Cherenkov detectors in the ALICE experiment at LHC

Abstract

The ALICE experiment is devoted to measure the properties of the strongly interacting matter created in heavy-ion collisions at LHC at . The ALICE-HMPID is a ring imaging Cherenkov detector with liquid C6F14 as radiator, dedicated to the identification of charged pions and kaons in the range 1≤p≤3 GeV/c and protons in the range 2≤p≤5 GeV/c. It consists of seven identical proximity focusing RICH counters, exploiting large area MWPC equipped with CsI photocathodes, for Cherenkov light imaging. Furthermore, results from experiments at RHIC and theoretical studies have shown that to understand the hadronization mechanisms in heavy-ion collisions is very important to identify track-by-track charged hadrons at larger momenta (10−30 GeV/c). Therefore an upgrade of ALICE PID capability is advisable. A possible upgrade is under study and it consists of a ring imaging Cherenkov detector, called VHMPID. HMPID characteristics and results from cosmic and first beam data taking are described. Description of VHMPID and performance results from simulation are also reported.

Full text

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11th Topical Seminar on Innovative Particle and Radiation Detectors
(IPRD08) 1 - 4 October 2008, Siena, Italy
Cherenkov detectors in the ALICE experiment
Cherenkov detectors in the ALICE experiment
at LHC
at LHC
Giacomo Volpea,b
for
ALICE-HMPID group and VHMPID protocollaboration
aINFN, Sezione di Bari, Italy.
b Dipartimento Interateneo di Fisica “M. Merlin”, Bari, Italy.

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pioni
L3 Magnet
B=0.2-0.5 T
HMPID
RICH , PID @ high pT
ITS
Vertexing, low pt tracking
and PID with dE/dx
TPC
Main Tracking,
PID with dE/dx
TRD
Electron ID,
Tracking
TOF
PID @ intermediate pT
PHOS
γ,π0 -ID
MUON
µ-ID
+
T0,V0, PMD,FMD and ZDC
Forward rapidity region
High energy γ
ALICE is designed to study the physics of
strongly interacting matter and the quark-
gluon plasma (QGP) in nucleus-nucleus
collisions (√sNN = 5.5 TeV) at the LHC. The
p-p physics will be study as well as
reference data for the nucleus-nucleus
analysis.
EMCal
ACORDE
cosmic trigger
IPRD08, 3 October 2008 G. Volpe
ALICE experiment

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HMPID detector description
cos
cosθ θ θ θc c = 1/n
= 1/nβ β β β
• ALICE-HMPID (High Momentum Charged Particle Identification Detector)
performs charged particle track-by-track identification by means of emission
Cherenkov angle measurement and of the momentum information provided by the
tracking devices.
• It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov)
counters
radiatorPhoton detector
• HMPID is the only Cherenkov detector in the ALICE apparatus;
• Physics goals: particle ratios, HBT interferometry, meson production;
mip
charged particle

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HMPID detector description
The largest scale (11 m2) application of CsI
photo-cathodes in HE/HI-P!
IPRD08, 3 October 2008 G. Volpe
PID RANGE
- 1<p<3 GeV/c π-k
- 2<p<5 GeV/c p
RADIATOR
15 mm liquid C6F14,
n ~ 1.2989 @ 175nm, βth = 1.21
PHOTON CONVERTER
Reflective layer of CsI
QE ~ 25% @ 175 nm.
PHOTOELECTRON DETECTOR
- MWPC with CH4 at atmospheric
pressure (4 mm gap) HV = 2050 V.
- Analogue pad readout

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HMPID detector description
CsI photo-cathode is
segmented in
0.8x0.84 cm pads
Six photo-cathodes per
module
IPRD08, 3 October 2008 G. Volpe