Prof. Asher Gotsman - Obituary

Asher was born in Krugersdorp, South Africa, on the 21st of October 1934. His start to life was not easy. He lost his father when he was only two years old. His mother decided to send him to Cheder in the hope that the Rabbis would be able to instil some discipline into her wild young son.

At the age of 12 the family moved to Randfontein and he attended Krugersdorp High School. He was known for his mischievous behavior as well as for being a great athlete. A major part of Asher's life in his youth, was his membership of the Habonim Jewish Youth Movement, where he spent many happy hours and made friends for life.

In 1952, at the age of 18, he came to Israel through the Movement to spend a year at \Mahon L'Madrichei Chutz LeAretz", the Institute for Youth Leaders from Abroad, which left a lasting impression on him. He spent time at Kibbutz Tzora and A kim, picking eggplants from morning till night and eating so many that for the rest of his life he could not eat an eggplant again. 

Asher discovered his two big passions while studying at the University of Witwatersrand, in Johannesburg, Education and the Field of Physics. He turned out to be an outstanding student, to the surprise of many of his friends from childhood, and earned an Honors Master's degree in Applied Maths and Physics.

In 1959 he was o ered a place at Imperial College London to do his Ph.D. in physics under the supervision of Abdus Salam, who later went on to win a Noble Prize in the eld.

In 1957 he married Lesley Targowsky and they had three children. Lesley sadly passed away in 2007. 

While studying in London, he became close friends with Yuval Ne'eman, who later on served as the Minister of Science in the Israeli Government. Yuval persuaded Asher that people with his knowledge, background and intelligence were desperately needed in the edgling State of Israel. After graduating in 1963 the young family made Aliya and moved to Rehovot, while Asher started his rst job, at the I.A.E.C in Nahal Soreq (Israel's Centre for Nuclear Research at the time), joining the group of young scientists and students whom Yuval gathered to form the nucleus of Theoretical High Energy Physics in Israel. 

The research activity of this group took place in the Soreq Research Facility in Yavne and at the Weizmann Institute in Rehovoth. Upon Yuval's establishment of the Physics Department at Tel Aviv University in 1967, Asher joined him there as one of the rst High Energy theorists. Asher became Vice-Chair of the Physics Department, assisting Yuval in handling the a airs of the department while Yuval became President of Tel Aviv University. In 1971 Asher was elected Chairman, and held this oce until 1976. He was reelected as Chair in 1978 and in 1992, after the Department had become the School of Physics and Astronomy. He was the Head of the School for a total of 11 years - an unmatched achievement until today. This feat resulted mainly from Asher's great character as a leader. He would always treat everyone as an equal never mind if they were the cleaner, secretary or a Noble Prize winner. Asher was also recognized as an extremely talented lecturer and researcher. During his distinguished career, spanning more than 60 years, he contributed in many ways to the State of Israel, which he rarely discussed.

In the early 1990's, after the fall of the Berlin Wall, Israel was ooded with a wave of extremely talented scientists. Asher, as Head of the Physics Department, went out of his way to nd jobs for as many of them as he could, even if it meant that they had to take positions that were below their capabilities, just to make sure that they could feed their families.

Even after his retirement, as Professor Emeritus, he never stopped doing research, going to his office at the University every day, well into his 80's. Two days before his passing he was noti ed that his last research paper had been approved for publication in one of the leading physics Journals.
In 2009, he started a new meaningful relationship with Margie Goss, where he gained the love and a ection of an additional family along with seven surrogate grandchildren. Margie and Asher lived happily together until he passed away.

As was said of him by a friend of over 70 years, \He was exacting in his expectations of himself and of others, with a passionate and generous side to his nature". He was an unbelievable father and grandfather to his six grandchildren and four great grandchildren who were immensely proud of him. He was humble, full of life's wisdom that he was always very happy to share, always happy to help others whenever he could and was always extremely hard working. As a friend of his from Habonim, aptly said, \Gotsie was a gentle giant, physically, mentally and emotionally".

In 1966, Yuval and Asher started a particle physics experimental group at Tel-Aviv University and Asher contributed afterwards to its development by being the active theoretical adviser. He was always ready to interact with the experimentalists and continued this activity till the end of his life. 

Asher started working in high energy physics in the days when 1 GeV was high energy and almost every experimental paper reported a discovery of new resonance. He belonged to the generation which transformed the growing experimental information and the general eld theory approach to the theory of strong interaction: quantum chromodynamics. The span of his research covered the range from \the one and two pion contributions to nuclear forces" in the new Tamm-Danco method (his PhD thesis from The Imperial College, 1963) to \High energy evolution for Gribovwanziger con nement: solution to the equation" (the last his paper in archive which appeared after his death).

As all physicists of his generation, Asher started working on S-matrix and Regge theory. Hadronic duality, which was the main subject of Asher's research at that time, was a realization of the S-matrix bootstrap idea relating hadron resonances (in the s-channel) with Regge pole trajectories (in t- and u- channels). It was the rst theoretical approach, which put the strong interaction on the solid theoretical basis, and led to modern string theory. Proceedings of the International Conference on Duality and Symmetry in Hadron Physics which was held at Tel Aviv University, April 5-7, 1971 and which had been edited by Asher were on the desk of all theoretical physicists in the 70's. 

The other facet of his activity in this, before QCD, time was the Regge approach with special attention to the interaction of photons. His paper (with N. H. Buttimore and E. Leader) on \ spin dependent phenomena induced by electromagnetic hadronic interference at high energy" (Phys. Rev. D 18 (1978), 694) opened a new way to measure the amplitudes of the strong interaction at high energies and it is still in use by the experts (the last reference to this paper is dated December 16, 2020). Asher and his collaborators (U. Maor, G. Alexander, M. Bander, A.Levy, P.D. Mannheim) investigated the contribution of Reggeons and the absorptive corrections to a number of di erent reactions. These papers were the signi cant contributions of the Tel Aviv theory group to the understanding of the high energy community of the general features of the Reggeon approach and its ability to describe the experimental data. 

It should be specially noted that the work of Asher and U. Maor on the extended vector dominance model which allowed the description of the photon- hadron and photon-photon interaction in the framework of the Regge approach. These papers were a harbinger of Asher's interest in deep inelastic scattering processes which became his main interest after QCD had been suggested.

After the advent of QCD, Asher (with A. Levy, D . Lissauer , U. Maor and S. Nussinov ) actively involved in understanding of the main properties of di erent hard processes, that are coming from the short distances, where the perturbative QCD can be applied. He (with A.Levy and U. Maor) undertook the rst attempt to separate two components of a photon: the hadronic one, which was treated in the extended vector dominance model , and the point -like one, which was estimated in perturbative QCD. This idea was the leading one in his further research.

By the time when HERA started to operate, the informal QCD theory group had been formed around him, which included E. Levin, U. Maor and students and post.-docs: E. Naftali, S. Bondarenko, K. Tuchin, M. Lublinsky, A. Prygarin, A. Kormilitzin and J. Miller. In addition to building the theoretical approach to the interaction at high energy and short distances (the Colour Glass Condensate (CGC) approach) this group worked in close cooperation with Israeli experimentalists at HERA, and developed its own angle at which it discussed the experimental data, looking for the saturation of the deep inelastic structure functions and searching for the new dimensional scale: saturation momentum, that arose from CGC. It became a respectable part of the CGC (low x) community, which twice came to Israel for its main conference: in 1999 at TAU, with Asher as the head of the organizing committee, and in 2013 (M. Lublinsky, BGU and A. Milov, WIS).

The trademark of TAU QCD group is its e ort to build a model, based on theoretical achievements, which is able to describe both long and short distances. In this model, on the same footing, is described the data on the total, elastic and di ractive cross sections, as well as inclusive production of the soft interactions at high energies. This is the only model on the market which is successful in describing the above-mentioned soft interaction data together with the deep inelastic scattering data, which occurs at short distances.

Over the past ve years Asher (with E. Levin) developed a new approach based on a robust relation between the principle features of high energy scattering and entanglement properties of the hadronic wave function and suggested a new mechanism of multiparticle production, which takes into account the interface between short and long distance physics. 

In his last papers Asher(with E. Levin) has found the generalization of the BFKL and BK evolution equations, which includes the Gribov-Zwanziger approach to the con nement of quarks and gluon, resolving the main theoretical diculty of the CGC approach: the power-like decrease of the scattering amplitude that results in the violation of the Froissart theorem. 

He will be remembered by his colleagues as a kind and knowledgeable physicist ready to advise and help others. Asher will be sadly missed by all who knew and loved him.

Family and Colleagues