Logbook Summer School 2016
Top Mass Precision Measurements at the FCC-ee

Week 01

Goal of the work

  • From the Cross section scan as a function of the energy extract Top mass, width, Yukawa coupling, \(\alpha_s\).

  • Study the effeciency and the background level as a function of the energy

  • What detector features are most important? (like b-tagging, momentum resolution...which precision do we need?)

  • Study how much luminosity do we need to scan the cross section and how many point do we need to get

  • Study how to split the luminosity available at the \(4^{th}\) run between the top mass and the top couplings

What we need to achieve this goal

  • Write down the heppy script to create ntuple and the selection script to reject background.

  • Generate all the events (signal and bg).

What we did during this week

  • fcc-pythia8 is ready to hadronize lhe files (test with madgraph: ok!, wait for whizard)

  • completed the missing energy class in the heppy framework

  • a lot of knowledge concerning the FCC software, but not enough!

Next steps

  • Make whizard working

  • Write down an heppy script which finds at least the iso-lepton, the missing energy and reconstruct the w-lep (and the tops?)

  • Writing down the b-tagging algorithm

  • Understand how to deal with the beam energy spread (put it inside whizard, but how to take it in account during the calculation of the missing energy-momentum?)

Week 02

Monday

  • I understood how to pick the recoil (missing energy, there is no so big difference).

  • I need to understand how to create my analyzer to build resonance.

  • I don’t understand how the b-tagging is implemented for the moment, and how can I do to implement the b-tagging algorithm because it doesn’t seem that we have the parameters of the track.

  • Last year we got our ntuples from the reconstruction and then we create new ntuples with useful variables, and used topConstrainer (it’s something done by Patrick, so how to deal with now?)

  • In my opinion we must put the lepton smearing inside papas.

  • It seems that the energy sum in the isolation doesn’t work.

Tuesday

  • Understood how to create my own analyzers.

  • Isolation cut: how to do that?

  • How fast jet cluster the particles?

  • Construct best tops and w bosons: w_lep is constrained, but to find the best combination I decide to minimize the quantity: \( \sum (m_{res} - m_{pdg})^2\), where the sum goes on w_had, top_lep and top_had

  • Patrizia managed to compile Whizard: let’s think about the theory and how to run it on lxplus.

What to do:

  • Some question for Patrick

  • Understand how to redo the analysis (isolation, photon recovery, cut...)

  • Lepton smearing? Look at Delphes!

  • Kinematics: fit? constraint?

  • Finding the track parameters and the generator info in the ntuples

Wednesday - Thursday - Friday

  • Understood the question about fit and constrain

  • Written an analyzer that call TopConstrainer and search for the best jet combination for each event; unfortunately the analyzer is really slow, and it processes at the moment only 2 events/second.

  • Attended the visit at the antiproton deceleration center and the CMG introduction meeting.

Week end: to do

  • Useful program from Giovanni Petrucciani to plot and useful hints with heppy: LEARN them!

  • Understand with Giovanni Franzoni what is the best way to simulate my events and process them.

  • Study tracks and b-tagging paper.

  • Try to understand what to do with the b-tagging algorithm, and how to study efficiency and purity varying the cut for instance and of course the distribution for signal and bg (I could generate for instance \( ZZ \rightarrow q \bar q\) for each species of quarks and test the b-tagging algorithm, and then try to understand how to deal with the \(t \bar t\) system.

  • Moreover I NEED to understand how can I get the MC info from the simulation.

  • And try to install Whizard on lxplus.

Doubts

  • Beamstralung

  • lepton smearing?

  • Photons recovery?

  • Isolation?

  • SOLVED: The tops don’t have necessary the same mass, they could have a different slightly different one.

  • How to deal with the fact that the W and the Top have a non-zero width?

Week end: results

  • Understood that the IP calculation in the Helix class is not what we need, and got the idea to write the new one.

  • Almost read all the b-tagging paper.