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Luc Pape (1939 – 2021)

Luc Pape
(Image: CERN)

It is with great sadness that we announce that our colleague and friend Luc Pape passed away on 9 April 2021 after a brief illness.

Luc's long, rich career covered all aspects of our field, from the early days of bubble chamber (BC) physics in the 1960s and 1970s to the analysis of CMS data at the LHC.

In the former, he contributed to the development of subtle methods of track reconstruction, measurement and event analysis. He participated in important breakthroughs, such as the first evidence for scaling violation in neutrino interactions at the Big European Bubble Chamber (BEBC) in 1978 and early studies of the structure of the weak neutral currents. Luc developed software that made it possible to identify muons by linking the extrapolated BC tracks to the signals of the external BEBC muon identifier.

Luc’s very strong mathematical background was instrumental in these developments. He acquired deep expertise in software development and always remained at the cutting edge of this field, exploiting ingenious techniques and rigorous methods that he adapted for new endeavours.

At the end of the BC era, Luc was among the experts studying the computing environment of future experiments. Along with his colleagues, he instigated the PAW (Personal Analysis Workstation) ideas.

Luc then joined the DELPHI collaboration. Analysing the needs of the LEP experiments in computing, he was among the first physicists to feel the need to move from shared central computing to distributed farms for large experiments. 

He thus conceived, pushed for and, with motivated collaborators, built and exploited the DELPHI Farm (DELFARM), making it possible to rapidly analyse DELPHI data and produce Data Summary (DST) files for the whole collaboration. Using his strong expertise in the available software tools, Luc progressively improved track analysis, quality checking and event display. DELPHI users will remember TANAGRA (Track ANAlysis and GRAphic package), the backbone of DELANA (DELPHI ANAlysis program), and DELGRA, for event displays.

Luc’s passion for physics never faded. He was open-minded but had a predilection for super-symmetry (SUSY), of which he brilliantly mastered the subtle phenomenology. He became the very active leader of the DELPHI group and later of the whole LEP SUSY group.

After retiring from CERN in 2004, he enjoyed the hospitality of the ETH Zurich group at CMS, to which he brought his expertise on SUSY. Collaborating closely with many young physicists, he introduced the stransverse mass (MT2) method for SUSY research at CMS and pioneered several leptonic and hadronic SUSY analyses. He first convened the CMS SUSY/BSM group (2003-2006), then the SUSY Physics Analysis group (2007-2008), preparing various topological experimentations to be performed with the first LHC collisions. As head of SUSY in the Particle Data group (2000-2012), he helped define SUSY benchmark scenarios within reach of present and future hadron colliders. Comforted by the discovery of a light boson, a necessary feature of SUSY (short of being proof of the theory’s validity), he continued exploring novel analysis methods and strategies to interpret any potential evidence.

We will remember Luc for the exceptional combination of his genuine enthusiasm for physics, his outstanding competence and rigour in analysis, his understanding of technical matters, and his deep concern for young colleagues with whom he interacted beautifully.

Luc had other domains of strong interest, such as cosmology (he had the opportunity to listen to Georges Lemaître himself) as well as African ethnicities and arts and Mesopotamian civilisations. He undertook some quite demanding Himalayan treks with his wife Christine.

We mourn the loss of a most remarkable and rounded physicist, a man of great integrity, devoid of personal ambition, a rich personality, interested in many aspects of life, and a very dear friend.

Our thoughts and deepest sympathy go to Christine and to all Luc’s family and friends.

His friends and colleagues