# SA-CERN – Theory

Theoretical physics is the attempt to qualitatively or quantitatively understand through mathematics and deductive reasoning observations of the natural world and is a critical component of any physics venture.

High energy nuclear and particle physics is the investigation of phenomena at energy scales relevant for nuclei and above, at keV and higher.

South Africa has a long and storied history of involvement in theoretical high energy nuclear and particle physics, beginning with the arrival of R. W. James through Jack de Wetâ€™s input to the Spin-Statistics Theorem and Stanley Mandelstamâ€™s significant generation of new knowledge to the contributors to nuclear, heavy ion, and particle theory today.

The activities of the SA-CERN/Theory group fall directly into this proud tradition of theoretical high energy nuclear and particle physics in South Africa and are 1) the theoretical understanding of the high energy nuclear and particle physics investigated by the experimental groups at CERN and 2) the capacity building necessary for supporting such theoretical understanding.

**The principal investigators are**

Em/Prof. Jean Cleymans (UCT)

Prof. Alan Cornell (UJ)

A/Prof. W. A. Horowitz (UCT)

Prof. Steven Karataglidis (UJ)

Prof. Azwinndini Muronga (NMU)

Prof. Andre Peshier (UCT)

A/Prof. Heribert Weigert (UCT)

Dr. Dawit Worku (CPUT)

## Alan Cornell

Prof. Cornell has been involved with developing a gauge-Higgs unification model in extra-dimensions, which he has been studying at one-loop level. SU(N) and SO(N) models in an S1/Z2 extra-dimensional space are being considered, to develop the tools to calculate the Higgs mass and to study its couplings. This has led to the development of a new regularisation technique. Furthermore, this inspired our recent work on using the geometry of hyperbolic extra-dimensions to generate from a purely Yang-Mills theory new effective scalar sectors without the need to radiatively generate scalar potentials.

Studies of proposed extensions to the scalar sector of the SM are being studied, these now include composite Higgs models, where packages are being developed for their future phenomenological study. Amongst the possible non-minimal composite models (SU(6)/Sp(6) for example) are some with similar phenomenology to my explorations of the parameter spaces of 2HDM+S models, where S would be a complex scalar field. Note that additional features in such composite models are also of interest to phenomenology, such as dark matter candidates, lepto-quarks, and the ubiquitous pseudo-scalar present in such models.

Machine learning tools are also under development for deployment in generating exclusion plots for classes of beyond the Standard Model theories, where at the moment issues of utilising appropriate layer depth etc. are being investigated to accurately reflect the symmetries required in such theories. Such tools may also be of use in extra-dimensional models of gravity, where we are also investigating how this can possibly be used to study black-hole quasinormal modes, especially in their asymptotic limits.

UJ URL: https://www.uj.ac.za/contact/Pages/Prof-Alan-Cornell.aspx

Publications: https://inspirehep.net/literature?sort=mostrecent&size=25&page=1&q=exactauthor%3AA.S.Cornell.1

## W. A. Horowitz

A microsecond after the Big Bang, all of space existed at a trillion degrees, one hundred thousand times hotter than the centre of the sun. 13.8 billion years later, massive collaborations of thousands of scientists recreate these conditions of the early universe thousands of times a second in one of the most expensive and complicated science experiments ever attempted. My research focuses on the physics explored in these Little Bangs, ephemeral fireballs that–during their lifetimes of less than a billionth of a trillionth of a second–are droplets of the hottest, most perfect fluid in the universe.

UCT website: http://www.phy.uct.ac.za/phy/people/academic/horowitz

Personal website: https://webapp-phy.uct.ac.za/personal/horowitz/index.php

Publications: https://inspirehep.net/literature?sort=mostrecent&size=25&page=1&q=exactauthor%3AW.A.Horowitz.1

## Azwinndini Muronga

My research interests lie at the intersection of particle physics, nuclear physics, and astrophysics – studying the nature and properties of matter under extreme conditions such as those in high-energy heavy-ion collisions and in high-density compact astrophysical objects. My focus is on the understanding of the equation of state and transport properties of matter produced in heavy-ion collisions and in astrophysical compact objects (including during their collisions or explosions). The study is conducted using Â theoretical, mathematical, and computational methods in (1) Relativistic Fluid Dynamics, (2) Kinetic Theory, and (3) Thermodynamics and Statistical Models.

Call for MSc and PhD Students: https://sa-cern.tlabs.ac.za/wp-content/uploads/sites/15/2020/05/Mandela_Uni_Postdoctoral_Postitions_2020_Poster-v2.pdf

NMU website: https://science.mandela.ac.za/Azwinndini-Muronga

Publications:Â https://inspirehep.net/literature?sort=mostrecent&size=25&page=1&q=a%20A.Muronga.1

## Heribert Weigert

Modern collider experiments open one of the most fascinating windows into the extremes of our universe. We can probe into the properties and interactions of the smallest constituents of matter and recreate conditions our universe as a whole went through only a few microseconds after the big bang, all within the same facilities.

I am interested in QCD at high energies and densities as encountered in virtually all modern collider experiments, be it in the exploration of the standard model and physics beyond, or the Quark Gluon Plasma. My own research has centered on the Color Glass Condensate (CGC), a highly correlated state of predominantly gluons. Here I am one of the authors of the JIMWLK equation, the main tool to describe the energy dependence of the CGC dominated contributions to experiments as conducted at BNL and CERN.

The theoretical work to understand and correctly predict Â features of QCD in such extreme conditions is both challenging and satisfying.Â I invite students with a strong Â theoretical physics interest and a solid mathematical background to join my group in this intellectual adventure.

UCT website: http://www.phy.uct.ac.za/phy/people/academic/weigert

Centre for Theoretical and Mathematical Physics: http://www.phy.uct.ac.za/ctmp

Publications: https://inspirehep.net/literature?sort=mostrecent&size=25&page=1&q=f%20a%20weigert%2C%20h