataris

11. Neutrino-electron elastic scattering cross section G.’t Hooft, Phys. Lett. B37,195(1971) ne ne ne ne w- z0 e- e- e- e- For T<<1 keV ds/dT = a(2sin4qw+sin2qw +1/4) High accuracy measurement of the Weinberg angle at very-low energy!! Test the weak interaction at long distances I. Giomataris

12. Neutrino magnetic moment sensitivity ds/dT≈ (mn)2(1-T/En)/T 3 2.5 -47 *10 2 2 -12 s d /dT(cm /keV) m 10 B 1.5 1 weak 0.5 0 0.01 0.1 1 2 T (keV) << 10-12mB Actual limit 10-10mB I. Giomataris

13. Target properties with 5.1030electrons, 1000 events/year Noble gas Pressure (bar) W(eV) Radioactivity Comments Xe 1 16 85Kr It needs high purification Expensive Ar 3 26 42Ar T=33y,Emax=565keV Low cost 42Ar activity: <1000/y below 1keV Ne 5.4 36 None Moderate cost He 27 41 None Low cost Very high pressure Reasonable goal: operate with Ar or Ne at pressures >10 bars >104events/year to tackle a total number of events of 105 Good news : The HELLAZ prototype provide gains of about 106 with He at 20 bar I. Giomataris

14. Supernova sensitivity Detect recoils from coherent neutrino-nucleus interaction High cross section: s ≈N2E 2 ≈ 2.5x10-39 cm2,Xe and E=10 MeV Assuming a flux of 1012/cm2 of a typical supernova and the spherical TPC filled with Xe : ≈ 280 detected with Xe at 1 bar ≈ 2,800 at 10 bar pressure!!! The challenge is again the low-energy threshold detection Tmax = 1500 eV Tmean = 508 eV Detection efficiency independent of the neutrino flavor Extra galactic supernova detection ? To be studied I. Giomataris

15. Plans • 1.3 m prototype is under construction • - Laboratory study of the radial spatial accuracy • - Laboratory study of the electron attenuation length • First investigations on the availability of the tritium source • High gain operation of the detector at high pressure operation must be investigated with various gas candidates I. Giomataris

16. NOSTOS 1rst prototype • Schedule • 2003-2004 • Laboratory tests • From 2004 • Operation in underground laboratory I. Giomataris

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19. Tests and studies with the 1.3 m prototype • Laboratory tests with various gas mixtures up to 5 bar • Total mass 1 - 25 Kgr (He, Ne, Ar, Xe, CF4) • First underground investigations • Measure the background level in the sub-keV range • Optimize the detector parameters, pitch, pulse shaping, gas mixture etc.. • If the background level is satisfactory • Search for low mass dark matter candidates • Search for WIMPs trapped in the solar system • WIMP search in spin dependant interactions (CF4 target) • Possible investigations with reactor neutrinos : coherent neutrino-nucleon scattering (>100/day detected neutrinos) I. Giomataris

20. Summary and Outlook • The purpose of the new experiment is to establish the phenomenon of neutrino oscillations with a different experimental technique and measure the angle q13 • High sensitivity measurement of the neutrino magnetic moment • Measurement of the Weinberg angle at very-low energy • High sensitivity for supervova neutrinos • Increase as much as possible the gas pressure will provide very-high statistics I. Giomataris