Stato e Sviluppi del sistema RICH di LHCb

Stato e Sviluppi del sistema RICH di LHCb

Tito Bellunato

XV IFAE - Lecce – 25 Aprile 2003

Outline of the Talk

• LHCb - a brief introduction

• RICH detectors overview

• Latest developments

• COMPASS RICH

Momentum

Particle Identification

1 < p < 150 GeV/c RICH1

RICH2

2 detectors with 3 radiators

aerogel

C4F10

CF4

b-Physics with Particle Identification B

K

K

Purity=13% Purity=84%

Efficiency=79%

No RICH With RICH











 ⋅ +

 =

 

 ⋅

=

 

= 

p m p

n p

E n

C n

2

1 2

arccos arccos 1

arccos 1 θ β

β θ σθ

β

σ = tan ⋅

With N detected photons

. .

. .

e p

e p

N

θ σθ

σ ≈

→ minimize σ_θ

→ maximize N_p.e.

n = 1.28 C₆F₁₄ liquid

n = 1.0018 C₅F₁₂ gas

Cherenkov radiator selection

go visible (LHCb)

go invisible (COMPASS)

p.e.

radiator CF₄ n (600 nm) 1.0005 p_threshold (π) 4.4 GeV/c N_p.e. 24

σ_θ 0.58 mrad p (3 σ) 100 GeV/c

RICH 1 RICH 2

radiator C₄F₁₀ Aerogel n (600 nm) 1.0014 1.03

p_threshold (π) 2.6 0.6 GeV/c N_p.e. 32.7 6.6

σ_θ 1.45 2 mrad p (3σ) 50 10 GeV/c

RICH layout

Flat mirror

PD plane

RICH 1 Redesign is in a well advanced status

Fraction of X0 from 14 % (TDR) to 8.5 %

RICH 2 RICH-2 Engineering Design Review

for the superstructure and mirrors completed:

Spherical mirrors ordered.

Prototype mirror mount and support panel

Stability of optical system to within 0.1 mrad

Baseline: Pixel-HPD, developed by CERN/ DEP(NL) cross-focused, 80mm Ø, encapsulated readout electronics 1024 pixels (500 µm x 500 µm), demagnification D = 5.

S20photocathode:

72 mm Ø active

The LHCb RICH photodetector

0 10 20 30

150 250 350 450 550 650

? ^(nm)

qe (%)

Quantum efficiency Requirements:

2.6 m² coverage with 75% active area 2.5 x 2.5 mm² granularity

Single photon efficiency 40 MHz readout

Photon detectors

HPD R&D 40 MHz pixel chip J photocathode J tube encapsulation J initial performance J

but… long term stability L due to the bump bonding quality

> 99.9% pixels responding with good S/N

bump-bonds original state after two bake-out cycles 20 µm

Backup Photon Detector: Hamamatsu MAPMT

- Final decision by September - Clear road map defined

11 signal channels latency coarsely

optimised

8-stage 64 pixel MaPMT readout by Beetle 1.2

quartz lenses

3x3 cluster in testbeam 3x3 cluster in testbeam

Aerogel as Cherenkov Radiator

Rayleigh scattering

linked network of SiO2 particles density = 0.15 g/cm

hygroscopic or hydrophobic

3

The Testbeam Setup

In the PS T7 area at CERN

In the simulation

program

10 10²

mm

mm

π run 30k events

9 GeV/c π

10 10 ²

mm

mm

6 to 10 GeV/c π / proton

The Beam

π/p 6 GeV/c 30k events

Particle Identification Performance

Mirror specifications

The uncertainty in the Cherenkov angle measurement must not be significantly affected by the precision of the optical system

σ

^{< ~1% R}

σ ^{θ ~} 0.15 mrad in RICH1 0.03 mrad in RICH2

For RICH1 material budget is particularly important:

low fraction of X

and λ

+ STABILITY

INFN Composite

CMA Composite Beryllium

Light Mirror Options

Mirror 1b R=1624mm D0=1.5mm

0 20 40 60 80 100

0 1 2 3 4 5

Diameter (mm)

% of collected light

Optical Quality

Figure of merit is D0 Defined as that diameter which contains 95% of the total reflected energy

Our aim is D0 < 2 mm

Laser point source

CCD camera

Mirror

Mechanical stability Optical

quality Fraction

of λ

Fraction of X0 Technology

? (B-field)

? 1.5 %

1.5 % Nickel

? (C4F10) X

0.5 %

PMMA + Nomex

~1%

+ C-fibre

X ?

(refl. ?) 0.5 %

C-fibre and ~1%

epoxy

X (X) X

(?) 1.6 %

(1.0 %) 1.8 %

(1.1 %) Be + glass

(thinner)

X X

1.2%

4.6 % 5 mm glass

Mirror options for RICH1

LHCb RICH - conclusions:

Project well on track and in good shape No loss in performance after re-designing

Decision on photon detector choice by September Light mirrors are a viable option

Optical system is well-defined and stable RICH2 EDR done and PRR next week

Spectrometer Magnet 1 +tracking

Spectrometer Magnet 2

RICH1

Polarised Target

Calorimetry-1

Calorimetry

Muon Wall Muon Wall

SPS 160 GeV µ beam

RICH2

COMPASS Current Setup

Nucleon Structure and Spectroscopy

COMPASS RICH-1 Parameters

Main requests from the experiment:

• π/K separation up to ~ 60 GeV/c

• Large angular acceptance:

±250mrad ±200mrad (V)

• Minimize materials Design:

• Radiator: C₄F₁₀, length: ~ 3m

• Mirrors:

• Spherical, focal length 3.3 m

• Reflectance > 80% for λ > 165nm

• Total surface

• Photon detectors:

MWPC’s with CsI photocathodes,

out of acceptance / total surface 5.3 m²

• Read-out electronics:

• Analog read-out/ 83 K channels

• average occupancy 5%

• max data rate 2.5 Gb/sec in spill Material Budget:

• Total 22.5% of X₀

• Mirrors 5.5%

• Radiator 10.5%

Photon detector (Up)

Photon detector (Down)

Photon Detectors

Basic Design from RD26

COMPASS RICH 2: Photon Detector Proposed Geometry

quartz lens quartz lens photocathode

photocathode PMPM

50 mm50 mm

30 mm30 mm

18 mm18 mm

1120 PM, 2.8 m²,

18000 digital channels

granularity: ~11 mm x 11 mm

fotone fotone

σ_{photon *} n^1/2 ~ cost

π/K sep. up to 120 GeV/c

MAPMT HAMAMATSU H6568-03 16 - channel with UV glass

COMPASS RICH - Conclusions:

RICH 1 is now fully operational

All photon detectors equipped

RICH 2 design in advanced status

Testbeam and prototyping started