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We discuss a scenario in which the diphoton enhancement at Mγγ=750 GeV, observed by the ATLAS and CMS collaborations, is a neutral technipion π0. We consider two distinct minimal models for the dynamical electroweak symmetry breaking. In a first one, two-flavor vectorlike technicolor (VTC) model, we assume that the two-photon fusion is a dominant production mechanism. We include γγ→π0 and producti
The Drell-Yan (DY) process of dilepton pair production off nuclei is not affected by final state interactions, energy loss, or absorption. A detailed phenomenological study of this process is thus convenient for investigation of the onset of initial-state effects in proton-nucleus (pA) collisions. In this paper, we present a comprehensive analysis of the DY process in pA interactions at RHIC and L
We study nuclear effects in production of Drell-Yan pairs and direct photons in proton-nucleus collisions. For the first time, these effects are studied within the color dipole approach using the Green function formalism which naturally incorporates the color transparency and quantum coherence effects. The corresponding numerical results for the nuclear modification factor are compared with availa
Using the color dipole formalism we study production of Drell-Yan (DY) pairs in proton-nucleus interactions in the kinematic region corresponding to LHC experiments. Lepton pairs produced in a hard scattering are not accompanied with any final state interactions leading to either energy loss or absorption. Consequently, dileptons may serve as more efficient and cleaner probes for the onset of nucl
We present a novel Monte Carlo implementation of dynamic color screening via multiple exchanges of semisoft gluons as a basic QCD mechanism to understand diffractive electron-proton scattering at the HERA collider. Based on the kinematics of individual events in the standard QCD description of deep inelastic scattering at the parton level, which at low x is dominantly gluon initiated, the probabil
The Drell-Yan massive dilepton production in hadron-hadron collisions provides a unique tool, complementary to Deep Inelastic Scattering, for improving our understanding of hadronic substructure and in particular for testing parton distributions. We will consider measurements of the differential and double-differential Drell-Yan cross sections from FNAL Tevatron up to CERN LHC energies and they wi
The soft color interaction model (SCI) as an add-on to standard perturbative QCD describes diffractive processes by allowing for additional soft color-octet exchanges below the conventional threshold for parton showering. We discuss how diffractive and inclusive event samples for diffractive hard processes can be obtained from a Monte Carlo in a unified way for pp → p[W± +X]p as an example, and di
We study the polarized Bjorken sum rule (BSR) at low momentum transfers in the range 0.223LO expression for the coefficient function CBj(αs) in the framework of the common QCD perturbation theory (PT) and the singularity-free analytic perturbation theory (APT). The analysis of the PT series for CBj(αs) gives a hint to its asymptotic nature manifesting itself in the region Q
We present a study of central exclusive production of W+W - pairs in proton-proton collisions at the LHC. We compare the contribution of the γγ → W+W- mechanism with a new mechanism of exclusive diffractive production through the gg → W+W- subprocess with intermediate virtual Higgs boson and quark box diagrams. The amplitude for the latter process is expressed in terms of the off-diagonal unintegr
We discuss single diffractive gauge bosons (γ*, W±, Z) production in proton-proton collisions at LHC energy (14 TeV) in the framework of the color dipole approach. The calculations are performed for gauge bosons produced at forward rapidities. The diffractive cross section is predicted as a function of fractional momentum and invariant mass of the lepton pair. We found a dramatic breakdown of the
We consider the central exclusive production of qq̄ pairs and Higgs boson in proton-proton collisions at LHC. The amplitude for the process is derived within the k -factorization approach and considered in different kinematical asymptotics, in particular, in the important high quark transverse momenta and massless quark limits. Quark helicity and spin-projection amplitudes in two different frames
Diffractive hard scattering is interpreted as the effect of soft gluon exchanges between the emerging energetic quarks and the nucleon's color field, resulting in an overall color singlet exchange. Summing multiple gluon exchanges to all orders leads to exponentiation and an amplitude in analytic form. Numerical evaluation reproduces the precise HERA data and gives new insights on the density of g
Top quark pairs production and decay are considered in the framework of the smeared-mass unstable particles model. The results are in good agreement with the previous ones in the literature. Suggested approach significantly simplifies calculations compared to the standard perturbative one.
We consider exclusive double diffractive production of polarised axial-vector χc(1+) and tensor χc(2+) charmonia in proton-(anti)proton collisions at Tevatron energy. The corresponding amplitudes for these processes are derived within the kt-factorisation approach. Contributions from different polarisation states of axial-vector and tensor charmonia are quantified. Corresponding experimental conse
We consider a measurement of exclusive production of scalar Χc(0++) meson in the proton-proton collisions at LHC and RHIC and in the proton-antiproton collisions at the Tevatron via Χc0→π+π- decay. The corresponding amplitude for exclusive double-diffractive Χc0 meson production was obtained within the kt-factorization approach including virtualities of active gluons and the corresponding cross se
We consider exclusive double diffractive production of polarised axial-vector χ c(1 +) and tensor χ c(2 +) charmonia in proton-(anti)proton collisions at Tevatron energy. The corresponding amplitudes for these processes are derived within the k t-factorisation approach. Contributions from different polarisation states of axial-vector and tensor charmonia are quantified. Corresponding experimental
Near-threshold production of boson pairs is considered within the framework of the model of unstable particles with smeared mass. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations.
We discuss exclusive elastic double diffractive axial-vector χc(1+) and tensor χc(2+) mesons production for different meson polarizations in proton-(anti)proton collisions at the Tevatron energy. The amplitude for the process is derived within the kt-factorization approach using unintegrated gluon distributions. Differential cross sections for different χc polarizations are calculated. Angular dis
We calculate the cross-section of the near-threshold off-shell ZZZ and ZW+W- production at the International Linear Collider taking into account their instability and the principal part of next-to-leading order corrections. The calculations are performed in the framework of the model of unstable particles with smeared mass-shell. We show that the contribution of the finite Z/W and H widths (their
We present a new model where hard diffraction is an effect of soft gluon rescattering between partons emerging from the hard interaction and the color field of the proton. A resummation to all orders of multiple gluon exchanges leads to an overall color singlet exchange amplitude which reproduces the precise HERA data on diffractive deep inelastic scattering.
