future strategy of cresst · 2015. 6. 5. · smaller c via smaller crystals (25 gm instead of 250...
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FUTURE
STRATEGY of
CRESST
MPI, TUM, Oxford, Tubingen, LNGS, Vienna
Based on presentation by Federica Petricca(spokes‘man’) at Gran Sasso
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The Two Big Problems
of ‘WIMP’ search via nuclear recoils.
I Low Energy Threshold, Resolution
II Background—Remarkable progress, more needed
—————————————————–
CRESST is undertaking new radical steps on thesetwo fronts
Optimize on small recoils
• low WIMP masses
• other applications
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I
The Recoil Energy is small
From astro we believe we know velocity
v/c ⇡ 2⇥ 10�3
Given velocity, smaller mass means smaller energyfor WIMP ! smaller recoil for Nucleus
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Mwimp = 50 GeV
Mwimp = 10 GeV
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Cryodetectors
At LOW T a little energy can mean a lot!
Solid state, liquid detectors: energy unit ⇡ 1 eV
But cryo devices: e.g. superconductor, energy tobreak Cooper pair ⇡ 10�4 eV
CRESST operates around 10 milliKelvin. Transitiontemperature of Tungsten thermometer ⇡ 14 mK.
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The “superconducting strip” or “transition edge sen-sor (TES)”
Crystal = CaWO4
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Great E resolution, low threshold
Still not down to fat part of recoil curveespecially for light WIMPs
New generation of CRESST detectors aim to getthere
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Principle: �T = �E/C, C very small at low T
New Generation of CRESST detectors
Smaller C via smaller crystals (25 gm instead of 250 gm)
Red: Light signal, same in both
White: Phonon signal, small/big crystal
from Raimund Strauss
Get to 100 eV recoils
Can see WIMP masses below 10 GeV
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II
Two-channel readout separates (�, e) fromnuclear recoils
Heat (phonons) and Light
Events are represented as points in heat-light plane
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Beige= WIMP signal region
Group around 100 KeV210Po !206 Pb (103 keV )+↵ (5.3MeV ) (from Radon)
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Great Improvements
• Radon control
• Radiopurity (own crystal lab)
• New innovative class of detectors withscintillating clamps
206Pb (103 keV ) was hitting metal clamps
– Nothing that doesn’t scintillate
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From only one stick- module: In latest publishedresults yellow region (where WIMPS expected) isessentially empty [ arXiv:1407.3146. Eur.Phys.J. C74 (2014) 12,
3184]
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latest and greatest
I-sticks
Hits on outer stick ends are identified
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•CRESST will have outstanding performance in low-recoil, low WIMP mass region.
Could maybe even reach level set by⌫ background
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• Di↵erent nuclei in one detector Ca, O, W
One of few ways to make a positive signalconvincing