Segmentation: Study of Shield & Absorber Materials Y.P.Viyogi(V.E.C.C) Arun Prakash(B.H.U)

Segmentation : Role of absorbers (study of shield and absorber material) “Standard” shield in CBMRoot is made of Tungsten : excellent absorber material but very expensive “Standard” absorbers for Muon stations : Iron, good material but for the first station we may need a non- magnetic material due to large fringe field of the magnet Hits in the inner region of first plane of station1 with ‘standard’ shield + absorber still beyond practical limits of pad size and rate capability of detectors (GEM) Study the role of material for shield and absorbers

Properties of common absorber material MaterialDensity (gm/cm^2)Rad. Length (cm)Int. length (cm) Iron Lead Tungsten19.3 (*) Uranium (? #) (*) density for industrially available material may be somewhat less (#) Spent Uranium has been used in many absorber applications (WA80 ZDC) Tungsten is the best absorber material Cost: Uranium << Tungsten

Study for Shield and Absorber UrQMD data at 25AGeV (for maximum particle density) Compact Muon Geometry, Hits on Layer 1 of Station 1, Front-GEM Use manual segmentation, hits using SimpleGEM, no clustering Hits slightly less than MC-points Use various combination of material for shield and absorber, only upto z-value relevant for station 1

Z-distribution of Hits : Station 1 shaded part : region of study

Shield : role of various material (absorber standard) Total hits for station 1 for Lead ~ 10% more than that for Tungsten Pb+W->W inside W+Pb->Pb inside

Absorber : various material at station 1

Shield : Previous study by Anna ■ Pb ■ Fe

Shield : Previous study by Anna Our present study supports this except there is a slight discrepancy for station 1 : density lowest for W in our case, but may be both agree with statistical limits

Summary and next steps Present study and extension of earlier study, only preliminary and at Hits level Effect of multiple scattering etc. (using very dense absorber) to be studied only by full tracking and reconstruction stages High density absorber may be minimized but not completely dispensed with for practical detectors in inner region. A composite absorber for station1 could be a better option : Pb/W upto ~40cm and Iron beyond