Lucia Perrini
Former member
PhD student in CP3 from January 2012 to October 2015
Past projects
Hide past projects.

I am involved in the following research directions:

Reconstruction and identification of hadronic tau decays with CMS at the LHC

The current experimental program of the CMS experiment contains many analyses which look for a Formula: 0 lepton in the final state. The decay of Higgs boson into Formula: 1 leptons is one of the few decay channels which can be used to observe or exclude a low mass neutral scalar boson that is predicted by the Standard Model as well as by many Beyond SM scenarios. Additionally, the observation of a charged Higgs boson, which for masses below 200 GeV preferably decays into a Formula: 2 lepton and a neutrino, would represent a unique clue to both the origin of mass and the deeper symmetries in Nature.
The Formula: 3 lepton can be useful also in many other analyses beyond the Higgs sector, e.g. to test the lepton/flavour universality.

Being the heaviest lepton, Formula: 4 can decay either to Formula: 5 or electron (``leptonic Formula: 6'') or to lighter hadrons (``hadronic Formula: 7''). Most of the Formula: 8 leptons decay hadronically (65 %). In hadronic decays, there is an odd number of charged hadrons possibly accompanied by neutral hadrons (due to charge conservation), forming together so-called Formula: 9 jet. Finally, there is always at least one neutrino (two for leptonic modes) among the Formula: 10 decay products.

Given that bulk of Formula: 11 decays are non-leptonic, the efficient reconstruction and identification of Formula: 12 jets is of crucial importance for the CMS physics program.

At CMS, the Formula: 13 decay products are reconstructed from Particle Flow (PF) objects. In the PF approach, the information from all sub-detectors is combined to identify and reconstruct all particles from collision, namely charged and neutral hadrons, photons, muons and electrons. The Formula: 14 reconstruction starts from jets.

The main reconstruction algorithm at CMS is "Hadron plus strips" (HPS). It combines PF electromagnetic particles into strips (due to broadening of calorimeter depositions from photon conversions) in order to reconstruct Formula: 15 candidates. Those are combined with charged hadrons to reconstruct visible Formula: 16 decay products.

Several identification criteria are applied to the Formula: 17 candidates: isolation (how much momentum is carried by jet constituents that cannot be associated with Formula: 18 decay products) and rejection against electrons and muons. All discriminators exist in cut- or MVA-based form and have several working points with different values of Formula: 19 reconstruction efficiency and rejection against fake Formula: 20 candidates.

The aim of this project is to maintain and improve the performance of the CMS tau reconstruction and identification algorithms.

Publications in CP3
All my publications on Inspire


Reconstruction and identification of τ lepton decays to hadrons and ν$_τ$ at CMS
Khachatryan, Vardan and others
[Abstract] [PDF] [Journal]
Refereed paper. 6th October.
Search for Neutral Resonances Decaying into a Z Boson and a Pair of b Jets or Tau Leptons
CMS collaboration
[Abstract] [PDF] [Journal] [Full text] Published in Phys. Lett. B 759 (2016) 369
Refereed paper. 28th April.
Summary results of high mass BSM Higgs searches using CMS run-I data
CMS Collaboration
[Full text] CMS Physics Analysis Summary CMS-PAS-HIG-16-007,
Public experimental note. 22nd April.


Tau reconstruction and identification in CMS during LHC run 1
CMS Collaboration
[Full text]
Public experimental note. 1st December.
Search for H/A decaying into Z and A/H, with Z-->ll and A/H-->bb or A/H-->tau tau
CMS Collaboration
[Full text] CMS-PAS-HIG-15-001
Public experimental note. 1st December.


Evidence for the 125 GeV Higgs boson decaying to a pair of tau leptons
CMS Collaboration
[Abstract] [PDF] [Journal]
Refereed paper. 1st July.
Evidence for the direct decay of the 125 GeV Higgs boson to fermions
Chatrchyan, Serguei and others
[Abstract] [PDF] [Journal] Subjects: High Energy Physics - Experiment (hep-ex)
Journal reference: Nature Physics 10 (2014) 557
DOI: 10.1038/nphys3005
Report number: CMS-HIG-13-033, CERN-PH-EP-2014-004

Refereed paper. 1st July.


Search for the standard model Higgs boson decaying to tau pairs produced in association with a W or Z boson with the CMS experiment in pp collisions at \sqrt{s} = 7 and 8 TeV
CMS Collaboration
[Full text] CMS Physics Analysis Summary, CMS-PAS-HIG-12-053
Public experimental note. 6th May.
Search for the standard model Higgs boson decaying to tau pairs produced in association with a W or Z boson
CMS Collaboration
[Full text] CMS Physics Analysis Summary, CMS-PAS-HIG-12-051
Public experimental note. 6th May.

[UCLouvain] - [SST] [IRMP] - [SC]
Contact : Jérôme de Favereau
Job opportunities EOS be.h : 10 PhD positions
Postdoctoral position: Data Analysis and GTK operation for NA62 experiment
Postodoctoral position in precision and BSM Phenomenology
Postdoctoral Position in Precision Computations for the LHC