Article

# Effects of transversity in deep-inelastic scattering by polarized protons

[more]
Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
(Impact Factor: 6.13). 09/2010; 693(1):11-16. DOI: 10.1016/j.physletb.2010.08.012

ABSTRACT

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The dependence of the cross section on the azimuthal angles of the target polarization (ϕS) and the produced hadron (ϕ) is found to have a substantial sin(ϕ+ϕS) modulation for the production of π+, π− and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For π0 and K− production the amplitude of this Fourier component is consistent with zero.

### Full-text

Available from: Vahagn Gharibyan
• Source
• "These Transverse Momentum Dependent distribution and fragmentation functions (collectively here called " TMDs " ) can be accessed in several types of processes, one of the most important is single particle hadron production in Semi-Inclusive Deep Inelastic Scattering (SIDIS) of leptons on nucleons. A significant amount of data on spin-azimuthal distributions of hadrons in SIDIS, providing access to TMDs has been accumulated in recent years by several collaborations, including HERMES, COMPASS and Halls A,B and C at JLab [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]. At least an order of magnitude more data is expected in coming years of running of JLab 12 [1]. "
##### Article: Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
[Hide abstract]
ABSTRACT: In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q 2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
Full-text · Article · Sep 2014 · Journal of High Energy Physics
• Source
##### Article: Azimuthal asymmetries of charged hadrons produced by high-energy muons scattered off longitudinally polarised deuterons
[Hide abstract]
ABSTRACT: Azimuthal asymmetries in semi-inclusive production of positive (h +) and negative hadrons (h −) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed in several terms according to their expected modulation in the azimuthal angle φ of the outgoing hadron. Each term receives contributions from one or several spin and transverse-momentum-dependent parton distribution and fragmentation functions. The amplitudes of all φ-modulation terms of the hadron asymmetries integrated over the kinematic variables are found to be consistent with zero within statistical errors, while the constant terms are nonzero and equal for h + and h − within the statistical errors. The dependencies of the φ-modulated terms versus the Bjorken momentum fraction x, the hadron fractional momentum z, and the hadron transverse momentum phTp_{h}^{T} were studied. The x dependence of the constant terms for both positive and negative hadrons is in agreement with the longitudinal double-spin hadron asymmetries, measured in semi-inclusive deep-inelastic scattering. The x dependence of the sin φ-modulation term is less pronounced than that in the corresponding HERMES data. All other dependencies of the φ-modulation amplitudes are consistent with zero within the statistical errors.
Full-text · Article · Jul 2010 · European Physical Journal C
• Source
##### Article: The polarized TMDs in the covariant parton model approach
[Hide abstract]
ABSTRACT: We derive relations between polarized transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDF $g_{1}^{q}(x)$ as input we predict the $x$- and $\mathbf{p}_{T}$-dependence of all polarized twist-2 naively time-reversal even (T-even) TMDs.
Full-text · Article · Jan 2011 · Journal of Physics Conference Series