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 + () g0 u/2 + () 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.