PhD activities report
Activities done as part of my PhD studentship included lectures and research activities.
I attended a set of courses and seminars, following the “Piano di Studi” approved by the PhD school. The following subjects were covered:
• Particle Physics • Medical physics • Quantum optics
• English scientific writing
I successfully passed examination on the indicated subjects.
Research activity was done within the ATLAS collaboration. It mainly focused on data analysis, which is the subject of the PhD thesis. Additional detector-related work has been done for the ATLAS Qualification Task (required to be qualified as ATLAS author).
In the following I detail my research activities with the ATLAS experiment. PhD thesis
• I contributed to the measurement of Standard Model semileptonic WW/WZ associated production cross section at 𝑠 = 8 TeV (advisor: T. Del Prete). I participated to the definition of the analysis strategy and developed the full analysis software, which was shared with a master student that I co-supervised. In addition, I am the Contact Editor for the publication in preparation.
The analysis covered the final state already measured at 𝑠 = 7 TeV (called resolved) defined by one electron/muon, a neutrino and two jets, and was also extended to a new final state (called boosted) in which an hadronically decaying boosted W/Z decays is detected as a single jet of large radius.
I contributed to both channels as analyser and editor, in the following I list the main topics I covered, a similar list with more details can be found in the thesis introduction.
o Definition and checks of the event selection (cut-flow) of the resolved analysis o Determination of the truth-level selection defining the fiducial phase space,
computation of the expected fiducial cross section and the correction factor (D in the thesis) for cross section computation. Determination of systematic uncertainties affecting these quantities. The study has been done both for resolved and boosted channels.
o Study of the application of Stewart-Tackmann method for scale uncertainty computation (details are provided in the thesis). For resolved and boosted channels. o Running the fit for cross section extraction, as a cross check of other analyser’s work
in the resolved channel.
o Systematic evaluation in the boosted channel.
We obtained consistent results between the resolved and boosted channels, reaching a significance of 4.5 σ in the resolved channel, while in the boosted we were limited by the low statistics and larger systematics.
I also studied an independent cross check of the resolved cross section measurement, using an alternative data-driven fit method. It exploits the fact that the signal is visible as a clear
bump to estimate the background using interpolation. The method proved to be feasible and results were consistent with respect to the maximum likelihood fit used in the analysis. • The analysis has been published in the paper: “Measurement of WW/WZ → l ν qq ′
production with the hadronically decaying boson reconstructed as one or two jets in pp collisions at 𝑠 = 8 TeV with ATLAS, and constraints on anomalous gauge couplings”. Ref. arXiv:1706.01702 [hep-ex]. Submitted to EPJC.
Other research activities
• I contributed to the monitoring of the Tile Calorimeter PMT response in the years 2013/2014 (advisors: T. Del Prete). I implemented a statistical-based method to monitor PMT response to laser pulses, without the need of a measurement of laser light intensity. The method was designed by the ATLAS Pisa group. I tested it by measuring the time evolution of PMT gain and comparing the results with complementary scans done with a cesium source.
The statistical method proved to be a reliable tool for PMT monitoring. For this task, I also built a functional implementation of the method within the software used for Tile Calorimeter monitoring.
• I worked on laboratory tests aiming to check the statistical method for measuring the PMT gain, thus validating the studies on Tile Calorimeter PMTs. Results confirmed the goodness of the method and were consistent with what measured with other methods in the Tile Calorimeter.
Responsibilities within the ATLAS experiment
• Contact Editor for the publication: “Measurement of WW/WZ→lνqq′ production with the
hadronically decaying boson reconstructed as one or two jets in pp collisions at 𝑠 = 8TeV
with ATLAS, and constraints on anomalous gauge couplings”. (The analysis described in
my PhD thesis.)
• Calorimeter shifter in the ATLAS Control Room. About 20 shifts of 8 hours each in 2016. • Shifter as ATLAS Data Quality Validator. 2014, July 31st – August 14th .
• Qualified as ATLAS author from December 2014
Presentations/posters at conferences and workshops
• “Measurement of WW/WZ production in semileptonic decay channels and search for
anomalous gauge couplings with the ATLAS detector”, on behalf of ATLAS Collaboration.
Alps2017, April 2017. Ref: ATL-PHYS-SLIDE-2017-205 (First public presentation of the analysis)
• “Electroweak processes at Run 2”, invited talk at ‘VII Workshop Italiano sulla fisica pp a LHC’, PoS(PP@LHC2016)016.
• “The upgrade of the laser calibration system for the ATLAS hadron calorimeter TileCal.” Poster, IEEE – Nuclear Science Symposium and Medical Imaging Conference, and
Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors workshop, Seattle USA. Reference: ATL-TILECAL-SLIDE-2014-780
• “The laser calibration system for the ATLAS Tile Calorimeter: upgrade and performance
studies”. 100° Congresso Nazionale della Società Italiana di Fisica. Pisa, September 2014.
• “Standard Model measurements with 2015/2016 data”. Invited talk. X ATLAS Italia Workshop on Physics and Upgrades Milano, February 2015.
• Co-author of two additional review talks on Standard Model single and multi-bosons measurements in ATLAS, XI and XII ATLAS Italia Workshops.
Outreach
