arXiv subjects

A. Kotzinian

Publications and source records attributed to A. Kotzinian.

30 records · Page 2Linked to original sources

arXiv2005

Extracting the Sivers function from polarized SIDIS data and making predictions

The most recent data on the weighted transverse single spin asymmetry $A_{UT}^{\sin(ϕ_h-ϕ_S)}$ from HERMES and COMPASS collaborations are analysed within LO parton model with unintegrated parton distribution and fragmentation functions; all transverse motions are taken into account, with exact kinematics, in the elementary interactions. The overall quality of the data is such that, for the first time, a rather well constrained extraction of the Sivers function for $u$ and $d$ quarks is possible and is performed. Comparisons with models are made. Based on the extracted Sivers functions, predictions for $A_{UT}^{\sin(ϕ_h-ϕ_S)}$ asymmetries at JLab are given; suggestions for further measurements at COMPASS, with a transversely polarized hydrogen target and selecting favourable kinematical ranges, are discussed. Predictions are also presented for Single Spin Asymmetries (SSA) in Drell-Yan processes at RHIC and GSI.

hep-ph↗

arXiv2005

Sivers function: SIDIS data, fits and predictions

The most recent data on the weighted transverse single spin asymmetry A_{UT}^{\sin(ϕ_h-ϕ_S)} from HERMES and COMPASS collaborations are analysed within LO parton model; all transverse motions are taken into account. Extraction of the Sivers function for u and d quarks is performed. Based on the extracted Sivers functions, predictions for A_{UT}^{\sin(ϕ_h-ϕ_S)} asymmetries at JLab are given; suggestions for further measurements at COMPASS, with a transversely polarized hydrogen target and selecting favourable kinematical ranges, are discussed. Predictions are also presented for Single Spin Asymmetries (SSA) in Drell-Yan processes at RHIC and GSI.

hep-ph↗

arXiv2005

Comparing extractions of Sivers functions

A comparison is given of the various recently published extractions of the Sivers functions from the HERMES and COMPASS data on single-transverse spin asymmetries in semi-inclusive deeply inelastic scattering.

hep-ph↗

arXiv2005

Including Cahn and Sivers effects into event generators

It is demonstrated that event generators LEPTO and PYTHIA can be modified to describe some azimuthal modulations. The comparisons of results obtained with modified LEPTO with existing data in the current fragmentation region of SIDIS are presented for Cahn and Sivers effects as well as the predictions for the target fragmentation region. The predictions for Sivers effect in the Drell--Yan process obtained with modified PYTHIA are also presented. The concept of hadronization function is discussed.

hep-ph↗

arXiv2005

Understanding the role of Cahn and Sivers effects in Deep Inelastic Scattering

The role of intrinsic $k_\perp$ in semi-inclusive Deep Inelastic Scattering (SIDIS) processes ($l p \to l h X$) is studied with exact kinematics within QCD parton model at leading order; the dependence of the unpolarized cross section on the azimuthal angle between the leptonic and the hadron production planes (Cahn effect) is compared with data and used to estimate the average values of $k_\perp$ both in quark distribution and fragmentation functions. The resulting picture is applied to the description of the weighted single spin asymmetry $A_{UT}^{\sin(ϕ_π- ϕ_S)}$ recently measured by the HERMES collaboration at DESY; this allows to extract parameters for the quark Sivers functions. The extracted Sivers functions give predictions for the COMPASS measurement of $A_{UT}^{\sin(ϕ_π- ϕ_S)}$ in agreement with recent data, while their contribution to HERMES $A_{UL}^{\sinϕ_π}$ is computed and found to be small. Predictions for $A_{UT}^{\sin(ϕ_K - ϕ_S)}$ for kaon production at HERMES are also given.

hep-ph↗

arXiv2005

The role of Cahn and Sivers effects in Deep Inelastic Scattering

The role of intrinsic $\bfk_\perp$ in inclusive and semi-inclusive Deep Inelastic Scattering processes ($\ell p \to \ell h X$) is studied with exact kinematics within QCD parton model at leading order; the dependence of the unpolarized cross section on the azimuthal angle between the leptonic and the hadron production planes (Cahn effect) is compared with data and used to estimate the average values of $k_\perp$ both in quark distribution and fragmentation functions. The resulting picture is applied to the description of the weighted single spin asymmetry $A_{UT}^{\sin(ϕ_π- ϕ_S)}$ recently measured by the HERMES collaboration at DESY; this allows to extract some simple models for the quark Sivers functions. These are compared with the Sivers functions which succeed in describing the data on transverse single spin asymmetries in $\pup p \to πX$ processes; the two sets of functions are not inconsistent. The extracted Sivers functions give predictions for the COMPASS measurement of $A_{UT}^{\sin(ϕ_π- ϕ_S)}$ in agreement with recent preliminary data, while their contribution to HERMES $A_{UL}^{\sinϕ_π}$ is computed and found to be small. Predictions for $A_{UT}^{\sin(ϕ_K - ϕ_S)}$ for kaon production at HERMES are also given.

hep-ph↗

arXiv2004

Comments on Cahn and Sivers effects in SIDIS

The role of intrinsic $k_\perp$ in semi-inclusive Deep Inelastic Scattering (SIDIS) processes ($\ell p \to \ell h X$) is studied within QCD parton model at leading order. The resulting picture is applied to the description of the weighted single spin asymmetry $A_{UL}^{\sinϕ_h}$ measured by HERMES. It is shown that these data could be described by the Sivers mechanism alone. However, the extracted Sivers functions fail to describe the HERMES data on $A_{UT}^{\sin(ϕ_h-ϕ_S)}$.

hep-ph↗

arXiv2001

Physics at the front-end of a neutrino factory: a quantitative appraisal

We present a quantitative appraisal of the physics potential for neutrino experiments at the front-end of a muon storage ring. We estimate the forseeable accuracy in the determination of several interesting observables, and explore the consequences of these measurements. We discuss the extraction of individual quark and antiquark densities from polarized and unpolarized deep-inelastic scattering. In particular we study the implications for the undertanding of the nucleon spin structure. We assess the determination of alpha_s from scaling violation of structure functions, and from sum rules, and the determination of sin^2(theta_W) from elastic nu-e and deep-inelastic nu-p scattering. We then consider the production of charmed hadrons, and the measurement of their absolute branching ratios. We study the polarization of Lambda baryons produced in the current and target fragmentation regions. Finally, we discuss the sensitivity to physics beyond the Standard Model.

hep-ph↗

arXiv1997

Gluon polarization from correlated high-pT hadron pairs in polarized electro-production

We propose to measure the gluon distribution function Delta G(eta) at eta < 0.2 via pseudo jet production in polarized fixed target lepton nucleon scattering at typical lepton beam energies of 200 GeV. The measurement of the spin-asymmetry for the production of correlated charge conjugated hadrons of opposite transverse momentum can be directly related to Delta G(eta) through the photo-gluon fusion process. Wa also present a numerical analysis of the accuracy which can be obtained for different flavors and kinematics of the observed hadron pair.

hep-ph↗

arXiv1997

Gluon Polarization from Correlated High-p_T Hadron Pairs in Polarized l - N Scattering

We propose to access the gluon polarization $ΔG$ by measuring the cross section spin-asymmetry in semi-inclusive polarized lepton -- nucleon scattering. The photon-gluon fusion sub-process will be tagged by detecting high-$p_T$ correlated hadron pairs in the forward hemisphere. Selecting oppositely charged kaon pairs will allow to suppress the background coming from gluon radiation.

hep-ph↗

arXiv1997

Lambda and Lambda-bar Polarization in Lepton Induced Processes

The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. Current and future semi-inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish between various models for the spin transfer mechanisms.

hep-ph↗

arXiv1996

Quark transverse momentum in hard scattering processes

The role of transverse momentum of quarks in semi-inclusive leptoproduction will be discussed. It involves generalized distribution and fragmentation functions which depend on both the longitudinal lightcone momentum fraction of the quarks and on the transverse momentum. Constraints on these functions and relations between them arise as a consequence of the QCD equation of motion for the quark fields, Lorentz invariance and of C, P, and T invariance of the strong interactions. Experimentally one has access to the functions for instance in measurements of azimuthal asymmetries in hard processes.

hep-ph↗