arXiv subjects

Wei Zhu

Publications and source records attributed to Wei Zhu.

At least 379 records · Page 21Linked to original sources

arXiv2009

Prediction for unintegrated parton distributions

Unintegrated parton distributions in the proton and nucleus are predicted by a modified DGLAP equation incorporating the shadowing corrections, which include exact energy-momentum conservation in each splitting and fusion vertices. We find that the nuclear shadowing effects are obvious, although they are far from the saturation limit. On the other hand, we point out that the suppression of the unintegrated gluon distribution toward lower $k_t^2$ may arise from the valence-like input rather than the saturation effects.

hep-ph↗

arXiv2008

Can a chaotic solution in the QCD evolution equation restrain high-energy collider physics?

We indicate that the random aperiodic oscillation of the gluon distributions in a modified Balisky--Fadin--Kuraev--Lipatov (BFKL) equation has positive Lyapunov exponents. This first example of chaos in QCD evolution equations, raises the sudden disappearance of the gluon distributions at a critical small value of the Bjorken variable $x$ and may stop the increase of the new particle events in an ultra high energy hadron collider.

hep-ph↗

arXiv2008

Can a chaos term in the QCD evolution equation restrain high-energy collider physics?

We indicate that the random aperiodic oscillation of the gluon distributions in a modified BFKL equation has the positive Lyapunov exponents. This first example of chaos in QCD evolution equations, raises the sudden disappearance of the gluon distributions at a critical small value of the Bjorken variable $x$ and may stop the increase of the new particle events in a ultra high energy hadron collider.

hep-ph↗

arXiv2008

Nuclear Shadowing and Antishadowing in a Unitarized BFKL Equation

The nuclear shadowing and antishadowing effects are explained by a unitarized BFKL equation. The $Q^2$- and $x$-variations of the nuclear parton distributions are detailed based on the level of the unintegrated gluon distribution. In particular, the asymptotical behavior of the unintegrated gluon distribution near the saturation limit in nuclear targets is studied. Our results in the nuclear targets are insensitive to the input distributions if the parameters are fixed by the data of a free proton.

hep-ph↗

arXiv2007

Regularity of Dirichlet nearly minimizing multiple-valued functions

In this paper, we extend the related notions of Dirichlet quasiminimizer, $ω-$minimizer and almost minimizer to the framework of multiple-valued functions in the sense of Almgren and prove Holder regularity results. We also give examples of those minimizers with various branch sets.

math.AP↗

arXiv2006

Antishadowing effects in the unitarized BFKL equation

A unitarized BFKL equation incorporating shadowing and antishadowing corrections of the gluon recombination is proposed. This equation reduces to the Balitsky-Kovchegov evolution equation near the saturation limit. We find that the antishadowing effects have a sizeable influence on the gluon distribution function in the preasymptotic regime.

hep-ph↗

arXiv2006

A regularity theory for multiple-valued Dirichlet minimizing maps

This paper discusses the regularity of multiple-valued Dirichlet minimizing maps into the sphere. It shows that even at branched point, as long as the normalized energy is small enough, we have the energy decay estimate. Combined with the previous work by Chun-Chi Lin, we get our first estimate that m-2 dimensional Hausdorff measure of singular set is zero. Furthermore, by looking at the tangent map and using dimension reduction argument, we show that the singular set is at least of codimension 3.

math.OC↗

arXiv2006

Analysis on Metric Space Q

In this paper, we show that the metric space Q is a positively-curved space (PC-space) in the sense of Alexandrov. We also discuss some issues like metric tangent cone and exponential map of Q. Then we give a stratification of this metric space according to the signature of points in Q. Some properties of this stratification are shown. The second part of this paper is devoted to some basic analysis on the space Q, like the tensor sum and L-p space, which can be of independent interest. In the end, we give another definition of derivative for multiple-valued functions, which is equivalent to the one used by Almgren. An interesting theorem about regular selection of multiple-valued functions which preserves the differentiability concludes this paper.

math.GN↗

arXiv2006

A Theorem on Frequency Function for Multiple-Valued Dirichlet Minimizing Functions

This paper discusses the frequency function of multiple-valued Dirichlet minimizing functions in the special case when the domain and range are both two dimensional. It shows that the frequency function must be of value k/2 for some nonnegative integer k. Futhermore, by looking at the blowing-up functions, we characterize the local behavior of the original Dirichlet minimizing function.

math.AP↗

arXiv2006

An Energy Reducing Flow for Multiple-Valued Functions

By the method of discrete Morse flows, we construct an energy reducing multiple-valued function flow. The flow we get is Holder continuous with respect to the L-2 norm. We also give another way of constructing flows in some special cases, where the flow we get behaves like ordinary heat flow.

math.AP↗

arXiv2006

A unity of QCD evolution dynamics at small $x$ region

The DGLAP, BFKL, modified DGLAP and modified BFKL equations are constructed in a unified partonic framework. The antishadowing effect in the recombination process is emphasized, which leads to two different small $x$ behaviors of gluon distribution. In the meantime, the BFKL equation and modified DGLAP equation are viewed as the corrections of the initial gluon correlations to the evolution dynamics at twist-2 and twist-4, respectively. A partonic explanation of Regge theory for the BFKL dynamics and the relation of the BFKL dynamics with the helicity configuration of the initial gluons are presented.

hep-ph↗

arXiv2005

A geometrizing higher twist effect on nuclear target

The higher twist effects in deep inelastic scattering on the nuclear target are studied using time ordered perturbation theory. We showed that the collinear rescattering of the outgoing quark on the extra nucleons via the contacting gluon-pair is dominant in nuclear size-dependent effects. The Qiu-Vitev resummation is proved by using the geometric properties of the higher twist amplitudes. The leading contributions of nuclear-enhanced effect to the DGLAP evolution equation are resummed in the same framework.

hep-ph↗

arXiv2003

Contributions of gluon recombination to saturation phenomena

Parton distributions in the small $x$ region are numerically predicted by using a modified DGLAP equation with the GRV-like input distributions. We find that gluon recombination at twist-4 level obviously suppresses the rapid growth of parton densities with $x$ decrease. We show that before the saturation scale $Q^2_s$ is reached, saturation and partial saturation appear in the small $x$ behavior of parton distributions in nucleus and free proton, respectively. The antishadowing contributions to the saturation phenomena are also discussed.

hep-ph↗

arXiv2002

Saturation and Wilson Line Distributions

We introduce a Wilson line distribution function bar{W}_tau(v) to study gluon saturation at small Feynman x_F, or large tau=ln(1/x_F). This new distribution can be obtained from the distribution W_tau(alpha) of the Color Glass Condensate model and the JIMWLK renormalization group equation. bar{W}_tau(v) is physically more relevant, and mathematically simpler to deal with because of unitarity of the Wilson line v. A JIMWLK equation is derived for bar{W}_tau(v); its properties are studied. These properties are used to complete Mueller's derivation of the JIMWLK equation, though for bar{W}_tau(v) and not W_tau(alpha). They are used to derive a generalized Balitsky-Kovchegov equation for higher multipole amplitudes. They are also used to compute the unintegrated gluon distribution at x_F=0, yielding a completely flat spectrum in transverse momentum squared k^2, with a known height. This is similar but not identical to the mean field result at small k^2.

hep-ph↗

arXiv2001

Nuclear enhanced power corrections to DIS structure functions

We calculate nuclear enhanced power corrections to structure functions measured in deeply inelastic lepton-nucleus scattering in Quantum Chromodynamics (QCD). We find that the nuclear medium enhanced power corrections at order of $O(α_s/Q^2)$ enhance the longitudinal structure function $F_L$, and suppress the transverse structure function $F_1$. We demonstrate that strong nuclear effects in $σ_A/σ_D$ and $R_A/R_D$, recently observed by HERMES Collaboration, can be explained in terms of the nuclear enhanced power corrections.

hep-ph↗

arXiv2000

$x_F$ Dependence of Drell-Yan Transverse Moemtum Broadening

We analyze $x_F$ dependence of Drell-Yan transverse momentum broadening in hadron-nucleus collisions. In terms of generalized factorization theorem, we show that the $x_F$ dependence of transverse momentum broadening, $ Δ< q_T^2 > (x_F) $, can be calculated in perturbative QCD. We demonstrate that $Δ< q_T^2 > (x_F)$ is a good observable for studying the effects of initial-state multiple scattering and extracting quark-gluon correlation functions.

hep-ph↗

arXiv1999

Space-time properties of the higher twist amplitudes

A consistent and intuitive description of the twist-4 corrections to the hadron structure functions is presented in a QCD-improved parton model using time-ordered perturbative theory, where the collinear singularities are naturally eliminated. We identify the special propagators with the backward propagators of partons in time order.

hep-ph↗

arXiv1998

A new approach to parton recombination in a QCD evolution equation

Parton recombination is reconsidered in perturbation theory without using the AGK cutting rules in the leading order of the recombination. We use time-ordered perturbation theory to sum the cut diagrams, which are neglected in the GLR evolution equation. We present a set of new evolution equations including parton recombination.

hep-ph↗