Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session 1WD: Future Directions in High Energy QCD |
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Chair: Abhay Deshpande, State University of New York at Stony Brook Room: Kohala 4 |
Tuesday, October 7, 2014 9:00AM - 9:30AM |
1WD.00001: Study of the QGP Initial State and its Evolution to QGP Invited Speaker: Kenji Fukushima I give a summary of recent theoretical developments in our understanding of the early-time dynamics of the strongly interacting quarks and gluons right after the relativistic heavy-ion collision. The theory tells us that the soft components of the high energetic reaction can accommodate abundant gluons enough to justify a semi-classical approximation or a description in terms of coherent fields. The question is then how such coherent fields can be decohered and eventually be turned in a hydrodynamical regime. I will put my emphasis on the fact that such a theoretical question is not only challenging in high-energy QCD but also relevant for many other fields; quantum fluctuations and particle productions on a non-trivial metric associated with the expansion, classical and quantum turbulence, scaling behavior and attractors, etc. There are already promising results from numerical simulations, but at the same time, there is no established theoretical framework that can be used for the real-time investigation including full quantum fluctuations. In this talk I will briefly introduce the idea of the semi-classical gluon fields at high energy first, and then proceed into advantages and disadvantages of respective analytical and numerical approaches, and finally comment on the remaining problems and future prospects. [Preview Abstract] |
Tuesday, October 7, 2014 9:30AM - 10:00AM |
1WD.00002: Three-Dimensional Imaging and Spin - from Valence Quarks to the Sea Invited Speaker: Ralf Seidl From un-polarized Deep inelastic scattering (DIS) it is known that describing the properties of the nucleon by just three valence quarks is not sufficient for most properties. Even in the Quark model one only can describe the nucleon mass by dressing the bare quarks. The actual bare quark masses as obtained by the Higgs mechanism only make up about 1\% of the total mass of the nucleon with the rest dynamically created by the strong interaction. The study of the the strong interaction thus is the study of the 99\% of the visible mass of the universe. The best way to understand QCD is by studying the quark and gluon properties in the nucleon such as its momentum distribution, its helicity contribution as well as its three-dimensional dynamics. The valence quark helicity contributions have been well measured by semi-inclusive DIS measurements making use of the knowledge of the unpolarized distributions and fragmentation functions. Similarly first insights into the three dimensional structure have been made in semi-inclusive and exclusive DIS. Some knowledge is still missing at larger Bjorken x which is expected to be obtained from the JLAB12 upgrade and some RHIC transverse spin measurements. The non-valence quark quantities are not as well known yet. Recent RHIC measurements for the first time indicate a nonzero contribution of the gluon spin to the nucleon at intermediate x. Sea quarks at similar x will be reasonably constrained by the RHIC W program which directly accesses sea quarks and SIDIS measurements. However in order to study the total spin contribution to the nucleon lower x measurements are necessary in the future as the uncertainties due to extrapolation are still substantial and can alter the interpretation completely as it had between the first SLAC experiments and EMC. Similarly, a broad x range will be necessary to access the three-dimensional structure which allows us to more directly study the quark and gluon dynamics in the nucleon and provides some relation to the orbital angular momentum via the Ji sum rule. Consequently the first existing measurements need to be augmented by JLAB 12 at the high x range and in particular by EIC at mid to lower x with high precision. The current status of our knowledge on the quark and gluon spin contributions to the nucleon and its three-dimensional structure will be discussed. An brief outline of future measurements will be given as well. [Preview Abstract] |
Tuesday, October 7, 2014 10:00AM - 10:30AM |
1WD.00003: The Emergence of Hadrons and the Nuclear Force from Color at an EIC Invited Speaker: Will Brooks The formation of hadrons has been successfully parameterized for decades via fragmentation functions, but thus far we have a limited understanding of the non-perturbative physics that gives rise to these functions, and how this physics is connected to QCD confinement. String models and cluster models of the underlying processes have been constrained by hadron distributions measured in a variety of hard collisions, however, little insight has been gained into the femtometer-scale dynamics at play. With the advent of new particle identification technologies, new information about hadronization can now be obtained from semi-inclusive deep inelastic scattering on nuclei by studying the interactions of the struck quark with the nuclear medium, allowing femtometer-scale measurements of the fundamental processes involved to be made for the first time. The modifications of the distributions of the identified hadrons emerging from nuclei of different sizes reveal a rich variety of spatial and temporal characteristics of the hadronization process, including its dependence on spin, flavor, energy, and hadron mass and structure. Fixed-target experiments of this kind at lower energies, pioneered by the HERMES experiment at DESY and now being extended at Jefferson Lab, are laying an important foundation of understanding of the issues involved, however, the ultimate program for exploring the high-energy domain of hadronization will come from the Electron-Ion Collider (EIC). The EIC will feature a wide range of kinematics, allowing a complete investigation of the effective lifetime of the propagation of QCD color charge. The EIC detectors are planned to have excellent particle identification, crucial for studying the flavor dependence of hadron formation. A fundamental process accessed by these studies is medium-induced gluon bremsstrahlung by the propagating quarks, leading to partonic energy loss. This fundamental process, which is also at the heart of jet quenching in heavy ion collisions, can be studied in detail for light quarks and heavy quarks at the EIC through observables quantifying hadron ``attenuation'' for a variety of hadron species. Fluctuations in the gluonic field of the nucleus may be accessible through the study of the broadening of the transverse momentum of produced hadrons, which has its origin in the quark-gluon interactions in the medium. The evolution of the forming hadrons in the medium may shed new light on the dynamical origins of the forces between hadrons. In this talk, a brief review of the status of this emerging sub-field will be followed by a description of the opportunities for advancement at the EIC. [Preview Abstract] |
Tuesday, October 7, 2014 10:30AM - 11:00AM |
1WD.00004: COFFEE BREAK |
Tuesday, October 7, 2014 11:00AM - 11:30AM |
1WD.00005: TBD Invited Speaker: Sergei Syritsyn |
Tuesday, October 7, 2014 11:30AM - 12:00PM |
1WD.00006: Theory Synergies: Observable effects of quark dressing in hadron physics Invited Speaker: Craig Roberts With discovery of the Higgs boson, the Standard Model of Particle Physics became complete. Its formulation and verification are a remarkable story. However, the most important chapter is the least understood. Quantum Chromodynamics (QCD) is that part of the Standard Model which is supposed to describe all of nuclear physics and yet, almost fifty years after the discovery of quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: pions, neutrons, protons. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB), whose implications are truly extraordinary. This presentation will reveal how DCSB, not the Higgs boson, generates more than 98\% of the visible mass in the Universe, explain why confinement guarantees that condensates, those quantities that were commonly viewed as constant mass-scales that fill all spacetime, are instead wholly contained within hadrons; and elucidate a range of observable consequences of these phenomena whose measurement is the focus of a vast international experimental programme. [Preview Abstract] |
Tuesday, October 7, 2014 12:00PM - 12:30PM |
1WD.00007: Electron-Ion Collider - Plans for Realization Invited Speaker: Patrizia Rossi Understanding the emergence of nucleons and nuclei and their interactions from the properties and dynamics of quarks and gluons in Quantum Chromo-Dynamics (QCD) is a fundamental and compelling goal of nuclear science. An Electron-Ion Collider (EIC) was designated in the 2007 Nuclear Physics Long Range Plan as ``embodying the vision for reaching the next QCD frontier,'' extending the QCD science programs in the U.S. established at both the CEBAF accelerator at JLab and RHIC at BNL in dramatic and fundamentally important ways. The 2013 Report of the NSAC Subcommittee on Major Nuclear Physics Facilities for the Next Decade reaffirmed an EIC as ``absolutely central in its ability to contribute to world-leading science in the next decade.'' Two proposals for the EIC are being considered in the U.S.: one each at BNL and at Jefferson Laboratory. In this presentation we will review these proposals of the EIC, their implementation plan, and comment on the physics opportunities they present to the nuclear science communities in the next decade. [Preview Abstract] |
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