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Title: Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors

Abstract

A theoretical framework is suggested for the calculation of {gamma}* N {yields} {Delta} transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the ''soft'' contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The ''minus'' components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.

Authors:
; ; ;
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA
Sponsoring Org.:
USDOE - Office of Energy Research (ER)
OSTI Identifier:
892167
Report Number(s):
JLAB-THY-05-436; DOE/ER/40150-4055
TRN: US0605555
DOE Contract Number:
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review D; Journal Volume: 73
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; FORM FACTORS; HADRONS; LIGHT CONE; ORBITAL ANGULAR MOMENTUM; QUARKS; SUM RULES; VALENCE; WAVE FUNCTIONS

Citation Formats

V.M. Braun, A. Lenz, G. Peters, and A. Radyushkin. Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors. United States: N. p., 2006. Web. doi:10.1103/PhysRevD.73.034020.
V.M. Braun, A. Lenz, G. Peters, & A. Radyushkin. Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors. United States. doi:10.1103/PhysRevD.73.034020.
V.M. Braun, A. Lenz, G. Peters, and A. Radyushkin. Wed . "Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors". United States. doi:10.1103/PhysRevD.73.034020. https://www.osti.gov/servlets/purl/892167.
@article{osti_892167,
title = {Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors},
author = {V.M. Braun and A. Lenz and G. Peters and A. Radyushkin},
abstractNote = {A theoretical framework is suggested for the calculation of {gamma}* N {yields} {Delta} transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the ''soft'' contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The ''minus'' components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.},
doi = {10.1103/PhysRevD.73.034020},
journal = {Physical Review D},
number = ,
volume = 73,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2006},
month = {Wed Feb 01 00:00:00 EST 2006}
}
  • A theoretical framework is suggested for the calculation of {gamma}*N{yields}{delta} transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the soft contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The minus components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.
  • Light-cone sum rules for the {lambda}{sub b}{yields}p, {lambda} transition form factors are derived from the correlation functions expanded by the twist of the distribution amplitudes of the {lambda}{sub b} baryon. In terms of the {lambda}{sub b} three-quark distribution amplitude models constrained by the QCD theory, we calculate the form factors at small momentum transfers and compare the results with those estimated in the conventional light-cone sum rules (LCSR) and perturbative QCD approaches. Our results indicate that the two different versions of sum rules can lead to the consistent numbers of form factors responsible for {lambda}{sub b}{yields}p transition. The {lambda}{sub b}{yields}{lambda}more » transition form factors from LCSR with the asymptotic {lambda} baryon distribution amplitudes are found to be almost 1 order larger than those obtained in the {lambda}{sub b}-baryon LCSR, implying that the preasymptotic corrections to the baryonic distribution amplitudes are of great importance. Moreover, the SU(3) symmetry breaking effects between the form factors f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup p} and f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup {lambda}} are computed as 28{sub -8}{sup +14}% in the framework of {lambda}{sub b}-baryon LCSR.« less
  • We examine the radiative {delta}{yields}{gamma}N transition at the real photon point Q{sup 2}=0 using the framework of light-cone QCD sum rules. In particular, the sum rules for the transition form factors G{sub M}(0) and R{sub EM} are determined up to twist 4. The result for G{sub M}(0) agrees with experiment within 10% accuracy. The agreement for R{sub EM} is also reasonable. In addition, we derive new light-cone sum rules for the magnetic moments of nucleons, with a complete account of twist-4 corrections based on a recent reanalysis of photon distribution amplitudes.
  • We report the first systematic analysis of the off-light-cone effects in sum rules for heavy-to-light form factors. These effects are investigated in a model based on scalar constituents, which allows a technically rather simple analysis but has the essential features of the analogous QCD calculation. The correlator relevant for the extraction of the heavy-to-light form factor is calculated in two different ways: first, by adopting the full Bethe-Salpeter amplitude of the light meson and, second, by performing the expansion of this amplitude near the light cone x{sup 2}=0. We demonstrate that the contributions to the correlator from the light-cone termmore » x{sup 2}=0 and the off-light-cone terms x{sup 2}{ne}0 have the same order in the 1/m{sub Q} expansion. The light-cone correlator, corresponding to x{sup 2}=0, is shown to systematically overestimate the full correlator, the difference being {approx}{lambda}{sub QCD}/{delta}, with {delta} the continuum subtraction parameter of order 1 GeV. Numerically, this difference is found to be 10 divide 20%.« less