[PPT] - The performance of the ATLAS Initial detector layout for B-physics PowerPoint Presentation

SLIDE 1

The performance of the ATLAS Initial detector layout for B-physics channels

B. Epp, V.M. Ghete, D. Kuhn, Y.J. Zhang

Institute for Experimental Physics University of Innsbruck, Austria ¨ OPG FAKT, Weyer, September 2004

SLIDE 2

Introduction Purpose of this studies:

Inner Detector(ID) performance w.r.t. quantities relevant to

B0

s → Dsπ analysis (Ds → φπ, φ → K+K−)

Validation of software in the ATLAS framework ATHENA
Validation of generation-simulation-reconstruction-analysis chain for:

– Initial layout – Complete layout Various comparisons were performed:

one-step comparisons: change one step in the software chain

and perform – comparison of different layouts – comparison of different versions of the reconstruction software

multi-step comparisons: more steps were different
V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 3

ATLAS Full Detector Inner Detector Electromagnetic and Hadronic Calorimeters Muon Detectors

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 4

ATLAS Inner Detector ID Inner Detector (ID):

cylinder with barrel and end-

cap parts

discrete semiconductor pixel

and strip detectors

transition radiation tracker:

straw-tubes interspersed with a radiator = ⇒ e/π separation

inside solenoid: 2 T magn.

field Staged detector: = ⇒ Initial layout versus Complete Layout

Detector part barrel end-cap Initial / Complete cylinders disks on each side Pixel Detectors 2 / 3 2 / 3 Semi-Conductor Tracker (SCT) 4 / 4 9 / 9 Transition Radiation Tracker (TRT) axial tubes C-Wheels: no/yes

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 5

Software chain Software step Software release Event generator Pythia 6.205, with B-physics tuning 50k events Athena framework, software release 5.0.0 Detector simulation full detector: initial layout complete layout atlsim framework, software release 6.0.2 (via AFS) realistic, non-uniform magnetic field Pileup simulation atlsim framework, software release 7.0.2

∼ L=2 × 1033cm−2s−1

min bias events with muon safety factor = 1 Reconstruction package xKalman++ with non-uniform magnetic field atrecon framework, software release 6.6.0 Athena, software release release 7.0.0 Analysis Combined Ntuples CTVMFT vertex fit package (uniform magnetic field)

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 6

Definitions of quantities

φ, Ds, B0

s mass resolutions and peak positions:

= ⇒ Fit core with a Gaussian function

B0

s dxy transverse decay length:

distance between interaction point and reconstructed B0

s decay vertex

projected onto the transverse plane = ⇒ Fit sum of two Gaussian functions, same mean value

B0

s g-factor fractional resolution: (g − g0)/g0

g = MB0

s/

c · pB0

s

T

,

g0 = MB0

s/

c · pT

B0

s

true

=

⇒ Fit with a Gaussian function

B0

s proper time: t = dxyg

proper time resolution t − t0 = ⇒ Fit sum of two Gaussian functions, same mean value Fits with sum of two Gaussian functions: For comparison, force for second sample the ratio from the first sample.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 7

Initial vs Complete layout: Atrecon rec., no pile-up

Particle Characteristic Initial layout Complete layout Nominal mass (MeV) 1019.4 1019.4 φ Peak position (MeV) 1019.6 ± 0.0 1019.6 ± 0.0 Resolution (MeV) 3.8 ± 0.0 3.8 ± 0.0 Nominal mass (MeV) 1968.5 1968.5 Ds Peak position (MeV) 1969.9 ± 0.1 1969.3 ± 0.1 Resolution (MeV) 15.4 ± 0.1 15.6 ± 0.1 Nominal mass (MeV) 5369.3 5369.3 B0

s

Peak position (MeV) 5369.3 ± 0.7 5367.4 ± 0.7 Resolution (MeV) 46.0 ± 0.6 46.4 ± 0.6

100 200 300 400 5.2 5.4 5.6 Entries / 0.01 GeV MKKππ [GeV] Initial Complete

No deterioration of the mass resolutions for the Initial layout w.r.t. Complete layout is seen.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 8

Initial vs Complete layout: Atrecon rec., no pile-up

Distribution Characteristic Initial layout Complete layout Peak position (µm) −0.8 ± 1.5 1.5 ± 1.4 Fraction G1 (%) 72.4 ± 2.2 idem dxy − d0

xy

Fraction G2 (%) 27.6 ± 2.2 idem Resolution G1 (µm) 84.3 ± 2.4 86.4 ± 1.5 Resolution G2 (µm) 212.7 ± 9.1 195.9 ± 4.1 Peak position (fs) −1.0 ± 1.3 0.4 ± 1.3 Fraction G1 (%) 63.1 ± 3.7 idem t − t0 Fraction G2 (%) 36.9 ± 3.7 idem Resolution G1 (fs) 69.8 ± 3.2 73.2 ± 1.4 Resolution G2 (fs) 157.5 ± 9.4 153.1 ± 2.9

100 200 300 400

0.4
0.2

0.2 0.4 Entries / 0.02 ps t-t0 [ps] Initial Complete

A slight tendency toward broader cores for Complete (more dead material) and larger tails for Initial (missing pixel layer) layout can be seen.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 9

Initial vs Complete layout: Atrecon rec., no pile-up

B0

s → Dsπ

Initial layout Complete layout Initial/Complete Simulated events 50000 50000 Reconstructed events σ = 46.0 MeV σ = 46.4 MeV 3σ 5901 6269 2σ 5542 5865 1σ 4016 4270 Reconstructed events / 10 fb−1 3σ 3324 3547 93.7% 2σ 3122 3304 94.5% 1σ 2262 2405 94.1%

6% of events are lost for the Initial layout w.r.t. the Complete layout. Differences are due to the track reconstruction. Overall: no significant deterioration of quantities for Initial layout w.r.t Complete layout.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 10

Initial layout: Atrecon versus Athena rec., no pile-up B-physics conditions require a non-default tracking strategy for xKalman pattern recognition:

typical B-decay tracks at low pT
missing second pixel layer in Initial layout =

⇒ pattern recognition fails or finds track with wrong hit in b-layer Parameter settings for alternate xKalman tracking strategy:

silicon clusters per track ≥ 7
no cut on hits in pixel layers (including b-layer)
minimum number of no-shared hits per track = 4
selectivity of reconstruction = 4
minimum number of TRT clusters per track = 9
maximum number of holes = 22
V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 11

Initial layout: Atrecon versus Athena rec., no pile-up

Distribution Characteristic Atrecon Athena Peak position (µm) −0.8 ± 1.5 −2.1 ± 1.6 Fraction G1 (%) 72.4 ± 2.2 idem dxy − d0

xy

Fraction G2 (%) 27.6 ± 2.2 idem Resolution G1 (µm) 84.3 ± 2.4 92.4 ± 1.6 Resolution G2 (µm) 212.7 ± 9.1 228.6 ± 4.7 (g − g0)/g0 Peak pos. (%) 0.007 ± 0.011 −0.013 ± 0.010 Resolution (%) 0.80 ± 0.01 0.81 ± 0.01 Peak position (fs) −1.0 ± 1.3 −1.3 ± 1.4 Fraction G1 (%) 63.1 ± 3.7 idem t − t0 Fraction G2 (%) 36.9 ± 3.7 idem Resolution G1 (fs) 69.8 ± 3.2 76.6 ± 1.4 Resolution G2 (fs) 157.5 ± 9.4 174.4 ± 3.3

Relatively large difference in dxy and proper time t resolutions: = ⇒ Athena worse by ∼ 10% than Atrecon. Explanation after cross check using Athena software inside Atrecon: predominantly due to different way of computing errors associated to pixel cluster position (simplified error calculation used in Athena)

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 12

Initial layout: Atrecon versus Athena rec., no pile-up

B0

s → Dsπ

Atrecon Athena Atrecon/Athena Simulated events 50000 50000 Reconstructed events σ = 46.1 MeV σ = 46.4 MeV 3σ 5901 6459 2σ 5542 6038 1σ 4016 4386 Reconstructed events / 10 fb−1 3σ 3324 3639 91.3% 2σ 3122 3401 91.8% 1σ 2262 2471 91.5%

100 200 300 400

0.4
0.2

0.2 0.4 Entries / 0.02 ps t-t0 [ps] Atrecon rec. Athena rec.

9% less events in Atrecon, due to different way

f computing errors on the track parameters in

Athena and Atrecon.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 13

Initial layout - pile-up versus no pile-up All samples were reconstructed with Athena only. An influence of pile-up on individual track reconstruction is seen for the Λ0

b → J/ψ (µ+µ−)Λ0(pπ−) channel:

the fraction of reconstructed tracks with an incorrect hit in b-layer is increasing (especially in the low pT region).

Λ0

b: σ single Gauss fit

no pile-up pile-up pile-up/no pile-up mass (MeV) 26.9 ± 0.6 28.4 ± 0.8 105.6% proper-time (fs) 108.1 ± 2.2 115.2 ± 2.6 106.6% N pile

rec / N nopile rec

94.0%

Broader resolutions and degradation of efficiency of ∼ 6% for pile-up events. (Λ fails to match J/ψ vertex) Similar effects are not seen on B0

s mass, dxy or t -resolutions or number of

reconstructed events for B0

s pile-up events (possible explanation: secondary

particles decay before b-layer).

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 14

Pile-up effect: Initial versus Complete layout

B0

s mass resolutions

100 200 300 400 5.2 5.4 5.6 Entries / 0.01 GeV MKKππ [GeV] Initial Complete

B0

s proper-time resolutions

100 200 300 400

0.4
0.2

0.2 0.4 Entries / 0.02 ps t-t0 [ps] Initial Complete

The same tendencies are observed as for no pile-up samples (no pile-up effect):

No deterioration of the mass resolutions
Tendency to slightly broader cores for dxy or t resolutions for Complete layout

(more dead material)

Same number of events (∼ 6%) is lost for the Initial layout w.r.t. the

Complete layout (due to the track reconstruction)

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 15

Conclusions For the actual set of cuts and assuming no additional dead cell and misalignment in the Inner Detector:

The performance of the detector is not deteriorated significantly for the Initial

layout w.r.t. the Complete layout.

The pile-up added for the events can have some influence on the detector

performance depending on the topology of the B-physics event within a few percent

Due to simplifications in some of the DC1 tools software had to be evolved

and adapted to fulfill needs of B-Physics analysis

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 16

Tasks Tasks to increase precision and reliability of further performance studies (DC2 period):

include misalignment
provide realistic detector efficiencies and noise
provide more realistic pixel cluster errors
availability of combined muon reconstruction
vertexing should use realistic magnetic field
V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 17

Backup

BACKUP

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 18

Initial layout: pile-up effect

Particle Characteristic Events with pile-up Events w/o pile-up Nominal mass (MeV) 1019.4 1019.4 φ Peak position (MeV) 1019.6 ± 0.0 1019.6 ± 0.0 Resolution (MeV) 3.9 ± 0.0 3.9 ± 0.0 Nominal mass (MeV) 1968.5 1968.5 Ds Peak position (MeV) 1970.0 ± 0.1 1970.0 ± 0.1 Resolution (MeV) 15.8 ± 0.1 15.8 ± 0.1 Nominal mass (MeV) 5369.3 5369.3 B0

s

Peak position (MeV) 5369.7 ± 0.6 5370.7 ± 0.6 Resolution (MeV) 46.0 ± 0.6 46.3 ± 0.6

No deterioration of the mass resolutions for the initial layout due to pile-up.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 19

Initial layout: pile-up effect

Distribution Characteristic Events with pile-up Events w/o pile-up Peak position (µm) −1.0 ± 1.5 −2.1 ± 1.6 Fraction G1 (%) 72.8 ± 2.3 idem dxy − d0

xy

Fraction G2 (%) 27.2 ± 2.3 idem Resolution G1 (µm) 91.4 ± 2.7 92.7 ± 1.6 Resolution G2 (µm) 228.7 ± 11.0 229.8 ± 4.7 (g − g0)/g0 Peak pos. (%) 0.000 ± 0.010 −0.013 ± 0.010 Resolution (%) 0.80 ± 0.01 0.81 ± 0.01 Peak position (fs) −1.4 ± 1.4 −1.2 ± 1.4 Fraction G1 (%) 57.5 ± 3.4 idem t − t0 Fraction G2 (%) 42.5 ± 3.4 idem Resolution G1 (fs) 74.9 ± 3.3 72.8 ± 1.6 Resolution G2 (fs) 158.0 ± 6.3 166.1 ± 2.9

No significant effect of pile-up on dxy or t resolutions.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 20

Initial layout: pile-up effect

B0

s → Dsπ

With pile-up W/o pile-up Pile-up/No pile-up Simulated events 50000 50000 Reconstructed events σ = 46.1 MeV σ = 46.4 MeV 3σ 6401 6459 2σ 5964 6038 1σ 4328 4386 Reconstructed events / 10 fb−1 3σ 3606 3639 99.1% 2σ 3360 3401 98.8% 1σ 2438 2471 98.7%

No significant effect of pile-up on the number of reconstructed events.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 21

Initial versus complete layout: pile-up effect

Particle Characteristic Initial Complete Nominal mass (MeV) 1019.4 1019.4 φ Peak position (MeV) 1019.6 ± 0.0 1019.6 ± 0.0 Resolution (MeV) 3.9 ± 0.0 3.9 ± 0.0 Nominal mass (MeV) 1968.5 1968.5 Ds Peak position (MeV) 1970.0 ± 0.1 1969.5 ± 0.1 Resolution (MeV) 15.8 ± 0.1 16.0 ± 0.1 Nominal mass (MeV) 5369.3 5369.3 B0

s

Peak position (MeV) 5369.7 ± 0.6 5368.5 ± 0.6 Resolution (MeV) 46.0 ± 0.6 46.4 ± 0.6

No deterioration of the mass resolutions for the initial layout w.r.t. complete layout is seen for events with pile-up reconstructed with Athena.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 22

Initial versus complete layout: pile-up effect

Distribution Characteristic Initial Complete Peak position (µm) −1.0 ± 1.5 1.6 ± 1.6 Fraction G1 (%) 72.8 ± 2.3 idem dxy − d0

xy

Fraction G2 (%) 27.2 ± 2.3 idem Resolution G1 (µm) 91.4 ± 2.7 97.1 ± 1.6 Resolution G2 (µm) 228.7 ± 11.0 229.8 ± 4.7 (g − g0)/g0 Peak pos. (%) 0.000 ± 0.010 0.030 ± 0.010 Resolution (%) 0.80 ± 0.01 0.79 ± 0.01 Peak position (fs) −1.4 ± 1.4 1.2 ± 1.4 Fraction G1 (%) 57.5 ± 3.4 idem t − t0 Fraction G2 (%) 42.5 ± 3.4 idem Resolution G1 (fs) 74.9 ± 3.3 77.4 ± 1.7 Resolution G2 (fs) 158.0 ± 6.3 162.4 ± 2.5

Tendency: slightly broader cores for complete layout (more dead material).

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004

SLIDE 23

Initial versus complete layout: pile-up effect

B0

s → Dsπ

Initial Complete Initial/Complete Simulated events 50000 50000 Reconstructed events σ = 46.1 MeV σ = 46.4 MeV 3σ 6401 6881 2σ 5964 6389 1σ 4328 4650 Reconstructed events / 10 fb−1 3σ 3606 3876 93.0% 2σ 3360 3599 93.4% 1σ 2438 2616 93.2%

Same number of events are lost for the initial layout w.r.t. the complete layout as in the case of samples without pile-up. Differences are due to the track reconstruction.

V. B. Epp

ATLAS initial detector layout performance ¨ OPG FAKT, Sept 2004