09/07/20021Burkhard Schmidt Muon Station M1 Outline: Material Budget –What is the present best estimate of the material budget of a “default” MWPC station –What was in SICBMC until end of June –What has been implemented now (Summary of recent LHCb light meetings with some corrections) Some points to be sorted understood better

09/07/20022Burkhard Schmidt Material Budget Muon station with “default” 4 gap MWPC chambers: (All numbers are averaged over the station surface area of 49m 2 ) 5 panels of: 2x0.8mm FR4 (G10) + 8.4mm foam 2x35  m Cu: 2.2% X 0 x 5 = 11% X 0 Chamber borders have overlap, which brings the value up by 45%: 16% X 0 Chamber border with WF-bars and other frames adds about 4% X 0 Cables and connectors add about 2.5% X 0 FE-boards (HVB, SPB, ACB) and connectors add about 3x 0.65% X 0 board, the GPS about 1.5% X 0, hence in total about 3.5% X 0 The Al support of 3mm adds about 3.4% X 0 -> Total radiation length (including ~1% for unknown things) 30% X 0

09/07/20023Burkhard Schmidt Material Budget SICBMC until end of June: 8.2% X 0 FR4 sheets (1.6mm thick -> should be 0.8mm for R3 R4) 3.5% X 0 Copper on the cathodes (50  m/layer) 0.6% X 0 Honeycomb structure 2.3% X 0 Support structure (2mm Al) -> 14.4% X 0 Drawbacks: No overlap of the chambers was in, No chamber border was in, The assumed panel material is honeycomb, No cables and connectors are in, No FE-boards and connectors are in, The Al support is 3mm instead of 2mm.

09/07/20024Burkhard Schmidt Material Budget: Where could we win? 1. # of Gaps:4 gaps versus2 gapsrel. gain Al support Chambers FE-boards Cables Unknown Total 30% X 0 21% X 0 -30% 2. Doubling the chamber height: Chambers % Total 25% X 0 19% X 0 3. Honeycomb instead of foam (default height): Chambers % Total 23.5% X 0 17% X 0 Max. possible: 21% X 0 15% X 0

09/07/20025Burkhard Schmidt M1 Chamber Layout in SICBMC OLD Chamber description NEW Chamber description ( 4 gaps ) ( 2 gaps ) 14.4% X % X 0 (Implemented by D.Hutchcroft)

09/07/20026Burkhard Schmidt New M1 Chamber Layout in SICBMC OLD Chamber layout NEW Chamber layout (no border and overlap)(frames and overlap in) Chamber with 4cm frame of G10/air mix ( To account for bars to close gas volume, FE-boards, cables etc.) -> Frame adds 8%X 0 in average. However, there are non-uniformities: Some part of area (ranging from 3% in R3+4 to 13% in R1) has 56% X 0, about 42% of area we have 25% X 0, and about 55% of area has 10% X 0. -> New average X 0 in SICBMC: 18%

09/07/20027Burkhard Schmidt GEANTINO study (Gloria)

09/07/20028Burkhard Schmidt Total X 0 in front of the Calo (SPD)

09/07/20029Burkhard Schmidt M1 contribution

09/07/200210Burkhard Schmidt New Rate estimate for M1 Note, that: The new estimate is based on very limited Statistics (stat. error 5%) Old estimate was done with GCALOR, new one not, includes however spillover. Both effects are small (a few percent) -> Rate in R1 went down by 20%, in all other regions NO appreciable reduction.

09/07/200211Burkhard Schmidt How to Proceed ? Some considerations: Significant gain in the M1 material budget beyond the 15-20% X0 level is difficult and would imply a mayor re-design of M1. If the M1 material contribution is really that harmful for Photon reconstruction ( further proves are certainly required ! ), the whole area around M1 and SPD should be re-optimized. -> Muon group needs feedback from calo group to know where we are -> This would be important input for a layout optimization