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 |
Dalitz plot linear slope asymmetry in 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:
Left: Normalized distribution of the selected events in the kinematical variables (u,|v|), right: u spectrum of the selected events. ( .eps, .jpg)
Spectra of reconstructed 3pi masses corresponding to K+ ( .eps, .jpg) and K- ( .eps, .jpg) decays. Dark areas indicate events with a muon identified by muon veto system.
Fitted quadruple ratios R_4(u) for (a) supersample 0 ( .eps, .jpg); (b) supersample 1 ( .eps, .jpg); (c) supersample 2 ( .eps, .jpg); (d) supersample 3 ( .eps, .jpg).
(a) Delta g measurement in the four supersamples; control quantities (b) Delta g_{LR} and (c) Delta g_{UD} corresponding to detector and beam line asymmetries which cancel in quadruple ratio, and their comparison to Monte Carlo. ( .eps, .jpg)
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:
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:
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:
Invariant mass distribution of reconstructed pi+/- pi0 pi0 candidate events ( .eps, .jpg)
Distribution of M^2_{00}, the square of the pi0 pi0 invariant mass ( .eps, .jpg)
(a) Expected M_{00} resolution versus generated M^2_{00}, together with M^2_{00} distributions for five generated values of M^2_{00}; (b) Acceptance versus M^2_{00} ( .eps, .jpg)
(data - fit)/data versus M^2_{00} for various theoretical models: (a) using the simple charge-exchange model; (b) fit to the rescattering model; (c) fit to the model including pionium formation; (d) fit to the rescattering model excluding a 7 bin wide interval centered at M^2_{00}= (2m_+)^2 ( .eps, .jpg)
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:
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.k' = 0.0097 ± 0.0003 (stat) ± 0.0008 (syst)