Dr Francesco Spano

Ph.D., Physics, The University of Chicago, 2004

Laurea, Fisica, Università di Pisa, 1998

I investigate the fundamental properties of nature that are revealed in proton-proton collisions at (Large Hadron Collider at CERN) by analysing the data collected by the ATLAS multi-purpose detector.

As member of the ATLAS collaboration, at present I am studying the properties of the production of the most massive known particle, the Top Quark, produced in the most energetic collisions at LHC.  

I am serving the ATLAS collaboration as the contact for measurement of differential production cross section  for top quarks in the LHCTOP working group, a joint group of members of the LHC multi-purpose experimental collaborations (ATLAS and CMS) and the theory community.

My previous activities were a balance between measuring fundamental properties of physics and measurement of the properties of the detectors that were used to take the data.

For my Ph.D. at the University of Chicago I measured the mass and width of the W boson, the charged mediator of the weak force,  using the full data set collected by the OPAL detector in electron-positron collisions. 

After that I went back to CERN where I was heavily involved in the commissioning of the ATLAS detector to prepare it for data taking. I was actively involved in  the calorimeter commissioning and the analysis of its response to beams of known particles produced by CERN accelerators. I played leading roles in role in determining the strategy for assessing the quality of the data being taken using information from the combined calorimeters. I co-developed a new scheme for the calibrating the response to hadrons of segmented calorimeters like the ATLAS ones.

With the start of ATLAS data-taking in proton-proton collisions at LHC in 2009, I played major roles in the measurement of the properties of the production of top quarks. Initially I co-led the studies for the properties of jets characterising top quark events that supported the first ATLAS measurement of top quark production in 2010.

Then during the evolution of Run1, I co-led the efforts that produced the first measurement of differential cross sections for the production of top-antitop quark pairs using part of the data ATLAS initially collected at the lower center of mass energy of 7 TeV. I was then involved in extending those measurements to the full 7 TeV data-set.

Then I co-led the effort to measure differential distributions using top quark events produced with the very highest momenta using the full data set collected at the higher center of mass energy of 8 TeV and I was involved in the first search for new resonances using very top quark high transverse momenta featuring a new way of For recognising top quarks decaying high transverse momentum top quarks.

As LHC entered Run2 data taking by increasing the center -of-mass energy to 13 TeV, I  contributed to measuring differential cross sections in final states (leptons +jets  and fully hadronic) and in different kinematic regimes (top quarks with low and very high transverse momentum compared tob their mass). In partiuolar I co-led the measurement of differential cross setcion in the  fully hadronic  final state using top quark events produced with the very highest momenta with 36/fb events collected in 2015 and 2016.

In the meanwhile in 2012-2013 I served the ATLAS collaboration as co-convener of the ATLAS group that measures the production cross section for events featuring top-anti-top pairs, the dominant top quark production mode in proton-proton collisions. I also served the ATLAS top group as liaison with the ATLAS Forum on the Statistical techniques for data analysis. I also served the ATLAS UK community as ATLAS UK Top convener from July 2014 to September 2016.

More recently I  contributed to understanding the properties of jets (jet mass) resulting from hadronization of heavy, high transverse momentum objects (top quarks in particularly)  and to using jets information to validate the data as usable for physics analyses.

I am currently leading an effort aimed at  precisely measuring of the top quark mass from double-differential cross sections and contributing to extending measurements of differential cross section for top quark pair production to using all the data collected by ATLAS in LHC pp collisions at 13 TeV.

At present I am focusing my studies  on the properties of the production of the most massive known particle, the top quark, resulting from the most energetic collisions at LHC. Such studies are a crucial element to help us understand why fundamental constituents of matter have such different masses and they are a privileged gateway to new physics beyond the standard model of fundamental interactions. I am particularly concentrating on measuring

• the probabilty to produce top quark pairs as a function of distinctive kinematic variables of the top quark, like the mass of the top and anti-top system and the momentum of the top quark.
• the mass of the top quark, using the sensitivity of the mentioned probability 

The newly found Higgs boson is expected to be maximally coupled to the top quark. This connection gives the most important contribution when the the smallest gravity-related fluctuations  tend to change the Higgs mass  to much larger values than the ones we observe in reality.  New physics is considered necessary to explain why the Higgs particle's mass is stable: a large number of theoretical extensions of the standard model predict the presence of new particles that are "partners " of the top quark which tend to cancel out the top contribution. Measurements that are differential in the kinematic variables of top quarks are sensitive to the presence of the new partners. In fact the "partners" are expected to decay to top quarks in a large number of scenarios, but the probability for their production is small because they will have either very high mass or special features that confine them in a those kinematic regions that we have not yet explored, like top quarks produced with the highest momenta. The partners will then generally modify the expected differential distributions with respect to our standard expectation. I am actively measuring these distributions  to search for the signs of deviations indicating the presence of new physics at energies and distances that were nver explored before. I am now also interested in meausuring the mass of the top quark, the defining property of the quark which makes it really different from all teh outher known particles.

My expertise in Calorimetry, Hadron and Jet calibration supports these endeavours as final states produced with top quarks involve hadrons , leptons and neutrinos for which the full ATLAS detector is at play.  

These efforts combine nicely with my interests in Statistics for High energy physics. particularly I am interested in developing  the use of techniques aimed at producing meausrements that are corrected for detector effects (unfolding). In this way any theoretical prediction can be directly compared with the result   without having to run it thorugh the complex simulation of the full ATLAS detector.