Measurement of low energy Electronic Recoil Response and - - PowerPoint PPT Presentation

Measurement of low energy Electronic Recoil Response and Electronic/Nuclear Recoils Discrimination in XENON100

Jingqiang Ye, UC San Diego On behalf on XENON Collaboration

LIDINE 2017, Sep. 22 - 24, 2017, SLAC

1

Introduction

2 ER,NR 𝑂"# 𝑂$ S1 S2 g1 g2

g1 = S1 Nph , g2 = S2 Ne

• Scintillation signal S1
• Charge signal S2
• Different S2/S1 for ER/NR
• Primary scintillation gain g1
• Secondary scintillation gain g2
• g1 is proportional to photon detection efficiency(PDE)

ER NR

Data Extraction

20 40 60 80 100 120 140 160 180

s] µ Drift Time [

20 40 60 80 100 120 140 160 180 200 220

]

2

at Liquid Surface [cm

2

Detected Radius

Relative Light Yield to Center

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2

20 40 60 80 100 120 140 160 1800 20 40 60 80 100 120 140 160 180 200 220

FV#1 FV#2 FV#3 FV#4 FV#5 FV#6 FV#7

3 Calibration source & detector condition:

• CH3T calibration (<18.6 keVee, ER)
• AmBe calibration(NR)
• 3 different drift and extraction fields

To compare with different PDE:

• 7 sub-FVs(‘small detector’)
• 50% quantile in 𝑆&direction, equal in drift time
• Enough statistics in each sub-FV
• Avoid strong field distortion in top and bottom region
• No position dependent correction of S1 and S2
• Small S1 and S2 variation in each sub-FV(6% for S1,

5% for S2)

• PDE increases from top part to bottom part

Drift field(V/cm) Extraction field(kV/cm) Electron lifetime(us) Max drift time(us) Events in sub-FV(10)) CH3T 400 10.0 1470 ± 190 182 43.4 CH3T 167 8.2 390 ± 160 202 11.9 CH3T 100 8.2 590 ± 30 220 8.9 AmBe 400 10.0 1490 ± 100 182 3.5 AmBe 167 8.2 490 ± 130 202 3.6 AmBe 100 8.2 550 ± 60 220 6.5

Detector calibration(g1, g2)

4

E = W · (S1 g1 + S2 g2 ), W = 13.7eV S2 E = − g2 g1 S1 E + g2 W

Calibration principle: Doke method

Detector calibration(g1, g2)

Calibration result:

• g1 z dependence due to geometry effect
• g2 z dependence due to electron lifetime
• g1 is consistent under different drift fields
• g2 increases with larger extraction field

5

Xe Incoming particle Xe* Xe+ e- Xe2+ e- e- S1 S2 Fano fluctuation Gaussian 𝑂+~ N(E/W, 𝐺𝐹/𝑋

• )

F=0.059 Recombination fluctuation Gaussian r~ N(<r>,∆𝑠) Electron drift & extraction Binomial ~B(𝑂$, 𝜁4 ∗ 𝜁$6) Photon detection Poisson Recombination Binomial ~ B(𝑂7,r) r: recombination factor <r>: average recombination fraction(<r> is tuned) ∆𝑠: recombination fluctuation(Δ𝑠/<r> is tuned) 6 Excimer production Binomial 𝑂$6~ B(𝑂+, 𝛽/(1 + 𝛽))

Simulation model

MC-data matching

7 500 1000 1500 2000 2500 3000 3500 Counts

S1 spectrum (data) 15.4%-84.6% credible region

1.5 2.0 2.5 3.0 Log10(S2/S1)

Point estimation MC

10 20 30 40 50 60 70 80 S1[PE] 1.5 2.0 2.5 3.0 Log10(S2/S1)

Data ER band medians (data) ER band medians (mc)

1000 2000 0<S1<10

S2 spectrum (data) 15.4%-84.6% credible region

500 1000 1500 10<S1<20 200 400 600 800

Counts

20<S1<30 100 200 300 30<S1<40

1000 2000 3000 4000 S2[PE]

20 40 60 80 40<S1<50

100 101 102

Counts

102 103

Counts

Use Binned Maximum Likelihood Estimation(MLE) in Log10(S2/S1) vs S1 space to extract ER response

Light yield

8

2 4 6 8 10 12 14

10 20 30 40 50 hnphi/E [ph/keV] a) 100 V/cm

Best estimation ±1σ fitting uncer. Credible region NEST v0.98 LUX @ 105 V/cm

2 4 6 8 10 12 14

b) 167 V/cm

LUX @ 180 V/cm

2 4 6 8 10 12 14

c) 400 V/cm 2 4 6 8 10 12 14 4 2 2 4

• Unc. [ph/keV]

2 4 6 8 10 12 14

Energy[keV]

2 4 6 8 10 12 14

• Lower light yield at higher drift field as expected
• Consistent with LUX measurement
• Light yield deviates from NEST at high energy, especially at high drift fields

Recombination fluctuation

2 4 6 8 10 12 14

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

∆r

d) 100 V/cm

2 4 6 8 10 12 14

e) 167 V/cm

Best estimation ±1σ fitting uncer. Credible region LUX @ 180 V/cm

2 4 6 8 10 12 14

f) 400 V/cm 2 4 6 8 10 12 14 −0.03 −0.02 −0.01 0.00 0.01 0.02 0.03

• Abs. unc.

2 4 6 8 10 12 14

Energy[keV]

2 4 6 8 10 12 14

No significant change observed between different drift fields 9

ER/NR discrimination

10

• Normalize S1 to photons generated to compare ER leakage under different g1
• S2 is corrected for electron lifetime

ER/NR discrimination

ER leakage is smaller at larger g1 11

ER/NR discrimination for different g1 and drift fields

12

• S1 range(100-400 photons), energy range(11-34 keVnr)
• ER leakage is smaller at larger g1
• No significant difference for ER leakage between 100 V/cm and

400 V/cm drift field

1

g

0.04 0.05 0.06 0.07 0.08 0.09

ER Leakage Fraction

3 −

10

2 −

10 400 V/cm 167 V/cm 100 V/cm

Summary

• Light yield and recombination fluctuation for low energy under three drift field are

measured

• Light yield under 100 and 167 V/cm are consistent with LUX measurement
• ER leakage is smaller for larger photon detection efficiency
• No significant difference in ER leakage is observed between 100 V/cm and 400 V/cm

drift field

• The paper will be available on arXiv next week

13

Back up

14

• Drift field increases:
• ER/NR separation increases
• ER band width increases
• g1 increases:
• ER/NR separation doesn’t change significantly
• ER band width decreases

Recombination factor

2 4 6 8 10 12 14 16

Energy[keV]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

hri

100 V/cm 167 V/cm 400 V/cm

Black: 180 V/cm Blue: 105 V/cm

LUX Collaboration arXiv: 1512.03133 15

16 500 1000 1500 2000 2500 3000 3500 Counts

S1 spectrum (data) 15.4%-84.6% credible region

1.5 2.0 2.5 3.0 Log10(S2/S1)

Point estimation MC

10 20 30 40 50 60 70 80 S1[PE] 1.5 2.0 2.5 3.0 Log10(S2/S1)

Data ER band medians (data) ER band medians (mc)

1000 2000 0<S1<10

S2 spectrum (data) 15.4%-84.6% credible region

500 1000 1500 10<S1<20 200 400 600 800

Counts

20<S1<30 100 200 300 30<S1<40

1000 2000 3000 4000 S2[PE]

20 40 60 80 40<S1<50

100 101 102

Counts

102 103

Counts

P-value = 0.01 P-value = 0.16 P-value = 0.10 P-value = 0.37 P-value = 0.38