The CP-violating asymmetry in KL→π+π−e+e−

Ecker, Gerhard; Pichl, H.

doi:10.1016/s0370-2693(01)00373-2

Cited by 9 publications

(9 citation statements)

References 28 publications

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“…Theorectally, P violation and CP violation in the decay of η → π + π − γ have been discussed by Herczeg and Singer [9] nearly thirty years before; very recently, Geng, Ng, and Wu [10] studied the CP-violating effects in this decay by considering the photon polarizations, and they predicted that a sizable linear photon polarization could be expected in some unconventional new physics scenarios. In the neutral K system, a large CP asymmetry, which arises from the interference between the parity-conserving magnetic amplitudes and the parity-violating electric amplitudes of K L → π + π − γ * → π + π − e + e − , has been predicted theoretically by many authors [11,12,13] and confirmed experimentally [14,2]. The purpose of this paper is to extend the above analyses to the decay of η → π + π − γ * → π + π − e + e − , thus to probe possible new CP-violating effects in η factories.…”

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confidence: 97%

THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-

Gao

2002

Mod. Phys. Lett. A

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We study the CP-violating asymmetry A CP , which arises, in η → π + π − e + e − , from the angular correlation of the e + e − and π + π − planes due to the interference between the magnetic and electric decay amplitudes. With the phenomenologically determined magnetic amplitude and branching ratio as input, the asymmetry, induced by the electric bremsstrahlung amplitude through the CP-violating decay η → π + π − , and by an unconventional tensor type operator, has been estimated respectively. The upper bound of A CP from the former is about 10 −3 , and the asymmetry from the latter might be up to O(10 −2 ). One can therefore expect that this CP asymmetry would be an interesting CP-violating observable for the future precise measurements in the η factories. †

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confidence: 97%

THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-

Gao

2002

Mod. Phys. Lett. A

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“…The possibility to probe CP violation effects through the polarization of the photon in the K 0 → π + π − γ * process as well as the recent experimental progress achieved in this field have aroused considerable theoretical interest [9,10,15,16,17,18,19,20,21] and stimulated several calculations based on chiral perturbation theory [22,23]. We present in this paper the results from a study of the K L → π + π − e + e − and K S → π + π − e + e − decay modes performed by the NA48 experiment at the CERN SPS.…”

Section: Introductionmentioning

confidence: 99%

Investigation of $K_\mathrm{L,S} \rightarrow \pi^+ \pi^{-} e^+ e^{-}$ decays

Lai¹,

Marras²,

Batley

et al. 2003

Eur. Phys. J. C

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decay modes have been studied in detail using the NA48 detector at the CERN SPS. Based on the data collected during the 1998 and 1999 run periods, a sample of 1162 K L → π + π − e + e − candidates has been observed with an expected background level of 36.9 events, yielding the branching ratio measurement BR(K L → π + π − e + e −)=(3.08 ± 0.20) × 10 −7. The distribution of events in the sinφ cosφ variable, where φ is the angle between the π + π − and the e + e − decay planes in the kaon centre of mass, is found to exhibit a large CP-violating asymmetry with the value A φ =(14.2 ± 3.6)%. For the K S → π + π − e + e − decay channel, 621 candidates have been identified in the 1999 data sample with an estimated background contribution of 0.7 event. The corresponding branching ratio has been determined to be BR(K S → π + π − e + e −) = (4.71 ± 0.32) × 10 −5. The combined value of this measurement with the published 1998 result is BR(K S → π + π − e + e −) = (4.69 ± 0.30) × 10 −5. No asymmetry is observed in this decay mode. Our results are in good agreement with theoretical predictions based on a phenomenological description of radiative kaon decays. The form factor parameters a 1 /a 2 andg M1 in the K L → π + π − e + e − direct emission process as well as the value of the K 0 charge radius have been extracted from the data.

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“…This interest focused on the decay width itself [1,2,3,4,5,6,7,8] and on the possibility of constructing CP-violating observables [1,2,3,4,7,8,9,10,11,12] as well as on other related topics [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…But as long as the polarization of the on-shell photon is not measured, this interference is not accessible. This is the reason why one looks directly to the decay with a lepton pair, since the angle between the two planes spanned by the pions and leptons can be used to construct a CP-violating observable [1,2,3,4,9,10].…”

Section: Introductionmentioning

confidence: 99%

$K\rightarrow \pi\pi e^+e^-$ decays and chiral low-energy constants

Pichl

2001

Eur. Phys. J. C

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The CP-violating asymmetry in KL→π+π−e+e−

Cited by 9 publications

References 28 publications

THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-

THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-

Investigation of $K_\mathrm{L,S} \rightarrow \pi^+ \pi^{-} e^+ e^{-}$ decays

$K\rightarrow \pi\pi e^+e^-$ decays and chiral low-energy constants

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The CP-violating asymmetry in KL→π+π−e+e−

Cited by 9 publications

References 28 publications

THE CP-VIOLATING ASYMMETRY IN η → π+ π-e+e-

THE CP-VIOLATING ASYMMETRY IN η → π+ π-e+e-

Investigation of $K_\mathrm{L,S} \rightarrow \pi^+ \pi^{-} e^+ e^{-}$ decays

$K\rightarrow \pi\pi e^+e^-$ decays and chiral low-energy constants

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THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-

THE CP-VIOLATING ASYMMETRY IN η → π⁺ π^-e⁺e^-