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I. P. Ivanov

Publications and source records attributed to I. P. Ivanov.

71 records · Page 4Linked to original sources
arXiv2003

Diffractive production of vector mesons in Deep Inelastic Scattering within k_t-factorization approach

In this work we give a theoretical description of the elastic vector meson production in diffractive DIS developed within the k_t-factorization formalism. Since the k_t-factorization scheme does not require large values of Q^2+m_V^2, we conduct an analysis that is applicable to all values of Q^2 from photo- up to highly virtual production of vector mesons. The basic quantity in this approach -- the unintegrated gluon structure function -- was for the first time extracted from the experimental data on F_{2p}, thoroughly investigated, and consistently used in the vector meson production calculation. Moreover, by limiting ourselves to the lowest Fock state of the vector meson, we were able to construct in a closed form the theory of spin-angular coupling in the vector meson. This allowed us for the first time to address the production of a vector meson in a given spin-angular state. We performed an extensive analytical and numerical investigation of the properties of 1S, 2S, and D-wave vector meson production reactions. Treating the physical ground state vector mesons as purely 1S states, we observed a good overall agreement with all available experimental data on vector meson production. For the excited states, our analysis predicts a picture which is remarkably different from 1S-state, so that such reactions can be regarded as potential sources of new information on the structure of excited states in vector mesons.

hep-ph↗
arXiv2003

Possibility of the odderon discovery via observation of charge asymmetry in the diffractive pi+pi- production at HERA

The interference between the Pomeron and possible odderon mechanisms of diffractive pi+pi- photoproduction results in charge asymmetry of the produced pions. The observation of charge asymmetry of pions at moderate M_{pi+pi-} will be an undoubted signal of odderon existence. To make numeral estimates more definite, we limit ourselves by the region M_{pi+pi-} = 1.1 -- 1.5 GeV, where in the odderon mechanism of dipion production, the production via single f_2(1270) resonance is expected to be dominant. We find a very statistically significant effect of the odderon induced charge asymmetry even with very modest estimates for the f_2 photoproduction cross section (without referring to any particular model of the odderon).

hep-ph↗
arXiv2002

High Density QCD, Saturation and Diffractive DIS

We review a consistent description of the fusion and saturation of partons in the Lorentz-contracted ultrarelativistic nuclei in terms of a nuclear attenuation of color dipole states of the photon and collective Weizsäcker-Williams (WW) gluon structure function of a nucleus. Diffractive DIS provides a basis for the definition of the WW nuclear glue. The point that all observables for DIS off nuclei are uniquely calculable in terms of the nuclear WW glue amounts to a new form of factorization in the saturation regime.

hep-ph↗
arXiv2002

High Density QCD and Saturation of Nuclear Partons

We review the recent finding of the two-plateau momentum distribution of sea quarks in deep inelastic scattering off nuclei in the saturation regime. The diffractive plateau which dominates for small $\bp$ measures precisely the momentum distribution of quarks in the beam photon, the rôle of the nucleus is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a substantial nuclear broadening of the momentum distribution. Despite this nuclear broadening, the observed final state and initial state sea quark densities do coincide exactly. We emphasize how the saturated sea is generated from the nuclear-diluted Weizsäcker-Williams because of the anti-collinear splitting of gluons into sea quarks.

hep-ph↗
arXiv2002

Diffractive Hard Dijets and Nuclear Parton Distributions

Diffraction plays an exceptional role in DIS off heavy nuclei. First, diffraction into hard dijets is an unique probe of the unintegrated glue in the target. Second, because diffraction makes 50 per cent of total DIS off a heavy target, understanding diffraction in a saturation regime is crucial for a definition of saturated nuclear parton densities. After brief comments on the Nikolaev-Zakharov (NZ) pomeron-splitting mechanism for diffractive hard dijet production, I review an extension of the Nikolaev-Schafer-Schwiete (NSS) analysis of diffractive dijet production off nuclei to the definition of nuclear partons in the saturation regime. I emphasize the importance of intranuclear final state interactions for the parton momentum distributions.

hep-ph↗
arXiv2002

Diffractive Vector Meson Production in k_t-Factorization Approach

We describe the current status of the diffractive vector meson production calculations within the k_t-factorization approach. Since the amplitude of the vector meson production off a proton is expressed via the differential gluon structure function (DGSF), we take a closer look at the latter and present results of our new improved determination of the DGSF from the structure function F_2p. Having determined the differential glue, we proceed to the k_t-factorization results for the production of various vector mesons. We argue that the properties of the vector meson production can reveal the internal spin-angular and radial structure of the vector meson.

hep-ph↗
arXiv2001

CP odd anomalous interactions of Higgs boson in its production at Photon Colliders

We discuss the potentialities of the study of CP-odd interactions of the Higgs boson with photons via its production at gamma-gamma and e-gamma colliders. Our treatment of H-gamma-gamma and H-Z-gamma anomalous interactions includes a set of parameters, whose impact on physical observables has not been considered before. We focus on two reactions - gamma+gamma-->H and e+gamma-->eH - and introduce the polarization and/or azimuthal asymmetries that are particularly sensitive to specific features of anomalies. We discuss the ways of disentangling effects of physically different parameters of anomalies and estimate what magnitude of CP violating phenomena can be seen in these experiments.

hep-ph↗
arXiv2000

Anatomy of the Proton Structure Functions in $κ$-factorization

We present the first experiment-based parameterization of differential gluon structure function, which is called upon in many applications. We compare $κ$-factorization and DGLAP approaches and analyze properties of DGSF, with special emphasis on soft-to-hard/hard-to-soft diffusion.

hep-ph↗
arXiv2000

Diffractive Vector Meson Production In A Unified $κ$-Factorization Approach

In the framework of the $κ$-factorization approach and on the basis of recently determined DGSF, we calculated the production rates of ground and excited (2S and D wave) states of vector mesons and investigated their various kinematical and spin dependencies. We also addressed the issue of S/D wave mixing in quarkonia.

hep-ph↗
arXiv2000

Anatomy of the differential gluon structure function of the proton from the experimental data on F_2p

The use of the differential gluon structure function of the proton ${\cal F}(x,Q^{2})$ introduced by Fadin, Kuraev and Lipatov in 1975 is called upon in many applications of small-x QCD. We report here the first determination of ${\cal F}(x,Q^{2})$ from the experimental data on the small-x proton structure function $F_{2p}(x,Q^{2})$. We give convenient parameterizations for ${\cal F}(x,Q^{2})$ based partly on the available DGLAP evolution fits (GRV, CTEQ & MRS) to parton distribution functions and on realistic extrapolations into soft region. We discuss an impact of soft gluons on various observables. The x-dependence of the so-determined ${\cal F}(x,Q^{2})$ varies strongly with Q^2 and does not exhibit simple Regge properties. None the less the hard-to-soft diffusion is found to give rise to a viable approximation of the proton structure function F_{2p}(x,Q^2) by the soft and hard Regge components with intercepts Δ_{soft}=0 and Δ_{hard}\sim 0.4.

hep-ph↗
arXiv1999

Diffractive production of S and D wave vector mesons in DIS

In this work the production of vector mesons in diffractive DIS is analyzed, with an emphasis on the impact of the internal spin structure of a vector meson upon its virtual photoproduction rate. We derived the full sets of s-channel helicity conserving and violating amplitudes for pure S and D wave vector mesons and found a striking difference between S and D wave vector meson production. First, in the case of helicity conserving amplitudes, D wave vector mesons were found to exhibit dramatically different Q^2-behavior due to abnormally large higher twist contributions. Besides, we found that helicity conserving amplitudes for S and D states are numerically comparable, which makes the physical rho meson very sensitive to D wave admixture. Second, the helicity violating amplitudes turned out large both for S and D wave states of light vector mesons and for D wave heavy vector mesons as well. Aiming at producing sort of a manual on the diffractive vector meson production, we carried out all calculations in a pedagogical manner with maximally full presentation of intermediate steps and accompanied them with detailed qualitative discussion.

hep-ph↗
arXiv1999

Search for fourth generation quarks and leptons at the Fermilab Tevatron and CERN Large Hadron Collider

If next generations of heavy quarks and leptons exist within the standard model (SM), they can manifest themselves in Higgs boson production at the Tevatron and the LHC, before being actually observed. This generation leads to an increase of the Higgs boson production cross section via gluon fusion at hadron colliders by a factor 6-9. So, the study of this process at the Tevatron and LHC can finally fix the number of generations in the SM. Using the $WW^*$ Higgs boson decay channel, the studies at the upgraded Tevatron will answer the question about the next generation for mass values 135 GeV $\lsim M_H\lsim 190$ GeV. Studying the $τ\barτ$ channel we show its large potential for the study of the Higgs boson at the LHC even in the standard case of three generations. At the Tevatron, studies in this channel could explore the mass range 110-140 GeV.

hep-ph↗
arXiv1999

Anomalous interactions in Higgs boson production at photon colliders

We discuss the potentialities of the non-standard interaction study via the Higgs boson production at photon ($\ggam$ and $eγ$) colliders. We estimate the scale of New Physics phenomena beyond the standard model that can be seen in the experiments with Higgs boson production. In particular, the effect of new heavy particles within the standard model is shown to be quite observable.

hep-ph↗
arXiv1999

Diffraction driven steep rise of spin structure function $g_{LT}=g_{1}+g_{2}$ at small x and DIS sum rules

We derive a unitarity relationship between the spin structure function $g_{LT}(x,Q^{2})=g_{1}(x,Q^{2})+g_{2}(x,Q^{2})$, the LT interference diffractive structure function and the spin-flip coupling of the pomeron to nucleons. Our diffractive mechanism gives rise to a dramatic small-$x$ rise $g_{LT}(x,Q^{2}) \sim g^{2}(x,\bar{Q}^{2}) \sim (1/x)^{2(1+δ_{g})}$, where $δ_{g}$ is an exponent of small-$x$ rise of the unpolarized gluon density in the proton $g(x,\bar{Q}^{2})$ at a moderate hard scale $\bar{Q}^{2}$ for light flavour contribution and large hard scale $\bar{Q}^{2} \sim m_{f}^{2}$ for heavy flavour contribution. It invalidates the Burkhardt-Cottingham sum rule. The found small-$x$ rise of diffraction driven $g_{LT}(x,Q^{2})$ is steeper than given by the Wandzura-Wilczek relation under conventional assumptions on small-$x$ behaviour of $g_{1}(x,Q^{2})$.

hep-ph↗
arXiv1999

Diffractive S and D-wave vector mesons in deep inelastic scattering

We derive helicity amplitudes for diffractive leptoproduction of the S and D wave states of vector mesons. We predict a dramatically different spin dependence for production of the S and D wave vector mesons. We find very small $R=σ_{L}/σ_{T}$ and abnormally large higher twist effects in production of longitudinally polarized D-wave vector mesons.

hep-ph↗
arXiv1997

Higgs Boson Search At Photon Collider For $M_H=140-190$ GeV

A Higgs boson within the mass range $M_H=140-190$ GeV can be discovered at a photon collider in the reaction $γγ\to WW$ (with real or virtual W) with the luminosity integral about 1 fb$^{-1}$. The reasonable resolution in the effective mass of the WW system is required.

hep-ph↗