Froissart-Martin bound forππscattering in QCD

Abstract

The Froissart-Martin bound for total ππ scattering cross sections is reconsidered in the light of QCD properties such as spontaneous chiral symmetry breaking and the counting rules for a large number of colours N c .

Asymptotic behaviour of pion-pion total cross-sections

“…of eq. (1.3) has recently been questioned by two of us [5]: what happens to the FML-bound in QCD in the chiral limit when the…”

What does Holographic QCD predict for anomalous (g− 2)μ?

“…Another caveat is that, although large values of the magnetic susceptibility χ 0 are disfavored, in the absence of stronger bounds on χ 0 , an additional (10 − 15)% systematic uncertainty on the previous value for a π 0 μ cannot be excluded. Modified ENJL [26][27][28] 59(9) VMD/HLS [29][30][31][32] 57(4) VMD+V (h 2 = 0) [33] 58(10) VMD+V (h 2 = −10 GeV 2 ) [33] 63(10) VMD+V (const.F π 0 γ * γ ) [37] 77(7) DSE [34,36] 58(7) Non local χQM [38] 65(2) AdS/QCD [21,39] 69 AdS/QCD/DIP [2] 65.4(2.5) RχT [40] 65.8(1.2) CχQM [41] 68(3) Table 3 shows a partial list of values of a π 0 μ obtained using different models, some of them discussed in other talks at this conference. Our numerical analysis showed also that the values of χ 0 hovered around 2 GeV −2 , as in the case shown in (18), with higher values disfavored although not definitely excluded.…”

Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ0→γγdecay width and theγ*γ→π0transition form factor with the KLOE-2 experiment

“…LbyL µ = (116 ± 40) × 10 −11 [4,1] rely entirely on calculations using hadronic models which employ form factors for the interaction of hadrons with photons. The more recent papers [5,6] yield a larger central value and a larger error of about (150 ± 50) × 10 −11 . For a brief review of had.…”

“…[10] have been performed with the dedicated Monte-Carlo program EKHARA [11] for the process e + e − → e + e − γ * γ * → e + e − P with P = π 0 , η, η , followed by the decay π 0 → γγ and combined with a detailed detector simulation. a e-mail: nyffeler@hri.res.in 1 Apart from the recent papers [5,6], where the (dressed) quark loop gives the largest contribution.…”