Search for CP violation in K0→3π0 decays

Abstract

Using data taken during the year 2000 with the NA48 detector at the CERN SPS, a search for the CP violating decay K S → 3π 0 has been performed. From a fit to the lifetime distribution of about 4.9 million reconstructed K 0 /K 0 → 3π 0 decays, the CP violating amplitude η 000 = A(K S → 3π 0 )/A(K L → 3π 0 ) has been found to be Re(η 000 ) = −0.002 ± 0.011 ± 0.015 and Im(η 000 ) = −0.003 ± 0.013 ± 0.017. This corresponds to an upper limit on the branching fraction of Br(K S → 3π 0 ) < 7.4 × 10 −7 at 90% confidence level. The result is used to improve knowledge of Re(ǫ) and the CPT violating quantity Im(δ) via the Bell-Steinberger relation.

Plate with a hole obeys the averaged null energy condition

“…A more detailed analysis [40] yields (within the statistical error) the same result. The formula (110) also shows that the uncertainty of Im(δ) is, at present, just a multiple of the one of φ η .…”

“…See [35], as well as [23,39], with [36] and [40], for a justification of the neglect of the other decay modes . (In Eq.…”

“…The other processes enter with the reduction factor Γ S / Γ L ≈ 580, and, given their abundances, can often be neglected [23,36,40]. What remains of the sum, is approximately Γ S η ππ , with η ππ defined by…”

“…We wish to remark that, given the constants |∆λ| and φ SW , the information contained in the mass and decay width differences (40,41) is identical to the one in δ.…”

Search for theKS→ 3π0decay with the KLOE detector

“…One of them is the K S → 3π 0 decay which, assuming the CPT invariance, allows one to investigate the CP -violating phase of the weak decay amplitude into I=1 final states. Despite several direct searches [2,3] and K S K L interference studies [4,5], this decay remains undiscovered and the best upper limit on the branching ratio BR(K S → 3π 0 ) < 1.2 · 10 −7 [3,7] is still two orders of magnitude larger than the predictions based on the Standard Model: BR(K S → 3π 0 ) ∼ 2 · 10 −9 [3]. In this article we briefly describe the search of the K S → 3π 0 decay based on the data sample gathered in 2004 -2005 …”