1

PEBS - Positron Electron Balloon SpectrometerDetector Concept

CERN, January 2009

Stefan SchaelI. Physikalisches Institut BRWTH Aachen

2

3

PEBS Experiment

4

1,6 mσ P

P= 0.0017 ⋅P

improve the momentum resolution by a factor of 10 !

5

6

7

8

RICH RICH

SRDSRD

PEBS-ECAL

TRD 1

TRD 2

1.2 m

1.0 m

0.86 m

2.0 m

Physic-Programm:• Positron – Spectrum 1 GeV - 700 GeV• Electron – Spectrum 1 GeV – 1000 GeV

B-Field: 0.7 TeslaSuperconducting magnet, 850 kg

Acceptance: 3000 cm2 sr

6 Si-Inner-Tracker Planes (red),single Point resolution 0.010 mm4 ScFi-Outer Tracker Planes (pink)single Point resolution 0.050 mm

momentum resolution:20% @ 1000 GeV

2 TRD‘s, each with 12 layers,Proton Rejection 104 @ 100 GeVElectron Efficiency 80%

11 X0 ECAL, Weight 650 kg

Weight: 1700 kg

1080 cm long ladders !

11

12

13

Inner Si Tracker Upper SciFi TrackerUpper SciFi Tracker

Circle-FitInner Si Tracker: B=0.7 Tesla, L=1m, nLayer=6, σx=0.010 mm

σ P

P=

σ x ⋅P0.3 ⋅B ⋅L2

720

nLayer + 4= 0.0004 ⋅ p

σ PP

=σ x ⋅P

0.3 ⋅B ⋅L2

256

nLayer= 0.0003 ⋅ p

Circle − Fit :σ PP

= 0.00032 ⋅ p

14

Inner Si Tracker Upper SciFi TrackerUpper SciFi Tracker

Angle-Point - MeasurementInner Si Tracker: B=0.7 Tesla, Lin =1.0 m, nLayer=4, σin=0.010 mmUpper SciFi-Tracker: Lup=1.2 m, nLayer=4, σup=0.050 mm

σ P

P=

2 ⋅P0.3 ⋅Lin ⋅B

σ up2 Lin

2 + σ in2 (Lin + Lup )

2 + σ in2 Lup

2

Lup2 Lin

2= 0.00024 ⋅P

15

Inner Si Tracker Upper SciFi TrackerUpper SciFi Tracker

Angle-Angle - MeasurementInner Si Tracker: B=0.7 Tesla, Lin =1.0 m, nLayer=4, σin =0.010 mmUpper SciFi-Tracker: Lup =1.2 m, nLayer=4, σout=0.050 mmLower SciFi-Tracker: Ldown=1.2 m, nLayer=4, σout=0.050 mm

σ P

P=

P

0.3 ⋅Lin ⋅B

(σ out2 + σ in

2 )(Lup2 + Ldown

2 )

Lup2 Ldown

2= 0.00014 ⋅P

16

Track-Fit Performance at P=100 GeV

17

No correlation visible for Circle-Fit and Angle-Point measurement=> take the weighted mean

PEBS: σ P

P=0.00020 ⋅P

AMS-2:σ P

P=0.00045 ⋅P

18

PEBS:

(Circle-Fit,Angle-Point) σ P

P=0.00020 ⋅P

Angle-Angleσ P

P=0.00014 ⋅P

AMS-2:σ P

P=0.00045 ⋅P

19

Magnet Top View, center of the coils

20

Magnet Side View, center of the coils

Coil Coil

21

Z=2.2m

L=1m

σ P

P=

σ 2

Z

Z − L⊕σ 3 ⊕σ 1

L

Z − L

0.3 BL232 + BL12 ⋅L − BL12

2 L

Z − L

⋅P = 0.00023⋅P

BL232 = B(z ')dz '

z2

z

∫⎡

⎣⎢⎢

⎤

⎦⎥⎥dz

z2

z3

∫ BL122 = B(z ')dz '

z1

z

∫⎡

⎣⎢⎢

⎤

⎦⎥⎥dz

z1

z2

∫ BL12 = B(z)dzz1

z2

∫

z [m]

z1z2z3

22

23

24

25

26

27

28

29

Electron-Efficiency 70%

30

Proton Rejection: Ecal 103, E/P=10 + TRD

PEBS - RICH

Physic-Programm:• Positron/Electron – Spectrum up to 200 GeV• He3/He4 for 1 GeV/n <= E/n <= 100 GeV/n• Be10/Be9 for 1 GeV/n <= E/n <= 100 GeV/n

Weight Budget for RICH 600 kgTRD 1

TRD 2

GasRICH

AerogelRICH

32

σ P

P= 0.00020 ⋅P

TRD 1

TRD 2

U-TRD

SRDPEBS - SRD

Physic-Programm:• Positron – Spectrum 1 GeV - 1500 GeV• Electron – Spectrum 1 GeV – 3000 GeV

U-TRD: 12 Layer upper TRDProton Rejection 36 Layer TRD5 104 @ 500 GeV Electron Efficiency 70%Weight 50 kg

Weight Budget for SRD (green) 400 kgSRD Acceptance 100,000 cm2 sr

34

35