Neutral Pion Double Helicity Asymmetry in Polarized Proton-Proton Collisions at [the square root of sigma]=200 GeV at STAR
Author(s)Leight, William (William Axel)
Longitudinal double-spin asymmetry for inclusive neutral pion production in polarized proton-proton collisions at **s=200 GeV
Massachusetts Institute of Technology. Dept. of Physics.
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One of the primary goals of the spin physics program at the STAR experiment is to constrain the polarized gluon distribution function, [delta]g(X,Q²), by measuring the double longitudinal spin asymmetry, ALL, of various final-state channels. Neutral pions provide a potentially powerful final state because they are copiously produced in p+p collisions and have few backgrounds. In 2009, STAR took 14 pb-¹ of integrated luminosity of 200 GeV p+p collisions, with average beam longitudinal polarization of 59%. Neutral pions produced in these collisions can be identified using STAR's large-acceptance electromagnetic calorimeter, with help from tracking from the STAR Time Projection Chamber. This work presents a measurement of the inclusive neutral pion ALL from this data, based on a new [pi]⁰ reconstruction algorithm. A comparison to theoretical predictions and other experimental results suggests that the current best-fit value of AG, the gluon contribution to the proton spin, is too small and that [delta]G is actually comparable in magnitude to the quark contribution to the proton spin [delta][sigma].
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis. In title on title page, "the square root of sigma" appears as the mathematical symbol.Includes bibliographical references (p. 109-112).
DepartmentMassachusetts Institute of Technology. Dept. of Physics.; Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology