Scholars@Duke

Prof. Ashutosh Kotwal's research focuses on the physics of fundamental particles and forces at high energies. One of the outstanding mysteries is the mechanism by which particles acquire mass. The theory of gauge symmetry has been very successful in describing the known fundamental forces; however this theory is obviously incomplete because it requires all particles to be massless. Clearly we are missing a big piece of the puzzle. Prof. Kotwal is pursuing this question experimentally using two approaches - precision measurements of fundamental parameters, and direct searches for new particles and forces.

Prof. Kotwal leads the effort to measure very precisely the mass of the W boson, which is sensitive to the quantum mechanical effects of new particles or forces. In particular it is directly connected to the mass of the Higgs boson, which is the quantum mechanical excitation of the Higgs field which imparts all fundamental particles their mass.

Using the data from the CDF and D0 experiments, he has developed new experimental techniques for performing precise calibrations. He has published numerous measurements of the W boson mass with increasing precision, most recently achieving a precision of 0.02%. This is the world's best measurement, and it predicted the mass of the Higgs boson which is compatible with the measurement of the Higgs-like boson discovered at the LHC. Within the current precision, Prof. Kotwal's measurement provides a spectacular confirmation of the Higgs theory.

His previous publications describe how he has progressively improved the experimental techniques for the W boson mass measurement. He now leads the effort to further improve on this precision by a factor of two, which can prove if new particles other than the Higgs boson also exist.

Prof. Kotwal and his post-doc Bodhitha Jayatilaka and collaborators have also published the most precise measurements of the top quark mass in the dilepton channel. His latest measurement used, for the first time in particle physics, neural network algorithms based on biological evolution. This method showed how to solve certain optimization problems based on ensemble properties.

Prof. Kotwal is pursuing improved techniques to search for the standard model Higgs boson. On the CDF experiment at Fermilab, he has published three papers describing the search for the Higgs boson, each time using more advanced techniques. He is now using one of these techniques for the first time in the ATLAS experiment at the LHC to search for the Higgs boson in a mode not yet observed.

Prof. Kotwal also works with his students, post-doc and collaborators on searches of rare, exotic signatures of new interactions. He has published searches for charged and neutral gauge bosons mediating new weak forces, the Higgs boson in theories that extend the standard model, and excited states of standard model fermions. These particles are predicted in theories where the weak interaction has both left-handed and right-handed couplings (as is indicated by recent data on neutrino oscillations), in supersymmetric theories which impose a fermion-boson duality, and in grand unified theories.

Prof. Kotwal's research program spans both the CDF experiment at Fermilab and the ATLAS experiment at the LHC. Prof. Kotwal is performing detailed studies of the silicon and transition radiation trackers of the ATLAS detector. His students on ATLAS are working on searches for new particles decaying to top quarks as well as Higgs boson measurements. He wrote the first three ATLAS papers on searches for heavy resonances decaying to leptons.

In addition to his experimental research, Prof. Kotwal has done theoretical work in the phenomenology of black holes in extra spatial dimensions. Extra spatial dimensions have been motivated by string theory and to explain why the gravitational force is so much weaker than the electromagnetic force at large distances. In this scenario it is possible for the gravitational force to be strong in the high energy regime of particle colliders, leading to the production of black holes. Prof. Kotwal has published a theoretical analysis of the production and decay of rotating black holes and their experimental signatures. Prof. Kotwal has also co-authored a paper on black hole relics.

Prof. Kotwal is the recipient of the Outstanding Junior Investigator Award and the Alfred P. Sloan Foundation Fellowship. He is a Fellow of the American Physical Society and a Fellow of the American Association for the Advancement of Science. He has served as project leader for analysis, software and computing on the CDF experiment, and now heads the experimental particle physics research group at Duke. He served as the Chair of the Fermilab Users Executive Committee and the DPF Nominating Committee. He is currently the Chair of Duke University's Information Technology Advisory Committee and the Associate Chair of the Physics Department.