Measurement of theKLCharge Asymmetry

Abstract

We present a measurement of the charge asymmetry δ L in the mode K L → π ± e ∓ ν based on 298 million analyzed decays. We measure a value of δ L = (3322 ± 58(stat) ± 47(sys)) · 10 −6 , in good agreement with previous measurements and 2.4 times more precise than the current best published result. The result is used to place more stringent limits on CPT and ∆S = ∆Q violation in the neutral kaon system. PACS numbers: 11.30. Er, 13.25.Es, The charge asymmetry in K L semileptonic decays is deeply related to CP violation through neutral kaon mixing. TheBR(e + π − ) + BR(e − π + ) . Assuming ∆S = ∆Q and no CPT violation in the decayTo first order in the parameters that violate CP and CPT,The terms Y and Re(x −x) parameterize CPT violation in the ∆S = ∆Q and ∆S = −∆Q transitions respectively[1, 2]:In the Standard Model, the ∆S = ∆Q violation is CPTconserving and occurs in 2nd order weak decays. Estimates for |x| are in the range 10 −7 [3]. δ L is modified to order |x| 2 and will not be considered in this letter.

Hyperon semileptonic decays and quark spin content of the proton

“…Therefore to confirm or invalidate our analysis it is of utmost importance to have better data for these decays. Since we predict that (Ξ − → Σ 0 ) = (Ξ 0 → Σ + ) the forthcoming experimental result for the latter decay [34] will provide a test of our approach. If the future data on this and on other decays will disagree with the predictions of our analysis (in which dynamical quantities are fitted to the existing data rather than calculated in the model), that would also mean that the model (with dynamical quantities calculated) fails for these particular observables.…”

“…In Table II the yet unmeasured hyperon semileptonic decay constants are listed. The Ξ 0 → Σ + channel is particularly interesting, since its measurement will be soon announced by the KTeV collaboration [34].…”

The fundamental symmetries in the neutral kaon system—a pedagogical choice

“…(The new, more precise values of δ ℓ [103,104] do not change this conclusion). We note in passing [45] Re(y) = (0.5 ± 3.0) × 10 −3 .…”

“…This is confirmed by the experimental results (184) and (186). The experiment [103] has allowed one, in addition, to confirm the vanishing of their sum by the experimental determination of the lhs of Eq. (106) Re ( 2…”

Measurement of the charge asymmetry for the KS → πeν decay and test of CPT symmetry with the KLOE detector

“…At present, the most precise measurement of A L has been performed by the KTeV collaboration: A L = (3.322 ± 0.058 stat ± 0.047 syst ) × 10 −3 [14]. The measurement of its counterpart, A S , requires a very pure K S beam which can only be realised exploiting the entangled neutral kaons pairs produced at a φ-factory [15].…”