The Electron Ion Collider: A Next QCD Frontier · 2019. 9. 30. · The White Paper as of today: 146...
Transcript of The Electron Ion Collider: A Next QCD Frontier · 2019. 9. 30. · The White Paper as of today: 146...
The Electron Ion Collider: A Next QCD Frontier Understanding the glue that binds us all Physics Opportunities @ An Electron Ion Collider Bloomington Indiana August 20, 2012 A. Deshpande, Z.-E. Meziani, J. Qiu for the EIC WP Writing Group
Monday, August 20, 12 The EIC White Paper 2
• A brief background on the White Paper (WP)
• An overview of the current WP draft
• The executive summary (ES) and its time lines: Tribble-II subcommittee deliberations (Sept. 7)
• WP and its time lines: Broader NP community’s townhall meetings at the DNP’12 and Tribble-II final report (December’12)
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Dear Zein-Eddine, It is important in preparing for the next Nuclear Physics Long Range Plan to produce a community-wide science White Paper for a non-site-specific EIC by the end of calendar year 2011. This schedule would give us time to get further community and funding agency input, and to iterate to a final version by Fall of 2012, when Town Meetings for the next LRP might start.
I am writing to see if you would be willing to serve with Abhay Deshpande and Jianwei Qiu as overall editors and overseers of the White Paper. I lay out the organization of the Steering Committee you would lead below. The committee membership has been endorsed by Tom Ludlam, Bob McKeown and Hugh Montgomery, and at this point all the individuals listed below have agreed to serve.
I think the “Yellow Book” that will soon result from the Fall 2010 INT program should serve as a resource for the White Paper, but it will be far too long and detailed for a non-expert audience. I think the White Paper should be no more than ~100 pages, and should be aimed at non-experts, including our potential “champions” within DOE (e.g., Tim Hallman) and the rest of the Nuclear Physics community that will be asked to endorse this vision. It should start with an ~5-page Introduction – basically the “elevator speech” we have discussed, slightly amplified – laying out the goals, importance and uniqueness of the facility, and answering the basic questions raised about EIC at the last LRP meeting in Galveston in 2007, all in clear, concise, compelling, jargon-free language. The Introduction should also indicate the features of the science goals that could be accomplished with a first-stage machine and detectors, and should include a few of the most compelling “money plots” envisioned. I expect writing of the Introduction would fall mostly to the three overall editors in the organization outlined below.
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There should then be ~10-page sections on specific science areas, laying out and fleshing out “golden experiment matrices” with simulated money plots. It is very important that these sections build on the excellent progress made at the INT workshop in selecting golden experiments to emphasize – the White Paper should not try to present all science that would be done at an EIC, but should concentrate on the measurement program that most compellingly illustrates the intellectual goals and performance requirements of the facility. These sections should get across the fundamental goals of the research and enough technical discussion to convince a reader of the basic feasibility and interpretability of the results, but should otherwise be relatively light on technical experimental and theoretical detail. There should be a section of ~10-15 pages on basic machine parameters, design options, technical challenges and ongoing R&D, which covers both design approaches (again without gory technical detail). A similar section of ~10 pages on detector design features and challenges would round out the document as I see it. I don’t think this White Paper needs to get into cost estimates, although we will clearly need that as well by the time of the LRP. We have tried to assemble a Steering Committee comprising experimentalist/theorist pairs, broadly representative of the interested institutions (and not too heavily BNL- and JLab-laden), aligned with an envisioned breakdown of the science and technical sections, as follows: Overall editors: A. Deshpande (Stony Brook), J. Qiu (BNL) and Z.-E. Meziani (Temple U.) Gluon saturation in e+A: T. Ullrich (BNL) and Y. Kovchegov (Ohio State U.) Nucleon spin structure (mostly inclusive e+N): E. Sichtermann (LBNL) and W. Vogelsang (Tubingen) GPD’s and exclusive reactions: F. Sabatie (Saclay) and M. Diehl (DESY) TMD’s, hadronization and SIDIS: H. Gao (Duke) and F. Yuan (LBNL) Electroweak physics: K. Kumar (U. Mass.) and M. Ramsey-Musolf (Wisconsin) Accelerator designs and challenges: T. Roser (BNL) and A. Hutton (JLab) Detector design and challenges: E. Aschenauer (BNL) and T. Horn (CUA) Senior advisors: R. Holt (ANL) and A. Mueller (Columbia)
If you are willing to serve as one of the overall editors, please let me know soon, and then get in touch with Abhay and Jianwei to discuss how to launch the efforts. I am hoping that considerable progress can be made on the White Paper over the coming summer.
Cheers, and thanks for a reasonably prompt response, Steve
Monday, August 20, 12 The EIC White Paper 4
Final committee: Overall editors:
A. Deshpande (Stony Brook), J. Qiu (BNL) and Z.-E. Meziani (Temple U.) Gluon saturation in e+A:
T. Ullrich (BNL) and Y. Kovchegov (Ohio State U.) Parton propagation and energy loss in nuclei: (added)
W. Brooks (UTF, Santa Maria) & J. Qiu (BNL) Nucleon spin structure (mostly inclusive e+N):
E. Sichtermann (LBNL) and W. Vogelsang (Tübingen) GPD’s and exclusive reactions:
F. Sabatiė (Saclay) and M. Diehl (DESY) TMD’s, hadronization and SIDIS:
H. Gao (Duke) and F. Yuan (LBNL) Electroweak physics:
K. Kumar (U. Mass.) and M. Ramsey-Musolf (Wisconsin) Accelerator designs and challenges:
T. Roser (BNL) and A. Hutton (JLab) Detector design and challenges:
E. Aschenauer (BNL) and T. Horn (CUA) Senior advisors:
R. Holt (ANL) and A. Mueller (Columbia)
Monday, August 20, 12 The EIC White Paper 5
The White Paper as of today: 146 pages • Executive Summary (ES) à 12 pages to Tribble-II • Spin and 3D structure of the nucleon:
• Introduction (9 pages) • Longitudinal Spin: (11 pages) • Confined Motion of Partons in Nucleons (TMDs) (9 pages) • Generalized Parton Distributions (14 pages)
• The Nucleus: A QCD Laboratory • Introduction (5 pages) • Physics of extreme gluon density (23 pages) • Quarks and gluons in nuclei (8 pages) • Connections to A-A, p-A and Cosmic Rays (11 pages)
• Opportunities at the extreme luminosity (6 pages) • Accelerator design (12 pages) • Detector design (12 pages) • Acknowledgment (1 page à will certainly grow….) • References (9 pages)
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Comment on EIC WP Draft 146 page EIC White Paper (draft) Too long: not appropriate for Tribble-II deliberations. Submit the 12 Page Executive Summary to Tribble-II. The WP was and is intended for the broader NP community for the Long Range Planning discussions, and town-hall meetings.
Long Range Plan (When?) Town meetings being organized in DNP’12 (October 2012)
Need to open the EIC White Paper for Comments from BNL & Jlab User communities: More on this later.
Aim to prepare an almost final draft of the White Paper by October Town hall meetings, and submit the final White Paper to NSAC (and its subcommittees in November after input/comment from the DNP)
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LETS FOCUS ON THE EXECUTIVE SUMMARY: We would appreciate comments from the POETIC participants!
Monday, August 20, 12 The EIC White Paper 8
Feedback needed: Executive Summary • Written for a non-expert nuclear (+1 CM) physicists • Emphasis on complete but concise • August 28 submission aimed at Tribble-II 1st meeting: Sept. 7 • Currently, 12 pages: approximately correct length • The rest of the WP DRAFT will serve as a back-up document Feedback needed by August 24th: • What is absolutely needed to strengthen the case? • Are there statements made that are detrimental to the case? • Relative emphases amongst different components correct? • Any mistakes in the physics? (in the process of simplification) • Is there anything crucial that is missing? • Are there better figures? Could one improve cartoons?
• Only YES does not help: suggest/contribute alternatives!
Monday, August 20, 12 The EIC White Paper 9
(Adapted from Steve V.’s recent discussion on RHIC WP)
Method to convey your comments on the Executive Summary (by August 24): Please Email: Subject: “Comments on EIC Executive Summary” • Abhay Deshpande ([email protected]) • Zein-Eddine Meziani ([email protected]) • Jianwei Qiu ([email protected])
We will convey the comments to the entire WP writing group.
Monday, August 20, 12 The EIC White Paper 10
Monday, August 20, 12 The EIC White Paper 11
Contents
1 Exploring the Glue that Binds Us All – The Executive Summary 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Science Highlights of the Electron Ion Collider . . . . . . . . . . . . . . . . 3
1.2.1 Nucleon Spin and its 3D Structure and Tomography . . . . . . . . . 31.2.2 The Nucleus, a Laboratory for QCD . . . . . . . . . . . . . . . . . . 61.2.3 Physics Possibilities at the Intensity Frontier . . . . . . . . . . . . . 10
1.3 The Electron Ion Collider and its Realization . . . . . . . . . . . . . . . . . 101.4 Physics Deliverables of the Stage I of EIC . . . . . . . . . . . . . . . . . . . 12
2 Spin and Three-Dimensional Structure of the Nucleon 132.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.2 Longitudinal spin of the nucleon . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2.2 Status and Near Term Prospects . . . . . . . . . . . . . . . . . . . . 232.2.3 Open questions and the role of an EIC . . . . . . . . . . . . . . . . . 26
2.3 Confined Motion of Partons in Nucleons: TMDs . . . . . . . . . . . . . . . 342.3.1 Opportunites for measurements of TMDs at the EIC . . . . . . . . . 36
Semi-inclusive Deep Inelastic Scattering (SIDIS) . . . . . . . . . . . 37Access to the Gluon TMDs . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.4 Spatial imaging of quarks and gluons . . . . . . . . . . . . . . . . . . . . . . 43
2.4.1 Physics motivations and measurement principle . . . . . . . . . . . . 432.4.2 Processes and observables . . . . . . . . . . . . . . . . . . . . . . . . 452.4.3 Parton imaging now and in the next decade . . . . . . . . . . . . . . 472.4.4 Accelerator and detector requirements . . . . . . . . . . . . . . . . . 482.4.5 Parton imaging with the EIC . . . . . . . . . . . . . . . . . . . . . . 512.4.6 Opportunities with nuclei . . . . . . . . . . . . . . . . . . . . . . . . 56
3 The Nucleus: A Laboratory for QCD 583.1 Physics of High Gluon Densities in Nuclei . . . . . . . . . . . . . . . . . . . 63
3.1.1 Gluon Saturation: a New Regime of QCD . . . . . . . . . . . . . . . 63Nonlinear Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Classical Gluon Fields and the Nuclear “Oomph” Factor . . . . . . . 66Map of High Energy QCD and the Saturation Scale . . . . . . . . . 68Nuclear Structure Functions . . . . . . . . . . . . . . . . . . . . . . . 71Di�ractive Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.1.2 Key Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
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Introduction: Relevance of studying the properties of fundamental structure of matter to nuclear science. What are the big questions? Why is EIC the ONLY appropriate facility to address them? What would be the deliverables for the 1st Stage? How would EIC position US towards continued leadership in nuclear physics (including accelerator science)
12 PAGES
Request your input by August 24. Will go to Tribble-II pannel by August 27/28
1.1 INTRODUCTION Three big questions in QCD: • How are the sea quarks and gluons inside the nucleon distributed
in space, momentum, spin and flavor? • Where does the saturation of gluon densities set in? • How does the nuclear environment affect the distribution of gluons
and interactions of quarks in nuclei?
Why EIC? Why a collider is the right tool? Why is electron the right tool? Why is polarization of beams needed? How would nuclei help in addressing the gluon related questions? Why should heavy ion physicists care?
Monday, August 20, 12 The EIC White Paper 12
Monday, August 20, 12 The EIC White Paper 13
The scientific goals and the machine parameters for the EIC were delineated in delib-77
erations at a community wide program held at the Institute for Nuclear Theory (INT) [2].78
The physics goals were set by identifying critical questions in QCD that remain unanswered79
despite the significant experimental and theoretical progress made over the past decade. A80
White Paper being prepared for the broader nuclear science community presents a summary81
of those scientific goals, and a brief description of the golden measurement programs and82
accelerator and detector technology advances required to achieve them. This is an executive83
summary of that White Paper.84
1.2 Science Highlights of the Electron Ion Collider85
Figure 1.1: Evolution of our understanding of the nucleon spin: from a picture (1980s) in termsof constituent quarks alone, through incorporation (1990s/2000s) of contributions from gluonsand the orbital motion of quarks, to the present day picture, where many parton spins andtheir transverse motion contribute, resulting in a rich internal dynamics and 3D structure of thenucleon.
1.2.1 Nucleon Spin and its 3D Structure and Tomography86
Several decades of experiments on the deep inelastic scattering (DIS) of electron or muon87
beams o� nucleons have taught us a lot about how quarks and gluons (collectively called88
partons) share the momentum of a fast-moving nucleon. They have not, however, resolved89
the question of how partons share the nucleon’s spin. The earlier studies were also limited90
to provide a one-dimensional view of nucleon structure only. The EIC is designed to yield91
much greater insight into nucleon structure (Fig. 1.1, from left to right), by facilitating92
multi-dimensional maps of the distributions of partons in space, momentum (including93
momentum components transverse to the nucleon momentum), spin and flavor.94
The 12 GeV upgrade of CEBAF at JLab will start on such studies in the kinematic95
region of the valence quarks, but these will be dramatically extended at the EIC to explore96
the role of the gluons, dominant below the parton momentum fraction x � 0.2 or so, and97
sea quarks in determining the hadron structure and its properties, and to resolve crucial98
questions, such as whether the substantial “missing” portion of nucleon spin resides in the99
gluons. And by facilitating high-energy probes of transverse momentum, EIC should also100
illuminate the role of parton orbital motion within the nucleon.101
The Spin and Flavor Structure of the Nucleon:102
After an intensive and worldwide experimental program over the past two decades we have103
learned that the spin of quarks and antiquarks is only responsible for � 30% of the proton104
spin, while recent RHIC results indicate that the gluons spin contribution in the currently105
3
explored kinematic region is non-zero, but not yet su⌃cient to account for the missing 70%.106
With the unique capabilities to reach two orders of magnitude lower in parton momentum107
fraction x and to span a wider range of momentum exchange Q2 than fixed polarized target108
experiments, the EIC would o⇤er the most powerful tool to precisely quantify how the spin109
of gluons and that of quarks of various flavors contribute to the protons spin. The EIC could110
achieve this by colliding longitudinally polarized electrons and nucleons, with both inclu-111
sive DIS measurements, where only the scattered electron is detected, and semi-inclusive112
DIS (SIDIS) measurements, where, in addition, a hadron created in the collisions is to be113
detected and identified. Figure 1.2 (right) shows the reduction in uncertainties in the con-
x
Q2 (
Ge
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EIC √
s= 1
40 G
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CERN DESY JLab SLAC
Current polarized BNL-RHIC pp data:
PHENIX π0 STAR 1-jet
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Figure 1.2: The range in parton momentum fraction x vs. resolution Q2 (GeV2) accessible tothe EIC for di�erent center-of-mass energies (
�s=45 and 140 GeV) in comparison with points
representing the kinematics of existing experiments probing nucleon spin structure. . Right: Theprojected reduction of uncertainties on the gluon (�g) and net quark (�⇥/2) contributions toproton spin with the addition of inclusive and semi-inclusive DIS measurements at EIC. Theblue region indicates the uncertainty calculated in a next-to-leading perturbative QCD analysisof all presently published data and the red region indicates what could be achieved with modestrunning times at the EIC
114
tributions to the nucleon spin from the spin of the gluons, and quark-antiquarks, evaluated115
between a parton momentum fraction x from 0.001 to 1.0, which could be achieved by the116
EIC as it turns on in its early phases of operation. At later stages of the EIC operation, this117
range can be extended down to x > 0.0001, which will significantly reduce the uncertainty118
on the contributions from the full interval 0 < x < 1. The uncertainties calculated here are119
based on the state-of-the art theoretical treatment of all available world data related to the120
nucleon spin puzzle. Clearly, the EIC will make a huge impact unmatched by any other121
existing or anticipated facility on our knowledge of these quantities. The reduced uncer-122
tainties would definitively resolve the question of whether parton spin preferences alone can123
account for the overall proton spin, or whether additional contributions are needed from124
the orbital angular momentum of partons in the nucleon.125
The Confined Motion of Partons inside the Nucleon:126
The SIDIS measurements have two natural momentum scales: the large momentum transfer127
from the electron beam needed to achieve the desired spatial resolution, and the momentum128
of the produced hadrons perpendicular to the direction of the momentum transfer, which has129
a small value sensitive to the motion of confined partons. Remarkable theoretical advances130
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over the past decade have led to a rigorous framework where information on the confined131
motion of the partons inside a fast-moving nucleon is matched to transverse momentum132
dependent parton distributions (TMDs). In particular, TMDs are sensitive to correlations133
between the motion of partons and their spin, as well as the spin of the parent nucleon. These134
correlations can arise from spin-orbit coupling among the partons, about which very little135
is known to date. TMDs thus allow us to investigate the full three-dimensional dynamics136
of the proton, going well beyond the information about longitudional momentum contained137
in conventional parton distributions. With both electron and nucleon beams polarized at138
collider energies, the EIC will dramatically advance our knowledge of the motion of confined139
gluons and sea quarks in ways not achievable at any existing or proposed facility.140
Figure 3 (Left) shows the transverse-momentum distribution of up quarks in x and y141
(spatial) directions, inside a proton moving in the z direction (out of the drawing plane)142
with its spin polarized in the y direction. The anisotropy in transverse momentum induced143
by the proton polarization is described by the Sivers distribution function, whose very144
existence is a consequence of the color gauge invariance of QCD . While the figure is based145
on a preliminary extraction of this distribution from current experimental data, nothing146
is known about the spin and momentum correlations of the gluons and sea quarks. The147
achievable precision of the quark Sivers function from the EIC kinematics is also shown in148
Fig. 1.3 (right). Currently no data exist for extracting such a picture in the gluon-dominated149
region in the proton. The EIC would be crucial to initiate and realize such a program.
(GeV)xk
u quark
−0.5 0 0.5
yk
−0.5
0
0.5
Figure 1.3: Left: Transverse-momentum distribution of up quark in a transversely polarizedproton moving in z-direction, while polarized in y direction. Right: The transverse-momentumprofile of the Sivers function of valence up quark at five x values and corresponding uncertain-ties.
150
The Tomography of the Nucleon - Spatial Imaging of Gluons and Sea Quarks:151
By choosing particular final states in electron-proton scattering, the EIC would be able to152
selectively probe the transverse spatial distributions of sea quarks and gluons in the fast-153
moving proton as a function of the parton’s longitudinal momentum fraction x. This spatial154
imaging is a powerful way to go beyond normal DIS one-dimensional snapshots of nucleons,155
and is complementary to the extraction of TMDs in momentum space. Such tomographic156
information promises insight into the dynamics of confinement of partons within nucleons.157
With its broad range of collision energies, its high luminosity and nearly hermetic detectors,158
the EIC could image the proton with unprecedented detail and precision from small to159
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large transverse distances. The accessible parton momentum fractions x extend from a160
region dominated by sea quarks and gluons to one where valence quarks become important,161
allowing the connection to the precise images expected from the 12 GeV upgrade at JLab.162
This is exemplified in Fig. 1.4, which shows the unprecedented precision expected for the163
spatial distribution of gluons as measured in the exclusive process: electron + proton �164
electron + J/� + proton.165
The tomographic images obtained from cross sections and polarization asymmetries for166
exclusive processes are encoded in generalized parton distributions (GPDs) that unify the167
concepts of parton densities and of elastic form factors. They contain detailed information168
about spin-orbit correlations and the angular momentum carried by partons, including their169
spin and their orbital motion. With the combined kinematic coverage of EIC and of the170
upgraded CEBAF, we shall obtain meaningful constraints on the quark orbital angular171
momentum contribution to the protons spin.172
bT (fm)
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Figure 1.4: Projected precision of the transverse spatial distribution of gluons as extractedfrom exclusive J/� production. bT is the distance of the gluon from the center of the proton,whereas the kinematic quantity xV determines the gluon momentum fraction. The collisionenergies assumed for stage-I and stage-II are Ee = 5 GeV, Ep = 100 GeV and Ee = 20 GeV,Ep = 250 GeV, respectively. The intermediate xV bin is accessible with either energy settingand gives almost identical uncertainty bands in both cases.
1.2.2 The Nucleus, a Laboratory for QCD173
The atomic nucleus is a “molecule” in QCD, made of nucleons, which, in turn, are174
bound states of quarks and gluons. Understanding the emergence of nuclei from QCD is175
an ultimate long-term goal of nuclear physics. With its wide kinematic reach, as shown in176
Fig. 5 (Left), the capability to probe a variety of nuclei in both inclusive and semi-inclusive177
DIS measurements, the EIC would be the first experimental facility capable of exploring the178
internal 3-dimensional sea quark and gluon structure of a fast-moving nucleus. Furthermore,179
the nucleus itself would be an unprecedented QCD laboratory for discovering the collective180
behavior of gluonic matter of high density, and for studying the propagation of a fast-moving181
color charge in a nuclear medium.182
6
Executive Summary: Cartoons and Figures
Figures from the ES
Physics with polarized nucleon
Monday, August 20, 12 The EIC White Paper 14
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Measurements with A ≥ 56 (Fe):
eA/μA DIS (E-139, E-665, EMC, NMC)
νA DIS (CCFR, CDHSW, CHORUS, NuTeV)
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Figure 1.5: Left: The resolution (Q2) vs. the parton momentum fraction (x) landscape ofavailable data points for lepton-nucleus (DIS) and Drell-Yan (DY) experiments at fixed targetenergies, compared to the kinematic reach of the EIC at two di�erent center of mass energies.Right: Schematic map of high energy QCD in the resolution (Q2) vs. energy (Y=ln(1/x))plane. The high gluon density saturation region is shown.
QCD at Extreme Parton Density:183
In QCD, the large soft gluon density enables the non-linear process of gluon-gluon recom-184
bination to limit the density growth. Such a QCD self-regulation mechanism necessarily185
generates a dynamic scale from the interaction of high density massless gluons, known as186
the saturation scale, Qs, at which gluon splitting and recombination reach a balance. At187
this scale the density of gluons is expected to saturate, producing new and universal prop-188
erties of hadronic matter. The saturation scale Qs separates the condensed and saturated189
soft gluonic matter from the dilute but confined quarks and gluons in a hadron, as shown190
in Fig. 1.5 (Right).191
The existence of such a saturated soft gluon matter, often referred to as Color Glass192
Condensate, is a direct consequence of gluon self-interaction in QCD. The dynamic sat-193
uration scale Qs may be impossible to reach unambiguously in electron-proton scattering194
without a multi-TeV proton beam. However, heavy ion beams provide precocious access to195
the saturation regime because the virtual photon in forward lepton scattering probes matter196
coherently over a characteristic length proportional to 1/xp, which can exceed the diameter197
of a Lorentz-contracted nucleus. Then all the gluons at a given impact parameter of the198
nucleus, enhanced by the nuclear diameter proportional to A1/3 with the atomic weight199
A, contribute to the probed density, reaching saturation at far lower energies than would200
be needed in electron-proton collisions. While HERA, RHIC and LHC only found hints of201
saturated gluonic matter, the EIC would have the potential to seal the case, completing the202
process started at those facilities.203
Figure 1.6 illustrates some of the dramatic predicted e�ects of gluon density saturation in204
electron-nucleus vs. electron-proton collisions at an EIC. The left frame considers coherent205
di�ractive processes, defined to include all events in which the beam nucleus remains intact206
and there is a rapidity gap containing no produced particles. As shown in the figure, gluon207
saturation greatly enhances the fraction of the total cross section accounted for by such208
events. An early measurement of coherent di�raction in e+A collisions at the EIC would209
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J/ψ no saturation
J/ψ saturation (bSat)
Experimental Cuts:|η(Vdecay products)| < 4p(Vdecay products) > 1 GeV/c
Coherent events only
stage-II, ∫Ldt = 10 fb-1/A
x < 0.01
Figure 1.6: Left:The predicted double ratio of the coherent di�ractive and total cross sectionsin electron-gold (eA) and electron-proton (ep) collisions plotted as a function of the invariantmass M2
X of the produced particles, with and without incorporation of gluon saturation. Thebands indicate projected statistical and systematic measurement uncertainties with EIC. Right:Ratios of eA to ep cross-sections for J/⇥ (blue) and � (red) production with (square) and without(circle) gluon saturation. The statistical uncertainties possible with measurements at the EICare indicated by the error bars.
provide the first unambiguous evidence for gluon saturation.210
Figure 1.6 (Right) shows that gluon saturation is predicted to suppress vector meson211
production in e+A relative to e+p collisions at EIC. The vector mesons result from quark-212
antiquark pair fluctuations of the virtual photon, which hadronize upon exchange of gluons213
with the beam proton or nucleus. The magnitude of the suppression depends on the size (or214
color dipole moment) of the quark-antiquark pair, being significantly larger for produced �215
(red points) than for J/⇥ (blue) mesons. An EIC measurement of the processes in Fig. 1.6216
(Right) would provide a powerful probe to diagnose the characteristics of the saturated217
gluons.218
Propagation of a Color Charge in QCD Matter:219
One of the key pieces of evidence for the discovery of quark-gluon plasma (QGP) at RHIC220
is jet quenching, manifested as a strong suppression of fast-moving hadrons produced in221
the very hot matter created in relativistic heavy ion collisions. The suppression is believed222
to be due to the energy loss of partons traversing the QGP. It has been puzzling that the223
production is nearly as much suppressed for heavy as for light mesons, even though a heavy224
quark is much less likely to lose its energy via medium-induced radiation of gluons. Some of225
the remaining mysteries surrounding heavy vs. light quark interactions in hot matter can226
be illuminated by EIC studies of related phenomena in cold nuclear matter. For example,227
the variety of ion beams available for electron-nucleus collisions at the EIC would provide228
a femtometer filter to test and to help determine the correct mechanism by which quarks229
and gluons lose energy and hadronize in nuclear matter (see schematic in Fig. 1.7 (Left)).230
Figure 1.7 (Right) shows the ratio of number of produced mesons in electron-nucleus231
and electron-deuteron collisions for pion (light mesons) and D0-mesons (heavy mesons) at232
8
0.30
0.50
0.70
0.90
1.10
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zM
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io
D0 mesons (lower energy)Pions (lower energy)D0 mesons (higher energy)Pions (higher energy)D0 (10% less energy loss)Wang, pions (lower energy)Wang, pions (higher energy)
0.01 < y < 0.85, x > 0.1, 10 fb-1
Higher energy: 25 GeV2< Q
2< 45 GeV
2, 140 GeV < < 150 GeV
Lower energy : 8 GeV 2< Q
2<12 GeV2, 32.5 GeV< < 37.5 GeV
1- D0systematic
uncertainty
1- pion systematicuncertainty
v
v
0.0 0.2 0.4 0.6 0.8 1.0
Figure 1.7: Left: Schematic drawings explaining interactions of the parton moving throughcold nuclear matter: the hadron is formed outside (top) or inside (bottom) the nucleus.Right:Ratio of semi-inclusive cross section for producing a pion (red), composed of light quarks, anda D0 meson (blue) composed of heavy quarks in electron-Lead collisions to the same producedin electron-deuteron as function of z, the momentum fraction of the exchanging photon carriedby the observed meson. Statistical uncertainties are shown in each case.
both low and high photon energy �, as a function of z - the momentum fraction of the233
virtual photon taken by the observed meson. The calculation of red lines and blue symbols234
assumes the mesons are formed outside of the nucleus, as shown in the top sketch of Fig. 1.7235
(Left), while the square symbols are simulated according to a model where a color neutral236
pre-hadron was formed inside the nucleus, like in the bottom sketch of Fig. 1.7 (Left).237
The di�erence between the red lines and the red square symbols would provide the first238
direct information on when the meson is formed. Unlike the suppression expected for pion239
production at all z, the ratio of heavy meson production could be larger than the unity240
due to very di�erent hadronization properties of heavy mesons. The discovery of such a241
dramatic di�erence in multiplicity ratios between light and heavy mesons at the EIC would242
shed light on the hadronization process and what governs the transition from quarks to243
hadrons.244
The Distribution of Quarks and Gluons in the Nucleus:245
The EMC experiment at CERN and experiments in the following two decades clearly re-246
vealed that the distribution of quarks in a fast-moving nucleus is not a simple superposition247
of their distributions within nucleons. Instead, the ratio of nuclear over nucleon structure248
functions follows a non-trivial function of Bjorken xB, deviating significantly from unity,249
with a suppression (often referred to as nuclear shadowing) as xB decreases. Amazingly,250
there is as of yet no knowledge whether the same holds true for gluons. With its much251
wider kinematic reach in both x and Q, the EIC could measure the suppression of the252
structure functions to a much lower value of x, approaching the region of gluon saturation.253
In addition, the EIC could for the first time reliably quantify the nuclear gluon distribution254
over a wide range of momentum fraction x. With its unprecedented luminosity, the EIC255
9
Figures from the ES
Physics with Nuclei
Monday, August 20, 12 The EIC White Paper 15
eSTAR
ePH
EN
IX
30 GeV
30 GeV
100 m
Lina
c 2.
45 G
eV
Linac 2.45 GeV
Coh
eren
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oole
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0.60 GeV
5.50 GeV
10.4 GeV
15.3 GeV
20.2 GeV
25.1 GeV
30.0 GeV
3.05 GeV
7.95 GeV
12.85 GeV
17.75 GeV
22.65 GeV
27.55 GeV
0.6 GeV
0.6 GeV
27.55 GeV
New detector
Figure 1.8: Top: The schematic of eRHIC at BNL: will require construction of the electronbeam facility (indicated in RED) to collide with the RHIC blue beam at three interaction points.Bottom: The schematic of the ELIC at JLab: will require construction of the ELIC complex(red and black in the center) and its injector (shown in green, top right) next to the 12 GeVCEBAF.
the accelerator a particularly challenging feature of the design. Lessons learned from past ex-296
perience at HERA have been considered while designing the EIC interaction region. Driven297
by the demand for high precision on particle detection and identification of final state par-298
ticles in both e-p and e-A programs, modern particle detector systems will be at the heart299
of the EIC. In order to keep the detector costs manageable, R&D e�orts are under way300
on various novel ideas for: compact (fiber sampling & crystal) calorimetry, tracking (NaI301
coated GEMs, GEM size & geometries), particle identification (compact DIRC, dual ra-302
diator RICH & novel TPC) and high radiation tolerance for electronics. Meeting these303
R&D challenges will keep the U.S. nuclear science community at the cutting edge in both304
accelerator and detector technology.305
11
Figures from the ES
BEYOND AUGUST 24TH: FINALIZING THE WP Aim at a time line which prepares the final WP around the DNP Townhall meetings (last week of October)
Monday, August 20, 12 The EIC White Paper 16
Monday, August 20, 12 The EIC White Paper 17
Contents
1 Exploring the Glue that Binds Us All – The Executive Summary 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Science Highlights of the Electron Ion Collider . . . . . . . . . . . . . . . . 3
1.2.1 Nucleon Spin and its 3D Structure and Tomography . . . . . . . . . 31.2.2 The Nucleus, a Laboratory for QCD . . . . . . . . . . . . . . . . . . 61.2.3 Physics Possibilities at the Intensity Frontier . . . . . . . . . . . . . 10
1.3 The Electron Ion Collider and its Realization . . . . . . . . . . . . . . . . . 101.4 Physics Deliverables of the Stage I of EIC . . . . . . . . . . . . . . . . . . . 12
2 Spin and Three-Dimensional Structure of the Nucleon 132.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.2 Longitudinal spin of the nucleon . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2.2 Status and Near Term Prospects . . . . . . . . . . . . . . . . . . . . 232.2.3 Open questions and the role of an EIC . . . . . . . . . . . . . . . . . 26
2.3 Confined Motion of Partons in Nucleons: TMDs . . . . . . . . . . . . . . . 342.3.1 Opportunites for measurements of TMDs at the EIC . . . . . . . . . 36
Semi-inclusive Deep Inelastic Scattering (SIDIS) . . . . . . . . . . . 37Access to the Gluon TMDs . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.4 Spatial imaging of quarks and gluons . . . . . . . . . . . . . . . . . . . . . . 43
2.4.1 Physics motivations and measurement principle . . . . . . . . . . . . 432.4.2 Processes and observables . . . . . . . . . . . . . . . . . . . . . . . . 452.4.3 Parton imaging now and in the next decade . . . . . . . . . . . . . . 472.4.4 Accelerator and detector requirements . . . . . . . . . . . . . . . . . 482.4.5 Parton imaging with the EIC . . . . . . . . . . . . . . . . . . . . . . 512.4.6 Opportunities with nuclei . . . . . . . . . . . . . . . . . . . . . . . . 56
3 The Nucleus: A Laboratory for QCD 583.1 Physics of High Gluon Densities in Nuclei . . . . . . . . . . . . . . . . . . . 63
3.1.1 Gluon Saturation: a New Regime of QCD . . . . . . . . . . . . . . . 63Nonlinear Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Classical Gluon Fields and the Nuclear “Oomph” Factor . . . . . . . 66Map of High Energy QCD and the Saturation Scale . . . . . . . . . 68Nuclear Structure Functions . . . . . . . . . . . . . . . . . . . . . . . 71Di�ractive Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.1.2 Key Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3
Monday, August 20, 12 The EIC White Paper 18
Structure Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Di-Hadron Correlations . . . . . . . . . . . . . . . . . . . . . . . . . 79Measurements of Di�ractive Events . . . . . . . . . . . . . . . . . . . 82
3.2 Quarks and gluons in the nucleus . . . . . . . . . . . . . . . . . . . . . . . . 863.2.1 The distributions of quarks and gluons in a nucleus . . . . . . . . . . 873.2.2 Propagation of a fast moving color charge in QCD matter . . . . . . 903.2.3 Strong color fluctuations inside a large nucleus . . . . . . . . . . . . 93
3.3 Connections to pA, AA and Cosmic Ray Physics . . . . . . . . . . . . . . . 943.3.1 Connections to pA Physics . . . . . . . . . . . . . . . . . . . . . . . 943.3.2 Connections to Ultrarelativistic Heavy-Ion Physics . . . . . . . . . . 97
Initial Conditions in AA collisions . . . . . . . . . . . . . . . . . . . 98Energy Loss and Hadronization . . . . . . . . . . . . . . . . . . . . . 102
3.3.3 Connections to Cosmic Ray Physics . . . . . . . . . . . . . . . . . . 104
4 Possibilities at the Luminosity Frontier: Physics Beyond the StandardModel 1064.1 Specific Opportunities in Electroweak Physics . . . . . . . . . . . . . . . . . 107
4.1.1 Charged Lepton Flavor Violation . . . . . . . . . . . . . . . . . . . . 1074.1.2 Precision Measurements of Weak Neutral Current Couplings . . . . 108
4.2 EIC Requirements for Electroweak Physics Measurements . . . . . . . . . . 111
5 The Accelerator Designs and Challenges 1125.1 eRHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.1.1 eRHIC design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145.1.2 eRHIC interaction region . . . . . . . . . . . . . . . . . . . . . . . . 1165.1.3 eRHIC R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.2 MEIC: The Je�erson Lab Implementation . . . . . . . . . . . . . . . . . . . 1185.2.1 Je�erson Lab Staged Approach . . . . . . . . . . . . . . . . . . . . . 1185.2.2 Baseline Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Ion Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Collider Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Interaction Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Electron Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6 The EIC Detector Requirements and Design Ideas 1256.1 Kinematic Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1 y Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256.1.2 Angle and momentum distributions . . . . . . . . . . . . . . . . . . 1266.1.3 Recoil Baryon angles and t resolution . . . . . . . . . . . . . . . . . 130
6.2 Detector and Interaction Region (IR) Layout . . . . . . . . . . . . . . . . . 1306.2.1 eRHIC Detector & IR Considerations and Technologies . . . . . . . 1306.2.2 Detector Design for MEIC/ELIC . . . . . . . . . . . . . . . . . . . . 133
Acknowledgment 137
References 138
4
Contents
1 Exploring the Glue that Binds Us All – The Executive Summary 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Science Highlights of the Electron Ion Collider . . . . . . . . . . . . . . . . 3
1.2.1 Nucleon Spin and its 3D Structure and Tomography . . . . . . . . . 31.2.2 The Nucleus, a Laboratory for QCD . . . . . . . . . . . . . . . . . . 61.2.3 Physics Possibilities at the Intensity Frontier . . . . . . . . . . . . . 10
1.3 The Electron Ion Collider and its Realization . . . . . . . . . . . . . . . . . 101.4 Physics Deliverables of the Stage I of EIC . . . . . . . . . . . . . . . . . . . 12
2 Spin and Three-Dimensional Structure of the Nucleon 132.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.2 Longitudinal spin of the nucleon . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2.2 Status and Near Term Prospects . . . . . . . . . . . . . . . . . . . . 232.2.3 Open questions and the role of an EIC . . . . . . . . . . . . . . . . . 26
2.3 Confined Motion of Partons in Nucleons: TMDs . . . . . . . . . . . . . . . 342.3.1 Opportunites for measurements of TMDs at the EIC . . . . . . . . . 36
Semi-inclusive Deep Inelastic Scattering (SIDIS) . . . . . . . . . . . 37Access to the Gluon TMDs . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.4 Spatial imaging of quarks and gluons . . . . . . . . . . . . . . . . . . . . . . 43
2.4.1 Physics motivations and measurement principle . . . . . . . . . . . . 432.4.2 Processes and observables . . . . . . . . . . . . . . . . . . . . . . . . 452.4.3 Parton imaging now and in the next decade . . . . . . . . . . . . . . 472.4.4 Accelerator and detector requirements . . . . . . . . . . . . . . . . . 482.4.5 Parton imaging with the EIC . . . . . . . . . . . . . . . . . . . . . . 512.4.6 Opportunities with nuclei . . . . . . . . . . . . . . . . . . . . . . . . 56
3 The Nucleus: A Laboratory for QCD 583.1 Physics of High Gluon Densities in Nuclei . . . . . . . . . . . . . . . . . . . 63
3.1.1 Gluon Saturation: a New Regime of QCD . . . . . . . . . . . . . . . 63Nonlinear Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Classical Gluon Fields and the Nuclear “Oomph” Factor . . . . . . . 66Map of High Energy QCD and the Saturation Scale . . . . . . . . . 68Nuclear Structure Functions . . . . . . . . . . . . . . . . . . . . . . . 71Di�ractive Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.1.2 Key Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3
Monday, August 20, 12 The EIC White Paper 19
Structure Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Di-Hadron Correlations . . . . . . . . . . . . . . . . . . . . . . . . . 79Measurements of Di�ractive Events . . . . . . . . . . . . . . . . . . . 82
3.2 Quarks and gluons in the nucleus . . . . . . . . . . . . . . . . . . . . . . . . 863.2.1 The distributions of quarks and gluons in a nucleus . . . . . . . . . . 873.2.2 Propagation of a fast moving color charge in QCD matter . . . . . . 903.2.3 Strong color fluctuations inside a large nucleus . . . . . . . . . . . . 93
3.3 Connections to pA, AA and Cosmic Ray Physics . . . . . . . . . . . . . . . 943.3.1 Connections to pA Physics . . . . . . . . . . . . . . . . . . . . . . . 943.3.2 Connections to Ultrarelativistic Heavy-Ion Physics . . . . . . . . . . 97
Initial Conditions in AA collisions . . . . . . . . . . . . . . . . . . . 98Energy Loss and Hadronization . . . . . . . . . . . . . . . . . . . . . 102
3.3.3 Connections to Cosmic Ray Physics . . . . . . . . . . . . . . . . . . 104
4 Possibilities at the Luminosity Frontier: Physics Beyond the StandardModel 1064.1 Specific Opportunities in Electroweak Physics . . . . . . . . . . . . . . . . . 107
4.1.1 Charged Lepton Flavor Violation . . . . . . . . . . . . . . . . . . . . 1074.1.2 Precision Measurements of Weak Neutral Current Couplings . . . . 108
4.2 EIC Requirements for Electroweak Physics Measurements . . . . . . . . . . 111
5 The Accelerator Designs and Challenges 1125.1 eRHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.1.1 eRHIC design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145.1.2 eRHIC interaction region . . . . . . . . . . . . . . . . . . . . . . . . 1165.1.3 eRHIC R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.2 MEIC: The Je�erson Lab Implementation . . . . . . . . . . . . . . . . . . . 1185.2.1 Je�erson Lab Staged Approach . . . . . . . . . . . . . . . . . . . . . 1185.2.2 Baseline Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Ion Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Collider Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Interaction Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Electron Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6 The EIC Detector Requirements and Design Ideas 1256.1 Kinematic Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1 y Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256.1.2 Angle and momentum distributions . . . . . . . . . . . . . . . . . . 1266.1.3 Recoil Baryon angles and t resolution . . . . . . . . . . . . . . . . . 130
6.2 Detector and Interaction Region (IR) Layout . . . . . . . . . . . . . . . . . 1306.2.1 eRHIC Detector & IR Considerations and Technologies . . . . . . . 1306.2.2 Detector Design for MEIC/ELIC . . . . . . . . . . . . . . . . . . . . 133
Acknowledgment 137
References 138
4
Structure Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Di-Hadron Correlations . . . . . . . . . . . . . . . . . . . . . . . . . 79Measurements of Di�ractive Events . . . . . . . . . . . . . . . . . . . 82
3.2 Quarks and gluons in the nucleus . . . . . . . . . . . . . . . . . . . . . . . . 863.2.1 The distributions of quarks and gluons in a nucleus . . . . . . . . . . 873.2.2 Propagation of a fast moving color charge in QCD matter . . . . . . 903.2.3 Strong color fluctuations inside a large nucleus . . . . . . . . . . . . 93
3.3 Connections to pA, AA and Cosmic Ray Physics . . . . . . . . . . . . . . . 943.3.1 Connections to pA Physics . . . . . . . . . . . . . . . . . . . . . . . 943.3.2 Connections to Ultrarelativistic Heavy-Ion Physics . . . . . . . . . . 97
Initial Conditions in AA collisions . . . . . . . . . . . . . . . . . . . 98Energy Loss and Hadronization . . . . . . . . . . . . . . . . . . . . . 102
3.3.3 Connections to Cosmic Ray Physics . . . . . . . . . . . . . . . . . . 104
4 Possibilities at the Luminosity Frontier: Physics Beyond the StandardModel 1064.1 Specific Opportunities in Electroweak Physics . . . . . . . . . . . . . . . . . 107
4.1.1 Charged Lepton Flavor Violation . . . . . . . . . . . . . . . . . . . . 1074.1.2 Precision Measurements of Weak Neutral Current Couplings . . . . 108
4.2 EIC Requirements for Electroweak Physics Measurements . . . . . . . . . . 111
5 The Accelerator Designs and Challenges 1125.1 eRHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.1.1 eRHIC design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145.1.2 eRHIC interaction region . . . . . . . . . . . . . . . . . . . . . . . . 1165.1.3 eRHIC R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.2 MEIC: The Je�erson Lab Implementation . . . . . . . . . . . . . . . . . . . 1185.2.1 Je�erson Lab Staged Approach . . . . . . . . . . . . . . . . . . . . . 1185.2.2 Baseline Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Ion Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Collider Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Interaction Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Electron Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6 The EIC Detector Requirements and Design Ideas 1256.1 Kinematic Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1 y Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256.1.2 Angle and momentum distributions . . . . . . . . . . . . . . . . . . 1266.1.3 Recoil Baryon angles and t resolution . . . . . . . . . . . . . . . . . 130
6.2 Detector and Interaction Region (IR) Layout . . . . . . . . . . . . . . . . . 1306.2.1 eRHIC Detector & IR Considerations and Technologies . . . . . . . 1306.2.2 Detector Design for MEIC/ELIC . . . . . . . . . . . . . . . . . . . . 133
Acknowledgment 137
References 138
4
Monday, August 20, 12 The EIC White Paper 20
Structure Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Di-Hadron Correlations . . . . . . . . . . . . . . . . . . . . . . . . . 79Measurements of Di�ractive Events . . . . . . . . . . . . . . . . . . . 82
3.2 Quarks and gluons in the nucleus . . . . . . . . . . . . . . . . . . . . . . . . 863.2.1 The distributions of quarks and gluons in a nucleus . . . . . . . . . . 873.2.2 Propagation of a fast moving color charge in QCD matter . . . . . . 903.2.3 Strong color fluctuations inside a large nucleus . . . . . . . . . . . . 93
3.3 Connections to pA, AA and Cosmic Ray Physics . . . . . . . . . . . . . . . 943.3.1 Connections to pA Physics . . . . . . . . . . . . . . . . . . . . . . . 943.3.2 Connections to Ultrarelativistic Heavy-Ion Physics . . . . . . . . . . 97
Initial Conditions in AA collisions . . . . . . . . . . . . . . . . . . . 98Energy Loss and Hadronization . . . . . . . . . . . . . . . . . . . . . 102
3.3.3 Connections to Cosmic Ray Physics . . . . . . . . . . . . . . . . . . 104
4 Possibilities at the Luminosity Frontier: Physics Beyond the StandardModel 1064.1 Specific Opportunities in Electroweak Physics . . . . . . . . . . . . . . . . . 107
4.1.1 Charged Lepton Flavor Violation . . . . . . . . . . . . . . . . . . . . 1074.1.2 Precision Measurements of Weak Neutral Current Couplings . . . . 108
4.2 EIC Requirements for Electroweak Physics Measurements . . . . . . . . . . 111
5 The Accelerator Designs and Challenges 1125.1 eRHIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.1.1 eRHIC design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145.1.2 eRHIC interaction region . . . . . . . . . . . . . . . . . . . . . . . . 1165.1.3 eRHIC R&D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.2 MEIC: The Je�erson Lab Implementation . . . . . . . . . . . . . . . . . . . 1185.2.1 Je�erson Lab Staged Approach . . . . . . . . . . . . . . . . . . . . . 1185.2.2 Baseline Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Ion Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Collider Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Interaction Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Electron Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6 The EIC Detector Requirements and Design Ideas 1256.1 Kinematic Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1 y Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256.1.2 Angle and momentum distributions . . . . . . . . . . . . . . . . . . 1266.1.3 Recoil Baryon angles and t resolution . . . . . . . . . . . . . . . . . 130
6.2 Detector and Interaction Region (IR) Layout . . . . . . . . . . . . . . . . . 1306.2.1 eRHIC Detector & IR Considerations and Technologies . . . . . . . 1306.2.2 Detector Design for MEIC/ELIC . . . . . . . . . . . . . . . . . . . . 133
Acknowledgment 137
References 138
4
White Paper path forward: • After ES is finalized and sent to the Tribble-II (end of August)
• Present the WP (distribute the link of the WP draft) to the BNL and Jlab User communities, EIC collaboration lists
• Comments gathered by a web based system that was used recently by Jefferson Laboratory for its 12-GeV White Paper.
• Identical systems will be setup both at BNL and JLab
• Approximately 2 weeks for the comments period • Approximately 2 week for the conveners of sections to
accommodate them • 1 week for (JQ, Z-EM & AD) to finalize the WP beyond that
• Aim for a final WP in the last week of October. To the BNL/Jlab managements in November
Monday, August 20, 12 The EIC White Paper 21
Feedback on the White Paper Keeping in mind the following things: Intended for the broader Nuclear Physics audience [High energy NP: Jlab, RHIC, but also, FRIB-community, symmetry violation seekers, theorists] who would influence the decision on EIC in the next Long Range Plan. Comprehensiveness less important than being concise and articulating the case most effectively. Length can not increase, can we reduce it to about 100 pages?
Monday, August 20, 12 The EIC White Paper 22
Feedback on the White Paper (Method and Dates on when, will be conveyed to you soon)
• What other things absolutely needed to strengthen the case for the EIC?
• Are there parts of current draft which are detrimental to making the case for the EIC?
• Are relative emphases and lengths amongst chapters & within chapters correct?
• Are there mistakes in the physics? • Can the presentation/articulation improve by simple changes
to the structure of the sections, inclusion of new things (replacing current parts)
• Are there better figures/cartoons which could be used?
Monday, August 20, 12 The EIC White Paper 23
Summary: • A good draft of the EIC White Paper is now ready, and was
released (for the first time) to THIS audience
• We anticipate your comments and suggestions on the Executive Summary (12 Pages) by August 24. We hope to send the improved draft to the Tribble-II panel by August 28. • Comments by email to Abhay, Jianwei and Zein-Eddine
• The comments on the rest of the White Paper: welcome but at a later date. We aim to finalize the WP by the end of October, November. Method of making the comments and the timelines will be distributed soon.
Monday, August 20, 12 The EIC White Paper 24