We have measured the cross section $σ(e^+e^-\toπ^+π^-γ(γ))$ at DA$Φ$NE, the Frascati ϕ-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb$^{-1}$. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two pion states in the mass range $0.592 < M_{ππ} < 0.975$ GeV. For the latter we find $Δa^{ππ}_μ= (387.2\pm0.5_{\rm stat}\pm2.4_{\rm exp}\pm2.3_{\rm th})\times 10^{-10}$
Dalitz plot analysis of e+ e- --> pi0 pi0 gamma events at SQRT(s) ~ M(phi) with the KLOE detector
本文研究了用KLOE探测器在SQRT（s）~ M（phi）上采集的e+ e-> pi 0 pi 0 γ事例的Dalitz图。在双介子不变质量（Mpp）低于700 MeV的区域中，所研究的过程由非共振过程e+ e-> omega -> pi 0和omega --> pi 0 γ主导，而对于更高的Mpp值，辐射phi衰变到f0（980）是主导机制。使用不同的理论模型来拟合Dalitz图，同时考虑到sigma（600）的可能贡献。对于每个模型，我们提取f0（980）质量及其与pipi，KKbar和phi的耦合。
The measurement of the $σ(e^+e^-\rightarrow π^+π^-)$ cross section allows to determine the pion form factor $| F_π|^2$ and the two pion contribution to the muon anomaly $a_μ$. Such a measurement has been performed with the KLOE detector at $DAΦNE$, the Frascati $ϕ$-factory.The preliminary results on the combination of the last analysis (KLOE12) with two previous published (KLOE08, KLOE10) will be presented in the following.
The generic Hidden Local Symmetry (HLS) model has given rise to the BHLS$_2$ variant which introduces symmetry breaking in the vector meson sector; the central mechanism is a modification of the covariant derivative at the root of the HLS approach. However, the description of the Belle $τ$ dipion spectra is not satisfactory whereas the dealing with its annihilation sector ($e^+ e^- \rightarrow π^+ π^-/π^+ π^-π^0/ π^0 γ/ηγ/K^+ K^-/K_L K_S$) is optimum. This issue is solved by an additional breaking term allowing to include the $[π^0,η,η^\prime]$ system. This extension of the usual 't~Hooft dete…
We present a search for a new light vector boson, carrier of a "dark force" between WIMPs, with the KLOE detector at \DA$Φ$NE. We analyzed $e^+ e^- \to μ^+ μ^- γ$ ISR events corresponding to an integrated luminosity of $239$ pb$^{-1}$ to find evidence for the $e^+ e^- \to Uγ,\,\, U\toμ^+μ^-$ process. We found no $U$ vector boson signal and set a 90% CL upper limit on the ratio of the U boson and photon coupling constants between 1.6$\times10^{-5}$ to 8.6$\times10^{-7}$ in the mass region $520<M_{\rm U}<980$ MeV. A projection of the KLOE sensitivity for the $μμγ$ and $ππγ$ channels at full stat…
Dispersive analysis of the $π^+ π^-$ production at the CMD3 experiment and the compatibility with muon pair production measurement by KLOE2 and the pion form factor by JLAB
Department of Theoretical Physics, Institute of Nuclear Physics Rez near Prague, CAS, Czech Republic（捷克布拉格附近雷兹核物理研究所理论物理系）
Precision measurement of $σ(e^+e^-\rightarrowπ^+π^-γ)/σ(e^+e^-\rightarrow μ^+μ^-γ)$ and determination of the $π^+π^-$ contribution to the muon anomaly with the KLOE detector
The KLOE experiment at the $ϕ-factory$ DA$Φ$NE in Frascati is the first to have employed Initial State Radiation (ISR) to precisely determine the $e^+e^-\toπ^+π^-(γ)$ cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the $(g-2)$ of the muon, where a long standing 3$σ$ discrepancy is observed. I will review the ISR activity in KLOE in the last 18 years from the measurement of the hadronic cross section to the first direct determination of the time-like complex running $α(s)$ in the region below 1 GeV.
The 4.2$σ$ discrepancy between the standard model prediction for the muon anomalous magnetic moment $a_μ$ and the experimental result is accompanied by other anomalies. A crucial input for the prediction is the hadronic vacuum polarization $a_μ^{\rm HVP}$ inferred from $σ_{\rm had} =σ(e^+e^- \to\,$hadrons) data. However, the two most accurate determinations of $σ_{\rm had}$ from KLOE and BaBar disagree by almost 3$\,σ$. Additionally, the combined data-driven result disagrees with the most precise lattice determination of $a_μ^{\rm HVP}$ by $2.1\,σ$. We show that all these discrepancies could b…
The three precision measurements of the cross section $σ\big(e^+e^-\rightarrowπ^+π^-γ(γ)\big)$ using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for $σ\…
Previous studies have shown that the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking mechanisms, provides an Effective Lagrangian (BHLS) which encompasses a large number of processes within a unified framework; a global fit procedure allows for a simultaneous description of the e+ e- annihilation into the 6 final states $π^+ π^-$, $π^0 γ$, $ηγ$, $π^+ π^- π^0$, $K^+ K^-$, $K_l K_s$ and includes the dipion spectrum in the τ decay and some more light meson decay partial widths. The contribution to the muon anomalous magnetic moment $a_{th}$ of these annihilation cha…
Based on a sample of 300 million $K_S$ mesons produced in $ϕ\to K_L K_S$ decays recorded by the KLOE experiment at the DA$Φ$NE $e^+e^-$ collider we have measured the branching fraction for the decay $K_S \to πμν$. The $K_S$ mesons are identified by the interaction of $K_L$ mesons in the detector. The $K_S \to πμν$ decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of $K_L \to πμν$ decays. A fit to the reconstructed muon mass distribution finds $7223 \pm 180$ signal events…
We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the $Z$-boson mass. We include newest $e^+e^- \to$ hadrons cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant $π^+π^-$ channel. For the muon $(g-2)/2$, we find for the lowest-ord…
