Contact
Name
Giacomo Bruno
Position
Professor
Email
giacomo.brunclouvain.be
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
Phone
+32 10 47 3215
Office
UCL member card
People responsibilities
Research scientists
Andres Tanasijczuk, member since January 2016
Computing support, Grid computing, CMS Remote Analysis Builder software.

Postdocs
Claudio Caputo (IISN), member since April 2017
I am an experimental particle physicist, member of the CMS collaboration. I am particularly interested in precision measurements of the Higgs boson and searches for new physics.

Jessica Prisciandaro (FNRS), member since January 2018

Visitors
Marco Musich, member since June 2015
Experimental particle physicist working with the CMS experiment at the LHC collider of the CERN laboratory. Currently involved in searches for signals of physics beyond the Standard Model and development of detector alignment and calibration techniques.

PhD students
Jože Zobec (UCL-FSR), member since November 2014
I am working on the long-lived exotic particles with the CMS group. My other more technical interest, unrelated to my work is high-performance computing. Appart from that I really do enjoy cooking, singing and playing board games.

Master students
Domitien Bertrand, member since September 2017

Research statement
Giacomo Bruno is an experimental particle physicist doing research with the CMS experiment at the LHC collider of the CERN laboratory.

His current physics interests are in searches for signals of physics beyond the Standard Model and in measurements related to the recently discovered, Higgs-like, 125 GeV boson: di-tau Higgs decay (associated production of standard model Higgs and exotic Higgs particles), massive long-lived charged particles, heavy resonances decaying into leptons, and baryon number violation. He is also involved in the development of some of the basic tools necessary for these physics data analyses like muon momentum measurement, tau identification, particle identification with ionization energy loss, and matrix elements techniques. He is responsible of the Belgian "Tier2" computing project in the context of the World LHC Computing Grid.

For several years he had contributed to the construction of the CMS detector and its related infrastructure. The main contributions were in the following areas: research and development of the RPC gaseous detectors, design of the CMS muon trigger, and CMS software development for online data acquisition, physics data analysis infrastructure and configuration/monitoring/calibration of the silicon strip tracker detector. He has recently joined the silicon strip tracker upgrade effort.
Projects
I am involved in the following research directions:

#### Angular asymmetries in ttW production

We take advantage of the large statistics being recorded by the CMS experiment in Run 2 to launch a systematic study of angular asymmetries in the ttW process, which have a potentially large sensitivity to non-SM effects.
In synergy with the CP3 phenomenology group, we aim at reporting our results in a form that can be easily translated in EFT constraints.

#### Particle Identification with ionization energy loss in the CMS experiment at the LHC

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

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

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

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.

#### The CMS silicon strip tracker upgrade

Development of the "phase II" upgrade for the CMS silicon strip stracker.

More precisely, we are involved in the development of the uTCA-based DAQ system and in the test/validation of the first prototype modules. We take active part to the various test-beam campaigns (CERN, DESY, ...)

This activity will potentially make use of the cyclotron of UCL, the probe stations and the SYCOC setup (SYstem de mesure de COllection de Charge) to test the response to laser light, radioactive sources and beams.

The final goal is to take a leading role in the construction of part of the CMS Phase-II tracker.

External collaborators: CRC and CMS collaboration.

#### World LHC Computing Grid: the Belgian Tier2 project

The World LHC Computing GRID (WLCG) is the worldwide distributed computing infrastructure controlled by software middleware that allows a seamless usage of shared storage and computing resources.

About 10 PBytes of data are produced every year by the experiments running at the LHC collider. This data must be processed (iterative and refined calibration and analysis) by a large scientific community that is widely distributed geographically.

Instead of concentrating all necessary computing resources in a single location, the LHC experiments have decided to set-up a network of computing centres distributed all over the world.

The overall WLCG computing resources needed by the CMS experiment alone in 2016 amount to about 1500 kHepSpec06 of computing power, 90 PB of disk storage and 150 PB of tape storage. Working in the context of the WLCG translates into seamless access to shared computing and storage resources. End users do not need to know where their applications run. The choice is made by the underlying WLCG software on the basis of availability of resources, demands of the user application (CPU, input and output data,..) and privileges owned by the user.

Back in 2005 UCL proposed the WLCG Belgian Tier2 project that would involve the 6 Belgian Universities involved in CMS. The Tier2 project consists of contributing to the WLCG by building two computing centres, one at UCL and one at the IIHE (ULB/VUB).

The UCL site of the WLCG Belgian Tier2 is deployed in a dedicated room close to the cyclotron control room of the IRMP Institute and is currently a fully functional component of the WLCG.

The UCL Belgian Tier2 project also aims to integrate, bring on the GRID, and share resources with other scientific computing projects. The projects currently integrated in the UCL computing cluster are the following: MadGraph/MadEvent, NA62 and Cosmology.

External collaborators: CISM (UCL), Pascal Vanlaer (Belgium, ULB), Lyon computing centre, CERN computing centre.

Show past projects.
Publications in CP3
Showing 5 publications over 48. Show all publications.
All my publications on Inspire

#### 2018

Search for a heavy scalar boson decaying into a pair of Z bosons in the 2ℓ2ν final state
CMS Collaboration

Public experimental note. 5th March.
Search for a new scalar resonance decaying to a pair of Z bosons in proton-proton collisions at $\sqrt(s) =$ 13 TeV
CMS Collaboration

Public experimental note. 5th March.

#### 2017

The Phase-2 Upgrade of the CMS Tracker
CMS collaboration
CERN-LHCC-2017-009 ; CMS-TDR-014
Refereed paper. 13th December.

#### 2016

Search for long-lived charged particles in proton-proton collisions at sqrt(s) = 13 TeV
Khachatryan, Vardan and others
[Abstract] [PDF] [Journal] Submitted to Phys. Rev. D
6th October.
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.

Contact : Jérôme de Favereau