[en] CMS results are presented on the measurement of properties of the Higgs-like particle discovered last summer with a mass in the range of 125-126 GeV, based on the full statistics of about 25 fb^-1, collected in 2011 and 2012 at 7 and 8 TeV respectively. Five decay channels are considered for these studies, namely the ZZ, γγ, WW, ττ, and bb modes. The mass of the new boson is measured to be 125.7 ± 0.4 GeV. The event yields measured by the different analyses, targeting specific decay modes and production mechanisms, are consistent with those expected for the standard model (SM) Higgs boson, with an overall best-fit signal strength of 0.80 ± 0.14 at the measured mass. A discussion on the measurement of the couplings and the spin-parity properties of this new particle is presented, using the most recent results. (authors)

[en] During October-November 2008 the CMS Collaboration conducted a data-taking exercise in order to complete the commissioning of the experiment for extended operation. A large sample of cosmic ray triggered events has been recorded with the solenoid at its nominal axial field strength of 3.8 T. The events collected have been exploited to perform a measurement of specific energy loss of muons in lead tungstate - the electromagnetic calorimeter material - over a wide momentum range (from 5 GeV/c to 1 TeV/c). The results are consistent with the expectations over the entire range. A comparison of collision losses with radiative losses allowed for a first experimental determination of muon critical energy in lead tungstate, measured to be 160⁺⁵_-6 ± 8 GeV, in agreement with expectations.

[en] A large sample of cosmic ray events collected by the CMS detector has been exploited to measure the muon stopping power in the lead tungstate (PbWO₄) of the electromagnetic calorimeter. The events were recorded in October-November 2008, during commissioning runs of the CMS detector with the solenoid at the nominal field strength of 3.8 T. The measurement spans a momentum range from 5 to 1000 GeV/c. The results are consistent with the expectations over the entire range. A comparison of collision losses with radiative losses allowed for a first experimental determination of muon critical energy in lead tungstate, measured to be 160⁺⁵_-6 (stat.) ± 8 (syst.) GeV, in agreement with expectations.

[en] The electromagnetic calorimeter (ECAL) of the CMS experiment at the CERN Large Hadron Collider is a hermetic, fine grained, homogeneous calorimeter containing 75848 lead tungstate crystals, completed by a silicon preshower installed in front of the endcaps. The main characteristics of the ECAL are reviewed. These include the challenges of calibration and triggering in the LHC environment, as well as the reconstruction and identification of photons and electrons. Several results achieved by the CMS experiment particularly exploit the ECAL excellent performance, here illustrated with reference to specific examples, comprising the Higgs boson search and characterization in the H → γγ and H → ZZ⁽*⁾ decay channels and the search for non-standard phenomena such as high-mass gauge bosons decaying into electrons and long-lived particles with delayed signals in the calorimeter

[en] One of the main challenges for detectors at future high-energy collider experiments is the high precision measurement of hadron and jet energy and momentum. One possibility to achieve this is the dual-readout technique, which allows recording simultaneously scintillation and Cherenkov light in an active medium in order to extract the electromagnetic fraction of the total shower energy on an event- by-event basis. Making use of this approach in the high luminosity LHC, however, puts stringent requirements on the active materials in terms of radiation hardness. Consequently, the R and D carried out on suitable scintillating materials focuses on the detector performance as well as on radiation tolerance. Among the different scintillating materials under study, scintillating glasses can be a suitable solution due to their relatively simple and cost effective production. Recently a new type of inorganic scintillating glass: Cerium doped DSB has been developed by Radiation Instruments and New Components LLC in Minsk for oil logging industry. This material can be produced either in form of bulk or fiber shape with diameter 0.3-2mm and length up to 2000 mm. It is obtained by standard glass production technology at temperature 1400°C with successive thermal annealing treatment at relatively low temperature. The production of large quantities is relatively easy and the production costs are significantly lower compared to crystal fibers. Therefore, this material is considered as an alternative and complementary solution to crystal fibers in view of a production at industrial scale, as required for a large dual readout calorimeter. In this paper, the first results on optical, scintillation properties as well as the radiation damage behaviour obtained on different samples made with different raw materials and various cerium concentrations will be presented

[en] Particle detectors at future collider experiments will operate at high collision rates and thus will have to face high pile up and a harsh radiation environment. Precision timing capabilities can help in the reconstruction of physics events by mitigating pile up effects. In this context, radiation tolerant, scintillating crystals coupled to silicon photomultipliers (SiPMs) can provide a flexible and compact option for the implementation of a precision timing layer inside large particle detectors. In this paper, we compare the timing performance of aluminum garnet crystals (YAG: Ce, LuAG: Ce, GAGG: Ce) and the improvements of their time resolution by means of codoping with Mg²⁺ ions. The crystals were read out using SiPMs from Hamamatsu glued to the rear end of the scintillator and their timing performance was evaluated by measuring the coincidence time resolution (CTR) of 150 GeV charged pions traversing a pair of crystals. The influence of crystal properties, such as density, light yield and decay kinetics on the timing performance is discussed. The best single detector time resolutions are in the range of 23–30 ps (sigma) and only achieved by codoping the garnet crystals with divalent ions, such as ${\mathrm{Mg}}^{2+}$. The much faster scintillation decay in the co-doped samples as compared to non co-doped garnets explains the higher timing performance. Samples of LSO: Ce, Ca and LYSO:Ce crystals have also been used as reference time device and showed a time resolution at the level of 17 ps, in agreement with previous results.

[en] The progresses in the micropulling-down technique allow heavy scintillating crystals to be grown directly into a fibre geometry of variable shape, length and diameter. Examples of materials that can be grown with this technique are Lutetium Aluminum Garnets (LuAG, Lu₃Al₅O₁₂) and Yttrium Aluminum Garnets (YAG, Y₃Al₅O₁₂). Thanks to the flexibility of this approach, combined with the high density and good radiation hardness of the materials, such a technology represents a powerful tool for the development of future calorimeters. As an important proof of concept of the application of crystal fibres in future experiments, a small calorimeter prototype was built and tested on beam. A grooved brass absorber (dimensions 26cm×7cm×16cm) was instrumented with 64 LuAG fibres, 56 of which were doped with Cerium, while the remaining 8 were undoped. Each fibre was readout individually using 8 eightfold Silicon Photomultiplier arrays, thus providing a highly granular description of the shower development inside the module as well as good tracking capabilities. The module was tested at the Fermilab Test Beam Facility using electrons and pions in the 2–16 GeV energy range. The module performance as well as fibre characterization results from this beam test are presented.

[en] The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about 30 ps at the beginning of operation, and degrading to 50-60 ps at the end of the detector lifetime as a result of radiation damage. In this work, we present the results obtained using a 120 GeV proton beam at the Fermilab Test Beam Facility to measure the time resolution of unirradiated sensors. A proof-of-concept of the sensor layout proposed for the barrel region of the MTD, consisting of elongated crystal bars with dimensions of about 3×3×57 mm³ and with double-ended SiPM readout, is demonstrated. This design provides a robust time measurement independent of the impact point of the MIP along the crystal bar. We tested LYSO:Ce bars of different thickness (2, 3, 4 mm) with a geometry close to the reference design and coupled to SiPMs manufactured by Hamamatsu and Fondazione Bruno Kessler. The various aspects influencing the timing performance such as the crystal thickness, properties of the SiPMs (e.g. photon detection efficiency), and impact angle of the MIP are studied. A time resolution of about 28 ps is measured for MIPs crossing a 3 mm thick crystal bar, corresponding to a most probable value (MPV) of energy deposition of 2.6 MeV, and of 22 ps for the 4.2 MeV MPV energy deposition expected in the BTL, matching the detector performance target for unirradiated devices. (paper)

[en] Test beam results of a calorimetric module based on 3×3×22 cm³ PbWO₄ crystals, identical to those used in the CMS ECAL Endcaps, read out by a pair of photodetectors coupled to the two opposite sides (front and rear) of each crystal are presented. Nine crystals with different level of induced absorption, from 0 to 20 m⁻¹, have been tested using electrons in the 50–200 GeV energy range. Photomultiplier tubes have been chosen as photodetectors to allow for a precise measurement of highly damaged crystals. The information provided by this double side read-out configuration allows to correct for event-by-event fluctuations of the longitudinal development of electromagnetic showers. By strongly mitigating the effect of non-uniform light collection efficiency induced by radiation damage, the double side read-out technique significantly improves the energy resolution with respect to a single side read-out configuration. The non-linearity of the response arising in damaged crystals is also corrected by a double side read-out configuration and the response linearity of irradiated crystals is restored. In high radiation environments at future colliders, as it will be the case for detectors operating during the High Luminosity phase of the Large Hadron Collider, defects can be created inside the scintillator volume leading to a non-uniform response of the calorimetric cell. The double side read-out technique presented in this study provides a valuable way to improve the performance of calorimeters based on scintillators whose active volumes are characterized by high aspect ratio cells similar to those used in this study.