We have observed 1085 events of the type e + e − → hadrons, in the total centre-of-mass energy range √ s = 1.2 to 3.0 GeV. The energy dependence of the total annihilation cross-section, parametrized in the form σ ( e + e − → hadrons ) = A · s n , is measured to be n = -(1.54 −0.29 +0.17 ) in the above energy range.
RESULTS USING THE (AP P) MODEL WITH PHASE-SPACE CORRECTIONS.
R AS CALCULATED FROM THE TOTAL HADRONIC CROSS SECTION USING THE (AP P) MODEL.
TOTAL CROSS SECTIONS OBTAINED USING THE QUASI-MODEL-INDEPENDENT METHOD ARE TABULATED HERE.
We have measured the crosss section for the reaction e + e − → 4 π ± in the energy range 1 2–3.0 GeV.No statistically significant evidence for a new vector meson in the ϱ″ region is found.
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The study of 620 hadron pairs produced in the s -range (1.44−9.0) GeV 2 , has yielded 110 collinear hadronic events. Their identification in terms of π and K mesons allows the determination of the time-like electromagnetic from factors of these pseudoscalar mesons in the above time-like range. The total number of (e + e − ) events observed in the same experimental conditions is 18 048.
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The analysis of 1466 events of the type e + e − → μ ± μ ± , in the time-lifke range from 1.44 to 9.00 GeV 2 , sh that the absolute value of the cross-section and its energy dependence follow QED expectations within (± 3.2%) and (± 1.2%), respectively.
The cross section of the reaction $e^+ e^- \to \mu^\pm \mu^\mp$ integrated over the experimental apparatus at 14 values of the colliding beam energy $E$ corresponding to total centre-of-mass energy $\sqrt{s}=2E$ from 1.2 to 3.0 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.
Cross section measurement for PHI(1020).
Mass measurement for PHI(1020).
Measurement of the PHI(1020) width.
We report a high-statistics measurement of differential cross sections for the process gamma gamma -> pi^0 pi^0 in the kinematic range 0.6 GeV <= W <= 4.0 GeV and |cos theta*| <= 0.8, where W and theta* are the energy and pion scattering angle, respectively, in the gamma gamma center-of-mass system. Differential cross sections are fitted to obtain information on S, D_0, D_2, G_0 and G_2 waves. The G waves are important above W ~= 1.6 GeV. For W <= 1.6 GeV the D_2 wave is dominated by the f_2(1270) resonance while the S wave requires at least one additional resonance besides the f_0(980), which may be the f_0(1370) or f_0(1500). The differential cross sections are fitted with a simple parameterization to determine the parameters (the mass, total width and Gamma_{gamma gamma}B(f_0 -> pi^0 pi^0)) of this scalar meson as well as the f_0(980). The helicity 0 fraction of the f_2(1270) meson, taking into account interference for the first time, is also obtained.
Differential cross section for W = 1.33, 1.35 and 1.37 GeV.
Total cross section for the cos(theta*) ranges 0.0 to 0.6 and 0.0 to 0.8.
The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
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We study the processes e+e- --> K+ K- pi+pi-gamma, K+ K- pi0pi0gamma, and K+ K- K+ K-gamma, where the photon is radiated from the initial state. About 84000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb-1 of BaBar data. The invariant mass of the hadronic final state defines the \epem center-of-mass energy, so that the K+ K- pi+pi- data can be compared with direct measurements of the e+e- --> K+ K- pi+pi- reaction. No direct measurements exist for the e+e- --> K+ K-pi0pi0 or e+e- --> K+ K-K+ K- reactions, and we present an update of our previous result with doubled statistics. Studying the structure of these events, we find contributions from a number of intermediate states, and extract their cross sections. In particular, we perform a more detailed study of the e+e- --> phi(1020)pipigamma reaction, and confirm the presence of the Y(2175) resonance in the phi(1020) f0(980) and K+K-f0(980) modes. In the charmonium region, we observe the J/psi in all three final states and in several intermediate states, as well as the psi(2S) in some modes, and measure the corresponding product of branching fraction and electron width.
Cross section measurements for the reaction E+ E- --> PHI F0(600). Statistical errors only.
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