Abstract
Based on an integrated luminosity of 1.61 fb−1 e+e− collision data collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory, a search for the P- and CP-violating decay η → π+π− has been performed. Radiative ϕ → ηγ decay is exploited to access the η mesons. No signal is observed in the π+π− invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ(η → π+π−) < 4.9 × 10−6, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ(η → π+π−) < 4.4 × 10−6 at 90% confidence level.
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References
C. Jarlskog and E. Shabalin, How large are the rates of the CP-violating η, η′ → ππ decays?, Phys. Rev. D 52 (1995) 248 [INSPIRE].
H.-Y. Cheng, The Strong CP Problem Revisited, Phys. Rept. 158 (1988) 1 [INSPIRE].
C. Jarlskog and E. Shabalin, On searches for CP, T, CPT and C violation in flavour-changing and flavour-conserving interactions, Phys. Scripta T 99 (2002) 23.
E. Shabalin, Decays of η and η′ mesons caused by the weak interaction, Phys. Scripta T 99 (2002) 104.
T. Gutsche et al., CP-violating decays of the pseudoscalars η and η′ and their connection to the electric dipole moment of the neutron, Phys. Rev. D 95 (2017) 036022 [arXiv:1612.02276] [INSPIRE].
A.S. Zhevlakov, M. Gorchtein, A.N. Hiller Blin, T. Gutsche and V.E. Lyubovitskij, Bounds on rare decays of η and η′ mesons from the neutron EDM, Phys. Rev. D 99 (2019) 031703 [arXiv:1812.00171] [INSPIRE].
KLOE collaboration, Upper limit on the η → π+π− branching ratio with the KLOE detector, Phys. Lett. B 606 (2005) 276 [hep-ex/0411030] [INSPIRE].
LHCb collaboration, Search for the CP-violating strong decays η → π+π− and η′ (958) → π+π−, Phys. Lett. B 764 (2017) 233 [arXiv:1610.03666] [INSPIRE].
A. Gallo et al., DAΦNE status report, Conf. Proc. C 060626 (2006) 604 [INSPIRE].
KLOE collaboration, Measurement of the DAΦNE luminosity with the KLOE detector using large angle Bhabha scattering, Eur. Phys. J. C 47 (2006) 589 [hep-ex/0604048] [INSPIRE].
M. Adinolfi et al., The tracking detector of the KLOE experiment, Nucl. Instrum. Meth. A 488 (2002) 51 [INSPIRE].
M. Adinolfi et al., The KLOE electromagnetic calorimeter, Nucl. Instrum. Meth. A 482 (2002) 364 [INSPIRE].
KLOE collaboration, The trigger system of the KLOE experiment, Nucl. Instrum. Meth. A 492 (2002) 134 [INSPIRE].
F. Ambrosino et al., Data handling, reconstruction, and simulation for the KLOE experiment, Nucl. Instrum. Meth. A 534 (2004) 403 [physics/0404100] [INSPIRE].
A. Birnbaum, On the foundations of statistical inference, J. Am. Statist. Assoc. 57 (1962) 269.
A.L. Read, Presentation of search results: The CL(s) technique, J. Phys. G 28 (2002) 2693 [INSPIRE].
T. Junk, Confidence level computation for combining searches with small statistics, Nucl. Instrum. Meth. A 434 (1999) 435 [hep-ex/9902006] [INSPIRE].
S. Giovannella and S. Miscetti, Study of the e+e− → π0π0γ process using 2001/2002 data, KLOE note 212, http://www.lnf.infn.it/kloe/pub/knote/kn212.ps, (2006).
KLOE collaboration, Precise measurements of the eta and the neutral kaon meson masses with the KLOE detector, JHEP 12 (2007) 073 [arXiv:0710.5892] [INSPIRE].
KLOE-2 collaboration, Combined limit on the production of a light gauge boson decaying into μ+μ− and π+π−, Phys. Lett. B 784 (2018) 336 [arXiv:1807.02691] [INSPIRE].
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The KLOE-2 collaboration., Babusci, D., Berlowski, M. et al. Upper limit on the η → π+π− branching fraction with the KLOE experiment. J. High Energ. Phys. 2020, 47 (2020). https://doi.org/10.1007/JHEP10(2020)047
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DOI: https://doi.org/10.1007/JHEP10(2020)047