TY  - JOUR
AU  - Gisbert, H.
AU  - Pich, A.
PY  - 2018
DA  - 2018//
TI  - Direct CP violation in K-0 -> pi pi : Standard Model Status
T2  - Rep. Prog. Phys.
JO  - Reports on Progress in Physics
SP  - 076201
EP  - 22pp
VL  - 81
IS  - 7
PB  - Iop Publishing Ltd
KW  - Kaon decays
KW  - CP violation
KW  - Standard Model
AB  - In 1988 the NA31 experiment presented the first evidence of direct CP violation in the K-0 -> pi pi decay amplitudes. A clear signal with a 7.2 sigma statistical significance was later established with the full data samples from the NA31, E731, NA48 and KTeV experiments, confirming that CP violation is associated with a Delta S = 1 quark transition, as predicted by the Standard Model. However, the theoretical prediction for the measured ratio epsilon'/epsilon has been a subject of strong controversy along the years. Although the underlying physics was already clarified in 2001, the recent release of improved lattice data has revived again the theoretical debate. We review the current status, discussing in detail the different ingredients that enter into the calculation of this observable and the reasons why seemingly contradictory predictions were obtained in the past by several groups. An update of the Standard Model prediction is presented and the prospects for future improvements are analysed. Taking into account all known short-distance and long-distance contributions, one obtains Re (epsilon' / epsilon) = (15 +/- 7) . 10(-4), in good agreement with the experimental measurement.
SN  - 0034-4885
UR  - http://arxiv.org/abs/1712.06147
UR  - https://doi.org/10.1088/1361-6633/aac18e
DO  - 10.1088/1361-6633/aac18e
LA  - English
N1  - WOS:000436545600001
ID  - Gisbert+Pich2018
ER  -