E. Naftali

A modified Balitsky–Kovchegov equation

Abstract We propose a modified version of the Balitsky–Kovchegov (BK) evolution equation, which includes the main NLO corrections. We use the result that the main NLO corrections to the BFKL kernel are the LO DGLAP corrections. We present a numerical solution of the modified non-linear equation, and compare with the solution of the unmodified BK equation. We show that the saturation momentum has a sharp increase in the LHC energy range. Our numerical solution indicates that the influence of the preasymptotic corrections, related to the full anomalous dimensions of the DGLAP equation, are rather large. These corrections moderate the energy behavior of the amplitude, as well as the value of the saturation scale. All our calculations are made with a fixed value of α S .

Momentum transfer dependence of the differential cross section for J/ψ production

We discuss the |t| dependence of J/ψ production in the region of 0<|t|≲M2ψ. The forward slope of the elastic differential cross section is calculated assuming a dipole-type dependence for the gluon ladder-proton form factor. The |t| dependence of dσ/dt is obtained using DGLAP evolution both for the elastic channel at low |t| and for the inelastic channel at large values of |t|, up to |t|≃M2ψ. Results are presented and compared with the relevant experimental data.

A unitarized QCD model for deep inelastic ep scattering

Recent experimental results emanating from HERA support the supposition that we are encountering phenomena associated with high-density partons. Evidence for this is: (a) the large value of the gluon structure function; (b) the asymptotic predictions of high-density quantum chromodynamics seem to be realized. We propose a model based on the Glauber-Mueller eikonal formalism, which incorporates screening corrections. Numerical estimates calculated using this model are consistent with the experimental data, and in addition provide a natural explanation for the size of the deviation from the standard DGLAP result. To obtain a complete picture we review some of our previous results pertaining to the logarithmic slope of F2, and the inclusive production of J/Ψ. Alternative approaches which deal with saturation phenomena are discussed, and new experiments are suggested.These notes are a summary of our efforts to answer the question in the title. Our answer is in the affirmative as: (i) HERA data indicate a large value of the gluon structure function; (ii) no contradictions with the asymptotic predictions of high density QCD have been observed; and (iii) the numerical estimates of our model give a natural description of the size of deviation from the routine DGLAP explanation. We discuss the alternative approaches and possible new experiments.

Has HERA reached a new QCD regime

Recent experimental results emanating from HERA support the supposition that we are encountering phenomena associated with high-density partons. Evidence for this is: (a) the large value of the gluon structure function; (b) the asymptotic predictions of high-density quantum chromodynamics seem to be realized. We propose a model based on the Glauber-Mueller eikonal formalism, which incorporates screening corrections. Numerical estimates calculated using this model are consistent with the experimental data, and in addition provide a natural explanation for the size of the deviation from the standard DGLAP result. To obtain a complete picture we review some of our previous results pertaining to the logarithmic slope of F2, and the inclusive production of J/Ψ. Alternative approaches which deal with saturation phenomena are discussed, and new experiments are suggested.These notes are a summary of our efforts to answer the question in the title. Our answer is in the affirmative as: (i) HERA data indicate a large value of the gluon structure function; (ii) no contradictions with the asymptotic predictions of high density QCD have been observed; and (iii) the numerical estimates of our model give a natural description of the size of deviation from the routine DGLAP explanation. We discuss the alternative approaches and possible new experiments.

Screening corrections in photo and DIS production of J/Ψ

Abstract Photo and DIS production of J/ Ψ are investigated and compared with calculations based on pQCD in the LLA approximation without and with screening corrections. The calculation includes corrections induced by the real part of the production amplitude, the skewed (off diagonal) gluon distribution function and the relativistic Fermi motion within the charmonium system. Our pQCD results are also compared with the predictions obtained from a Regge type two-pomeron model. Our results show that the screened pQCD model gives a better reproduction of the data than the nonscreened model. However, the available data does not enable us to exclude any of the three models we have examined. The predictions of these models, when extrapolated to both low and very high energies may provide a more effective discrimination between the different parameterizations.

The components of the \(\gamma^* \gamma^*\) cross section

Abstract. We extend our previous treatment of the

The scattering of photons on proton and photon targets

\gamma^{*}

Towards a new global QCD analysis: solution to the Balitsky–Kovchegov nonlinear equation at arbitrary impact parameter

p cross section based on Gribovs hypothesis to the case of photon–photon scattering. With the aid of two parameters, determined from the experimental data, we separate the interactions into two categories corresponding to short (“soft”) and long (“hard”) distance processes. The photon–photon cross section thus receives contributions from three sectors, soft–soft, hard–hard and hard–soft. The additive quark model is used to describe the soft–soft sector, pQCD the hard–hard sector, while the hard–soft sector is determined by relating it to the

The effect of screening on the x and Q2 behaviour of F2 slopes

\gamma^{*}p

Scaling violations in the Q2 logarithmic derivative of F2

system. We calculate and display the behaviour of the total photon–photon cross section and its various components and polarizations for different values of energy and virtuality of the two photons, and discuss the significance of our results.