1. Muon Alignment: 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: 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”

3. Muon Alignment (quick) Status
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 f q f
CSC alignment
New beam-halo + photogrammetry alignment
New optical alignment in r-f coordinates
Combined Endcap + Link information
Next step: integration of optical + track-based
alignments

4. Track-Based Alignment Status I
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)

5. Track-Based Alignment Status II
Residuals are now wider but mean is independent of Pt:
can align without high Pt cut

6. Removing the RPC-hit bias
Track-Based Alignment III
Removing the RPC-hit bias
Both of these effects had the same cause
All barrel residuals distributions now behave ~ as expected; new alignment produced

7. Muon Alignment: HW vs Tracks
Chamber-to-chamber agreement at the level of 1.3mm
Outliers in these TB-HW rf 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

8. Muon Alignment: ongoing studies
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: 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

9. Alignment Constants Time-line
Agree on common HW 3.8T
2/7
9/7
16/7
23/7
30/7
6/8
13/8
20/8
27/8
3/9
BH, cosmics, pp
CSC tracks
CSC HW+B.H.
combination
studies
HW Automation
Tools for
Endcap X,Y ME2,3,4
Barrel
Cosmics, pp
DT tracks
Link
AR vs. TK
Endcap Z, fx
???
Endcap T.L.
???
Integrated HW 3.8T
Optimize HW+Track
Combination
Validated HW alignment
Validated track alignment
Integrated HW + track-based Geom
Validated Muon Alignment Geometry
Enter “quasi-static” loop (with faster turn-around)
New alignment constants due ~ here ? 9