instrumentation of the forward region of the tesla detector
DESCRIPTION
Instrumentation of the Forward Region of the TESLA Detector. International Europhysics Conference on High Energy Physics Aachen, July 19th 2003. TESLA. T eV E nergy S uperconducting L inear A ccelerator. Main Parameters Energy: 90 to 800+ GeV - PowerPoint PPT PresentationTRANSCRIPT
Karsten Büßer
Instrumentation of the Forward Region of the TESLA Detector
International Europhysics Conference on High Energy Physics
Aachen, July 19th 2003
19/07/2003
2Karsten Büßer, EPS-HEP Conference Aachen
TESLA
TeV Energy Superconducting Linear Accelerator
Main Parameters
• Energy: 90 to 800+ GeV• Luminosity (500GeV): 3.4 x 1034 cm-2 s-1
• Beam size (500 GeV): 553 x 5 nm
Physics Potential
Precision measurements and searches in:• Higgs physics• Supersymmetry• EW precision tests (GigaZ)• QCD and top thysics• yet unimagined physics
19/07/2003
3Karsten Büßer, EPS-HEP Conference Aachen
The TESLA Detector
Detector Concept
• Precision vertex detector• Large gas filled central tracking detector• Highly segmented calorimeters• 4T magnetic field, tracking detectors and calorimeters inside the coil
19/07/2003
4Karsten Büßer, EPS-HEP Conference Aachen
Beam Induced Backgrounds
Main background source for the detector are beamstrahlung pairs
19/07/2003
5Karsten Büßer, EPS-HEP Conference Aachen
• Shielding of the tracking detectors against backscattered beamstrahlung background• Provide instrumentation for:
• Precision luminosity measurement• Hermeticity:
→ Extension of the energy flow measurement down to small angles • Beam diagnostics
Tasks for the Forward Region
GEANT3 simulation of 10 pair particles
19/07/2003
6Karsten Büßer, EPS-HEP Conference Aachen
• Instrumented tungsten mask
• Two calorimeters:
• LAT Low Angle Tagger27.5 – 83.1 mradactual task :„Luminosity Calorimeter“
• LCAL Luminosity Calorimeter
4.6 – 30 mradactual task: „Beam Calorimeter“
TESLA Forward Calorimeters
19/07/2003
7Karsten Büßer, EPS-HEP Conference Aachen
Physics Requirements: ΔL/L ≈ 0.02% (GigaZ)
Process: e+ e- → e+ e- elastic Bhabha Scatteringe+ e- → e+ e- γ radiative Bhabha Scattering
Statistics: for L = 3.4 x 1034 cm-2 s-1 rate R ≈ 170 Hz
Systematics:• from detector acceptance:
since σtot
(Θmin
,Θmax
) ~ Θmin
-2 – Θmax
-2 ≈ Θmin-2
then ΔL/L = 2ΔΘmin
/Θmin
with Θmin
= 27.5 mrad,
ΔL/L = 10-4 ΔΘmin
= 1.4 µrad (!)• from theory:
At LEP achieved: 5.0 x 10-4
Luminosity Measurement
19/07/2003
8Karsten Büßer, EPS-HEP Conference Aachen
Geometry(as defined in the TESLA TDR)
• 14 cylinders in Θ 24 sectors in Φ 40 rings in z 13440 cells in MC studies
• Conical Setup
• r: 4 – 12 cm (not affected by beamstrahlung pairs) z: 140 – 200 cm
• Silicon/Tungsten sandwich 40 X
0
Low Angle Tagger
The LAT serves as a shield !
19/07/2003
9Karsten Büßer, EPS-HEP Conference Aachen
Energy Response Energy Resolution
LAT Performance
GEANT3 simulation studies show the response to high energetic electrons
19/07/2003
10
Karsten Büßer, EPS-HEP Conference Aachen
Energy Response and Resolution Angular Resolution
Red: Cut on desposited energy (>2.5 GeV)
LAT Performance
19/07/2003
11
Karsten Büßer, EPS-HEP Conference Aachen
LAT Outlook• New TESLA beam optics are under development which would allow to move the quads out of the detector (increasing l* from 3m to ≤5m).
• Mask and calorimeters would move
• Flat LAT seems possible
• Simulation studies for a flat LAT are under way → angular resolutions down to 1.4 µrad are still challenging!
• Alignment tolerances for detectors are stringent:
• Δz < 60 µm
• Δr < 0.75 µm
Alignment monitor system probably needed
TESLA-TDRl*=3m
Design studyl*=4.1m
19/07/2003
12
Karsten Büßer, EPS-HEP Conference Aachen
Technology options under study:
• Diamond -Tungsten Sandwich, rm~ 1cm
• Crystal PbWO4, r
m~ 2cm
30 layers, 30 X0
The LCAL
19/07/2003
13
Karsten Büßer, EPS-HEP Conference Aachen
Pairs from Beamstrahlungper bunch crossing (BX)
Produced:#: ~130000, E
tot: ~360 TeV
on each LCAL:#: ~15000, E
tot: ~20 TeV
Deposited Energy, Diamond/W
LCAL and Pair Background
Dose: ≤ 10 MGy/y
19/07/2003
14
Karsten Büßer, EPS-HEP Conference Aachen
LCAL as Beam Monitor
• Number of produced pairs is a measure of the luminosity• Deposited energy on the LCAL is input for the TESLA fast feedback system• rΦ energy distribution on the LCAL is an indicator for beam misalignments
nominal beam
tilted beam: x‘=3.5 mrad
19/07/2003
15
Karsten Büßer, EPS-HEP Conference Aachen
One 250 GeV electron and pair background from one BX
Generated Background added Reconstructed
LCAL as Physics Device
19/07/2003
16
Karsten Büßer, EPS-HEP Conference Aachen
Simple algorithm:
• subtract average (10 BX) background• search for cells with signal > 3σ of background fluctuation• require longitudinal chain of signal cells
4.6 mrad30 mrad
Reconstruction
19/07/2003
17
Karsten Büßer, EPS-HEP Conference Aachen
Energy Resolution of the LCAL
Energy resolution is dominated by the background
19/07/2003
18
Karsten Büßer, EPS-HEP Conference Aachen
500 BX
Fake Rates
19/07/2003
19
Karsten Büßer, EPS-HEP Conference Aachen
ConclusionLAT
• Luminosity measurment with 0.02% accuracy will be challenging
LCAL
• Several technologies are under study• Detection of high energetic electrons is possible with high efficiency below 10 mrad• Energy resolution is dominated by background subtraction• Need to look into more clever algorithms
OUTLOOK
• TESLA interaction region might change (increasing l*)→ Redesign of the forward region, impact on
calorimeters ?• R&D has started
Test stand for Si and Diamond sensors in Zeuthen