1. Tracking performances & b-tagging commissioning
Simone Montesano (Milano)

2. Simone Montesano - Milano
Outline
Motivation:
Impact of b-tagging on ATLAS data analysis (top cross section)
Plan for 2009 (PHD thesis)
Pixels offline calibrations => effect on resolution
Tracking performances using cosmics data
Tracking performances from first collisions data (minimum bias events)
Developments & perspectives (2010)
Tracking performances from first collisions data (top events)
b-tagging commissioning using ttbar events (see CSC note)
Real data
MC data
3 June 2018
Simone Montesano - Milano

3. Top cross section analysis - b-tagging impact -
B-tagging is an important tool in ATLAS:
From CSC note “Determination of Top Quark Pair Production Cross-Section” (Udine involved):
100 pb-1 data, 14 Tev
STANDARD ANALYSIS: no b-tagging (S/B = 2.2. – 5.3)
b-tagging (S/B = 9.6 – 20.1)
B-tagging performances are tested for small misalignments:
From CSC note “Effect of Misalignment on b-Tagging”:
“The amount of misalignment remaining after applying the actual alignment procedures resulted in only a small loss of performances[..]”
CSC analysis didn’t assumed a working b-tagging with first data (no time for full alignment and tracking commissioning before collisions)
3 June 2018
Simone Montesano - Milano

4. b-tagging status after commissioning with cosmics?
Before reprocessing: impact parameter resolution
Splitted tracks to estimate resolution on tracking parameters
d0 resolution is already very near to the nominal one!
12 μm expected!!!
3 June 2018
Simone Montesano - Milano

5. Optimizing pixel resolution: offline calibrations
This is done with preliminary alignment!
30 um improvement in eta direction!
3 June 2018
Simone Montesano - Milano

6. Simone Montesano - Milano
Plans: before data
Consider SIG/BKG ratio in the plane “b-tagging efficiency vs b-tagging rejection” (top cross section analysis):
when b-tagging starts to be useful?
requirements on tracking performances?
where b-tagging algorithms curves are placed?
Plans: First data
Tracking performances using minimum bias:
resolution, efficiency?
is b-tagging ready?
impact on data?
3 June 2018
Simone Montesano - Milano

7. b-tagging commissioning using ttbar events
Work that could start on simulated data and be completed in 2010 using data
“super pure” top events selection
mainly interested in b-jet enriched sample
no need to reconstruct the full event
di-leptonic top events?
3 June 2018
Simone Montesano - Milano