U.GaspariniCMS week, 11/06/021 MB3 internal alignment study using cosmic muons - 14 MB3 chambers assembled in Legnaro have been extensively tested using cosmic run data (some preliminary results on internal layer and SL alignment on first 3 chambers already presented at CMS week in June 2002) - afterHV tests, pressure tests, noise/rate test, dead-channel test on each single SL (performed with scalers before chamber assembling ), assembled chambers are put on a cosmic station test ( 1/2 chamber per time is tested) and a full DAQ => local rec. chain ; ORCA, running on Obj.database; all data stored/archived there) [ Noise,rate, tmax results and wire position measurements in SL stored in ‘database’ on Web (M.Passaseo, P. Checchia, E.Torassa,A.Meneguzzo,F.Cavallo): http: // CMS note in preparation ] A.Meneguzzo, M.Zanetti, U.G. (special thanks to M.De Giorgi, F.Gonella, S.Vanini, P.Ronchese)

U.GaspariniCMS week, 11/06/022 Cosmic run data Full MB3 chamber in Legnaro: cosmic angle (rad) x (cm) ½ chamber instrumented in this run

U.GaspariniCMS week, 11/06/023 Testing  -SL alignment 232  14  m  0.13 mrad MB3_08 x2x2 x1x1 All 4 point tracks, |  < 20 o build 4 point segment in each single SL Extrapolate to the middle plane of the chamber

U.GaspariniCMS week, 11/06/024 3 point fit residuals <>=8  6  m 32  6  m 34  5  m 22  5  m 32  6  m 11  5  m 10  5  m 27  6  m SL  2SL  1 MB3_08

U.GaspariniCMS week, 11/06/025 3 point fit residuals & intercept and slope difference 112  -layers (8x 14) 14 chambers Slope difference (mrad) intercept difference (  m) Hit residuals(  m) Ch. 3, 8, 9, 18 (residual averages in all 8 layers < 75  m )

U.GaspariniCMS week, 11/06/026  -SL (apparent) misalignments syst.err  y extr

U.GaspariniCMS week, 11/06/027 T max in left – right half cells “Good” SL (MB3_08, SL2) “Bad” SL (MB3_05 SL2) left semicell right semicell  T=2.9  0.2 ns  T=-2.3  0.2 ns  T=0.4  0.2 ns  T=0.0  0.2 ns

U.GaspariniCMS week, 11/06/028 3 point fit residuals 10 of the 14 chambers analyzed have at least 1 “good” SL: best SL worst SL 40 layers (=4x10)

U.GaspariniCMS week, 11/06/029 Average residuals w.r.t. extrapolation from other SL “best” “worst” - use values marked by arrows as alignment correction of corresponding layer - look to 3 point fit residuals in corrected SL; if all average 3 point fit residuals are < 50  m, stop here; otherwise, repeat procedure a 2nd time

U.GaspariniCMS week, 11/06/ point fit residuals in worst SL Before correction After correction (max 2 layers in a SL moved)

U.GaspariniCMS week, 11/06/0211  -SL misalignments 4 chambers (nr. 4, 7, 11, 14) have 2 “bad” SL’s : they need a more refined layer alignment procedure In each SL, consider the 4 (not independent) Tmax combinations:  T = T max L -T max R  1 =v drift  T 234,  2 =v drift  T 134,.... and the quantities: The system:  i =  a ij  j with: may be solved considering the misalignments  j w.r.t. one layer, under the assumption that only 2 of the other 3 have displacement significantly different from zero w.r.the reference one uknown misalignments

U.GaspariniCMS week, 11/06/0212  -SL misalignments  6 possible solutions for each SL  6x6= 36 possible layer configurations in the chambers  Only fews give slope differences  compatible with zero  Take the configuration with minimum  (=slope difference between Segments in the 2 SL) as the best one and use the corresponding  x (intercept difference) as best estimate of the SL misalignment; take the maximum semi-dispersion of all possible  x as estimation of systematic error on the SL misalignment

U.GaspariniCMS week, 11/06/0213  -SL misalignments before corrections after corrections syst.err  y extr syst.err  (  2  max /3.9)  y extr Chambers with 2 “bad” SL max.of averages of 3 pont fit residuals

U.GaspariniCMS week, 11/06/0214 single layer alignment corrections

U.GaspariniCMS week, 11/06/0215 Conclusions - A procedure to measure internal misalignments in the  SL of the chambers using cosmic rays has been proposed and applied to 14 MB3 chambers assembled in LNL - the  SL relative position,  SL, can be measured within a systematic error of less than 300  m -12 chambers show  SL values well below the 1 mm construction tolerance; 2 chambers are at the limit of this value - 6 out of 112 layers have an alignment correction bigger than 100  m