In the beginning Michel came to SLAC as a graduate student on leave from LAL, 1967 thru 1969, working with Bob Mozeley and his group on the SLAC Streamer Chamber, studying meson photoproduction using an 18 GeV bremmstrahlung beam. The experiment observed the rho and omega vector mesons, and found a signal for the production of the radial excitation of the rho at 1600 Mev. On his return to LAL, Michel worked at CERN with colleagues from LAL and Ecole Polytechnique, joining the Lundby group on extensive studies of elastic scattering.

…. coming back to SLAC I was fortunate to recruit Michel to come join me at SLAC in 1971 as an Assistant Professor. We worked together using r.f. separated hadron beams at SLAC. The main group effort was in studying meson spectroscopy, with emphasis on strange quark spectroscopy. Michel initiated a parallel program of study on elastic scattering, while joining in our group’s work as a colleague. He was promoted to Assoc. Prof. in 1975, but chose to return to France, when a very good opportunity at University of Paris opened up.

…. In joining SLAC Gp B, Michel …. Initiated studies of elastic, and quasi-elastic scattering, and generally probing diffractive processes. His program can be characterized by observation of forward structure in elastic scattering, study of the energy dependence, comparison of particle and anti-particle scattering, and measurement of the real part of the scattering amplitude. These goals were beautifully accomplished. He contributed an elegant evolution of our spectrometer to study meson spectroscopy, so he could take high statistics data on particle and antiparticle scattering at 6 GeV, 10 GeV and 14 GeV, and improve some of our hardware. He also worked on phenomenological analysis of the geometrical structure of the nucleon, using his and other data, wrote theory papers with Haim Harari and Gordon Kane.

…. his colleagues in Group B at SLAC

….. at SLAC Michel needed some new instrumentation built for his elastic scattering experiment, specifically better measurements of the incoming and outgoing scattered particles. He partnered our detector scientist, Steve Shapiro, in the design, building and commissioning of those devices.

….. his instrumentalist phase The SLAC two mile electron linear accelerator is a very hostile environment for a counting experiment – ………. as is well known at LAL ! High power beams, with a burst of electrons modulated at 3000 Mhz for the full 1.5 microsec linac pulse, at 180 rep rate – about 1/1000 duty cycle ! Our experiments had to design for 10 to 20 Mhz instantaneous data rates.

….. his instrumentalist phase MWPC chambers to measure positions to microns, in 10 – 20 MHz rate environment. 1 mm wire spacing. He worked with Steve again on a novel “plug chamber” for the LASS spectrometer, where these small devices, 25 cms by 25 cms, with 1 mm wire spacing, on very large frames that fit snuggly inside the LASS s/c solenoid – so 2 m diameter frames. They were mounted together with the full aperture PC’s, that had their center area deadened, and were wound with 2 mm wire spacing.

Beam chamber

A LASS MWPC with full coverage and a central plug chamber package

cathode – anode ambiguity resolving

… this ‘instrumentalist phase’, and the next step in his career … These devices worked very well, for his own elastic scattering experiment, for the group’s meson spectroscopy studies, and for the LASS studies that followed. He carried that experience with him into the CELLO experiment at DESY, where he and Jean- Jacques Veillet created similar hardware relevant to that experimental program.

… also in play during those years... Studies of meson spectroscopy with r f separated beams at SLAC. Needed evolution of new kind of detector, in a very unpleasant environment with tiny duty cycle. Early version, only a large aperture magnet and a forward wire chamber spectrometer.

…. and on meson spectroscopy Discovery of new meson states – * Axial mesons K (1270) and K (1400) with spin-parity 1 ++ and 1+- * Spin 3 excitation of K star - K (1800) * Excited kaon – a strange psuedo-scalar radial excitation of the K meson – K (1400)

…. his instrumentation went on into LASS The full 4 pi spectrometer – LASS – was a high data rate, digital bubble chamber, studying strange quark spectroscopy. Uncovered the full radial, and orbital, excitation spectra of the strange quark states for three to four level of excitation in both quantum numbers.

LASS

The magnitude, (a), and the phase, (b), of the S-wave and P-wave amplitudes in the mass region below 1.84 GeV/c 2.

Valued Family Friendship. We have enjoyed good family friendship with the Davier family for almost 40 years; They have two daughters and six grand-children, while we had three boys, and a dog – always a dog – (a border collie). One of Doreen’s fondest memories, before her own grand-children arrived, was daily brushing the beautiful long hair of Eve and Diane, when their Mum and Dad had gone back to France on the death of Francoise’s father. We treasure their friendship, enjoyed visiting their home and garden and wish the entire family all the best for the future.

The Davier Family

The Leith Family … then.

The Leith Family … now.

Finally, we have a message from our “ big guns”, who have sent a video greeting to Michel

The end

Back-up

… Photo from the Steamer Chamber

A LASS MWPC with full coverage and a central plug chamber package

….. the next phase …. He carried that experience with him into the CELLO experiment at DESY, where he and Jean-Jacques Veillet created similar hardware relevant to that experimental program.

Elastic scattering experiment

Meson spectroscopy experiment

The SLAC Streamer Chamber

... an interesting development – his diving into instrumentation Developed instrumentation for the elastic scattering experiment, which was also required for the high data rate environment of the meson spectroscopy program – the challenges were … # the SLAC linac intrinsic duty cycle # counting in ten megahertz environment # 1 mm wire spacing MWPC’s # low mass construction