Murchhana Roy

MRO292's picture
  • PhD Candidate
  • Graduate Research Assistant
  • Physics & Astronomy
CP 61 (Lab)
(859) 257-3942
Research Interests:
Research
I am a PhD candidate in the department of Physics and Astronomy at UKY having over 6 years of graduate research experience.
My dissertation experiment E12-06-121 : “A Path to Color Polarizabilities in the Neutron: A Precision Measurement of the Neutron g2 and d2 at High Q2 in Hall C” (https://hallcweb.jlab.org/wiki/index.php/A1nd2n) was succesfully completed in September 2020 in Jefferson Lab Hall C  at Newport News, VA.
The spin structure of the nucleons became a theoretical crisis after an experiment carried out by the European Muon Collaboration (EMC) in 1987. Contrary to the expectation that the quark spin constitutes 75% of the spin of the nucleon, the experiment revealed that they contributed a small fraction (~12%) of the total spin. This crisis has since resulted in multiple theoretical and experimental research endeavors to crack one of the unsolved problems of physics, popularly known as the “proton spin puzzle”. The current understanding of the nucleon spin is that the total spin is distributed among valence quarks, sea quarks, their orbital angular momenta, and gluons. My dissertation research aims to explore the neutron spin structure over a wide kinematic range with very high precision data.
Due to the non-perturbative nature of strong interactions, it is extremely difficult to make absolute predictions using the existing theory (Quantum Chromodynamics or QCD) on how the spin is decomposed in all the components. To experimentally investigate the nucleon spin structure, deep inelastic scattering (DIS) is used where the high-energy electrons are scattered inelastically from the nucleons by transferring a virtual photon with momentum Q. In DIS the electrons are scattered elastically from the quarks inside the nucleon by carrying a fraction x of the nucleon momentum and it provides a measurement of nucleon structure functions. Two structure functions g1 and g2 encode information on the momentum structure and spin structure of the nucleon respectively. This simple two-particle (electron-quark) scattering process is expected to break down at lower energies and momentum transfers because of the correlation of quarks and gluons. It is yet unknown at which point the correlation process starts. The third moment of the linear combination of g1 and g2 , denoted by d2 , is a clean probe to the quark-gluon correlation. The experiment aims to do a precision determination of g2 and d2 of neutrons which will give insight into the unanswered questions of physics i.e. quark spin contribution and the quark-gluon correlation. To minimize the uncertainty in the extraction of the g2 in the final results, the precision for the magnetic field direction measurement needed to be within ±0.1°. A novel air-floated compass was conceptualized and constructed at the University of Kentucky as the commercially available compasses cannot achieve the aforementioned level of precision. I am currently working on publishing the paper titled “Development and Construction of a Precision Compass” (M. Roy et al.) detailing the work performed for the magnetic field direction measurement.
 
Furthermore, I have made valuable contributions to a few other projects in my research group. One of the first projects I collaborated on at the University of Kentucky was an experiment to study the magnetically induced Faraday rotation by polarized helium-3 atoms, The team did a pioneering experiment by using helium-3 as a substitute for dark matter to probe limits on the possible magnetic moment of asymmetric dark matter. The study has resulted in a publication in Physical Review A (J. Abney et al., 2019), titled “Limits on magnetically induced Faraday rotation from polarized 3 He atoms”. As a part of this study, I developed a novel setup to reduce laser phase noise using an interferometer and an innovative feedback system that corrects the interferometer phase by eliminating phase drift with time and making it significantly more stable. I have also collaborated on an experiment that was part of the Spallation Neutron Source neutron electric dipole moment (nEDM@SNS) experiment. This experiment used the electro-optic Kerr effect to extract the strength of the net electric field to study the behavior of charge accumulation in a superfluid helium environment. This study has culminated into a paper titled “The Behavior of Charged Particles on Insulating Surfaces in Cryogenic Fluids within (Strong) Electric Fields” (M. Broering et al.) which is pending submission.

 

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