Cristiana Peroni, former team leader of the Torino group of the CMS collaboration, passed away on 19 June 2024.

Peroni obtained her degree in physics in 1974 at the University of Torino. She worked at an experiment on low-energy proton–antiproton collisions at the CERN Proton Synchrotron, before joining the European Muon Collaboration and, later, the New Muon Collaboration. After this, she moved to ZEUS at DESY and then CMS at the LHC, and was appointed full professor at the University of Torino in 2001.

Thanks to Cristiana’s initiative, in collaboration with Fabrizio Gasparini (project manager of the drift-tube project of CMS’s muon system), the Torino group joined the CMS collaboration in the late 1990s. The group took responsibility for the construction of the MB4 muon chambers, together with groups at Padua, Madrid and Aachen, which were responsible for the construction of the MB3, MB2 and MB1 layers of CMS’s drift-tube system, respectively.

At the same time, Cristiana started a collaboration with the JINR–Dubna group led by Igor Golutvin to realise a critical part of the system: the deposition of the field electrodes on the aluminium planes that form the structural element of the chambers. This was a very successful collaboration, in spite of the crucial issues related to complex logistics, which worked extremely well, guaranteeing the construction of the system within the required timeframe. Alongside hardware commitments, the team coordinated by Cristiana took on important roles of responsibility in the physics groups of the collaboration (in particular in the Higgs sector), and soon saw its expansion with the addition and merger of other groups in Torino, which added activities related to the tracker, electromagnetic calorimeter and precision proton spectrometer.

“Cris” was a determined and capable leader, highly appreciated for the attention she always paid to the professional growth of her collaborators, the career development of early-stage researchers, as well as the team building and mutual support that made her group united and coherent.

In the last part of her professional life, Cris turned her attention to research in medical physics, leaving the management of the CMS group to her collaborators, and carrying out research on hadron therapy. In this field, not only did she establish a new course on medical physics at Torino, but she was instrumental to the CNAO hadron-therapy facility in Pavia, which has been treating cancer patients for more than a decade.

Sachio Komamiya, a prominent figure in the Japanese and International Linear Collider communities, passed away on 5 June 2024 at the age of 71.

Born in Yokohama, Japan in 1952, Komamiya graduated from the University of Tokyo in 1976. He remained there as a graduate student, under the mentorship of Masatoshi Koshiba. Komamiya began his diverse international career by proposing an experiment using the PETRA electron–positron collider at DESY in collaboration with Heidelberg University and the University of Manchester. This collaboration led to the JADE experiment. Koshiba’s laboratory took charge of developing the lead–glass electromagnetic shower detector, which operated reliably and contributed to the discovery of gluons.

After obtaining his PhD for his work at DESY, Komamiya took up a postdoc position at the University of Heidelberg, joining the group of Joachim Heintze. He quickly integrated himself into the group and to the JADE collaboration in general, and was one of the first to perform searches for supersymmetric particles – his enthusiasm for this type of analysis earning him the nickname “SachiNo”.

In 1986 Komamiya’s interest in the highest-energy experiments led him to SLAC as a staff physicist. The construction of the SLAC Linear Collider (SLC) – the first linear collider – was underway. The SLC was a single-pass collider that used a linac to accelerate both electrons and positrons, a design that was highly complex. Komamiya worked on developing the arcs that bent the beams at the end of the linac, which was one of the most complicated parts of the machine. Physics measurements at the SLC started in 1988 with the Mark II detector, and in 1990 Komamiya moved to Europe to join the OPAL experiment at the Large Electron Positron Collider.

Komamiya returned to Japan in 1999 and became a director of the International Center for Elementary Particle Physics at the University of Tokyo in 2000. While leading research and experiments there, he led Japan’s high-energy physics community, serving four terms as the chairman of the Japan Association of High Energy Physics and as a Japanese representative for the International Committee for Future Accelerators from 2000. His leadership and extensive international experience have been precious in advancing the International Linear Collider (ILC) project. In December 2012, a technical design report for the ILC was completed. Shortly afterwards, the ILC project was reorganised under the umbrellas of the Linear Collider Collaboration (LCC), led by Lyn Evans for project development, and the Linear Collider Board, which oversaw the LCC’s activity and was chaired by Komamiya.

Komamiya was eager to see the ILC become Japan’s first globally hosted project. He served as a diplomat to advance this vision, and was calm and patient when explaining to others the often-complex relations involved. Sachio thus fulfilled a critical and essential role bridging science and politics – a talent that, alongside his physics expertise, will be sorely missed.

Hans Joachim Specht, one of the founders of ultra-relativistic heavy-ion physics and a pioneering figure in hadron cancer therapy, passed away on 20 May 2024 at the age of 87. A graduate of the University of Munich and ETH Zurich, and full professor at the University of Heidelberg for more than 30 years, his career was distinguished by important contributions across a spectrum of scientific domains.

Hans started his academic career in atomic and nuclear physics in Munich, under the guidance of Heinz Maier-Leibnitz. A highlight was the discovery and precise measurement of shape isomerism in heavy nuclei. His observation of distinct rotational bands in plutonium-240 showed, for the first time, that nuclei can be in a strongly deformed cigar-shaped state shortly before fission, confirming the concept of a “double-humped” fission barrier. In Munich, and later in Heidelberg, he developed several innovative large-scale detectors for fission fragments and reaction products of heavy-ion collisions, becoming one of the leading experimentalists in the new field of heavy-ion physics, with experiments at the MPI for Nuclear Physics in Heidelberg and at the newly founded GSI in Darmstadt.

In the early 1980s, Hans reoriented his research towards the higher energies available at CERN. His contributions and advocacy, alongside a handful of other enthusiastic proponents, were instrumental in establishing CERN’s ultra-relativistic heavy-ion programme at the SPS, which was approved in 1984. He became the spokesperson of a first-generation heavy-ion experiment (Helios/NA34-2), initiator and spokesperson of a second-generation experiment (CERES/NA45), and a crucial supporter of the third-generation ALICE experiment at the LHC.

Hans was a brilliant experimentalist with a keen eye for cutting-edge detector concepts and how to apply them in a minimalistic approach. This was apparent in his masterpiece, the dilepton experiment CERES, which used a “hadron blind” double Cherenkov detector and a specially crafted magnetic field configuration to pick out and measure the rare electrons from the haystack of hadrons.

Initially with CERES, and later as a leading force within NA60, Hans succeeded in detecting, for the first time, thermally produced lepton pairs in heavy-ion collisions; the original discovery with NA45 remains one of the most cited papers from the SPS heavy-ion programme. The high-precision measurements at NA60 of what is arguably one of the most challenging signals (the Planck-like spectrum of thermal radiation at higher masses), and the precise characterisation of the in-medium modification of the ρ meson at lower masses, proved to be crucial in establishing the existence and properties of quark–gluon plasma. The enduring quality and relevance of these measurements remain unsurpassed almost two decades later.

Throughout his career, Hans held numerous positions in the realm of science policy at a variety of German and international research institutes. At CERN, he served as chair of the PSCC committee and as a member of the SPC. He was also a founding member of the first board of directors of the theory institute ECT* in Trento, a place that held special significance for him.

Hans was a brilliant experimentalist with a keen eye for cutting-edge detector concepts

As scientific director of GSI from 1992 to 1999, Hans set the course for the development and application of a groundbreaking innovation in radiation medicine: ion-beam cancer therapy. A pilot project at GSI for the irradiation of tumours with carbon-12 ions successfully treated 450 patients and led to the establishment of the Heidelberg Ion-Beam Therapy Center, the first European ion-beam therapy facility. Reflecting on his achievements, he was most proud of his contributions to ion-beam therapy. Additionally, Hans initiated discussions on the long-term future of GSI, which eventually led to the proposal for the international FAIR facility.

Hans also had a profound interest in the intersection of physics, music and neuroscience, collaborating with Hans-Günter Dosch on understanding perception of music and its physiological bases. This transdisciplinary approach produced highly cited publications on the differences in the auditory cortex between musicians and non-musicians, expanding the boundaries of how we understand the brain and its response to music.

Hans was an outstanding teacher, a prolific mentor, a successful science manager, but foremost, he was someone who profoundly loved physics, with a relentless drive to follow wherever his interests and research would lead him. His frequent and spirited commutes between Heidel­berg and CERN in his iconic green Lotus Elan will be fondly remembered. His critical guidance and profound questions will be deeply missed by all who had the privilege of knowing him.

Werner Beusch, who played a pioneering role in the OMEGA spectrometer at CERN, passed away after a short illness on 4 May 2024.

A student of Paul Scherrer at ETH Zurich, Werner obtained his PhD in 1960 with a thesis on two-photon transitions in barium-137 and moved to CERN, joining the “Groupe Chambre Wilson” (a collaboration of teams from CERN, ETH Zurich and Imperial College London). Around that time, cloud chambers were being replaced with spark chambers. Werner, already very experienced in electronics despite his young age, designed and built the entire trigger system for spark chambers from scratch using discrete components (NIM modules were not yet available at the time!).

In the late 1960s Werner started working on the OMEGA project – a high-aperture electronic spectrometer to be installed on a PS beam line in the West Area. The spectrometer was envisioned to operate as a facility, with a standard suite of detectors that could be complemented by experiment-specific apparatus provided by the individual collaborations. This was achieved by a large (3 m diameter) superconducting magnet equipped with spark chambers, a triggering system and data acquisition. The original programme included missing-mass experiments, the study of baryon-exchange processes and leptonic hyperon decays, and experiments with hyperon beams and with polarised targets. After a few years, interest moved to new topics, such as photoproduction, charm production and QCD studies.

In 1976 the OMEGA spectrometer was moved to its final position in the West Area on a beam line from the newly built SPS. In 1979, under Werner’s supervision, the spectrometer – until then equipped with spark chambers and plumbicon cameras – was instrumented with the new, much faster and higher resolution multi-wire proportional chambers. The refurbished OMEGA quickly became the go-to facility for a wide range of experiments. Over the years, under Werner’s stewardship, the facility was continuously upgraded with new equipment such as drift chambers, ring-imaging Cherenkov detectors, silicon microstrips and silicon pixel detectors (which were deployed at OMEGA for the first time). Triggering and data acquisition were also continuously updated such that, throughout its 25-year lifetime, OMEGA remained at the forefront of technology. It hosted some 50 experiments, with achievements ranging from its essential role in the establishment of non-qq mesons, to the detection of a (so-far unexplained) excess in the production of soft photons, to the observation of clear violations of factorisation in charm hadroproduction. The OMEGA scientific programme culminated in a key contribution to the discovery of quark–gluon plasma (QGP), with the detection of the signature enhancement pattern of strange and multi-strange hadrons in lead–lead collisions.

Werner retired from CERN in 1995, one year before OMEGA was closed, not because it had reached its time (QGP studies, then in full blossom, had to be hastily moved to the North Area), but to make room for an assembly and test facility for the LHC magnets. Throughout its lifetime, Werner truly was the “soul” of the OMEGA experiment, always present and ready to help. Swapping from one layout to the next (and from one experimental group to the next) was the standard way of operating, and Werner and his team had the heavy responsibility of keeping the spectrometer in good shape and guaranteeing a prompt and efficient restart of the experiments. Werner’s kind and thoughtful attitude was key to this and the many other OMEGA successes. His impassioned, matter-of-fact and selfless way of doing science influenced generations of physicists whose careers were forged at OMEGA. Werner coming into the control room and offering a basket of fruits from his garden remains vivid in the memory. We miss him dearly.

Olav Ullaland, a brilliant detector physicist who spent his career at CERN, passed away on 16 June 2024.

Olav obtained his degree in particle physics at the University of Bergen in 1971. After a short period at Rutherford Appleton Laboratory in the UK, he went to CERN as a fellow in 1973, following which he was awarded a staff contract. He worked as a detector physicist at CERN until he retired in 2009, remaining active for several years as an emeritus. One of his last scientific articles dates from 2020.

Alongside detector R&D, Olav participated in several key CERN experiments. For the Split Field Magnet Detector, located at CERN’s Intersecting Storage Rings, he was in charge of the multi-wire proportional chambers and worked on the prototype of a novel electromagnetic calorimeter that was later adopted by the DELPHI experiment.

After contributing to the UA1 upgrade, he was asked to take a leading role in the complex barrel ring-imaging Cherenkov (RICH) project of DELPHI, which was the first attempt to integrate an imaging Cherenkov detector into a cylindrical collider experiment. The challenges were immense, as it was necessary to operate a gas and liquid radiator, together with a photo­sensitive gas, at different temperatures in a confined space. Thanks to Olav’s perseverance and the loyalty he inspired in his team, he was able to bring the apparatus to a level where it could be used in physics analysis, for example in the tagging of strange jets from Z and W decays. This was a critical milestone in the history of RICH detectors.

Around 1997 Olav joined LHCb and became a leader in the international effort to make its two RICH detectors a reality. Thanks to his deep knowledge of the many facets of detector physics and techniques, and his ability to remain calm, he and his team managed to find solutions to potential showstoppers. It is testament to Olav’s efforts that the particle identification system of LHCb works so impressively in the study of CP violation and heavy-flavour rare decays. In addition, Olav was the LHCb resource coordinator for several years, taking impeccable control of delicate LHCb financial matters at the beginning of the experiment operations. His expertise in leading many project reviews and trouble-shooting several wide-ranging detector subsystems was also in high demand both within and outside LHCb.

Olav was a wonderful collaborator. He was passionate in his support of students and fellows, and encouraged young people to give presentations and international talks, always graciously stepping away from the limelight himself. His dedication to student training was highlighted by his running of the CERN summer student programme, with both lectures and laboratory courses.

For Olav, work did not finish at CERN, but would be continued in any possible meeting place. These unconventional settings provided a conducive atmosphere to explore, discuss and challenge new projects and ideas, with the goal of promoting cohesion in a critical, constructive and friendly fashion.

Olav Ullaland was not only an outstanding researcher, but also a unique human being who left a deep impression on all those with whom he came into contact. We will never forget him.

Arnau Brossa Gonzalo, a postdoctoral researcher at the Galician Institute of High Energy Physics (IGFAE) working on the LHCb experiment, died in Santiago on 21 July 2024 following complications from a climbing accident.

Arnau obtained his degree in physics at the University of Barcelona in 2016, specialising in theoretical physics. He continued there for his master’s in astrophysics, particle physics and cosmology, with a thesis on the LHCb experiment.

In 2017 he embarked on his PhD studies in particle physics at the University of Warwick. His thesis, entitled “First observation of B⁰ → D^*(2007)⁰K⁺π^– and B⁰_s → D^*(2007)⁰K^–π⁺ decays in LHCb”, won the Springer Thesis Prize for outstanding PhD research. This was the first LHCb measurement of B decays involving fully reconstructed neutral D^*mesons, which are particularly challenging due to the soft neutral particles emitted in the D^* → Dπ⁰ and D^* → Dγ decays. These modes are nonetheless extremely important to understand as they are backgrounds to a wide range of other studies, including those used for precision measurements of the CKM angle γ.

Following the completion of his PhD, Arnau joined the LHCb group at IGFAE in 2022 to work further on the LHCb experiment, first as a postdoctoral researcher and later as a Juan de la Cierva researcher. He then joined the lepton-flavour-universality group at IGFAE, taking on a leading role in the measurement of the ratios of semileptonic-decay branching fractions to final states with tau leptons relative to muons, denoted R(D) and R(D^*). Arnau had rapidly established himself as an expert in this area, and in early 2024 he had taken on convenership of the LHCb subgroup that was dedicated to this and to similar charged-current lepton-flavour-universality tests.

Arnau’s warmth, kindness, dedication, intelligence and competence will be deeply missed by his many friends at the institute in Santiago and in the LHCb collaboration.