We report a measurement of the differential cross section of $\pi^0$ pair production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0 \pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$, where $Q^2$ is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and $|\cos \theta^*|$ < 1.0 for the total energy and pion scattering angle, respectively, in the $\gamma^* \gamma$ center-of-mass system. The results are based on a data sample of 759 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The transition form factor of the $f_0(980)$ and that of the $f_2(1270)$ with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=3.45 GeV$^2$.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=4.46 GeV$^2$.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=5.47 GeV$^2$.
The cross section for the e$^{+}$ e$^{–}$ → π$^{+}$π$^{–}$π$^{0}$ process in the energy range 1.05–2.00 GeV has been measured using the data collected in the experiment with the Spherical Neutral Detector (SND) at the VEPP-2000 e$^{+}$ e$^{–}$ collider. The obtained results on the cross section are in good agreement with previous measurements by the SND at the VEPP-2M collider and BABAR, but have a better accuracy.
The Born cross section of the process e+e- -> pi+pi-pi0.
Using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we measure the energy dependence of the $e^+e^- \to h_b(nP)\pi^+\pi^-$ $(n=1,2)$ cross sections from thresholds up to $11.02\,$GeV. We find clear $\Upsilon(10860)$ and $\Upsilon(11020)$ peaks with little or no continuum contribution. We study the resonant substructure of the $\Upsilon(11020) \to h_b(nP)\pi^+\pi^-$ transitions and find evidence that they proceed entirely via the intermediate isovector states $Z_b(10610)$ and $Z_b(10650)$. The relative fraction of these states is loosely constrained by the current data: the hypothesis that only $Z_b(10610)$ is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only $Z_b(10650)$ is produced is not excluded at a significant level.
Center-of-mass energies, integrated luminosities and Born cross sections for all energy points. The first uncertainty in the energy is uncorrelated, the second is correlated. The three uncertainties in the cross sections are statistical, uncorrelated systematic and correlated systematic.
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No description provided.
The angular and energy distributions of pions produced by 650-MeV protons and pion-nucleon correlations were studied using a liquid hydrogen bubble chamber. The present investigation indicates that the experimental angular distributions of neutral and charged pions are consis- tent with the assumption of isotopic spin conservation. The contributions of rrN subsystem states with isospin T 11'N = 7' 2 and % are measured; the contribution of the latter is 72 ± 3%.
No description provided.
The production of A ( ~ 0 ) hyperons (henceforth denoted A hyperons for short) and K 0 mesons by negative pions on carbon was investigated. The angular and momentum distribu- tions of these particles and the cross sections for their production are determined, and the cross sections of the different channels of the reactions are estimated. The fraction of strange particles produced in the secondary processes is estimated for the first time. The momentum spectrum of the A hyperons (in the pion-nucleon c.m.s.) is compared with the spectrum for rr-p interactions. The experimental data are compared with the results of cascade-model calculations made by the Monte Carlo method.
No description provided.
Using a data sample of 6.8 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider we select about 2700 events of the $e^+e^- \to p\bar{p}$ process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio $|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30$.
The c.m. energy, beam energy shift, luminosity, number of selected $e^+e^- \to p\bar{p}$ events, detection efficiency, radiative correction, and cross section with statistical and systematic errors. The data for collinear type events.
The c.m. energy, luminosity, number of signal events, fraction of antiprotons stopped in beam pipe and DC inner shell, efficiency, cross section with statistical and systematic errors, for annihilation events.
In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider the cross section for the process $e^+e^-\to\eta\pi^+\pi^-$ has been measured in the center-of-mass energy range from 1.22 to 2.00 GeV. Obtained results are in agreement with previous measurements and have better accuracy. The energy dependence of the $e^+e^-\to\eta\pi^+\pi^-$ cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions $B(\rho(1450)\to\eta\pi^+\pi^-)B(\rho(1450)\to e^+e^-)$ has been extracted and compared with the same products for $\rho(1450)\to\omega\pi^0$ and $\rho(1450)\to\pi^+\pi^-$ decays. The obtained cross section data have been also used to test the conservation of vector current hypothesis.
The c.m. energy ($\sqrt{s}$), integrated luminosity ($L$), detection efficiency ($\varepsilon$), number of selected signal events ($N$), radiative-correction factor ($1 + \delta$), measured $e^+e^- \to \eta \pi^+\pi^-$ Born cross section ($\sigma_B$). For the number of events and cross section the statistical error is quoted. The systematic uncertainty on the cross section is 8.3% at $\sqrt{s}<1.45$ GeV, 5.0% at $1.45<\sqrt{s}<1.60$ GeV, and 7.8% at $\sqrt{s}>1.60$ GeV.
Cross sections for pi+-p elastic scattering have been measured to high precision, for beam momenta between 800 and 1240 MeV/c, by the EPECUR Collaboration, using the ITEP proton synchrotron. The data precision allows comparisons of the existing partial-wave analyses (PWA) on a level not possible previously. These comparisons imply that updated PWA are required.
Differential cross section of elastic $\pi^+$p-scattering at P= 800.25 MeV/c. Errors shown are statistical only.
Differential cross section of elastic $\pi^+$p-scattering at P= 803.75 MeV/c. Errors shown are statistical only.
Differential cross section of elastic $\pi^+$p-scattering at P= 807.25 MeV/c. Errors shown are statistical only.
We have analyzed a data set taken over 2.76 years live time with the Baikal neutrino telescope NT200. The goal of the analysis is to search for neutrinos from dark matter annihilation in the center of the Sun. Apart from the conventional annihilation channels $b\bar{b}$, $W^+W^-$ and $\tau^+\tau^-$ we consider also the annihilation of dark matter particles into monochromatic neutrinos. From the absence of any excess of events from the direction of the Sun over the expected background, we derive 90% upper limits on the fluxes of muons and muon neutrinos from the Sun, as well as on the elastic cross sections of dark matter scattering on protons.
Process: DM DM --> BOTTOM BOTTOMBAR. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
Process: DM DM --> TAU+ TAU-. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
Process: DM DM --> W+ W-. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
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