Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s} >$ 4.4 GeV, the processes $e^+e^- \rightarrow \omega \chi_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074 pb^{-1}$ near $\sqrt{s} =$ 4.42 GeV, a significant $\omega \chi_{c2}$ signal is found, and the cross section is measured to be $(20.9 \pm 3.2 \pm 2.5)\pb$. With $567 pb^{-1}$ near $\sqrt{s} =$ 4.6 GeV, a clear $\omega \chi_{c1}$ signal is seen, and the cross section is measured to be $(9.5 \pm 2.1 \pm 1.3) \pb$, while evidence is found for an $\omega \chi_{c2}$ signal. The first errors are statistical and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $\omega \chi_{c2}$ cross section, an enhancement is seen around $\sqrt{s} =$ 4.42 GeV. Fitting the cross section with a coherent sum of the $\psi(4415)$ Breit-Wigner function and a phase space term, the branching fraction $\mathcal{B}(\psi(4415)\to\omega\chi_{c2})$ is obtained to be of the order of $10^{-3}$.
Results on $e^+e^-\to \omega \chi_{c0}$. Shown in the table are the channels, the center-of-mass energy, the integrated luminosity $\mathcal{L}$, product of radiative correction factor, vacuum polarization factor, branching fraction and efficiency, $\mathcal{D}=(1+\delta)\frac{1}{|1-\Pi|^{2}}(\epsilon_{\pi}\mathcal{B}(\chi_{c0}\to\pi^+\pi^-)+\epsilon_{K}\mathcal{B}(\chi_{c0}\to K^+K^-))\mathcal{B}(\omega\to\pi^+\pi^{-}\pi^{0})\mathcal{B}(\pi^{0}\to\gamma\gamma)$ for $\omega\chi_{c0}$, number of observed events $N^{\rm {obs}}$, number of estimated background events $N^{\rm bkg}$, number of signal events $N^{\rm sig}$ determined as described in the text, Born cross section $\sigma^{\rm B}$(or upper limit at 90$\%$ C.L.) at each energy point.
Results on $e^+e^-\to \omega \chi_{c1}$. Shown in the table are the channels, the center-of-mass energy, the integrated luminosity $\mathcal{L}$, product of radiative correction factor, vacuum polarization factor, branching fraction and efficiency, $\mathcal{D}=(1 + \delta) \frac{1}{|1-\Pi|^{2}} (\epsilon_{e}\mathcal{B}_{e} + \epsilon_{\mu}\mathcal{B}_{\mu}) \mathcal{B}_{1}$ for $\omega\chi_{c1}$, number of observed events $N^{\rm {obs}}$, number of estimated background events $N^{\rm bkg}$, number of signal events $N^{\rm sig}$ determined as described in the text, Born cross section $\sigma^{\rm B}$(or upper limit at 90$\%$ C.L.) at each energy point. $N^{\rm sig}$ for $\omega\chi_{c1}$ at $\sqrt{s}$ = 4.416 and 4.599 GeV is taken from the fit. Dash means that the result is not applicable.
Results on $e^+e^-\to \omega \chi_{c2}$. Shown in the table are the channels, the center-of-mass energy, the integrated luminosity $\mathcal{L}$, product of radiative correction factor, vacuum polarization factor, branching fraction and efficiency, $\mathcal{D}=(1 + \delta) \frac{1}{|1-\Pi|^{2}} (\epsilon_{e}\mathcal{B}_{e} + \epsilon_{\mu}\mathcal{B}_{\mu}) \mathcal{B}_{1}$ for $\omega\chi_{c2}$, number of observed events $N^{\rm {obs}}$, number of estimated background events $N^{\rm bkg}$, number of signal events $N^{\rm sig}$ determined as described in the text, Born cross section $\sigma^{\rm B}$(or upper limit at 90$\%$ C.L.) at each energy point. $N^{\rm sig}$ for $\omega\chi_{c2}$ at $\sqrt{s}$ = 4.416 and 4.599 GeV is taken from the fit. Dash means that the result is not applicable.
The cross section for the process e+e- --> omega pi0 --> pi0 pi0 gamma has been measured in the energy range 1.05--2.00 GeV. The experiment has been performed at the e+e- collider VEPP-2000 with the SND detector. The measured e+e- --> omega pi0 cross section above 1.4 GeV is the most accurate to date. Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements. Data on the e+e- --> omega pi0 cross section are well described by the VMD model with two excited rho-like states. From the measured cross section we have extracted the gamma^* --> omega pi0 transition form factor. It has been found that the VDM model cannot describe simultaneously our data and data obtained from the omega --> pi0 mu+ mu- decay. We have also tested CVC hypothesis comparing our results on the e+e- --> omega pi0 cross section with data on the tau- --> omega pi- nu_{tau} decay.
The c.m. energy(E) and measured Born cross section(SIG). For the cross section, the first error is statistical, the second is systematic.
The production of enutral kaons in e + e − annihilation has been measured for c.m. energies between 3.4 GeV and 7.6 GeV. Near 4 GeV the inclusive K S cross section shows an increase and structure similar to total hadron production. Roughly 40–45% of all hadronic final states contain kaons, except at 4.028 GeV and 4.415 GeV, where a significantly larger kaon fraction is observed.
THIS IS TWICE THE MEASURED KS CROSS SECTION. THE ERRORS ARE STATISTICAL ONLY. THERE IS 15 PCT ABSOLUTE NORMALIZATION ERROR, PLUS POSSIBLY SOME ENERGY DEPENDENT ERROR. THE DATA ARE NOT EQUALLY SPACED IN THE ENERGY INTERVALS.
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).
We report measurement of the cross section of $e^+e^-\to \pi^+\pi^-\psi(2S)$ between 4.0 and $5.5 {\rm GeV}$, based on an analysis of initial state radiation events in a $980 \rm fb^{-1}$ data sample recorded with the Belle detector. The properties of the $Y(4360)$ and $Y(4660)$ states are determined. Fitting the mass spectrum of $\pi^+\pi^-\psi(2S)$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $M_{Y(4360)} = (4347\pm 6\pm 3) {\rm MeV}/c^2$, $\Gamma_{Y(4360)} = (103\pm 9\pm 5) {\rm MeV}$, $M_{Y(4660)} = (4652\pm10\pm 8) {\rm MeV}/c^2$, $\Gamma_{Y(4660)} = (68\pm 11\pm 1) \rm MeV$; and ${\cal{B}}[Y(4360)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4360)}^{e^+e^-} = (10.9\pm 0.6\pm 0.7) \rm eV$ and ${\cal{B}}[Y(4660)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4660)}^{e^+e^-} = (8.1\pm 1.1\pm 0.5) \rm eV$ for one solution; or ${\cal{B}}[Y(4360)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4360)}^{e^+e^-} = (9.2\pm 0.6\pm 0.6) \rm eV$ and ${\cal{B}}[Y(4660)\to \pi^+\pi^-\psi(2S)]\cdot \Gamma_{Y(4660)}^{e^+e^-} = (2.0\pm 0.3\pm 0.2) \rm eV$ for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at $4.05 {\rm GeV}/c^2$ is observed in the $\pi^{\pm}\psi(2S)$ intermediate state in the $Y(4360)$ decays.
Measured $e^+e^- \to \pi^+\pi^-\psi(2S)$ cross section for center of mass energy ($E_{\rm cm}$) from 4.0 GeV/$c^2$ to 5.5 GeV/$c^2$. The errors are the sums of statistical errors of signal and background events and the systematic errors.
Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV < \sqrt{s} < 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 < Q^2 < 30 GeV^2 and 1.1 GeV < W_gg < 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.
Measured production cross section for the E+ E- process as a function of W for Q**2 from 8.8 to 30 GeV**2 for the high energy data.
Measured production cross section cross section for the two photon process as a function of W for Q**2 from 8.8 to 30 GeV**2 for the high energy data.
Measured production cross section for the two-photon process as a function of W for Q**2 from 8.8 to 30 GeV**2 for the high energy data.
The reaction e^+e^- -> e^+e^- proton antiproton is studied with the L3 detector at LEP. The analysis is based on data collected at e^+e^- center-of-mass energies from 183 GeV to 209 GeV, corresponding to an integrated luminosity of 667 pb^-1. The gamma gamma -> proton antiproton differential cross section is measured in the range of the two-photon center-of-mass energy from 2.1 GeV to 4.5 GeV. The results are compared to the predictions of the three-quark and quark-diquark models.
Total cross section for P PBAR production at a mean centre-of-mass energy of 197 GeV.
We study the processes $e^+ e^-\to K_S^0 K_L^0 \gamma$, $K_S^0 K_L^0 \pi^+\pi^-\gamma$, $K_S^0 K_S^0 \pi^+\pi^-\gamma$, and $K_S^0 K_S^0 K^+K^-\gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic states over a continuum of center-of-mass energies. The results are based on 469 fb$^{-1}$ of data collected with the BaBar detector at SLAC. We observe the $\phi(1020)$ resonance in the $K_S^0 K_L^0$ final state and measure the product of its electronic width and branching fraction with about 3% uncertainty. We present a measurement of the $e^+ e^-\to K_S^0 K_L^0 $ cross section in the energy range from 1.06 to 2.2 GeV and observe the production of a resonance at 1.67 GeV. We present the first measurements of the $e^+ e^-\to K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ cross sections, and study the intermediate resonance structures. We obtain the first observations of \jpsi decay to the $K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ final states.
The product WIDTH(E+ E- --> J/PSI) * BR(J/PSI --> F2PRIME(1525) K+ K-) * BR(F2PRIME(1525) --> KS KS) and the J/PSI branching fraction.
Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $\psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}$, $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $\phi = (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $\phi = (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $\psi(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow \psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb.
Summary of results at center-of-mass energies from 3.65 to 3.90 GeV. N(SIG) is the number of E+ E- --> P P events; EPSILON is the detection efficiency; L is the integrated luminosity; (1 + DELTA)(DRESSED) is the initial state radiation correction factor without the vacuum polarization correction; and SIG(OBS), SIG(DRESSED) and SIG(BORN) are the observed cross section, the dressed cross section and the Born cross section, respectively.
The two solutions of the dressed cross section and the corresponding phase angles, PHI.
We have measured the inclusive cross section for η production in e+e− interactions near charm threshold using the Crystal Ball detector. No pronounced structure in the energy dependence is observed. By comparing cross sections above and below charm threshold we obtain the limits (90% confidence limit): R(e+e−→FF¯X)RB(F→ηx)<0.15−0.32 (for Ec.m. from 4.0 to 4.5 GeV), RB(D→ηx)<0.13. Our results are inconsistent with a previous report of a large energy dependence of the η cross section ascribed to the crossing of the FF* and F*F* production thresholds.
ENERGY SCAN DATA.
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