scholarly journals FINAL-STATE INTERACTIONS AND SINGLE-SPIN ASYMMETRIES IN SEMI-INCLUSIVE DEEP INELASTIC SCATTERING

2003 ◽  
Vol 18 (08) ◽  
pp. 1327-1334 ◽  
Author(s):  
STANLEY J. BRODSKY ◽  
DAE SUNG HWANG ◽  
IVAN SCHMIDT
Keyword(s):  
Spin Asymmetry ◽  
Proton Spin ◽  
Final State ◽  
Complex Phase ◽  
Target Nucleon ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Polarized Target ◽  
Single Spin Asymmetries ◽  
Final State Interactions

Recent measurements from the HERMES and SMC collaborations show a remarkably large azimuthal single-spin asymmetries AUL and AUT of the proton in semi-inclusive pion leptoproduction γ*(q) p → π X. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system leads to single-spin asymmetries in deep inelastic lepton-proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality q2 at fixed xbj. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with [Formula: see text] to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum Lz of the proton's constituents and thus is distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of structure function and fragmentation function, and it is not related to the transversity distribution δq(x,Q) which correlates transversely polarized quarks with the spin of the transversely polarized target nucleon.

SINGLE SPIN ASYMMETRIES FOR LOW ENERGY π±'S AND FOR ρ MESONS AT RHIC ENERGIES

2004 ◽  
Vol 19 (12) ◽  
pp. 897-908
Author(s):  
G. HERRERA ◽  
I. LEÓN-MONZÓN ◽  
J. MARTÍNEZ CASTRO
Keyword(s):  
Spin Asymmetry ◽  
Good Description ◽  
Thomas Precession ◽  
Final State ◽  
Recombination Mechanism ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Two Component ◽  
Production Asymmetry

The production asymmetry of both π and ρ mesons in the reaction p↑p→hX is calculated in a two-component model in which hadrons are produced by a nonperturbative recombination process and by fragmentation of quarks in the final state. Thomas precession in the recombination mechanism seems to be responsible of the single spin asymmetry. We obtain a good description of experimental data. Predictions of single spin asymmetries for ρ production at RHIC energies are presented.

scholarly journals Study of single-spin asymmetries with polarized target at the SPASCHARM experiment at U70 accelerator

2017 ◽  
Vol 798 ◽  
pp. 012096
Author(s):  
V V Abramov ◽  
N A Bazhanov ◽  
N I Belikov ◽  
A A Borisov ◽  
N S Borisov ◽  
...  
Keyword(s):  
Spin Asymmetries ◽  
Single Spin ◽  
Polarized Target ◽  
Single Spin Asymmetries

scholarly journals Proton Quark Helicity Structure via W-Boson Production in PP Collision @ Phenix

2016 ◽  
Vol 40 ◽  
pp. 1660018
Author(s):  
F. Giordano
Keyword(s):  
W Boson ◽  
Light Quark ◽  
Center Of Mass ◽  
Proton Spin ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Quark Spin ◽  
Polarized Proton ◽  
The Status

The spin structure of the proton has been long studied in the past decades, but, while the contributions to the proton spin from valence quarks is by now precisely known, large uncertainties are still affecting our knowledge of the sea quark contributions. The measurement of single-spin asymmetries of the parity violating W production in pp collision allows a (quasi-)model independent access to the flavor-dependent light sea quark contributions. Being maximally parity violating, the [Formula: see text] charge can be directly realted to the quark and antiquark flavor, and in addition, moving from forward to backward rapidities with respect to the polarized proton beam direction it is possible to change the relative contributions of u, d, anti-u, anti-d quarks, thus accessing each light-quark spin alignment with respect to the proton spin. At PHENIX, the W boson produced in pp collision at center of mass energies of about 500 GeV is accessed via its decays into electron (muon) at central (forward) rapidities. Here the status of the analysis and the most updated results is reported.

scholarly journals Transverse Single Spin Asymmetries of Forward π0 and Jet-like Events in s = 500 GeV Polarized Proton Collisions at STAR

2016 ◽  
Vol 40 ◽  
pp. 1660037 ◽  
Author(s):  
Yuxi Pan
Keyword(s):  
Final States ◽  
High Transverse Momentum ◽  
Initial State ◽  
Final State ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Polarized Proton ◽  
State Models

The large transverse single spin asymmetries (SSA) of high [Formula: see text] inclusive hadrons produced in polarized proton collisions are usually explained by means of collinear twist-3 multi-parton correlations. In this picture these asymmetries can originate from initial-state twist-3 parton distributions in the polarized proton and/or through the coupling between proton transversity and twist-3 fragmentation functions. The measurement of SSA for forward inclusive hadrons produced in [Formula: see text] collisions out to high transverse momentum helps to examine the validity and interplay of these initial- and final-state models. These models can be further explored by investigating the dependence of the SSA on event topologies. We present our latest status on the measurement of SSA for forward inclusive [Formula: see text] detected within [Formula: see text] in [Formula: see text] = 500 GeV [Formula: see text] collisions as well as its dependence on event topologies. We will also present our analysis of Sivers and Collins asymmetries for forward jet-like events consisting of multi-photon final states. The measurements are based on the data taken in 2011 with integrated luminosity [Formula: see text] 22 [Formula: see text].

scholarly journals SINGLE-SPIN ASYMMETRIES IN SEMI-INCLUSIVE DEEP INELASTIC SCATTERING AND DRELL-YAN PROCESSES

2014 ◽  
Vol 25 ◽  
pp. 1460015
Author(s):  
MATTHEW D. SIEVERT
Keyword(s):  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Time Reversal ◽  
Complex Phase ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Dependent Part ◽  
Single Spin Asymmetries ◽  
Sign Change ◽  
Symmetry Properties

In this brief article, we summarize our recent work1 regarding the origin of the nucleon Sivers functions within the diquark spectator model in semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY). We demonstrate that the C, P, T symmetry properties of transverse spinors always couple the spin-dependent part of the numerator algebra to the imaginary part of the denominator in the cross section. This complex phase, and its sign change under time reversal, is believed to be responsible for the predicted sign change of the Sivers functions in SIDIS and DY. We study the complex phase generated in both processes by the "color-lensing" mechanism and find that, although the phases appear to be different in structure between SIDIS and DY, they do give rise to the expected sign flip relation at leading twist.

scholarly journals Study of single-spin asymmetries with polarized target at the SPASCHARM experiment at U70 accelerator

2016 ◽  
Vol 678 ◽  
pp. 012048 ◽  
Author(s):  
V V Mochalov ◽  
V V Abramov ◽  
N A Bazhanov ◽  
N I Belikov ◽  
A A Borisov ◽  
...  
Keyword(s):  
Spin Asymmetries ◽  
Single Spin ◽  
Polarized Target ◽  
Single Spin Asymmetries

SINGLE SPIN ASYMMETRIES IN INCLUSIVE DIS AND MULTI-PARTON CORRELATIONS IN THE NUCLEON

2012 ◽  
Vol 20 ◽  
pp. 137-144
Author(s):  
ANDREAS METZ ◽  
DANIEL PITONYAK ◽  
ANDREAS SCHÄFER ◽  
MARC SCHLEGEL ◽  
WERNER VOGELSANG ◽  
...  
Keyword(s):  
Experimental Data ◽  
Spin Asymmetry ◽  
Recent Experimental Data ◽  
Hard Scattering ◽  
Photon Exchange ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Two Photon ◽  
Single Spin Asymmetries ◽  
Dependent Relation

Transverse single spin asymmetries in inclusive deep-inelastic lepton-nucleon scattering can be generated through multi-photon exchange between the leptonic and the hadronic part of the process. Here we consider two-photon exchange, and mainly focus on the transverse target spin asymmetry. In particular, we investigate the case where two photons couple to different quarks. Such a contribution involves a quark-photon-quark correlator in the nucleon, which has a (model-dependent) relation to the Efremov-Teryaev-Qiu-Sterman quark-gluon-quark correlator TF. Using different parameterizations for TF we compute the transverse target spin asymmetry for both a proton and a neutron target, and compare the results to recent experimental data. Potential implications on our general understanding of single spin asymmetries in hard scattering processes are discussed as well.

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