Ashutosh V. Kotwal
Fritz London Distinguished Professor of Physics

Prof. Ashutosh Kotwal's research focuses on the physics of fundamental particles and forces at high energies. The discovery of the Higgs boson has answered the 50-year old puzzle of how fundamental particles acquire mass. However, the properties of the Higgs boson are not understood, and neither is the process by which the Higgs field condenses everywhere in space. Prof. Kotwal is pursuing these questions experimentally using two approaches - precision measurements of fundamental parameters, and direct searches for new particles and forces.

Prof. Kotwal leads the worldwide 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 properties of the Higgs boson. If the properties of the Higgs differ from the current Standard Model theory, the mass of the W boson will also differ from its predicted value. 

Over the last 27 years, Prof. Kotwal has published five world-leading measurements of the W boson 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, achieving a precision of 0.02% in 2012. This was the world's best measurement, and it predicted the mass of the Higgs boson before its discovery at the LHC.

In 2022 he published the W boson mass with an improved precision of 0.01%, which is more precise than all previous measurements combined. This measurement is significantly different from the theory. It is the most significant deviation ever observed from a fundamental prediction of the Standard Model. As such, it is our biggest clue yet that we do not completely understand the weak nuclear force or all the particles that experience
this force. This measurement points towards exciting new discoveries in particle physics for years to come.

The Standard Model is a set of equations, first developed in the 1960's and '70s, describing the basic building blocks and forces of nature. It has been one of the most successful theories in all of science. The deviation observed by Prof. Kotwal could indicate a new principle at work in nature. Some of the possibilities for extending the Standard Model are supersymmetry, substructure of the Higgs boson, additional Higgs-like particles and dark-sector particles. These could manifest as new particles and be discovered in running and future experiments.

The Standard Model is known to be incomplete because it does not explain the dark matter in the universe, nor the excess of matter over antimatter, nor the force of gravity. Prof. Kotwal's measurement is in direct contention with the Standard Model, which has been the most successful quantum theory of matter and forces to date. This could be the first step towards a more complete theory.

Prof. Kotwal's research on the ATLAS experiment at the LHC is also motivated by the possibility of Higgs and top quark compositeness. He has initiated a new idea to search for top quark constituents by looking for top-antitop resonances in events with four top quarks. In this project he has been joined by colleagues from Harvard and DESY, Germany. He is also pursuing the vector boson fusion process as a method to measure important Higgs properties and to detect resonances in the Higgs sector, both providing incisive tests of the Higgs theory. 

The second part of Prof. Kotwal's ATLAS research is motivated by Dark Matter, which was discovered on the galactic and cosmic scales via its gravitational interaction. If Dark Matter consists of particles, these may be produced from the decay of heavier, short-lived charged particles which in turn can be produced at the LHC. With his postdoc Kate Pachal and colleagues from Harvard and Genoa, Prof. Kotwal is designing an analysis to search 
for heavy short-lived charged particles using the silicon pixel detector. This work is closely aligned with Prof. Kotwal's expertise in particle tracking and efforts to improve tracking algorithms for ATLAS. His group is working to improve both the efficiency and speed of these algorithms so that such rare signatures can be recognized and separated at very high rates. This project is a key component of the LHC upgrades to collect vastly more data over the next two decades. 

Prof. Kotwal also works with his students, post-doc and collaborators on searches of rare, exotic signatures of new interactions. Searching for a fifth force on ATLAS, he wrote the first three ATLAS papers on searches for heavy force mediators decaying to leptons. On the CDF experiment 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 data on neutrino oscillations), in supersymmetric theories which impose a fermion-boson duality, and in grand unified theories. Also on CDF, Prof. Kotwal pursued improved techniques to search for the standard model Higgs boson, publishing three papers using advanced techniques. These techniques are now being used in the ATLAS experiment for the Higgs boson measurements in the vector boson fusion process. 

Also on CDF, Prof. Kotwal and collaborators have 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.

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 as the head of 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 has served as the Chair of Duke University's Information Technology Advisory Committee and as the Associate Chair of the Physics Department. He received the Dean's Leadership Award from Duke University and was elected Fellow of the Maharashtra Academy of Sciences, India.

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