Fermilab E-906/SeaQuest
Fermilab E-906/SeaQuest is a particle physics experiment which will use Drell–Yan process to measure the contributions of antiquarks to the structure of the proton or neutron and how this structure is modified when the proton or neutron is included within an atomic nucleus.
Overview
The Fermilab E-906/SeaQuest experiment is part of a series of fixed target Drell–Yan experiments designed to measure the quark and antiquark structure of the nucleon and the modifications to that structure. With these measurements, SeaQuest will also be able to quantify the energy loss of a colored parton travelling through cold, strongly-interacting matter.SeaQuest has been approved by Fermilab to extend previous down to up antiquark measurements to larger Bjorken x. It will use a 120 GeV proton beam extracted from the Fermilab Main Injector. The experiment will also examine the modifications to the antiquark structure of the proton from nuclear binding.
Physics motivations
/ asymmetry
Originally it was thought down and up antiquarks were produced in the nucleon sea with a ratio of 1. However, the result of deep inelastic scattering experiment by CERN-NMC showed that there are more 's than 's in the proton.The Gottfried sum evaluated by NMC from the data of deep inelastic muon scattering on a proton and a deuteron targets was 0.235±0.026 which is smaller than the expected value of 0.333. This means that - integrated over Bjorken x from 0 to 1.0
is 0.147±0.039, indicating a flavor asymmetry in the proton sea.
In the early 1990s, DYSSIS made a measurement of Drell–Yan process in the low Bjorken x region that tilted the ratio in favor of a higher number than. Experiments such as Fermilab E-866/NuSea yielded results in a range of low Bjorken x, which further showed an asymmetry in the antiquark production. SeaQuest will extend the measurements to higher Bjorken x, which will help resolve questions about the behavior of this ratio above.