1

Muon Alignment: Muon Alignment: OrganizationOrganization• Organization

– New co-coordinator: Jim Pivarski (to be formalized at MUIB)– The sign-off chain is formalized, but long: we'll need to have a

common decision on a muon geometry within the group a few weeks in advance of the CMS-wide sign-off

MUIB

2

Muon Alignment: StrategyMuon Alignment: Strategy• “Quasi-static” alignment state

– Even when a requested sign-off date is announced in advance, slippage can make the actual date uncertain– To avoid being caught without an agreed-upon geometry, will aim to always have a “state-of-the-art" at hand– The discrepancies/problems that we're working on are usually

motivated by the results of validation anyway: having a validated working point formalizes that (and can help assess priorities)

• Documentation!– So far largely underused muon alignment Twiki– Aim to document results, validations, tools periodically– Keep documentation updated with respect to “state-of-the-art”

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Muon Alignment (quick) Muon Alignment (quick) StatusStatus

Passive plane (12)

Active plane (12)

Muon chamberoptical line(8 lines)

Link line

MAB (36 pieces)

Z bar

Diagonal connection

• Full barrel alignment• All DTs aligned simultaneously using optical (barrel+link) system• Good agreement of TK-MU relation between HW and tracks• Decent agreement between track-based and HW constants

• discrepancies under study• First combined HW+track-based alignments• Validated by PVT

• Improved internal DT alignment• Includes theta superlayer• Includes all corner-block-to-wires and quality control measurements

CB

• CSC alignment• New beam-halo + photogrammetry alignment• New optical alignment in r- coordinates• Combined Endcap + Link information• Next step: integration of optical + track-based alignments

4

Unexpected dependence of residuals on position within the chamber (“sawtooth effect”) and on track curvature are now both explained:

Due to a typo, RPC hits were allowed to bias tracker-to-muon propagation

With this corrected, many long-standing mysteries have been resolved

Consequences: Can lower pT > 100 GeV/c cut used in alignment

(see next slide) Must revise resolution vs. integrated luminosity

estimates (“5-20 pb-1 for 200 microns” derived from affected code, likely to be too optimistic)

Track-Based Alignment Track-Based Alignment Status IStatus I

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Track-Based Alignment Track-Based Alignment Status IIStatus II

Residuals are now wider but mean is independent of Pt:can align without high Pt cut

6

Removing the RPC-hit bias

Both of these effects had the same cause

All barrel residuals distributions now behave ~ as expected; new alignment produced

Track-Based Alignment IIITrack-Based Alignment III

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Chamber-to-chamber agreement at the level of 1.3mm

Outliers in these TB-HW r difference plots are low-statistics chambers

Largest remaining discrepancy: trend vs. wheel in local-x

Independent of RPC-hit bias

• Simple twist model already ruled out by Link and Global and SA track constrains

• Other possibilities under study

Muon Alignment: HW vs Muon Alignment: HW vs TracksTracks

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Track-based analysis: Confirmed at the level of raw residuals: no sharp

breaks at chamber boundaries indicates either a track bias or a coherent rotation of the superplanes

Not proportional to station number, as would be expected of rotated tracks (effect is clearly constant with respect to station number)

Hardware analysis: End-to-end difference measured by link: 1.1 +- 0.6

mm, not 4 mm as it appears from tracks Inclinometers and transfer lines can provide

additional independent cross-checks Using independence of the TB/HW datasets

to find remaining problems and converge upon a solution

Muon Alignment: ongoing Muon Alignment: ongoing studiesstudies

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Alignment Constants Time-Alignment Constants Time-lineline

2/7

9/7

16/7

23/7

30/7

6/8

13/8

20/8

27/8

3/9

Lin

k

AR

vs. TK

Barrel

En

dcap

X

,Y

ME

2,3,4

Integrated HW + track-based Geom

DT

tracksC

osm

ics, pp

CS

C tracks

BH

, cosm

ics, p

p

Agree on common HW runs @ 3.8T

En

dcap

Z,

x

??

?

En

dcap

T.L

. ?

??

Integrated HW Geom @ 3.8T

Validated HW alignment Validated track alignment

Validated Muon Alignment Geometry

New alignment constants due ~ here ?

Tools for

HW

Autom

ation

CS

C

HW

+B

.H.

com

bin

ation

stud

ies

Op

timize

HW

+T

rac

k C

om

bin

atio

n

Enter “quasi-static” loop (with faster turn-around)