A constrained fit of the valence transversity distributions from dihadron production

Abstract

We present a constrained analysis of the valence transversity Parton Distribution Functions from dihadron production in semi-inclusive DIS. While usual extractions of the transversity distributions rely explicitly on the fulfillment of the Soffer bound, the present analysis releases that restriction to implement further constraints through the method of Lagrange multipliers. The results are quantitatively comparable to previous analyses in the kinematical range of data; the qualitative impact translates into an increased flexibility in the functional form.

Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons

“…While earlier work employed simplified approaches for the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution in the fits to data at various scales, the focus has moved to employ TMD evolution in more recent works, especially in view of the B-factory data at Q 2 ∼ 100 The results for the transversity distributions from global fits are of the same sign 18 as results for the helicity distribution, but somewhat smaller in magnitude, by as much as a factor of two for the d-quark distribution. Flavor decompositions of the collinear transversity distribution, based on analysis of dihadron production in semi-inclusive deep-inelastic scattering [127][128][129], e + e − annihilation [130], and more recently in p ↑ p collision [131], confirm this general behavior [132][133][134][135]. In general, the d-quark transversity distribution is much less constrained, given the u-quark dominance in many of the processes employed in the extractions.…”

Transverse spin effects in hard semi-inclusive collisions

“…The available data on h q 1 (x) cover only a limited region in x, so that one needs some extrapolation in order to compute the full integral of Eq. (101); at the moment, there seems to be a discrepancies between the value of δu, as obtained from the extracted h u 1 (x), and the lattice results [228,229,230,231]. A very recent global analysis of data on Transverse Single Spin Asymmetries [232] includes, for the first time, results on the single spin asymmetry A N in p ↑ p scattering and sees less tension with the lattice results.…”

Origin of single transverse-spin asymmetries in high-energy collisions

“…ðzÞ at Q 2 ¼ 4 GeV 2 from our (JAM20) global analysis (red solid curves with 1-σ CL error bands). The functions from other groups [82,95,102,103,106,115,119,120] are also shown.…”

“…The individual flavor charges δq ≡ R 1 0 dx½h q 1 ðxÞ − hq 1 ðxÞ are shown along with the isovector combination g T ≡ δu − δd. We compare our results to those from lattice QCD computations at the physical point [121][122][123], other phenomenological extractions [82,95,115,119,120,124,125], and a calculation using Dyson-Schwinger equations [126]. From Fig.…”