# Presentation: 480992

## Hub and Spoke Algorithm: 1 Electron, 2 Electron, Red Electron, Blue Electron

- Presentation by
- David Miller, SUNY-Stony Brook REU ’08
- Mentor: Professor Thomas Hemmick

## Algorithm Ideas

- Old: **Clustering**
- Clusters could grow to any size or shape
- Fails with scintillation

-    New: **Hub and Spoke (HnS)**
- - Reconstructed electron location is used as center for search region
**Hub**: multiple-pad sum at center
**Spoke**: multiple-pad sum at some R and phi away from center

## Two Possible Pad Sizes: 3 vs 7

- - Two options that are presently coded

## Definition Spoke Radius (SR)

- Spoke Radius: The number of hexagon centers away from the hub, the algorithm will search for a spoke.
- Defined slightly differently for 3-tuple vs 7-tuple (See following diagrams)

## Three-tuple definition of SR

## Seven-tuple definition of SR

## Basic Algorithm Parameters

- Size of Hub
- 3-tuple or 7 tuple? Or some other geometry?
- Size of Spoke
- Area of search region
- 	- What spoke radius to use?

## Size of Hub\spoke

- Small Hub (3-tuple)
- 	-  Less collected scintillation -> less variation due to scintillation
- 	-  Lose some Cherenkov response. On average lose 92% of response (see next diagram)
- Large Hub (7-tuple)
- 	-  Never miss Cherenkov response
- 	-  Large Scintillation. 3-tuple seems preferred for this reason.

## Slide 9

## 3 vs 7 tuple; Size of Spoke

- Three-tuple vs seven-tuple
- Three-tuple seems preferred due to less scintillation
- Three-tuple’s smallest possible spoke radius (without overlap with hub) is 2, vs the seven-tuple’s 3. (See slides 5&6)
- Size of Spoke
- As presently coded, sizes of hub and spoke are equal
- Could imagine a 7-tuple hub and 3-tuple spoke

## Spoke Radius

- Large radius
- Pick up false physical electron or large noise fluctuation
- Single electron events will be misclassified as double

-  Small radius
-  Miss true Dalitz partner (see next diagram)
-  Dalitz decays will be misclassified as single

## Opening Angle Distribution In Spoke Radius Terms

## Ingredients

- Pi0 Dalitz Conversions: Read from file created by Exodus, realistic momentum distribution.
- Single (Signal) electrons: Read from same file, but only one electron from a decay is kept
- Scintillation: Spread uniformly across HBD, ranges from 0.0 – 2.0 scintillation photon per pad
- Hadrons: No ionizations, but hadrons were spread uniformly and their locations were used as a response to “zero” electrons

## Note:  100 Cherenkov photons used to help to train the intuition.

- Note:  100 Cherenkov photons used to help to _train the intuition_.

## Slide 15

## Slide 16

## Slide 17

## Slide 18

## Slide 19

## Doubles Spoke Radius = 2

**Doubles Spoke Radius = 2**

**Doubles Spoke Radius = 5**

## Singles Spoke Radius = 2

**Singles Spoke Radius = 2**

**Singles Spoke Radius = 5**

## Hadrons Spoke Radius = 2

**Hadrons Spoke Radius = 2**

**Hadrons Spoke Radius = 5**

## Singles

**Singles**

**Doubles**

## Spoke Radius: Discriminator?

## How to make decisions

- One possible way - **TMVA**: Hub, spoke, and central-electron-to-spoke distance may be put in as a training tree into this multivariate analysis package
- For a given hub, spoke, and spoke distance TMVA will output a number from
- 	-1 to 1 indicating signal-like or background-like
- Cut is made on this classifier at some desired signal survival rate