P. Govoni

Design and performance of the cooling system for the electromagnetic calorimeter of CMS

For the physics program of the CMS experiment at the LHC to be carried out successfully, excellent electromagnetic calorimetry is required. Given the thermal properties of CMS ECAL, keeping the constant term of the energy resolution below 0.5% needs its temperature to be stabilized at 18/spl deg/C within 0.05/spl deg/C. A prototype module of ECAL with the final cooling system has been tested at CERN to check its integration with the read-out electronics and verify that it complies with the severe thermal requirements. The thermal performance of the cooling system is reported here.

Inter-calibration of the CMS electromagnetic calorimeter with isolated electrons

The CMS electromagnetic crystal calorimeter (ECAL) must be precisely inter-calibrated if its full potential performance is to be realized. In this note, a detailed Monte Carlo study of in situ inter-calibration of the ECAL crystals using isolated electrons is described. The achievable precision depends on the quality and number of available electrons per crystal. This in turn depends upon the position of the crystals and the corresponding thickness of material in front of the ECAL.

Micro-channel plates in ionization mode as a fast timing device for future hadron colliders

At the high luminosity LHC (HL-LHC) about 200 concurrent interactions are expected, with a spread between the interaction vertices of few centimeters in the beam direction and 200 ps in the collision time. A time of flight resolution of the order of 30 ps would be able to reduce neutral particles pile-up contamination at the calorimeter level of about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates have been used in PMT configuration as fast charged particles detector (resolution of better than 20 ps have been achieved with commercial devices), however they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more then 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This open the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology.

High-energy electron test results of a calorimeter prototype based on CeF3 for HL-LHC applications

The High-Luminosity phase of the Large Hadron Collider at CERN (HL-LHC) poses stringent requirements on calorimeter performance in terms of resolution, pileup resilience and radiation hardness. A tungsten-CeF3 sampling calorimeter is a possible option for the upgrade of current detectors. A prototype, read out with different types of wavelength-shifting fibers, has been built and exposed to high energy electrons, representative for the particle energy spectrum at HL-LHC, at the CERN SPS H4 beam line. This paper shows the performance of the prototype, mainly focussing on energy resolution and uniformity. A detailed simulation has been also developed in order to compare with data and to extrapolate to different configurations to be tested in future beam tests. Additional studies on the calorimeter and the R&D projects ongoing on the various components of the experimental setup will be also discussed.