Soft spectator scattering in the nucleon form factors at large Q{sup 2} within the soft collinear effective theory approach

Journal Article · Sun May 01 04:00:00 EDT 2011 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.83.093005· OSTI ID:21541578

Kivel, Nikolai; Vanderhaeghen, Marc ^[1]

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1. Institut fuer Kernphysik, Johannes Gutenberg-Universitaet, D-55099 Mainz, Germany, Helmholtz Institut Mainz, Johannes Gutenberg-Universitaet, D-55099 Mainz, Germany, and Petersburg Nuclear Physics Institute, Gatchina, 188350 (Russian Federation)

The proton form factors at large momentum transfer are dominated by two contributions which are associated with the hard and soft rescattering, respectively. Motivated by a very active experimental form factor program at intermediate values of momentum transfers, Q{sup 2}{approx}5-15 GeV{sup 2}, where an understanding in terms of only a hard rescattering mechanism cannot yet be expected, we investigate in this work the soft rescattering contribution using soft collinear effective theory (SCET). Within such a description, the form factor is characterized, besides the hard scale Q{sup 2}, by a hard-collinear scale Q{Lambda}, which arises due to the presence of soft spectators, with virtuality {Lambda}{sup 2} ({Lambda}{approx}0.5 GeV), such that Q{sup 2}>>Q{Lambda}>>{Lambda}{sup 2}. We show that in this case a two-step factorization can be successfully carried out using the SCET approach. In a first step (SCET{sub I}), we perform the leading-order matching of the QCD electromagnetic current onto the relevant SCET{sub I} operators and perform a resummation of large logarithms using renormalization group equations. We then discuss the further matching onto a SCET{sub II} framework, and propose the factorization formula (accurate to leading logarithmic approximation) for the Dirac form factor, accounting for both hard and soft contributions. We also present a qualitative discussion of the phenomenological consequences of this new framework.

• OSTI ID: 21541578
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 9 Vol. 83; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACCOUNTING
APPROXIMATIONS
BARYONS
CALCULATION METHODS
DIMENSIONLESS NUMBERS
DIRAC FORM FACTORS
ELEMENTARY PARTICLES
ENERGY RANGE
EQUATIONS
FACTORIZATION
FERMIONS
FIELD THEORIES
FORM FACTORS
GEV RANGE
GEV RANGE 01-10
HADRONS
MOMENTUM TRANSFER
NUCLEONS
PARTICLE PROPERTIES
PROTONS
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
RENORMALIZATION
RESCATTERING
SCATTERING