An Assessment of U.S.-Based Electron-Ion Collider Science (2018) / Chapter Skim
Currently Skimming:
5 Comparison of a U.S.-Based Electron-Ion Collider to Current and Future Facilities
5 Comparison of a U.S.-Based Electron-Ion Collider to Current and Future Facilities
Pages 82-104
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 82... ...
, the only lepton-hadron collider that has operated to date, and moving on to survey other types of accelerators and colliders that are presently operating and whose physics programs are related to that of the EIC. Finally, other proposals for possible future machines are discussed.
|
From page 83... ...
HERA was designed for the needs of the high-energy particle physics community, primarily to search for new physics beyond the Standard Model. However, given that it discovered no new physics, HERA is remembered mainly for the wealth of electroweak and quantum chromodynamics (QCD)
|
From page 84... ...
fixed-target experiment used HERA's electron and posi tron beams on a variety of stationary targets, including longitudinally and trans versely polarized proton targets and nuclear targets. The longitudinally polarized lepton beam in HERA permitted a variety of measurements on polarized targets in various configurations.
|
From page 85... ...
CEBAF AT JLAB The valence quark region, which will be a focus of the 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) science program, is an important bridge connecting to the gluon and sea quark region accessible by an EIC.
|
From page 86... ...
During 6 GeV operations the users performed 178 experiments. CEBAF was recently upgraded to deliver continuous electron beams to the experimental users at a maximum energy of 12 GeV.
|
From page 87... ...
. The energyupgraded CEBAF accelerator is capable of delivering beams simultaneously to all four halls, up to 11 GeV electrons to Halls A, B, and C, and a 12 GeV electron beam to Hall D for producing 9 GeV tagged photons for meson spectroscopy, complementary to spectroscopy at the Large Hadron Collider (LHC)
|
From page 88... ...
The resulting multidimensional distribution functions provide tomographic imaging of the nucleon and insight into the QCD dynamics inside the nucleon. Extensive programs on GPDs and TMDs are planned for Halls A, B, and C in the large x, also called "valence quark," region with a 12 GeV CEBAF.
|
From page 89... ...
Continued running is currently planned through 2018, and there is a proposal to extend COMPASS data taking through 2021. The muon beam physics program includes lepton scattering and exclusive measurements on nuclear targets containing both longitudinally and transversely polarized nucleons.
|
From page 90... ...
The EIC will additionally perform a com prehensive program of lepton scattering and exclusive measurements on nuclei. RHIC AT BROOKHAVEN NATIONAL LABORATORY RHIC Collider The RHIC, which has operated at Brookhaven National Laboratory (BNL)
|
From page 91... ...
This experience is a crucial foundation for an EIC that must also accelerate and store polarized proton beams. Projections for the RHIC collider extending to 2027, with a variety of nuclei and further polarized proton performance, have been given.6 The RHIC Physics Program Within the Context of the EIC In operation since 2000, RHIC was designed to study QCD, with focus on high energy densities, the creation and study of a quark-gluon plasma, and the polarized structure of the proton.
|
From page 92... ...
92 An Assessment of U.S.-Based Electron-Ion Collider Science FIGURE 5.4 Aluminum tubes with spiraling grooves were used for the construction of 48 full-twist superconducting helical dipoles for the Siberian snakes and spin rotators that allowed the acceleration and collision of up to 250 GeV polarized protons at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. SOURCE: Brookhaven National Laboratory.
|
From page 93... ...
The EIC will combine the strengths of the kinematic reach at a collider with the discriminating power of a lepton probe to elucidate the nucleon's internal spin structure. The study of the quark-gluon plasma and exploration of the QCD phase diagram are not part of the EIC physics program; however, improving knowledge of the partonic structure of nuclei is part of both the RHIC heavy ion and EIC physics programs.
|
From page 94... ...
An EIC, with a lepton beam on a variety of light and heavy nuclei at a range of center-of-mass energies, would make precision measurements of the flavor-separated partonic structure of nuclei through inclusive, semi-inclusive, and exclusive observables, comparable to similar measurements performed on protons. In the clean environ ment of lepton-nucleus collisions, and with critical kinematic coverage allowing calculations of observables sensitive to gluon saturation effects using both theoreti cal techniques specific to a saturation regime and traditional perturbative methods of calculation in QCD, definitive studies of gluon saturation will be possible at an EIC.
|
From page 95... ...
took place recently, demonstrating the capability of the CERN complex to accelerate and collide other species if required in the future. The total energy concentrated into nuclear volumes in the LHC's Pb-Pb collisions, at over 1,000 TeV, is by far the highest achieved to date in any human-made particle collision.
|
From page 96... ...
These studies are being extended to pPb collisions leading to results on gluon distributions in heavy nuclei at low x, that is, deep into the saturation region. Unfortunately, Q2 cannot be varied independently.
|
From page 97... ...
Since photonuclear cross sections scale, at leading order, as the square of the gluon distribution in the relevant nucleus, they provide an excellent tool to probe gluon distributions at low x, albeit at fixed (low)
|
From page 98... ...
Such a measurement would put attempts to study whether the strong, electromagnetic, and weak forces become 17 A Bracco et al., eds., 2016, "NuPECC Long Range Plan 2017 Perspectives in Nuclear Physics," European Science Foundation, http://www.nupecc.org/lrp2016/Documents/lrp2017.pdf.
|
From page 99... ...
Zimmermann, 2017, "Future Circular Collider Study FCC-he Baseline Parameters," CERN-ACC-2017-0019, April, http://cds.cern.ch/record/2260408, accessed August 13, 2018. comparable in strength at the grand unification scale, some 1016 GeV, on a firm footing.
|
From page 100... ...
Zimmermann, 2017, Future Circular Collider Study FCC-he Baseline Parameters, CERN-ACC-2017-0019, April, http://cds.cern. ch/record/2260408, accessed August 13, 2018.
|
From page 101... ...
The knowledge of fragmentation functions has made it possible, for example, to relate neutral pion production in polarized proton collisions to the gluon spin distribution in the polarized proton, thereby complementing the insights gained from jet measurements at RHIC. Recent fragmentation measurements with Belle at the KEK B-factory have revealed a rich interplay between spin and transverse momenta, which enable determinations of quark transversity, a quark spin distribution related to the nucleon tensor charge and electric dipole moment from the azimuthal distributions of hadrons produced
|
From page 102... ...
Its main physics focus will be in four research areas: atomic physics, plasma physics, and applications; nuclear matter physics with the High Acceptance Dielectron Spectrometer and Compressed Baryonic Matter detectors; nuclear structure, astrophysics, and reactions with the Nuclear Structure, Astrophysics, and Reactions detectors; and physics with high-energy antiprotons with the PANDA detector. While much of the FAIR physics program is concentrated on areas outside the focus of an EIC, the PANDA experiment plans to measure processes like proton + antiproton → 2 photons and proton + antiproton → dileptons.
|
From page 103... ...
The primary proton beam of 30 GeV at J-PARC is slowly extracted from the Main Ring accelerator and transported to the production target in the experimental hall. Various secondary particles, such as K and π mesons produced in the target, are transported through the secondary beam lines to the experimental area and are used for particle and nuclear physics experiments.
|
From page 104... ...
It is planned to study the spin-dependent Drell-Yan process us ing both longitudinally and transversely polarized protons and deuterons to extract new parton distribution functions in a much lower kinematic range than at an EIC.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.