1. The problem: The latest theoretical and experimental results suggest investigating a physics domain for p t higher than the actual one covered by the HMPID detector in the ALICE experiment (1 - 5 GeV/c) [1]. Goals of the new Cherenkov detector : ID of charged hadrons with p t  10 GeV/c. Inclusive measurement, particle yields, (anti)protons play a very important role in HI Physics. Weak identification, i.e. ,  - protons can be enough, since observables like anti-p / p, mesons/baryons are very sensitive to QGP Physics. Requirements: Compactness, it must fit in the present ALICE layout. Space constrains are the most strict requirement. The fact of use a gas radiator (high p t ) and the barrel geometry makes the use of a classical RICH difficult. Operation in a B-field up to 0.5T. Environment: High charged particle multiplicity, up to dN CH / dy = 8000 (100/m 2 (CC), Alice design parameters). Low interaction rates: from 8kHz (Pb-Pb) up to 300 kHz (p-p). R&D ON A DETECTOR FOR VERY HIGH MOMENTUM CHARGED HADRON IDENTIFICATION IN ALICE CENTRO DI CULTURA SCIENTIFICA A.VOLTA, VILLA OLMO (COMO-ITALY ) International Conference on Advanced Technology and Particle Physics Abraham Gallas INFN, Sez. Bari On behalf of the ALICE/HMPID group. References: [1] See for instance C. A. Salgado, I. Tserruya, B. Mueller talks in Quark Matter 2005, Budapest. [2] A. Braem et al., Nuclear Instruments and Methods A 409, 426-431 (1998). [3] Alice Collaboration, HMPID TDR, CERN/LHCC 98-19. F. Piuz et al., Nuclear Instruments and Methods A 433, 222 (1999) [4] M. Danilov et al., Nuclear Instruments and Methods A 515 202-219 (2003). ALICE EXPERIMENT 2 m HMPID Available space Conclusions & Outlook The PID capability of ALICE can be extended up to 30 GeV/c making use of available technologies at reasonable cost and time. Simulation studies are underway in order to optimize the detector layout. Laboratory tests are being scheduled to investigate the ageing of the MWPC and the CsI in presence of CF 4 Scintillation in CF 4 is being simulated, to clarify if the setup with the MWPC / GEM coated with CsI is feasible. Other options, like solid state photon detectors and aerogel as one of the radiators are being studied as a backup for the presented layout. ~ 1 m A possible solution: A Threshold imaging Cherenkov TIC as already used in NA44 [2]: Two gas radiators (CF 4, C 4 F 10 ) (UV region), to match the momentum range, separated by a CaF 2 window. Two photon detectors on the sides of the gas vessel measure the UV Cherenkov photons reflected by the central mirrors. A third tracking detector placed after the mirrors could improve the positioning of the track of the charged particle. Radiator: CF 4 and C 4 F 10 [8]: PID PERFORMANCE A MWPC with segmented cathodes coated with CsI, like the one used in the HMPID detector @ ALICE [3]. This time operated in pure CF 4 at atmospheric pressure. Although a rapid aging of proportio- nal counters operated with CF 4 has been observed [4], owing to this geo metry, wire material and collected charge ( ~ 0.8 mC/m, ~ 30 ALICE years) we do not expect aging e- ffects [5]. Still, stable operation of the chamber has to be proven. CF 4 transparent to 110 nm ~ 25 for C 4 F 10, ~ 30 for CF 4 (50 cm). Photon detector : Townsend avalanche photosensitive CsI layer (300 nm) Cherenkov photon CF 4 In order to achieve a good transparency of CF 4 and C 4 F 10 to UV photons we need a clean gas system, H 2 O and O 2 less than few ppm. This is critical for the CF 4 since this gas is in contact with the CsI, that has a large hygroscopicity. Another possibility is to use a GEM (Gas Electron Multiplier) with a CsI photocathode deposited in the first GEM in a cascade [6]. It can be ope- rated in a stable mode in pure CF 4 [7], so we can get rid of the window. Acceptable degradation of the CsI layer was observed for a total ion- back flow charge of ~ 7 mC/cm 2 [7]. [5] J.Wise et al., J. Appl. Phys. 74 No 9 5327-5340 (1993). [6] Thomas Meinschad et al., Nuclear Instruments and Methods A 535, 324-329 (2004). [7] A. Kozlov et al., Nuclear Instruments and Methods A 523 345-354 (2004). [8] Data from K. Zeitelhack et al., Nuclear Instruments and Methods A 433 201-206 (1999). AerogelC 4 F 10 CF 4 n1.011.00141.0005  c (  = 1) 8º8º 3º3º1.8º P  th (GeV/c)12.64.4 P K th (GeV/c)3.59.315.7 P proton th (GeV/c) 717.731.8 Momentum (GeV/c) AerogelC 4 F 10 CF 4 1 < p < 3100  3 < p < 3.5110  3.5 < p < 5110  100K 5 < p < 7111  100K 7 < p < 9100K 100proton 9 < p < 16110K 100proton 16 < p < 30111 , K 110proton We could replace one of the gas radiators by an aerogel or add it. In this case we would use solid state photon detectors in the visible, getting rid of the scintillation problem in the CF 4 gas radiator. Since the maximum Cherenkov angles for C 4 F 10 and CF 4 are very similar, the Cherenkov photons produced in both Radiators will be close in the photon detector. A third de- tector after the mirrors could improve the positioning of the particle track, helping in identifying the origin of the Cherenkov photons. We are as well considering the possibility of using a solid state photon detector. In this case we could move from the UV range to the visible. Some R&D needs to be done in order to operate those photon detectors inside the magnetic field (0.5 T) of the ALICE experiment. NA44 TIC Layout: