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• ID Detector News• CSC for Alignment• To Do List• Strategy for a physics analysis start• Miscellanea (computing, future meetings, etc…)

Report from:

Few Words on:

LHC Alignment WorkshopLHC Alignment Workshop

Very interesting meeting, people from different experiments shared experiences:• LHC people focused on strategies and problems• Running experiments reported how they have tackled the problem (CDF was also represented)

Impression was LHC experiments want to achive an unprecedented level of precision.

A lot of discussion about methods and common issues to solve (inv. Matrix, speed, validation, etc)

impact parameter

momentum

ATLAS ID TDRTracking requirements

Degradation due to geometry knowledge: <20% on impact parameter and momentum

Reasonable goal: Pixel: R7 m SCT: R= 12 m TRT: R= 30 m

Furthermore studies of impact of SCT+Pixel random misalignment on B-Tagging abilities show: light jet reduction get worse by 10% for Rm light jet reduction get worse by 30% for R=20m

S. Corréard et al, ATL-COM-PHYS-2003-049

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Initial Misalignment• misalign detector

elements on simulation level

• initial misalignment in the order of 1mm to 30 m has great impact on tracking performance

• misalignment on reconstruction level produces same results

Sergio Gonzalez, Grant GorfineFlorian Bauer, 4/9/2006, LHC Alignment Workshop 12

Software requirements

• ID consists of 1744 Pixel, 4088 SCT and 124 TRT modules

=> 5956 modules x 6 DoF ~ 35.000 DoFs

This implies an inversion of a 35k x 35k matrix

• Use calibration as X-ray and 3Dim measurements to setup

best initial geometry

• combine information of tracks and optical measurements like FSI.

• Reduce weakly determined modes using constraints:

vertex position, track parameters from other tracking detectors, Mass constraints of known resonances, overlap hits, modelling, E/p constraint from calorimeters, known mechanical properties etc.

• ability to provide alignment constants 24h after data taking (Atlas events should be reconstructed within that time)

• And last but not least work under the ATLAS framework: ATHENA

Florian Bauer, 4/9/2006, LHC Alignment Workshop 13

• Global minimisation (the 35k x 35k inversion) • Local minimisation (correlations between modules put to 0,

invert only the sub-matrices, iterative method)

• Robust Alignment (Use overlap residuals for determining relative module to module misalignment, iterative method)

Furthermore work done on:• Runtime alignment system (FSI)

• B-field

Many approaches

Florian Bauer, 4/9/2006, LHC Alignment Workshop 14

“clocking”R(VTX constraint)

“telescope”z~R

radial distortions(various)

dependent sagittaXabRcR2

dependent sagitta“Global twist”Rcot()

global sagittaR

…

We need extra handles in order to tackle these. Candidates:• Requirement of a common vertex for a group of tracks (VTX constraint),• Constraints on track parameters or vertex position (external tracking (TRT, Muons?), calorimetery, resonant mass, etc.)• Cosmic events,• External constraints on alignment parameters (hardware systems, mechanical constraints, etc).[PHYSTAT’05 proceedings] & talk from Tobi Golling

“Weak modes” - examples

Example “lowest modes” in PIX+SCT as reconstructed by the 2 algorithmGlobal Freedom have been ignored

(only one Z slice shown)

The above “weak modes” contribute to the lowest part of the eigen-spectrum. Consequently they dominate the overall error on the alignment parameters. More importantly, these deformations lead directly to biases on physics (systematic effects).

Latest News: We need much more statistics, try to fix the CASTOR problem and run on multiple file. Try to expidite the code, maybe not redoing the pattern recognition every timeDocumentation: We can start to write it down the alignment idea and the results.Either one note (algo, calibration and cosmic) or two notes. Besides that rumors inicate people want a big cosmic ID pubblic note….

Some problem with the infrastructure

• algorithms discussed here use single CPU: can never work in an online environment, because not feasible to process required amount of data in decent amount of time

• need to split algorithms into 1. part that collects data from tracks (i.e. the chisquare

derivatives); perfectly suitable for parallel processing in online reconstruction

2. part that calculate alignment constants and writes those to database; should on a single CPU, for example at the end or a run, or at fixed intervals

Is somebody designing this system for Atlas? If so, is there already a template for calibration algorithms? I’d like to start using it …

… this raised some concern…

Another TRT SW meeting this Thursday to discuss organization and task sharing

Mail from Wouter today about To-Do list

About CSC:About CSC:• Important to start now to convert the code from cosmic setup to collision setup(+MF).• Daniel personally contacted me about it, he really stressed the importance of that• The NPI postdoc is here for two month and he’s willing to help on that and share the burden• Meeting tomorrow with him, Daniel, Wouter, Peter et al…• My feeling is we should fully go on this

On Analysis Start-up strategy:• Give a talk on what we have done in CDF (AIDA) and why we think we can do better in ATLAS• Look for some “external” collaboration. A lot of student/people involved in commissioning looking for physics topics. Little or no “internal” advising, perfect for an “external” mentoring (need some contact).Example: Antony from Melbourne…• Caveat: It is useless give a talk and step forward if we don’t have to follow up in a reasonable time frame(i.e. give a talk and see you in one year….)