Walter Oelert, founding spokesperson of COSY-11 and an experimentalist of rare foresight in the study of antimatter, passed away on 25 November 2024.

Walter was born in Dortmund on 14 July 1942. He studied physics in Hamburg and Heidelberg, achieving his diploma on solid-state detectors in 1969 and his doctoral thesis on transfer reactions on samarium isotopes in 1973. He spent the years from 1973 to 1975 working on transfer reactions of rare-earth elements as a postdoc in Pittsburgh under Bernie Cohen, after which he continued his nuclear-physics experiments at the Jülich cyclotron.

With the decision to build the “Cooler Synchrotron” (COSY) at Forschungszentrum Jülich (FZJ), he terminated his work on transfer reactions, summarised it in a review article, and switched to the field of medium-energy physics. At the end of 1985 he conducted a research stay at CERN, contributing to the PS185 and the JETSET (PS202) experiments at the antiproton storage ring LEAR, while also collaborating with Swedish partners at the CELSIUS synchrotron in Uppsala. In 1986 he habilitated at Ruhr University Bochum, where he was granted an APL professorship in 1996.

With the experience gained at CERN, Oelert proposed the construction of the international COSY-11 experiment as spokesperson, leading the way on studies of threshold production with full acceptance for the reaction products. From first data in 1996, COSY-11 operated successfully for 11 years, producing important results in several meson-production channels.

At CERN, Walter proposed the production of antihydrogen in the interaction of the antiproton beam with a xenon cluster target – the last experiment before the shutdown of LEAR. The experiment was performed in 1995, resulting in the production of nine antihydrogen atoms. This result was an important factor in the decision by CERN management to build the antiproton–decelerator (AD). In order to continue antihydrogen studies, he received substantial support from Jülich for a partnership in the new ATRAP experiment aiming for CPT violation studies in antihydrogen spectroscopy.

Walter retired in 2008, but kept active in antiproton activities at the AD for more than 10 years, during which time he was affiliated with the Johannes Gutenberg University of Mainz. He was one of the main driving forces on the way to the extra-low-energy antiproton ring (ELENA), which was finally built within time and financial constraints, and drastically improved the performance of the antimatter experiments. He also received a number of honours, notably the Merentibus Medal of the Jagiellonian University of Kraków, and was elected as an external member of the Polish Academy of Arts and Sciences.

Walter’s personality – driven, competent, visionary, inspiring, open minded and caring – was the type of glue that made proactive, successful and happy collaborations.

Grigory Vladimirovich Domogatsky, spokesman of the Baikal Neutrino Telescope project, passed away on 17 December 2024 at the age of 83.

Born in Moscow in 1941, Domogatsky obtained his PhD in 1970 from Moscow Lomonosov University and then worked at the Moscow Lebedev Institute. There, he studied the processes of the interaction of low-energy neutrinos with matter and neutrino emission during the gravitational collapse of stars. His work was essential for defining the scientific programme of the Baksan Neutrino Observatory. Already at that time, he had put forward the idea of a network of underground detectors to register neutrinos from supernovae, a programme realised decades later by the current SuperNova Early Warning System, SNEWS. Together with his co-author Dmitry Nadyozhin, he showed that neutrinos released in star collapses are drivers in the formation of isotopes such as Li-7, Be-8 and B-11 in the supernova shell, and that these processes play an important role in cosmic nucleosynthesis.

In 1980 Domogatsky obtained his doctor of science (equivalent to the Western habilitation) and in the same year became the head of the newly founded Laboratory of Neutrino Astrophysics at High Energies at the Institute for Nuclear Research of the Russian Academy of Sciences, INR RAS. The central goal of this laboratory was, and is, the construction of an underwater neutrino telescope in Lake Baikal, a task to which he devoted all his life from that point on. He created a team of enthusiastic young experimentalists, starting site explorations in the following year and obtaining first physics results with test configurations later in the 1980s. At the end of the 1980s, the plan for a neutrino telescope comprising about 200 photomultipliers (NT200) was born, and realised together with German collaborators in the 1990s. The economic crisis following the breakdown of the Soviet Union would surely have ended the project if not for Domogatsky’s unshakable will and strong leadership. With the partial configuration of the project deployed in 1994, first neutrino candidates were identified in 1996: the proof of concept for underwater neutrino telescopes had been delivered.

He shaped the image of the INR RAS and the field of neutrino astronomy

NT200 was shut down a decade ago, by which time a new cubic-kilometre telescope in Lake Baikal was already under construction. This project was christened Baikal–GVD, with GVD standing for gigaton volume telescope, though these letters could equally well denote Domogatsky’s initials. Thus far it has reached about half of the size of the IceCube neutrino telescope at the South Pole.

Domogatsky was born to a family of artists and was surrounded by an artistic atmosphere whilst growing up. His grandfather was a famous sculptor, his father a painter, woodcrafter and book illustrator. His brother followed in his father’s footsteps, while Grigory himself married Svetlana, an art historian. He possessed an outstanding literary, historical and artistic education, and all who met him were struck by his knowledge, his old-fashioned noblesse and his intellectual charm.

Domogatsky was a corresponding member of the Russian Academy of Sciences and the recipient of many prestigious awards, most notably the Bruno Pontecorvo Prize and the Pavel Cherenkov Prize. With his leadership in the Baikal project, Grigory Domogatsky shaped the scientific image of the INR RAS and the field of neutrino astronomy. He will be remembered as a carefully weighing scientist, as a person of incredible stamina, and as the unforgettable father figure of the Baikal project.

Elena Accomando, a distinguished collider phenomenologist, passed away on 7 January 2025.

Elena received her laurea in physics from the Sapienza University of Rome in 1993, followed by a PhD from the University of Torino in 1997. Her early career included postdoctoral positions at Texas A&M University and the Paul Scherrer Institute, as well as a staff position at the University of Torino. In 2009 she joined the University of Southampton as a lecturer, earning promotions to associate professor in 2018 and professor in 2022.

Elena’s research focused on the theory and phenomenology of particle physics at colliders, searching for new forces and exotic supersymmetric particles at the Large Hadron Collider. She explored a wide range of Beyond the Standard Model (BSM) scenarios at current and future colliders. Her work included studies of new gauge bosons such as the Z′, extra-dimensional models, and CP-violating effects in BSM frameworks, as well as dark-matter scattering on nuclei and quantum corrections to vector-boson scattering. She was also one of the authors of “WPHACT”, a Monte Carlo event generator developed for four-fermion physics at electron–positron colliders, which remains a valuable tool for precision studies. Elena investigated novel signatures in decays of the Higgs boson, aiming to uncover deviations from Standard Model expectations, and was known for connecting theory with experimental applications, proposing phenomenological strategies that were both realistic and impactful. She was well known as a research collaborator at CERN and other international institutions.

She authored the WPHACT Monte Carlo event generator that remains a valuable tool for precision studies

Elena played an integral role in shaping the academic community at Southampton and was greatly admired as a teacher. Her remarkable professional achievements were paralleled by strength and optimism in the face of adversity. Despite her long illness, she remained a positive presence, planning ahead for her work and her family. Her colleagues and students remember her as a brilliant scientist, an inspiring mentor and a warm and compassionate person. She will also be missed by her longstanding colleagues from the CMS collaboration at Rutherford Appleton Laboratory.

Elena is survived by her devoted husband, Francesco, and their two daughters.

Shoroku Ohnuma, who made significant contributions to accelerator physics in the US and Japan, passed away on 4 February 2024, at the age of 95.

Born on 19 April 1928, in Akita Prefecture, Japan, Ohnuma graduated from the University of Tokyo’s Physics Department in 1950. After studying with Yoichiro Nambu at Osaka University, he came to the US as a Fulbright scholar in 1953, obtaining his doctorate from the University of Rochester in 1956. He maintained a lifelong friendship with neutrino astrophysicist Masatoshi Koshiba, who received his degree from Rochester in the same period. A photo published in the Japanese national newspaper Asahi Shimbun shows him with Koshiba, Richard Feynman and Nambu when the latter won the Nobel Prize in Physics – Ohnuma would often joke that he was the only one pictured who did not win a Nobel.

Ohnuma spent three years doing research at Yale University before returning to Japan to teach at Waseda University. In 1962 he returned to the US with his wife and infant daughter Keiko to work on linear accelerators at Yale. In 1970 he joined the Fermi National Accelerator Laboratory (FNAL), where he contributed significantly to the completion of the Tevatron before moving to the University of Houston in 1986, where he worked on the Superconducting Super Collider (SSC). While he claimed to have moved to Texas because his work at FNAL was done, he must have had high hopes for the SSC, which the first Bush administration slated to be built in Dallas in 1989. Young researchers who worked with him, including me, made up an energetic but inexperienced working team of accelerator researchers. With many FNAL-linked people such as Helen Edwards in the leadership of SSC, we frequently invited professor Ohnuma to Dallas to review the overall design. He was a mentor to me for more than 35 years after our work together at the Texas Accelerator Center in 1988.

Ohnuma reviewed accelerator designs and educated students and young researchers in the US and Japan

After Congress cancelled the SSC in 1993, Ohnuma continued his research at the University of Houston until 1999. Starting in the late 1990s, he visited the JHF, later J-PARC, accelerator group led by Yoshiharu Mori at the University of Tokyo’s Institute for Nuclear Study almost every year. As a member of JHF’s first International Advisory Committee, he reviewed the accelerator design and educated students and young researchers, whom he considered his grandchildren. Indeed, his guidance had grown gentler and more grandfatherly.

In 2000, in semi-retirement, Ohnuma settled at the University of Hawaii, where he continued to frequent the campus most weekdays until his death. Even after the loss of his wife in 2021, he continued walking every day, taking a bus to the university, doing volunteer work at a senior facility, and visiting the Buddhist temple every Sunday. His interest in Zen Buddhism had grown after retirement, and he resolved to copy the Heart Sutra a thousand times on rice paper, with the sumi brush and ink prepared from scratch. We were entertained by his panic at having nearly achieved his goal too soon before his death. The Heart Sutra is a foundational text in Zen Buddhism, chanted on every formal occasion. Undertaking to copy it 1000 times exemplified his considerable tenacity and dedication. Whatever he undertook in the way of study, he was unhurried and unworried, optimistic and cheerful, and persistent.