Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider

Following updates in the compilation of e þ e − → hadrons data, this work presents reevaluations of the hadronic vacuum polarization contributions to the anomalous magnetic moments of the electron (a e), muon (a μ) and tau lepton (a τ), to the ground-state hyperfine splitting of muonium and also updates the hadronic contributions to the running of the QED coupling at the mass scale of the Z boson, αðM 2 Z Þ. Combining the results for the hadronic vacuum polarization contributions with recent updates for the hadronic light-bylight corrections, the electromagnetic and the weak contributions, the deviation between the measured value of a μ and its Standard Model prediction amounts to Δa μ ¼ ð28.02 AE 7.37Þ × 10 −10 , corresponding to a muon g − 2 discrepancy of 3.8σ.

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“…There have been a number of small data updates (see Refs. [41][42][43][44][45][46]) in other channels since Ref. [1].…”

Section: Other Channelsmentioning

confidence: 99%

g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

2020

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“…The total number of signal events is a free fit parameter. The fractions of the processes (11) in the sum are calculated using their measured cross sections [4,21,22] and the branching fractions of the decays φ, ρ, ω → ηγ [10]. The energy dependences of the cross sections for the processes (11) are shown in Fig.…”

Section: Event Selectionmentioning

confidence: 99%

“…The dominant contribution to the e + e − → ηηγ cross section in the energy region under study comes from the process e + e − → φη with the decay φ → ηγ . This process was well studied in the SND [3], CMD-3 [4], BABAR [5,6] and a email: l.v.kardapoltsev@inp.nsk.su (corresponding author) BESIII [7] experiments in the decay channel φ → K + K − . In this work, the main objective of the analysis is the search of other intermediate states.…”

Section: Introductionmentioning

confidence: 99%

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Study of the process $$e^+e^- \rightarrow \eta \eta \gamma $$ in the energy range $$\sqrt{s} = \text{1.17--2.00 }$$ GeV with the SND detector

et al. 2022

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The process $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb$$^{-1}$$ - 1 collected by the SND detector at the VEPP-2000 $$e^+e^-$$ e + e - collider. The $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\phi \eta $$ ϕ η intermediate state. Our result on the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is consistent with the $$e^+e^-\rightarrow \phi \eta $$ e + e - → ϕ η measurement in the $$\phi \rightarrow K^+ K^-$$ ϕ → K + K - mode. The search for radiative processes contributing to the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is performed, and no significant signal is observed.

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“…To calculate the expected number of events, we used the cross sections for the processes (8) measured in Refs. [19][20][21][22] and the ρ → π 0 γ , φ → π 0 γ , and ηγ branching ratios [23]. The contribution of the processes (9) estimated using Refs.…”

Section: Event Selectionmentioning

confidence: 99%

Study of the process $$e^+e^- \rightarrow \eta \pi ^0\gamma $$ in the energy range $$\sqrt{s} = {1.05-2.00}$$ GeV with the SND detector

et al. 2020

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The process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 $$\hbox {pb}^{-1}$$ pb - 1 collected by the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ e + e - collider. The $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\omega \eta $$ ω η intermediate state. The measured cross section of the subprocess $$e^+e^-\rightarrow \omega \eta \rightarrow \eta \pi ^0\gamma $$ e + e - → ω η → η π 0 γ is consistent with previous measurements in the $$e^+e^-\rightarrow \pi ^+\pi ^-\pi ^0\eta $$ e + e - → π + π - π 0 η mode. It is found, with a significance of $$5.6\sigma $$ 5.6 σ , that the process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ e + e - → η π 0 γ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. $$e^+e^-\rightarrow a_{0}(1450)\gamma $$ e + e - → a 0 ( 1450 ) γ , is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.

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Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider

Abstract: The process e + e − →K + K − η has been studied in the center-of-mass energy range from 1.59 to 2.007 GeV using the data sample of 59.5 pb −1 , collected with the CMD-3 detector at the VEPP-2000 e + e − collider in 2011,

Cited by 13 publications

References 29 publications

g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

Study of the process $$e^+e^- \rightarrow \eta \eta \gamma $$ in the energy range $$\sqrt{s} = \text{1.17--2.00 }$$ GeV with the SND detector

Study of the process $$e^+e^- \rightarrow \eta \pi ^0\gamma $$ in the energy range $$\sqrt{s} = {1.05-2.00}$$ GeV with the SND detector

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Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider

Abstract: The process e + e − →K + K − η has been studied in the center-of-mass energy range from 1.59 to 2.007 GeV using the data sample of 59.5 pb −1 , collected with the CMD-3 detector at the VEPP-2000 e + e − collider in 2011,

Cited by 13 publications

References 29 publications

g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

Study of the process $$e^+e^- \rightarrow \eta \eta \gamma $$ in the energy range $$\sqrt{s} = \text{1.17--2.00 }$$ GeV with the SND detector

Study of the process $$e^+e^- \rightarrow \eta \pi ^0\gamma $$ in the energy range $$\sqrt{s} = {1.05-2.00}$$ GeV with the SND detector

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Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider