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Misalignment studies MS z misalignments Barrel and Endcap

Misalignment studies MS z misalignments Barrel and Endcap. Peter Kluit, Muon week meeting 15 November Summary of results 5/15 october. Based on the v35 processing of the Z skimmed data. Focussing on MS misalignments. Study was initiated by so-called Afb effect

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Misalignment studies MS z misalignments Barrel and Endcap

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  1. Misalignment studiesMS z misalignments Barrel and Endcap Peter Kluit, Muon week meeting 15 November Summary of results 5/15 october Based on the v35 processing of the Z skimmed data

  2. Focussing on MS misalignments • Study was initiated by so-called Afb effect • CB momentum suffered from systematic eta dependent effects • Traced down to misalignment in z of MS and ID • Here below it is pinned down to misalignments in the Muon system • Using muons from Z events in ZMUMU v35 (release 17) processing. • Will be done in three ways: • Comparison of MS-MS parameters: z0-z0 • B) Comparison of MS-ID z0 parameter • Z0 of ID is consistent and precise to better than 0.1 mm apart from ONE global z shift • C) comparing theta ID and SA • Try to understand and model the Endcap structure: Barrel is more simple.

  3. Looking at z0 SA – z0 SAfor MS Barrel-Barrel events Select eta1<0 and eta2 >0 events and plot plot dz = z(eta>0) – z(eta<0) So Barrel A and C are not consistent at 2 mm level

  4. z0 SA – z0 SAfor MS Barrel-Endcap events plot dz = z(EC) – z(Barrel) both in eta >0 or both in <0 So Barrel and Endcap are not consistent at a few mm level - It is known that B-E overlap are not consistent - See also slide 9 that demonstrate this wrt z0 of ID

  5. Looking at z0 SA – z0 SAA simplified model for the Endcap R (sign) Inspired by the linear trend in slide 4 CSC region might be more complicated z • A possible deformation would look like this • Keeps the z distance between A-C approx. constant • not only a z shift of endcap A or C: can be added • has feature that dz vs eta is linear for Endcap AA or CC events • Can be tested and refined selecting Endcap-Endcap events: • - Events A-C (z distance between AC) and AA or CC events

  6. Looking at z0 SA – z0 SAMS Endcap A-C Recall slide MCP Plotted eta in EC A Means that EC distance is correct at ~2 mm level

  7. z0 SA – z0 SAMS Endcap AA Plotted delta eta of the two muons in EC A So: dz/deta = -6 mm/ unit rapidity By ‘definition’ through 0 Or 9 mm/1.5 rap Quite unexpected…

  8. z0 SA – z0 SAMS Endcap CC Plotted delta eta of the two muons in EC A So: dz/deta = -4.4 mm/ unit rapidity By ‘definition’ through 0 Or 6.6 mm/1.5 rap Quite unexpected… A and C seem to behave similarly

  9. A telescope model for the Endcap • Basically the same as the one on slide 5 • There are however NO z(R) shifts • There are rotations + small shifts (~1 mm). theta’ = theta + dtheta This generates a z0’: z0’ = z0 +/- 7000*dtheta/sin2(theta) Value of dtheta = 30 μrad (A side) and 50 μrad (C) This value is compatible with Survey and alignment constraints Interpretation: telescope effect in Endcap i.e. small rotations (dR/dz) that are phi sector dependent This is consistent with the observed sector dependence

  10. z0 ID – z0 SA at primary vertex before/after correction for dtheta Tighted MS track selection to three station tracks with NO EE chambers and NO Barrel-Endcap Flattened: After Before

  11. z0 SA – z0 SA correctedMS Endcap AA Plotted delta eta of the two muons in EC A Now flat!

  12. z0 SA – z0 SA correctedMS Endcap CC Plotted delta eta of the two muons in EC C Now flat!

  13. z0 SA – z0 SA correctedMS Endcap A-C Plotted eta in EC A Means that EC distance is correct at ~2 mm level After correction results more compatible with 0 Conclusion: Model in slide 9 seems to do the job

  14. z0 ID –z0 SA correctedEndcap: eta Sector projections Interpretation: dtheta is sector dependent and small misalignments cause q splitting

  15. z0 ID –z0 SA correctedEndcap: eta Sector projections

  16. z0 ID –z0 SABarrel: eta Sector projections Different interpretation for the Barrel: Here we have z shifts that are sector dependent The charge splitting could be due to misalignment in position and/or angle

  17. z0 ID –z0 SABarrel: eta Sector projections

  18. Endcap: q* (z0 ID –z0 SA) and q*(theta ID- theta SA) corrected Very similar shapes in dz and dtheta plots: implies that structure comes from dtheta MS endcap misalignments: in agreement with the model

  19. Endcap: q* (z0 ID –z0 SA) and q*(theta ID- theta SA) corrected Very similar shapes in dz and dtheta plots: implies that structure comes from dtheta MS endcap misalignments: in agreement with the model

  20. Barrel: q* (z0 ID –z0 SA) and q*(theta ID- theta SA) corrected Very similar shapes in dz and dtheta plots: implies that structure comes from MS Barrel z/theta misalignments.

  21. Barrel: q* (z0 ID –z0 SA) and q*(theta ID- theta SA) corrected Very similar shapes in dz and dtheta plots: implies that structure comes from MS Barrel z/theta misalignments.

  22. Conclusions • - An Interpretation for the Endcap is proposed: telescope effect in Endcap i.e. small rotations (dR/dz) that are phi sector dependent. Plus small shifts of the Endcap (~1 mm). • Correcting for the Endcap Model gives dtheta values of 30 and 50 microrad • These values are in agreement with constraints from Survey and the optical alignment. • The distributions in Endcap A and C are after correction flat • Detailed study of the sector dependent effects show that: • Endcap dtheta correction is sector dependent • Endcap q*misalignments in MS are observed in z0 and theta (wrt ID) -> misalignment within one sector • Everything compatible with dtheta << 50 microrad

  23. Conclusions • - The results in the Barrel can be interpreted as a set of sector dependent z shifts • This is in agreement with constraints from Survey and the optical alignment. • Looking into more detail at q*dz and q*dtheta (appended) plots structures are observed indicating misalignments in z/theta inside a sector. • Note that also clear MS effects within one sector are observed. • This is further confirmed by very high statistics studies performed by Phillipp Fleischmann. • What we learned from this: • can improve the alignment • using a z0 constraint might help a lot • Pierre-Francois Giraud is implementing this for the Barrel • For the Endcap Christoph and Ben and I look into this

  24. theta ID –theta SA correctedEndcap: eta Sector projections Interpretation: the observed structures are probably too big to come from the MS

  25. theta ID –theta SA correctedEndcap: eta Sector projections Interpretation: the observed structures are too big to come from the MS

  26. theta ID – theta SABarrel: eta Sector projections Interpretation for the Barrel? Looks like a global dtheta vs phi structure

  27. theta ID – theta SABarrel: eta Sector projections Interpretation for the Barrel? Statistics?

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