K → π ν ν decay in the Standard Model
In the Standard Model, the master formula for
Br(K^{+}→ π^{+} ν ν) and
BR(K_{L}→ π^{0} ν ν)
correspond to the conventional separation of long and shortdistance parts
where
λ_{q}=V^{*}_{qs}V_{qd},
X_{t}=1.464 ± 0.041,
P_{u,c}=P_{c} +
δP_{u,c}=0.41±0.04 for
m_{c}=1.30±0.05,
I_{ν}^{+,0} is the phase space
integral.
Experimental data on K_{l3} branching ratios and formfactor slopes
permit to estimate the
ϰ coefficients very precisely
Using these values and CKM couplings from
CKMfitter and UTfIt collaborations,
we get in the SM
(see complete note)
The error on CKM matrix elements largely dominates, while those from LD
coefficients are negligible. The present experimental situation from
E787

and
is the
following
These values are expected to be improved by the planned experiments at
CERN and
JPARC (KEK E391a).
K → π ν ν decay beyond the Standard Model
Download Picture in eps format
Some reference of recent analyses about rare K decays beyond the SM;
MFV,
CMFV,
MSSM
(1,
2),
LHT
(1,
2),
331 ZīModel,
FourGeneration Model
(1,
2)
June 2010 by F. Mescia
&
C. Smith