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This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on 'Gluons and quark sea at high energies' at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users' communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier. [ABSTRACT FROM AUTHOR]

In this paper we apply to the photoproduction total cross section a model we have proposed for purely hadronic processes and which is based on QCD mini-jets and soft gluon re-summation. We compare the predictions of our model with the HERA data as well as with other models. For cosmic rays, our model predicts substantially higher cross sections at TeV energies than models based on factorization, but lower than models based on mini-jets alone, without soft gluons. We discuss the origin of this difference. [ABSTRACT FROM AUTHOR]

Including the new HERA data, the γ[sup *]p total cross-section is analyzed in the gen- eralized vector dominance/color-dipole picture (GVD/CDP) that contains scaling in η = (Q² + m²[sub 0])/Λ²(W²), where Λ²(W²) is an increasing function of W². At any Q² for W² → ∞, the cross-sections for virtual and real photons become identical, σ[sub γ[sup *]p](W², Q²)/σ[sub γp](W²) → 1. The gluon density deduced from the color-dipole crosssection fulfills the leading order DGLAP relationship. Evolution à la DGLAP breaks down for η ... 0.1. [ABSTRACT FROM AUTHOR]

Results on measurements of the proton structure function from the two HERA experiments H1 and ZEUS in 1994 show that perturbative QCD (pQCD) allows to describe the observed rapid rise of with decreasing x down to Q2 = 1.5GeV2. Whereas the pQCD region exhibits a strong rise of σγ* p tot with increasing W2, the total cross-section for real photon-proton scattering σγ p tot shows only a modest rise with W2. The proton structure function F2 and the total virtual photon-proton (γ* p) cross-section σγ* p tot have been measured in inelastic neutral current scattering, e+ p → e+ X, at HERA in the previously unexplored transition region of non-perturbative to perturbative QCD at low Q2. To study this kinematic region, a small electromagnetic Beam Pipe Calorimeter (BPC) has been designed, constructed and installed in the ZEUS experiment in 1995. The accuracy of the measurement of F2 in this kinematic region relies mainly on a precise energy calibration and detector alignment. An energy calibration with a precision of 0.5% and a detector alignment of 0.5mm have been achieved. Results on a measurement of F2 and σγ p tot are obtained for 0.11 ≤ Q2≤ 0.65 GeV2 and 1.7 ċ 10−6 ≤ x ≤ 6.0 ċ 10−5, corresponding to a range in the γ* p center-of-mass energy of 104 ≤ W ≤ 251 GeV. The results on F2 and σγ p tot indicate a smooth transition between the pQCD region and the photoproduction region. A detailed phenomenological analysis as well as a QCD analysis has been carried out to investigate the limitations of a non-perturbative as well as a perturbative QCD description. [ABSTRACT FROM AUTHOR]

The article focuses on town meetings conducted by the American Physical Society over U.S. nuclear physics ventures. Topics covered include the target laboratory machines for completion by the society like the Facility for Rare Isotope Beams at Michigan State University and the modification of the electron beam at the Thomas Jefferson National Accelerator Facility, and debates among nuclear physicists during town meetings over staff and experiments done on nuclear physics laboratories.