### Transversity from First Principles in QCD

"... Summary. — Transversity observables, such as the T-odd Sivers single-spin asymmetry measured in deep inelastic lepton scattering on polarized protons and the distributions which are measured in deeply virtual Compton scattering, provide important constraints on the fundamental quark and gluon struct ..."

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Summary. — Transversity observables, such as the T-odd Sivers single-spin asymmetry measured in deep inelastic lepton scattering on polarized protons and the distributions which are measured in deeply virtual Compton scattering, provide important constraints on the fundamental quark and gluon structure of the proton. In this talk I discuss the challenge of computing these observables from first principles; i.e.; quantum chromodynamics, itself. A key step is the determination of the frame-independent light-front wavefunctions (LFWFs) of hadrons – the QCD eigensolutions which are analogs of the Schrödinger wavefunctions of atomic physics. The lensing effects of initial-state and final-state interactions, acting on LFWFs with different orbital angular momentum, lead to T-odd transversity observables such as the Sivers, Collins, and Boer-Mulders distributions. The lensing effect also leads to leading-twist phenomena which break leading-twist factorization such as the breakdown of the Lam-Tung relation in Drell-Yan reactions. A similar rescattering mechanism also leads to diffractive deep inelastic scattering, as well as nuclear shadowing and non-universal antishadowing. It is thus important to distinguish “static ” structure functions, the probability distributions computed the target hadron’s light-front wavefunctions, versus “dynamical ” structure functions which include the effects of initial- and final-state rescattering. I also discuss related effects such as the J = 0 fixed pole contribution which appears in the real part of the virtual Compton amplitude. AdS/QCD, together with “Light-Front Holography”, provides a simple Lorentz-invariant color-confining approximation to QCD which is successful in accounting for light-quark meson and baryon spectroscopy as well as hadronic LFWFs. 1.

### QCD Analysis of the Polarized World Data

"... The results of a recent next-to-leading order QCD analysis of the world data on polarized deep inelastic scattering are reported. New parameterizations are derived for the quark and gluon distributions and the value of αs(M2z) is determined. We obtain αNLOs (M2Z) = 0.1132 +0.0056 −0.0095. Potential ..."

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The results of a recent next-to-leading order QCD analysis of the world data on polarized deep inelastic scattering are reported. New parameterizations are derived for the quark and gluon distributions and the value of αs(M2z) is determined. We obtain αNLOs (M2Z) = 0.1132 +0.0056 −0.0095. Potential higher twist contributions to the structure function g1(x,Q2) are considered.

### and transverse momentum effects

"... COMPASS results on transverse transverse spin ..."

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### Cermet Spent Nuclear Fuel Casks and Waste Packages

, 2006

"... by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. File: MSR Cermet ..."

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by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. File: MSR Cermet

### unknown title

, 810

"... EPJ manuscript No. (will be inserted by the editor) Pion-nucleon charge-exchange amplitudes above 2 GeV ..."

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EPJ manuscript No. (will be inserted by the editor) Pion-nucleon charge-exchange amplitudes above 2 GeV

### Coupled-channels study of the π − p → ηn process

, 2008

"... The reaction π−p → ηn is investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region. The meson baryon channels included are πN, ηN, π∆, σN, and ρN. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians ..."

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The reaction π−p → ηn is investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region. The meson baryon channels included are πN, ηN, π∆, σN, and ρN. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two excited nucleon states in each of S, P, D, and F partial waves are included to generate the resonant amplitudes. Data of π−p → ηn reaction from threshold up to a total center-of-mass energy of about 2 GeV are satisfactorily reproduced and the roles played by the following nine nucleon resonances are investigated:

### SLAC-PUB-15408 Single-Spin Asymmetries in Semi-inclusive Deep Inelastic Scattering and Drell-Yan Processes

, 2013

"... We examine in detail the diagrammatic mechanisms which provide the change of sign between the single transverse spin asymmetries measured in semi-inclusive deep inelastic scattering (SIDIS) and in the Drell-Yan process (DY). This asymmetry is known to arise due to the transverse spin dependence of t ..."

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We examine in detail the diagrammatic mechanisms which provide the change of sign between the single transverse spin asymmetries measured in semi-inclusive deep inelastic scattering (SIDIS) and in the Drell-Yan process (DY). This asymmetry is known to arise due to the transverse spin dependence of the target proton combined with a T-odd complex phase. Using the discrete symmetry properties of transverse spinors, we show that the required complex phase originates in the denominators of rescattering diagrams and their respective cuts. For simplicity, we work in a model where the proton consists of a valence quark and a scalar diquark. We then show that the phases generated in SIDIS and in DY originate from distinctly different cuts in the amplitudes, which at first appears to obscure the relationship between the single-spin asymmetries in the two processes. Nevertheless, further analysis demonstrates that the contributions of these cuts are identical in the leading-twist Bjorken kinematics considered, resulting in the standard sign-flip relation between the Sivers functions in SIDIS and DY. Physically, this fundamental, but yet untested, prediction occurs because the Sivers effect in the Drell-Yan reaction is modified by the initial-state “lensing ” interactions of the annihilating antiquark, in contrast to the final-state lensing which produces the Sivers effect in deep inelastic scattering.

### New measurements of transverse spin asymmetries at COMPASS F. Sozzi on behalf of the COMPASS Collaboration

"... The study of transverse momentum effects and transverse spin structure of the nucleon is an important part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. The transverse effects are investigated via semi inclusive DIS reactions with a 160 GeV/c muon beam impinging on ..."

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The study of transverse momentum effects and transverse spin structure of the nucleon is an important part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. The transverse effects are investigated via semi inclusive DIS reactions with a 160 GeV/c muon beam impinging on transversely polarised targets. The hadrons produced in the reactions are detected in a wide momentum and angular range by a two-stage spectrometer. A deuterium target has been used in the first part of COMPASS data taking from 2002 to 2004, while a proton target has been used in 2007 and 2010. Here we present the recent results obtained from the 2010 data on different channels, involving the azimuthal distribution of single hadrons and the azimuthal dependence of the plane containing hadron pairs. The results confirm the published results of the 2007 data taking with an improved statistical significance; the measured azimuthal asymmetries are clearly non zero, at variance with those measured on a deuterium target. 1

### The polarized TMDs in the covariant parton model approach1

, 2010

"... Abstract. We derive relations between polarized transverse momentum dependent distribu-tion 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 sym-metric distribution of parto ..."

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Abstract. We derive relations between polarized transverse momentum dependent distribu-tion 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 sym-metric distribution of parton momenta in the nucleon rest frame. Using the known PDF gq1(x) as input we predict the x- and pT-dependence of all polarized twist-2 naively time-reversal even (T-even) TMDs. TMDs [1, 2] open a new way to a more complete understanding of the quark-gluon structure of the nucleon. Indeed, some experimental observations can hardly be explained without a more accurate and realistic 3D picture of the nucleon, which naturally includes transverse motion. The azimuthal asymmetry in the distribution of hadrons produced in deep-inelastic lepton-nucleon scattering (DIS), known as the Cahn effect [3], is a classical example. The intrinsic (transversal) parton motion is also crucial for the explanation of some spin effects [4]–[16]. In previous studies we discussed the covariant parton model, which is based on the 3D picture of parton momenta with rotational symmetry in the nucleon rest frame [17]–[26]. In this model we studied all T-even TMDs and derived a set of relations among them [23]. It should be remarked that some of the relations among different TMDs were found (sometimes before) also in other models [27]–[34]. In the recent paper [35] we further develop and broadly extend our studies [24]–[25] of the relations between TMDs and PDFs. The formulation of the model in terms of the light-cone formalism [23] allows us to compute the leading-twist TMDs by means of the light-front