Transcript RICH - CEA-Irfu

Physics motivations
Status of the project
Future Plans
Patrizia Rossi for the RICH
Collaboration
Laboratori Nazionali di Frascati- INFN (Italy)
CLAS12 2nd European Workshop - March 7-11, 2011- Paris, France
CLAS12 Physics Program
Study of the internal nucleon dynamics:
TMD distribution and fragmentation functions & GPDs
Hadron PID to achieve flavor tagging
Quark hadronization in the nuclear medium
Hadron PID to strongly constrain the models
Spectroscopy
Hadron PID to access rare processes
This program requires good identification of p 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 PID
LHCb (MC prediction)
NO RICH
With RICH
Need to distinguish Bd pp from other similar topology 2-body
decays and to distinguish B from anti-B using K tag.
CLAS12 PID
GeV/c 1
p/K
p/p
K/p
e/p
2
TOF
TOF
TOF
HTCC
full pion / kaon / proton separation
over whole accessible momentum
range of 2 – 8 GeV for SIDIS exp.
3
4
5
6
LTCC
RICH
LTCC
LTCC
RICH
7
8
9
10
HTCC
HTCC
HTCC
LTCC
RICH
LTCC
EC/PCAL
SIDIS
kinematics
p/K separation of 4-5 s @ 8 GeV/c for a rejection factor ~1000
Concept of a RICH for CLAS12
Projective geometry:
 6 radial sectors

1.2 m gap

~ 3 m radius
B ~ 40 G
25o
RICH for CLAS12
2 mrad
RADIATOR
8 mrad
Freon+UV-light detection does not provide enough discrimination power in the 28 GeV/c momentum range
Aerogel mandatory to separate hadrons in the 2-8 GeV/c momentum
range  collection of visible Cherenkov light  use of PMTs
RICH for CLAS12
Challenging project:
 Large Detector area (several m2)
 Operation in magnetic field &
with high intensity e- beam
Innovative new technologies
 Radiator Material
 Photo-detectors
 Electronics
~ 6 m2
entrance window
From a proximity focusing to an “hybrid” RICH
1m
depth
RICH for CLAS12: status and plans
MC Simulation for basic parameters studies ✔
(stand-alone GEANT-3 based code)
- Aerogel refractive index and thickness
- Photon detector pixel size
- Gap dimension
s

CK
sp
Cp
Fix the pixel size of PMTs
< 1cm
5
8 5
85
85
85
8
RICH for CLAS12: status and plans
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
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 summer
Transparent Silica Aerogel with High n
Makoto Tabata, Ichiro Adachi et al. for Belle II aerogel RICH group
–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
70
transmission length
@400nm [mm]
New production technique
invented for high refractive
index greater than 1.05
conventional
PD
60
50
40
30
20
10
0
1.00
1.05
1.10
1.15
1.20
refractive index @405nm
Some new developments also in Novosibirsk
First 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]
1.25
1.30
GEMC 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 System
Low
material
budget
Direct &
reflected
photons
Goals:
• instrument only forward region
• reduce active area (~1 m2/sect)
• minimize interference with TOF system
• allow larger aerogel thickness (focalization)
The focusing Mirror System
• spherical (elliptical) mirror within gap volume for backward refl.
• plane mirror just beyond radiator for forward reflections
Minimize
TOF
detector area (~1 m2/sector)
interference with FTOF
Reflecting
inside
Low material
budget
direct &
reflected
Preliminary studies with mirrors (to reduce instrumented area):
- focalization capabilities shown
- ring patterns for positive and negative mesons at different angles and momenta reconstructed
Different scenarios (refractive index, radiator thickness, mirror geometry) are being
explored
The reconstruction algorithm: Direct Ray Tracing (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.
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 a hit given the kinematics of track t and hypothesis h
is the probability of no hit
is the total number of expected PMT hits
is a background term
Hypothesis that maximizes
is assumed to be true
200 trials per event
Aerogel:
- n=1.06
- thickness increasing
with radius:
Direct ring example
M. Contalbrigo INFN/FE
Hit prob > 3 10-3
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
PPMT (i)
Average
Np.e.
p+
p-
5
°
Np.e. > 5 for reflected rings
Np.e.> 12 for direct rings
LHp-LHK,p
p+
p-
Contamination
as expected
from the
GEANT3
simulation!
Very promising
results also for
the reflected
events
5
°
Average
Np.e.
p+
p-
Mirror 14°-25°
Mirror up to 35o:
Viable configuration
LHp-LH
K,p
- Mirror 14o-25o
n=1.06
Aer. thick 2-4-6-8-10 cm
p+
n=1.03
Aer. thick 3-6-9-12-15 cm
p-
p+
p-
n=1.03 in principle good due to the larger Cherenkov angle separation
Average
Np.e.
p+
p-
n=1.06 better
for patter
recognition in
the presence
of backgrouns
n=1.06
Jo
Average
Np.e.
p+
p-
Jo
Photo-detectors
REQUESTS:
visible light
compact
single
photon
Small pad
size
 Multi-anode PMTs
 SiPM
MA-PMT
Dimentional
outline (mm3)
Effective area (mm2)
Pixel size
(mm2)
Comment
R7600
26x26x28
18x18
4.5x4.5 (4x4)
Optimized for single photon
Recommended by Hamam
Low packing factor
H8500-C
52x52x28
49x49
5.8x5.8 (8x8)
Excellent packing factor
Not optimized for single photon
Not recommended by H.
H8500-C-03
R8900-00-M16
UV glass window
25x25x28
20x20
4.8x4.8 (4x4)
R8900-100-M16
R11265
Optimized for single photon
High packing factor
Sensitive to B
Super bialkali
23x23
2.8x2.8 (8x8)
Optimized for single photon
High packing factor
Insensitive to B
Available only 8x8
- Preliminary tests results with H8500 and R7600 at Glasgow U.
- R8900 will be tested soon
Front-end & Readout Electronics
Front-end & readout board developed by INFN-Genova group (frontend chip MAROC from IN2P3-Orsay)
A.G. Argentieri et al. NIM A 617 (2010) 348–350
• Independent channels
(unique!) with selectable
gain for non-uniformity
compensation
• Smart (reconfigurable) selftriggering by active FPGA
(trigger topology scheme)
• Up to 4096 channels in
compact form factor
• Fast Readout
• Compact (high density of the
front end)
Players in the Game
INSTITUTIONS
Researchers
ARGONNE NL
INFN
Bari, Ferrara, Genova,
Frascati, Roma/ISS
GLASGOW U.
JLAB
U. CONN
3
13
UTFSM (Chile)
3
2
2
3
NEW COLLABORATORS, CONTRIBUTIONS ($, €..),
MANPOWER, ARE VERY WELCOME TO JOIN THIS
EXCTING PROJECT
Conclusions
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