QCD factorization with multihadron fragmentation functions

Journal Article · 03 March 2025 · Physical Review. D.

DOI: https://doi.org/10.1103/physrevd.111.056001 · OSTI ID:2526271

Rogers, T.  C.  ^[1]; Radici, Marco  ^[2]; Courtoy, Aurore  ^[3]; Rainaldi, T.  ^[4]

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1. Old Dominion Univ., Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2. Istituto Nazionale di Fisica Nucleare (INFN), Pavia (Italy). Sezione di Pavia
3. Univ. Nacional Autonoma de Mexico (UNAM), Mexico City (Mexico)
4. Old Dominion Univ., Norfolk, VA (United States)

Important aspects of quantum chromodynamics (QCD) factorization theorems are the properties of the objects involved that can be identified as universal. One example is that the definitions of parton densities and fragmentation functions for different types of hadrons differ only in the identity of the nonperturbative states that form the matrix elements, but are otherwise the same. This leads to independence of perturbative calculations on nonperturbative details of external states. It also lends support to interpretations of correlation functions as encapsulations of intrinsic nonperturbative properties. These characteristics have usually been presumed to still hold true in fragmentation functions even when the observed nonperturbative state is a small-mass cluster of n hadrons rather than simply a single isolated hadron. However, the multidifferential aspect of cross sections that rely on these latter types of fragmentation functions complicates the treatment of kinematical approximations in factorization derivations. That has led to recent claims that the operator definitions for fragmentation functions need to be modified from the single hadron case with nonuniversal prefactors. With such concerns as our motivation, we retrace the steps for factorizing the unpolarized semi-inclusive e⁺⁢ e^- annihilation cross section and confirm that they do apply without modification to the case of a small-mass multihadron observed in the final state. In particular, we verify that the standard operator definition from single hadron fragmentation, with its usual prefactor, remains equally valid for the small-mass n-hadron case with the same hard parts and evolution kernels, whereas the more recently proposed definitions with nonuniversal prefactors do not. Our results reaffirm the reliability of most past phenomenological applications of dihadron fragmentation functions.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: Consejo Nacional de Humanidades, Ciencias, y Tecnologías (CONAHCYT); UNAM Dirección General de Asuntos del Personal Académico (DGAPA); USDOE Office of Science (SC), Nuclear Physics (NP)
• Grant/Contract Number: AC05-06OR23177; SC0024715
• OSTI ID: 2526271
• Report Number(s): DOE/OR/23177-7749; JLAB-THY--24-4246
• Journal Information: Physical Review. D., Journal Name: Physical Review. D. Journal Issue: 5 Vol. 111; ISSN 2470-0010
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English