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L. Szymanowski

Publications and source records attributed to L. Szymanowski.

At least 199 records · Page 11Linked to original sources
arXiv2006

On exotic hybrid meson production in gamma* gamma collisions

We present a theoretical study of exotic hybrid meson (JPC=1-+) production in photon-photon collisions where one of the photons is deeply virtual, including twist 2 and twist 3 contributions. We calculate the cross section of this process which turns out to be large enough to imply sizeable counting rates in the present high luminosity electron-positron colliders. We emphasize theimportance of the pi eta decay channel for the detection of the hybrid meson candidate pi_1(1400) and calculate the cross section and the angular distribution for pi eta pair production in the unpolarized case. This angular distribution is a useful tool for disentangling the hybrid meson signal from the background. Finally, we calculate the single spin asymmetry associated with one initial longitudinally polarized lepton.

hep-ph↗
arXiv2005

Hard Pomeron in exclusive meson production at ILC

We calculate the exclusive process gamma* gamma* ->rho rho at high energy. The Born order estimate and the leading (LLA) and next to leading order (NLLA) BFKL resummation effects show the feasibility of experimental detection in a quite large range of Q2 values at future high energy e+e- linear colliders.

hep-ph↗
arXiv2005

The QCD analysis of hadron-antihadron -> gamma^* gamma in the forward region and related processes

A QCD analysis of the reactions A B -> gamma^* gamma and gamma^* gamma -> A B in the forward region shows that they can be factorized in a way which is quite similar to the frameword developped for deeply virtual Compton scattering. The generalized parton distributions (GPDs) related to this latter process being replaced by new non perturbative hadronic matrix elements, the transition distribution amplitudes (TDAs).

hep-ph↗
arXiv2005

A QCD analysis of \bar p N -> gamma^* pi and \bar p N -> gamma^* gamma. Where is the pion in the proton ?

We study the scaling regime of nucleon-anti-nucleon annihilation into a deeply virtual photon and a photon or meson, \bar p N -> gamma ^* pi, \bar p N -> gamma ^* gamma, in the forward direction. The leading twist amplitude factorizes into an antiproton distribution amplitude, a short-distance matrix element and a long-distance dominated transition distribution amplitude (TDA) which describes the nucleon to meson or photon transition. The impact representation of this TDA maps out the transverse locations of the small size core and the meson or photon cloud inside the proton.

hep-ph↗
arXiv2005

Hard production of exotic hybrid mesons

Exotic hybrid mesons H, with quantum numbers J^{PC}= 1^{- +} may be copiously produced in the hard exclusive processes gamma^*(Q^2) gamma -> H and gamma^*(Q^2) P(p) -> H P(p') because they have a leading twist distribution amplitude with a sizable coupling constant f_H, which may be estimated through QCD sum rules. The reaction rates scale in the same way as the corresponding rates for usual mesons.

hep-ph↗
arXiv2005

Born order study of gamma*gamma* -> rho rho at very high energy

We calculate the cross-section for the diffractive exclusive process gamma*_L (Q_1^2) gamma*_L(Q_2^2) -> rho^0_L rho^0_L, in view of its study in the future high energy e+e- linear collider. The Born order approximation of the amplitude is completely calculable in the hard region Q_1, Q_2 >> Lambda_QCD. The resulting cross-section is large enough for this process to be measurable with foreseen luminosity and energy, for Q_1 and Q_2 in the range of a few GeV.

hep-ph↗
arXiv2005

Double diffractive rho-production in gamma^* gamma^* collisions

We present a first estimate of the cross-section for the exclusive process gamma^*_L (Q_1^2) gamma^*_L(Q_2^2) -> rho^0_L rho^0_L, which will be studied in the future high energy e^+ e^- linear collider. As a first step, we calculate the Born order approximation of the amplitude for longitudinally polarized virtual photons and mesons, in the kinematical region s >> -t, Q_1^2, Q_2^2. This process is completely calculable in the hard region Q_1^2, Q_2^2 >> Lambda^2_{QCD}. We perform most of the steps in an analytical way. The resulting cross-section turns out to be large enough for this process to be measurable with foreseen luminosity and energy, for Q_1^2 and Q_2^2 in the range of a few GeV^2.

hep-ph↗
arXiv2005

Hadron annihilation into two photons and backward dVCS in the scaling regime of QCD

We study the scaling regime of hadron-(anti)-hadron annihilation into a deeply virtual photon and a real photon, H anti-H -> gamma^* gamma, and deep backward virtual Compton scattering, gamma^* H -> H gamma. We advocate that there is a kinematical region where the scattering amplitude factorizes into a short-distance matrix element and a long-distance dominated object: a transition distribution amplitude which describes the hadron to photon transition.

hep-ph↗
arXiv2005

On BLM scale fixing in exclusive processes

We discuss the BLM scale fixing procedure in exclusive electroproduction processes in the Bjorken regime. We show that in the case of vector meson production the usual way to aplly the BLM method fails due to singularities present in equations fixing the BLM scale. We argue that the BLM scale should be extracted from the squared amplitudes which are directly related to observables.

hep-ph↗
arXiv2005

$γ^* γ^* \to ρρ$ at very high energy

The next generation of $e^+e^-$-colliders will offer a possibility of clean testing of QCD dynamics in the Regge limit. Recent progress in the theoretical description of exclusive processes permits for many of them a consistent use of the perturbative QCD methods. We advocate that the exclusive diffractive production of two $ρ$ mesons from virtual photons at very high energies should be measurable at the future linear collider (LC).

hep-ph↗
arXiv2005

$πη$ pair hard electroproduction and exotic hybrid mesons

We show that hard electroproduction is a promising way to study exotic hybrid mesons, in particular through the hybrid decay channel $H \to πη$. We discuss the $πη$ generalized distribution amplitude, calculate the production amplitude and propose a forward-backward asymmetry as a signal for the hybrid meson production.

hep-ph↗
arXiv2005

Exclusive production of pentaquarks in the scaling regime

We investigate two exclusive reactions with a Theta+ pentaquark in the final state: electroproduction of a K meson on the nucleon, and K+ scattering on a neutron target producing a lepton pair. These reactions offer unique opportunities to investigate the structure of pentaquark baryons at parton level. We discuss the generalized parton distributions for the N --> Theta+ transition and give the leading order amplitude for these processes in the Bjorken regime.

hep-ph↗
arXiv2004

Hard exclusive production of a vector meson

The processes of a light neutral vector meson, V=ρ^0, ω, ϕ, electroproduction and a heavy quarkonium, V=J/Ψ, Υ, photoproduction are studied in the framework of QCD factorization. We derive a complete set of hard-scattering amplitudes which describe these processes at next-to-leading order (NLO).

hep-ph↗
arXiv2004

Exotic hybrid mesons in hard electroproduction

We estimate the sizeable cross section for deep exclusive electroproduction of an exotic $J^{PC}=1^{-+}$ hybrid meson in the Bjorken regime. The production amplitude scales like the one for usual meson electroproduction, i.e. as $1/Q^2$. This is due to the non-vanishing leading twist distribution amplitude for the hybrid meson, which may be normalized thanks to its relation to the energy momentum tensor and to the QCD sum rules technique. The hard amplitude is considered up to next-to-leading order in $α_{S}$ and we explore the consequences of fixing the renormalization scale ambiguity through the BLM procedure. We study the particular case where the hybrid meson decays through a $πη$ meson pair. We discuss the $πη$ generalized distribution amplitude and then calculate the production amplitude for this process. We propose a forward-backward asymmetry in the production of $π$ and $η$ mesons as a signal for the hybrid meson production. We briefly comment on hybrid electroproduction at very high energy, in the diffractive limit where a QCD Odderon exchange mechanism should dominate. The conclusion of our study is that hard electroproduction is a promissing way to study exotic hybrid mesons, in particular at JLAB, HERA (HERMES) or CERN (Compass).

hep-ph↗
arXiv2004

Hard Exclusive QCD Processes at the Linear Collider

The next generation of $e^+e^-$ colliders will offer a possibility of clean testing of QCD dynamics. Recent progress in the theoretical description of exclusive processes permits for many of them a consistent use of the perturbative QCD methods. We find that already on the basis of Born approximation, the exclusive diffractive production of two $ρ$ mesons from virtual photons at very high energies should be measurable at the linear collider (LC).

hep-ph↗
arXiv2004

Quasi-Hermiticity in infinite-dimensional Hilbert spaces

In infinite-dimensional Hilbert spaces, the application of the concept of quasi-Hermiticity to the description of non-Hermitian Hamiltonians with real spectra may lead to problems related to the definition of the metric operator. We discuss these problems by examining some examples taken from the recent literature and propose a formulation that is free of these difficulties.

quant-ph↗