Article

# Improved dispersion relations for γγ→ππ

Departamento de Física, Universidad de Murcia, E-30071 Murcia, Spain

Physics Letters B (Impact Factor: 6.13). 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.

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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