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 Washington, D.C. : United States. Dept. of Energy. Office of Science ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2011
 Description
 Book — 1 online resource.
 Summary

Progresses towards the calculation and the understanding of NLO/NLL contributions to Deep Inelastic Scattering at low x with gluon saturation are being reviewed.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2007
 Description
 Book — 1 online resource.
 Summary

Initialstate and finalstate interactions which are conventionally neglected in the parton model, have a profound effect in QCD hardscattering reactions. The effects, which arise from gluon exchange between the active and spectator quarks, cause leadingtwist singlespin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and the breakdown of the LamTung relation in DrellYan reactions. Diffractive deep inelastic scattering also leads to nuclear shadowing and nonuniversal antishadowing of nuclear structure functions through multiple scattering reactions in the nuclear target. Factorizationbreaking effects are particularly important for hard hadron interactions since both initialstate and finalstate interactions appear. Related factorization breaking effects can also appear in exclusive electroproduction reactions and in deeply virtual Compton scattering. None of the effects of initialstate and finalstate interactions are incorporated in the lightfront wavefunctions of the target hadron computed in isolation.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2005
 Description
 Book — 1 online resource (4 pages) : digital, PDF file.
 Summary

The shadowing and antishadowing of nuclear structure functions in the GribovGlauber picture is due to the destructive and constructive interference of amplitudes arising from the multiplescattering of quarks in the nucleus, respectively. The diffractive contributions to deep inelastic scattering includes Pomeron and Odderon contributions from multigluon exchange as well as Reggeon quarkexchange contributions. The coherence of multistep nuclear processes leads to shadowing and antishadowing of the electromagnetic nuclear structure functions in agreement with measurements. This picture also leads to substantially different antishadowing for charged and neutral current reactions, thus affecting the extraction of the weakmixing angle Θ{sub W}. The fact that Reggeon couplings depend on the quantum numbers of the struck quark implies nonuniversality of nuclear antishadowing for charged and neutral currents as well as a dependence of antishadowing on the polarization of the beam and target. The implications of hidden color degrees of freedom in the nuclear wavefunction is also briefly discussed.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004
 Description
 Book — 1 online resource.
 Summary

Multiple scattering, induced radiative energy loss and modified fragmentation functions of a heavy quark in nuclear matter are studied within the framework of generalized factorization in perturbative QCD. Modified heavy quark fragmentation functions and energy loss are derived in detail with illustration of the mass dependencies of the LandauPomeranchukMigdal interference effects and heavy quark energy loss. Due to the quark mass dependence of the gluon formation time, the nuclear size dependencies of nuclear modification of the heavy quark fragmentation function and heavy quark energy loss are found to change from a linear to a quadratic form when the initial energy and momentum scale are increased relative to the quark mass. The radiative energy loss of the heavy quark is also significantly suppressed due to limited cone of gluon radiation imposed by the mass. Medium modification of the heavy quark fragmentation functions is found to be limited to the large z region due to the form of heavy quark fragmentation functions in vacuum.
 Online
 Washington, D.C. : United States. Dept. of Energy. Office of Science ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004
 Description
 Book
 Summary

It is usually assumedfollowing the parton modelthat the leadingtwist structure functions measured in deep inelastic leptonproton scattering are simply the probability distributions for finding quarks and gluons in the target nucleon. In fact, gluon exchange between the outgoing quarks and the target spectators effects the leadingtwist structure functions in a profound way, leading to diffractive leptoproduction processes, shadowing and antishadowing of nuclear structure functions, and target spin asymmetries, physics not incorporated in the lightfront wavefunctions of the target computed in isolation. In particular, finalstate interactions from gluon exchange lead to singlespin asymmetries in semiinclusive deep inelastic leptonproton scattering which are not powerlaw suppressed in the Bjorken limit. The shadowing and antishadowing of nuclear structure functions in the GribovGlauber picture is due respectively to the destructive and constructive interference of amplitudes arising from the multiplescattering of quarks in the nucleus. The effective quarknucleon scattering amplitude includes Pomeron and Odderon contributions from multigluon exchange as well as Reggeon quarkexchange contributions. Part of the anomalous NuTeV result for sin² θ{sub W} could be due to the nonuniversality of nuclear antishadowing for charged and neutral currents. Detailed measurements of the nuclear dependence of individual quark structure functions are thus needed to establish the distinctive phenomenology of shadowing and antishadowing and to make the NuTeV results definitive. I also discuss diffraction dissociation as a tool for resolving hadron substructure Fock state by Fock state and for producing leading heavy quark systems.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004
 Description
 Book — 1 online resource (vp.) : digital, PDF file.
 Summary

The shadowing and antishadowing of nuclear structure functions in the GribovGlauber picture is due respectively to the destructive and constructive interference of amplitudes arising from the multiplescattering of quarks in the nucleus. The effective quarknucleon scattering amplitude includes Pomeron and Odderon contributions from multigluon exchange as well as Reggeon quarkexchange contributions. The authors show that the coherence of these multiscattering nuclear processes leads to shadowing and antishadowing of the electromagnetic nuclear structure functions in agreement with measurements. This picture leads to substantially different antishadowing for charged and neutral current reactions, thus affecting the extraction of the weakmixing angle θ{sub w}. They find that part of the anomalous NuTeV result for θ{sub w} could be due to the nonuniversality of nuclear antishadowing for charged and neutral currents. Detailed measurements of the nuclear dependence of individual quark structure functions are thus needed to establish the distinctive phenomenology of shadowing and antishadowing and to make the NuTeV results definitive.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003
 Description
 Book — 1 online resource (4 pages ) : digital, PDF file.
 Summary

Multiple scattering, modified fragmentation functions and radiative energy loss of a heavy quark propagating in a nuclear medium are investigated in perturbative QCD. Because of the quark mass dependence of the gluon formation time, the medium size dependence of heavy quark energy loss is found to change from a linear to a quadratic form when the initial energy and momentum scale are increased relative to the quark mass. The radiative energy loss is also significantly suppressed relative to a light quark due to the suppression of collinear gluon emission by a heavy quark.
 Online
 Washington, D.C. : United States. Dept. of Energy ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2002
 Description
 Book — 1 online resource (8 p. ) : digital, PDF file.
 Summary

In the target rest frame and at high energies, DrellYan (DY) dilepton production looks like bremsstrahlung of massive photons, rather than parton annihilation. The projectile quark is decomposed into a series of Fock states. Configurations with fixed transverse separations in impact parameter space are interaction eigenstates for p p scattering. The DY cross section can then be expressed in terms of the same color dipole cross section as DIS. We compare calculations in this dipole approach with E772 data and with nexttoleading order parton model calculations. This approach is especially suitable to describe nuclear effects, since it allows one to apply Glauber multiple scattering theory. We go beyond the Glauber eikonal approximation by taking into account transitions between states, which would be eigenstates for a proton target. We calculate nuclear shadowing at large Feynmanx{sub F} for DY in protonnucleus collisions and compare to E772 data. Nuclear effects on the transverse momentum distribution are also investigated.
 Online
9. THE COLOR DIPOLE APPROACH TO THE DRELLYAN PROCESS IN PA COLLISIONS [electronic resource]. [2001]
 Washington, D.C. : United States. Dept. of Energy ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2001
 Description
 Book — 1 online resource (191 Kilobytes pages ) : digital, PDF file.
 Summary

In the target rest frame and at high energies, DrellYan (DY) dilepton production looks like bremsstrahlung of massive photons, rather than parton annihilation. The projectile quark is decomposed into a series of Fock states. Configurations with fixed transverse separations are interaction eigenstates for pp scattering. The DY cross section can then be expressed in terms of the same color dipole cross section as DIS. This approach is especially suitable to describe nuclear effects, since it allows to apply Glauber multiple scattering theory. We go beyond the Glauber eikonal approximation by taking into account transitions between interaction eigenstates. We calculate nuclear shadowing at large Feynmanx{sub f} for DY in protonnucleus collisions, compare to existing data from E772 and make predictions for RHIC. Nuclear effects on the transverse momentum distribution are also investigated.
 Online
 Washington, D.C. : United States. Dept. of Energy. ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2001
 Description
 Book — 1 online resource (37 pages ) : digital, PDF file.
 Summary

Multiple parton scattering and induced parton energy loss are studied in deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering of a highly offshell quark and the induced parton energy loss is expressed in terms of the modification to the quark fragmentation functions. The authors derive such modified quark fragmentation functions and their QCD evolution equations in DIS using the generalized factorization of higher twist parton distributions. They consider doublehard and hardsoft parton scattering as well as their interferences in the same framework. The final result, which depends on both the diagonal and offdiagonal twistfour parton distributions in nuclei, demonstrates clearly the LandauPomeranchukMigdal interference features and predicts a unique nuclear modification of the quark fragmentation functions.
 Online
 Los Alamos, N.M. : Los Alamos National Laboratory ; Oak Ridge, Tenn. : distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 1984
 Description
 Book — 1 online resource (Pages: 9 ) : digital, PDF file.
 Summary

The K/sup +/nucleus system is reviewed and comparison with data is made. The principal conclusions are that the theoretical uncertainties in relating the K/sup +/nucleus interaction to the K/sup +/nucleon interaction are very small and hence the positive kaon makes an excellent probe of the nucleus. It is suggested that this particle may be more sensitive to nonnucleonic degrees of freedom (especially quarks) than classical probes.
 Online