On the intrinsic charm and the recombination mechanisms in charm hadron production

Proceedings of 4th International Workshop High-pT Physics at LHC 09 — PoS(High-pT Physics09)

2010

The presence of direct higher-twist processes, where a proton is produced directly in the hard subprocess, can explain the "baryon anomaly" -the large proton-to-pion ratio seen at RHIC in high centrality heavy ion collisions. Direct hadronic processes can also account for the deviation from leading-twist pQCD scaling at fixedRescattering interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hardscattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam-Tung relation in DrellYan reactions, nuclear shadowing -all leading-twist dynamics not incorporated in the light-front wavefunctions of the target computed in isolation. Antishadowing is shown to be quark flavor specific and thus different in charged and neutral deep inelastic lepton-nucleus scattering. Other aspects of quantum effects in heavy ion collisions include hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and the important consequences of color-octet intrinsic heavy quark distributions in the proton for particle and Higgs production at high x F . The "ridge" -the same-side long-range rapidity correlation observed at RHIC in high centrality heavy ion collisions is suggested as due to the imprint of semihard DGLAP gluon radiation from initial-state partons which have transverse momenta biased toward the trigger. I also discuss how the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories allows one to compute the analytic form of frame-independent light-front wavefunctions of mesons and baryons and to compute quark and gluon hadronization at the amplitude level. Finally, the BLM method for determining the renormalization scale in pQCD calculations is reviewed.

Section: Novel Intrinsic Heavy Quark Phenomenasupporting

confidence: 90%

Novel Aspects of QCD in High Transverse Momentum Production Processes at RHIC and the LHC

Proceedings of 4th International Workshop High-pT Physics at LHC 09 — PoS(High-pT Physics09)

2010

“…The diffractive dissociation of the intrinsic charm Fock state leads to leading charm hadron production and fast charmonium production in agreement with measurements [45]. Intrinsic charm can also explain the J/ψ → ρπ puzzle [39], and it affects the extraction of suppressed CKM matrix elements in B decays [40].…”

Section: Diffractive Dissociation and Intrinsic Heavy Quark Productionsupporting

confidence: 82%

Light-Front QCD

2004

In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, including light-front statistical physics. Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. Given the LFWFs, one can compute form factors, heavy hadron decay amplitudes, hadron distribution amplitudes, and the generalized parton distributions underlying deeply virtual Compton scattering. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffractive dissociation, and hidden-color components of nuclear wavefunctions. A new test of hidden color in deuteron photodisintegration is proposed. The origin of leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing is also discussed; these phenomena cannot be described by lightfront wavefunctions of the target computed in isolation. Part of the anomalous NuTeV results for the weak mixing angle θ W could be due to the non-universality of nuclear antishadowing for charged and neutral currents.2

“…Intrinsic charm thus predicts that the charm structure function has support at large x bj in excess of DGLAP extrapolations [83]; this is in agreement with the EMC measurements [86]. It predicts leading charm hadron production and fast charmonium production in agreement with measurements [87]. In fact even double J/ψ ′ s are produced at large x F , consistent with the dissociation and coalescence of double intrinsic Fock states of the projectile LFWF [88].…”

Section: Other Qcd Phenomenology Related To Lightfront Wavefunctionssupporting

confidence: 77%

New Results in Light-Front Phenomenology

2004

The light-front quantization of gauge theories in light-cone gauge provides a frameindependent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitarity, and a trivial vacuum. In this talk I review the theoretical methods and constraints which can be used to determine these central elements of QCD phenomenology. The freedom to choose the light-like quantization four-vector provides an explicitly covariant formulation of light-front quantization and can be used to determine the analytic structure of light-front wave functions and define a kinematical definition of angular momentum. The AdS/CFT correspondence of large N C supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in 4-dimensional space-time has interesting implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for exclusive processes. String/gauge duality also predicts the QCD power-law behavior of light-front Fock-state hadronic wavefunctions with arbitrary orbital angular momentum at high momentum transfer. The form of these nearconformal wavefunctions can be used as an initial ansatz for a variational treatment of the light-front QCD Hamiltonian. The light-front Fock-state wavefunctions encode the bound state properties of hadrons in terms of their quark and gluon degrees of freedom at the amplitude level. The nonperturbative Fock state wavefunctions contain intrinsic gluons, and sea quarks at any scale Q with asymmetries such as s(x) =s(x),ū(x) =d(x). Intrinsic charm and bottom quarks appear at large x in the light-front wavefunctions since this minimizes the invariant mass and off-shellness of the higher Fock state. In the case of nuclei, the Fock state expansion contains "hidden color" states which cannot be classified in terms of nucleonic degrees of freedom. I also briefly review recent analyses which shows that some leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing cannot be computed from the LFWFs of hadrons in isolation.2