A precise new KLOE measurement of $F_π$ with ISR events and determination of $ππ$ contribution to $a_μ$ for [0.35,0.95] GeV$^2$
Federico Nguyen
备注:
5 pages, 4 figures, written contribution to the Proceedings of PHIPSI08, International Workshop on e+e- collisions from Phi to Psi, Laboratori Nazionali di Frascati (Roma) 7 - 10 April 2008
在DA $Φ$ NE $ϕ$工厂的KLOE实验已经使用初始状态辐射事件对π介子形状因子进行了新的精确测量,光子以小极角发射。给出了基于240 pb $^{-1}$的积分光度和在[0.35,0.95] GeV $^2$质量范围内提取$ππ$对$a_μ$贡献的结果,相对于已发表的KLOE结果,系统不确定性降低了。
英文摘要:
The KLOE experiment at the DA$Φ$NE $ϕ$-factory has performed a new precise measurement of the pion form factor using Initial State Radiation events, with photons emitted at small polar angle. Results based on an integrated luminosity of 240 pb$^{-1}$ and extraction of the $ππ$ contribution to $a_μ$ in the mass range [0.35,0.95] GeV$^2$ are presented, the systematic uncertainty is reduced with respect to the published KLOE result.
Combination of KLOE $σ\big(e^+e^-\rightarrowπ^+π^-γ(γ)\big)$ measurements and determination of $a_μ^{π^+π^-}$ in the energy range $0.10 < s < 0.95$ GeV$^2$
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 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…
Methods for measuring the absolute center-of-mass energy, $\sqrt{s}$, and its distribution, are investigated for future $e^+e^-$ Higgs-factory colliders using in situ $e^+e^-$ collisions. We emphasize the potential of an estimator based on the measurement of muon momenta that we denote $\sqrt{s}_p$. It can be determined with high precision in $e^+e^-$ to $μ^+μ^-$($γ$) events while being sensitive to effects from beam energy spread, beamstrahlung, initial-state radiation (ISR), final-state radiation (FSR), crossing angle, and detector resolution. The measurement precision is enabled by a high-p…