1,721,494 research outputs found
Calculation of the electric field in GaAs particle detectors
No full textIn this work a numerical approach has been used to investigate some properties of semi-insulating GaAs detectors. In particular the electric field has been obtained by solving transport and Poisson equations. A comparison with the results obtained in a previous work by another group has been carried out
A study of the electrical and charge-collection properties of semi-insulating GaAs detectors
No full textIn this work a numerical approach has been used to investigate some properties of semi-insulating GaAs detectors. In particular, the electric field and the carriers mean free path distributions have been obtained, by solving transport and Poisson equations. The knowledge of these quantities allows us to determine the charge-collection efficiency and other detector characteristics. A comparison with the experimental results of X-ray irradiated detectors of different thicknesses has been carried out
BSM (Beyond Standard Model) searches with escaping invisible particles associated to a Higgs boson and protons tagged with the PPS (Precision Proton Spectrometer)
No full textIn this thesis is presented a new analysis with the PPS (Precision Proton Spectrometer) detectors of CMS, in which we search for a production of a scalar particle by photon fusion. The scalar should be seen in association with a Higgs particle, detected in the CMS central detector, and an additional invisible massive particle, called X. The process analyzed is: p + p → p + H + X + p.
The protons-tagged events are recorded in the proton-proton collisions at √s = 13 TeV in the year 2018 at the LHC accelerator. The interaction is simulated by Monte Carlo methods, then the outputs and strategies to select the signal against the background are studied. Then, a study of the proton mass spectrum of the simulated signal and background is carried out. The analysis is developed over a range of the scalar particle masses between 800 and 1600 GeV where the PPS detector has the maximum acceptance
Search for new resonances in p-p collisions using fully leptonic W+W− decays with the CMS detector
No full textThis thesis presents a search for a possible heavy Higgs boson, X, decaying into a
pair of W bosons, in the mass range from 200 GeV to 3 TeV. The analysis is based on
proton-proton collisions recorded by the CMS experiment at the CERN LHC in 2016,
corresponding to an integrated luminosity of 35.9 fb −1 at sqrt{s}=13 TeV. The W boson
pair decays are reconstructed in the 2l2ν and lνqq̄ final states. Both gluon-gluon
fusion and electroweak production of the scalar resonance are considered. Dedicated
event categorizations, based on the kinematic properties of the final states, are
employed for an optimal signal-to-background separation. Combined upper limits at
the 95% confidence level on the product of the cross section and branching fraction
excludes a heavy Higgs boson with Standard Model-like couplings and decays in the
range of mass investigated
Study of the calorimetric detection of the muon to electron conversion in the Mu2e experiment
No full textThe Mu2e experiment will search for Charged Lepton Flavor Violation (CLFV), looking at the coherent conversion of a muon into an electron in the field of an aluminum nucleus. The knowledge of such a CLFV reaction allows to indirectly probe new physics at energy scales up to thousands of TeV, inaccessible with direct searches at either present or planned high energy colliders. For this reason, Mu2e will measure the muon-to-electron conversion rate R_{\mu e} with an unprecedented accuracy, so to improve of a factor 10^4 the best current measurement and, in case of no observation, to constrain its value below 6 x 10^-17 at 90% of CL. To reach this ambitious sensitivity, about 10^18 muonic atom decays have to be observed: Mu2e is expected to use an intense pulsed muon beam, and rely on a detector system composed of a straw tube tracker and an electromagnetic calorimeter. The calorimeter is composed of 1348 un-doped CsI crystals, each coupled to two large area Silicon Photomultipliers (SiPMs). It plays a central role in the Mu2e measurement, providing particle identification capabilities that are necessary to reject the cosmic muons and antiprotons induced background. Moreover, the calorimeter has to help the tracker providing a seed for the pattern recognition and to provide a fast independ trigger. Having these experimental requests as pivotal reference, a set of Quality Assurance (QA) criteria for the calorimeter active components have been defined. Following the corresponding QA procedures, a first batch of crystals and photosensors has been characterized and used to assemble a medium scale prototype of the calorimeter (Module-0). The Module-0 has been studied by means of a 100 MeV electron beam, confirming that expected calorimeter performances well satisfy the Mu2e requirements
A Search for Particles Beyond the Standard Model with the PPS
No full textThis thesis work deals with the search for the associate production of a Z boson and a new massive particle X with two forward protons in the PPS, the forward proton spectrometer of the CMS experiment. The search is model independent and performed in a mass range of the X particle between 800-1600 GeV. The expectations on the signal hypothesis are based on a simple toy Monte-Carlo (MC) generator, that I contributed to develop. The effects of the PPS miscalibration on a possible signal are presented as well, and represent the first time that such studies are performed within the PPS collaboration. Finally, an analysis of the main backgrounds of the search is performed and several selection cuts are presented. These are expected to enhance the significance of an excess in the hypothesis that the X particle is fully invisible to the central detector
Development of semi-insulating GaAs detectors for digital radiography
No full textIn this paper we present the results of an experimental study concerning different contact deposition processes on Semi-Insulating (S.I.) GaAs detectors aiming to study and optimize their performance in terms of leakage current, break-down voltage, charge collection efficiency and energy resolution when irradiated with 60 KeV photons; in particular the effect of the mesa etching treatment on the Schottky barrier side of the detectors has been studied. Such treatment certainly improves the detector performances related to the very important issue of the electric field uniformity. Detectors with satisfactory features in view of their possible application to Digital Radiography have been obtained. RI Cola, Adriano/G-2379-201
Charge collection properties of GaAs detectors for digital radiography
No full textIn this paper we present the result of an experimental study concerning the charge collection efficiency (cce) properties of various (Semi Insulating) S.I.-GaAs detectors, when irradiated with 60 keV photons. Some of these detectors, 100 or 200 mu m thick, are equipped with a new type of Ohmic contact manufactured by Alenia S.p.A. (Italy), which allows the detector to withstand a bias voltage up to 700 V before break-down. A cce value of 100% has been measured for the 100 mu m thick detector. The behavior of a matrix of 36 square pixels, 200x200 mu m(2) spaced 200 mu m, has been investigated for the cross talk between adjacent pixels and for cce uniformity, obtaining good results. RI maestro, paolo/E-3280-201
Searches for resonant double Higgs production in the bbττ final state at the CMS experiment
Get PDFThis thesis presents a search for resonant Higgs bosons pair (HH) production via the Gluon-gluon Fusion (ggF) mechanism, predicted in different Beyond Standard Model (BSM) scenarios to be observable with the current Large Hadron Collider (LHC) dataset. The search focuses on the HH → b ̄bτ+τ− final state, which offers a good balance between branching fraction and experimental feasibility but presents challenges due to neutrinos in τ decays and background discrimination. Advanced techniques are employed for τ reconstruction and identification, along with sophisticated modeling of the relevant backgrounds. The analysis, performed on proton-proton (pp) collision data collected by the Compact Muon Solenoid (CMS) experiment during Run 2 (2016–2018) with an integrated luminosity of 137.1 fb−1, employs advanced techniques for τ reconstruction and background modeling. The τ+τ− pair is studied through three decay channels: τhτh (fully hadronic) and τhτl, where τh represents a tau lepton decaying into hadrons plus a ντ , and τl corresponds to the leptonic decay of the tau into either an electron (l = e) or a muon (l = μ). A key aspect of the analysis is the use of machine- learning-based identification algorithms, including DeepTau for τ identification. The primary results are obtained using DeepTau2017v2p1, the stable version recommended for Run 2 analyses. Additionally, a study with DeepTau2018v2p5, an improved and re-trained version optimized for future runs, demonstrates better data/MC agreement, confirming its suitability for upcoming analyses. As part of the CMS internal review process, the analysis remains blinded to avoid bias. The 95% Confidence Level upper limits on the HH production cross section are set as a function of resonance mass and spin, interpreted within the Warped Extra Dimensions theory (WED) model for masses from 250 to 3000 GeV under spin-0 and spin-2 hypotheses
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