C. Rovelli

The reconstruction of the energy and momentum of isolated electrons in CMS combining tracking and electromagnetic calorimetry information is described. The emphasis is put on primary electrons with transverse momentum below 50 GeV/c. The energy deposited in the electromagnetic calorimeter is measured in clusters of clusters (superclusters) which collect bremsstrahlung photons emitted along the electron trajectory in the tracker volume. The electron tracks are built from seeds in the pixel detector found via a cluster-driven pixel hit matching algorithm, followed by a reconstruction of trajectories in the silicon strip tracker with a Gaussian sum filter. Electrons are classified using observables sensitive to the pattern of bremsstrahlung emission and electromagnetic showering in the tracker material. Energy scale corrections depending on the electron class are applied to the supercluster and estimates of associated errors are obtained. The electron energy is deduced from a weighted combination of the corrected supercluster energy and tracker momentum measurements. The electron direction is that of the reconstructed electron track at interaction vertex. The pre-selection of isolated electron candidates for physics analysis is described. Class-dependent observables combining tracking and calorimetry information are discussed for electron identification.

The helicity dependence of the total cross section for the γ→p→→nπ+π0 reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement was performed with the large acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, due to the intermediate production of the D13 resonance.

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 integrity of neuroprotection is an important component against the development of cognitive disorders and AD. Within this context, DHEAS would seem to have some positive metabolic and endocrine effects to delay brain aging by recovering the impairment of neuroprotective growth factors. In the present study we measured by ELISA the secretion of insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and transforming growth factor-beta1 (TGFbeta1) in the supernatants of cultured circulating peripheral blood mononuclear cells (PBMC) from which natural killer cells (NK) were separated (PBMC-NK) (pg/ml/7.75x10(6) cells) in healthy subjects and in age-matched patients with mild to moderate AD. The growth factors were measured in spontaneous conditions and after stimulation with growth hormone (GH) 1 microg/ml (IGF-1), lipopolysaccharide (LPS) 1 microg/ml (VEGF) and glucose 10 microM (TGF(beta1). AD group demonstrated at baseline a severe reduction of IGF-1 (3.7+1.2 pg/ml after GH), VEGF (63+/-18 pg/ml spontaneous and 210+/-65 pg/ml after LPS) and TGF(beta1 (33+/-10 pg/ml spontaneous and 75+/-12 pg/ml after glucose) secretions compared to healthy elderly subjects (IGF-1, 9.5+/-2.8 pg/ml after GH, p<0.001; VEGF, 117+/-38 pg/ml spontaneous, p<0.001 and 690+/-120 pg/ml after LPS, p<0.001; and TGF(beta1, 73+/-21 pg/ml spontaneous, p<0.001 and 169+/-53 pg/ml after glucose, p<0.001). Significant positive correlations between IGF-1 and VEGF concentrations were found both in healthy subjects (r=0.87, p<0.001) and in AD subjects (r=0.87, p<0.001). The co-incubation of NK cells with DHEAS (10(6) M/ml/cells) significantly increase IGF-1, VEGF and TGF (beta1 production, reaching in AD group the normal concentrations found in healthy subjects (IGF-1, 7.9 + 2.4 pg/ml after GH; VEGF, 105+/-31 pg/ml spontaneous and 670+/-112 pg/ml after LPS; and TGFfbeta1, 68+/-18 pg/ml spontaneous and 155+/-48 pg/ml after glucose). These data suggested that DHEAS is able to increase the immunoendocrine production of neuroprotective growth factors, which is reduced in AD subjects, so suggesting a new approach in the treatment of dementia.

INFN Kids is a science education project of the Italian National Institute for Nuclear Physics addressed to young people of Primary and Middle schools age. The initiative aims at raising children’s curiosity towards science with a focus on Physics, inspiring them with science by illustrating the different research fields that INFN is pursuing, the development in technologies along with the applications in everyday life and presenting people who animate science. It gathers technicians and researchers of thirteen units and National labs in the design and realization of multimedia products, laboratory-based activities, comics, science demos and exhibits. The activities are conducted online and in person in schools, science festivals and at INFN’s sites. The adopted methodologies and the didactic tools (lectures, interactive lessons, hands-on sessions, science games) involve children in the direct exploration of natural phenomena. Given the manifold plan of activities the recipients of the project are also teachers and families, and this allowed to expand and use different formats to meet the audience’s requests. We here present an overview of the ongoing initiatives to share our experiences and we illustrate in particular the comics centered on the characters Leo and Alice that drive children in the investigation of the micro and macro world, and the laboratory-based activities designed to introduce kids some fundamental concepts related to matter and its inner structure.

A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, recorded with the CMS detector. The coupling strength with respect to the standard model value, $Y_\mathrm{t}$, is determined from kinematic distributions in $\mathrm{t\bar{t}}$ final states containing ee, $μμ$, or e$μ$ pairs. Variations of the Yukawa coupling strength lead to modified distributions for $\mathrm{t\bar{t}}$ production. In particular, the distributions of the mass of the $\mathrm{t\bar{t}}$ system and the rapidity difference of the top quark and antiquark are sensitive to the value of $Y_\mathrm{t}$. The measurement yields a best fit value of $Y_\mathrm{t} =$ 1.16 $^{+0.24}_{-0.35}$, bounding $Y_\mathrm{t}$ $\lt$ 1.54 at a 95% confidence level.

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce)is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce ($[Lu_{(1-x)}Y_x]_2SiO_5$:$Ce$) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers.The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

Abstract The organometal halide perovskites (OMHP) are promising candidates for fast, sensitive, and large area photodetectors. In the last decade, several techniques have been developed with complementary advantages. Film devices are thin and can be scaled to large area, but have a large number of grain‐boundaries related defects. Single bulk crystals instead have higher purity, but are thicker and can not be easily produced on large areas. In this work, a microfluidics‐assisted technique to realize a controlled growth of OMHP single crystals, in the form of microwires, directly on a conductive patterned substrates, is presented. This technique enables the realization of vertical devices with a pixelated sensor layer. The resulting devices present gain, a responsivity up to 200 AW −1 and a fast rise time down to 35 µs. This is the first demonstration of a OMHP vertical device realized on a patterned substrate using microfluidics‐assisted techniques.

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvertζ_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvertζ_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

The CMS Electromagnetic Calorimeter (ECAL) is made of about 75 000 lead tungstate crystals. The 61 200 crystals of the barrel part are read by Avalanche Photodiodes (APD) with internal amplification of the signal. Since the gain strongly depends on the bias voltage, the APDs require a very stable power supply system. To preserve the high energy resolution of the calorimeter, a stability of the bias voltage of the order of 10-4 is required over several months, a typical interval between absolute calibrations of the full read-out chain with physics events. This paper describes the high voltage power supply system developed for CMS ECAL and its performances as measured in laboratory tests and during test-beam operations of several modules of the calorimeter.

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.

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.

The CMS ECAL Collaboration developed a full simulation of the detector which is integrated in the software framework CMSSW. The simulation is based on the Geant4 tool for the description of particles interactions with the detector material. Care is given to the detailed description of the detector geometry and of the electronics response. The simulation software is fully operational and it is currently under validation using real data from testbeams and from commissioning with cosmic rays.

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.

The discovery potential of the CMS detector at the LHC for the Standard Model Higgs boson is discussed. The full simulation of the detector is used and many possible sources of systematic uncertainties are considered. The results show that Standard Model Higgs can be discovered with about 15 fb-1.

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016-2018, corresponding to an integrated luminosity of 117 fb$^{-1}$. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H $\to$ SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10-100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass ($\approx$15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions $\mathcal{B}$(H $\to$ SS) $\lt$ 20% for proper decay lengths of 10-50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.

A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13\TeV is presented. The transverse momenta of jets within $\lvert\eta\rvert \lt$ 4.7 reach down to 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.

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 CMS electromagnetic calorimeter (ECAL) comprises 75848 scintillating lead tungstate crystals. 61200 crystals are contained in the ECAL Barrel section and are read out by avalanche photodiode (APD) with internal gain of about 50. This gain is achieved with a high voltage (HV) of about 400 Volts. The gain stability requirement implies a supply voltage stable to within 0.01%. We describe our experience with the installed Barrel HV power supply system, which has been used for data taking since 2008.

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.

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel H → WW ( * ) → e + νe - ν, for a Higgs boson mass M H in the range 120 < M H < 160 GeV/c 2 . A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass M H ≥ 134 GeV/c 2 would be observed with a significance above three standard deviations in the e + νe - ν channel alone for an integrated LHC luminosity above 30 fb -1 .

The reconstruction of the four-momentum of electrons in CMS combining tracking and electromagnetic calorimetry information is described.Electrons in the energy range from 5 to 100 GeV are considered. Different electron topologies, depending on the amount of bremsstrahlung and re-interaction in the inner tracker material, are identified to select the most adapted energy scale correction for the electron supercluster and to estimate the associated error. The electron tracks are built starting from a cluster-driven seed finding in the pixel detector, followed by a Gaussian Sum Filter technique to build and fit trajectories in the Silicon Tracker Detectors. The electron four-momentum is deduced from a combination of the supercluster energy and tracker momentum measurements, with the direction taken from the electron track at interaction vertex.

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.

In this note we summarize the progress made by the calorimeter simulation task force (CALOTF) over the past year. The CALOTF was established in February 2008 in order to understand and reconcile the discrepancies observed between the CMS calorimetry simulation and test beam data recorded during 2004 and 2006. The simulation has been significantly improved by using a newer version of GEANT4 and an improved physics list for the full CMS detector simulation. Simulation times have been reduced by introducing flexible parameterizations to describe showering in the calorimeter (using a GFLASH-like approach) which have been tuned to the test beam data.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

A search for the resonant production of high mass photon pairs is presented.The search focuses on spin-0 and spin-2 resonances with an invariant mass between 0.5 TeV and 4.5 TeV and with a width, relative to the mass, between 1.4×10 -4 and 5.6×10 -2 .The results are based on proton-proton collision data at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC and corresponding to an integrated luminosity of 12.9 fb -1 .The results of the search are combined statistically with those previously obtained by CMS at √ s = 8 TeV and √ s = 13 TeV, in 2012 and 2015.No significant excess with respect to the Standard Model expectation is observed.Limits are set on scalar resonances produced through gluon-gluon fusion and on Randall-Sundrum gravitons.

HEPscape is an escape room about high energy physics. The project has been designed and created by researches from the National Institute of Physics in Rome with the support of Sapienza, University of Rome.Escape rooms for learning purposes are more and more frequent nowadays. HEPscape represents, based on the knowledge of the authors, the first particle physics escape room ever built so far. The escape room is an activity in which one finds him/herself involved in a specific environment: a series of unexpected events and challenges have to be solved in order to be able to get out of the game. The proposed project, characterized by strong innovativeness and originality, aims to introduce the participants to the topics of high energy physics with a playful and fun approach, in which one learns by playing and collaborating in a group what does team work mean. HEPscape visitors learn while having fun some notions concerning particle physics and fundamental interactions, the functioning of the Large Hadron Collider (LHC) at CERN in Geneva and the recent or ongoing research activities of Compact Muon Solenoid (CMS) and ATLAS, two of the multi-purpose experiments operating at the LHC.The visitors have the impression of visiting the LHC at CERN and of entering one of the experimental underground control rooms. HEPscape makes use of high-technology projectors, LED lamps controlled remotely and printed posters which replicate the control room environment. Through some clues, that are kept in lockers hidden in the room, the visitors discover how particle accelerators and high energy physics experiments are build and work. The project aims at a varied audience, from elementary school students, to high school students to adults, with attention also to people with special needs. The riddles can be tuned to the age of the group, resulting in a fun and affordable experience for everyone. HEPScape is made of portable equipments that can be transported and assembled in less than two hours. This allows to use it in science fairs and exhibitions. In addition it can be brought on demand to high schools also in remote places. The possibility of creating the escape room in different languages ​​is also envisaged.So far HEPscape has registered more than 1000 visitors. Feedback and experiences from two science fairs happened in Italy in 2021 will be also presented in the talk.

HEPScape is an escape room about particle physics built in 2021 by a team of INFN researchers. The visitors have the impression of entering one of the experimental control rooms of the Large Hadron Collider at CERN. Through clues hidden in the room, and with the help of a moderator, they discover the purpose of high energy physics and how particle accelerators work. HEPScape is made of portable equipment and this allows to use it in science fairs, exhibitions and schools. The experience from three science fairs in Italy is presented.

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel , for a Higgs boson mass MH in the range 120 < MH < 160GeV/c2. A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass MH 134GeV/c2 would be observed with a significance above three standard deviations in the channel alone for an integrated LHC luminosity above 30 fb−1.

The electromagnetic calorimeter (ECAL) of the Compact Muon Solenoid experiment is currently taking data at the Large Hadron Collider (LHC).The High Luminosity phase of the LHC will provide unprecedented instantaneous and integrated luminosity, at the price of very challenging running conditions in terms of radiation level, data rates and number of simultaneous collisions in the same bunch crossing.The upgrade of the barrel part of the CMS ECAL is discussed in this paper.The requirements of the upgraded detector are reviewed and a presentation of test beam results is given.

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ($\Delta v_2$) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, $v_2$) between $\mathrm{D}^0$ ($\mathrm{\bar{u}c}$) and $\overline{\mathrm{D}}^0$ ($\mathrm{u\bar{c}}$) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of $\Delta v_2$. The rapidity-averaged value is found to be $\langle\Delta v_2 \rangle =$ 0.001 $\pm$ 0.001 (stat) $\pm$ 0.003 (syst) in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the $\mathrm{D}^0$ and $\overline{\mathrm{D}}^0$ mesons $v_2$ and triangular flow coefficient ($v_3$) as functions of rapidity, transverse momentum ($p_\mathrm{T}$), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt $\mathrm{D}^0$ meson $v_2$ values is observed, while the $v_3$ is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental instrument for these analyses and its energy resolution is crucial for the Higgs boson mass measurement. Recently the energy response of the calorimeter has been precisely calibrated exploiting the full Run2 data, aiming at a legacy reprocessing of the data. A dedicated calibration of each detector channel has been performed with physics events exploiting electrons from W and Z boson decays, photons from π 0 and η decays, and from the azimuthally symmetric energy distribution of minimum bias events. This talk presents the calibration strategies that have been implemented and the excellent performance achieved by the CMS ECAL with the ultimate calibration of Run2 data, in terms of energy scale stability and energy resolution.

The CMS experiment at the LHC features an electromagnetic calorimeter (ECAL) made of lead tungstate scintillating crystals. The ECAL energy response is fundamental for both triggering purposes and offline analysis. Due to the challenging LHC radiation environment, the response of both crystals and photodetectors to particles evolves with time. Therefore continuous monitoring and correction of the ageing effects are crucial. Fast, reliable and efficient workflows are set up to have a first set of corrections computed within 48 hours from data-taking, making use of dedicated data streams and processing. Such corrections, stored in relational databases, are then accessed during the prompt offline reconstruction of the CMS data. Twice a week, the calibrations used in the trigger are also updated in the database and accessed during the data-taking. In this note, the design of the CMS ECAL data handling and processing is reviewed.

Une des questions de la physique des hautes energies est l'origine de la masse des particules. Le mecanisme de brisure de symetrie electrofaible est communement utilise pour l'expliquer. Il predit l'existence d'une particule scalaire, le boson de Higgs, mais les recherches effectuees n'ont pas permis sa decouverte. La recherche du Higgs est une des motivations pour le projet d'un nouvel accelerateur, le LHC, en construction au CERN. Le LHC est un collisionneur proton-proton avec une energie dans le centre de masse egale a 14 TeV. Le detecteur CMS est un des detecteurs prevus aupres du LHC. Le sujet de la these est l'etude des possibilites de detection du Higgs pour le canal H->WW^*->2e2nu. Nos contributions a la calibration du calorimetre electromagnetique ECAL et au developpement des algorithmes de reconstruction des electrons sont egalement presentees dans la these. Dans le chapitre 1 nous donnons un resume de la partie du Modele Standard relative aux interations electrofaibles et au secteur de Higgs. Dans les chapitres 2 et 3, une description du LHC et du CMS est donnee et la procedure du calibration du ECAL est decrite. Dans le chapitre 4 nous donnons les resultats de la precalibration des cristaux du ECAL pendant le test en faisceau et l'etude du controle de la perte de transparence avec un laser. Dans le chapitre 5 les algorithmes utilises pour la reconstruction des electrons sont decrites et un algorithme pour la reconstruction des traces electromagnetiques est developpe. Dans le chapitre 6 l'etude du canal H->WW^*->2e2nu est presentee dans le domaine de masses s'etendant de 120 jusqu'a 170 GeV

Efficiency and precision in electron reconstruction is of ultimate importance for Higgs boson search at LHC through Higgs decay to four electrons. Main problems in electron reconstruction at CMS are reviewed and solution proposed

Electron reconstruction in CMS is presented, with emphasis on estimation of momentum, classification, identification and selection.

A measurement of the top quark mass is performed using a data sample enriched with single top quark events produced in the $t$ channel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, recorded at $\sqrt{s}$ = 13 TeV by the CMS experiment at the LHC in 2016.Candidate events are selected by requiring an isolated high-momentum lepton (muon or electron) and exactly two jets, of which one is identified as originating from a bottom quark. Multivariate discriminants are designed to separate the signal from the background. Optimized thresholds are placed on the discriminant outputs to obtain an event sample with high signal purity. The top quark mass is found to be 172.13$^{+0.76}_{-0.77}$ GeV, where the uncertainty includes both the statistical and systematic components, reaching sub-GeV precision for the first time in this event topology. The masses of the top quark and antiquark are also determined separately using the lepton charge in the final state, from which the mass ratio and difference are determined to be 0.9952$^{+0.0079}_{-0.0104}$ and 0.83$^{+1.79}_{-1.35}$ GeV, respectively. The results are consistent with $CPT$ invariance.