Search

We consider the experimental data on the production of strange Lambdas, and multistrange baryons (Xi, Omega), and antibaryons, on nuclear targets, at the energy region from SPS up to LHC, in the framework of the Quark-Gluon String Model. One remarkable result of this analysis is the significant dependence on the centrality of the collision of the experimental ratios bar(Xi)+/bar(Lambda) and bar(Omega)+/bar(Lambda) ratios in heavy-ion collisions, at SPS energies., Comment: 4 pages, 2 figures, 1 table Contribution to the 51th International Symposium on Multiparticle Dynamics (ISMD2022), Pitlochry, Scotland, UK, July 31st-August 5th (2022)

We consider the experimental data on yields of protons, strange $\Lambda^{\prime}$s, and multistrange baryons ($\Xi$, $\Omega$), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the Quark-Gluon String Model calculations. In the case of heavy nucleus collisions, the experimental dependence of the $\overline{\Xi}^+/\overline{\Lambda}$, and, in particular, of the $\overline{\Omega}^+/\overline{\Lambda}$ ratios, on the centrality of the collision, shows a manifest violation of quark combinatorial rules., Comment: 18 pages, 7 figures, 4 tables. Accepted for publication in Physical Review D

We expose the current experimental and theoretical situation of the interesting case of the production of phi mesons in up to very high energy collisions of hadrons on both nucleon and nuclear targets, and we present a quantitavely good theoretical description of the corresponding experimental data, based on the formalism of the well established Quark-Gluon String Model, that has proved to be valid for a wide energy range. All the available experimental data for phi-meson production in hadron-nucleon collisions on the spectra of secondary phi, and on the ratios of phi/pi(-) and phi/K(-) production cross sections, as well the corresponding ones for phi-meson production on nuclear targets, are considered. In particular, it is seen that the production of phi-mesons on nuclear targets presents unusually small shadow corrections for the inclusive density in the central rapidity region., Comment: 29 pages, 14 figures, 4 tables

We consider the experimental data on neutral Kstar-meson production on nucleon and nuclear targets. The Quark-Gluon String Model quantitatively describes the inclusive density in the midrapidity region, as well as the initial energy and A dependences of the produced Kstar-mesons., Comment: 19 pages, 8 figures, and 4 tables. arXiv admin note: text overlap with arXiv:1610.06039

The inclusive spectra of secondaries produced in soft (minimum-bias) p+Pb collisions at LHC energy are calculated in the frame of the Quark-Gluon String Model, by including the inelastic screening corrections (percolation effects). These effects are expected to be quite large at the very high energies, and they should drive down the spectra in the midrapidity region more than 2 times, at sqrt(sNN)=5 TeV., Comment: Contribution to the Proceedings of the Low-x Meeting 2017, ed by C. Royon et al., Bisceglie, near Bari (Italy), June 13th-18th, 2017 (6 pages and 1 table)

We consider the experimental data on phi-meson production on nuclear targets, and we find that they present unusually small shadow corrections for the inclusive density in the midrapidity region. We also give a quantitatively consistent description of both the initial energy dependence and the A-dependence of the produced phi-mesons, obtained in the frame of the Quark-Gluon String Model., Comment: 13 pages, 6 figures, and 3 tables. arXiv admin note: text overlap with arXiv:1604.01918

We calculate the inclusive spectra of secondaries produced in soft (minimum bias) p+Pb collisions in the framework of Quark-Gluon String Model at LHC energy, by taking into account the inelastic screening corrections (percolation effects). The role of these effects is expected to be very large at the very high energies, and they should decrease the spectra more than 2 times in the midrapidity region at sqrt(s)_(NN) = 5 TeV. The experimental data confirm such a picture, which means that the nuclear screening effects are connected with the Pomeron interaction rather than with the interactions of the produced secondary particles in the final state., Comment: 11 pages, 2 figures, and 2 tables. arXiv admin note: substantial text overlap with arXiv:1207.6900

The experimental data on p, Lambda, Xi-, Omega-, baryons and the corresponding antibaryons spectra obtained by different collaborations are compared with the results of the calculations performed into the frame of the Quark-Gluon String Model. The contribution of String Junction diffusion and the inelastic screening corrections are accounted for in the theoretical calculations. The predictions of the Quark-Gluon String Model both for pp and pA collisions are extended up to the LHC energies., Comment: 23 pages, 12 figures, and 3 tables. arXiv admin note: substantial text overlap with arXiv:1305.0388; text overlap with arXiv:1307.3442 by other authors

In this paper we present the description of the production of strange and mulistrange baryons in a wide energy region, from CERN SpS up to LHC, in the framework of the Quark-Gluon String model., Comment: Proceedings of Initial Stages 2014 Conference (6 pages, 2 figures, and 2 tables)

We consider the photoproduction of secondary mesons in the framework of the Quark-Gluon String model. At relatively low energies, not only cylindrical, but also planar diagrams have to be accounted for. To estimate the significant contribution of planar diagrams in gamma-p collisions at rather low energies, we have used the expression obtained from the corresponding phenomenological expression for pi-p collisions. The results obtained by the model are compared to the existing SLAC experimental data. The model predictions for light meson production at HERMES energies are also presented., Comment: 13 pages and 8 figures

We consider the experimental data on var(phi)-meson production in hadron-nucleon collisions for a wide energy region. The Quark-Gluon String Model quantitatively describes the spectra of secondary var(phi), as well as the ratios of var(phi)/pi^- and var(phi)/K^- production cross sections., Comment: 11 pages and 7 figures

We consider the experimental ratios of multistrange to strange antibaryon production and compare them to the standard Quark-Gluon String Model predictions. The significant differences between the experimental bar(Xi)+/bar(Lambda) and, especially, bar(Omega)+/bar(Lambda) values and model predictions can be interpreted as the signal of the existence of an additional source of multistrange antibaryon production. The possible connection of this additional source with Quark-Gluon Plasma (QGP) formation can turn the bar(Omega)+ production into a good QGP signature., Comment: 17 pages, 6 figures, and 3 tables. arXiv admin note: substantial text overlap with arXiv:1305.0388, arXiv:1207.6900

The experimental data on net proton and net Lambda-hyperon spectra obtained by the NA35 Collaboration, as well as the inclusive densities of Lambda and bar-Lambda obtained by NA49, NA57, and STAR collaborations, are compared with the predictions of the Quark-Gluon String Model. The contributions of String Junction diffusion, interactions with nuclear clusters, and the inelastic screening corrections are accounted for. The level of numerical agreement of the calculations with the experimental data is of about 20-30%. The predictions for LHC are also presented., Comment: 20 pages, 7 figures, and 1 table

We calculate the inclusive spectra of secondaries produced in soft (minimum bias) p+Pb collisions in the framework of Quark-Gluon String Model at LHC energy, and by taking into account the inelastic screening corrections (percolation effects). The role of these effects is expected to be very large at very high energies, and they should decrease the spectra about 3 times in the midrapidity region and increase them about 2 times in the fragmentation region at the energy of LHC., Comment: 18 pages and 10 figures. arXiv admin note: text overlap with arXiv:0802.2195

A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has non-zero baryon charge. This asymmetry is connected with the possibility of baryon charge diffusion in rapidity space. Such a diffusion should decrease the baryon charge in the fragmentation region and translate into the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. Another numerically more significant reason for the Feynman scaling violation comes from the fact that the average number of cutted Pomerons increases with initial energy. We present the quantitative predictions of the Quark-Gluon String Model (QGSM) for the Feynman scaling violation at LHC energies and at even higher energies that can be important for cosmic ray physics., Comment: 21 pages, 11 figures, and 1 table. arXiv admin note: substantial text overlap with arXiv:1107.1615, arXiv:1007.3206

We consider the first LHC data for elastic pp scattering in the framework of Regge theory with multiple Pomeron exchanges. The simplest eikonal approach allows one to describe differential elastic cross sections at LHC, as well as pp and $\bar{p}p$ scattering at lower collider energies, on a reasonable level., Comment: 11 pages, 5 figures, and 1 table

A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has non-zero baryon charge. This asymmetry is connected with the possibility of a baryon charge diffusion in rapidity space. Evidently, such a diffusion should decrease the baryon charge in the fragmentation region leading to the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. We present the quantitative predictions for the Feynman scaling violation at LHC energies and even at highier energies that can be important for cosmic ray physics., Comment: 17 pages and 9 figures

We consider the first LHC data for pp collisions in the framework of Regge phenomenology, and the Quark-Gluon String Model, and we present the corresponding predictions for both the integral cross sections and the inclusive densities of secondaries, that are determined by Pomeron exchange. All parameters were fixed long time ago for the description of the data at fixed target energies. The first measurements of the total inelastic cross section by ATLAS and CMS Collaborations are in agreement with our calculations. Also the inclusive densities measured in the central region are in agreement with our theoretical predictions on the accuracy level of about 10-15%., Comment: Contribution to the Proceedings of the Low-x Meeting 2011 (talk presented by Yu.M. Shabelski) 14 pages, 6 figures, and 4 tables

We consider the first LHC data for pp collisions in the framework of Regge theory. The integral cross sections and inclusive densities of secondaries are determined by the Pomeron exchange, and we present the corresponding predictions for them. The first measurements of inclusive densities in midrapidity region are in agreement with these predictions. The possible contribution of Odderon (Reggeon with alpha(Odd)(0) ~ 1 and negative signature) exchange to the differences in the inclusive spectra of particle and antiparticle in the central region could be significant at LHC energies. The first data of ALICE Collaboration are consistent with a very small Odderon contribution. Probably, further LHC data will definitely settle the question of the Odderon existence., Comment: 31 pages, 18 figures, and 6 tables

We describe the WA89 Collaboration experimental data on Lambda, Sigma(-), Sigma(+), Xi(-), and Omega(-) baryons, and bar(Lambda) and bar(Xi(+)) antibaryons production in Sigma(-) collisions with C and Cu targets at 345 GeV/c (sqrt(s_(Sigma N)) ~ 25.5 GeV) in the frame of the Quark-Gluon String Model. How the theoretical results compare to the experimental data is discussed. Finally, some relations among the values of the model parameters obtained with the help of quark combinatorics are presented., Comment: 18 pages, 13 figures, and 1 table.

We prove that the Tutte polynomial of a coloopless paving matroid is convex along the portions of the line segments x+y=p lying in the positive quadrant. Every coloopless paving matroids is in the class of matroids which contain two disjoint bases or whose ground set is the union of two bases of M*. For this latter class we give a proof that T_M(a,a) <= max {T_M(2a,0), T_M(0,2a)} for a >= 2. We conjecture that T_M(1,1) <= max {T_M(2,0), T_M(0,2)} for the same class of matroids. We also prove this conjecture for some families of graphs and matroids., Comment: 17 pages

Charm production in pp collisions is considered in the framework of perturbative QCD. The values of two parameters, the charm quark mass $m_c$ and the QCD scale mu^2, are determined from the comparison of the theoretical calculations with experimental data. The RHIC data on charm and beauty production are compared with the k_T-factorization approach predictions and with standard NLO QCD. The calculated results underestimate the STAR Collaboration data. The role of possible nuclear effects is discussed. The predictions for LHC energies are also given., Comment: 15 pages, 6 figures, and 3 tables

The information about sizes and nuclear density distributions in unstable (radioactive) nuclei is usually extracted from the data on interaction of radioactive nuclear beams with a nuclear target. We show that in the case of nucleus-nucleus collisions the values of the parameters depend rather strongly on the considered theoretical approach and on the assumption about the parametrization of the nuclear density distribution. The obtained values of root-mean-square radii (R_{rms}) for stable nuclei with atomic weights A = 12-40 vary by approximately 0.1 fm when calculated in the optical approximation, in the rigid target approximation, and using the exact expression of Glauber Theory. We present several examples of R_{rms} radii calculations using these three theoretical approaches and compare these results with the data obtained from electron-nucleus scattering., Comment: 14 Pages, 5 Figure, and 1 Table

We consider the possible contribution of Odderon (Reggeon with alpha_(Odd)(0) similar to 1 and negative signature) exchange to the differences in the total cross sections of particle and antiparticle, to the ratios of real/imaginary parts of the elastic pp amplitude, and to the differences in the inclusive spectra of particle and antiparticle in the central region. The experimental differences in total cross sections of particle and antiparticle are compatible with the existence of the Odderon component but such a large Odderon contribution seems to be inconsistent with the values of Re/Im ratios. In the case of inclusive particle and antiparticle production the current energies and/or accuracy of the experimental data don't allow a clear conclusion. It is expected that the LHC will finally solve the question of the Odderon existence., Comment: Lecture given by Yu.M. Shabelski at the XLIII PNPI Winter School on Physics, St.Petersburg, Russia, February 2009 (30 pages, 13 figures, and 9 tables)

We consider the possible contribution of Odderon (Reggeon with \alpha_{Odd}(0) \sim 1 and negative signature) exchange to the differences in the total cross sections of particle and antiparticle, to the ratios of real/imaginary parts of the elastic pp amplitude, and to the differences in the inclusive spectra of particle and antiparticle in the central region. The experimental differences in total cross sections of particle and antiparticle are compatible with the existence of the Odderon component but such a large Odderon contribution seems to be inconsistent with the values of Re/Im ratios. In the case of inclusive particle and antiparticle production the current energies and/or accuracy of the experimental data don't allow a clear conclusion., Comment: 24 pages, 12 figures, and 4 tables

The midrapidity inclusive densities of different secondaries are calculated in the framework of the Quark-Gluon String Model. The transfer of baryon number in rapidity space due to the gluon string junction propagation leads to a significant effect on the net baryon production. The numerical results are in reasonable agreement with RHIC experimental data., Comment: Contribution to the Proceedings of the XLIII Rencontres de Moriond: QCD and High Energy Interactions, La Thulile, Italy, 8-15 March 2008. Talk presented by C. Merino (4 pages and 2 figures)

We evaluate both the tau lepton energy loss produced by photonuclear interactions and the neutrino charged current cross section at ultra-high energies, both relevant to neutrino bounds with Earth-skimming tau neutrinos., Comment: Contribution to the Proceedings of the XLIII Rencontres de Moriond: QCD and High Energy Interactions, La Thulile, Italy, 8-15 March 2008. Talk presented by G. Parente (4 pages and 3 figures)

In the framework of Quark-Gluon String Model we calculate the inclusive spectra of secondaries produced in d+Au collisions at intermediate (CERN SPS) and at much higher (RHIC) energies. The results of numerical calculations at intermediate energies are in reasonable agreement with the data. At RHIC energies numerically large inelastic screening corrections (percolation effects) should be accounted for in calculations. We extract these effects from the existing RHIC experimental data on minimum bias and central d+Au collisions. The predictions for p+Au interactions at LHC energy are also given., Comment: 18 pages and 10 figures

We evaluate both the tau lepton energy loss produced by photonuclear interactions and the neutrino charged current cross section at ultra-high energies, relevant to neutrino bounds with Earth-skimming tau neutrinos, using different theoretical and phenomenological models for nucleon and nucleus structure functions. The theoretical uncertainty is estimated by taking different extrapolations of the structure function F2 to very low values of x, in the low and moderate Q2 range for the tau lepton interaction and at high Q2 for the neutrino-nucleus inelastic cross section. It is at these extremely low values of x where nuclear shadowing and parton saturation effects are unknown and could be stronger than usually considered. For tau and neutrino energies E=10^9 GeV we find uncertainties of a factor 4 for the tau energy loss and of a factor 2 for the charged current neutrino-nucleus cross section., Comment: 20 pages and 11 figures

We consider the phenomenological implications of the assumption that baryons are systems of three quarks connected through gluon string junction. The transfer of baryon number in rapidity space due to the string junction propagation is considered in detail. At high energies this process leads to a significant effect on the net baryon production in hN collisions at mid-rapidities. The numerical results for midrapidity inclusive densities of different secondaries in the framework of the Quark-Gluon String Model are in reasonable agreement with the experimental data. One universal value lambda ~ 0.25 for the strangeness suppression parameter correctly describes the yield ratios of Lambda/p, Xi/Lambda, and Omega/Xi. The predictions for pp collisions at LHC energies are also presented., Comment: 12 pages, 5 figures, and 1 table

The process of secondary baryon production in pi(+-)p collisions at high energies in the central and forward fragmentation regions is considered in the framework of the Quark-Gluon String Model. The contribution of the string-junction mechanism to the baryon production is analysed. The results of numerical calculations are in reasonable agreement with the experimental data on the Lambda/bar(Lambda) and p/bar(p)$ asymmetries., Comment: Contribution to the Proceedings of QCD@Work 2007, International Workshop on Quantum Chromodynamics, Theory and Experiment, Martina Franca-Valle d'Itria, Italy, June 16-20, 2007 (6 pages and 4 figures)

The RHIC data on charm production are compared with the kT-factorization approach predictions, both standard NLO QCD and FONLL. The calculated results underestimate the STAR Collaboration data. The role of possible nuclear effects is discussed., Comment: Talk given at the Ninth Workshop on Non-Perturbative Quantum Chromodynamics, Paris (France), June 4th-8th, 2007 (8 pages and 3 figures)

The asymmetry of strange baryon production in Kp interactions at high energies is considered in the framework of the Quark-Gluon String Model. The contribution of the String-Junction Mechanism to the strange baryon production is analysed., Comment: Contribution to the proceedings of the IV International Conference on Quarks and Nuclear Physics (QNP06), Universidad Complutense, Madrid (Spain), 5-10 June 2006 (2 pages with 2 figures)

The process of baryon production in K p collisions at high energies is considered in the framework of the Quark-Gluon String Model. The contribution of the string-junction mechanism to the strange baryon production is analysed. The results of numerical calculations are in reasonable agreement with the data on inclusive spectra of p, Lambda, bar{Lambda}, and on the bar{Lambda}/Lambda asymmetry. The predictions for Xi and Omega baryons are presented., Comment: 19 pages, 7 figures

The process of Lambda-baryon production in pi-p collisions is considered. The contribution of the string-junction mechanism to the strange baryon production in meson-baryon scattering is anlysed. The results of numerical calculations in the framework of the Quark-Gluon String model are in reasonable agreement with the data., Comment: 10 pages and 5 figues

Strong correlations are obtained between the number and the average transverse momentum of jets emitted by the exchange of a single BFKL Pomeron., Comment: Contribution to the Proceedings of the XXXII International Symposium on Multiparticle Dynamics (ISMD), Alushta, Crimea (Ukraine), 7-13 September 2002 (5 pages and 1 figure)

A review is presented of the different theoretical models proposed to approach consistently the interplay between soft and hard physics, that can now be studied experimentally at HERA for the first time., Comment: 14 pages

Strong correlations between the number of emitted jets and their average transverse momentum are found for the events resulting from the exchange of a single BFKL pomeron. transverse momentum are found for the events resulting from the exchange., Comment: 6 pages + 4 figures

We propose the asymmetry in the fractional energy of charm versus anticharm jets produced in high energy diffractive photoproduction as a sensitive test of the interference of the Odderon (C = -) and Pomeron (C = +) exchange amplitudes in QCD. If measured at HERA, this asymmetry could provide the first experimental evidence of the Odderon., Comment: Contribution to the Proceedings of the International Euroconference in Quantum Chromodynamics: 15 Years of the QCD - Montpellier Conference (QCD 00), Montpellier, France, 6-12 July 2000

It is shown that the CKMT model for the nucleon structure function F2, taken as the initial condition for the NLO evolution equations in perturbative QCD, provides a good description of the HERA data when presented in the form of the logarithmic slopes of F2 vs x and Q2 (Caldwell-plot), in the whole available kinematic ranges. Also the results obtained for the behavior of the gluon component of a nucleon are presented., Comment: 16 pages, 10 figures

The CKMT model for the nucleon structure function F_2 is in good agreement with the HERA data at low and moderate Q^2. The fit to the same data obtained with a modified version of the model in which a logarithmic dependence on Q^2 has been included is also discussed. Finally, we show how the parametrization of the CKMT model for the nucleon structure function F_2 describes the HERA data when presented in the Caldwell-plot as the behavior of the logarithmic slopes of F_2 vs x and Q^2., Comment: 15 pages (Latex), 6 figures. Talk presented at the XVII Autumn School on QCD: Perturbative or Nonperturbative?, 29 September-4 October 1999, IST, Lisbon (Portugal) (submitted to the Proceedings)

We review our recent works on tests of perturbative QCD, inspired by the relation between the hadronic decay of the tau lepton and the e+ e- annihilation into hadrons. First, we present a set of commensurate scale relations that probe the self-consistency of leading-twist QCD predictions for any observable which defines an effective charge. These tests are independent of the renormalization scheme and scale, and are applicable over wide data ranges. As an example we apply this approach to R_{e+ e-}. Second, using a differential form of these conmensurate scale relations, we present a method to measure the QCD Gell-Mann--Low Psi function., Comment: To appear in the proceedings of the QCD 99 Euroconference, 7-13th July 1999 Montpellier, France 4 pages, uses espcrc2.sty (included)

We present a general method for extracting the Gell Mann-Low logarithmic derivative of an effective charge of an observable directly from data as a mean for empirically verifying the universal terms of the QCD $\beta$-function. Our method avoids the biases implicit in fitting to QCD-motivated forms as well as the interpolation errors introduced by constructing derivatives from discrete data. We also derive relations between moments of effective charges as new tests of perturbative QCD., Comment: 15 pages, 1 figure (uses psfig)

It is shown that the CKMT model for the nucleon structure function $F_2$ gives a good description of the recent HERA data at low and moderate $Q^2$. Also the fit to the same data obtained with a modified version of the model in which a logarithmic dependence on $Q^2$ has been included, is presented. For moderate values of $Q^2$, in the current available range of $x$, the first parametrization leads to a better description of the data., Comment: Tex (12 pages), 2 ps fig

Gribov theory is applied to investigate the shadowing effects in the structure functions of nuclei. In this approach these effects are related to the process of diffractive dissociation of a virtual photon. A model for this diffractive process, which describes well the HERA data, is used to calculate the shadowing in nuclear structure functions. A reasonable description of the $x$, $Q^2$ and A-dependence of nuclear shadowing is achieved., Comment: TeX, 15 pages, 7 figures in 6 ps-files

Gribov theory is applied to investigate the shadowing effects in the structure functions of nuclei. In this approach these effects are related to the process of diffractive dissociation of a virtual photon. A model for this diffractive process, which describes well the HERA data, is used to calculate the shadowing in nuclear structure functions. A reasonable description of the x, Q^2 and A-dependence of nuclear shadowing is achieved., Comment: TeX, 10 pages, 7 figures in 6 ps-files

The rapidity distribution of $\Lambda$ and $\bar{\Lambda}$ produced in nucleus-nucleus collisions at CERN energies is studied in the framework of an independent string model - with quark-antiquark as well as diquark-antidiquark pairs in the nucleon sea. It is shown that, besides the $\Lambda$-$\bar{\Lambda}$ pair production resulting from the fragmentation of sea diquarks, final state interactions of co-moving secondaries $\pi + N \to K + \Lambda$ and $\pi + \bar{N} \to K + \bar{\Lambda}$ are needed in order to reproduce the data. Predictions for $Pb$-$Pb$ collisions are presented., Comment: Plain TeX + epsf, 40 pages; 1 Postscript-table and 7 Postscript figures (uuencoded)

We show that the previously introduced CKMT model, based on conventional Regge theory, gives a good description of the HERA data on the structure function F_2^D for large rapidity gap (diffractive) events. These data allow, not only to determine the valence and sea quark content of the Pomeron, but also, through their Q^2 dependence, give information on its gluonic content. Using DGLAP evolution, we find that the gluon distribution in the Pomeron is very hard and the gluons carry more momentum than the quarks. This indicates that the Pomeron, unlike ordinary hadrons, is a mostly gluonic object. With our definition of the Pomeron flux factor the total momentum carried by quarks and gluons turns out to be 0.3-0.4 - strongly violating the momentum sum rule., Comment: C-Shell archive of a PostScript file containing a 20 page paper with text and 12 figures in it

The diffraction dissociation of virtual photons is considered in the framework of conventional Regge theory. It is shown that the recent HERA data on large rapidity gap events can be successfully described in terms of the Pomeron structure function. Using Regge factorization, the latter can be related to the deuteron structure function. The parameters which relate these two structure functions are determined from soft hadronic diffraction data. The size of the shadowing corrections at low x and large Q**2 is also obtained., Comment: 17 pages, TEX, preprint LPTHE Orsay 94-42

In the framework of conventional Regge theory we present a common description of total photon-proton cross-section and proton structure functions in the region $0 \leq Q^2 \leq 5 \ {\rm GeV}^2$. Using it as an initial condition in the perturbative QCD evolution equation, we describe structure functions at any $Q^2$ and $x$ - including the small $x$ region explored at HERA., Comment: 10 pages + 7 figures available on request, Plain TeX, Preprint LPTHE Orsay 94-34