My first contact with Dr. Hannes was about ten years ago during a J-PARC experiment. It was then that Hannes brought his SSD to J-PARC, marking the beginning of our professional relationship. Over the years, I had the opportunity to communicate with him on various occasions, and each time, I was reminded of the qualities that made Hannes truly exceptional.

One of the most striking characteristics of Hannes, as many of his friends and colleagues would agree, was his warm and humble attitude. Despite his profound expertise and accomplishments in the field of physics, he always approached others with kindness and respect. He never hesitated to share his knowledge or offer his support, making him not only a brilliant scientist but also a truly decent human being.

We have lost not just a smart physicist but also a wonderful person who touched the lives of many with his generosity and grace. His presence will be deeply missed, but his legacy will continue to inspire us all.

Dear Hannes, may you rest in peace.

I am deeply saddened by the loss of my dear friend, Hannes-san. I will always cherish the memories of the times we spent together, especially those evenings when we enjoyed a good time together. I only wish we could have shared many more. Many thanks, Hannes-san.

The news of Hannes’ passing leaves me with deep sadness. We are losing not only a great physicist but also an exceptional person. I had the pleasure to work with Hannes at SMI for several years and it is impossible to describe by words how much support, help and knowledge he gave and how many great moments we shared at work and aside from work. Every single moment together with him in the laboratory you could feel his burning passion for what he was doing.

I met him just a few weeks ago when he was already undergoing treatment. Even in these difficult times he was exactly as I had remembered him from our common times at SMI: kind, humorous, always in good mood, interested and curious, full of optimism and extremely passionate about his work, physics and newly upcoming projects.

My sincere condolences to family, friends and colleagues.

Many thanks Hannes, RIP.

Farewell, my dearest friend 

Addio, amico mio!

23^rd of July is one of the most shocking days of m, my beloved friend Hannes Zmeskal passed away.  I talked with him by phone only a few days before – and, as usually, even if he was not well, he told me that he’s doing fine, he’s under treatment and he was looking forward to meet again soon.

 I cannot believe that the last time we met, in December 2023 in Tokyo, would be our final one. I want to remember you just as you were then and all the year I knew you: full of life, joy, and optimism like no one else!

For over 25 years, we were not just colleagues but close friends, sharing countless adventures together. Our friendship was a pillar of my life, and I don’t know how I will go on without you. You were not only an unparalleled physicist but also a kind, joyful, and wonderful-hearted person. Always with a good word, a smile, and an endless optimism, you brought light to every situation, even the most challenging ones.

You were a world-renowned expert in cryogenics, a master of mechanics and radiation detectors, and a true genius in technology. But beyond your professional excellence, it was your humor, your endless curiosity, and your ability to find the beauty in every situation that made you truly unique. You were one of the few who added life to years rather than just years to life.

I remember one of the first times we met, over 25 years ago. You had come from Vienna to Frascati to start working with our group. You were so cheerful and full of energy, and you told me that you planned to take apart our entire apparatus and rebuild it from scratch, down to the smallest details—screws, bolts, everything! I was terrified that you wouldn’t be able to put it back together, so I followed you around, taking notes and making drawings. But I couldn’t keep up; it was too complicated, and my sketches looked like something out of a Picasso painting. You laughed and encouraged me, assuring me that it would all be useful. I was in despair, not understanding any of my notes, but you always had a reassuring word.

You once told me that you had considered becoming a neurosurgeon, but couldn’t stand the sight of blood, so instead, you became the "neurosurgeon" of our most sophisticated equipment—a unique and irreplaceable talent. I could write a book about our adventures: the time our entire experimental apparatus fell, but it was so well-constructed that it didn’t get a scratch; your magical calculations of the gas density we were using; and those fine adjustments that were more art than science—always done by you.

Hannes, your spirit, your endless curiosity, and your ability to save the day, time and time again, will be deeply missed by everyone who knew you. You were loved by all—whether in Vienna, Japan, Frascati, or anywhere else in the world. Part of me is gone with you.

RIP, dear friend.

It is extremely sad news to learn of the passing away  of Dr Johann Zmeskal. Apart from being an internationally excellent scientist, covering with his extremely valuable research, a broad spectrum of interests, from fundamental physics analysis to instrumentation, he has also been an extremely nice and kind person. A very valuable and cultured colleague, who will be greatly missed. I have had the opportunity of appreciating first hand his scientific excellence and capabilities and skills during my membership in the scientific advisory board of the Stefan Meyer Institute.

This was very sad news, indeed: with Hannes Zmeskal, we lost a great physicist, an instrumentation wizard, and an exceptional person. I first met him when giving a seminar at SMI which ended with a lively discussion in a restaurant late in the evening. We later met regularly during my visits to SMI as a member of the SMI Scientific Advisory Board. I was looking forward to his reports – there was always an element of surprise, a novel method, a new twist to an established technique, or an interesting result of his research.

Mein herzliches Beileid an die Familie, Freunde und Kollegen.

ever since I heard that you had left this world, I have been speechless. 

From the moment I came to you to ask you to be my mentor to the moment you congratulated me on my Master's degree, you were my great support and someone who pushed me to work hard.

Working with you, having coffee with you was a great honor!

Thank you very much Hannes. I will always remember you as a wonderful person and a great mentor.

My deepest condolences to your family.

It was deeply saddening learning that you had left us for good. Your smiling face and enthusiasm is well imprinted everywhere in SMI. You were always there ready to help everyone who asked for help and I certainly got to learn a lot from the few instances I worked with you. 

I hope every time you look at us from wherever you are, you keep smiling the way you always have.

Ich durfte Hannes vor über 20 Jahren kennenlernen, als wir die ersten Schritte für Experimente an einem Hochenergie-Speicherring für Antiprotonen an der GSI unternahmen ... übrigens bis heute nicht realisiert. Die Freundlichkeit und Herzlichkeit, mit der er Menschen begegnete, ist mir neben seiner wissenschaftlich-technischen Kompetenz in sehr guter Erinnerung. Man konnte in jeder Hinsicht auf ihn zählen. Er hinterlässt eine große Lücke. Herzliches Beileid.

Dear Hannes,

I still can't believe that your desk will remain empty.

I am so grateful for all your support in the last few years, not only when I did my master's with you, but also now in my PhD on a different project. You were always there for me, no matter if it was a physics discussion I needed or other advice. 

We still wanted to call you and tell you that the cooling system you designed only a few months ago is working. It hurts that it was just a little too late.

I very much enjoyed sharing an office with you in the last year. I will deeply miss your interpretation of Gianna Nannini and your "Ciao everybody!" every time you joined an online meeting. 

Your enthusiasm was so inspiring and I hope to carry at least a fraction of it with me.

My deepest condolences to your family.

Ich hatte das Glück und durfte 24 Jahre lang für den Vorgesetzten Dr. Zmeskal und mit dem Kollegen Hannes zusammenarbeiten. Er gab einem nie das Gefühl das er der großartige Physiker (der er war) ist und ich der kleine unerfahrene Techniker. Er war sich keinen Handgriff, keine Tätigkeit oder Weg zu schade. Oft brauchte Hannes nur vorarbeiten und machte die letzten Handgriffe direkt vor Ort beim Experiment. Er nahm sich jeden an, ob StudentIn, PraktikantIn oder unerfahrene Techniker. Unsere Gespräche gingen weit über das berufliche hinaus, er erkundigte sich immer über die Familie und ich nahm ihm das ehrliche Interesse wirklich ab. Wir haben nicht nur miteinander gearbeitet, sondern auch das eine oder andere Glas Wein im Inland und Ausland getrunken. Die Heurigenbesuche in Wien und Umgebung oder die Abende in den Cantina in Frascati bleiben immer in meiner Erinnerung.

Es gab nur wenig Menschen bis jetzt in meinem Leben wo mich die Nachricht über das Ableben so getroffen hat wie bei Hannes.

Er wird mir fehlen als Mensch, Kollege und Mentor.

Dearest Hannes,

The day after you left for good was the saddest day at SMI. Working in the lab, surrounded by your experiments was painful, even more as I was testing a cooling system you designed just a couple of months before.

These days I come to realize how privileged I was to know you and work with you over the past several years. You were truly one of a kind - an admirable character with tremendous knowledge in physics, treating everyone with the same kindness and respect, ready and able to help with just any experiment.

I am forever grateful for having worked closely with you at SMI and CERN, and for your invaluable involvement in the annihilation experiments at ASACUSA. I will miss you and your unfathomable lightness and enthusiasm in everything you did: from daily communication to genuine problem-solving, from supporting younger researchers to generously sharing your knowledge and expertise, from carrying out experiments to lifting the mood whenever you appeared with your child-like joie de vivre.

My deepest and most sincere condolences to your family.

The very sad news of Hannes having left us are devastating. I knew him since he was working at the Paul Scherrer Institut in Villigen (PSI/CH) on muon catalyzed fusion (a seminal 1993 article with other prominent colleagues can be found at https://doi.org/10.1007/BF01027965). Hannes made substantial contributions to experiments at various facilities such as J-PARC (Japan), CERN, PSI and recently at LNF-Frascati, where his competences in hardware will be badly missed. He was a versatile physicist, always ready to listen and help, with a positive attitude towards projects, even when they were outside his own fields of interest. SMI is loosing an irreplaceable collaborator and friend.  My deepest sympathies to his wife and his daughter!