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N. I. Kochelev

Publications and source records attributed to N. I. Kochelev.

At least 37 records · Page 2Linked to original sources
arXiv2004

Instanton induced quark dynamics and the pentaquark

We analyze the existence of the exotic $Θ^+$ from the perspective of instanton induced quark dynamics. The 't Hooft interaction gives strong attraction in specific channels of the triquark $ud\bar s$ and diquark $ud$ configurations. In particular it leads to a light $ud\bar s$ triquark cluster, with the mass around $750 {\rm MeV}$, in the I=0, $S=1/2$ and color 3 configuration, and a light $ud$-diquark configuration, with mass $440 {\rm MeV}$, in the I=0, S=0 and color {$\bar{3}$} configuration. If we consider the pentaquark as a bound state of such triquark and diquark configurations in a relative L=1 state we obtain good agreement with the data. The small width of $Θ^+$ has a natural explanation in this model.

hep-ph↗
arXiv2003

Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays

The scale of low energy c-cbar and b-bbar cross sections on light hadrons is of great importance to searches for the quark gluon plasma using the heavy-quarkonium suppression signature. Unfortunately, little is known about these near-threshold cross sections at present, and recent theoretical estimates span many orders of magnitude. Here we use experimental data on the four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' -> pi pi Upsilon', combined with simple models of the transition amplitudes, to estimate the pion scattering cross sections of c-cbar and b-bbar mesons near threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' -> pi Upsilon'' and their time-reversed analogues. Our results may be useful in constraining theoretical models of the strong interactions of heavy quarkonia, and can be systematically improved through future detailed studies of dipion decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.

nucl-th↗
arXiv2003

The Pauli form factor of the quark induced by instantons

The non-perturbative contribution to the Pauli form factor of the quark, $F_2(Q^2)$, is calculated within an instanton model for the QCD vacuum. It is shown that the instantons give a large negative contribution to the form factor.

hep-ph↗
arXiv2002

DIS structure functions and the double-spin asymmetry in $ρ^0$ electroproduction within a Regge approach

The proton, neutron and deuteron structure functions $F_2(x,Q^2)$ and $g_1(x,Q^2)$, measured at intermediate $Q^2$, are analyzed within a Regge approach. This analysis serves to fix the parameters of this scheme which are then used to calculate, in a unified Regge approach, the properties of $ρ^0$ meson electroproduction on the proton and the deuteron. In this way, the double-spin asymmetry observed at HERMES in $ρ^0$ electroproduction on the proton, can be related to the anomalous behavior of the flavor-singlet part of the spin-dependent structure function $g_1(x,Q^2)$ at small $x$.

hep-ph↗
arXiv2001

A mechanism for the Double-Spin Asymmetry in Electromagnetic $ρ$ Production at HERMES

We calculate the contribution of meson and pomeron exchanges to the double-spin asymmetry in $ρ$-meson electromagnetic production at HERMES energies. We show that the observed double-spin asymmetries, which are large, can be explained by the interference between the natural parity $f_2$-secondary Reggeon and the unnatural parity anomalous $f_1$ exchanges.

hep-ph↗
arXiv2001

Gluonic effects in vector meson photoproduction at large momentum transfers

Non-perturbative QCD mechanisms are of fundamental importance in strong interaction physics. In particular, the flavor singlet axial anomaly leads to a gluonic pole mechanism which has been shown to explain the $η^{\prime}$ mass, violations of the OZI rule and more recently the proton spin. We show here that the interaction derived from the gluonic pole exchange explains the high momentum transfer behavior of the photoproduction cross sections of vector mesons at JLab energies.

hep-ph↗
arXiv2001

Instantons and the $ΔI=1/2 $ Rule

The instanton induced interaction leads to a significant enhancement of the $A_0$ weak amplitude determining the $ΔI=1/2$ rule, through the contribution of operators with dimension d=9, as we show in the weak $K\to ππ$ decay.

hep-ph↗
arXiv2001

Evidence for the flavor singlet axial anomaly related effects in $ϕ$ meson electromagnetic production at large momentum transfers

The gluonic contributions to the conventional PCAC formulas due to flavor singlet axial anomaly have been instrumental in explaining the mass of the $η^{\prime}$ and providing a plausible explanation for solving the spin crisis. We show that they also play an important role in the description of photo- and electroproduction of vector mesons at low energy and high momentum transfers. We calculate the contributions of this type to $ϕ$ meson electromagnetic production in a model, which contains also a soft pomeron, and find agreement with recent CLAS data.

hep-ph↗
arXiv2001

A New Mechanism for Single Spin Asymmetries in Strong Interactions

It is shown that the contribution of the instantons to the fragmentation of quarks leads to the appearance of a imaginary part in diagrams of quark-quark scattering at large transfer momentum. The imaginary part comes from the analytical continuation of the instanton amplitudes from Euclidean to Minkowsky space-time and reflects quasiclassical origin of instanton solution of QCD equations of motion. This phenomenon and instanton--induced quark spin-flip give a new nonperturbative mechanism for the observed anomalous single-spin asymmetries in hadron-hadron and lepton-hadron interactions.

hep-ph↗
arXiv2000

New Anomalous Exchange in Regge Phenomenology and Hard Diffraction

A new mechanism for hard diffraction based on the anomalous $f_1$ trajectory exchange, which we identify as the odd signature partner of the Pomeron, is suggested. We calculate the contribution of the $f_1$ exchange to elastic and dissociative electromagnetic production of vector mesons and show that it gives a dominant contribution to the differential cross sections at large momentum transfers.

hep-ph↗
arXiv2000

The role of secondary Reggeons in central meson production

We estimate the contribution of f_2 trajectory exchange to the central ηand η^\prime production. It is shown that secondary Reggeons may give a large contribution to processes of double diffractive meson production at high energy.

hep-ph↗
arXiv2000

Diffractive Lambda_c^+ Productions in Polarized pp Reactions and Polarized Gluon Distribution

To test the model of the polarized gluon distribution $ΔG(x, Q^2)$ in the proton, we propose a new process, diffractive $Λ_c^+$ productions in polarized $pp$ reactions, which will be observed in the forthcoming RHIC and also the proposed HERA-$\vec {\rm N}$ experiments. The spin correlation between the target proton and the $Λ_c^+$ produced in the target fragmentation region largely depends on $ΔG(x, Q^2)$ and thus, the process is quite promising for testing the models of $ΔG(x, Q^2)$.

hep-ph↗
arXiv1999

Instantons and $η$ Meson Production near threshold in NN collisions

An enhancement for the $η$ production in proton-neutron collisions as compared with that in proton-proton scattering has been recently observed. We present a calculation for the production cross section, in proton-neutron collisions near threshold, within instanton model for the QCD vacuum and show that a specific flavor dependent nonperturbative quark-gluon interaction related to instantons is able to explain the observed enhancement.

hep-ph↗
arXiv1999

Ultra-High Energy Cosmic Rays and Stable H-dibaryon

It is shown that an instanton induced interaction between quarks produces a very deeply bound H-dibaryon with mass below 2M_N, M_H=1718 MeV. Therefore the H-dibaryon is predicted to be a stable particle. The reaction of photodisintegration of H-dibaryon to $2Λ$ in during of its penetration into cosmic microwave background will result in a new possible cut-off in the cosmic-ray spectrum. This provides an explanation of ultra-high energy cosmic ray events observed above the GZK cut-off as a result of the strong interaction of high energy H-dibaryons from cosmic rays with nuclei in Earth's atmosphere.

hep-ph↗
arXiv1999

Pomeron Fusion and Central $η$ and $η'$ Meson Production

The contribution of pomeron fusion to the cross section of $η$ and $η'$ productions in double-diffractive scattering has been calculated within the Donnachie-Landshoff model of pomeron. It is shown that the double pomeron exchange mechanism does not explain the full set of the recent data of WA102 Collaboration, though it might not be inconsistent with $η'$ productions.

hep-ph↗
arXiv1999

Unusual Properties of the Central Production of Glueballs and Instantons

It is shown that instantons provide a natural mechanism to explain an unusual azimuthal dependence of the production of the even-parity glueball candidates in central pp collision. A different azimuthal dependence for instanton-induced production of the odd-parity glueballs is predicted.

hep-ph↗
arXiv1998

Further Comments on a Vanishing Singlet Axial Vector Charge

The recent suggestion of a vanishing flavor-singlet axial charge of nucleon due to a nontrivial vacuum structure is further amplified. A perturbative QCD discussion, applicable for the heavy quark contributions, relates it to the physics of the decoupling theorem. It is also shown that $g_{A}^{0}\simeq 0$ leads to a negative $η'$-meson-quark coupling, which has been found to be compatible with the chiral quark model phenomenology.

hep-ph↗