Updates and Status of the Noble Element Simulation Technique Jon - - PowerPoint PPT Presentation

Updates and Status of the Noble Element Simulation Technique

Jon Balajthy

CPAD Workshop December 10, 2019

1

2

Noble Element Simulation Technique (NEST)

Simulation package for modelling response of noble element detectors

• Interpolates between existing calibration datasets to provide predictions

for arbitrary energies and fields

• LXe is most fully developed model, LAr is currently in development
• Collaborators from wide range of experiments and institutions

○ LUX/LZ, XENON, (n)EXO, DUNE Main webpage: http://nest.physics.ucdavis.edu/ Github page: https://github.com/NESTCollaboration/nest Several implementation platforms:

• C++ based executable
• Geant4 integration
• Python wrapper
• Online calculator

3

The NEST Physics model

NEST is a set of mostly empirical models that simulates S1 and S2 size, timing, and location The inputs required:

• Event energy and/or interaction type

○ Beta/Compton (spectra for H-3 and C-14 included) ○ NR (AmBe, B-8, WIMP, neutrons) ○ Kr-83m ○ Heavy Ions ○ Alphas ○ Photoabsorption

• Drift field profile (can be a constant or a detailed map)
• Detector parameters (g1, g1_gas, density, extraction efficiency, etc.)

4

Current Status

5

Very brief overview- more detailed information available at NEST website (http://nest.physics.ucdavis.edu/) Also see Greg Rischbieter’s talk from DANCE conference (https://indico.cern.ch/event/824917/contributions/3571627/att achments/1934381/3205056/NEST_DANCE_GR.pdf)

Nuclear Recoil Yields

Same yields model used for WIMPs, D-D, B-8, Cf, AmBe Recent data from LLNL improves model at low energy

6

• M. Szydagis. (NEST Collaboration) A Comprehensive,

Exhaustive, Complete Analysis of World LXe NR Data With a Final Model. 2019. Need Ly data in <1keV region

Electron Recoil Yields

Currently divided into two(ish) parts:

• Compton/beta yields
• Photo-absorption
• Also includes special case of Kr-83m

Ly and Qy are complementary, (Ly = 1/W - Qy)

7

photoabsorption

beta/Compton

Ions and alphas and krypton, oh my!

alpha-NR Heavy Ions Kr-83m

8

Resolution Model

9

Improved Modeling of β Electronic Recoils in Liquid Xenon Using LUX Calibration Data LUX Collaboration (D.S. Akerib et al.). Oct 9, 2019. 17 pp. e-Print: arXiv:1910.04211 [physics.ins-det]

LUX C-14 LUX D-D NEST doesn’t just do mean yields! Fluctuations from recombination + detector resolution, tuned to match band means+widths

Recent/Ongoing Updates

10

• 1. LArNEST
• 2. Low energy NR model
• 3. ER model overhaul
• a. Inner shell interactions (nu-e, EC)
• b. Compton vs beta
• 4. Work Function

LAr ER Model

11

Coming soon! Models based on LXe equations and fit to LAr calibration data

LAr NR Model

12

NR, too! Low energy behavior modeled after LXe measurements

Low Energy NR Model

13

New data from Livermore improves sub-keV Qy, but Ty and Ly are still unknown

Need total yields measurements in sub-keV region

• Low energy behavior could trend high or

low

• Difficult measurement to make due to

small LY at low E NR

Lenardo, Brian, et al. "Measurement of the ionization yield from nuclear recoils in liquid xenon between 0.3--6 keV with single-ionization-electron sensitivity." arXiv preprint arXiv:1908.00518 (2019).

ER-Model Overhaul

14

• Re-fit beta model using C-14 from LUX and H-3 data from

XENON and XeLDA

• (?)Separate beta and Compton models
• Develop new electron capture/ nu-e scattering model

Beta vs EC

15

XeLDA detector at FNAL observed offset of H-3 vs Xe-127 L-shell capture Primary decay mode: 5.1keV is divided ~evenly between 6 electrons

• > Higher dE/dx means more recombination

Slide from Dylan Temple’s TAUP talk

Beta vs EC

16

This effect was also observed in LUX, but was within systematic error. Is not observed in K, M, or N shells ER->NR leakage fraction for L-shell captures increases from ~0.5% to ~3% Leads to ~20% increase in neutrino burden in LZ G3 experiments will have O(10,000) 𝜉-e scatters (~7% are 𝜉-L, or ~1,000 events) XeLDA result predicts ~30 leaked events vs. ~5 for current NEST

Preliminary plot from Dylan Temples Identical

• ffset in LUX

and XeLDA

Need to develop L-shell NEST model

• Measurements limited to < 300 V/cm
• Direct 𝜉-e measurements could be

informative

Beta vs Compton

17

Possibly a similar effect in Compton scattering vs beta decay Tritium data is very consistent, but NEST tends to overshoot at high field

• > Comes from previous lack of beta data above 180 V/cm

~100 V/cm 150-180 V/cm ~275 V/cm 330-366 V/cm

Beta vs Compton

18

Compton data is also consistent, but disagrees with all available beta data No strong physical explanation for disparity

~180 V/cm ~410 V/cm ~500 V/cm ~2000 V/cm

Need to investigate possible split of CS/beta models

• Compton/beta measurements from the same detector would cancel any

possible systematic effects (possibly forthcoming from XeLDA?)

W-value: New EXO result

19

Density (g/cc) W (eV/quantum)

The new EXO yields calibration includes a measurement of the average work function (W) Disagrees with accepted results by ~15% Existing measurements of W agree with 13.7 +/-~0.2 eV

arXiv:1908.04128v1

Note: mass density shown, but # density is important. EXO effective density is 2.9 g/cc. Most commonly cited: Absolute measurement from E. Dahl Not listed: 13.4 +/-0.4 eV from neriX. W floated in MC fit.

W-value: Excess light yield?

20

Need more measurements

• Want to verify our explanation
• If confirmed, IR scintillation will need to be measured

and modeled. A structured 35% effect might change the field/energy dependence, or even break the combined energy model (no more 1:1 recombination?)

Points include CS and photoabsorption, so expect to fall between beta and gamma Qy seems ~correct, while Ly is high

• > Additional IR photons detected by APDs?
• > Add 35% to Ly for silicon PDs
• > Adding ~15% to both Ly & Qy doesn’t work

(Green is modified NEST model )

Least kludgy method- assumes everyone is right IR scintillation is expected (but not this much)

arXiv:1908.04128v1

Conclusions

21

• NEST is a robust set of empirical models that currently

matches all world data to ~10% (most places much better)

• There are still several open questions caused by lack of

data/ contradictory data

• a. Total yield of low energy NR- Data does not exist
• b. L-shell interactions- Known to differ, but only measured

at 2 fields in Xe-127 EC

• c. Beta v. Compton- All available data shows ~10-20%

discrepancy.

• d. W value- Few absolute measurements available.

Those that exist disagree by ~15%. Might be explained by detector effects

Extra Slides

22

IR Scintillation in LXe

23

SD 630-70-75-500 APDs PMT cutoff DOI:10.1016/S0168-9002(00)01249-3

Significant IR scintillation is observed in GXe (~= VUV) Few direct measurements in LXe (none at wavelengths <1um ) Only measurements show LXe << GXe for IR scintillation

Need ~17 ph/keV NIR to explain EXO result

• GAr NIR yield is 17.5 ph/keV (Xe is higher)
• LAr yield is ~0.5 ph/keV (times ~30% QE)
• LXe NIR yield needs to be ~50x yield in LAr

( A Bondar et al 2012 JINST 7 P06014 )

The NEST Physics model

1.

• a. Draws number of quanta given

event type/energy/field

• b. Divides into Ne, Nγ according to

mean yields model + recombination fluctuations 2. Propagate photons and calculate S1 size/timing ○ Pulse shape model is included ○ Detailed hit-mapping is in development 3. Propagate electrons calculate drift time and S2 size

+ + + -

• *

*

EExtraction Liquid Gas EDrif

t

e- e- e- e- e-

24

Recombination Model

25

Recombination is integral to the observed

• f charge and light yield

Note that recombination does not affect the total number of quanta.