# Presentation: 004097

## Detector Monte-Carlo

- Goal: Develop software tools to:
- Model detector performance
- Study background issues
- Calculate event rates
- Determine feasibility of interesting experiments

## Monte Carlo

- Main components:
- Flexible interactive framework
- GEANT++  (version 3.21) to track particles through a model of a detector and surrounding matter, simulating additional interactions of particles and detector's response
- FLUKA for hadronic interactions
- Simple detector model
- Sophisticated neutrino event generator
- NEUGEN (from MINOS) embedded in GEANT
- Beam flux model

## Neutrino beam model

## MC algorithm

- Choose incident particle
- Can specify everything (type, position, momentum)
- Can choose neutrino (any type) randomly from beam model or with specified position, momentum.
- Let GEANT track particle, including secondaries
- Energy loss in scintillators is converted to light output
- Neutrinos don't interact, but sample matter distribution to calculate vertex distribution density along path.
- Choose neutrino vertex position, struck atom, and let NEUGEN generate interaction. (Can cut on final state.)
- Final state particles tracked by GEANT.
- Normalization book-keeping for rate calculations.

## Target/detector + near detector

- 2.5 m (50 modules)

- 1.5 m

- Top View

- Side View

- Near

- Tgt/det

- Beam center

## Detector module

- Polystyrene strips
- 2cm x 2cm x 1.5m
- Stacked into planes
- 1.5m x 1.5m square
- 2 planes with orthogonal alignment (X, Y axes)
- Air gap of 1cm (room for additional target material)
- Total thickness: 5 cm

- 1.5m

- 1.5m

## Target/detector in cave

- 20 m

- 25m

- 9.6m

- 5.5m

- 4m

- Top

- Side

- Beam
- center

- Cave

- Tgt

## (Idealized) Detector Response

- For each scintillator strip:
- Energy loss --> light output
- Perfect light collection for now (no loss or attenuation)
- Light from all strips is summed together (calorimeter mode) and normalized to minimum ionizing protons for an energy scale.
- Plot is for protons of momentum 1 GeV/c entering the detector. (fully contained when no secondaries produced.)

## Good charged-current event

- Top view

- Side view

- Muon

- Muon

- Proton

- Proton

## Complex event

- Top view

- Side view

## Upstream background event

-  Muon goes through detector
- Several charged particles enter the cave
- Could be vetoed by an upstream detector

## Veto of upstream background

- ME tune, NC elastic events in detector

- Any event in upstream rock

- Any event in upstream rock, vetoed by a
- scintillator lining upstream wall

## Background from walls

- LE beam overlaps walls
- Neutrons can bounce into detector and scatter, simulating a NC event
- Difficult to veto

## Background from walls

- LE tune, CC + NC events in detector

- Detector signal from CC+NC events
- anywhere in the rock

- Rock events above, vetoed by a
- scintillator detector lining upstream wall

## Neutron background

- Neutron events can look like N.C. Scattering
- May be a large background from scattering in walls of cave, especially for LE tune.
- Caveat: GEANT/FLUKA might not be very good for neutron interactions...
- Needs further investigation. (Track reconstruction may help)

## Muon side-detectors (exploded view)

- 4 layers magnetized Fe (4, 4, 6, 12.5 cm thick)
- 2 planes of plastic scintillator strips (like main detector) after each Fe layer.
- 3 configurations for magnetic field: axial, toroidal, quadrupole.

## Permanently magnetized iron

- Toroidal field, max is 3.8 kG inside special alloy.
- Field is parallel to direction of view.
- Fe is black, scint is red.
- Muon of  p = 1 GeV/c introduced in Fe.
- Should be deflected up by field, but multiple scattering is larger effect (downwards in this event.)

## Fe magnetized with coils

- Toroidal field, 20 kG in Fe.
- Field is parallel to direction of view.
- Fe is black, scint is red.
- Muon of  p = 1 GeV/c introduced in Fe.
- Deflection by field dominant over multiple scattering.

## Conclusions

- Reasonable starting point for detector simulations
- Lots of room for improvement:
- More sophisticated detector model (light collection)
- Track reconstruction from hits in scintillator
- Newer version of NEUGEN?
- Better hadronic interaction package, especially neutrons
- IMPORTANT: Needs new leader