Improved dispersion relations for γγ→ππ

Departamento de Física, Universidad de Murcia, E-30071 Murcia, Spain; CONICET and Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 1, (1428) Buenos Aires, Argentina
Physics Letters B (Impact Factor: 6.02). 01/2008; 659(1-2):201-208. DOI: 10.1016/j.physletb.2007.11.030
Source: arXiv

ABSTRACT We perform a dispersive theoretical study of the reaction
γγ→ππ emphasizing the low
energy region. The large source of theoretical uncertainty to calculate
the γγ→ππ total cross
section for s≳0.5 GeV within the dispersive approach is removed.
This is accomplished by taking one more subtraction in the dispersion
relations, where the extra subtraction constant is fixed by considering
new low energy constraints, one of them further refined by taking into
consideration the f(980) region. This allows us to make
sharper predictions for the cross section for s≲0.8 GeV, below the
onset of D-wave contributions. In this way, were new more precise data
on γγ→ππ available one
might then distinguish between different parameterizations of the
ππ isoscalar S-wave. We also elaborate on the width of the σ
resonance to γγ and provide new values.

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