[Jlab-seminars] Today's Physics Seminar: Markus Diefenthaler; “The SeaQuest Experiment at Fermilab”

[Stephanie Tysor]

*Physics Seminar*

*Markus Diefenthaler*

*University of Illinois*

**

/“/The SeaQuest Experiment at Fermilab”

Abstract//


The nucleon is one the the fundamental building blocks of the visible 
universe. But many of its properties and how those properties can be 
deduced from its inner structure are not well understood. Deep-inelastic 
scattering (DIS) experiments have revealed that the inner structure of 
the nucleon consists of relativistic quarks that exchange gluons, and 
have established quantum chromodynanics (QCD) as the theory of the 
strong interaction between quarks and gluons. Due to the confinement 
feature of the strong interaction and the relativistic nature of the 
system, we cannot yet explain many properties of the nucleon from first 
principles. Our knowledge of the inner structure of the nucleon is to a 
large extent based on the measurement of electroweak processes such as 
DIS or the Drell-Yan process, which can be interpreted within QCD. The 
SeaQuest experiment at Fermilab continues a series of Drell-Yan 
measurements to explore the antiquark content of the nucleon and to 
study the modifications to nucleon structure when the nucleon is 
embedded into a nuclei. To extend existing measurements to larger values 
of Bjorken-x - the momentum fraction of a quark within a fast moving 
nucleon - a 120 GeV proton beam extracted from Fermilab’s main injector 
is used, resulting in 50 times more luminosity than previous experiments 
and enabling access to values of x up to 0.9. An overview will be 
presented of the key physics goals of the SeaQuest collaboration: These 
include investigation of the dramatic dbar(x)/ubar(x) flavor asymmetry 
in the nucleon sea and its behavior at high x; study of the EMC effect 
in Drell-Yan scattering and the unexpected absence of any antiquark 
excess in existing data; and measurements of the angular dependence of 
the Drell-Yan process, sensitive to spin-orbit correlations within the 
nucleon. Updates to the SeaQuest experiment with polarized beam (E-1027) 
and target (E-1039) will allow us to study the quarks' spin-orbit 
correlations within the nucleon and to provide complementary information 
to existing data from DIS. The talk will conclude with a status report 
on the ongoing data taking and analysis of this new experiment.

*Thursday, January 22, 2015*

*CEBAF F113 @ 11:00 am*

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