Muon Barrel Geometry Studies

Luca ScodellaroMuon Barrel Workshop

July 6th, 2010

OutlineStudies of the latest hardware-based

barrel geometryStudies for a standalone barrel

geometry with tracksInclusion of quality control

measurements

Studies of Latest HW GeometryLatest barrel geometry sign-off at the

PVT meeting on May 12th and used for ICHEP

Use DT segments to study relative alignment of neighbour chambers in the same sector

Use new track collection with t0 correction from May 24th reprocessing

> bottom-top asymmetryLook for systematic effects

Bottom-Top AsymmetryComparison of residual distributions

Top

Bottom

Old collectionNew collection

Performance of HW GeometryMeans of ∆X distributions

Performance of HW GeometryMeans of ∆dX/dY distributions

Performance of HW GeometryMeans of ∆Y distributions

Performance of HW GeometryMeans of ∆dY/dZ distributions

Bottom-Top Comparison

(mrad)

(mrad)

Mean distributions for hemisphere Bottom sectorsTop sectors

Comparison by Station

(mrad)

(mrad)

Mean distributions for station Station 1 to 2Station 2 to 3Station 3 to 4

Wheel to Wheel Twist Select tracks crossing two wheelsUse DT segments connecting neighbour chambers: (final station-initial station)=±1 (final wheel-initial wheel)=±1Assumeing YB0 as a reference and

extrapolating DT segments towards external wheels:

no significant twist of wheels observed

Wheel to Wheel TwistGlobal results

W-2 vs W-1 W-1 vs W0

W1 vs W0 W2 vs W1

Wheel to Wheel TwistStation by station results

Station 1 to station 2

Station 2 to station 3

Station 3 to station 4

Standalone Geometry with TracksHardware alignment close to its design

precisionAlignment with respect to the tracker might

suffer for several effects > track misalignment, B field, material

descriptionWe want to improve our standalone

description of the barrel using tracksMillepede approach based on a linear

approximation of residuals: R = B∆p + AδB matrix hard to describe in a non-uniform

magnetic field

Trying an approach based on DT segment

> for small movements, we can assume ∆p to depend only on chamber movements B ∆p = ACδinit = Aδfinal

> simplified χ2 minimization Using half statistic to fit chamber

movements inside a sector, the other half to test the new geometry with the usual method (tighter cuts)

Standalone Geometry with Tracks

Residual DistributionsYB0, Sector 11, Station 2

(mrad)

Corrected distributionUncorrected distribution

Mean Distributions

(mrad)

(mrad)

Corrected geometryUncorrected geometry

Quality Control MeasurementCorrection distribution

Segment Validation

(mrad)

(mrad)

ConclusionsWe studies the performances of the

latest hardware-based barrel geometry

> still some top-bottom asymmetry observed

> no major systematic so far identified with segments

Quality control measurement added to internal chamber description

Starting to develop a standalone track-based geometry