We show that the QCD van der Waals interaction due to multiple-gluon exchange provides a new kind of attractive nuclear force capable of binding heavy quarkonia to nuclei. The parameters of the potential are estimated by identifying multigluon exchange with the Pomeron contributions to elastic mesonnucleon scattering. The gluonic potential is then used to study the properties of cc nuclear-bound states. In particular, we predict bound states of the rj c with 3 He and heavier nuclei. Production modes and rates are also discussed.PACS numbers: 21.90.+f, 12.40.-y, 21.30.+y, 25.10.-hs One of the most interesting anomalies in hadron physics is the remarkable behavior of the spin-spin correlation A NN for pp-^pp elastic scattering at 0 cm =90°: As V7 crosses 5 GeV the ratio of cross sections for protons scattering with their incident spins parallel and normal to the scattering plane and for protons scattering with their spins antiparallel changes rapidly from approximately 2:1 to 4:1. l As shown in Ref. 2, this behavior can be understood as the consequence of a strong threshold enhancement at the open-charm threshold for pp-*A c Dp at V7 = 5.08 GeV. The dominant enhancement in the pp^*pp amplitude occurs in the partial wave J=L=S = \, which matches the quantum numbers of the J-1 5-wave eight-quark system qqqqqq(cc)s = \ at threshold. Strong final-state interactions are expected at the threshold for new-flavor production, since at threshold, all the quarks in the final state have nearly zero relative velocity.In this paper we discuss the possibility of production of hidden charm below threshold in hadronic and nuclear collisions. Consider the reaction pd-•(a 7 ) 3 He where the charmonium state is produced nearly at rest. At the threshold for charm production, the incident nuclei will be nearly stopped (in the center-of-mass frame) and will fuse into a compound nucleus (the 3 He) because of the strong attractive nuclear force. The charmonium state will be attracted to the nucleus by the QCD gluonic van der Waals force. One thus expects strong final-state interactions near threshold. In fact, we shall argue that the cc system will bind to the 3 He nucleus. It is thus likely that a new type of exotic nuclear bound state will be formed: charmonium bound to nuclear matter. Such a state should be observable at a distinct pd energy, spread by the width of the charmonium state, and it will decay to unique signatures such as pd-*' 3 He//. The binding energy in the nucleus gives a measure of the charmonium's interactions with ordinary hadrons and nuclei; its decays will measure hadron-nucleus interactions and test color transparency starting from a unique initial-state condition.In quantum chromodynamics, a heavy-quarkonium QQ state such as the t] c interacts with a nucleon or nucleus through multiple gluon exchange. This is the QCD analog of the attractive QED van der Waals potential. Unlike QED, the potential cannot have an inverse power law at large distances because of the absence of zeromass gluonium states. Since the (QQ...

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We review the present theoretical and empirical knowledge for α s , the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of α s (Q 2 ) on momentum transfer Q encodes the underlying dynamics of hadron physics -from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on α s (Q 2 ) at high Q 2 , as predicted by perturbative QCD, and its analytic behavior at small Q 2 , based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain.In the second, more technical, part of the review, we discuss the behavior of α s (Q 2 ) in the high momentum transfer domain of QCD. We review how α s is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior α s (Q 2 ) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale Λ and hadron masses. One can also identify a specific scale Q 0 which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including lattice QCD, the Schwinger-Dyson equations and the GribovZwanziger analysis. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of α s (Q 2 ) in order to bring better unity to the subject.2

The light-front holographic mapping of classical gravity in anti-de Sitter space, modified by a positive-sign dilaton background, leads to a nonperturbative effective coupling α AdS s (Q 2 ). It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale ∼ 1 GeV. The resulting β function appears to capture the essential characteristics of the full β function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on α AdS s (Q 2 ).

The structure of generalized parton distributions is determined from light-front holographic QCD up to a universal reparametrization function w(x) which incorporates Regge behavior at small x and inclusive counting rules at x→1. A simple ansatz for w(x) that fulfills these physics constraints with a single-parameter results in precise descriptions of both the nucleon and the pion quark distribution functions in comparison with global fits. The analytic structure of the amplitudes leads to a connection with the Veneziano model and hence to a nontrivial connection with Regge theory and the hadron spectrum.