ePHENIX forward tracker resolution “study”

in EicRoot framework

Alexander KiselevEIC TF meeting, BNL Sep,26 2013

Sep,26 2013 A.Kiselev

Contents ePHENIX surprisingly good fwd tracker resolution “puzzle” Comparison to the dedicated EIC detector ePHENIX realistic resolution plots in EicRoot framework

Summary

Sep,26 2013 A.Kiselev

ePHENIX fwd tracker resolution (LoI)

-> expected sp/p as good as ~3% at h = 3.0!

Sep,26 2013 A.Kiselev

EIC dedicated detector resolutionp+ track momentum resolution vs. pseudo-rapidity

-> basically the same ~2-3% at h = 3.0

Sep,26 2013 A.Kiselev

EIC dedicated detector support plot #1p+ track momentum resolution at h = 3.0 vs. Silicon thickness

-> material budget matters!

Sep,26 2013 A.Kiselev

EIC dedicated detector support plot #2p+ track momentum resolution at h = 3.0 vs. Silicon pixel size

-> detector intrinsic resolution matters as well!

Sep,26 2013 A.Kiselev

ePHENIX detector layout

ePHENIX EIC ratio

XY-planes # 5 8 5:8

Material per plane ~ 0.86% X0 ~ 0.20% X0 ~4 worse

Plane resolution ~ 50mm < 6mm ~8 worse

Magnetic field ~ 1.5T ~ 3.0T ~2 worse

Sep,26 2013 A.Kiselev

Other design considerations

sp/p (material budget) ~ 1/Lsp/p (intrinsic resolution) ~ 1/L2

well, size also matters …

-> and ePHENIX fwd tracker base (L) is at present ~3 times longer …

(assuming equidistant detector spacing and homogeneous magnetic field)

Sep,26 2013 A.Kiselev

ePHENIX mock-up in EicRoot 5x XY GEM stations at predefined locations 50 micron gaussian resolution and 0.86% rad.length per plane Either constant 1.5T or real-life BABAR-for-ePHENIX field RICH material: 1.0% rad.length entrance window & ~1m thick CF4

gas volume

p+ tracks

Track fitting using Kalman filter

Sep,26 2013 A.Kiselev

ePHENIX resolution plot #1

-> so really expect ~10% resolution at 10 GeV/c

1.5T constant field; h = 4.0; check contributions (one change at a time)

Sep,26 2013 A.Kiselev

ePHENIX resolution plot #2

-> a factor of ~3 difference in B*dl integral matters, clear

1.5T constant field; h = 3.0 vs 4.0

Sep,26 2013 A.Kiselev

ePHENIX magnetic field map

-> field rapidly falls down beyond ~1.5m from the IP

Sep,26 2013 A.Kiselev

ePHENIX resolution plot #3

-> real field gives a factor of ~2 worse results

1.5T constant vs realistic field; h = 3.0 & 4.0

Sep,26 2013 A.Kiselev

ePHENIX resolution plot #4

-> linear term ~0.7% / GeV/c (~matches LoI number)

realistic field; h = 4.0; “sp/p ~ a*p + b” breakdown

Sep,26 2013 A.Kiselev

Summary ePHENIX LoI momentum resolution numbers for forward

tracker look reasonable (but whether this resolution suffices or not for RICH-based PID at h=4.0 is a different question)

One might want to optimize dedicated EIC detector tracker layout (work started)