Related papers: Instantons, Spin Crisis and High $Q^2$ Anomaly at …
Numerical and anaytical studies of the instanton liquid model have allowed the determination of many hadronic parameters during the last 13 years. Most part of this thesis is devoted to the extension of the analytical methods. The meson…
I explain how instantons break chiral symmetry and how do they bind quarks in baryons. The confining potential is possibly irrelevant for the task.
We investigate the instanton effects on the heavy-quark potential,including its spin-dependent part, based on the instanton liquid model. Starting with the central potential derived from the instanton vacuum, we obtain the spin-dependent…
We construct improved QCD sum rules for the nucleon magnetic moments by implementing direct-instanton contributions to the operator product expansion of the nucleon correlator in a magnetic background field. The instanton contributions are…
We present estimates of possible data on spin-dependent asymmetries in inclusive scattering of high energy polarized electrons by high energy polarized protons at HERA, including statistical errors, and discuss systematic uncertainties. We…
In this thesis we study two processes in which instantons may play an important role: the decays of charmonium states $\eta_c$, $\chi_c$ and glueball and the OZI violation in channels relevant to the proton spin decomposition puzzle. We…
We discuss the role of nucleon and its excited state poles in the twist expansion of the nucleon structure function moments. We find that the nucleon pole contribution was overestimated in previous analyses by a factor of two. Inclusion of…
I present some comments on the relationship between the small-$x$ behaviour of the parton (quark and gluon) densities and the scaling violation of the proton structure function $F_{2}(x,Q^{2})$.
We discuss how the proton structure function F2 is described in the HERA kinematic range by double asymptotic expressions for low x and large Q^2. From a NLO double asymptotic approximation of recent data from the H1 experiment at HERA we…
A physical model is presented for the non-perturbative parton distributions in the nucleon. This is based on quantum fluctuations of the nucleon into baryon-meson pairs convoluted with Gaussian momentum distributions of partons in hadrons.…
The gluon contributions to $F_L(x,Q^2)$ in ${\cal O}(\alpha_s)$ are calculated taking into account the transverse momentum of the initial state parton. In comparison with collinear factorization $F_L(x,Q^2)$, is not affected at large $x$…
We report briefly on a broad and systematic study of possible manifestations of QCD-instantons at HERA. We concentrate on the high multiplicity final state structure, reminiscent of an isotropically decaying ``fireball''. First results of a…
We analyze the quark mass dependence of photon gluon fusion in polarized deep inelastic scattering for both the intrinsic and extrinsic gluon distributions of the nucleon. We calculate the effective number of flavors for each of the heavy…
The gluon fields screening in the stochastic vacuum of gluodynamics is studied. The effective action is derived for the instanton interacting with nonperturbative fields. Quantum nonperturbative effects are shown to affect greatly the shape…
A ``fiducial'' kinematical region for our calculations of instanton (I)-induced processes at HERA within I-perturbation theory is extracted from recent lattice simulations of QCD. Moreover, we present the finalized I-induced cross-sections…
Recent results from the H1 experiment [1] have confirmed the existence of a substantial baryon asymmetry of the proton sea at small $x$ with magnitude predicted in hep-ph/9607486. This is a strong support for the idea [3] that baryon number…
String instanton Yukawa corrections from Euclidean D-branes are investigated in an effective Standard Model theory obtained from the minimal U(3)xU(2)xU(1) D-brane configuration. In the case of the minimal chiral and Higgs spectrum, it is…
The spin-dependent structure functions g_2 (x, Q^2) are investigated within the framework of the chiral quark soliton model. It turns out that the twist-3 part of g_2 (x, Q^2) gives nonnegligible contributions to the total distributions at…
The leading chiral contributions to the quark and gluon components of the proton spin are calculated using heavy-baryon chiral perturbation theory. Similar calculations are done for the moments of the generalized parton distributions…
This is a talk given at Ringberg Workshop:"New Trends in HERA Physics", 30 May - 4 June, 1999.In this talk we discuss how deeply the region of high parton densities has been studied experimentally at HERA. We show that the measurements of…