LAT performance studies

Results from Cracow

(by A.Kowal, B.Pawlik, L.Zawiejski)

L.Suszycki

AGH University of Science and Technology Cracow

L. Suszycki Prague, 15-17 April 2004 2

Forward Calorimetry Region

with new design of the Mask

LAT parameters:• distance from the IP

305-325 cm• radial dimensions

8-28 cm• angular coverage

– 26.2<<82 mrad– 0<<360 deg

L. Suszycki Prague, 15-17 April 2004 3

LAT detector versions

Switching the geometry:

From the conical one (TDR version)

to the cylindrical one.

Two competitive structures of the Si/W sandwich calorimeter are considered:

• Si pads • Si strips

L. Suszycki Prague, 15-17 April 2004 4

Simulated LAT pad-structure

Si pads/W calorimeter 16 cylinders (in r) 30 rings (in z) 24 sectors (in )=> 11520 channels analyzed angular range:

30<<78 mrad 0<<360 deg

L. Suszycki Prague, 15-17 April 2004 5

Simulated LAT pad-structure 2

Large statistics behaviour Angular reconstruction not

satisfactory –

Simple reconstruction bias and resolution ~0.2 - 0.3mrad,

(with 16 cylinders),

can be reduced at price of large #channels

L. Suszycki Prague, 15-17 April 2004 6

Stripped LAT description

• LAT consists of 30 tungsten disks

• Each disk has silicon strip detector attached

• Every second detector has either 120 radial or 64 concentric strips

• In total there is 2960 read-out channels

L. Suszycki Prague, 15-17 April 2004 7

Stripped LAT reconstruction Accuracy of order 0.5x10-4 radian in measuring polar angle

Measurement of 250GeV electron energy with accuracy 5GeV (ΔE~0.31√E)

L. Suszycki Prague, 15-17 April 2004 8

Stripped LAT - Bhabha events Measurement of the scattered electron energy with accuracy 7GeV

(ΔE~0.44√E)

Egen - Erec

L. Suszycki Prague, 15-17 April 2004 9

Stripped LAT - Bhabha events 2

Reconstruction of energy of the back-to-back electron pair

E (GeV)

L. Suszycki Prague, 15-17 April 2004 10

Stripped LAT - Bhabha events 3

Reconstruction of theta angle of the back-to-back electron pair

Gen.

Rec.

θ (mrad)

L. Suszycki Prague, 15-17 April 2004 11

Stripped LAT - Bhabha events 4

Acolinearity

θL – θR (mrad)

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Stripped LAT - Bhabha events 5

Angle reconstruction accuracy ~0.09 mrad

θgen – θrec (mrad)

L. Suszycki Prague, 15-17 April 2004 13

Beamstrahlung background

No photons are seen in LAT (θ>26 mrad)

L. Suszycki Prague, 15-17 April 2004 14

Beamstrahlung background 2

L. Suszycki Prague, 15-17 April 2004 15

Beamstrahlung background 3Pairs from beamstrahlung in LAT angular range

L. Suszycki Prague, 15-17 April 2004 16

Beamstrahlung background 4Energy from beamstrahlung in LAT angular range

and azimuthal angle 0/180 degrees

Background may be present at rmin

(deg)

(deg)

L. Suszycki Prague, 15-17 April 2004 17

Summary• LAT with pads: reconstruction

algorithm to be improved or changed completely

• Stripped LAT: seems ok

• Bhabha events: in progress

• Beamstrahlung: needs detector simulation

The end

Thank you

L. Suszycki Prague, 15-17 April 2004 19

Notices

Stripped LAT: E_rec = 60.79*E_seen

Generated 20 000 events, reconstr. 9800 (26 – 86 mrad)

Beamstrahlung: TDR, FC Proposal 20-40 TeV/bx, Jeju 20 TeV

A.Stahl 500 TeV/bx photons, 100 TeV/bx pairs

(in BeamCal 5 TeV/bx and 20 TeV/bx) – Zeuthen Nov 2002

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Reconstruction results (512ch)