176,828 research outputs found
Correlations between SIDIS Azimuthal Asymmetries in Target and Current Fragmentation Regions
No full textWe shortly describe the leading twist formalism for spin and
transverse-momentum dependent fracture functions recently developed and present results for the production of spinless hadrons in the target fragmentation region (TFR) of SIDIS. In this case not all fracture functions can be accessed and only a Sivers-like single spin azimuthal asymmetry shows up at LO cross-section. Then, we show that the process of double hadron production in polarized SIDIS—with one spinless hadron produced in the current fragmentation region (CFR) and another in the TFR—would provide access to all 16 leading twist fracture functions. Some particular cases are presented
SIDIS in the target fragmentation region: Polarized and transverse-momentum dependent fracture functions
No full textTransversity and Collins functions from SIDIS and e+ e- data
No full textA global analysis of the experimental data on azimuthal asymmetries in semi-inclusive deep inelastic scattering (SIDIS), from the HERMES and COMPASS Collaborations, and in e+e- --> h1 h2 X processes, from the BELLE Collaboration, is performed. It results in the extraction of the Collins fragmentation function and, for the first time, of the transversity distribution function for u and d quarks. These turn out to have opposite signs and to be sizably smaller than their positivity bounds. Predictions for the azimuthal asymmetry A_{UT}^{sin(phi_h + phi_S)}, as will soon be measured at JLab and COMPASS operating on a transversely polarized proton target, are then presente
Update on transversity and Collins functions from SIDIS and e+ e- data
No full textWe present an update of a previous global analysis of the experimental data on azimuthal asymmetries in semi-inclusive deep inelastic scattering (SIDIS), from the HERMES and COMPASS Collaborations, and ill e(+)e(-) --> h(1)h(2)X processes, front the Belle Collaboration. Compared to the first extraction, a more precise determination of the Collins fragmentation function and the transversity distribution function for u and d quarks is obtained
Extracting the Sivers function from polarized semi-inclusive deep inelastic scattering data and making predictions
No full textThe most recent data on the weighted transverse single spin asymmetry A(UT) sin(phi(h) - phi(S)) from HERMES and COMPASS Collaborations are analyzed within the 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(phi(h)-phi(S)) asymmetries at JLab are given; suggestions for further measurements at COMPASS, with a transversely polarized hydrogen target and selecting favorable kinematical ranges, are discussed. Predictions are also presented for single spin asymmetries in Drell-Yan processes at the Relativistic Heavy Ion Collider and the Facility for Antiproton and Ion Research at GSI-Darmstadt
Role of Cahn and Sivers effects in deep inelastic scattering
No full textThe role of intrinsic k(perp) in inclusive and semi-inclusive Deep Inelastic Scattering processes (lp -> lhX) 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(perpendicular to) both in quark distribution and fragmentation functions. The resulting picture is applied to the description of the weighted single spin asymmetry A(UT)(pi)(sin(phi)-phi(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 p(uparrow) p -> pi X processes; the two sets of functions are not inconsistent. The extracted Sivers functions give predictions for the COMPASS measurement of A(UT)(pi)(sin(phi)-phi(S)) in agreement with recent preliminary data, while their contribution to HERMES A(UL)(pi) sin(phi) is computed and found to be small. Predictions for A(UT)(K)(sin(phi)-phi(S)) for kaon production at HERMES are also given
New preliminary results on the Transversity distribution and the Collins Fragmentation Functions
No full textFirst results from a new global analysis of the experimental data on azimuthal asymmetries in SIDIS, from HERMES and COMPASS collaborations, and in e(+)e(-) -> h(1)h(2)X processes, from the Belle collaboration, are presented. The new data allow for a more precise determination of the Collins fragmentation function and of the transversity distribution function for u and d quarks, in comparison with the results of our previous analysis. Estimates for the single spin asymmetry A(UT) (sin(phi(h)+phi(S))) at JLab and COMPASS, operating on a transversely polarized proton target, are given
Transversity and Collins functions from SIDIS and e(+)e(-) data
No full textA global analysis of the experimental data on azimuthal asymmetries in semi-inclusive deep inelastic scattering (SIDIS), from the HERMES and COMPASS Collaborations, and in e(+)e(-) --> h(1) h(2) X processes, from the Belle Collaboration, is performed. It results in the extraction of the Collins fragmentation function and, for the first time, of the transversity distribution function for u and d quarks. These turn out to have opposite signs and to be sizably smaller than their positivity bounds. Predictions for the azimuthal asymmetry A(UT)(S)(sin(phi)+phi(h)), as will soon be measured at JLab and COMPASS operating on a transversely polarized proton target, are then presented
- …
