Arabella Martelli

We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers.

The High Luminosity phase of the Large Hadron Collider will deliver 10 times more integrated luminosity than the existing collider, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry. As part of its upgrade program, the Compact Muon Solenoid collaboration is designing a high-granularity calorimeter (HGCAL) to replace the existing endcap calorimeters. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. First hexagonal silicon modules, using the existing Skiroc2 front-end ASIC developed for CALICE, have been tested in beams at Fermilab and CERN in 2016. We present results from these tests, in terms of system stability, calibration with minimum-ionizing particles and resolution (energy, position and timing) for electrons, and the comparisons of these quantities with GEANT4-based simulation.

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with heavy absorber plates, and read out by wavelength-shifting (WLS) fibers is being studied as a calorimeter option for detectors at the upgraded High-Luminosity LHC (HL-LHC) collider at CERN. A prototype has been exposed to electron beams of different energies at the INFN Frascati (Italy) Beam Test Facility. This paper presents results from the studies performed on the prototype, such as signal amplitudes, light yield and energy resolution.

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.

A prototype for a sampling calorimeter made out of cerium fluoride crystals interleaved with tungsten plates, and read out by wavelength-shifting fibres, has been exposed to beams of electrons with energies between 20 and 150 GeV, produced by the CERN Super Proton Synchrotron accelerator complex. The performance of the prototype is presented and compared to that of a Geant4 simulation of the apparatus. Particular emphasis is given to the response uniformity across the channel front face, and to the prototype׳s energy resolution.

The High Luminosity LHC (HL-LHC) will integrate 10 times more luminosity than the LHC, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry, and hallmarks the issue for future colliders. As part of its HL-LHC upgrade program, the CMS collaboration is designing a High Granularity Calorimeter to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (ECAL) and hadronic (HCAL) compartments. This will facilitate particle-flow calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The ECAL and a large fraction of HCAL will be based on hexagonal silicon sensors of 0.5-1cm$^{2}$ cell size, with the remainder of the HCAL based on highly-segmented scintillators with SiPM readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. An overview of the HGCAL project is presented, covering motivation, engineering design, readout and trigger concepts, and performance (simulated and from beam tests).

It is here presented the diboson production cross section measured by the CMS collaboration in $pp$ collisions data at $\sqrt{s}$=7 TeV. $W \gamma$ and $Z \gamma$ results from 2010 analyses (36 pb$^{-1}$) are presented together with 2011 first measurements of $WW$, $WZ$ and $ZZ$ final states obtained using 1.1 fb$^{-1}$. Results obtained with 2010 data are also interpreted in term of anomalous triple gauge couplings.

Este artigo objetiva analisar a utilização de Ambientes Virtuais de Aprendizagem na formação de lideranças. Foram utilizadas como metodologia a pesquisa bibliográfica e documental, valendo-se do estudo de caso para uma investigação aprofundada. Por meio deste estudo foi possível verificar que ao combinar a tecnologia com a abordagem sociointeracionista é possível criar ambientes virtuais de aprendizagem que promovam a interação social, permitindo o desenvolvimento de competências.

O presente artigo tem como objetivo avaliar a implantação da Educação a Distância como modalidade de ensino na . Esta pesquisa qualitativa, que se configura num estudo de caso, é de cunho descritivo e analítico. Na primeira parte do trabalho apresentamos o embasamento teórico para amparar a discussão aqui proposta, em seguida a caracterização da organização pesquisada. Por fim, apresentamos os resultados do estudo de caso, quanto a implantação da educação a distância

Este artigo objetiva discutir sobre a importância da formação de instrutores internos em uma escola de contas e como a utilização de Ambientes Virtuais de Aprendizagem pode contribuir para essa formação. Foram utilizadas como metodologia a pesquisa bibliográfica e documental, valendo-se do procedimento exploratório-descritivo. Por meio deste estudo foi possível verificar que para além de professores detentores de competências e habilidades afetas a esse tipo de atividade, há que se buscar e preparar aqueles que estejam em sintonia com as demandas contemporâneas, inclusive no manejo de metodologias e recursos virtuais de aprendizagem.

I-MCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of micro-channel plates (MCP) for single ionizing particles and fast timing of showers in high rate environments. Results from tests with electrons with energies up to 50 GeV of MCP devices with different characteristics are presented. In particular detection efficiency and time resolution are measured for a range of MCP prototypes: different MCP channel diameter and layers configuration are studied. Devices operated in I-MCP configuration, where the particle detection proceed through direct ionization of the MCP layers, are studied in comparison with the more usual PMT-MCP configuration. The results show efficiencies up to 70% for single charge particle detection for I-MCP devices with a time resolution of about 40 ps. The efficiency raise to 100% in response to high energy electromagnetic showers.

Future high rate hadron colliders are expected to have hundreds of concurrent proton-proton interactions in the same bunch crossing, deteriorating the energy resolution and identification capabilities of calorimeters. The possibility to distinguish neutral particles coming from different interaction vertices is being pursued as a tool to reduce pile-up contamination in calorimeters, and restore optimal performance. A time of flight resolution of the order of 20 ps will be able to reduce neutral particles pile-up contamination at the calorimeter level by 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 (MCP) can be used in PMT configuration as fast charged particles detector (resolution of better then 30 ps can be 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 than 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 opens 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. Preliminary results on the radiation hardness of the i-MCP configuration will be also presented.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with absorber plates made of tungsten, and read out by wavelength-shifting fibres has been tested with high-energy electron beams at the CERN SPS H4 beam line, as well as with lower-energy beams at the INFN Frascati Beam Test Facility in Italy. Energy resolution studies revealed a low stochastic term (<10%/E). This result, combined with high radiation hardness of the material used, marks this sampling calorimeter as a good candidate for the detectors׳ forward regions during the high luminosity phase of LHC.

The performance of the CMS electromagnetic calorimeter (ECAL) has been continuously monitored at the LHC. The evolution of this performance is a critical issue for the future. Work has started to assess the need for possible changes to the detector to ensure adequate performance for High-Luminosity LHC (HL-LHC) operation, planned for 2022 and beyond. Results from CMS running, beam tests and laboratory measurements on proton-irradiated crystals are combined to predict the performance of the current detector at the HL-LHC. This is achieved using MC simulations of the CMS detector, where the ECAL response has been tuned to account for the ageing of the detector components. In addition, various R&D studies are presented in case modification or replacement of the ECAL Endcaps is needed for the HL-LHC period.

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-CeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> 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.

Cette these presente la premiere mesure de production du W Z avec le detecteur CMS au LHC en utilisant les modes leptoniques. La reponse du calorimetre electromagnetique (ECAL) est etudiee par la mesure du pouvoir d'arret de muons dans le tungstate de plomb d'ECAL. Les electrons sont valides avec les premieres donnees pour etre utilisable dans toutes les analyses. Avec les donnees de rayons cosmiques, le pouvoir d'arret de muons traversants le tungstate de plomb du calorimetre electromagnetique a ete mesure pour une gamme d'impulsion 5-1000 GeV/c. Le resultat compatible avec l'attendu a permis de valider l'echelle d'energie d'ECAL, determinee auparavant avec un faisceau d'electrons de 120 GeV/c, dans la region du sub-GeV en accord avec 1. 004+0. 002-0. 003(stat. ) ±0. 019(syst. ). Les donnees des premieres collisions de LHC ont permis la verification des algorithmes de reconstruction des electrons, en particulier pour la determination des pre-traces dans la partie la plus interne du trajectographe. Les algorithmes ont ete optimises, sur des electrons issus de desintegrations de bosons W et entierement valides avec 14/pb de donnees environ. La mesure physique est la section efficace de production des bosons associes WZ dans les collisions proton-proton a √s =7TeV. La signature claire de la desintegration en leptons permet l'extraction efficace du signal et la rejection du bruit de fond, pour chaque canal considere. Le premier evenement a ete observe avec 36/pb de donnees. Avec 1. 09/fb, la section de production de WZ a ete mesuree pour la premiere fois a √s =7TeV σ(WZ) = 19. 11+3. 30-2. 53(stat. )±1. 10(syst. )±1. 15(lumi. )pb et trouvee en accord avec la prediction du Model Standard (18. 57+0. 75-0. 58 pb NLO)

IMCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of microchannel plates (MCP) for fast timing of showers in high rate environments. The usage of MCPs in “ionisation” mode has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The fast time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Results from tests with electrons with energies up to 150 GeV of MCP devices with different characteristics will be presented, in particular detection efficiency and time resolution.

The first CMS data from the center-of-mass energy of 900 GeV proton-proton collisions were analyzed in order to commission electron reconstruction and assess its performance. A comparison between data and simulation of all the key ingredients for the electron physics objects reconstruction and identification was performed. The good agreement shown indicates that the sub-detectors response is well modeled in the simulation and that the algorithms designed and optimized with the simulation are functioning as expected.

The CMS endcap calorimeter upgrade for the high-luminosity LHC (HL-LHC) uses, for the most part, silicon sensors to achieve radiation tolerance, with the further benefit of a very high readout granularity.Developing a reconstruction sequence that fully exploits the granularity, and other significant features of the detector like precision timing, is a challenging task.The aim is for operation in the high pileup environment of HL-LHC.An iterative clustering framework (TICL) is being developed.This takes as input clusters of energy deposited in individual calorimeter layers delivered by an "imaging" algorithm which has recently been revised and tuned to deliver excellent performance.Mindful of the projected extreme pressure on computing capacity in the HL-LHC era the algorithms are being designed with GPUs in mind.In addition, reconstruction based entirely on machine learning techniques is being developed and studied.This talk will describe the approaches being considered and show first results.