The negative kaon electromagnetic form factor has been measured in the space-like q 2 range 0.015–0.10 (GeV/ c ) 2 by the direct scattering of 250 GeV kaons from electrons at the CERN SPS. It is found that the kaon mean square charge radius 〈 r 2 K 〉 = 0.34 ± 0.05 fm 2 . From data collected simultaneously for πe scattering, the difference between the charged pion and kaon mean square radii (which is less sensitive to systematic errors) is found to be 〈 r 2 π 〉 − 〈 r 2 K = 0.1 0 ± 0.045 fm 2 .
Ratio is assumed free of systematic error.
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No description provided.
ALL NEGATIVE PARTICLES WAS CONSIDERED AS PI-.
ALL NEGATIVE PARTICLES WAS CONSIDERED AS PI-.
A high-precision measurement of the differential cross section for Bhabha scattering (e+e−→e+e−) is presented. The measurement was performed with the MAC detector at the PEP storage ring of the Stanford Linear Accelerator Center, at a center-of-mass energy of 29 GeV. Effects due to electroweak interference are observed and agree well with the predictions of the Glashow-Salam-Weinberg model. The agreement between the data and the electroweak prediction rules out substructure of the electron up to mass scales of 1 TeV.
Error contains both statistics and systematics.
No description provided.
No description provided.
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High-precision measurements of electron-positron annihilation into final states of two, three, and four photons are presented. The data were obtained with the MAC detector at the PEP storage ring of the Stanford Linear Accelerator Center, at a center-of-mass energy of 29 GeV. The measured e+e−→γγ differential cross section is used to test the validity of quantum electrodynamics (QED) in this energy range; it agrees well with QED, and the limit on cutoff parameters for the electron propagator is Λ>66 GeV. The measurement of e+e−→γγγ is used to test the QED calculations of order α3 and to search for anomalies that would indicate the existence of new particles; the agreement with QED is excellent and no anomalies are found. Two events from the reaction e+e−→γγγγ are found, in agreement with the QED prediction.
Errors are combined statistical and systematics.
No description provided.
Two 4gamma events are observed corresponding to a cross section of 0.02 PB.
Ratios of inclusive cross sections σ(π+)/σ(π++K++p) and\(\sigma (\pi ^ -)/\sigma (\pi ^ -+ K^ -+ \bar p)\) were measured for proton-proton interactions with a highpT hadron in the final state around c.m.s. scattering angles θ≅20°, 20° and 45° at two ISR energies\(\sqrt s= 31\) Gev and 62 GeV. Results are shown as functions of transverse and longitudinal momentum and are compared with parton model predictions. The different dependences of positive and negative pion fractions atpT≅2–3 GeV/c on longitudinal momenta is similar to that observed in soft hadronic interactions at low values ofpT where the leading proton effect (diquark fragmentation) is known to contribute. The quantitative agreement of the data with diquark model predictions indicates the presence of diquark fragmentation also in highpT jets.
No description provided.
No description provided.
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The pion form factor has been measured in the space-like q 2 region 0.014 to 0.26 (GeV/ c ) 2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar results to the naive pole form, and conclude 〈r 2 π 〉 = 0.438±0.008 fm 2 .
No description provided.
Data are presented for the exclusive reaction pp → pp π+ π− at\(\sqrt s= 62GeV\) with two leading protons at large Feynman-x and a centrally produced π+;π− system. In this kinematical configuration one expects a substantial contribution from Double Pomeron Exchange, which is a potential source of glueballs. The experiment was performed at the CERN ISR using the Split Field Magnet spectrometer. In the mass range between 1,000 and 1,700 MeV/c2 the invariant mass distribution for the central π+;π− system exhibits a very significant signal for thef0(1270) and no other obvious resonant states.
No description provided.
A new technique is applied to data collected at the ψ(3770) resonance to derive charmed-D-meson branching fractions without relying on the measurement of D-production cross sections. Measurements are presented for three decay modes of the D0 (K−π+, D−π−π+π+, and K−π+π0 and four decay modes of the D+ (K−π+π+,K−π+π+π0,KS0π+, and KS0π+π0). The resulting branching fractions are significantly larger than previous measurements.
No description provided.
No description provided.
The relative yields of kaons and protons compared with the yield of pions at highpT and polar angles θ away from 90° (in the range from 10° to 45°) are presented forpp, dd, and αα interactions at a centre-of-mass energy\(\sqrt {s_{NN} }= 31\) GeV per nucleon-nucleon collision. The measured particle ratios depend on the atomic mass numberA of the beam particles and on θ. TheA dependence of the ratios becomes stronger for largerpT and is more pronounced at smaller polar angles.
ERRORS ARE PURELY STATISTICAL.
ERRORS ARE PURELY STATISTICAL.
ERRORS ARE PURELY STATISTICAL.
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