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Muon Alignment: Organization. MUIB. 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.

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slide1

Muon Alignment: Organization

MUIB

  • 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
slide2

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”
slide3

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
slide4

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)
slide5

Track-Based Alignment Status II

Residuals are now wider but mean is independent of Pt:

can align without high Pt cut

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
slide7

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
slide8

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: 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
slide9

Alignment Constants Time-line

2/7

9/7

16/7

23/7

30/7

6/8

13/8

20/8

27/8

3/9

Agree on common HW runs @ 3.8T

CSC HW+B.H.

combination

studies

CSC tracks

BH, cosmics, pp

Tools for

HW Automation

Endcap X,Y ME2,3,4

DT tracks

Cosmics, pp

Barrel

Link

AR vs. TK

Endcap Z, fx

???

Endcap T.L.

???

Optimize HW+Track

Combination

Integrated HW Geom @ 3.8T

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 ?