arXiv subjects

L. Motyka

Publications and source records attributed to L. Motyka.

43 records · Page 3Linked to original sources

arXiv2000

The QCD pomeron at TESLA - motivation and exclusive J/psi production

We briefly present the motivation for studying the processes mediated by the QCD pomeron at high energy e+e- colliders. We describe the behaviour of the cross-section for the reaction gamma gamma to J/psi J/psi obtained from the BFKL equation with dominant non-leading corrections. We give the predictions for the rates of anti-tagged e+e- to e+e- J/psi J/psi events in TESLA and conclude that such reactions may be excellent probes of the hard pomeron.

hep-ph↗

arXiv1999

Probing the QCD pomeron in doubly tagged e^+ e^- collisions

We calculate the total cross-section for $γ^* γ^*$ collisions and for the process $e^+ e^- \to e^+ e^- + hadrons$ with two tagged leptons assuming dominance of the QCD pomeron exchange. We solve the BFKL equation including the dominant subleading effects generated by the consistency constraint which restricts the available phase-space of the emitted gluons to the region inwhich the virtuality of the exchanged gluons is dominated by their transverse momentum squared. Estimate of the possible soft pomeron contribution to the $γ^* γ^*$ cross-section is also presented. At very high CM energies $W$ the calculated total $γ^* γ^*$ cross-section exhibits effective power-law $(W^2)^λ$ behaviour with $λ\sim 0.3$. We confront our results with the recent measurements at LEP and give predictions for the energies which can be accessible at TESLA and at other future linear $e^+ e^-$ colliders.

hep-ph↗

arXiv1999

The QCD pomeron in e+e- collisions

The contribution of the QCD pomeron to the processes: e+e- to e+e- J/psi J/psi and e+ e- to e+ e- hadrons (with tagged electrons) is discussed. We focus on reactions which occur via photon-photon collisions, with virtual photons coming from the Weizsaecker-Wiliams spectrum of the electrons. We stress the importance of the non-leading corrections to the BFKL equation and take into account dominant non-leading effects which come from the requirement that the virtuality of the exchanged gluons along the gluon ladder is controlled by their transverse momentum squared. The γ* γ* cross-sections are found to increase with increasing γ* γ* CM energy W as (W^2)^{λ_P} while the cross-section for γγto J/psi J/psi is found to increase as (W^2)^{2λ_P}. The parameter λ_P is slowly varying with energy W and takes the values lambda_P \sim 0.23 - 0.35 depending on the process. We also analyze the contribution of the soft pomeron for the total γ* γ* cross-section. We compare results of our calculations to the recent data from LEP.

hep-ph↗

arXiv1998

Spin effects in heavy quarkonia

A model based on a nonrelativistic potential supplemented by spin dependent terms of the Breit-Fermi type is described. This model reproduces the known masses of the $\bar{b}b$ quarkonia within 1MeV and the known masses of the $\bar{c}c$ quarkonia within 5MeV. Many predictions are made, some of them, e.g. for the fine splittings of the high $L$ states of the $\bar{b}b$ quarkonia and of the mass spectrum of the $\bar{b}c$ quarkonia, significantly different from previous predictions made by other authors.

hep-ph↗

arXiv1998

Possible probe of the QCD odderon singularity through the quasidiffractive eta_c production in gamma-gamma collisions

The reactions gamma-gamma to eta_c eta_c and gamma gamma to eta_c + X are discussed within the three gluon exchange model. We give predictions for the differential cross-sections and discuss feasibility of measuring these processes at LEP2 and TESLA. The total cross-sections were estimated to be approximately equal to 40 fb and 120 fb for gamma-gamma to eta_c eta_c and gamma-gamma to eta_c + X respectively assuming exchange of elementary gluons that corresponds to the odderon with intercept equal to unity. These values can be enhanced by a factor equal to 1.9 and 2.1 for LEP2 and TESLA energies if the odderon intercept is equal to 1.07. The estimate of cross-sections sigma(e^+ e^- to e^+ e^- eta_c eta_c) and sigma (e^+ e^- to e^+ e^- eta_c + X) for untagged e^+ and e^- is also given.

hep-ph↗

arXiv1997

Exclusive $η_c$ photo- and electroproduction at HERA as a possible probe of the odderon singularity in QCD

Theory and phenomenology of the eta_c photo- and electroproduction is developed from the point of view of probing the odderon singularity in QCD which corresponds to the three gluon exchange mechanism. This mechanism leads to the cross-sections which are independent of W^2 for the exchange of three non-interacting gluons or exhibit increase with increasing W^2 (or 1/x) for the odderon intercept above unity. The η_c electroproduction in the three gluon exchange mechanism is shown to be entirely controlled by the transversely polarised virtual photons. The magnitude of the eta_c photoproduction cross-section is estimated to be around 11-45pb. The t-dependence of the differential cross-section is also discussed.

hep-ph↗

arXiv1995

NONRELATIVISTIC MODEL FOR $b\OVERLINE{b}$ QUARKONIA

Experimental data for $b\bar{b}$ quarkonia have been compared with the predictions of a variety of nonrelativistic quark models. It is found that a potential $a\sqrt{r} - b/r +$ const gives good agreement, while many others do not. Some implications of this observation are discussed.

hep-ph↗