We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2 . If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.
ELECTRON BEAM ENERGIES OF 3.0 AND 3.6 GEV.
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.
The cross section for the reaction E+ E- --> K+ K- PI+ PI- measured with ISR data. Statistical errors only.
Cross section measurements for the reaction E+ E- --> K*(892)0 K- PI+. Statistical errors only.
Cross section measurements for the reaction E+ E- --> PHI PI+ PI-. Statistical errors only.
Differential cross sections and polarisations in the reaction π + p→K + Σ + have been measured using the Rutherford Multiparticle Spectrometer at NIMROD. Data are presented at 26 momentum points at approximately 50 MeV/ c intervals in the range 1.282 to 2.473 GeV/ c with an order of magnitude more events than previous experiments. Legendre polynomial expansion coefficients have also been determined.
ERRORS HAVE SYSTEMATIC AND STATISTICAL ERRORS FOLDED IN QUADRATURE. TYPICAL STATISTICAL ERRORS ARE 2 PCT OR LESS.
No description provided.
No description provided.
We report measurements of kaon electroproduction from hydrogen and deuterium targets carried out at the Wilson Synchrotron Laboratory at Cornell University. The reactions γVp→K+X0, K+Γ, and K+Σ0 were studied in the kinematic region 2.15≤W≤3.1 GeV and 1.2<Q2<4.0 GeV2 as a function of Q2, W, and ω. The K+Σ0 cross sections fall much more rapidly with increasing Q2 than the K+Λ cross sections so that K+Σ0KΛ→0 as Q2 increases.
No description provided.
FIRST 11 DATA POINTS ARE FROM THE PRESENT EXPERIMENT. THE NEXT 4 DATA POINTS ARE HARVARD-CORNELL DATA: BEBEK ET AL., PRL 32, 21 (1974). THE LAST 8 DATA POINTS ARE CEA DATA: BROWN ET AL., PRL 28, 1086 (1972).
No description provided.
We report measurements of the electroproduction of single charged pions from hydrogen and deuterium targets for values of ε in the range 0.35<ε<0.45. Data were taken with a hydrogen target at the (W, Q2) points (2.15 GeV, 1.2 GeV2), (2.65, 2.0), (2.65, 3.4), (2.65, 6.0), and (2.65, 10.0). Data were taken with a deuterium target at the (W, Q2) points (2.15, 1.2) and (2.65, 2.0). The transverse cross section obtained by using these data in conjunction with earlier data at high ε to separate the longitudinal and transverse components is used in conjunction with the new data and the t-channel Born term to determine the pion form factor and to re-evaluate previously reported measurements. In the range 0.15 GeV2<Q2<10.0 GeV2 the pion form factor can be described by the simple pole form [1+Q2(0.462±0.024)]−1.
SEPARATED TRANSVERSE AND LONGITUDINAL VIRTUAL-PHOTON CROSS SECTIONS PREVIOUSLY PUBLISHED IN C. J. BEBEK ET AL., PRL 37, 1326 (1976).
DATA POINT 1 (HYDROGEN TARGET).
DATA POINT 1 (HYDROGEN TARGET).
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.
This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.
The cross section for E+ E- --> K0S K+ PI- + CC with statistical errors only.
The cross section for E+ E- --> K+ K- PI0 with statistical errors only.
The cross section for E+ E- --> PHI PI0 with statistical errors only.
Measurements of the forward-angle differential cross section for elastic electron-proton scattering were made in the range of momentum transfer from Q2=2.9 to 31.3 (GeV/c)2 using an electron beam at the Stanford Linear Accelerator Center. The data span six orders of magnitude in cross section. Combinded statistical and systematic uncertainties in the cross section measurements ranged from 3.6% at low Q2 to 19% at high Q2. These data have been used to extract the proton magnetic form factor GMp(Q2) and Dirac form factor F1p(Q2) by using form factor scaling. The logarithmic falloff of Q4F1p expected from leading twist predictions of perturbative quantum chromodynamics is consistent with the new data at high Q2. Some nonperturbative and hybrid calculations also agree with our results.
No description provided.
Formfactor scaling assumes (Ge=Gm/mu).
Measurements have been made of the polarisation parameters Σ , T and P for the process γ p → π + n in the photon energy range 520–2250 MeV at c.m. angles between 30° and 120°. These data were obtained in a double polarisation experiment, using the polarised photon beam from the Daresbury electron synchrotron incident on a polarised proton target. The data are compared with predictions from current theoretical analyses.
No description provided.
No description provided.
Data on pbar-b annihilation in flight into pizero-pizero-eta are presented for nine beam momenta 600 to 1940 MeV/c. The strongest four intermediate states are found to be f_2(1270)-eta, a_2(1320)-pi, sigma-eta and a_0(980)-pi. Partial wave analysis is performed mainly to look for resonances formed by pbar-p and decaying into pizero-pizero-eta through these intermediate states. There is evidence for the following s-channel I = 0 resonances : two 4^{++} resonances with mass and width (M,Gamma) at (2044, 208) MeV and (2320+-30, 220+-30) MeV/ three 2^{++} resonances at (2020+-50, 200+-70) MeV, (2240+-40, 170+-50) MeV and (2370+-50, 320+-50) MeV/ two 3^{++} resonances at (2000+-40, 250+-40) MeV and (2280+-30, 210+-30) MeV/ a 1^{++} resonance at (2340+-40, 340+-40) MeV/ and two 2^{-+} resonances at (2040+-40, 190+-40) MeV and (2300+-40, 270+-40) MeV.
No description provided.
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