Selected Physics Topics at the
Electron-Ion-Collider
Antje Bruell, JLab
ECT workshop, July 2008
• nuclear effects in deep inelastic scattering from fixed target
experiments
• prospects for EIC
• TMDs and GPDs at EIC
• Summary
x and A dependence of the EMC effect
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Q2 dependence of the EMC effect
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
NMC vs E665 nuclear data
NMC experimental set-up
cancellation of acceptance and luminosity
Gluon Saturation at EIC ?
Gluon distribution G(x,Q2)
– What can we measure at EIC ?
• Extract from scaling violation in F2: dF2/dlnQ2
• FL ~ as G(x,Q2)
– Other Methods:
• 2+1 jet rates (needs jet algorithm and modeling of hadronization
for inelastic hadron final states)
• inelastic vector meson production (e.g. J/)
• diffractive vector meson production - very sensitive to G(x,Q2)
d
dt
(γ*A  VA)  a S2 [G A ( x, Q 2 )]2
t 0
Gluon Saturation at EIC ?
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
Exclusive Processes: Collider Energies
Exclusive Processes: EIC Potential and
Simulations
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
5 GeV  50 GeV/c
(e  P)
 Q2=4 GeV2
 2= 0.2
 P’ tagging required
– Exclusivity
  Resolution
 () ≈ 0.3GeV2
without tagging
• Transverse
Imaging
Exclusive charged pion production
Assume: 100 days,
Luminosity=10E34
Missing mass reconstruction
10<Q2<15
15<Q2<20
35<Q2<40
0.01<x<0.02
Ee=5 GeV
Γ dσ/dt (ub/GeV2)
Γ dσ/dt (ub/GeV2)
Ep=50 GeV
Detect the neutron
0.02<x<0.05
10<Q2<15
15<Q2<20
35<Q2<40
0.05<x<0.1
0.05<x<0.1
-t (GeV2)
•
•
Neutron acceptance limits the t-coverage
The missing mass method gives full t-coverage for x<0.2
-t (GeV2)
Assume dp/p=1%
(pπ<5 GeV)
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TIFF (Uncompressed) decompressor
are needed to see this picture.
Transversity and friends
Unpol. DF
q(x)
Helicity
q(x)
Transversity
dq(x)
g1T
f1T
Sivers function
h1
Boer-Mulders function
h1L
EIC workshop, May 21th
h1T
R.Seidl: Transversity measurements at EIC
20
First successful attempt at a global analysis for the transverse SIDIS and the BELLE Collins data
 HERMES AUT p
data
 COMPASS AUT d
data
 Belle e+ e- Collins
data
 Kretzer FF
 First extraction
of transversity
(up to a sign)
Anselmino et al: hep-ex 0701006
R.Seidl: Transversity
measurements at EIC
21
EIC
workshop,
May 21th
What can be expected at EIC?
 Larger x range
measured b y existing
experiments
COMPASS ends at ~
0.01, go lower by almost
one order of magnitude,
but asymmetries become
small
 Have some overlap at
intermediate x to test
evolution of Collins
function and higher
twist but at higher Q2
EIC workshop, May 21th
R.Seidl: Transversity measurements at EIC
22
The Gluon Contribution to the
Nucleon Spin
Antje Bruell, Jlab
EIC meeting, MIT, April 7 2007
• Introduction
• G from scaling violations of g1(x,Q2)
• The Bjorken Sum Rule
• G from charm production
Sivers effect: Kaon electroproduction
EIC
CLAS12
• The low x of EIC makes it ideal place to study the Sivers asymmetry in Kaon
production (in particular K-).
• Combination with CLAS12 data will provide almost complete coverage in x
Correlation between Transverse Spin and
Momentum of Quarks in Unpolarized Target
All Projected Data
Perturbatively
Calculable at
Large pT
Vanish like
1/pT (Yuan)
ELIC
Summary
• eA data from fixed target experiments insufficient to constrain
nuclear gluon distribution
• large kinematic range of EIC will provide precision data on e.g. Q2
dependence of F2A/F2D and x dependence of FLA/FLD and will thus
allow to investigate the low x phyiscs of saturation in the nucleus
• high luminosity and large kinematic coverage will allow to do
gluon and quark “tomography” via exclusive processes
(measurement of fully differential cross sections for diffractive and
non-diffractive channels)
• single spin asymmetries will determine transverse spin effects and
get access to orbital momenta