Probir Roy (born 4 October 1942) is an Indian particle physicist and a former professor at Tata Institute of Fundamental Research. He is also a senior scientist of the Indian National Science Academy at Bose Institute and a former Raja Ramanna fellow of Department of Atomic Energy at Saha Institute of Nuclear Physics.
Known for the development of a sum rule on two-photon processes, Roy is an elected fellow of all the three major Indian science academies – Indian Academy of Sciences, Indian National Science Academy and National Academy of Sciences, India – as well as of the American Physical Society. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, for his contributions to physical sciences in 1987.[note 1]
Born on 4 October 1942 at Calcutta in the Bengal state of British India to Kiran Lal Roy-Sujata Sikdar couple, Probir Roy graduated in physics with honours from Presidency College, Calcutta (present-day Presidency University) in 1962 before moving to Cambridge University to obtain an MA (cantab) from Kings College, Cambridge in 1965. Subsequently, he joined Stanford University for his doctoral studies and secured a PhD, mentored by S. M. Berman, for his thesis in Kaon physics, in 1968. During this period, he worked at Stanford Linear Accelerator Center as a research assistant (1966–68) and as a temporary research associate (1968). He remained in the US for three more years for his post-doctoral work at Cornell University where he worked at the laboratories of Kenneth G. Wilson, who would go on to receive the Nobel Prize for physics in 1982, and Toichiro Kinoshita, an APS fellow, simultaneously serving the University as an instructor. Before returning to India in 1972, he had a one-year spell at CERN during 1971–72 as a visiting scientist.
Roy's career at Tata Institute of Fundamental Research started in 1972 as a visiting fellow and he became a regular research fellow a year later. He served the institution for three decades and half and before his superannuation from TIFR service as a senior professor in 2017, he held various positions as reader (1976–83), associate professor (1983–90) and professor (1990–93). After retiring from regular service, he continued his research at Saha Institute of Nuclear Physics as a DAE Raja Ramanna fellow of the Board of Research in Nuclear Sciences (BRNS) until 2012 and carries on his research at the Center for Astroparticle Physics and Space Science (CAPSS) of Bose Institute as a senor scientist of the Indian National Science Academy ever since. In between, he had several spells abroad as a visiting faculty and the institutions he has served include Oxford University, University of Texas at Austin, University of California, Riverside, University of Hawaii at Manoa, University of Helsinki and Kavli Institute for Theoretical Physics.
Roy's work in Kaon physics during his doctoral studies at Stanford University was based on the applications of algebra in the discipline and his thesis was subsequently published by the university under the title, Current-algebra Applications in Kaon Physics. Later, he worked on scale invariance and deep inelastic scattering while at CERN, Geneva and his research thereafter has covered several aspects of high energy physics. He has developed a new sum rule in two-photon processes which is related to the collision of two real polarised photons and the equation is now known as Roy's Sum Rule. Further, he proposed a solution for U(n)-symmetric Thirring model which has been detailed in two of his articles[note 2] published in 1975. Later, shifting his focus to supersymmetry and supergravity, he suggested new τ -number violating signals for R-parity breaking and estimated an upper bound on the gaugino-gravitino mass ratio. Deep inelastic lepton-hadron-photon processes with regard to their phenomenological aspects have been another area of his studies. He has also done extensive studies on neutrinos and Higgs mesons which covered the detection of heavy neutrinos, ultralight neutrinos in super-symmetry, oscillations and flavours, and his studies on neutrino detection helped India-based Neutrino Observatory in blueprinting the proposed detector at the observatory.
Roy's studies have been documented by way of a number of articles[note 3] and the online article repository of the Indian Academy of Sciences has listed 106 of them. Besides, he has published four more books other than his PhD thesis viz. Theory of Lepton-Hadron Processes at High Energies: Partons, Scale Invariance and Light-Cone Physics, Supersymmetry and Supergravity Nonperturbative QCD Phenomenology of the standard model and beyond, and Theory and Phenomenology of Sparticles: An Account of Four-Dimensional N=1 Supersymmetry in High Energy Physics. He has also contributed chapters to books published by others and has mentored doctoral and post-doctoral scholars. The lecture series or invited talks delivered by him included Linear collider signals of anomaly-mediated supersymmetry breaking, at the physics working group meeting of American Linear Collider Physics in 2004, The wonderful world of neutrinos at S.N. Bose National Centre for Basic Sciences in 2004, Measuring the deviation from maximal mixing of atomospheric neutrinos at INO, at PANIC 05 in Santa Fe, New Mexico, Event-shape of dileptons plus missing energy at a linear collider as a SUSY/ADD discriminant at Indian Institute of Science in 2006, Symmetries of nonhierarchical neutrinos from high to low scales at IWTHEP-2007, and Dark Energy of the Universe at Indian Institute of Science Education and Research, Pune in 2015.
Roy is one among the Indian participants in the Oxford-India Network in Theoretical Physical Sciences, an initiative promoted by the John Fell Fund. He was a member of the research committee of the Council of Scientific and Industrial Research during 1991–94. He served as the chairman of the Physics Graduate School from 1992 to 1997 and the Department of Theoretical Physics from 1997 to 2002, both based at Tata Institute of Fundamental Research. He sat in the governing council of S.N. Bose National Centre for Basic Sciences from 1997 to 2002 and in the editorial boards of Indian Journal of Pure and Applied Physics, Pramana and Indian Journal of Physics during various terms. He also served as the vice-president of the Indian Physical Society in 1996 and presided the society in 2002.
During his college days at King's College, Cambridge, Roy received three honours from the institution; Powel Prize for the best student in natural sciences (1964), senior scholarship (1964) and honorary scholarship (1965). The Council of Scientific and Industrial Research awarded him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards in 1987. The Indian Academy of Sciences elected him as a fellow in 1989 and he became a fellow of the Indian National Science Academy in 1992. Two years later, INSA selected him for the exchange fellowship between the academy of the Royal Society and the American Physical Society elected him as a fellow in 1995. He delivered the Meghnad Saha award oration of the Indian Association for the Cultivation of Science in 1997 and received the elected fellowship of the National Academy of Sciences, India in 2001.