MaterialStudy

FORWARDS FIT

negative phi

   $N_i$ = $N_e$ nMod_i ( X $D_i$ /$sin \theta$ +$C_i$) (1)

Ne = Number events/100000

4 layers in negative phi used to find values of D and C

X fixed =1

VAR VALUE ERROR  
D1 12.9681 0.843960
D2 31.4216 1.19890
D3 27.1672 1.10404
D4 5.55769 0.564706
C1 -8.75987 0.962665
C2 -19.2786 1.37036
C3 -14.2078 1.26846
C4 -1.07452 0.655159

see attachments below ForwardsFitNegPhi.eps

C negative (not exactly what want) But this shows that range |Eta|<1 material varies as 1/sin Theta

Then in positive phi

add linear term to X

 X+ m $\eta$ +c

To account for extra material of 0.5-1.5% Interaction lengths in SCT2

Fix Ds and Cs

VAR VALUE ERROR
m 0.0782631 0.0115899
c 0.0366751 0.0661413

see attached nModmEtaPlusc.pdf

4-12% extra ??

(~4% at eta =0 increasing to ~12% at |eta|=1)

This does not take into account brem seen in next layer.

Ntuple kindly sent from Pat Ward: Mean number interaction lengths traversed by particle through SCT barrel. I fitted 8/sinTheta - could then presume each SCT layer contributes 2% interaction lengths

see SCTInteractionLengths.eps

OR

If consider each SCT layer has silicon thickness 285 microns ~0.61% radiation lengths ~ 3% interaction lengths

(Silicon radiation length 21.82 gcm-2, nuclear interaction length 108.4gcm-2)

So my 4% extra material seen at eta=0 corresponds to 4% of 2.5% = 0.1% interaction length

(Expecting 0.5% interaction length which corresponds to 1% radiation length carbon))

I said it wasn't clever!

Oh. And you know its in SCT 2 because when you look at Backwards fit, it totally obvious.

see attachments below

NumberHitsSCTBackwards.eps

-- SueCheatham - 9 Sept 2009

Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formateps ForwardsFitNegPhi.eps r1 manage 53.1 K 2009-09-09 - 20:01 SueCheatham Negative Phi SCT layers fitted with 1/sinTheta. Same fit shown on positive phi
Unknown file formateps NumberHitsSCT.eps r1 manage 53.3 K 2009-09-09 - 20:18 SueCheatham Number of hits in positive phi clearly more than in negative phi
Unknown file formateps NumberHitsSCTBackwards.eps r1 manage 50.6 K 2009-09-09 - 22:30 SueCheatham Backwards Fit
Unknown file formateps SCTInteractionLengths.eps r1 manage 13.1 K 2009-09-10 - 00:06 SueCheatham SCT material budget in interaction lengths
PDFpdf nModmEtaPlusc.pdf r1 manage 26.2 K 2009-09-09 - 20:03 SueCheatham Parameters from negative phi fit fixed. Linear term added to positive phi to account for extra material.
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Topic revision: r7 - 2009-10-13 - SueCheatham
 
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