Resistive Plate Chamber detectors are largely used in current High Energy Physics experiments, typically operated in avalanche mode with large fractions of Tetrafluoroethane (C2H2F4), a gas recently ...banned by the European Union due to its high Global Warming Potential (GWP). An intense R&D activity is ongoing to improve RPC technology in view of future HEP applications. In the last few years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to investigate the performance of present and future RPC generations with eco-friendly gas mixtures. Detectors with different layout and electronics have been operated with ecological gas mixtures, with and without irradiation at the CERN Gamma Irradiation Facility (GIF++). Results of these performance studies together with plans for an aging test campaign are discussed in this article.
The first evidence of spin alignment of vector mesons ( K*0 and ϕ ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at ...midrapidity ( | y | < 0.5 ) in Pb-Pb collisions at a center-of-mass energy ( √sNN ) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ( p T < 2 GeV / c ) for K*0 and ϕ at a level of 3 σ and 2 σ , respectively. No significant spin alignment is observed for the K0S meson ( spin = 0 ) in Pb-Pb collisions and for the vector mesons in p p collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.
The ALICE Collaboration at the CERN-LHC has started a vast program of upgrades in the context of the increase of the luminosity of the LHC from 2018 on. The present very front-end electronics (VFE) ...of the Muon Trigger, whose acronym is ADULT, must be replaced to prevent the aging of the Resistive Plate Chamber (RPC) detector in the future expected operating conditions. The new VFE, FEERIC (Front-End Electronics Rapid Integrated Circuit), will have to perform amplification of the analog input signal (this is not the case for ADULT). This will allow for RPC operation in a low-gain avalanche mode, with a much smaller (factor 3-5) charge deposit in the detector with respect to the present conditions. The purpose is to discriminate RPC signals with a charge threshold around 100 fC, in both polarities. The VFE system consists of 21,000 channels, distributed over 2400 electronics cards equipped with one or two ASICs. A total of 3000 ASICs of 8 channels each is necessary. The future ASIC has to insure mainly the following functions: amplification, discrimination and LVDS output stage. FEERIC will be capable of handling bipolar signals varying from ±20 fC up to ±3 pC with a fixed threshold of typically 100 fC. A prototype chip has been designed using the 0.35 μm CMOS technology of AMS. The time resolution is less than 500 ps rms for an input charge of ±100 fC. The time resolution is 30 ps rms for an input charge of ±3 pC. The cross-talk is less than 2% for an input charge of ±3.5 pC and a threshold of ±20 mV (corresponding to ≈ 70 fC). The global power consumption per channel is 60 mW, with a 3 V power supply.
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