A couple of slides on rare decays Stefan Leupold MesonNet, Prague, - - PowerPoint PPT Presentation

Stefan Leupold ω decays

A couple of slides on rare ω decays

Stefan Leupold MesonNet, Prague, June 2013

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Stefan Leupold ω decays

Motivation

for g − 2 of muon and — not to forget — to learn more about the challenging part of QCD we are interested in 2-γ physics: hadron(s) ↔ γ(∗) γ(∗) if, for instance, mγ∗ = mω (or mφ, . . . ) ֒ → related to decays ω → γ(∗)+ hadron(s)

• 1. for hadron = π0

related to transition form factor ω → π0 + l+l− (with lepton l)

• 2. for hadron = 2π0

related to rare decay ω → π0π0γ

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Stefan Leupold ω decays

Transition form factor

0.1 0.2 0.3 0.4 0.5 0.6 1 10 100 √s [GeV] |Fωπ0(s)|2

NA60 ’09 [8] NA60 ’11 [9] Lepton-G [7] VMD Terschl¨ usen et al. [34] f1(s) = a Ω(s) full dispersive

figure from Schneider/Kubis/Niecknig, PhysRevD.86.054013 note the log scale!

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Stefan Leupold ω decays

Transition form factor

0.1 0.2 0.3 0.4 0.5 0.6 1 10 100 √s [GeV] |Fωπ0(s)|2

NA60 ’09 [8] NA60 ’11 [9] Lepton-G [7] VMD Terschl¨ usen et al. [34] f1(s) = a Ω(s) full dispersive

figure from Schneider/Kubis/Niecknig, PhysRevD.86.054013 note the log scale!

can theory understand the high-mass part of this spectrum? so far: no can one (re)measure the high-mass part of this spectrum with complete reconstruction of final state? so far: no?

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Stefan Leupold ω decays

Rare ω decay

ω → π0π0γ branching ratio: 6.6 · 10−5 differential data from CMD2 (Akhmetshin et al., Phys.Lett.B580, 119 (2004))

2 4 6 8 10 12 14 16 18 20 250 300 350 400 450 500 550 600 650 700

M(π0π0), MeV/c2 Events/ 20 MeV/c2

histograms are simulations with an in- termediate rho (full) or sigma meson (dotted)

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