Experimental Nuclear Physics

Research Interests

As a nuclear physicist, I am devoted to understanding how a subset of the most fundamental particles of our universe, quarks and gluons, interact to form the nucleons upon which our visible world is built. The study of strong interactions is complicated by the reality of color confinement, which prevents the observation of free quarks and gluons. Unlike partons, nucleons are readily accessible and therefore have served as surrogates for the ``partonic laboratory'' for nearly half a century. Consequently, the underlying mechanisms of Quantum Chromodynamics (QCD) are illuminated via investigations into how the nucleon mass, charge and spin manifest from the partonic degrees of freedom of the quarks and gluons from which they are built.

Within the broad framework of nuclear and particle physics, one of my primary research interests is the study of the parton helicity and transversity distributions inside the nucleon. The successes of the the deep inelastic scattering experiments of the last century informed us of the small total quark helicity contributions to the nucleon, and current experiments at the Relativistic Heavy Ion Collider (RHIC), European Organization for Nuclear Research (CERN) and the German Electron Synchrotron (DESY) are starting to shed light on what appears to be a small gluon helicity distribution (Δ G) in the proton. While these answers reflect great progress in the field, they only lead to more intriguing questions. Is the gluon helicity distribution in the nucleon truly small or, as in the unpolarized distribution, does it vary strongly with Bjorken x_g? How does partonic angular momentum contribute to the total nucleon spin and what is the best way to measure it? Is the helicity distribution of the sea flavor symmetric? What are the quark transversity distributions and how do the transverse momentum of the initial partonic distributions and final fragmentation functions correlate with the partonic spin? Our work in the STAR collaboration at RHIC is centered around investigations aimed at answering precisely these questions.

Education

• B.S. Physics, University of Virginia, 1995
• Ph.D. Nuclear Physics, University of Virginia, 2002
• Postdoctoral Associate, Indiana University Cyclotron Facility, 2002-2005
• Senior Postdoctoral Associate, Massachusetts Institute of Technology, 2005-2007

1. STAR Collaboration (B.I. Abelev et al), ``Longitudinal Double-spin Asymmetry and Cross-section for Inclusive Jet Production in Polarized Proton Collisions at √ s=200 GeV/c,'' Phys. Rev. Lett. 97, 252001 (2006).
2. CLAS Collaboration (A. Deur et al.), ``Experimental determination of the evolution of the Bjorken integral at low Q²,'' Phys. Rev. Lett. 93, 212001 (2004).
3. CLAS Collaboration (R. Fatemi et al.), ``Measurement of the Proton Spin Structure Function g₁(x,Q²) for Q² from 0.15 to 1.6 GeV² with CLAS,'' Phys. Rev. Lett. 91, 2220022 (2003).
4. C.D. Keith, M. Anghinolfi, M. Battaglieri, P. Bosted, Stephen Bueltmann, V.D. Burkert, S.A. Comer, D.G. Crabb, R. De Vita, G. Dodge, R. Fatemi, D. Kashy, S.E. Kuhn, Y. Prok, M. Ripani, M.L. Seely, M. Taiuti, S. Witherspoon, ``A Polarized Target for the CLAS Detector,'' Nucl. Instrum. Meth. A, 327 (2003).
5. SLAC E155 Collaboration (P.L. Anthony et al.), ``Precision Measurement of the Proton and Deuteron Spin Structure Functions g₂ and Asymmetries A₂,'' Phys. Lett. B553, 18 (2003).
6. Stephen L. Bueltmann, D.G. Crabb, D.B. Day, R.D. Fatemi, B. Gardner, C.M. Harris, J.R. Johnson, J.S. McCarthy, P.M. McKee, W. Meyer, S.I. Penttila, E.Ponikvar, A. Rijllart, O.A. Rondon, S. St.Lorant, W.A. Tobias, S. Trentalange, H. Zhu, B. Zihlmann, D. Zimmermann, ``A Study of Lithium Deuteride as a Material for a Polarized Target,'' Nucl. Instrum. Meth. A425, 23 (1999).
7. Complete list of Papers

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