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CMS WEEK – MARCH06

CMS WEEK – MARCH06. REVIEW OF MB4 COMMISSIONING DATA. Giorgia Mila 17-03-06. 1. MAIN TOPICS . CMS WEEK – MARCH06. ANALYSIS TOOLS AND RESULTS CALIBRATION FIRST ALIGNMENT STUDIES. Giorgia Mila 17-03-06. Full analysis. Calibration. Alignment. 2. ANALYSIS TOOLS. CMS WEEK – MARCH06.

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CMS WEEK – MARCH06

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  1. CMS WEEK – MARCH06 REVIEW OF MB4 COMMISSIONING DATA Giorgia Mila 17-03-06

  2. 1 MAIN TOPICS CMS WEEK – MARCH06 • ANALYSIS TOOLS AND RESULTS • CALIBRATION • FIRST ALIGNMENT STUDIES Giorgia Mila 17-03-06

  3. Full analysis Calibration Alignment 2 ANALYSIS TOOLS CMS WEEK – MARCH06 • For each MB4 chamber placed in the wheel 1, we have observed : • time boxes • occupancies • efficiencies • angular distributions • residual distributions • in order to check anomalies in the cell behavior • In general the chambers work fine but there are some problematic cells Giorgia Mila 17-03-06

  4. Full analysis Calibration Alignment 3 PROBLEMATIC CELLS CMS WEEK – MARCH06 DEAD CELLS & NOISY CELLS Giorgia Mila 17-03-06

  5. Full analysis Calibration Alignment 4 EFFICIENCY - the method - CMS WEEK – MARCH06 We measure the efficiency from the segment extrapolation : we take a reconstructed segment and for the cells it goes through we look if there is a hit or not inefficient cell We look only at the segments reconstructed with 7 or 8 hits We count not only the hits associated to the segment We apply this method on data taken with a HH+HL trigger Giorgia Mila 17-03-06

  6. Full analysis Calibration Alignment 5 EFFICIENCY (I) CMS WEEK – MARCH06 Studying the MB4 efficiency we have found 2 cells which have a bad cathode HV connection : sector 5, SL3 L4 w 36,37 .... dead cell Giorgia Mila 17-03-06

  7. Full analysis Calibration Alignment 6 EFFICIENCY (II) CMS WEEK – MARCH06 ... but also an inefficient cell which has a good time box (maybe a strip HV problem – to be investigated) : sector 2, SL1 L1 w21 dead cells : Giorgia Mila 17-03-06

  8. φ0 Full analysis Calibration Alignment 7 ANGULAR DISTRIBUTION - the method - CMS WEEK – MARCH06 We suppose that the measured angular distributions of reconstructed tracks N(φ) for a chamber with an angle φo with respect to the vertical direction are : N(φ, φ0)= kφo· f(φ- φ0) · acc(φ) acc(φ) = angular dependence of trigger acceptance (unknown) f(φ) = cosmics angular distribution (unknown) with : • With an iterative method including a combined fit of the measured angular distributions it is possible to extract: • the cosmics angular distributionf(φ) (parameterized) • kφ0· acc(φ)= angular dependence of the trigger acceptance NOTE : the chambers must have the same internal geometry for more details see my presentation of 8-02-06 Giorgia Mila 17-03-06

  9. Trigger acceptance Measuredangular distributions -30° -60° 60° Full analysis Calibration Alignment 8 ANGULAR DISTRIBUTION (I) CMS WEEK – MARCH06 We have studied the global angular trigger acceptance for the left chambers: (HH+HL trigger) sector 6 sector 8 sector 5 NOTE : • The trigger acceptance is asymmetric for MB4 • Singular acceptances consistent one from the other Giorgia Mila 17-03-06

  10. sector 12 Full analysis Calibration Alignment 9 ANGULAR DISTRIBUTION (II) CMS WEEK – MARCH06 and the global angular trigger acceptance for the right chambers : sector 2 sector 3 there is a range of angles where the trigger acceptance deviates a bit from the global one The trigger angular acceptance changes sign moving from right chambers to left chambers: this confirms that the asymmetry is related to the staggering between the SLs Giorgia Mila 17-03-06

  11. Full analysis Calibration Alignment 10 OCCUPANCY – sector 12 CMS WEEK – MARCH06 We suspect that the trigger configuration was changed for the commissioning of the chamber placed in sector 12: in fact it has an occupancy distribution very different from the other MB4 chambers(we don’t see the regular pattern of drops in the cell occupancy) sector 6 sector 12 Giorgia Mila 17-03-06

  12. Full analysis Calibration Alignment 11 t0-event correction CMS WEEK – MARCH06 We have used the t0-event correction (Anna’s routine) on our data t0 correction t0 correction on logarithmic scale TDC counts TDC counts These tails give problems on digi computation (we had to reset them to zero) Giorgia Mila 17-03-06

  13. res_neg res_pos mean distance k Full analysis Calibration Alignment 12 CALIBRATION CMS WEEK – MARCH06 1- We calculate the tmean and σtmean by fitting the rising edge of the time box 2- We compute the ttrig correction by a k-factor : The method to compute the correct k-factor: we plot residuals distributions using different k-factors for each k-factor we compute the distance from the means of residuals in the left and in the right part of the cell we fit this distance with a line and we extrapolate the k corresponding to the distance=0 0 3- We extract the drift velocity from the mean-timer distributions Giorgia Mila 17-03-06

  14. Full analysis Calibration Alignment 13 commissioning data & t0 correction (I) CMS WEEK – MARCH06 Using the routine for the t0-event correction we obtain 2 different k-factors for the 2 phi SLs. For example for the MB4 chamber placed in sector 6: k_SL1=1.84 ( tmean = 1881.68 σtmean = 7.95756 ) k_SL3=2.81 ( tmean = 1880.86 σtmean = 7.74864 ) When we recompute the residuals with these two k factors we obtain a point which is very distant from the linear fit mean distance k_SL1 Giorgia Mila 17-03-06

  15. Full analysis Calibration Alignment 14 commissioning data & t0 correction (II) CMS WEEK – MARCH06 • If we compute the k factor which minimize the distance from the means of residuals without the t0 correction routine, we obtain a reasonable calibration: • very similark factors for the 2 SLs (we use their mean) • For example for the MB4 chamber placed in sector 6: • k_SL1=1.79 • k_SL3=1.74 • a point on the fit (when we recompute the residuals) : mean distance k_SL1 Giorgia Mila 17-03-06

  16. Full analysis Calibration Alignment 15 t0-event correction CMS WEEK – MARCH06 We calibrate without the t0-event correction, and after we apply the t0-event correction routine to the data. It seem to work well : Residuals : not t0-event correction vs t0-event correction (MB4 chamber : wheel1, sector 6, SL1) σ=526μm σ=328μm Giorgia Mila 17-03-06

  17. Full analysis Calibration Alignment 16 t0-event correction CMS WEEK – MARCH06 Anna’s talk at the CMS week on 06/12/05 The t0-event correction improve the σ of residuals but it remain of about 300 μm ! ... one possibility is that we use different chi2 cuts in the track selection Giorgia Mila 17-03-06

  18. δSL δ1 r1 δ2 r2 δ3 r3 r4 δ4 r5 δ5 r6 δ6 r7 r8 Full analysis Calibration Alignment 17 ALIGNMENT CMS WEEK – MARCH06 In our method we have 7 free parameters ( misalignments δ ) NOTE : for MB4 we restrict the study on two dimensions δ are the misalignments with respect to the nominal positions taking as reference the first layer r are the mean residuals from 8 point fits Giorgia Mila 17-03-06

  19. Full analysis Calibration Alignment 18 ALIGNMENT STUDIES – the method - CMS WEEK – MARCH06 The residuals are correlated to the 7 misalignments by a linear relation : where C is a matrix (8,7) and its rank is : • We have 2 ways to compute misalignments : • fix δSL (from ISR measurements) and calculate the layer misalignments (δ1,2, ... ) • fix the layer misalignments (from CCD measurements at the assembly sites) and extract δSL Giorgia Mila 17-03-06

  20. Full analysis Calibration Alignment 19 PRELIMINARY RESULTS CMS WEEK – MARCH06 MB4 chamber - sector 2 - NOTE : we are working to understand the mismatches between our results and the measured data Giorgia Mila 17-03-06

  21. 20 CONCLUSIONS CMS WEEK – MARCH06 • We have finalized our tools we want to use to check the chamber performance on commissioning data. • We are using the ORCA Calibration Tool to calibrate the chambers • We are starting to use the t0-event correction routine (very useful but with some problems to be understood) • We are trying to check the alignments parameters on commissioning data in a simple way Giorgia Mila 17-03-06

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