A measurement of the x dependent sea flavor asymmetry at Seaquest
SeaQuest is a fixed target forward spectrometer experiment located at Fermilab which uses a 120 GeV proton beam on liquid hydrogen, liquid deuterium, and several solid targets. The flagship measurement of this experiment is to use the Drell-Yan process to improve the accuracy of the antiquark PDFs in the parton momentum fraction x range 0.1 to 0.58. By measuring the cross section ratio of proton-deutrium(x)/proton-proton(x) one can derive an estimate of the proton sea flavor asymmetry, dbar/ubar, as a function of x. This measurement is of interest to many theoreticians who have proposed several different classes of models in order to simulate the inner workings of the proton, a good test of these models is how well they predict the sea flavor asymmetry. A measurement from a previous experiment, E866, measured dbar/ubar at x above 0.3. The models proposed so far do not predict dbar < ubar at any x, so the accuracy of the E866 experiment in this region is of great interest. An analysis of some but not all of the data collected by SeaQuest is presented in this paper. It contains a measurement of the cross section ratio of proton-deuterium(x)/proton-proton(x), the application of several corrections and uncertainties to this measurement, and the derivation of dbar/ubar(x) from this measurement. Major corrections and uncertainties are the rate dependence correction and the target contamination correction. Particular care is paid to how to correctly merge the results from multiple data sets and optimizing the accuracy of estimating the value of parton momentum fraction x from measured quantities. The most notable feature of these results is that dbar/ubar is not less than one at any value of x, and is above one by several sigma where E866 measured dbar/ubar below one.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign