Quark induced excitations of the instanton liquid

The selfconsistent approach to the quark interactions in the instanton liquid is developed within the tadpole approximation calculating the basic functional integral. The effective Lagrangian obtained includes colourless scalar field interacting with quarks. The origin of this dynamical field as an interaction carrier in soft momentum region is discussed.Comment: 17 pages, 1 figure ps.file. Slightly revised improved versio

Double heavy meson production through double parton scattering in hadronic collisions

It is shown that the contribution from double parton scattering to the inclusive double heavy meson yield is quite comparable with the usually considered mechanism of their production at the LHC energy. For some pairs of heavy flavored quarks in the final state the double parton scattering will be a dominant mode of their production.Comment: 5 pages, version accepted in Phys. Lett. B, discussion extended, references adde

Magnetic properties of thin Ni films measured by a dc SQUID-based magnetic microscope

We have applied a scanning HTS (high-temperature superconductor) de SQUID (superconducting quantum interference device) -based magnetic microscope to study the magnetic properties of Au/Ni/Si(100) films in the thickness range from 8 to 200 Angstrom at T = 77 K. A one-domain structure with in-plane orientation of the magnetic moment was found for film thicknesses exceeding 26 Angstrom. A drastic decrease of the magnetization of the film was detected when the thickness is less than 26 Angstrom

Double parton correlations versus factorized distributions

Using the generalized Lipatov-Altarelli-Parisi-Dokshitzer equations for the two-parton distribution functions we show numerically that the dynamical correlations contribute to these functions quite a lot in comparison with the factorized components. At the scale of CDF hard process ($\sim 5$ GeV) this contribution to the double gluon-gluon distribution is nearly 10% and increases right up to 30% at the LHC scale ($\sim 100$ GeV) for the longitudinal momentum fractions $x \leq 0.1$ accessible to these measurements. For the finite longitudinal momentum fractions $x \sim 0.2 \div 0.4$ the correlations are large right up to 90% in accordance with the predicted QCD asymptotic behaviour.Comment: 10 pages, 1 figur

Simple Mechanism of Softening Structure Functions at Low Transverse Momentum Region

The relevance of the dipole configurations of quarks in forming nucleus structure functions is discussed. It is shown that a radiation generated by dipole configurations while moving relativistically along their axises is described by distributions which are finite and infrared stable in low transverse momentum region. It is argued that there is an exponential transition to the perturbative regime of large transverse momenta and its power is defined by the distance between the dipole charges in its rest frame $m^{-1}_\pi$.Comment: 8 page

Partonic energy loss in ultrarelativistic heavy ion collisions: jet suppression versus jet fragmentation softening

We discuss the modification of a jet fragmentation function due to medium-induced partonic energy loss in context of leading particle observables in ultrarelativistic nucleus-nucleus interactions. We also analyze the relation between in-medium softening jet fragmentation function and suppression of the jet rates due to energy loss outside the jet cone. The predicted anti-correlation between two effects allows to probe a fraction of partonic energy loss carried out of the jet cone and truly lost to the jet.Comment: LaTeX, 12 pages including 2 eps-figure

Pt-imbalance in dimuon+jet production as a signal of partonic energy loss in heavy ion collisions at LHC

We consider a hard jet production tagged by a muon pair in ultrarelativistic heavy ion collisions. The process cross section is calculated by the CompHEP Monte-Carlo generator taking into account full gamma*/Z interference pattern at LHC energies. We have found that reasonable statistics, ~1000 events per 1 month of LHC run with lead beams, can be expected for realistic geometrical acceptance and kinematic cuts. The transverse momentum imbalance due to interactions of jet partons in the medium is evaluated for mu+mu-pair+jet correlation, as well as for the correlation between mu+mu- pair and a leading particle in a jet. Theoretical and experimental uncertainties of these observables are discussed.Comment: 17 pages in LaTeX including 5 eps-figure

Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)

HYDJET++ is a Monte-Carlo event generator for simulation of relativistic heavy ion AA collisions considered as a superposition of the soft, hydro-type state and the hard state resulting from multi-parton fragmentation. This model is the development and continuation of HYDJET event generator (Lokhtin & Snigirev, 2006, EPJC, 45, 211). The main program is written in the object-oriented C++ language under the ROOT environment. The hard part of HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is included in the generator structure as a separate directory. The soft part of HYDJET++ event is the "thermal" hadronic state generated on the chemical and thermal freeze-out hypersurfaces obtained from the parameterization of relativistic hydrodynamics with preset freeze-out conditions. It includes the longitudinal, radial and elliptic flow effects and the decays of hadronic resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is adapted to HYDJET++. It is designed for studying the multi-particle production in a wide energy range of heavy ion experimental facilities: from FAIR and NICA to RHIC and LHC.Comment: 44 pages including 6 figures as EPS-files; prepared using LaTeX package for publication in Computer Physics Communication

Same-sign W pair production as a probe of double parton scattering at the LHC

We study the production of same-sign W boson pairs at the LHC in double parton interactions. Compared with simple factorised double parton distributions (dPDFs), we show that the recently developed dPDFs, GS09, lead to non-trivial kinematic correlations between the W bosons. A numerical study of the prospects for observing this process using same-sign dilepton signatures, including same-sign WWjj, di-boson and heavy flavour backgrounds, at 14 TeV centre-of-mass energy is then performed. It is shown that a small excess of same-sign dilepton events from double parton scattering over a background dominated by single scattering WZ(gamma*) production could be observed at the LHC.Comment: 14 pages, 8 figures. Added references, slight changes in the text