Department of Physics

nuclear physics (experimental)

Senior Research Scientist William W. Jacobs investigates the QCD
 spin-flavor structure of the proton at STAR, parton fragmentation
 functions at Belle, and dark matter and rare Tau lepton decays at
  Belle II.

   * The STAR experiment at RHIC, Brookhaven National Laboratory.
     My focus is on investigations to understand the QCD spin-flavor
     structure of the proton as it arises from constituent quarks and
     gluons. Single and double spin measurements use colliding beams
     of both longitudinally and transversely polarized protons in
     RHIC, the world's only high energy polarized beam collider. A large
     "Endcap" Electromagnetic Calorimeter, built primarily at IU has
     aided such studies locally, an effort now spanning ~ 20 years.
     An accumulation of novel RHIC spin results, with more expected via
     a near term forward detector upgrade, help point the way to a
     future EIC (Electron-Ion Collider).

   * The Belle experiment at KEKB; the Belle II experiment at super KEKB,
     both at the KEK Laboratory, Japan (https://belle.kek.jp/ and
     https://www.belle2.org/).
     At the B-factory Belle, my interest is in precise determination of
     spin-dependent correlations and cross sections measured via clean
     electron-positron annihilation collisions. These are used to
     characterize the transition of asymptotically free partons into
     hadrons, as described by (FF) fragmentation functions. FF provide
     important information on open questions in nuclear physics,
     but also have crucial use in e.g., proton-proton collision analyses
     (STAR) to extract observables of physics interest.

     The upgraded Belle II experiment recorded its first collisions from
     SuperKEKB in April, 2018, ushering in a new era of precision for
     measurements at the intensity frontier. At IU, besides continued FF
     studies, understanding the particle nature and other interactions of
     dark matter is of particular interest. Belle II is well suited for
     such searches involving candidate or mediator particles in the
     vector, Higgs and axion portals.

     Because the high Belle II luminosities will produce a copious number of
     tau leptons, tau-decay physics will push new limits. Use of correlated
     production analysis techniques, along with minimal collision
     background conditions, will allow sensitive new tests of Lepton
     Flavor Violation and other rare processes of fundamental interest.

Learn more about Belle