What we learned from dc1 b physics validations
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What we learned from DC1 B-physics validations. pp  B (J/ y ( mm ) K 0 ) X. M.Smizanska , Lancaster University for B-physics validation team. DC1 B-physics validation teams:. List of Physics processes. Software tools, status at the start of DC0:. Detector simulation

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What we learned from DC1 B-physics validations

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What we learned from dc1 b physics validations

What we learned from DC1 B-physics validations

pp  B(J/y(mm) K0) X

M.Smizanska, Lancaster University

for B-physics validation team.


What we learned from dc1 b physics validations

DC1 B-physics validation teams:

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

List of Physics processes

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Software tools, status at the start of DC0:

  • Detector simulation

    • ‘TDR’ detector layout was obsolent for several years, but the changes were not implemented in ATLAS software. atlsim 98_2 was identical to 97_6 for the ID description, which corresponded to a description in ID TDR.

    • … so an impact of important changes in the ID: increasing the radius of b-layer, eliminating second pixel layer and some other parts in the endcap - had to be estimated by ATLFAST – using simple approximations of the resolutions derived from TDR ones.

    • Physics performance for conferences was for a long time presented for TDR layout.

    • DC1 validation was important step forward: first publicly presentable B-physics results with new ID layout.

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Software tools, status at the start of DC0, cont

  • ATHENA, Generators

    • TDR B-physics generator Atgenb – a branch of Atgen an ATLAS interface package that stop to be supported in 97.

    • In DC0 – Atgenb – rewritten to PythiaB – ATHENA algorithm, was in use for DC1 production.

  • Reconstruction:

    • atsim, atrecon – longest survivors over TDR-DC0-DC1 … finally were useful for ATHENA validations – most of our DC1 done in parallel using atrecon (or atlsim!) and ATHENA

    • ATHENA-reconstruction much progress during DC1 …

    • … but we did not reach the same performance for the 3 packages in DC1. The sources of differences are more-less understood, but all these packages stop at DC1. All manpower - to DC2.

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Detector Layouts in DC1 validations

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Software in DC1 validations

*) part of Complete and Initial also with iPatrec, 6.0.3

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Performance results

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Mass reconstruction

Core of mass distributions similar with

Complete and Initial layouts and Complete-300mm.

Degradation vrt TDR: 10-15%

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Complete vs Initial layout: reconstruction of B-signal mass

xKalman6.5.0 optimized track finding strategy

Example for channel BsJ/y(m6m3)f(K+K-)

All four tracks of B reconstructed

e = 82.5% (5% B in tails)

e =77.9% (6% B in tails)

… and B-vertex reconstructed

e = 82.3% (5% B in tails)

e = 77.7% (6% B in tails)

Initial Layout:

1. Efficiency to reconstruct B only 4.5% smaller then in Complete.

2. Only 0.3 % fails the vertex fit in both Complete and Initial layouts.

Complete Layout

Initial Layout

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

All four tracks of B reconstructed

e = 83% (4% B in tails)

e =77% (11% B in tails)

… and B-vertex reconstructed

e = 82% (4% B in tails)

e = 67% (8% B in tails)

…the same events withdefault xKalman track search strategy

– failed for Initial layout, ok for Complete layout.

Example for channel BsJ/y(m6m3)f(K+K-)

Initial Layout:

1. More B’s in tails.

2. Efficiency to reconstruct B tracks only 6% smaller,

3. however next 10% fails the vertex fit

Complete Layout

Initial Layout

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

B-hadrons - proper time resolution

Core of proper-time distribution similar in Complete and Initial layouts.

Degradation vrt TDR: 20-35%.

Degradation Complete 400mm vrt 300mm : 14%

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

B-hadrons proper-time resolution, optimized xKalman

Example for channel BsJ/y(m6m3)f(K+K-)

Both Complete and Initial layout similar: Bs proper-time reconstruction:

8% in tails

only 0.3% fails vertex fit

in both layouts

Complete Layout

Initial Layout

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

All four tracks of B reconstructed and B-vertex reconstructed

e = 82% (7% B in tails)

e = 67% (16% B in tails)

B-hadrons proper-time resolution, default xKalman

Example for channel BsJ/y(m6m3)f(K+K-)

Bs proper-time resolution:

1. Complete layout 7% in tails

2. Initial layout 16% in tails

… and lower efficiency of track reconstruction and less sucessful vertex fits

-> all these factors lead to decrease of efficiency. After final selection cuts in this channel

Initial : Complete 3:5

Complete Layout

Initial Layout

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Efficiency of reconstruction of B-signal including vertex fit Initial vs Complete, optimal xKalman

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

  • Complete layout vrt Initial layout similar performance.

  • … so are we going to miss second pixel layer?

  • The simulation was optimistic

  • inefficiencies underestimated

  • no misalignement

  • degradation appears at higher multiplicities - already at L=2 x 1033 cm-2 s-1

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Single-track performance:

wrong hit on track in b-layer; dependence on: layout, multiplicity and pT.

Complete layout vrt Initial similar - if only a signal event simulated.

Degradation at higher multiplicities (already at L=2 x 1033 cm-2 s-1 ).

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Athena7.0.0 versus atrecon… different performance

ATHENA worse by  ~10% than atrecon6.5.0

atrecon 'private'  ~8% worse than atrecon6.5.0.

Degradation due to pixel clusters errors.

Other -smaller factor:  ATHENA

more inefficiencies  

Can ATHENA7.0.x be corrected ?? 

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Athena7.0.0 versus atrecon… different performance

  • We finish DC1 with ATHENA reconstruction in which we are aware of errors

  • Degraded performance in proper-time vrt atrecon.

  • Can ATHENA 7.0.x be improved?? NO

    • cannot invest time for old code – need people for 7.3.0…

    • DC1 Simulation not realistic anyway, for instance misalignment…

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Conclusions

  • Initial vrt Complete layout - similar performance – if no pileup, with optimized track search strategy in atrecon6.5.0.

    • Track-finding efficiency -7% for pt (0.5-1.0) GeV, only -2%. for pT>1GeV

    • Tracks with wrong hit in B-layer: Initial 3%, in Complete 2% for pT<1GeV

    • Efficiency of B-signal reconstruction Initial vrt Complete: lower by ~6% - due to track search inefficiency. Only 0.3% fails vertex fit in both Initial and Complete layouts.

  • Comparisons with other layouts

    • Mass resolution: degraded 10-15% vrt TDR,

    • Time resolution: degraded 20-30% vrt TDR, and 14% 400mm vrt 300mm.

  • Still to be done in DC1: Signal events with minimum bias.

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


What we learned from dc1 b physics validations

Conclusions,cont

  • We are aware of insufficiencies of DC1 and we understand their impact on performance.

  • This will alllow us to use reasonably the DC1 software validation results as a starting point to validate DC2 software.

M.Smizanska, et al, DC1 B-validation, UK-physics meeting


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