arXiv subjects

HAPS Collaboration

Publications and source records attributed to HAPS Collaboration.

3 recordsLinked to original sources

arXiv2026

Modern Determination of Pion and Kaon Fragmentation Functions from SIA and High-Precision COMPASS SIDIS Multiplicities

We present a combined determination of charged-pion and charged-kaon fragmentation functions (FFs), denoted HAPS-PiFF1.0 and HAPS-KaFF1.0, at next-to-leading order (NLO) and within a next-to-next-to-leading-order (NNLO) perturbative QCD setup. The analysis combines single-inclusive electron-positron annihilation (SIA) data with charge-separated semi-inclusive deep-inelastic-scattering (SIDIS) multiplicities from HERMES and COMPASS. A central goal of this work is to incorporate the modern COMPASS SIDIS input, namely the COMPASS 2025 proton-target multiplicities and the COMPASS 2026 revised isoscalar-target multiplicities, into a common charged-pion and charged-kaon FF analysis and to assess their role in the resulting flavor separation. The revised isoscalar data supersede the earlier COMPASS measurements used in previous global fits. The charge-separated pion multiplicities provide important constraints on favored and unfavored light-quark fragmentation, while the kaon measurements enhance the sensitivity to light-quark, unfavored, and strange-to-kaon fragmentation channels. In both analyses, the gluon FF remains indirectly constrained in the present SIA+SIDIS framework and should be interpreted with appropriate caution. The extractions are carried out using the publicly available MontBlanc framework, and the resulting HAPS-PiFF1.0 and HAPS-KaFF1.0 replica sets are provided in the standard LHAPDF format.

hep-ph↗

arXiv2026

Revisiting Unidentified Charged-Hadron Fragmentation Functions with Modern COMPASS SIDIS Multiplicities

We present \texttt{HAPS-hFF1.0}, a new global QCD analysis of unidentified charged-hadron fragmentation functions (FFs) using single-inclusive electron-positron annihilation (SIA) data together with the modern COMPASS semi-inclusive deep-inelastic scattering (SIDIS) multiplicities. The COMPASS input consists of the 2025 proton-target measurement and the revised isoscalar-target multiplicities provided in the COMPASS addendum 2026. The extraction is performed at both next-to-leading order (NLO) and next-to-next-to-leading order (NNLO), allowing us to study the perturbative stability of the QCD fit and the impact of the updated SIDIS information on the flavor structure of the FFs. We find that the modern COMPASS multiplicities can be consistently described together with the SIA data and provide important charge-separated constraints on the light-quark and antiquark FFs. The comparison between the NLO and NNLO extractions indicates a stable quark-sector determination, while the gluon FF remains less directly constrained in the present SIA+SIDIS analysis. Our results highlight the importance of the modern COMPASS SIDIS multiplicities for precision studies of unidentified charged-hadron fragmentation and for future global FF determinations. The resulting \texttt{HAPS-hFF1.0} replicas are publicly available in standard LHAPDF format.

hep-ph↗

arXiv2026

Toward Precision Helicity PDFs from Global DIS and SIDIS Fits with Projected EIC Measurements

We present a new global determination of the helicity-dependent parton distribution functions (PDFs) of the proton, based on inclusive deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data within a consistent next-to-leading order (NLO) QCD framework. In addition to existing measurements, we incorporate simulated pseudodata for the future Electron-Ion Collider (EIC), considering two beam-energy configurations, $E_e \times E_p = 5 \times 41~\mathrm{GeV^2}$ and $18 \times 275~\mathrm{GeV^2}$, corresponding to an extended kinematic reach down to $x \sim 10^{-5}$. We focus on longitudinal double-spin asymmetries $A_1^h$ for charge-separated pion and kaon production in SIDIS off a longitudinally polarized proton target. These projected measurements significantly improve the flavor separation of sea-quark polarized PDFs ($\Delta \bar{u}$, $\Delta \bar{d}$, $\Delta s$) and reduce the uncertainties on both quark and gluon helicity distributions, with the largest impact at small $x$. Polarized PDFs are extracted using a neural-network parametrization and a Monte Carlo replica methodology to propagate experimental uncertainties, while theoretical constraints such as positivity are imposed during the fit. We demonstrate that the inclusion of EIC pseudodata leads to a substantially more precise determination of polarized PDFs, with the largest impact in the small-$x$ region. The resulting polarized PDF sets are provided in the LHAPDF format.

hep-ph↗