Monday 10, March 2003D. Guez - IPN Orsay - Alice week1 Station 1 chambers thickness Detector modeling and multiple scattering studies David GUEZ, Ivana Hrivnacova, Marion Mac Cormick – IPN Orsay ALICE Week – Monday 10, March 2003

Monday 10, March 2003D. Guez - IPN Orsay - Alice week2 Outline Goals Description and studies of the first quadrant. Detailed GEANT description. Modeling procedures Semi-simplified GEANT model. Whole chamber simulation Results Conclusions

Monday 10, March 2003D. Guez - IPN Orsay - Alice week3 Goals Global detector performances are highly dependent on the multiple scattering contribution (as described in the TDR)  chamber thickness One wants to update the estimation of the total amount of matter in the detector. The distribution of different detector materials implies resolution/efficiency variations. The GEANT description should be kept as simple as possible in order to not slow down simulations.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week4 Goals One wants to update the estimation of the total amount of matter in the detector. The distribution of different detector materials implies resolution/efficiency variations. The GEANT description should be kept as simple as possible.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week5 Detailed geometry First quadrant A very detailed investigation was carried out on the material composition of this quadrant. Each detector element is described separately. This work’s results are summarized in an internal note (IPNO-DR ). The geometry can be described in terms of elementary motifs (one per elementary electronic module)

Monday 10, March 2003D. Guez - IPN Orsay - Alice week6 Mother board Foam layer Kaptons Detector layers

Monday 10, March 2003D. Guez - IPN Orsay - Alice week7 Mother board Foam layer Kaptons Detector layers Hardware

Monday 10, March 2003D. Guez - IPN Orsay - Alice week8 Kaptons Detector layers Pad layer

Monday 10, March 2003D. Guez - IPN Orsay - Alice week9 Detector layers Connectors Kaptons

Monday 10, March 2003D. Guez - IPN Orsay - Alice week10 Detector layers Daughter boards

Monday 10, March 2003D. Guez - IPN Orsay - Alice week11 Description of the first quadrant The layout of all these elements leads to inhomogeneities in the chamber’s thickness. Object Mat erial Surfac e (1) X/X0 ref. /motif X/X0 ref /surf obj Sect eff ref/motif surf ref/obj X0 mate. simul Element thickness(%X 0 ) Volume /X0 Cathode plane Copper 1529,440,3280,36391,83101,67714,300 0,052 5,554 FR4 1479,170,2060,23699,73114,177194,000 0,458 3,488 Mechanical plan FR4 793,440,1030,22049,82106,331194,000 0,426 1,744 Foam 793,440,1250,26749,82106, ,000 21,023 2,117 Kapton Copper 900,000,2880,54142,820680,57114,300 0,077 4,871 Soldering Sn/Pb 456,000,1710,6347, ,9208,560 0,054 2,890 Berg connector Plastic 284,750,1310,7815,3131,579392,000 3,062 2,224 Copper 90,000,69913,1581,9236,12714,300 1,882 11,842 Mother card FR4 1693,440,147 71,5471,540194,000 0,285 2,489 Copper 1693,440,355 65,5165,51014,300 0,051 6,012 Daughter board FR4 1449,000,2210,25883,88898,040194,000 0,501 3,740 Copper 1449,000,6810,79580,806494,43814,300 0,114 11,524 Used as input for the simulations

Monday 10, March 2003D. Guez - IPN Orsay - Alice week12 Detailed GEANT description In the first model, all the motif elements are simulated individually.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week13 Detailed GEANT description Description : From the X/X 0 map, we define “iso- thickness” areas. zone One zone per area overlap

Monday 10, March 2003D. Guez - IPN Orsay - Alice week14 Detailed GEANT description Test : compares the effective simulated thickness, in each area, and the calculated one. Excellent agreement, but too many details.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week15 Simplification rules. Molière small angle scattering formula The material are regrouped in an “iso- thickness” area are within ±1.7%X 0 of the reference. For a free path of 10m, this range corresponds to a projected position inside ±50µm around the reference. → Within any “iso-thickness” area, the average scattering angle should be similar to the complex model.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week16 Fully simplified model First attempt All the materials are regrouped in a single aluminum layer: The average thickness per cathode is 3,91%X 0 → Volume distribution cannot be reproduced. Maximum difference in the connector area : 12,38%X 0. → Conclusion : the fully simplified model is too simple…

Monday 10, March 2003D. Guez - IPN Orsay - Alice week17 Semi simplified model 1 – Obvious areas defined. Daughter boards Motif Hole Soldering Kapton Connector (plastic) Connector (copper)

Monday 10, March 2003D. Guez - IPN Orsay - Alice week18 Semi-simplified model 2 – All materials is regrouped inside the naturally apparent elements. Element name Surface (mm²) Thickness (%X/X 0 ) Pad layer1693,4400,534 Mechanical plan793,4400,487 Kaptons900,000,541 Soldering456,000,634 Berg connector (plastic)284,750,781 Berg connector (copper)90,0013,158 Mother board1693,4400,502 Daughter board1449,0001,053

Monday 10, March 2003D. Guez - IPN Orsay - Alice week19 Semi-simplified model 3 – The model is defined From the complex model…

Monday 10, March 2003D. Guez - IPN Orsay - Alice week20 Semi-simplified model 3 – The model is defined … to the semi-simplified one

Monday 10, March 2003D. Guez - IPN Orsay - Alice week21 Semi-simplified model 4 – comparison with the complex model

Monday 10, March 2003D. Guez - IPN Orsay - Alice week22 Whole chamber simulation Using the mapping package, one can place several copies of the motif at their real positions. All the elements outside the sensitive area are also simulated in great detail. As a result, one can simulate a full quadrant.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week23 Whole chamber simulation

Monday 10, March 2003D. Guez - IPN Orsay - Alice week24 Whole chamber simulation Four identical copies of this quadrant are placed (at their z position) so the whole chamber is realistically simulated.

Monday 10, March 2003D. Guez - IPN Orsay - Alice week25 Results Thickness per zone Zone Minimum thickness (%X 0 ) Maximu m thickness (%X 0 ) Average thickness (%X 0 ) ,5110,30

Monday 10, March 2003D. Guez - IPN Orsay - Alice week26 Initial geometry Efficiency : 86,44% Resolution : 98.5 MeV/c² Starting point Results Upsilon invariant mass reconstruction

Monday 10, March 2003D. Guez - IPN Orsay - Alice week27 Results Upsilon invariant mass reconstruction

Monday 10, March 2003D. Guez - IPN Orsay - Alice week28 Results Upsilon invariant mass reconstruction Updated geometry Efficiency : 84,58% Resolution : MeV/c² Initial geometry Efficiency : 86,44% Resolution : 98.5 MeV/c²

Monday 10, March 2003D. Guez - IPN Orsay - Alice week29 Conclusions The updated geometry and the mapping package are successfully tested. The efficiency with the updated geometry is slightly deteriorated. The Upsilon mass resolution has increased by 5 MeV.