TY - JOUR
T1 - Model-independent constraints on hadronic form factors with above-threshold poles
AU - Caprini, Irinel
AU - Grinstein, Benjamín
AU - Lebed, Richard F.
N1 - Funding Information:
I. C. acknowledges support from the Ministry of Research and Innovation, Contract No. PN 16420101/2016. B. G. was supported by the U.S. Department of Energy under Grant No. DE-SC0009919. R. F. L. was supported by the U.S. National Science Foundation under Grant No. 1403891.
Publisher Copyright:
© 2017 American Physical Society.
PY - 2017/8/28
Y1 - 2017/8/28
N2 - Model-independent constraints on hadronic form factors, in particular those describing exclusive semileptonic decays, can be derived from the knowledge of field correlators calculated in perturbative QCD, using analyticity and unitarity. The location of poles corresponding to below-threshold resonances, i.e., stable states that cannot decay into a pair of hadrons from the crossed channel of the form factor, must be known a priori, and their effect, accounted for through the use of Blaschke factors, is to reduce the strength of the constraints in the semileptonic region. By contrast, above-threshold resonances appear as poles on unphysical Riemann sheets, and their presence does not affect the original model-independent constraints. We discuss the possibility that the above-threshold poles can provide indirect information on the form factors on the first Riemann sheet, either through information from their residues or by constraining the discontinuity function. The bounds on form factors can be improved by imposing, in an exact way, the additional information in the extremal problem. The semileptonic K→π ν and D→π ν decays are considered as illustrations.
AB - Model-independent constraints on hadronic form factors, in particular those describing exclusive semileptonic decays, can be derived from the knowledge of field correlators calculated in perturbative QCD, using analyticity and unitarity. The location of poles corresponding to below-threshold resonances, i.e., stable states that cannot decay into a pair of hadrons from the crossed channel of the form factor, must be known a priori, and their effect, accounted for through the use of Blaschke factors, is to reduce the strength of the constraints in the semileptonic region. By contrast, above-threshold resonances appear as poles on unphysical Riemann sheets, and their presence does not affect the original model-independent constraints. We discuss the possibility that the above-threshold poles can provide indirect information on the form factors on the first Riemann sheet, either through information from their residues or by constraining the discontinuity function. The bounds on form factors can be improved by imposing, in an exact way, the additional information in the extremal problem. The semileptonic K→π ν and D→π ν decays are considered as illustrations.
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U2 - 10.1103/PhysRevD.96.036015
DO - 10.1103/PhysRevD.96.036015
M3 - Article
AN - SCOPUS:85054521264
SN - 2470-0010
VL - 96
JO - Physical Review D
JF - Physical Review D
IS - 3
M1 - 036015
ER -