Tomasz Stebel

Quantitative study of geometrical scaling in deep inelastic scattering at HERA

A bstractWe propose a method to assess the quality of geometrical scaling in Deep Inelastic Scattering and apply it to the combined HERA data on γ*p cross-section. Using two different approaches based on Bjorken x binning and binning in γ*p scattering energy W, we show that geometrical scaling in variable τ ~ Q2xλ works well up to Bjorken x’s 0.1. The corresponding value of exponent λ is 0.32-0.34.

Soft gluon resummation for associated \( \mathrm{t}\overline{\mathrm{t}}\mathrm{H} \) production at the LHC

We perform resummation of soft gluon corrections to the total cross section for the process pp! t tH. The resummation is carried out at next-to-leading-logarithmic (NLL) accuracy using the Mellin space technique, extending its application to the class of 2! 3 processes. We present an analytical result for the soft anomalous dimension for a hadronic production of two coloured massive particles in association with a colour singlet. We discuss the impact of resummation on the numerical prediction for the associated Higgs boson production with top quarks at the LHC.A bstractWe perform resummation of soft gluon corrections to the total cross section for the process pp → tt¯H

Quantitative study of different forms of geometrical scaling in deep inelastic scattering at HERA

t\overline{t}H

Twist expansion of forward Drell-Yan process

. The resummation is carried out at next-to-leading-logarithmic (NLL) accuracy using the Mellin space technique, extending its application to the class of 2 → 3 processes. We present an analytical result for the soft anomalous dimension for a hadronic production of two coloured massive particles in association with a colour singlet. We discuss the impact of resummation on the numerical prediction for the associated Higgs boson production with top quarks at the LHC.

Soft gluon resummation at fixed invariant mass for associated

The quantum telescope is a recent idea aimed at beating the diffraction limit of spaceborne telescopes and possibly other distant target imaging systems. There is no agreement yet on the best setup of such devices, but some configurations have already been proposed. In this Letter we characterize the predicted performance of quantum telescopes and their possible limitations. Our extensive simulations confirm that the presented model of such instruments is feasible and the device can provide considerable gains in the angular resolution of imaging in the UV, optical, and infrared bands. We argue that it is generally possible to construct and manufacture such instruments using the latest or soon to be available technology. We refer to the latest literature to discuss the feasibility of the proposed QT system design.

t\bar{t}H

A bstractWe use recently proposed method of ratios to assess the quality of geometrical scaling in deep inelastic scattering for different forms of the saturation scale. We consider original form of geometrical scaling (motivated by the Balitski-Kovchegov (BK) equation with fixed coupling) studied in more detail in our previous paper, and four new hypotheses: phenomenologically motivated case with Q2 dependent exponent λ that governs small x dependence of the saturation scale, two versions of scaling (running coupling 1 and 2) that follow from the BK equation with running coupling, and diffusive scaling suggested by the QCD evolution equation beyond mean field approximation. It turns out that more sophisticated scenarios: running coupling scaling and diffusive scaling are disfavored by the combined HERA data on e+p deep inelastic structure function F2.

production at the LHC

A bstractThe forward Drell-Yan process at the LHC probes the proton structure at a very small Bjorken-x and moderate hard scales. In this kinematical domain higher twist effects may be significant and introduce sizeable corrections to the standard leading twist description. We study the forward Drell-Yan process beyond the leading twist approximation within the color dipole model framework that incorporates multiple scattering effects. We derive the Mellin representation of the forward Drell-Yan impact factors for fully differential cross-sections. These results combined with the color dipole cross-section of the saturation model are used to perform the twist expansion of the Drell-Yan structure functions at arbitrary transverse momentum qT of the Drell-Yan pair and also of the structure functions integrated over qT. We also investigate the Lam-Tung relation, find that it is broken at twist 4 and provide explicit estimates for the breaking term.

Soft gluon resummation for the associated production of a top quark pair with a W boson at the LHC

We present a twist expansion of differential cross-sections of the forward Drell-Yan process at the high energies. The expansion of all invariant form-factors is performed assuming GBW saturation model and the saturation scale plays the role of the hadronic scale of OPE. Some expilicit predictions for LHC experiments are given. It is shown also how the Lam-Tung relation is broken at twist 4 what provides a sensitive probe for searching of higher twists.