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Feng Yuan - One of the best experts on this subject based on the ideXlab platform.
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gluon distribution functions and higgs boson production at moderate Transverse Momentum
Physical Review D, 2011Co-Authors: Bowen Xiao, Feng YuanAbstract:We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the Transverse Momentum-dependent factorization formalism. In addition to the usual azimuthal symmetric Transverse Momentum-dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the Transverse Momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive k{sub t}-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account. The result agrees with the Transverse Momentum-dependent factorization formalism. We comment on the possible breakdown of the naive k{sub t}-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.
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Transverse Momentum dependent distribution functions in the bag model
Physical Review D, 2010Co-Authors: Harut Avakian, A Efremov, P Schweitzer, Feng YuanAbstract:Leading and subleading twist Transverse Momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular Momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the Transverse Momentum dependence of TMDs.
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qcd factorization for semi inclusive deep inelastic scattering at low Transverse Momentum
Physical Review D, 2005Co-Authors: J P, Feng YuanAbstract:We argue a factorization formula for semi-inclusive deep-inelastic scattering with hadrons in the current fragmentation region detected at low Transverse Momentum. To facilitate the factorization, we introduce the Transverse-Momentum dependent parton distributions and fragmentation functions with gauge links slightly off the light cone, and with soft-gluon radiations subtracted. We verify the factorization to one-loop order in perturbative quantum chromodynamics and argue that it is valid to all orders in perturbation theory.
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qcd factorization for semi inclusive deep inelastic scattering at low Transverse Momentum
Physical Review D, 2005Co-Authors: Xiangdong Ji, J P, Feng YuanAbstract:We demonstrate a factorization formula for semi-inclusive deep-inelastic scattering with hadrons in the current fragmentation region detected at low Transverse Momentum. To facilitate the factorization, we introduce the Transverse-Momentum dependent parton distributions and fragmentation functions with gauge links slightly off the light-cone, and with soft-gluon radiations subtracted. We verify the factorization to one-loop order in perturbative quantum chromodynamics and argue that it is valid to all orders in perturbation theory.
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collins soper equation for the energy evolution of Transverse Momentum and spin dependent parton distributions
Physical Review D, 2004Co-Authors: Ahmad Idilbi, J P, Feng YuanAbstract:The hadron-energy evolution (Collins and Soper) equation for all the leading-twist Transverse-Momentum and spin dependent parton distributions is derived in the impact parameter space. Based on this equation, we present a resummation formulas for the spin dependent structure functions of the semi-inclusive deep-inelastic scattering.
P J Mulders - One of the best experts on this subject based on the ideXlab platform.
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no generalized Transverse Momentum dependent factorization in the hadroproduction of high Transverse Momentum hadrons
Physical Review D, 2010Co-Authors: T C Rogers, P J MuldersAbstract:It has by now been established that standard QCD factorization using Transverse Momentum dependent parton distribution functions fails in hadroproduction of nearly back-to-back hadrons with high Transverse Momentum. The essential problem is that gauge-invariant Transverse Momentum dependent parton distribution functions cannot be defined with process-independent Wilson line operators, thus implying a breakdown of universality. This has led naturally to proposals that a correct approach is to instead use a type of generalized Transverse Momentum dependent factorization in which the basic factorized structure is assumed to remain valid, but with Transverse Momentum dependent parton distribution functions that contain nonstandard, process-dependent Wilson line structures. In other words, to recover a factorization formula, it has become common to assume that it is sufficient to simply modify the Wilson lines in the parton correlation functions for each separate hadron. In this paper, we will illustrate by direct counterexample that this is not possible in a non-Abelian gauge theory. Since a proof of generalized Transverse Momentum dependent factorization should apply generally to any hard hadroproduction process, a single counterexample suffices to show that a general proof does not exist. Therefore, to make the counter-argument clear and explicit, we illustrate with a specific calculation for a double spin asymmetry in a spectator model with a non-Abelian gauge field. The observed breakdown of generalized Transverse Momentum dependent factorization challenges the notion that the role of parton Transverse Momentum in such processes can be described using separate correlation functions for each external hadron. © 2010 The American Physical Society.
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non universality of Transverse Momentum dependent parton distribution functions
Nuclear Physics, 2008Co-Authors: C J Bomhof, P J MuldersAbstract:Abstract In the field theoretical description of hadronic scattering processes, single Transverse-spin asymmetries arise due to gluon initial and final state interactions. These interactions lead to process dependent Wilson lines in the operator definitions of Transverse Momentum dependent parton distribution functions. In particular for hadron–hadron scattering processes with hadronic final states this has important ramifications for possible factorization formulas in terms of (non)universal TMD parton distribution functions. In this paper we will systematically separate the universality-breaking parts of the TMD parton correlators from the universal T -even and T -odd parts. This might play an important role in future factorization studies for these processes. We also show that such factorization theorems will (amongst others) involve the gluonic pole cross sections, which have previously been shown to describe the hard partonic scattering in weighted spin asymmetries.
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semi inclusive deep inelastic scattering at small Transverse Momentum
Journal of High Energy Physics, 2007Co-Authors: Alessandro Bacchetta, P J Mulders, Markus Diehl, Andreas Metz, Klaus Goeke, Marc SchlegelAbstract:We study the cross section for one-particle inclusive deep inelastic scattering off the nucleon for low Transverse Momentum of the detected hadron. We decompose the cross section in terms of structure functions and calculate them at tree level in terms of Transverse-Momentum-dependent parton distribution and fragmentation functions. Our results are complete in the one-photon exchange approximation at leading and first subleading twist accuracy, with both beam and target polarization. © SISSA 2007.
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Transverse Momentum dependence in gluon distribution and fragmentation functions
Physical Review D, 2001Co-Authors: P J Mulders, J RodriguesAbstract:We investigate the twist two gluon distribution functions for spin-1/2 hadrons, emphasizing the intrinsic Transverse Momentum of the gluons. These functions are relevant in leading order in the inverse hard scale in scattering processes such as inclusive leptoproduction or Drell-Yan scattering, or more generally in hard processes in which at least two hadrons are involved. They show up in azimuthal asymmetries. For future estimates of such observables, we discuss specific bounds on these functions. ©2001 The American Physical Society.
Ignazio Scimemi - One of the best experts on this subject based on the ideXlab platform.
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linearly polarized gluons at next to next to leading order and the higgs Transverse Momentum distribution
Journal of High Energy Physics, 2019Co-Authors: Daniel Gutierrezreyes, Ignazio Scimemi, Sergio Lealgomez, Alexey VladimirovAbstract:We calculate the small-b (or large-q$_{T}$) matching of Transverse Momentum de- pendent (TMD) distribution for linearly polarized gluons to the integrated gluon distributions at the next-to-next-to-leading order (NNLO). This is the last missing part for the complete NNLO prediction of the Higgs spectrum within TMD factorization. We discuss the numerical impact of the correction so derived to the q$_{T}$ -differential cross-section for Higgs boson production and to the positivity bound for linearly polarized gluon Transverse Momentum distribution.
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Model independent evolution of Transverse Momentum dependent distribution functions (TMDs) at NNLL
The European Physical Journal C, 2013Co-Authors: Miguel G. Echevarria, Ahmad Idilbi, Andreas Schäfer, Ignazio ScimemiAbstract:We discuss the evolution of the eight leading-twist Transverse Momentum dependent parton distribution functions, which turns out to be universal and spin independent. By using the highest order perturbatively calculable ingredients at our disposal, we perform the resummation of the large logarithms that appear in the evolution kernel of Transverse Momentum distributions up to next-to-next-to-leading logarithms (NNLL), thus obtaining an expression for the kernel with highly reduced model dependence. Our results can also be obtained using the standard CSS approach when a particular choice of the b ^∗ prescription is used. In this sense, and while restricted to the perturbative domain of applicability, we consider our results as a “prediction” of the correct value of b _max which is very close to 1.5 GeV^−1. We explore under which kinematical conditions the effects of the non-perturbative region are negligible, and hence the evolution of Transverse Momentum distributions can be applied in a model independent way. The application of the kernel is illustrated by considering the unpolarized Transverse Momentum dependent parton distribution function and the Sivers function.
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soft and collinear factorization and Transverse Momentum dependent parton distribution functions
Physics Letters B, 2013Co-Authors: Miguel G. Echevarria, Ahmad Idilbi, Ignazio ScimemiAbstract:Abstract In this work we consider how a parton distribution function, with an explicit Transverse Momentum dependence can be properly defined in a regularization-scheme independent manner. We argue that by considering a factorized form of the Transverse Momentum dependent spectrum for the production of a heavy lepton pair in Drell–Yan reaction, one should first split the relevant soft function into two boost invariant contributions. When those soft contributions are added to the pure collinear contributions, well-defined hadronic matrix elements emerge, i.e., the Transverse Momentum dependent distributions. We also perform a comparison with Collinsʼ definition.
A Prokudin - One of the best experts on this subject based on the ideXlab platform.
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role of Transverse Momentum dependence of unpolarized parton distribution and fragmentation functions in the analysis of azimuthal spin asymmetries
Physical Review D, 2018Co-Authors: M Anselmino, M Boglione, A Prokudin, U Dalesio, F MurgiaAbstract:Information on the Sivers distribution and the Collins fragmentation functions and their Transverse Momentum dependence is mainly based on fitting single-spin asymmetry data from semi-inclusive deep inelastic scattering (SIDIS). Independent information on the Sivers distribution and the Collins fragmentation can be obtained from the Drell-Yan and ${e}^{+}{e}^{\ensuremath{-}}$ annihilation processes, respectively. In the SIDIS case, the Transverse Momentum of the final observed hadron, which is the quantity measured, is generated both by the average Transverse Momentum in the distribution and by that in the fragmentation functions. As a consequence, these are strongly correlated, and a separate extraction is made difficult. In this paper we investigate, in a simple kinematical Gaussian configuration, this correlation, its role on the Transverse single-spin asymmetries in SIDIS, and the consequences for predictions of the Sivers asymmetry in Drell-Yan processes and for the Collins asymmetry in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. We find that, in some cases, these effects can be relevant and must be carefully taken into account.
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unpolarised Transverse Momentum dependent distribution and fragmentation functions from sidis multiplicities
Journal of High Energy Physics, 2014Co-Authors: M Anselmino, M Boglione, S Melis, A ProkudinAbstract:The unpolarised Transverse Momentum dependent distribution and fragmen- tation functions are extracted from HERMES and COMPASS experimental measurements of SIDIS multiplicities for charged hadron production. The data are grouped into indepen- dent bins of the kinematical variables, in which the TMD factorisation is expected to hold. A simple factorised functional form of the TMDs is adopted, with a Gaussian dependence on the intrinsic Transverse Momentum, which turns out to be quite adequate in shape. HERMES data do not need any normalisation correction, whilets of the COMPASS data much improve with a y-dependent overall normalisation factor. A comparison of the ex- tracted TMDs with previous EMC and JLab data conrms the adequacy of the simple Gaussian distributions. The possible role of the TMD evolution is briey considered.
M Anselmino - One of the best experts on this subject based on the ideXlab platform.
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role of Transverse Momentum dependence of unpolarized parton distribution and fragmentation functions in the analysis of azimuthal spin asymmetries
Physical Review D, 2018Co-Authors: M Anselmino, M Boglione, A Prokudin, U Dalesio, F MurgiaAbstract:Information on the Sivers distribution and the Collins fragmentation functions and their Transverse Momentum dependence is mainly based on fitting single-spin asymmetry data from semi-inclusive deep inelastic scattering (SIDIS). Independent information on the Sivers distribution and the Collins fragmentation can be obtained from the Drell-Yan and ${e}^{+}{e}^{\ensuremath{-}}$ annihilation processes, respectively. In the SIDIS case, the Transverse Momentum of the final observed hadron, which is the quantity measured, is generated both by the average Transverse Momentum in the distribution and by that in the fragmentation functions. As a consequence, these are strongly correlated, and a separate extraction is made difficult. In this paper we investigate, in a simple kinematical Gaussian configuration, this correlation, its role on the Transverse single-spin asymmetries in SIDIS, and the consequences for predictions of the Sivers asymmetry in Drell-Yan processes and for the Collins asymmetry in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. We find that, in some cases, these effects can be relevant and must be carefully taken into account.
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unpolarised Transverse Momentum dependent distribution and fragmentation functions from sidis multiplicities
Journal of High Energy Physics, 2014Co-Authors: M Anselmino, M Boglione, S Melis, A ProkudinAbstract:The unpolarised Transverse Momentum dependent distribution and fragmen- tation functions are extracted from HERMES and COMPASS experimental measurements of SIDIS multiplicities for charged hadron production. The data are grouped into indepen- dent bins of the kinematical variables, in which the TMD factorisation is expected to hold. A simple factorised functional form of the TMDs is adopted, with a Gaussian dependence on the intrinsic Transverse Momentum, which turns out to be quite adequate in shape. HERMES data do not need any normalisation correction, whilets of the COMPASS data much improve with a y-dependent overall normalisation factor. A comparison of the ex- tracted TMDs with previous EMC and JLab data conrms the adequacy of the simple Gaussian distributions. The possible role of the TMD evolution is briey considered.
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Transverse Momentum dependent parton distribution fragmentation functions at an electron ion collider
European Physical Journal A, 2011Co-Authors: M Anselmino, Daniël Boer, Harut Avakian, F Bradamante, Matthias Burkardt, J P Chen, E Cisbani, M Contalbrigo, D Crabb, D DuttaAbstract:We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The Transverse-Momentum-dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single-spin asymmetries (SSA) from semi-inclusive deep inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D (D production at large Transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the unexplored sea quark region along with a study of their evolution.
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Transverse Momentum dependent parton distribution fragmentation functions at an electron ion collider
arXiv: High Energy Physics - Experiment, 2011Co-Authors: M Anselmino, Daniël Boer, Harut Avakian, F Bradamante, Matthias Burkardt, J P Chen, E Cisbani, M Contalbrigo, D Crabb, D DuttaAbstract:We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The Transverse Momentum dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single spin asymmetries (SSA) from semi-inclusive deep-inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D (`D) production at large Transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the sea quark region along with a study of their evolution.
