future opportunities at an electron-ion collider oleg eyser brookhaven national laboratory
TRANSCRIPT
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Exploring the Glue that Binds Us All
Questions at the next QCD frontiero How are the sea quarks and gluons, and their spins,
distributed in space and momentum inside the nucleon?o Where does the saturation of gluon densities set in?o How does the nuclear environment affect the distribution of
quarks and gluons and their interactions in nuclei?
An Electron-Ion Collidero Electron beams for precision measurementso Polarized nucleon beamso Heavy ion beams of different specieso Kinematic reach into the gluon dominated regimeo Dedicated hermetic detector setup
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The Structure of the Nucleon
What is the dynamical origin of sea quarks and gluons inside the proton?
How does the proton spin originate at the microscopic level?
How is hadron structure influenced by chiral symmetry and its breaking?
How does confinement manifest itself in the structure of hadrons?
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Deep Inelastic Scattering
Lorentz invariants
π =(π+π )2=4 βπΈπ βπΈπ
π2=βπ2=β (πβπ β² )2
π₯π΅=π2
2βπ βπ
π¦=π βππ βπ
In the collider frame
πΈπβ² =πΈπ β (1β π¦ )+ π2
4 βπΈπ
π2=π₯ β π¦ βπ
Other variables
π 2=(π+π)2=π2 β (1β1 /π₯ ) π=π βππ
=π¦ βπ 2π
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Structure Functions
π2πππ₯ππ2=
4 ππΌ2
π₯π4 [(1β π¦+ π¦ 2
2 )πΉ2 (π₯ ,π2 )β π¦2
2πΉ πΏ (π₯ ,π2 )] π π=πΉ 2 (π₯ ,π2 )β π¦ 2
1+ (1β π¦ )2πΉ πΏ (π₯ ,π2 )
12 [ π2πβ
ππ₯ππ2βπ2πβ
ππ₯ππ2 ]β 4ππΌ2
π4 π¦ (2β π¦ )π1 (π₯ ,π2 )
πΉ 2 (π₯ ,π2 )=π₯βππ2 [π (π₯ ,π2 )+π (π₯ ,π2 ) ] π1 (π₯ ,π2 )=π₯βππ
2 [Ξπ (π₯ ,π2)+Ξπ (π₯ ,π2 ) ]
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Spatial Imaging of Nucleons
π β (π₯ ,ππ )= π (π₯ ,ππ2 )+
(ππ Γππ )π§
ππ
πππ2 π (π₯ ,ππ
2 )
πΈ (π₯ , π , π‘ )π» (π₯ ,π ,π‘ )
Fourier transform of at π=0π (π₯ ,ππ
2 )π (π₯ ,ππ
2 )
Exclusive processes
Resolution scale π2 ππ2 +π2
π
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The Nucleus: A Laboratory for QCD
What is the role of strong gluon fields, parton saturation effects, and collective gluon excitations in nuclei?
Can we experimentally find evidence of non-linear QCD dynamics in the high-energy scattering off nuclei?
What are the momentum/spatial distributions of gluons and sea quarks in nuclei?
Are there strong color fluctuations inside a large nucleus?
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Nuclear PDFs
π2πππ₯ππ2=
4 ππΌ2
π₯π4 [(1β π¦+ π¦ 2
2 )πΉ2 (π₯ ,π2 )β π¦2
2πΉ πΏ (π₯ ,π2 )]
Expect strong non-linear effects in FL from higher twist contributionsDipole model from Bartels et al.
π 2/πΏ (π₯ ,π2 )= πΉ 2/πΏπ΄ (π₯ ,π2 )
π΄ βπΉ 2 /πΏπ (π₯ ,π2 )
Quantify by
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Di-hadron Correlations
PRD 83, 1 5005 (2011)PRL 106, 022301 (2011)
Prediction in CGC framework Expected experimental significance
GeV
with EPS09 (nPDF shadowing)PYTHIA6 (partons, showers, fragmentation)DPMJet-III (nuclear geometry)
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Diffractive Scattering
Rapidity gap
|π‘|βπ2π2
Black disc limit Non-linear amplify in e+A
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ERL eRHIC
Electron beam energy 10 GeVProton beam energy 250 GeVIon beam energy 100 GeV/AElectron beam polarization 80%Proton beam polarization 70%
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MEIC
Electron beam energy 5 GeVProton beam energy 60 GeVIon beam energy 40 GeV/AElectron beam polarization 80%Proton beam polarization 70%
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Detector Layout
SolenoidEM-CalorimeterDual Rad. RICHAero RICH/DIRC/HR-ToFTrackingMicro-Vertex Tracking
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Saturation Scale QS
The ultra-relativistic boost amplifies the gluon densities in a nucleus
ππ 2 (π₯ ) ( π΄π₯ )
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π π΄13