Getting Serious about Coherent Neutrino Scattering…

Coherent neutrino-nucleus scattering:

• Uncontroversial Standard Model process

• Large enhancement in cross-section

for E< few tens of MeV

( 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

Why should one care?(other than “because it’s there”)

Fundamental physics:

• Largest 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 determination of oscillation pattern

and mass of n star (J.F.Beacom, W.M.Far & P.Vogel, PRD 66(02)033011)

• Coherent same for all known …

oscillations observed in a coherent detector evidence for sterile (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)

• critically depends on µ: observation of

SM prediction would increase limits on µ by

> an order of magnitude (A.C.Dodd et al, PLB 266 (91) 434)

Smallish detectors… “ 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.

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…

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)

First Mass Production of GEMsChicago-3M-Purdue

but many other applications can profit from “industrialization”: TPC readout, large-area tracking devices, X-ray astronomy, neutron physics, medical & industrial imaging, photonics...

SEM courtesy F. Sauli

1. Single Electron detection with quadruple GEM2. Self-supporting (glueless) stackable PEEK holders3. 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 application(also exploring other detector technologiesexploring other detector technologies)

Further work on 3M GEM: Chicago (emphasis low-bckg)

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

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

Seeing is believing… even modest cooling (-50°C) of commercial LAAPDs does the job

• 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)

Single photon pulses from x10-12 filtered LEDusing low-noise Ortec 142AH preamp + 672 amplifier

very preliminary(not optimzed yet)

Entering terra incognita(adequate calibrations a must)

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

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

Can be used to calibrate GEM-based detectors as well

Next: filtered (monochromatic) n irradiations

A Fe+Al filter closely mimics recoil energies from reactor nus

(J.I. Collar and Y. Giomataris, NIM A 471 (2001) 254)

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…