Hough Map Improvement 2016 7 14 Outline Distinguish

Hough Map Improvement 2016 -7 -14

Outline • Distinguish (+ - ) charge of track on Hough space • Study the track width on Hough space

1. Improved method on Hough space • In the first step , only use axial hits to fill Hough space • Imformation of slant of sin curve ->split a hole circle to 2 half circle ρ Hits on 1 st half and 2 nd half have different sign of slant when there appears a track A pievent θ • From mathematical derivation , we can distinguish a hit on which side of the circle by (sign of slant) *(sign of ρ)

Improved method on Hough space • select 1 st half hits on track -> get hits of clockwise -> get a candidate track of negative charge • select 2 nd half hits on track -> get hits of anticlockwise -> get a candidate track of negative charge • So split a Hough. Map into two charge - charge map + charge map

Algorithm Procedure Hough. Hit. List Hough. Map - Hough. Map + Peak finding Determine track Determine whether from same track

Why • Solve Back to back events for high pt • For low pt , decay and energy lose of the 2 nd hits spoil the circle finding Not focus one area

2. Track width determination • Different kinds of hits • • • Noise hit Hit on decayed track Hit from delta e 2 nd half hits on a track circle 1 st half hits on single turn track • To study the width of the track • • No decay & delta e track No background Single turn track Only take 1 st half hits into consider

2. Track width determinationρ • Only use axial hits ->more focused area • My suppose • Method • Find the most focused area θ • Cut Hough. Map to as many bins( 500*500) • The highest bin (ρ, θ) should be the parameter of the track Compare the peak with the track par from MC truth 500 single curve events (no decay and delta e) ρ - ρTruth θ - θ Truth Parameters (ρ, θ) explain the parameter of track on BESIII x-y space ρ -> 1/r , θ->angle on x-y plane The highest bin on Hough. Map can similar express the track

Track width determination • Method • Extend the size bin by bin from two directions around the highest bin • confirm the size of peak at least include 70% hits of the track • For one event , the size of the peak is recorded by (theta. Num, rho. Num) 500 single curve events (no decay and delta e) Thetabin. Num rhobin. Num theta. Num: peak need to combine number of bins along theta axias rho. Num: peak need to combine number of bins along rho axias If we use cut peak width by (4, 4) 84% events has collected more than 70% useful hits

Track width determination procedure Cut Hough. Map to 500*500 (as small) Look for the highest bin No If (collected hits>70% of all hits) Yes theta. Num++ Or rho. Num++ Combine highest bin with bins around it Record theta/rho bin. Num

Hit tracking efficiency hits proportion 50% 60% 70% 80% 90% 100% Efficiency 94. 2% 89. 7% 83. 5% 64. 5% 39. 5% 21% Means 94. 2% events find more than 50% useful hits

Track width varied with ρ • The track width should be some distribution in Hough. Map • Along θ direction track are no difference • Along ρ direction , has some difference , but not clear • Under studying