Conveners: I.Mikulec, M.Sozzi

Status Working Group Presentations
Charged
3pi asymmetry 		2003 result - published
2003+2004 - preliminary 
result reported 		E.Goudzovski
I.Mikulec
F.Marchetto 		Link
Neutral
3pi asymmetry 		2003 result - published
2003+2004 - in progress 		S.Balev
M.Wache
GL.Lamanna
S.Giudici 		Link
Cusp effect 2003 result - published I.Mannelli
L.DiLella
N.Cabibbo
D.Madigozhin
S.Giudici 		Link

Charged 3pi asymmetry 

Dalitz plot linear slope asymmetry in $K^{\pm}\rightarrow \pi^+ \pi^- \pi^{\pm}$ decays

Published final 2003 result 
(full 2003 data sample of 1.67x10^9 events selected for analysis):

Ag = (1.7 ± 2.1 (stat) ± 1.4 (stat-trig) ± 1.4 (syst)) * 10-4 = (1.7 ± 2.9) * 10-4

in Physics Letters B 634 (2006) 474-482.

2003 Plots:

Public preliminary combined 2003+2004 result 
(adding the full 2004 data sample of 1.45x10^9 events selected for analysis):

Ag = (-1.3 ± 1.5 (stat) ± 0.9 (stat-trig) ± 1.4 (syst)) * 10-4 = (-1.3 ± 2.3) * 10-4

first presented by E. Goudzovski at La Thuile 2006.

2004 Plots:

Neutral 3pi asymmetry 

Dalitz plot linear slope asymmetry in $K^{\pm}\rightarrow \pi^0 \pi^0 \pi^{\pm}$ decays

Published final 2003 result (full 2003 data sample of 47.1x10^6 events selected for analysis):

Ag = (1.8 ± 2.2 (stat) ± 1.0 (stat-trig) ± 0.8 (syst) ± 0.2 (ext.)) * 10-4 = (1.8 ± 2.6) * 10-4

in Physics Letters B 638 (2006) 22-29.

2003 Plots:

Public preliminary combined 2003+2004 result 
(adding 2004 data sample excluding SS4. Additional ststistics SS5-SS8: 44.2x10^6 events selected for analysis):

Ag = (2.1 ± 1.6 (stat) ± 1.0 (syst) ± 0.2 (ext)) * 10-4 = (2.1 ± 1.9) * 10-4

2004 Plots:

Cusp effect

Published 2003 result: based on the improved Cabibbo-Isidori theoretical framework, obtained from a uni-dimensional fit to the squared pi0-pi0 invariant mass in which the quadratic Dalitz plot slope parameter k is set to 0 (as suggested by PDG 2005), the scattering length difference is

(a0-a2) m(pi+) = 0.268 ± 0.010 (stat) ± 0.004 (syst) ± 0.013 (ext)

a2 m(pi+) = -0.041 ± 0.022 (stat) ± 0.014 (syst)

or

(a0-a2) m(pi+) = 0.264 ± 0.006 (stat) ± 0.004 (syst) ± 0.013 (ext)

if the correlation between a0 and a2 predicted by Chiral Perturbation Theory is taken into account.

From the same fit the following slope parameters are extracted:

g0 = 0.645 ± 0.004 (stat) ± 0.009 (syst)

h' = -0.047 ± 0.012 (stat) ± 0.011 (syst)

corresponding to the functional form M0 = 1 + (½) g0 u/2 + (½) h' u^2 for the matrix element.

These results appear in Physics Letters B 633 (2006) 173-182.

2003 Plots:

Update to 2003 result: clear evidence for a non-zero k parameter of order 1% is found. This has negligible effect on the scattering length difference, but more significant effect on slope parameters.
On the meeting 5 jul 2006 we decided to release a quantitative preliminary result based on 2003 data:

k' = 0.0097 ± 0.0003 (stat) ± 0.0008 (syst)

The parameter of the v^2 term is called here k' as it is defined at the amplitude and hence does not correspond to the classical PDG definition of k.
Analysis within the Colangelo-Gasser-Kubis-Rusetsky theoretical framework is in progress.