Test of 1kg point contact detector and CDEX-1 Data Analysis Process Wu Yucheng CDEX collaboration Development of High Purity Germanium Detector Techniques for Applications in Fundamental Universitaet Tuebingen

Outline System Setup System Performance Data Analysis Summary 2 Detector Shielding Electronics Energy linearity (Calibration) Energy resolution Decays of characteristic X-rays Data quality check Background & Microphonics Cut Physics Interpretation

System Setup: Detector 1kg-PPCGe (Canberra ) 1kg (Φ62.2×62.3, 187cm 3, 994g) Dead Layer: < 0.5mm/Ge (Canberra) P-type Crystal P + Point Contact (few mm, few pF) HV: V Pulsed Optical Reset preAMP (P + Contact) RC Feedback preAMP (N + Contact, HV module) Cryostat: OFHC, 1.5mm Dewar: 30L (LN 2 Holding time – 14 days) 3

System Setup: Shielding System 4 PE Pb PE(B) Cu Rock  PE  Pb  PE(B)  Cu CJPL 2400m1m20cm

System Setup: Electronics Systematic Setup 5 1kg-PPCGe Pulsed optical feedback Preamplifier Spec AMP Discriminator Logic Random Trigger Pulser FADC VME BUS PC Trigger VME Crate NIM Crate Resistive feedback Preamplifier Timing AMP HV Supply 6μs/12μs 10ns(int.) Spec AMP 2μs Fast Pulse Slow Pulse S1 S2

Energy Linearity 6 System Performance: Energy linearity SourceE /keV RT0 152 Eu Eu Eu Eu Eu Eu SourceE /keV RT0 68, 71 Ge Zn , 71 Ge SourceE /keV RT0 152 Eu Eu Eu SourceE /keV RT0 152 Eu Eu Eu Eu Eu Below 12 keV: Intrinsic Background; 0.3 – 3 MeV: 152 Eu sample.

System Performance: Energy resolution Energy Resolution keV keV

System Performance: X-ray Decay 8 Cosmogenic isotope:Lifetime” 68, 71 Ge:K-shell EC X-ray : keV 68 Ge: day L-shell EC X-ray : 1.29 keV 71 Ge: day

Data Analysis: Data Quality Check 9 S1 S2

Data Analysis: Physics Interpretation Elastic scattering 10 θ Center of mass frame WIMP Target ERER E a.Earth velocity relative to dark halo b.Quenching factor: nuclear VS electron recoil c.Form factor d.Energy resolution and threshold of detector e.Spin: dependent VS independent f.Mixed components J. D. Lewin and P. F. Smith, Astrop. Phys. 6 (1996) 87 a,b,d,fc,e,fe,f M χ = 10 GeV, σ = cm 2

Data Analysis: Physics Interpretation With WIMP signal Maximum Likelihood Method Without WIMP signal Maximum Gap Method Binned Poisson Method Conservative! 11 G. Savage, et al, JCAP. 04 (2009) 010

Data Analysis: Physics Interpretation 12 Predicted Anti-Compton Surface/Bulk

Summary 1kg-PPCGe has been set up System performance is good Energy Linearity; Energy resolution; Threshold; Decays Data analysis is processing Quality check  Background subtraction  Physics interpretation Optimistic physics result 13

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