Cargando…

The structure function of semi-inclusive heavy flavour decays in field theory

We consider the decay of a heavy flavour into an inclusive hadronic state X of invariant mass m_X small with respect to its energy E_X, m_X << E_X. The electron spectrum and the hadronic mass distribution in semileptonic b -> u decays, or the photon spectrum in b -> s gamma decays, all r...

Descripción completa

Detalles Bibliográficos
Autores principales: Aglietti, Ugo, Ricciardi, Giulia
Lenguaje:eng
Publicado: 2000
Materias:
Acceso en línea:https://dx.doi.org/10.1016/S0550-3213(00)00443-0
http://cds.cern.ch/record/431035
_version_ 1780895240436056064
author Aglietti, Ugo
Ricciardi, Giulia
author_facet Aglietti, Ugo
Ricciardi, Giulia
author_sort Aglietti, Ugo
collection CERN
description We consider the decay of a heavy flavour into an inclusive hadronic state X of invariant mass m_X small with respect to its energy E_X, m_X << E_X. The electron spectrum and the hadronic mass distribution in semileptonic b -> u decays, or the photon spectrum in b -> s gamma decays, all require, close to their endpoints, a control over this region. This region is affected both by non-perturbative phenomena related to the Fermi motion of the heavy quark and by perturbative soft gluon radiation in the final state (Sudakov form factor). Fermi motion can be described by the shape function f (m_*), which represents the distribution of the effective mass m_* of the heavy quark at disintegration time. We perform a factorization with a simple technique in order to consistently separate perturbative from non-perturbative effects. We find that the shape function, contrary to naive expectations, is not a physical distribution, as it is affected by substantial regularization scheme effects, controlling even the leading, double-logarithmic term. It factorizes, however, the bulk of non-perturbative effects in lattice-like regularizations. Some non-perturbative effects are present in the coefficient function even at leading twist, but they are expected to be suppressed on physical grounds. Finally, we clarify a controversial factor of 2 in the evolution kernel of the shape function.
id cern-431035
institution Organización Europea para la Investigación Nuclear
language eng
publishDate 2000
record_format invenio
spelling cern-4310352021-07-18T12:48:38Zdoi:10.1016/S0550-3213(00)00443-0http://cds.cern.ch/record/431035engAglietti, UgoRicciardi, GiuliaThe structure function of semi-inclusive heavy flavour decays in field theoryParticle Physics - PhenomenologyWe consider the decay of a heavy flavour into an inclusive hadronic state X of invariant mass m_X small with respect to its energy E_X, m_X << E_X. The electron spectrum and the hadronic mass distribution in semileptonic b -> u decays, or the photon spectrum in b -> s gamma decays, all require, close to their endpoints, a control over this region. This region is affected both by non-perturbative phenomena related to the Fermi motion of the heavy quark and by perturbative soft gluon radiation in the final state (Sudakov form factor). Fermi motion can be described by the shape function f (m_*), which represents the distribution of the effective mass m_* of the heavy quark at disintegration time. We perform a factorization with a simple technique in order to consistently separate perturbative from non-perturbative effects. We find that the shape function, contrary to naive expectations, is not a physical distribution, as it is affected by substantial regularization scheme effects, controlling even the leading, double-logarithmic term. It factorizes, however, the bulk of non-perturbative effects in lattice-like regularizations. Some non-perturbative effects are present in the coefficient function even at leading twist, but they are expected to be suppressed on physical grounds. Finally, we clarify a controversial factor of 2 in the evolution kernel of the shape function.We consider the decay of a heavy flavour into an inclusive hadronic state X of invariant mass m_X small with respect to its energy E_X, m_X << E_X. The electron spectrum and the hadronic mass distribution in semileptonic b -> u decays, or the photon spectrum in b -> s gamma decays, all require, close to their endpoints, a control over this region. This region is affected both by non-perturbative phenomena related to the Fermi motion of the heavy quark and by perturbative soft gluon radiation in the final state (Sudakov form factor).Fermi motion can be described by the shape function f (m*), which represents the distribution of the effective mass m* of the heavy quark at disintegration time. We perform a factorization with a simple technique in order to consistently separate perturbative from non-perturbative effects. We find that the shape function, contrary to naive expectations,is not a physical distribution, as it is affected by substantial regularization scheme effects, controlling even the leading, double-logarithmic term. It factorizes, however, the bulk of non-perturbative effects in lattice-like regularizations. Some non-perturbative effects are present in the coefficient function even at leading twist, but they are expected to be suppressed on physical grounds. Finally, we clarify a controversial factor of 2 in the evolution kernel of the shape function.hep-ph/0003146CERN-TH-2000-071DSF-T-7-00CERN-TH-2000-071DSF-T-2000-007oai:cds.cern.ch:4310352000-03-15
spellingShingle Particle Physics - Phenomenology
Aglietti, Ugo
Ricciardi, Giulia
The structure function of semi-inclusive heavy flavour decays in field theory
title The structure function of semi-inclusive heavy flavour decays in field theory
title_full The structure function of semi-inclusive heavy flavour decays in field theory
title_fullStr The structure function of semi-inclusive heavy flavour decays in field theory
title_full_unstemmed The structure function of semi-inclusive heavy flavour decays in field theory
title_short The structure function of semi-inclusive heavy flavour decays in field theory
title_sort structure function of semi-inclusive heavy flavour decays in field theory
topic Particle Physics - Phenomenology
url https://dx.doi.org/10.1016/S0550-3213(00)00443-0
http://cds.cern.ch/record/431035
work_keys_str_mv AT agliettiugo thestructurefunctionofsemiinclusiveheavyflavourdecaysinfieldtheory
AT ricciardigiulia thestructurefunctionofsemiinclusiveheavyflavourdecaysinfieldtheory
AT agliettiugo structurefunctionofsemiinclusiveheavyflavourdecaysinfieldtheory
AT ricciardigiulia structurefunctionofsemiinclusiveheavyflavourdecaysinfieldtheory