43 research outputs found
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Heavy Quarkonium Physics
This report is the result of the collaboration and research effort of the
Quarkonium Working Group over the last three years. It provides a comprehensive
overview of the state of the art in heavy-quarkonium theory and experiment,
covering quarkonium spectroscopy, decay, and production, the determination of
QCD parameters from quarkonium observables, quarkonia in media, and the effects
on quarkonia of physics beyond the Standard Model. An introduction to common
theoretical and experimental tools is included. Future opportunities for
research in quarkonium physics are also discussed.Comment: xviii + 487 pages, 260 figures. The full text is also available at
the Quarkonium Working Group web page: http://www.qwg.to.infn.i
Leading twist nuclear shadowing phenomena in hard processes with nuclei
We present and discuss the theory and phenomenology of the leading twist
theory of nuclear shadowing which is based on the combination of the
generalization of the Gribov-Glauber theory, QCD factorization theorems, and
the HERA QCD analysis of diffraction in lepton-proton deep inelastic scattering
(DIS). We apply this technique for the analysis of a wide range of hard
processes with nuclei---inclusive DIS on deuterons, medium-range and heavy
nuclei, coherent and incoherent diffractive DIS with nuclei, and hard
diffraction in proton-nucleus scattering---and make predictions for the effect
of nuclear shadowing in the corresponding sea quark and gluon parton
distributions. We also analyze the role of the leading twist nuclear shadowing
in generalized parton distributions in nuclei and in certain characteristics of
final states in nuclear DIS. We discuss the limits of applicability of the
leading twist approximation for small x scattering off nuclei and the onset of
the black disk regime and methods of detecting it. It will be possible to check
many of our predictions in the near future in the studies of the
ultraperipheral collisions at the Large Hadron Collider (LHC). Further checks
will be possible in pA collisions at the LHC and forward hadron production at
the Relativistic Heavy Ion Collider (RHIC). Detailed tests will be possible at
an Electron-Ion Collider (EIC) in the USA and at the Large Hadron-Electron
Collider (LHeC) at CERN.Comment: 253 pages, 103 figures, 7 tables. The final published versio
Precision Studies of QCD in the Low Energy Domain of the EIC
The manuscript focuses on the high impact science of the EIC with objective
to identify a portion of the science program for QCD precision studies that
requires or greatly benefits from high luminosity and low center-of-mass
energies. The science topics include (1) Generalized Parton Distributions, 3D
imagining and mechanical properties of the nucleon (2) mass and spin of the
nucleon (3) Momentum dependence of the nucleon in semi-inclusive deep inelastic
scattering (4) Exotic meson spectroscopy (5) Science highlights of nuclei (6)
Precision studies of Lattice QCD in the EIC era (7) Science of far-forward
particle detection (8) Radiative effects and corrections (9) Artificial
Intelligence (10) EIC interaction regions for high impact science program with
discovery potential. This paper documents the scientific basis for supporting
such a program and helps to define the path toward the realization of the
second EIC interaction region.Comment: 103 pages,47 figure