In Phys. Lett. B 753, 629-638 (2016) [arXiv:1507.08188] the BESIII collaboration published a cross section measurement of the process $e^+e^-\to \pi^+ \pi^-$ in the energy range between 600 and 900 MeV. In this erratum we report a corrected evaluation of the statistical errors in terms of a fully propagated covariance matrix. The correction also yields a reduced statistical uncertainty for the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, which now reads as $a_\mu^{\pi\pi\mathrm{, LO}}(600 - 900\,\mathrm{MeV}) = (368.2 \pm 1.5_{\rm stat} \pm 3.3_{\rm syst})\times 10^{-10}$. The central values of the cross section measurement and of $a_\mu^{\pi\pi\mathrm{, LO}}$, as well as the systematic uncertainties remain unchanged.
Results of the BESIII measurement of the cross section $\sigma^{\rm bare}_{\pi^+\pi^-(\gamma_{\rm FSR})} \equiv \sigma^{\rm bare}(e^+e^-\rightarrow\pi^+\pi^-(\gamma_{\rm FSR}))$ and the squared pion form factor $|F_\pi|^2$. The errors are statistical only. The value of $\sqrt{s'}$ represents the bin center. The 0.9$\%$ systematic uncertainty is fully correlated between any two bins.
Results for the bare cross section $\sigma^\text{bare}_{\pi^+\pi^-}$ and the pion form factor together with their statistical uncertainties. The systematical uncertainties are given by 0.9% (see <a href="https://inspirehep.net/literature/1385603">arXiv:1507.08188</a>).
Bare cross section $\sigma^\mathrm{bare}(e^+e^-\to\pi^+\pi^-(\gamma_\mathrm{FSR}))$ of the process $e^+e^-\to\pi^+\pi^-$ measured using the initial state radiation method. The data is corrected concerning final state radiation and vacuum polarization effects. The final state radiation is added using the Schwinger term at born level.
We present an analysis of the decay $D^{+} \to K^{-} \pi^+ e^+ \nu_e$ based on data collected by the BESIII experiment at the $\psi(3770)$ resonance. Using a nearly background-free sample of 18262 events, we measure the branching fraction $\mathcal{B}(D^{+} \to K^{-} \pi^+ e^+ \nu_e) = (3.71 \pm 0.03 \pm 0.08)\%$. For $0.8<m_{K\pi}<1.0$ GeV/$c^{2}$ the partial branching fraction is $\mathcal{B}(D^{+} \to K^{-} \pi^+ e^+ \nu_e)_{[0.8,1]} = (3.33 \pm 0.03 \pm 0.07)\%$. A partial wave analysis shows that the dominant $\bar K^{*}(892)^{0}$ component is accompanied by an \emph{S}-wave contribution accounting for $(6.05\pm0.22\pm0.18)\%$ of the total rate and that other components are negligible. The parameters of the $\bar K^{*}(892)^{0}$ resonance and of the form factors based on the spectroscopic pole dominance predictions are also measured. We also present a measurement of the $\bar K^{*}(892)^{0}$ helicity basis form factors in a model-independent way.
The $S$-wave phase $\delta_{S}$ measured in the 12 $m_{K\pi}$ bins with statistical and systematic uncertainties. The systematic uncertainties include: (I) background fraction, (II) background shape, (III) the $\bar K_{0}^{*}(1430)^{0}$ mass and width, (IV) additional resonances, (V) tracking efficiency correction, (VI) PID efficiency correction.
Average form-factor products in the $K^{*}$-dominated region.
A measurement of the vector to pseudoscalar conversion decay $\phi \to \pi^0 e^+e^-$ with the KLOE experiment is presented. A sample of $\sim 9500$ signal events was selected from a data set of 1.7 fb$^{-1}$ of $e^+e^-$ collisions at $\sqrt{s} \sim m_{\phi}$ collected at the DA$\Phi$NE $e^+e^-$ collider. These events were used to obtain the first measurement of the transition form factor $| F_{\phi \pi^0}(q^2) |$ and a new measurement of the branching ratio of the decay: $\rm{BR}\,(\phi \to \pi^0 e^+e^-) = (\,1.35 \pm 0.05^{\,\,+0.05}_{\,\,-0.10}\,) \times 10 ^{-5}$. The result improves significantly on previous measurements and is in agreement with theoretical predictions.
KLOE measurement of the transition form factor $| F_{\phi \, \pi^0}(q^2) |$ of the $\phi \to \pi^0 e^+e^-$ decay.
The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the $\pi^0$ electromagnetic transition form factor slope parameter from $1.11\times10^{6}$ fully reconstructed $K^\pm \to \pi^\pm \pi^0_D, \pi^0_D \to e^+ e^-\gamma$ events is reported. The measured value $a = (3.68 \pm 0.57)\times10^{-2}$ is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.
Number of reconstructed data events and MC events as a function of the Dalitz kinematic variable $x=(M_{ee}/M_{\pi^0})^2$. The MC events are reweighted to correspond to a TFF slope a=0. The MC sample is not normalized to the size of the data. The values of $x$ quoted in the table are the barycenters of the 50 variable size bins.
The $e^+e^-\to K^+K^-$ cross section and charged-kaon electromagnetic form factor are measured in the $e^+e^-$ center-of-mass energy range ($E$) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb$^{-1}$ of data collected with the BABAR detector at the PEP-II $e^+e^-$ collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than $1/E^2$, and approaches the asymptotic QCD prediction. Production of the $K^+K^-$ final state through the $J/\psi$ and $\psi(2S)$ intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a model-independent determination of the relative phases between single-photon and strong amplitudes in $J/\psi$ and $\psi(2S)\to K^+K^-$ decays. The values of the branching fractions measured in the reaction $e^+e^- \to K^+K^-$ are shifted relative to their true values due to interference between resonant and nonresonant amplitudes. The values of these shifts are determined to be about $\pm5\%$ for the $J/\psi$ meson and $\pm15\%$ for the $\psi(2S)$ meson.
The $K^+K^-$ invariant-mass interval ($M_{K^+K^-}$), number of selected events ($N_{\rm sig}$) after background subtraction, detection efficiency ($\varepsilon$), ISR luminosity ($L$), measured $e^+e^-\to K^+K^-$ cross section ($\sigma_{K^+K^-}$), and the charged-kaon form factor ($|F_K|$). For the number of events and cross section. For the form factor, we quote the combined uncertainty. For the mass interval 7.5 - 8.0 GeV/$c^2$, the 90$\%$ CL upper limits for the cross section and form factor are listed.
We report the first observation of the Dalitz decay $\eta' \to \gamma e^+e^-$, based on a data sample of 1.31 billion $J/\psi$ events collected with the BESIII detector. The $\eta'$ mesons are produced via the $J/\psi \to \gamma \eta'$ decay process. The ratio $\Gamma(\eta' \to \gamma e^+ e^-)/\Gamma(\eta'\to\gamma\gamma)$ is measured to be $(2.13\pm0.09(\text{stat.})\pm0.07(\text{sys.}))\times10^{-2}$. This corresponds to a branching fraction ${\cal B}(\eta' \to \gamma e^+e^-)= (4.69 \pm0.20(\text{stat.})\pm0.23(\text{sys.}))\times10^{-4}$. The transition form factor is extracted and different expressions are compared to the measured dependence on the $e^+e^-$ invariant mass. The results are consistent with the prediction of the Vector Meson Dominance model.
Fitted ($n^{\text{obs}}_i$) and efficiency-corrected ($n^{\text{corr}}_i$) signal yields for the eight $M(e^+e^-)$ bins, and ratios ($r_i$). The uncertainties are statistical only.
Values of $|F|^2$ in each $M(e^+e^-)$ bin.
Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of $e^{+}e^{-}\rightarrow p\bar{p}$ at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal $(|G_{E}|= |G_{M}|)$. In addition, the ratio of electric to magnetic form factors, $|G_{E}/G_{M}|$, and $|G_{M}|$ are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at $\sqrt{s}=$ 2232.4 and 2400.0 MeV and a combined sample at $\sqrt{s}$ = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BaBar, improving the overall uncertainty by about 30\%. The $|G_{E}/G_{M}|$ ratios are close to unity and consistent with BaBar results in the same $q^{2}$ region, which indicates the data are consistent with the assumption that $|G_{E}|=|G_{M}|$ within uncertainties.
Summary of the Born cross section $\sigma_\text{Born}$, the effective FF $|G|$, and the related variables used to calculate the Born cross sections at the different c.m.energies $\sqrt{s}$, where $N_\text{obs}$ is the number of candidate events, $N_\text{bkg}$ is the estimated background yield, $\varepsilon^\prime=\varepsilon\times(1+\delta)$ is the product of detection efficiency $\varepsilon$ and the radiative correction factor $(1+\delta)$, and $L$ is the integrated luminosity. The first errors are statistical, and the second systematic.
We have measured the cross section $\sigma(e^+e^-\to\pi^+\pi^-\gamma(\gamma))$ at DA$\Phi$NE, the Frascati \phi-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 $0.592 < M_{\pi\pi} < 0.975$ GeV. For the latter we find $\Delta a^{\pi\pi}_\mu = (387.2\pm0.5_{\rm stat}\pm2.4_{\rm exp}\pm2.3_{\rm th})\times 10^{-10}$
Differential cross section for E+ E- --> PI+ PI- GAMMA (GAMMA).
Total cross section for E+ E- --> PI+ PI-.
Pion form factor.
The e+e- -> p anti-p cross section is determined over a range of p anti-p masses, from threshold to 4.5 GeV/c^2, by studying the e+e- -> p anti-p gamma process. The data set corresponds to an integrated luminosity of 232 fb^-1, collected with the BABAR detector at the PEP-II storage ring, at an e+e- center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, is measured for p anti-p masses below 3 GeV/c^2: its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c^2. We also measure J/psi -> p anti-p and psi(2S) -> p anti-p branching fractions and set an upper limit on Y(4260) -> p anti-p production and decay.
The cross section and effective form factor for E+ E- --> PBAR P.
The cross section and effective form factor for E+ E- --> PBAR P.
Cross sections for e^+e^- -> ppbar have been measured at 10 center-of-mass energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton electromagnetic form factors in the time-like region have been determined.
Cross section and proton form factor measurements. The cross section quoted is the lowest order cross section corrected for initial and final state radiation and coulomb effects.
We have measured the cross section $\sigma(e^+e^-\to \pi^+\pi^- \gamma)$ at an energy $W=m_\phi=1.02$ GeV with the KLOE detector at the electron-positron collider DA$\Phi$NE. From the dependence of the cross section on the invariant mass of the two-pion system, we extract $\sigma(e^+e^-\to \pi^+\pi^-)$ for the mass range $0.35<s<0.95$ GeV$^2$. From this result, we calculate the pion form factor and the hadronic contribution to the muon anomaly, $a_\mu$.
The differential cross section as a function of the invariant mass of the di-pion system in the angular region THETA(PIPI) <15 DEGREES or THETA(PIPI) >165 DEGREES and THETA(PI) in the region 0 to 180 DEGREES.
The physical cross section for E+ E- --> PI+ PI- including FSR and vacuum polarization effects.
The pion form factor with FSR and vacuum polarization effects removed.
We have measured the form factor ratios r_V = V(0)/A_1(0) and r_2 = A_2(0)/A_1(0) for the decay D_s^+ -> phi ell^+ nu_ell, phi -> K^+ K^-, using data from charm hadroproduction experiment E791 at Fermilab. Results are based on 144 signal and 22 background events in the electron channel and 127 signal and 34 background events in the muon channel. We combine the measurements from both lepton channels to obtain r_V = 2.27 +- 0.35 +- 0.22 and r_2 = 1.57 +- 0.25 +- 0.19.
With a vetor meson in the final state, there are four formfactors, V(Q2), A1(Q2), A2(Q2), A3(Q2). Charge conjugated states are understood.
The fermilab high-energy photoproduction experiment E687 provides a sample of approximately 90 events of the decay mode D + s → φμ + ν . The ratios of the form factors governing the decay are measured to be R v =1.8±0.9±0.2 and R 2 = 1.1±0.8±0.1, implying a polarization of Г 1 /Г t = 1.0±0.5±0.1 for the electron decay, consistent with our measurement of the form factor for the decay D + → K ∗0 μ + ν .
With a vetor meson in the final state, there are four formfactors, V(Q2), A1(Q2), A2(Q2), A3(Q2). Charge conjugated states are understood.
Neutral-kaon decays to π e ν were analysed to determine the q 2 dependence of the K 0 e3 electroweak form factor f + . Based on 365 612 events, this form factor was found to have a linear dependence on q 2 with a slope λ + =0.0245±0.0012 stat ±0.0022 syst .
The Q2 dependence of FORMFACTOR+ is usually approximated as: FORMFACTOR+(Q2) = CONST * ( 1 + Q2 * CONST(NAME=LAMBDA+)/M(C=PI)**2).
Fermilab experiment E835 has measured the cross section for the reaction p ̄ p→e + e − at s =11.63, 12.43, 14.40 and 18.22 GeV 2 . From the analysis of the 66 observed events new high-precision measurements of the proton magnetic form factor are obtained.
The measured cross section in the kinematic range defined by COS(THETA).
The proton magnetic form factor calculated assuming the equality of the electric and magnetic form factors.
The proton magnetic form factor calculated assuming a negligible electric contribution.
The cross section of the process e+e- -> pi+pi- has been measured using about 114000 events collected by the CMD-2 detector at the VEPP-2M e+e- collider in the center-of-mass energy range from 0.61 to 0.96 GeV. Results of the pion form factor determination with a 0.6% systematic uncertainty are presented. Implications for the hadronic contribution to the muon anomalous magnetic moment are discussed.
Updated measured values of the pion form factor and 'bare' cross section.
Tensor polarization observables (t20, t21 and t22) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)^2. The experiment was performed at the Jefferson Laboratory in Hall C using the electron HMS Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q^2 the deuteron charge form factors G_C and G_Q. They are in good agreement with relativistic calculations and disagree with pQCD predictions.
No description provided.
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The cross section for the reaction p¯p→e+e− has been measured at s=8.8, 10.8, 12.4, 13.1, and 14.4 GeV2 by Fermilab experiment E835. A non-magnetic spectrometer is used to identify the e+e− final states generated by the antiproton beam intersecting an internal hydrogen gas jet target. From the analysis of the 144 observed events, new high-precision measurements of the proton magnetic form factor for timelike momentum transfers are obtained.
No description provided.
Assuming ABS(FORMFACTOR(NAME=ELECTRIC)) = ABS(FORMFACTOR(NAME=MAGNETIC)).
Neglecting contribution for FORMFACTOR(NAME=ELECTRIC).
We report on a measurement of the tensor-analyzing power T20 in elastic electron-deuteron scattering in the range of four-momentum transfer from 1.8 to 3.2 fm-1. Electrons of 704 MeV were scattered from a polarized deuterium internal target. The tensor polarization of the deuterium nuclei was determined with an ion-extraction system, allowing an absolute measurement of T20. The data are described well by a non-relativistic calculation that includes the effects of meson-exchange currents.
No description provided.
The electromagnetic form factors of the neutron in the time-like region have been measured for the first time, from the threshold up to q 2 ⋟ 6 GeV 2 . The neutron magnetic form factor turns out to be larger than the proton one; the angular distribution suggests that for the neutron, at variance with the proton case, electric and magnetic form factors could be different. Further measurements are also reported, concerning the proton form factors and the Σ Σ production, together with the multihadronic cross section and the J / Γ branching ratio into n n .
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The SQRT(S) values with (C=NOMIN) and (C=SHIFT) correspond to the nominal energy and shifted energy analysis (see text of paper for details).
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The NEUTRON formfactor value are calculated in two hypotheses: GE = GM and GE = 0.
The uncertainty on the evaluated cross section is given by the quadratic combination of the statistical and systematic uncertainties.
Two samples of exclusive semileptonic decays, 579 B 0 → D ∗+ ℓ − ν ℓ events and 261 B 0 → D + ℓ − ν ℓ events, are selected from approximately 3.9 million hadronic Z decays collected by the ALEPH detector at LEP. From the reconstructed differential decay rate of each sample, the product of the hadronic form factor F (ω) at zero recoil of the D (∗)+ meson and the CKM matrix element | V cb | are measured to be F D ∗+ (1)|V cb | = (31.9 ± 1.8 stat ± 1.9 syst ) × 10 −3 , F D + (1)| V cb | = (27.8 ± 6.8 stat ± 6.5 syst ) × 10 −3 . The ratio of the form factors F D + (1) and F D ∗+ (1) is measured to be F D + (1) F D ∗+ (1) = 0.87 ± 0.22 stat ± 0.21 syst . A value of | V cb | is extracted from the two samples, using theoretical constraints on the slope and curvature of the hadronic form factors and their normalization at zero recoil, with the result | V cb | = (34.4 ± 1.6 stat ± 2.3 syst ± 1.4 th ) × 10 −3 . The branching fractions are measured from the two integrated spectra to be Br ( B 0 → D ∗+ ℓ − ν ℓ ) = (5.53 ± 0.26 stat ±0.52 syst ) %, Br ( B 0 → D ∗+ ℓ − ν ℓ ) = (2.35 ± 0.20 stat ± 0.44 syst ) %.
The formfactors are evaluated at zero recoil of D meson. Two different methods are used (see text for details). VCB is the KCM matrix element. The formfactor fitted to dependence: FF(OM) = FF(1)*(1-CONST*(OM-1)).
VCB is the KCM matrix element.
VCB is the KCM matrix element.
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From the measurement of e + e - pairs from the reaction p̄p→e + e - at the CERN-ISR, using an antiproton beam and a hydrogen jet target, we derived upper limits for the proton magnetic form factor in the time-like region at Q 2 ⋍8.9( GeV c ) 2 and Q 2 ⋍12.5( GeV c ) 2 .
No description provided.
We have observed $23.2 \pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> \mu^+ \nu_\mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> \phi \mu^+ \nu_\mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> \mu^+ \nu_\mu) / B(D_s^+ --> \phi \mu^+ \nu_\mu) =0.16 \pm 0.06 \pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 \pm 35 \pm 20 \pm 14 MeV$.
No description provided.
We present measurement of the π0γ*γ, ηγ*γ and η′γ*γ form factors. The π0-form factor is for the first time observed in the space-like region. The transition form factor of the η-meson is determined from its decay modes π+π−π0, π+π−γ and the neutral decay mode γγ. The decay of the η′ is observed in the decay channels ργ, ηπ+π− with η→γγ and in the four charged prong final state stemming from ηπ+π− with the η decaying into π+π−(π0/γ). All form factors agree well with a simple ρ-pole predicted by the vector meson dominance model and also with the QCD inspired Brodsky-Lepage model.
No description provided.
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