Contact
Name
Claudio Caputo

Position
Postdoc
Funding: IISN
Member since April 2017

Email
claudio.caputo@uclouvain.be

Address
Centre for Cosmology, Particle Physics and Phenomenology - CP3
Université catholique de Louvain
2, Chemin du Cyclotron - Box L7.01.05
B-1348 Louvain-la-Neuve
Belgium

Office
E.164

UCL member card
http://www.uclouvain.be/claudio.caputo
Projects
Research directions:
Data analysis in HEP experiments
Detector commissioning, operation and data processing

Experiments and collaborations:
CMS

Active projects
Particle Identification with ionization energy loss in the CMS experiment at the LHC
Giacomo Bruno, Claudio Caputo, Jessica Prisciandaro, Angela Taliercio, Jože Zobec

The CMS detector at the LHC can be used to identify particles via the measurement of their ionization energy loss. The sub-detectors that have provided so far useful information for this experimental technique are the silicon strip tracker and the pixel detectors. Identification of low momentum hadrons and detection of new exotic massive long-lived charged particles have all benefited from this experimental method. Members of UCL pioneered this technique in the early LHC times and have been developing the tools for its use and calibration. Since 2010 particle identification with ionization energy loss has been the basis of the CMS inclusive search for new massive long-lived charged particles, which has been providing the most stringent and model-independent limits existing to date on any model of new physics predicting such particles.

External collaborators: CMS collaboration.
Search for Higgs bosons in the ll tau tau final state with the CMS experiment at the LHC
Domitien Bertrand, Giacomo Bruno, Claudio Caputo, Marco Musich, Jessica Prisciandaro, Angela Taliercio

A resonance consistent with the stanadard model Higgs boson with mass of about 125 GeV was discovered in 2012 by the CMS and ATLAS experiments at the LHC. Using the available dataset (2011+2012 LHC runs) evidence was later found of the existence of the SM-predicted decay into a pair of tau leptons. The CP3 Louvain group has been involved in the channel where the Higgs boson is produced in association with the Z boson and decays into a pair of tau leptons.

A search for additional Higgs bosons in the general framework of models with two Higgs doublets (2HDM) was then performed by the same CP3 group using the same final state and the full Run-1 data. Models with two Higgs doublets feature a pseudoscalar boson, A, two charged scalars (H+-) and two neutral (h0 and H0) scalars, one of which is identified with the 125 GeV SM-like Higgs resonance. In some scenarios the most favored decay chain for the discovery of the additional neutral bosons is H0-->ZA-->llττ (or llbb). The search was carried out in collaboration with another group in CP3 who looks at the llbb final state.

An update of both the SM search and the exotic one is expected using the Run-2 dataset using more advanced techniques and by adding the llee and llmumu channels.
Search for long-lived heavy neutral leptons with CMS
Giacomo Bruno, Claudio Caputo, Marco Musich, Jessica Prisciandaro, Angela Taliercio

Many well motivated new physics extensions of the SM include new particles whose decay width is very small and hence have a decay length which is macroscopic. One very attractive and minimal extension of the standard model is one with right-handed neutrinos with Majorana masses below the electroweak scale (low scale see-saw). This addition is able to generate both the light neutrino masses and the baryon asymmetry of the universe via low scale leptogenesis. In what is probably the most studied model that invokes the low scale seesaw, the Neutrino Minimal Standard Model [2], one of the three right-handed neutrinos is a dark matter candidate. A large allowed region of phase space for right handed neutrinos spans masses between 1 and 50 GeV with corresponding lifetimes (cτ) ranging from 10^3 to 10^-4 m. For higher masses the right handed neutrino basically decays promptly and for lower masses the probability that it decays within the detector volume is virtually zero thus giving rise to missing transverse momentum in the detector. These latter two extreme cases can be captured experimentally by standard searches at the general purpose LHC experiments, while the intermediate case is the natural target of the so-called “displaced” searches, which are highly peculiar and challenging analyses at the LHC in high demand for dedicated data reconstruction tools in order to extend their sensitivity. We intend to search for long-lived sterile neutrinos decaying at displaced vertices into a charged light lepton and hadrons. A fundamental ingredient of this search is the identification of charged tracks emerging from highly displaced vertices.
Search for massive long-lived charged particles with the CMS detector at the LHC
Giacomo Bruno, Claudio Caputo, Marco Musich, Jessica Prisciandaro, Angela Taliercio, Jože Zobec

The CMS detector at the LHC is used to search for yet unobserved heavy (mass >100 GeV/c$^2$), long-lived (lifetime > 1 ns), electrically charged particles, called generically HSCPs.
HSCPs can be distinguished from Standard Model particles by exploiting their unique signature: very high momentum and low velocity. These features are a consequence of their high mass and the relatively limited LHC collision energy. Two experimental techniques are used to identify such hypothetical heavy and low-velocity particles: the measurement of the ionization energy loss rate using the all-silicon tracker detector and the time-of-flight measurement with the muon detectors.

UCL members have developed the ionization energy loss identification technique and have lead the CMS HSCP search since 2010, when the first HSCP paper became one of the first published LHC search papers. Updated results, using the 2011 dataset, were then published followed by a comprehensive paper including also searches for fractional and multiply-charged particles published using the full CMS Run-1 dataset. The results obtained by analysing the 2015 Run 2 data at 13 TeV have also been published.

The analysis, which is very inclusive, doesn't find evidence of HSCP. It currently excludes, among various models, the existence of quasi-stable gluinos, predicted by certain realizations of supersymmetry, and Drell-Yan-produced staus with masses lower than about 1.3 TeV and 350 GeV, respectively. These and the other limits set by the analysis are the most stringent to date. The CMS HSCP papers total to date more than 300 citations.
Publications in CP3
All my publications on Inspire

Number of publications as CP3 member: 1 Download BibTeX

2017

CP3-17-56: The Phase-2 Upgrade of the CMS Tracker
CMS collaboration

[Full text]
CERN-LHCC-2017-009 ; CMS-TDR-014
Refereed paper. December 13.