Semi-Analytic Approach to Light Simulation Diego Garcia-Gamez & - - PowerPoint PPT Presentation

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Semi-Analytic Approach to Light Simulation Diego Garcia-Gamez & - - PowerPoint PPT Presentation

Dec 26, 2022 102 likes •338 views

Semi-Analytic Approach to Light Simulation Diego Garcia-Gamez & Andrzej Szelc The University of Manchester 1 Introduction Optical simulation in LAr detectors is very hard: huge time and memory consuming This issue is even worse in

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SLIDE 1

Semi-Analytic Approach to Light Simulation

Diego Garcia-Gamez & Andrzej Szelc The University of Manchester

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SLIDE 2

Introduction

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  • Optical simulation in LAr detectors is very hard: huge time

and memory consuming

  • This issue is even worse in large detectors like DUNE (SP &

DP)

  • Different approaches to overcome this problem: Optical

library, hybrid library, extended library

  • We propose here a new approach: analytical/parametric

solution:

  • Very good results already demonstrated for the

time estimation (ns level)

  • We include now the estimation of the number of

photons

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SLIDE 3

Geometric approach

  • For “practical” reasons we will assume
  • ur light detector as circular disks: a

symmetric shape will make easier to generalize our results

  • Given a dEdx in a point (x, y, z) we want

to predict the number of hits in our

  • ptical detector (xi, yi, zi)
  • Isotropic scintillation emission makes

the problem “almost” geometric

  • “Almost” because we have Rayleigh

scattering

Solid angle of a disk

3

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SLIDE 4

Simulations

LAr Optical Detectors

In our studies we assume:

  • Scintillation points with 5x107 photons
  • 8” diameter disks as optical detectors
  • Argon absorption length of 20 meters
  • No photon reflections in the walls (VUV

light is highly absorbed in most materials )

  • Three different active volume sizes:

DUNE-SP like (3.6m x 12m x 14m) DUNE-DP like (12m x 12m x 8m) SBN like (2m x 4m x 10m)

  • Three different Rayleigh Scattering lengths

(i.e. spectrums centered at): ~ 60 cm ~ 120 cm ~ 180 cm

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SLIDE 5

If we assume no Rayleigh Scattering

distance [cm]

200 400 600 800 1000 1200 1400

hit

)/N

hit

  • N

rec

(N

  • 0.3
  • 0.2
  • 0.1

0.1 0.2 0.3 Poisson fluctuation

  • As expected, when switching off

the Rayleigh scattering (or for larger wavelengths like visible) the situation is pure geometry

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SLIDE 6

100 150 200 250 300 350 400 450

[nm] λ

10

2

10

3

10

4

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Rayleigh Length [cm]

Rayleigh Scattering in our simulations

Mean 63.74 Std Dev 20.23

20 40 60 80 100 120 140 160 180 200

Rayleigh Length [cm]

50 100 150 200 250 300 350 400 450

Mean 63.74 Std Dev 20.23

LAr scintillation emission:

Mean 128.0 Std Dev 3.2

Scatter-lengths plugged in our simulations

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Rayleigh scattering length @ 90K as a function of wavelength from arXiv:1502.04213 (the one in LArSoft)

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SLIDE 7

Including Rayleigh Scattering vs distance

ß Situation a lot more complex in the realistic case when Rayleigh Scattering is included (λRS ~ 60cm in this example)

Relation Nhits/Ω is more complex than a simple dependency on the distance à At a fixed distance, fluctuations are too big (unmanageably)!

à More degrees of freedom needed!

< λRS ~ 60cm > DP-size < λRS ~ 60cm > DP-size

More than 5 orders

  • f magnitude range!

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SLIDE 8

Including Rayleigh Scattering vs distance and θ

θ = angle between the scintillation point and the normal to the optical detector surface

Relation Nhits/Ω/cos(θ) reduces significantly the uncertainties, but still quite large à strong dependency on the relative position between scintillation point and the optical detector surface

/cos(θ)

< λRS ~ 60cm > DP-size < λRS ~ 60cm > DP-size

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SLIDE 9

Including Rayleigh Scattering vs distance and θ

< λRS ~ 60cm > DP-size

Modeled with Gaisser-Hillas function

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Preliminary

  • D. Garcia-Gamez
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SLIDE 10

Correcting Ω by RS(distance, θ): Dual-Phase with λRS ~ 60cm

/cos(θ)

< λRS ~ 60cm > DP-size

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Preliminary

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SLIDE 11

/cos(θ)

< λRS ~ 60cm > DP-size

Reweighting by the number of entries/opdet

Correcting Ω by RS(distance, θ): Dual-Phase with λRS ~ 60cm

No bias and better than 10% resolution, and better for larger λRS

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Preliminary

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SLIDE 12

< λRS ~ 60cm > SP-size

Correcting Ω by RS(distance, θ): Single-Phase with λRS ~ 60cm

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Preliminary

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SLIDE 13

Reweighting by the number of entries/opdet

Correcting Ω by RS(distance, θ): Single-Phase with λRS ~ 60cm

No bias and better than 10% resolution, and better for larger λRS

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Preliminary

< λRS ~ 60cm > SP-size

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SLIDE 14

Reminder: Library performance

Entries 51239 Mean 0.1649 − Std Dev 0.2322

4 − 3 − 2 − 1 − 1 2 3 4

geant4

)/Photons

geant4

  • Photons

library

(Photons 1000 2000 3000 4000 5000 6000 7000 8000 9000

Entries 51239 Mean 0.1649 − Std Dev 0.2322

Notice in SBND the PMTs are 8” diameter à voxels half size of PMT window ~15% underestimation of the photon number with a 23% global resolution

Correlation between geant4 and SBND optical library: (5cm x 5cm x 5cm voxels & 4x105 photons generated in each voxel)

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SLIDE 15

RS(distance, θ) vs λRS and detector size

Single-Phase: < λRS = 60 cm > < λRS = 120 cm > < λRS = 180 cm > Dual-Phase: < λRS = 60 cm > < λRS = 120 cm > < λRS = 180 cm >

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Preliminary Preliminary Preliminary Preliminary Preliminary Preliminary

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SLIDE 16

RS(distance, θ) vs λRS and detector size

Single-Phase Single-Phase Dual-phase Dual-phase

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Preliminary Preliminary Preliminary Preliminary

NGaisser-Hillas NGaisser-Hillas MaximumGaisser-Hillas MaximumGaisser-Hillas

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SLIDE 17

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  • We are also working in an update/

extension of the time parametrization to larger detectors like DUNE

Photon Arrival Times

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SLIDE 18

time [ns] 20 40 60 80 100 120 140 photons (direct component) 20 40 60 80 100 120 140 160

A Landau + Exponential function describes well the arrival time distributions of the direct/VUV light at any distance from the photocathode Parameterization ready in LArSoft (next weeks): par0 = Landau normalization par1 = Landau MPV par2 = Landau width par3 = Expo cte par4 = Expo tau

Arrival time distributions [reminder]

We have parameterized the time distributions à resulted only from direct transport + Rayleigh scattering

  • We have developed a parametrization to account for this in

SBND à we have validated it with the other two Short Baseline detectors: MicroBooNE and ICARUS

  • It was designed as an addition to the fast optical mode

Fit result

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Landau + Exponential Landau Landau + Exponential Landau

distance = 341 cm distance = 119 cm

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Updating the arrival time distributions

For the update we have generated 108 optical photons per scintillation point (dEdx ~ 4.2 GeV) to have the shape of the signals at very large distances

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SLIDE 20

“Landau + Exponential” vs “Landau”

  • For distance < 300 cm

Landau + Exponential model clearly describes better the signals than a single Landau

  • At distances > 300 cm

both models work similarly

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SLIDE 21

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Updating the arrival time distributions

  • Extension to large distances (> 600 cm) soon: files with

simulations at large distances ready

  • Study dependencies with different values of Rayleigh

Scattering under way

Landau + Exponential Landau

Preliminary Preliminary

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SLIDE 22

Conclusions

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  • We have developed an analytical way to predict the scintillation

light signals in LAr detectors:

  • A recipe for both number of photons and arrival time

distributions

  • We have studied and parametrized the main dependencies of

the signals:

  • Distance, angle, λRS and detector size
  • Better performance than current tools
  • We want to have an operative module for doing this in LArSoft

by the end of the summer

  • A technical paper is in preparation to explain all the details