Minimum BiasLow Pt Tracking

W. H. Bell

08/02/2007

Overview

Motivation Recap Low Pt Tracking

Objectives Steering reconstruction Track Quality Cuts

MBTS Trigger Efficiency Conclusions and Outlook

Motivation

Predictions of dN/dη at LHC uncertain Compare NSD with previous results Use minimum bias measurement as a Monte

Carlo tuning input and for pile-up studies.

LHC Predictions

σmb approximately 65mbIntegrated luminosity of 10pb-1 => 1012 Events

Minimum Bias Trigger Scintillators

inner inner ηη

outer outer ηη

2 segments in η8 segments in φ

2.0 < η < 3.8

Recap ε

ε

From Generator Truth, requiring a Lvl1 MBTS trigger

Inelastic non-diffractive

Inelastic Double and Single Diffractive

Low Pt Tracking Tracker is in principle sensitive to soft tracks

Pt = 400 MeV - tracks reach end of TRT Pt = 150 MeV - tracks reach last SCT layer Pt = 50 MeV - tracks reach all Pixel layers

150MeV50MeV 400MeV

A.Salzburger - Fatras simulation

Low Pt Tracking: Steering Reconstruction InDetRecExample provides examples Implement via modified

RecExCommon_topOptions.py minPT = 75MeV GlobalChi2Fitter maxHoles = 1

Track Quality Cuts

|d0| < 50mm |z0| < 1000mm Pt > 75MeV No. Silicon Hits >= 4 (of 11) No. Pixel Hits >=1 (of 3) No. of holes <=1 Χ2/d.o.f <= 6.0

Primary track: require |d0| < 10mm

Data Selection

Pythia 6.4 @ 14TeV 50k Inelastic non-diffractive 50k Inelastic single and double diffractive

Data passed through ATLAS Geant simulation and digitization Generation of MBTS LVL1 containers

Reconstruction run with low pt tracking settings

Problems

All inelastic non-diffractive jobs crashed 44% of inelastic diffractive jobs crashed

Known problem within tracking software

Reconstructed Tracks: Pt distribution

Reconstructed Tracks: η distribution

Track Quality Cuts: Pt

Track Quality Cuts: η

Track Quality Cuts: Pt vs χ2/d.o.f

Track Quality Cuts: Pt vs Silicon hits

MBTS Trigger Efficiency: Pt

MBTS Trigger Efficiency: η

Conclusions and Outlook

MBTS trigger requirement has no η bias when looking at low pt reconstructed tracks from inelastic diffractive samples.

Better track reconstruction exit condition needed

Need efficiency and purity plots Affect of Ks? Vertex constraint?

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