Getting Serious about Coherent Neutrino Scattering…

1. Getting Serious about Coherent Neutrino Scattering… Coherent neutrino-nucleus scattering: • Uncontroversial Standard Model process • Large enhancement in cross-section for En< few tens of MeV (s N2, only possible for neutral current) • However, not yet measured… detector technology has been missing. Detector mass must be at least ~1 kg (reactor experiment) + recoil energy (EA) threshold <<1keV (low-E recoils lose only < 10% to ionization) • Cryogenic bolometers proposed, no success yet

2. Why should one care?(other than “because it’s there”) Fundamental physics: • Largest sn in SN dynamics: should be measured to validate models (J.R. Wilson, PRL 32 (74) 849) • A large detector can measure total E and T of SN nn determination of n oscillation pattern and mass of n star (J.F.Beacom, W.M.Far & P.Vogel, PRD 66(02)033011) • Coherent s same for all known n… oscillations observed in a coherent detector  evidence for nsterile(A.Drukier & L.Stodolsky, PRD 30 (84) 2295) • Sensitive probe of weak nuclear charge  test of radiative corrections due to new physics above weak scale(L.M.Krauss, PLB 269, 407) • s critically depends on µn: observation of SM prediction would increase limits on µn by > an order of magnitude (A.C.Dodd et al, PLB 266 (91) 434) Smallish detectors… “n technology”? • Monitoring of nuclear reactors against illicit operation of fuel diversion: present proposals (A.Bernstein et al, nucl-ex/0108001) with conventional 1-ton detectors work only above ~3 GWt reactor power • Geological prospection, planetary tomography… the list gets much wilder.

3. An experiment in search of a technology: is it already available?(J.I. Collar and Y. Giomataris, NIM A 471(2001) 254) Micropatterned Gaseous Detectors: • Technologies originally developed for HEP can find many applications in low-bckg experiments • Gains of up to 107 obtained by multi-layering • Ionization threshold in the few tens of eV, single electron detection routine even at P ~ few atm (PMTs better watch out…) • Large drift distance (TPC) and target mass possible. Room T operation. Variety of target gases. Low cost. • Minimalist construction, easy switch to low-bckg materials. • Good E resolution (e.g.,~5% FWHM @ 22keV) • Excellent spatial resolution (few tens of µm) However, no need in a coherent detector (single channel device, large active volume drifted into small amplification element) • Examples: GEMs, Micromegas, LEMs…

4. First Mass Production of GEMs Chicago-3M-Purdue Original motivation for first mass-production: Low-background applications (in particular coherent neutrino-nucleus scattering: J.I. Collar and Y. Giomataris, NIM A 471(2001) 254; Barbeau et al.IEEE TNS 50(2003)1285) SEM courtesy F. Sauli but many other applications can profit from “industrialization”: TPC readout, large-area tracking devices, X-ray astronomy, neutron physics, medical & industrial imaging, photonics...

5. Further work on 3M GEM: Chicago (emphasis low-bckg) 1. Single Electron detection with quadruple GEM 2. Self-supporting (glueless) stackable PEEK holders 3. Simultaneous charge/electroluminescence (extra PMT gain allows operation at higher P or two-phase) 4. 3M GEMs withstand T-cycling down to LN2 5. Building calibration sources for n application (also exploring other detector technologies)

6. Is there another (faster, cheaper) way?(was the humblest of all detectors waiting to be used for this?)

7. The read-out technology is already with us…cooled LAAPD have the QE, gain (single photon!) and low noise required -size is around the corner- news from industry… 45 cm2 LAAPD (!) succesfully cycled to LN2

8. Seeing is believing… even modest cooling (-50°C) of commercial LAAPDs does the job very preliminary (not optimzed yet) Single photon pulses from x10-12 filtered LED using low-noise Ortec 142AH preamp + 672 amplifier • Studies of dark pulses and QE vs. threshold under progress (~100% QE for single photon -driven by Q cryptography etc.-: Moszynski et al., IEEE TNS 49(02)971; Woodward et al., Appl. Phys. Lett. 64(94)1177; Farrell et al., NIM A353(94)176; V.N Solovov et al. (recent hep-ex). • Some backgrounds to be expected. Phosphorescence (afterglow) can be rejected via scintillator selection, coincidence and timing analysis, but imposes an effective two-photon threshold (possibly equivalent to as low as few tens of eV recoil energy in some crystals). Thermal and epithermal neutron bckgs can be controlled via shielding. • A baker’s dozen crystals to be tested (pros and cons, not straightforward to predict best)

9. Entering terra incognita(adequate calibrations a must)

10. IPNS @ ANL provides the perfect beam (pure, collimated over small area, pulsed, right intensity)

11. The next best thing to actual data(beam time Feb. 15th)

12. Can be used to calibrate GEM-based detectors as well

13. Next: filtered (monochromatic) n irradiations

14. A Fe+Al filter closely mimics recoil energies from reactor nus (J.I. Collar and Y. Giomataris, NIM A 471 (2001) 254)

15. We are not the only “serious” individuals… Coherent neutrino detection early drive for some of the most successful bolometric WIMP detectors we have today. In the news -> ~20 eV recoil threshold via Luke effect (Akerib et al.) using CDMS technology. SSG (Orpheus), crystal bolometers (CRESST)… LLNL (two-phase Argon) Case example: TEXONO…