cms week – march06

CMS WEEK – MARCH06

REVIEWOF MB4

COMMISSIONING DATA

Giorgia Mila 17-03-06

1CMS WEEK –

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MAIN TOPICS


1. ANALYSIS TOOLS AND RESULTS2. CALIBRATION3. FIRST ALIGNMENT STUDIES

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Full analysisCalibrationAlignment

ANALYSIS TOOLS

For each MB4 chamber placed in the wheel 1, we have observed :• time boxes• occupancies• efficiencies• angular distributions• residual distributionsin order to check anomalies in the cell behavior

In general the chambers work fine but there are some problematic cells


PROBLEMATIC CELLS 3CMS WEEK – CMS WEEK –

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Wheel 1 SL1L1 SL1L2 SL1L3 SL1L4 SL3L1 SL3L2 SL3L3 SL3L4Sector 2 8,76,94 83 --- 4,23 --- --- --- ---Sector 3 --- --- --- --- --- --- --- ---Sector 5 4 --- --- --- 51 --- --- 3Sector 6 --- --- --- --- --- 1 (L.S.) --- ---Sector 8 --- --- --- --- --- --- --- ---

Sector 12 --- --- --- --- --- --- --- ---

DEAD CELLS & NOISY CELLS

Full analysisCalibration

Alignment Giorgia Mila 17-03-06



EFFICIENCY - the method - 4CMS WEEK – CMS WEEK –

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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) 5CMS WEEK – CMS WEEK –

MARCH06MARCH06Studying the MB4 efficiency we have found 2 cells which have a bad cathode HV connection :sector 5, SL3 L4 w 36,37 ....



dead cell

EFFICIENCY (II) 6CMS WEEK – CMS WEEK –

MARCH06MARCH06... 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 :

ANGULAR DISTRIBUTION - the method -

7

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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 :

φ0

N(φ, φ0)= kφo · f(φ- φ0) · 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)• kφ0· 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 8-02-06

ANGULAR DISTRIBUTION (I) 8CMS WEEK – CMS WEEK –

MARCH06MARCH06We have studied the global angular trigger acceptance for the left chambers:(HH+HL trigger)



sector 5 sector 8sector 6

Trigger acceptance

-30° 60°-60°

Measuredangular

distributions

1. The trigger acceptance is asymmetric for MB42. Singular acceptances consistent one from the other

NOTE :

ANGULAR DISTRIBUTION (II) 9CMS WEEK – CMS WEEK –

MARCH06MARCH06and the global angular trigger acceptance for the right chambers :

sector 2sector 3 sector 12there 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

OCCUPANCY – sector 12 10CMS WEEK – CMS WEEK –

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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)



t0-event correction 11CMS WEEK – CMS WEEK –

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We have used the t0-event correction (Anna’s routine) on our data

t0 correction t0 correction on logarithmic scale

These tails give problems on digi computation (we had to reset them to zero)

TDC counts

TDC counts

CALIBRATION 12CMS WEEK – CMS WEEK –

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2- We compute the ttrig correction by a k-factor : meantmeantrig ktt

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 tmean and σtmean by fitting the rising edge of the time box

mean distance

k0

commissioning data & t0 correction (I)

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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

k_SL1

mean distance


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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=1.79k_SL3=1.74

• a point on the fit (when we recompute the residuals) :

mean distance

k_SL1


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t0-event correction



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


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t0-event correction



Anna’s talk at the CMS week on 06/12/05


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ALIGNMENT



δ are the misalignments with respect to the nominal positions taking as reference the first layerr are the mean residuals from 8 point fits

NOTE : for MB4 we restrict the study on two dimensions

δ1δ2δ3

δSL

δ4δ5δ6

r1r2 r3r4

r5r6r7r8

In our method we have 7 free parameters ( misalignments δ )


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ALIGNMENT STUDIES – the method -



The residuals are correlated to the 7 misalignments by a linear relation :

SL

C

rrrrrrrr

6

5

4

3

2

1

8

7

6

5

4

3

2

1

where C is a matrix (8,7) and its rank is :

6C

We have 2 ways to compute misalignments :1. fix δSL (from ISR measurements) and calculate the layer misalignments (δ1,2, ... )2. fix the layer misalignments (from CCD measurements at the assembly sites)

and extract δSL


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PRELIMINARY RESULTS



MB4 chamber - sector 2 -

(cm) ISR (cm)δSL 0.00783165 0.003

CCD (cm)

δ SL3 L4 -0.000807 0.0175δ SL3 L3 0.0471147 -0.0148δ SL3 L2 0.0479869 0.0500δ SL1 L4 0.00795136 0.0059δ SL1 L3 0.0107243 0.0110δ SL1 L4 0.00955415 0.0085

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 chambers3. 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


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CONCLUSIONS


cms week – march06

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