CMS WEEK – MARCH06 REVIEW OF MB4 COMMISSIONING DATA Giorgia Mila

1 CMS WEEK – MARCH06 MAIN TOPICS Giorgia Mila ANALYSIS TOOLS AND RESULTS 2. CALIBRATION 3. FIRST ALIGNMENT STUDIES

2 CMS WEEK – MARCH06 Full analysis Calibration Alignment ANALYSIS TOOLS 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

PROBLEMATIC CELLS 3 CMS WEEK – MARCH06 Wheel 1SL1L1SL1L2SL1L3SL1L4SL3L1SL3L2SL3L3SL3L4 Sector 2 8,76, , Sector 3--- Sector Sector (L.S.) --- Sector 8--- Sector DEAD CELLS & NOISY CELLS Full analysis Calibration Alignment Giorgia Mila

Full analysis Calibration Alignment Giorgia Mila EFFICIENCY - the method - 4 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 We count not only the hits associated to the segment We look only at the segments reconstructed with 7 or 8 hits inefficient cell We apply this method on data taken with a HH+HL trigger

EFFICIENCY (I) 5 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, Full analysis Calibration Alignment Giorgia Mila dead cell

EFFICIENCY (II) 6 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 Full analysis Calibration Alignment Giorgia Mila dead cells :

ANGULAR DISTRIBUTION - the method - 7 CMS WEEK – MARCH06 Full analysis Calibration Alignment Giorgia Mila We suppose that the measured angular distributions of reconstructed tracks N(φ) for a chamber with an angle φ o with respect to the vertical direction are : φ0φ0 N(φ, φ 0 )= k φ o · f(φ- φ 0 ) · acc(φ) With an iterative method including a combined fit of the measured angular distributions it is possible to extract: the cosmics angular distribution f(φ) (parameterized) kφ 0 · acc(φ) = angular dependence of the trigger acceptance acc(φ) = angular dependence of trigger acceptance (unknown) f(φ) = cosmics angular distribution (unknown) with : NOTE : the chambers must have the same internal geometry for more details see my presentation of

ANGULAR DISTRIBUTION (I) 8 CMS WEEK – MARCH06 We have studied the global angular trigger acceptance for the left chambers: (HH+HL trigger) Full analysis Calibration Alignment Giorgia Mila sector 5 sector 8sector 6 Trigger acceptance -30° 60° -60° Measured angular distributions 1. The trigger acceptance is asymmetric for MB4 2. Singular acceptances consistent one from the other NOTE :

ANGULAR DISTRIBUTION (II) 9 CMS WEEK – MARCH06 and the global angular trigger acceptance for the right chambers : sector 2 sector 3 sector 12 there is a range of angles where the trigger acceptance deviates a bit from the global one Full analysis Calibration Alignment Giorgia Mila 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

OCCUPANCY – sector CMS WEEK – MARCH06 sector 12 sector 6 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) Full analysis Calibration Alignment Giorgia Mila

t0-event correction 11 CMS WEEK – MARCH06 Full analysis Calibration Alignment Giorgia Mila We have used the t0-event correction (Anna’s routine) on our data t0 correctiont0 correction on logarithmic scale These tails give problems on digi computation (we had to reset them to zero) TDC counts

CALIBRATION 12 CMS WEEK – MARCH06 Full analysis Calibration Alignment Giorgia Mila We compute the t trig 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 res_posres_neg 3- We extract the drift velocity from the mean-timer distributions 1- We calculate the t mean and σ tmean by fitting the rising edge of the time box mean distance k 0

commissioning data & t0 correction (I) 13 CMS WEEK – MARCH06 Full analysis Calibration Alignment Giorgia Mila 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 ( t mean = σ tmean = ) k_SL3=2.81 ( t mean = σ tmean = ) When we recompute the residuals with these two k factors we obtain a point which is very distant from the linear fit k_SL1 mean distance

14 CMS WEEK – MARCH06 Full analysis Calibration Alignment Giorgia Mila commissioning data & t0 correction (II) 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 similar k 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

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

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 16 CMS WEEK – MARCH06 t0-event correction Full analysis Calibration Alignment Giorgia Mila Anna’s talk at the CMS week on 06/12/05

17 CMS WEEK – MARCH06 ALIGNMENT Full analysis Calibration Alignment Giorgia Mila 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 NOTE : for MB4 we restrict the study on two dimensions δ1δ1 δ2δ2 δ3δ3 δSLδSL δ4δ4 δ5δ5 δ6δ6 r1r1 r2r2 r3r3 r4r4 r5r5 r6r6 r7r7 r8r8 In our method we have 7 free parameters ( misalignments δ )

18 CMS WEEK – MARCH06 ALIGNMENT STUDIES – the method - Full analysis Calibration Alignment Giorgia Mila 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 : 1. fix δ SL (from ISR measurements) and calculate the layer misalignments (δ 1,2,... ) 2. fix the layer misalignments (from CCD measurements at the assembly sites) and extract δ SL

19 CMS WEEK – MARCH06 PRELIMINARY RESULTS Full analysis Calibration Alignment Giorgia Mila MB4 chamber - sector 2 - (cm)ISR (cm) δ SL CCD (cm) δ SL3 L δ SL3 L δ SL3 L δ SL1 L δ SL1 L δ SL1 L NOTE : we are working to understand the mismatches between our results and the measured data

1. We have finalized our tools we want to use to check the chamber performance on commissioning data. 2. We are using the ORCA Calibration Tool to calibrate the chambers 3. We are starting to use the t0-event correction routine (very useful but with some problems to be understood) 4. We are trying to check the alignments parameters on commissioning data in a simple way 20 CMS WEEK – MARCH06 CONCLUSIONS Giorgia Mila