1. Vertex detector update 1 Oct. 2004 Y. Sugimoto KEK

2. Layer Configuration Forward disks as shown in the figure below are proposed in the previous meeting. However, it may not be practical How to support ladders? How to put end-plate? Vertex detector consisting of only barrel is considered

3. Wrong tracking probability Wrong tracking probability due to multiple scattering increases in the forward region as sin -4  In order to reduce the probability Thinner wafer Smaller distance between 1 st and 2 nd layers Decrease b.g. hit density (i.e. larger R) R Signal hit Background hit d

4. Wrong tracking probability t = 70  m p = 1 GeV/c  = 100hits/mm 2 cos  =0.95 1%

5. Wrong tracking probability t = 50  m p = 1 GeV/c  = 100hits/mm 2 (R < 20 mm)

6. Wrong tracking probability t = 50  m p = 1 GeV/c  = 30hits/mm 2 (R = 24 mm)

7. Impact parameter resolution Configurations A: R= 20,21,32,34 mm A’: R=20,21,32,34,48,50 mm B: R=22,24,32,34 mm B’: R=22,24,32,34,48,50 mm C: R=24,26,32,34 mm C’: R=24,26,32,34,48,50 mm Common t = 50  m  pixel =1.44  m B=3T Beampipe:R=15mm, t=250  m p (GeV/c)  IP (  m)

8. A possible layout

9. Summary A tentative design of the vertex detector using fine pixel CCD is studied If layer thickness is 50  m, the wrong tracking probability is less than 1% for 1GeV/c tracks in cos  <0.95 with Rmin=20mm and d=1mm, or Rmin=24mm and d=2mm (B.G. rejection using hit pattern of pixels not included) Impact parameter resolution is close to the target value of  b =5  10/(p  sin 3/2  )  m for Rmin=20 – 24 mm Wafer thickness less than 50  m is desirable both for tracking efficiency and for impact parameter resolution