Extra spin asymmetries from the breakdown of transverse-momentum-dependent factorization in hadron-hadron collisions

Rogers, T. C.

doi:10.1103/physrevd.88.014002

Cited by 43 publications

(28 citation statements)

References 138 publications

(305 reference statements)

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“…[5][6][7], the structure of the gauge link, including transverse pieces at light-cone infinity, plays a very important role in the understanding of single-spin asymmetries at high energies. However, the presence of the gauge link complicates the study of factorization in processes involving TMD correlators [8][9][10][11][12], and it is important to understand their universality issues. Towards this goal, we note that the TMD correlators can be ordered according to their p T dependence, which can conveniently be written in terms of symmetric traceless tensors constructed from p T .…”

Section: Introductionmentioning

confidence: 99%

Generalized universality of definite rank gluon transverse momentum dependent correlators

2013

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Transverse momentum dependent (TMD) parton correlators describing the partonic structure of hadrons contain gauge links, required by color gauge invariance. The required gauge links enter in the matrix elements that contain the parton fields and depend on the color flow in the hard process. The correlators are expanded in terms of transverse momentum dependent parton distribution functions, referred to as TMD PDFs, or in short TMDs. In this paper, we introduce gluon TMDs of definite rank, by making an expansion of the TMD gluon correlator with the help of irreducible tensors built from the transverse momenta. The process dependence is isolated in gauge-link-dependent gluonic pole factors multiplying the TMDs. It is important to account for the different possibilities in the color structure within the matrix elements, leading to multiple TMDs at a given rank. In this way we are able to write the leading tree-level result for a hard process in terms of process-dependent gluon correlators which are expressed in a finite set of universal TMDs. We tabulate the gluonic pole factors for various gauge links, among them those that are relevant for 2 ! 2 processes.

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Section: Introductionmentioning

confidence: 99%

Generalized universality of definite rank gluon transverse momentum dependent correlators

2013

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“…[12,13]). Moreover, a proof of factorisation in terms of TMDs for such processes (where only one energy scale is present) is still lacking [14] and potential factorisation breaking effects could be expected [15]. Testing of universality is therefore a very non-trivial topic, sensitive to important aspects of QCD.On the other hand, the study of the azimuthal distribution of leading hadrons produced in the fragmentation of a large transverse momentum jet offers a unique opportunity for studying TMDs as well as factorisation breaking effects in hadronic collisions and, by comparison with SIDIS and e + e − annihilations, get information on the process dependence of the TMD functions.…”

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confidence: 99%

Testing the universality of the Collins function in pion-jet production at RHIC

2017

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By adopting a generalised parton model approach at leading order in QCD, including spin and intrinsic parton motion effects, we study the Collins azimuthal asymmetries for pions within a large-pT jet produced at mid-rapidity in polarised hadronic collisions. Using available information on the quark transversity distributions and the pion Collins functions, as extracted from semi-inclusive deeply inelastic scattering and e+ e- -> h1 h2 X processes, we compute estimates for the Collins asymmetries in kinematical configurations presently investigated at RHIC by the STAR Collaboration. Collins-like asymmetries, involving linearly polarised gluons, are also considered. Our predictions, compared against available preliminary data, show a very good agreement, even if some discrepancies, to be further scrutinized both theoretically and experimentally, appear in the transverse momentum dependence of the Collins asymmetry. These results are in favour of the predicted universality of the Collins function and of a mild, if any, evolution with the hard scale of the asymmetries

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“…They may perhaps be disentangled for certain transverse moments [40][41][42]. This entanglement does not only jeopardize predictions, it may also lead to additional angular dependences that are otherwise absent [43]. At present nothing is known about the size of this type of factorization breaking contributions.…”

Section: Process Dependencementioning

confidence: 99%

Gluon TMDs in Quarkonium Production

Boer

2017

Few-Body Syst

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Quarkonium production offers good possibilities to study gluon TMDs. In this proceedings contribution this topic is explored for the linearly polarized gluons inside unpolarized hadrons and unpolarized gluons inside transversely polarized hadrons. It is argued that χ b0/2 and η b production at LHC are best to study the effects of linearly polarized gluons in hadronic collisions, by means of angular independent ratios of ratios of cross sections. This can be directly compared to cos 2φ asymmetries in heavy quark pair and dijet production in DIS at a future high-energy Electron-Ion Collider (EIC), which probe the same TMDs. In the small-x limit this corresponds to the Weizsäcker-Williams (WW) gluon distributions, which should show a change in behavior for transverse momenta around the saturation scale. Together with investigations of the dipole (DP) gluon distributions, this can provide valuable information about the polarization of the Color Glass Condensate if sufficiently small x-values are reached. Quarkonia can also be useful in the study of single transverse spin asymmetries. For transversely polarized hadrons the gluon distribution can be asymmetric, which is referred to as the Sivers effect. It leads to single spin asymmetries in for instance J/ψ (pair) production at AFTER@LHC, which probe the WW or f -type gluon Sivers TMD. It allows for a test of a sign-change relation w.r.t. the gluon Sivers TMD probed at an EIC in open heavy quark pair production. Single spin asymmetries in backward inclusive C-odd quarkonium production, such as J/ψ production, may offer probes of the DP or d-type gluon Sivers TMD at small x-values in the polarized proton, which in that limit corresponds to a correlator of a single Wilson loop, describing the spin-dependent odderon.

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Extra spin asymmetries from the breakdown of transverse-momentum-dependent factorization in hadron-hadron collisions

Cited by 43 publications

References 138 publications

Generalized universality of definite rank gluon transverse momentum dependent correlators

Generalized universality of definite rank gluon transverse momentum dependent correlators

Testing the universality of the Collins function in pion-jet production at RHIC

Gluon TMDs in Quarkonium Production

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