The path of the Physicist

NA3, the beginnings

In 1975 I had completed my studies at Ecole Polytechnique (X) in Paris when I started working in DPhPE (now DAPNIA) in Saclay on the NA3/Lezard experiment. Before that, I had been working for 2 years intermittently on the PS Hyperon experiment, with the X laboratory where I met my Masters in physics : Jacques Lefrançois and Jean Badier. It is with them that I had then the chance to live the very exciting experience of NA3. I also had the chance to meet very interesting friends during these years, the list is too long to be mentionned here, but certainly our spokesman Aldo Michelini (later founder of OPAL) was an outstanding physicist and the most human person one can imagine. Of course I don't forget Olivier Callot who was another student in this experiment, coming as well from the hyperons.

We started studying hadronic production of muon pairs with a beam dump setup and many important results were produced:

Structure function of several hadrons (p,pbar, pi, K)
Production of Upsilon from pion beams
Discovery of the "K" factor (QCD corrections to the Born cross-section of Drell-Yan processes). Its name was chosen as "K" at one of our meetings without us noticing this was the initial of one of the founders of the experiment W.Kienzle and for a while it was the "Kienzle-factor"!
Hadronic Production of J/Psi (this was the subject of my Doctorate Thesis I obtained in 1983). Analysing the A dependence of the cross-section, a peculiar dependence with the rapidity was observed, interpreted as a diffractive production mechanism.

We then moved to single photon hadronic production, for which we were pionneering the field, quickly followed by more performant detectors. We completed the experimental program of NA3 in 1984 with a search for light gluinos, using a beam dump hadronic experiment in which the dump was followed by a vacuum decay tank in order to observe the decay of WIMPs. But unfortunately only a large number of strange particles (close to a million K0s, a even a few Omega-) were observed, allowing a tuning of hadronic shower MC programs.

DELPHI...

I started working in DELPHI in 1984. I proposed in 1985 with my Saclay colleagues the concept of Crate Processors. Originally foreseen for the TPC, the FIP processors I contributed to define have been used as the unique DELPHI Fastbus processor.

Together with C.Story of Oxford, I designed the Fastbus readout system in 1986/87, using SASD techniques. I participated as well in the definition of many parts of the online system (trigger decision and control units, slow control strategy, online software, ...).

In 1988 I implemented the CP software and supervised the DAS commissioning in 1989. I took over the LES software responsibility from R.Lucock in 1990 and part of the VAX-VMS software after Michel Jonker's departure in 1992.

Since 1992 I have been Project Leader for DAS software. I have been member of the DELPHI executive committee (DEC) from May 1996 to May 1998. I was since the beginning of 1997 Project Leader for the both DAS hardware and software. Since 1998, I am a member of the DELPHI coordination. Since January 1999, I am Group Leader of the EP/DEL group and responsible of the DELPHI CERN Team.

In Spring 2000, I launched with my TPC colleagues a task force for understanding the origin of the TPC distortions. The new method for computing these distortions has been implemented by E.Piotto. As from the end of LEP data taking, I defined a procedure for measuring the TPC drift velocity as a function of time with a relative precision of the order of 10^-4. Details on this procedure and results can be found here.

LHCb

Since May 2001, I am a member of the LHCb collaboration. I have been the LHCb Computing Group leader from 2002 to 2012.

I have been following the progress of the Data Acquisition (DAQ) and Experiment Control System (ECS) design and gave advice for the writing of the Online TDR.

As from autumn 2001, I had the responsibility of Physics Software Coordinator in LHCb. It consisted in linking software activities (mainly offline) with physics (analysis, high level triggers, simulation etc...). I participate in most offline computing meetings, dealing with the main software projects related with physics: simulation (Gauss), reconstruction (Brunel), physics analysis (DaVinci) and the LHCb framework Gaudi . In 2002, these packages made their transition from fortran based algorithms to C++, and the computing group was setting up the LHCb Event Model . One of my tasks was to make sure that the actual implementation by subdetector groups of this event model is suitable, and that the guidelines are also suitable for being used by the subdetctor groups. Based on this generic event model, an LHCb Physics Event Model was developped to be used in DaVinci.

I have also been involved from the beginning in the LHCb Distributed Computing activities, using the Worldwide LHC Computing Grid as LHCb representative to various management bodies. I was in 2005 one of the main authors of the LHCb Computing Technical Design Report.

From 2007 to 2010, I have been the LHCb Computing Project Leader, and then the deputy project leader for 2 years. I am now the LHCb Distributed Computing Coordinator and I am still representing the LHCb collaboration is the WLCG management bodies.

The LHCb Distributed Computing is based on a Grid Interware called DIRACthat is the core part of the LHCb Grid Solution LHCbDirac, of which I am also one of the developers. I am leading the Data Management developments in LHCbDirac and Dirac, and in charge of the data management operational aspects. I am assisting the Computing Project Leader in the coordination of computing resources.