exotic atoms and nuclei

2008 Nishina Memorial Prize -

Study of antiprotonic helium atoms

Written on November 13, 2008, at Eilat, Israel, Ryu Hayano

Nishina Memorial Prize - It is a great honor for me to receive the 2008 Nishina Memorial Prize for the study of antiprotonic helium atoms, work done since 1997This is when we formed the collaboration, and submitted a proposal to CERN. We started to take data in 2001. with my ASACUSA collaborators at CERN's antiproton decelerator facility. The Nishina Memorial Foundation was established in 1955 to commemorate Dr. Yoshio Nishina (1890-1951), the father of atomic & subatomic physics in Japan, whose name is well known from the Klein-Nishina formula in Compton scattering. The prize, awarded annually by the Foundation, is the most prestigious physics award in JapanAmong the recipients are the Nobel laureates Esaki, Koshiba, Kobayashi & Maskawa..

Weighing the antiproton - Transition frequencies of antiprotonic helium atoms depend on the properties of the antiproton. Measuring them therefore determines these properties with precision commensurate with that of the measuring technique, which for laser spectroscopy can be extremely high. This has enabled us, among other things, to 'weigh' the antiproton, resulting in the most precise value to date for the antiproton-to-electron mass ratio -- so precise in fact that our value now contributes to the "2006 CODATA recommended values" of fundamental physics constantsSection 4 of P.J. Mohr, B.N. Taylor and D.B. Newell, "CODATA recommended values of the fundamental physical constants: 2006", Rev. Mod. Phys. 80, 633 (2008) reads: "Atomic transition frequencies in hydrogen, deuterium, and antiprotonic helium yield information on the Rydberg constant...."..

curiosity-driven-research (hänsch)

CERN, but not LHC - Although our experiment is done at CERN, it differs enormously from experiments done with the LHC (Large Hadron Collider). The LHC experiments are gigantic, while ours is quite modest both in the 'human-sized' scale of the apparatus and in the number of collaboratorsThe number of coauthors of our paper, Hori et al., Physical Review Letters 96, 243401 (2006), which contributed to the CODATA 2006 values, is twelve.. Moreover It is not just the size which is different, but also the style, as was eloquently depicted by T.W. Hänsch, the 2005 Nobel laureate (see the figure). In goal-oriented research like the LHC experiments, the goal is known to everybody, and has to be conquered at whatever cost. On the other hand curiosity-driven research works quite differently. In our case, we started to work on antiprotonic helium because we wanted to understand the mysterious longevity of antiprotons in helium, and we never at first dreamed of measuring the antiproton mass as precise as the proton mass back then.

Can't thank enough - I cannot thank enough to my long-term ASACUSA collaborators, in particular, Drs. Masaki Hori, Eberhard Widmann and Dezső Horváth, with whom I have recently published a review paper entitled "Antiprotonic helium and CPT invariance" (Reports on Progress in Physics 70, 1995-2065 (2007).). Thanks are also due to Dr. Vladimir Korobov; without his precise calculations, we cannot deduce the antiproton to electron mass ratio from our measured laser-transition frequencies. I would like to thank the two medical doctors, Drs. Nakata and Kohno of Torano-mon hospital, who in 2000 diagnosed (well-differentiated adenocarcinoma) and treated (right upper lobectomy) my lung cancer. Recent CT scans show that my lungs are clean.
I am grateful to my family. It was fortunate that I could convey this news to my father, who has been fighting acute myelogenous leukemia (AML) since last year.