### Conveners

#### Parallel Session 6 - Goldstone Boson WG

- Mario Antonelli (LNF)
- Sebastien Descotes-Genon (CNRS/Univ. Paris-Sud 11)
- Andreas Juettner (University of Southampton)
- Emilie Passemar (Indiana University/JLab)

Xu Feng
(Columbia University, New York)

7/2/15, 4:20 PM

Goldstone Boson Working Group

Talk

The rare kaon decays, K → πν¯ν, have attracted increasing interest during the past few
decades. As ﬂavor changing neutral current processes, these decays are highly suppressed in the standard model and thus provide ideal probes for the observation of new physics effects. As second-order weak interactions, the ultra-rare decays K → πν¯ν represent a signiﬁcant challenge in experiments. After 40...

Sinya Aoki
(Kyoto University)

7/2/15, 4:50 PM

Goldstone Boson Working Group

Talk

We discuss the fate of the axial U(1) symmetry in 2-flavor QCD, when the non-singlet chiral symmetries are recovered at finite temperature. We theoretically investigate the constraints on the eigenvalue density of the Dirac operator, derived from the non-singlet chiral symmetries among various multi-point correlation functions in the chiral limit. We show that the axial U(1) symmetry, broken...

Daniel Robaina
(Institute of Nuclear Physics, Mainz)

7/2/15, 5:10 PM

Goldstone Boson Working Group

Talk

We investigate the low-temperature phase of strongly interacting matter and the crossover region with two light flavors of quarks in Lattice QCD. Based on Chiral Ward Identities we test the applicability of a fixed-temperature chiral expansion given that chiral symmetry is spontaneously broken. It indicates that a sharp real-time excitation persists with the quantum numbers of the pion...

Aron Bernstein
(Massachusetts Institute of Technology, Cambridge)

7/2/15, 5:30 PM

Goldstone Boson Working Group

Talk

The pi^0 rightarrow gamma gamma decay rate is dominated by the QCD axial anomaly that is increased by approx 4.5% +- 1.0% by the mixing of the pi^0 wave function with the eta, eta^' mesons. This relatively large isospin breaking effect is proportional to the mass difference of the up and down quarks. It has been calculated in Chiral Perturbation Theory (ChPT) by three slightly different...

Ashot Gasparian
(North Carolina A&T State University, Greensboro)

7/2/15, 5:50 PM

Goldstone Boson Working Group

Talk

The neutral pion is the lightest strongly interacting particle in Nature. Therefore, the properties of $\pi^0$ decay are especially sensitive to the underlying fundamental symmetries of quantum chromodynamics (QCD). In particular, the pi^0 -> gamma gamma decay width is primarily defined by the spontaneous chiral symmetry breaking effect (chiral anomaly) in QCD. Theoretical activities in this...

Karol Kampf
(Charles University, Prague)

7/2/15, 6:10 PM

Goldstone Boson Working Group

Talk

In this talk I will present basic properties of the lightest meson, pi0. I will discuss its decay modes, mainly two photon decay, Dalitz decay and e+e- production and focus on its recent theoretical and experimental studies. Connection with the theoretical calculation of the hadronic light-by-light scattering contribution in the g-2 type experiment will be outlined.