design of the tesla very forward calorimeter

Design of the TESLA

very Forward Calorimeter

K. Afanasiev2, V. Drugakov2,

E. Kouznetsova1, W. Lohmann1, A. Stahl1

1 DESY - Zeuthen2 University of Minsk

DPG, Aachen, 10.03 – 13.03. 2003

Location and Requirements

• Detection and measurement of electrons and photons at small angles

• Fast beam diagnostic

• Shielding of the inner part of the detector

Beamstrahlung

• TESLA : Beam size 553 nm x 5 nm

↓ (pinch effect)

• ~6 x 1010 photons / BX

↓ (→e+e-, e-→e+e-e- , e+e-→e+e- e+e-)

• ~6 x 104 e+e- pairs / BX

Background Simulation

GUINEAPIG + BRAHMS( for √s = 500 GeV ) :

Per bunch crossing :

• ~15000 e± hit the LCAL• ~20 TeV of deposited

energy

Expected dose :

• for “bad” regions :up to 10

MGy/year(R,)-distribution of the deposited energy in

LCAL :

De

po

sit

ed

En

erg

y,

Ge

V

is required !

One of possible options for calorimeter technology

Diamond-tungsten sandwich

www.desy.de/~ghodbane

CVD DIAMONDradiation hardness

No decrease in the charge collection distance up to 10 MGy

Sandwich LCALgeometry

Z - Segmentation :

Tungsten 3.5 mm

Layer == 1 X0

Diamond 0.5 mm

(R,) - Segmentation :

Tungsten absorber +

Diamond sensor

=> Cell size = 0.5 cm

RM ~ 1 cm

Signal and background

250 GeV e- + BG :

Signalreconstruction

sensor PA/discr ADC

reconstructionAlgorithm :

• 10 previous BG -> average BG + RMS

• “Suspected” cells : ECELL > 3 BG

reasonable z-location

• Requirement of a longitudinal chain of such cells

Sandwich LCALrecognition

Efficiency vs radius :

Sandwich LCALrecognition

Fake rate :

(BG of high energy + BG fluctuations)

( 50

0 b

un

chcr

oss

ing

s )

Sandwich LCALrecognition

Energy resolution vs radius :

Sandwich LCALrecognition

Energy resolution vs radius :

Sandwich LCALrecognition

Polar angle resolution vs radius :

Sandwich LCALRecognition

Calibration :

Averaged energy resolution :

Sandwich LCALRecognition

Averaged angular resolution :

CONCLUSIONS

sandwich diamond-tungsten calorimeter seems to be a promising technology

high energetic e±, can be detected with reasonable efficiency even near the beam pipe, on top of the extremely high background

“hardware part” of the study has been started