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Collins-Soper kernel and reduced soft function in lattice QCD

Alexandrou, Constantia [University of Cyprus, Nicosia (Cyprus); The Cyprus Institute, Nicosia (Cyprus)] (ORCID:0000000191363621)Ā·Bacchio, Simone [The Cyprus Institute, Nicosia (Cyprus)] (ORCID:000000025532450X)Ā·Cichy, Krzysztof [Adam Mickiewicz University, Poznań (Poland)] (ORCID:0000000257053256)Ā·Constantinou, Martha [Temple University, Philadelphia, PA (United States)] (ORCID:0000000269881745)Ā·Sen, Aniket [Rheinische Friedrich-Wilhelms-UniversitƤt Bonn (Germany)] (ORCID:0000000275511126)Ā·Spanoudes, Gregoris [University of Cyprus, Nicosia (Cyprus)] (ORCID:0000000170202570)Ā·Steffens, Fernanda [Rheinische Friedrich-Wilhelms-UniversitƤt Bonn (Germany)]Ā·Tarello, Jacopo [University of Cyprus, Nicosia (Cyprus); The Cyprus Institute, Nicosia (Cyprus)] (ORCID:0009000616168598)
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Abstract

We evaluate the Collins-Soper kernel and the reduced soft function in lattice QCD, incorporating š’Ŗā”(š›¼ š‘  ) matching corrections. The calculation relies on the evaluation of the quasitransverse momentumā€“dependent wave function with asymmetric staple-shaped quark bilinear operators and four-point meson form factors. These quantities are computed nonperturbatively using two š‘ š‘“ =2 + 1 + 1 twisted-mass fermion ensembles with the same lattice spacing of š‘Ž = 0.093 fm: the first ensemble has a lattice size of 24 3 Ɨ 48 and a pion mass of 346 MeV, and the second one has a lattice size of 32 3 Ɨ 64 and a pion mass of 261 MeV. The Collins-Soper kernel and the soft function are needed for the determination of the transverse momentumā€“dependent parton distribution functions.

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Alexandrou, Constantia [University of Cyprus, Nicosia (Cyprus); The Cyprus Institute, Nicosia (Cyprus)] (ORCID:0000000191363621), Bacchio, Simone [The Cyprus Institute, Nicosia (Cyprus)] (ORCID:000000025532450X), Cichy, Krzysztof [Adam Mickiewicz University, Poznań (Poland)] (ORCID:0000000257053256), Constantinou, Martha [Temple University, Philadelphia, PA (United States)] (ORCID:0000000269881745), Sen, Aniket [Rheinische Friedrich-Wilhelms-UniversitƤt Bonn (Germany)] (ORCID:0000000275511126), Spanoudes, Gregoris [University of Cyprus, Nicosia (Cyprus)] (ORCID:0000000170202570), Steffens, Fernanda [Rheinische Friedrich-Wilhelms-UniversitƤt Bonn (Germany)], Tarello, Jacopo [University of Cyprus, Nicosia (Cyprus); The Cyprus Institute, Nicosia (Cyprus)] (ORCID:0009000616168598). 2026-04-09. Collins-Soper kernel and reduced soft function in lattice QCD. https://doi.org/10.1103/5wft-9rtd

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