https://doi.org/10.1140/epja/i2011-11147-7
Regular Article - Theoretical Physics
Implications of unitarity and analyticity for the Dπ form factors
1
Centre for High Energy Physics, Indian Institute of Science, 560 012, Bangalore, India
2
Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125, Magurele, Romania
* e-mail: anant@cts.iisc.ernet.in
Received:
1
August
2011
Revised:
13
October
2011
Accepted:
10
November
2011
Published online:
28
November
2011
We consider the vector and scalar form factors of the charm-changing current responsible for the semileptonic decay D → πlν. Using as input dispersion relations and unitarity for the moments of suitable heavy-light correlators evaluated with Operator Product Expansions, including O(α s 2 ) terms in perturbative QCD, we constrain the shape parameters of the form factors and find exclusion regions for zeros on the real axis and in the complex plane. For the scalar form factor, a low-energy theorem and phase information on the unitarity cut are also implemented to further constrain the shape parameters. We finally propose new analytic expressions for the Dπ form factors, derive constraints on the relevant coefficients from unitarity and analyticity, and briefly discuss the usefulness of the new parametrizations for describing semileptonic data.
© SIF, Springer-Verlag Berlin Heidelberg, 2011
