Patrizia Rossi for the RICH Collaboration

Laboratori Nazionali di Frascati- INFN (Italy)

Physics motivations

Status of the project

Future Plans

CLAS12 2nd European Workshop - March 7-11, 2011- Paris, France

CLAS12 Physics ProgramCLAS12 Physics Program

Hadron PID to achieve flavor tagging

Hadron PID to strongly constrain the models

Hadron PID to access rare processes

Study of the internal nucleon dynamics: Study of the internal nucleon dynamics: TMD distribution and fragmentation functions & TMD distribution and fragmentation functions & GPDsGPDs

Quark hadronization in the nuclear mediumQuark hadronization in the nuclear medium

SpectroscopySpectroscopy

This program requires good identification of and K over the full kinematical range accessible with CLAS12 Particle identification is an essential part of any experiment, and has contributed substantially to our present understanding of elementary particles and their interaction

The power of a good PIDThe power of a good PID

Need to distinguish Bd from other similar topology 2-body decays and to distinguish B from anti-B using K tag.

LHCb (MC prediction)

NO RICH With RICH

CLAS12 PIDCLAS12 PID

RICH

SIDIS kinematics

full pion / kaon / proton separation over whole accessible momentum range of 2 – 8 GeV for SIDIS exp.

/K separation of 4-5 @ 8 GeV/c for a rejection factor ~1000

GeV/c 1 2 3 4 5 6 7 8 9 10

/K

/p

K/p

e/

HTCC

TOF

TOF

TOF

HTCC

HTCC

HTCCEC/PCAL

RIC

HRIC

H

LTCC

LTCCRICH

LTCCLTCCRICH

LTCCRICH

Concept of a RICH for CLAS12Concept of a RICH for CLAS12

Projective geometry: 6 radial sectors

1.2 m gap

~ 3 m radius

25o

FT

OF

wall

DC

3TOR

US

538 cm

124 cm

B ~ 40 G

RA

DIA

TO

R

RIC

8 mrad

2 mrad

Aerogel mandatory to separate hadrons in the 2-8 GeV/c momentum range collection of visible Cherenkov light use of PMTs

Freon+UV-light detection does not provide enough discrimination power in the 2-8 GeV/c momentum range

RICH

RICH for CLAS12RICH for CLAS12

RICH for CLAS12RICH for CLAS12

RIC

RIC

RIC

Large Detector area (several m2)

Operation in magnetic field & with high intensity e- beam

Challenging project:

Innovative new technologies Radiator Material Photo-detectors Electronics

RIC

~ 6 m2

entrance window

1 m depth

From a proximity focusing to an “hybrid” RICH

5 8 5 8 5 8 5 8 5 8

CC

K

RICH for CLAS12: status and plansRICH for CLAS12: status and plansMC Simulation for basic parameters studies ✔ (stand-alone GEANT-3 based code)- Aerogel refractive index and thickness - Photon detector pixel size - Gap dimension

Fix the pixel size of PMTs< 1cm

5 8 5 8 5 8 5 8 5 8

RICH for CLAS12: status and plansRICH for CLAS12: status and plans

MC Simulation with RICH geometry included into the CLAS12 GEMC package (Geant4/C++ based code)- focussing mirrors option studies in progress- Development of the reconstruction tracking algorithm of charged particles in progress Front-end & Readout Electonics- Available readout system to be customized for CLAS12 - Test of the modified system in CLAS12 conditions - Production of the needed boards- Quality checks/characterization

Preparation of a Conceptual Design Report by this Preparation of a Conceptual Design Report by this summersummer

MC Simulation for basic parameters studies ✔ (stand-alone GEANT-3 based code)- Aerogel refractive index and thickness - Photon detector pixel size - Gap dimension

Validation of simulations and check performances: RICH prototype construction- Procurements of parts done ✔- Tests of the radiators and the photo-detectors at Frascati – setup installation started- Prototype beam tests

Committed by UTFSM (Chile)

Transparent Silica Aerogel with High nTransparent Silica Aerogel with High n

0

10

20

30

40

50

60

70

1.00 1.05 1.10 1.15 1.20 1.25 1.30

refractive index @405nm

transmission length

@400nm [mm]

conventionalPD

New production technique invented for high

refractive index greater than 1.05

–Optical quality degraded if sample with n>1.05 is produced in a conventional method –“Pinhole drying (PD)” method artificially shrinks alcogel to obtain high index–Transparency doubled for n>1.05 aerogel with this new method

Makoto Tabata, Ichiro Adachi et al. for Belle II aerogel RICH group

Some new developments also in NovosibirskFirst use of high refractive index aerogel (n=1.13) in particle physics experiment [A.Yu.Barnyakov et.al., Nucl.Instr. and Meth. A 598 (2009) 163]

GEMC SimulationsGEMC Simulations

GEANT4 toolkit:Toward a complete simulation: realistic geometry / detailed optic effects track multiplicity / background full Cherenkov ring simulation chain

Ongoing activities: Improve simulation

Reduce costs mirrors

The focusing Mirror SystemThe focusing Mirror System

Goals: • instrument only forward region • reduce active area (~1 m2/sect)• minimize interference with TOF system• allow larger aerogel thickness (focalization)

Low material budget

Direct & reflected photons

The focusing Mirror SystemThe focusing Mirror System

Preliminary studies with mirrors (to reduce instrumented area): - focalization capabilities shown - ring patterns for positive and negative mesons at different angles and momenta reconstructed

• spherical (elliptical) mirror within gap volume for backward refl.

• plane mirror just beyond radiator for forward reflections

Different scenarios (refractive index, radiator thickness, mirror geometry) are being explored

TOF

Reflectinginside

direct &reflected

Low materialbudget

Minimize detector area (~1 m2/sector) interference with FTOF

The reconstruction algorithm: Direct Ray Tracing The reconstruction algorithm: Direct Ray Tracing (DRT)(DRT)

For each track, t, and particle hypothesis, h, use direct ray tracing for a large number of generated photons to determine the hit probability for each PMT

The measured hit pattern is compared to the hit probability densities for the different hypotheses by a likelihood function.

Hypothesis that maximizes is assumed to be true

is the probability of a hit given the kinematics of track t and hypothesis h

is the hit pattern from data = 1 if the ith PMT is hit= 0 if the ith PMT is not hit

is the probability of no hit

is the total number of expected PMT hits is a background term

ANL+INFN/FE

Direct ring exampleDirect ring example

Hit prob > 3 10-3

200 trials per event

Aerogel: - n=1.06 - thickness increasing with radius: 2 cm  up to 13 deg 4 cm  13-15 deg 6 cm  15-17 deg 8 cm  17-20 deg 10 cm > 20 deg

Mirror: 14o-25o

PMTs: UBA

M. Contalbrigo INFN/FE

PPMT (i)

Average Average NNp.e.p.e.

Np.e. > 5 for reflected ringsNp.e.> 12 for direct rings

+ -

5°

LHLH-LH-LHK,pK,p+ -

Contamination as expected from the GEANT3 simulation!

Very promising results also for the reflected events

Contamination as expected from the GEANT3 simulation!

Very promising results also for the reflected events

5°

Average Average NNp.e.p.e.

Mirror up to 35o:Viable configurationMirror up to 35o:Viable configuration

+ -

Mirror 14°-25°

LHLHpp-LH -LH K,pK,p - Mirror 14 - Mirror 14oo-25-25oo

n=1.03 in principle good due to the larger Cherenkov angle separationn=1.03 in principle good due to the larger Cherenkov angle separation

n=1.06Aer. thick 2-4-6-8-10 cm

n=1.03Aer. thick 3-6-9-12-15 cm

+ - + -

n=1.06 better for patter recognition in the presenceof backgrouns

n=1.06 better for patter recognition in the presenceof backgrouns

Average Average NNp.e.p.e.

oo

+ -

n=1.06

Average Average NNp.e.p.e.

oo

+ -

Photo-detectorsPhoto-detectors

Multi-anode PMTsSiPM

visible light compact single photon

Small pad size

REQUESTS:

MA-PMT Dimentional outline (mm3)

Effective area (mm2)

Pixel size (mm2)

Comment

R7600 26x26x28 18x18 4.5x4.5 (4x4) Optimized for single photonRecommended by HamamLow packing factor

H8500-C 52x52x28 49x49 5.8x5.8 (8x8) Excellent packing factorNot optimized for single photonNot recommended by H.

H8500-C-03 UV glass window

R8900-00-M16

25x25x28 20x20 4.8x4.8 (4x4) Optimized for single photonHigh packing factorSensitive to B

R8900-100-M16

Super bialkali

R11265 23x23 2.8x2.8 (8x8) Optimized for single photonHigh packing factorInsensitive to BAvailable only 8x8 - Preliminary tests results with H8500 and R7600 at Glasgow U.

- R8900 will be tested soon

Front-end & Readout ElectronicsFront-end & Readout Electronics

• Independent channels (unique!) with selectable gain for non-uniformity compensation

• Smart (reconfigurable) self-triggering by active FPGA (trigger topology scheme)

• Up to 4096 channels in compact form factor

• Fast Readout

• Compact (high density of the front end)

Front-end & readout board developed by INFN-Genova group (front-end chip MAROC from IN2P3-Orsay)

A.G. Argentieri et al. NIM A 617 (2010) 348–350

Players in the GamePlayers in the GameINSTITUTIONS Researchers

ARGONNE NL 3

INFNBari, Ferrara, Genova, Frascati, Roma/ISS

13

GLASGOW U. 2

JLAB 2

U. CONN 3

UTFSM (Chile) 3NEW COLLABORATORS, CONTRIBUTIONS ($,

€..), MANPOWER, ARE VERY WELCOME TO JOIN THIS EXCTING PROJECT

ConclusionsConclusions

Good hadron identification is required for studies of the internal nucleon dynamics

RICH technique is the clear choice when hadron identification is required at high momenta

Preliminary studies show that aerogel plus visible light detection with MA-PMT can match the requirements for a RICH for CLAS12.

Work is in progress to:- Improve simulation and reconstruction algorithm - Define a CDR by this summer- validate simulations and check performances by testing components and building a prototype

Initial R&D funding available from INFN and ANL