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L. Szymanowski

Publications and source records attributed to L. Szymanowski.

At least 163 records · Page 9Linked to original sources
arXiv2009

Timelike Compton Scattering at LHC

Exclusive photoproduction of dileptons, gamma N ->l+l- N, is and will be measured in ultraperipheralcollisions at hadron colliders. We demonstrate that the timelike deeply virtual Compton scattering (TCS) mechanism gamma q -> l+l- q, where the lepton pair comes from the subprocess gamma q -> gamma* q, dominates in some accessible kinematical regions, thus opening a new way to study generalized parton distributions (GPD) in the nucleon at small skewedness.

hep-ph↗
arXiv2009

Probing photon structure in DVCS on a photon target

The factorization of the amplitude for the deeply virtual Compton scattering (DVCS) process gamma*(Q) gamma -> gamma gamma at high Q2 is demonstrated in two distinct kinematical domains, allowing to define the photon generalized parton distributions and the diphoton generalized distribution amplitudes. Both these quantities exhibit an anomalous scaling behaviour and obey new inhomogeneous QCD evolution equations.

hep-ph↗
arXiv2008

gamma* -> rhoT impact factor with twist three accuracy

We evaluate the impact factor of the transition gamma* -> rhoT taking into account the twist 3 contributions. We show that a gauge invariant expression is obtained with the help of QCD equations of motion. Our results are free of end-point singularities. This opens the way to a consistent treatment of factorization for exclusive processes with a transversally polarized vector meson.

hep-ph↗
arXiv2008

On AdS/QCD correspondence and the partonic picture of deep inelastic scattering

We critically examine the question of scaling of the Deep Inelastic Scattering process in the medium Bjorken x region on a scalar boson in the framework of the AdS/QCD correspondence. To get the right polarization structure of the forward electroproduction amplitude, we show that one needs to add (at least) the scalar to scalar and scalar to vector hadronic amplitudes. This illustrates how the partonic picture may emerge from a simple scenario based on the AdS/QCD correspondence, provided one allows the conformal dimension of the hadronic field to equal 1 and use the concept of "hadron - parton duality" .

hep-ph↗
arXiv2008

Can one measure timelike Compton scattering at LHC ?

Exclusive photoproduction of dileptons, gamma N->e+e-N, is and will be measured in ultraperipheral collisions at hadron colliders, such as the Tevatron, RHIC and the LHC . We demonstrate that the timelike deeply virtual Compton scattering (TCS) mechanism gamma q -> e+e- q where the lepton pair comes from the subprocess gamma q -> gamma* q dominates in some accessible kinematical regions, thus opening a new way to study generalized parton distributions (GPD) in the nucleon. High energy kinematics enables to probe parton distributions at small skewedness. This subprocess interferes at the amplitude level with the pure QED subprocess gamma gamma* -> e+e- where the virtual photon is radiated from the nucleon.

hep-ph↗
arXiv2008

Hard Pomeron-Odderon interference effects in the production of pi^+pi^- pairs in high energy gamma-gamma collisions at the LHC

We estimate the production of two meson pairs in high energy photon photon collisions produced in ultraperipheral collisions at LHC. We show that the study of charge asymmetries may reveal the existence of the perturbative Odderon and discuss the concrete event rates expected at the LHC. Sizable rates and asymmetries are expected in the case of proton-proton collisions and medium values of gamma-gamma energies \sqrt{s_{γγ}} \approx 20GeV. Proton-proton collisions will benefit from a high rate due to a large effective gamma-gamma luminosity and ion-ion collisions with a somewhat lower rate from the possibility to trigger on ultraperipheral collisions and a reduced background from strong interactions.

hep-ph↗
arXiv2008

Two Photon Distribution Amplitudes

The factorization of the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q2 behaviour and obey new inhomogeneous evolution equations.

hep-ph↗
arXiv2008

Diphoton Generalized Distribution Amplitudes

We calculate the leading order diphoton generalized distribution amplitude by calculating the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the gamma gamma generalized distribution amplitude exhibits a characteristic \ln Q^2 behaviour and obeys inhomogeneous evolution equations.

hep-ph↗
arXiv2008

Exclusive photoproduction of lepton pairs at LHC

Exclusive photoproduction of dileptons, gamma p ->l+ l- p, will be measured in ultraperipheral collisions at LHC. The mechanism where the lepton pair comes from a heavy timelike photon radiated from a quark interferes with the pure QED process gamma gamma ->l+ l- As an analog of deeply virtual Compton scattering, this timelike Compton scattering is a way to study generalized parton distributions in the nucleon or the nucleus. High energy kinematics will enable to focus on gluon distributions. Nuclear effects may be scrutinized in heavy ion collisions.

hep-ph↗
arXiv2008

A test of the BFKL resummation at ILC

We consider the exclusive production of rho^0 meson pairs in gamma^*gamma^* scattering in the Regge limit of QCD as a probe of BFKL resummation effects and we show the feasibility of the measurement of this process at the ILC.

hep-ph↗
arXiv2007

Hard exclusive electroproduction of a pion in the backward region

We study the scaling regime of pion electroproduction in the backward region, eN->e'N'pi. We compute the leading-twist amplitude in the kinematical region, where it factorises into a short-distance matrix element and long-distance dominated nucleon Distribution Amplitudes and nucleon to pion Transition Distribution Amplitudes. Using the chiral limit of the latter, we obtain a first estimate of the cross section, which may be experimentally studied at JLab or Hermes.

hep-ph↗
arXiv2007

QCD Factorizations in Exclusive gamma* gamma* -> rho0_L rho0_L

The exclusive process e+ e- -> e+ e-rho0_L rho0_L allows to study various dynamics and factorization properties of perturbative QCD. At moderate energy, we demonstrate how collinear QCD factorization emerges, involving either generalized distribution amplitudes (GDA) or transition distribution amplitudes (TDA). At higher energies, in the Regge limit of QCD, we show that it offers a promising probe of the BFKL resummation effects to be studied at ILC.

hep-ph↗
arXiv2007

Anomalous GPDs in the photon

We consider deeply virtual Compton scattering (DVCS) on a photon target, in the generalized Bjorken limit, at the Born order and in the leading logarithmic approximation. This leads us to the extraction of the photon anomalous generalized parton distributions (GPDs) \cite{url, DVCSphoton}.

hep-ph↗
arXiv2007

Transition Distribution Amplitudes for gamma* gamma collisions

We study the exclusive production of pi-pi and rho-pi in hard gamma* gamma scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for rho-pi and pi-pi production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BaBar).

hep-ph↗
arXiv2007

Production of a pion in association with a high-Q2 dilepton pair in antiproton-proton annihilation at GSI-FAIR

We evaluate the cross section for anti-p p -> l+ l- pi0 in the forward direction and for large lepton pair invariant mass. In this kinematical region, the leading-twist amplitude factorises into a short-distance matrix element, long-distance dominated antiproton Distribution Amplitudes and proton to pion Transition Distribution Amplitudes (TDA). Using a modelling inspired from the chiral limit for these TDAs, we obtain a first estimate of this cross section, thus demonstrating that this process can be measured at GSI-FAIR.

hep-ph↗
arXiv2007

Studying QCD factorizations in exclusive gamma* gamma* -> rho^0_L rho^0_L

The exclusive process e+ e- -> e+ e- rho^0_L rho^0_L allows to study various dynamics and factorization properties of perturbative QCD. At moderate energy, we demonstrate how collinear QCD factorization emerges, involving generalized distribution amplitudes (GDA) and transition distribution amplitudes (TDA). At higher energies, in the Regge limit of QCD, we show that it offers a promising probe of the BFKL resummation effects to be studied at the International Linear Collider (ILC).

hep-ph↗