Publications (47)
Towards a model independent extraction of the Boer-Mulders function
E. Christova, D. Kotlorz, E. Leader
At present, the Boer-Mulders function for a given quark flavour has been extracted from data on semi-inclusive deep inelastic scattering using the simplifying, but theoretically in…
Scheme Dependence in Polarized Deep Inelastic Scattering
E. Leader, A. V. Sidorov, D. B. Stamenov
We study the effect of scheme dependence upon the NLO QCD analysis of the world data on polarized DIS. The reliability of an analysis at NLO is demonstrated by the consistency of o…
Can the Collins mechanism explain the large transverse single spin asymmetries observed in p(transv. polarized) p --> pion X?
M. Anselmino, M. Boglione, U. D'Alesio +2
We present a calculation of inclusive polarised and unpolarised cross sections within pQCD and the factorisation scheme, taking into account the parton intrinsic motion, k_T, in di…
Importance of Higher Twist Corrections in Polarized DIS
E. Leader, A. V. Sidorov, D. B. Stamenov
The higher twist corrections to the spin dependent proton and neutron structure functions are extracted from the world data on in a model independen…
Single spin asymmetries in DIS
M. Anselmino, E. Leader, F. Murgia
We consider possible mechanisms for single spin asymmetries in inclusive Deep Inelastic Scattering (DIS) processes with unpolarized leptons and transversely polarized nucleons. Tes…
The spin dependence of high energy proton scattering
N. H. Buttimore, B. Z. Kopeliovich, E. Leader +2
Motivated by the need for an absolute polarimeter to determine the beam polarization for the forthcoming RHIC spin program, we study the spin dependence of the proton-proton elasti…
Parton intrinsic motion: suppression of the Collins mechanism for transverse single spin asymmetries in p(transv. polarised) p --> pion + X
M. Anselmino, M. Boglione, U. D'Alesio +2
We consider a general formalism to compute inclusive polarised and unpolarised cross sections within pQCD and the factorisation scheme, taking into account parton intrinsic motion…
On the Role of Higher Twist in Polarized Deep Inelastic Scattering
E. Leader, A. V. Sidorov, D. B. Stamenov
The higher twist corrections to the spin dependent proton and neutron structure functions are extracted in a model independent way from experimental da…
The Gluon Sivers Distribution in D production at RHIC
M. Anselmino, M. Boglione, E. Leader +2
The single transverse spin asymmetry in D meson production at RHIC can provide a clean measure of the gluon Sivers distribution function. At intermediate rapidity, D production is…
The Role of Higher Twist in Determining Polarized Parton Densities from DIS data
E. Leader, A. V. Sidorov, D. B. Stamenov
Different methods to extract the polarized parton densities from the world polarized DIS data are considered. The higher twist corrections to the spin dependent proton…
Parton Densities and Fragmentation Functions from Polarized Lambda Production in Semi-Inclusive DIS
M. Anselmino, M. Boglione, U. D'Alesio +2
We consider the longitudinal polarization of Lambda and Lambda-bar produced in the current fragmentation region of polarized deep inelastic scattering. We show how the various cros…
Tests of the parametrizations of Fragmentation Functions using data on inclusive pion and kaon production in unpolarized collisions from the STAR collaboration and at the NICA project
D. Kotlorz, E. Christova, E. Leader
The goal of this study is to check which, if any, of the published versions of the pion and kaon fragmentation functions is compatible with the STAR data on semi-inclusive pion and…
Helicity Formalism and Spin Asymmetries in Hadronic Processes
M. Anselmino, M. Boglione, U. D'Alesio +3
We present a generalized QCD factorization scheme for the high energy inclusive polarized process, (A, S_A) + (B, S_B) -> C + X, including all intrinsic partonic motions. This intr…
The theory and phenomenology of polarized deep inelastic scattering
M. Anselmino, A. Efremov, E. Leader
Comprehensive review paper on the theory and phenomenology of polarized deep inelastic scattering, to appear in Physics Reports
Electron Scattering with Polarized Targets at TESLA
N Study Group, M. Anselmino, E. C. Aschenauer +39
Measurements of polarized electron-nucleon scattering can be realized at the TESLA linear collider facility with projected luminosities that are about two orders of magnitude highe…
General partonic structure for hadronic spin asymmetries
M. Anselmino, M. Boglione, U. D'Alesio +3
The high energy and large p_T inclusive polarized process, (A, S_A) + (B, S_B) --> C + X, is considered under the assumption of a generalized QCD factorization scheme. For the firs…
Fragmentation functions from semi-inclusive DIS pion production and implications for the polarized parton densities
E. Christova, S. Kretzer, E. Leader
By combining recent HERMES data on semi-inclusive DIS -production with the singlet fragmentation function , which is well determined from data, we are…
Spin Structure of the Nucleon - Status and Recent Results
S. E. Kuhn, J. -P. Chen, E. Leader
After the initial discovery of the so-called "spin crisis in the parton model" in the 1980's, a large set of polarization data in deep inelastic lepton-nucleon scattering was colle…
Can the polarization of the strange quarks in the proton be positive ?
E. Leader, D. B. Stamenov
Recently, the HERMES Collaboration at DESY, using a leading order QCD analysis of their data on semi-inclusive deep inelastic production of charged hadrons, reported a marginally p…
On the Sensitivity of the Polarized Parton Densities to Flavour SU(3) Symmetry Breaking
E. Leader, A. V. Sidorov, D. B. Stamenov
Motivated by the possibility that it may be misleading to assume SU(3) symmetry in the analysis of hyperon β-decays, we study the sensitivity of the polarized parton densities, de…
Contour gauges, canonical formalism and flux algebras
L. Lukaszuk, E. Leader, A. Johansen
A broad class of contour gauges is shown to be determined by admissible contractions of the geometrical region considered and a suitable equivalence class of curves is defined. In…
Form factor $Ï^0\to γ^* +γ^*$ at different photon virtualities
A. Anselm, A. Johansen, E. Leader +1
The vertex for virtual photons of squared masses and plays a vital rôle in several physical processes; for example for , , in the two…
Sivers and Collins effects in polarized pp scattering processes
M. Anselmino, M. Boglione, U. D'Alesio +3
We summarize the present phenomenology of Sivers and Collins effects for transverse single spin asymmetries in polarized proton-proton collisions within the framework of the genera…
On the role of Collins effect in the single spin asymmetry A_N in p(transv. polarized) p --> h X processes
M. Anselmino, M. Boglione, U. D'Alesio +4
The much debated issue of the transverse single spin asymmetry A_N observed in the inclusive large P_T production of a single hadron in pp interactions, p(transv. polarized) p -->…
NLO QCD Analysis of Polarized Deep Inelastic Scattering
E. Leader, A. V. Sidorov, D. B. Stamenov
We have carried out a NLO analysis of the world data on polarized DIS in the MS/bare scheme. We have studied two models of the parametrizations of the input parton densities, the f…
On the potential role of the Collins effect in A_N in pp --> pion X
M. Anselmino, M. Boglione, U. D'Alesio +4
Transverse single spin asymmetries in pp --> pion X processes, while on a quite firm ground experimentally, are still a much debated phenomenological issue. We consider them in a t…
The odderon and spin-flip dependence of high energy proton-proton scattering
E. Leader, T. L. Trueman
The sensitivity of the spin dependence of high energy pp scattering, particularly the asymmetry A_{NN}, to the odderon is demonstrated. Several possible ways of determining the spi…
Accessing Sivers gluon distribution via transverse single spin asymmetries in p(transv. polarized) p --> D X processes at RHIC
M. Anselmino, M. Boglione, U. D'Alesio +2
The production of D mesons in the scattering of transversely polarized protons off unpolarized protons at RHIC offers a clear opportunity to gain information on the Sivers gluon di…
The angular momentum controversy: What's it all about and does it matter?
E. Leader, C. Lorce
The general question, crucial to an understanding of the internal structure of the nucleon, of how to split the total angular momentum of a photon or gluon into spin and orbital co…
Polarized Parton Densities in the Nucleon
E. Leader, A. V. Sidorov, D. B. Stamenov
We present a critical assessment of what can be learnt from the present data on inclusive polarized DIS. We examine critically some of the simplifying assumptions made in recent an…
A Possible Explanation of the Excess Jet Production at Large E_T
E. Leader, D. B. Stamenov
We demonstrate that the significant discrepancy between the previous predictions of the conventional QCD and the CDF inclusive jet production data could be an indication that the b…
On the importance of Lorentz structure in the parton model: target mass corrections, transverse momentum dependence, positivity bounds
U. D'Alesio, E. Leader, F. Murgia
We show that respecting the underlying Lorentz structure in the parton model has very strong consequences. Failure to insist on the correct Lorentz covariance is responsible for th…
On model independent extraction of the Kaon Fragmentation Functions
S. Albino, E. Christova, E. Leader
We present a model independent approach to FFs, which allows to determine uniquely the non-singlet combination (D_u-D_d)^{K^++K^-} of the kaon FFs, independently in the three diffe…
Intrinsic parton motion soft mechanisms and the longitudinal spin asymmetry A_LL in high energy pp -> pi X
M. Anselmino, M. Boglione, U. D'Alesio +3
The longitudinal double spin asymmetry A_LL in the reaction pp --> pi X has been measured at RHIC with extremely interesting consequences. If the gluon polarization in a proton wer…
A critique of the angular momentum sum rules and a new angular momentum sum rule
B. L. G. Bakker, E. Leader, T. L. Trueman
We present a study of the tensorial structure of the hadronic matrix elements of the angular momentum operators . Well known results in the literature are shown to be incor…
Sivers and Collins Effects: from SIDIS to Proton-Proton Inclusive Pion Production
M. Anselmino, M. Boglione, U. D'Alesio +4
We consider the Sivers, Collins and transversity functions as extracted from SIDIS and e+e- experimental data and investigate to what extent they might explain the large Single Spi…
An absolute polarimeter for high energy protons
N. H. Buttimore, E. Leader, T. L. Trueman
A study of the spin asymmetries for polarized elastic proton proton collisions in the electromagnetic hadronic interference (CNI) region of momentum transfer provides a method of s…
An exact sum rule for transversely polarized DIS
A. V. Efremov, E. Leader, O. V. Teryaev
The Operator Product Expansion provides expressions for the moments of and in terms of hadronic matrix elements of local operators for odd integer.…
New study of the Boer-Mulders function: Implications for the quark and hadron transverse momenta
E. Christova, D. Kotlorz, E. Leader
In series of papers the Boer-Mulders function for a given quark flavour has been extracted: (i) from data on semi-inclusive deep inelastic scattering, using the simplifying, but th…
An Alternative Approach to Semi-inclusive DIS and A Model Independent Determination of D_u^{Ï^+}, D_d^{Ï^+} and D_s^{Ï^+}
E. Christova, E. Leader, S. Kretzer
We discuss how to extract the polarized parton densities and fragmentation functions in a model independent way from SIDIS, and present results for D_{u,d,s}^{Ï^+}.
Fragmentation functions and their role in determining the polarized parton densities
S. Kretzer, E. Leader, E. Christova
We extract the pion fragmentation functions and their uncertainties from a judicious choice of e+e- and semi-inclusive DIS data. These are used to study the error propagation in th…
General helicity formalism for Single and Double Spin Asymmetries in p p --> pion + X
M. Anselmino, M. Boglione, U. D'Alesio +3
We consider within a generalized QCD factorization approach, the high energy inclusive polarized process p p --> pion + X, including all intrinsic partonic motions. Several new spi…
A New Evaluation of Polarized Parton Densities in the Nucleon
E. Leader, A. V. Sidorov, D. B. Stamenov
We present a new leading and next-to-leading QCD analysis of the world data on inclusive polarized deep inelastic scattering. A new set of polarized parton densities is extracted f…
Reassessment of the Collins Mechanism for Single-spin Asymmetries and the behavior of Delta d(x) at large x
M. Boglione, E. Leader
It is shown that the Collins mechanism explanation of the transverse single-spin asymmetries in p^{\uparrow} p -> ÏX leads to a transversely polarized d quark density Delta_T d(x)…
Positivity of NLO Spin-Dependent Parton Distributions
C. Bourrely, E. Leader, O. V. Teryaev
We discuss the positivity of the hadron density matrix in QCD. This basic property is shown to be preserved by QCD evolution, provided the relation is v…
Semi-inclusive hadron-hadron transverse spin asymmetries and their implication for polarized DIS
M. Boglione, E. Leader
We discuss a possible explanation of the 25 year old mystery of the large transverse spin asymmetries found in many semi-inclusive hadron-hadron reactions. We obtain the first reli…
Gamma^*, Z^* production in polarised p-p scattering as a probe of the proton spin structure
E. Leader, Sridhar K
We present the results of a detailed study of the large transverse momentum Drell-Yan process, pp --> (Gamma^*, Z^*)X --> l^+l^- X at collider energies, with either one or both pro…