Sandro Gonzi

RESEARCH INTERESTS The topics I am more interested to work on are: data analysis, statistics, electroweak physics, quantum chromodynamics, phenomenology of hadronic collisions, Monte Carlo generators for LHC, tracking detectors, tracking algorithms and computing. DATA ANALYSIS My principal research activity lies in the field of data analysis in subnuclear physics at high energy accelerators. In particular, I spent the academic formation period in studying the Standard Model Z/γ + jets process in the CMS experiment at the LHC. I became interested in this subject during my Master’s Degree Thesis work in which I analyzed the first data collected in 2010 by CMS, by focussing on the electroweak Z + jets process with the Z boson decaying in the di-electron channel (Z → e+ e−). Later, I extended my studies to the di-muon Z decay channel (Z → μ+ μ−) by focussing on the determination of selection efficiencies and systematic uncertainties related to the pile-up events. The material produced has been used for the preparation of conferences and for writing an article. During the first part of the Ph.D. program I extended the study on this subject by contributing to the measurement of angular correlations and event shape variables in Z(→ l+ l−) + jets (l = e, μ) processes. This work concerned in particular the phase-space region with Z bosons at high transverse momentum, that is critical in searches for new phenomena that are based on a large apparent imbalance in the total transverse momentum. The principal contribution that I gave to the analysis has been the evaluation of the reconstruction and selection efficiency of Z(→ l+ l−) candidates by using the so-called Tag-and-Probe (T&P) data-driven method. The material produced has been used for writing an article. In the second part of the Ph.D. program I worked on the γ + jets process, by writing a Thesis on the measurement of its differential cross section production as a function of the photon transverse momentum in the phase-space region with photons at high transverse momentum. I studied a series of selection cuts in order to identify the γ + jets process with respect to the background, I extracted the selection efficiency values (by using the Tag-and-Probe method) and I developed a background extraction with a full data-driven approach. The calculation of the differential cross section has then been performed after a correction of the detector effects and a detailed treatment of the systematic uncertainties. The material produced has been be used for writing an article concerning the measurement of the Z + jets/γ + jets differential cross section ratio with respect to the transverse momentum of the boson (Z/γ), a measurement that can be used to accurately predict the Z(→ ν ν) + jets background in new physics searches. All previous work has required the study of statistical techniques for dealing with data, of Monte Carlo simulation generators (in particular MADGRAPH and PYTHIA) and of advanced computing skills (including through the use of the grid resources). SIMULATIONS OF THE DETECTOR RESPONSE During the Ph.D. program I participated in activities on the CMS tracker as responsible for the maintenance of the geometry used by the simulation. This is implemented in the software GEANT4 that using a detailed description of the detector, accurately simulates the interaction between the radiation and matter as, for example, the energy deposited by the particles, the effects of multiple scattering of the subdetectors and other effects such as the bremsstrahlung of electrons. My contribution in this field consisted in studying the detector response to obtain a more accurate profile of the distribution of the material in the tracker (material budget). The material produced has been used for writing an article. In particular, I specialized in creating new geometries, as alternatives to the nominal one, with specific volumes of the tracker altered to correct any discrepancies observed in the electromagnetic calorimeter between Monte Carlo simulations and experimental data. SOFTWARE DEVELOPMENT Once received the title of Ph.D. in Physics and Astronomy, I applied the knowledge acquired in software development by working with Sinerlab s.r.l., a company specialized in the application of X-ray fluorescence for the determination of the elemental composition of materials and for the measurement of the thickness of coatings. My contribution in this field consisted in the development of a software application for qualitative and quantitative analysis of energy dispersive X-ray Fluorescence (ED-XRF) spectra acquired on bulk samples. The material produced has been used for the preparation of conferences.