We have found events of the form e++e−→e±+μ∓+missingenergy, in which no other charged particles or photons are detected. Most of these events are detected at or above a center-of-mass energy of 4 GeV. The missing-energy and missing-momentum spectra require that at least two additional particles be produced in each event. We have no conventional explanation for these events.
X IN RE INCLUDES TWO OR MORE UNDETECTED PARTICLES.
Decay modes of the charmed mesons, D 0 and D + , are studied in e + e − annihilation data at 4.03 and 4.41 GeV c.m. energy. The products of cross section times branching ratio are measured for the K − π + , K − π + π + π − , K S π + π − and K − π + π + final states. Upper limits are established for the Cabibbo forbidden decays via π + π − , K + K − , K + K − π + , K + π + π − and π + π − π + . The K − π + π + π − final state is shown to be dominated by K − π + ρ 0 .
THESE PARTIAL CROSS SECTIONS ARE CONVERTED TO TOTAL D INCLUSIVE CROSS SECTIONS USING KNOWN BRANCHING RATIOS AND TABULATED IN M. PICCOLO ET AL., PL 86B, 220 (1979).
We find an increase in ∑ ± production between E cm = 4 and 7 GeV which is consistent with charmed baryon production models. A search for the decay ∧ c − → ∑ ± π ± π − yields no significant peaks.
The production of antineutrons and charged Σ's in e+e− annihilations has been measured at s=4 and 7 GeV and at the ψ(3.1) resonance. Two packages containing spark chambers, steel plates, and scintillation counters were added to each side of the Mark I detector at SPEAR. Antineutrons were identified by annihilations which produced large-angle charged prongs characteristic of a high-Q reaction. The resulting antineutron cross sections and momentum distributions are consistent with previous antiproton results. Charged Σ's were detected by forming mass combinations with the n's and charged tracks in the Mark I. A clear signal is seen in the 7-GeV and ψ data, with little or no signal at s=4 GeV. The increase in Σ± production between 4 and 7 GeV is consistent with simple expectations for charmed-baryon production. A search for the decays Λc−→Σ±π∓π− and Σc*Σc→Λc−π± yields no significant peaks. An upper limit, at the 90% confidence level, of σΛcB(Λc→Σ±π∓π−)<56 pb is set.
THE ANTI-SIGMA PRODUCTION CROSS SECTIONS WERE REPORTED IN T. FERGUSON ET AL., PL 79B, 161 (1978).
The reactions e+e−→e+e− and e+e−→μ+μ− have been measured at center-of-mass energies 3.0, 3.8, and 4.8 GeV and production angles of 50°<θ<130° over all azimuthal angles. Agreement with quantum electrodynamics is excellent. New limits for cutoff parameters in quantum-electrodynamic-breakdown models are given.
No description provided.
No description provided.
We present results on the jet structure observed in multihadronic events produced by e+e− annihilation in the Mark I magnetic detector at SPEAR. The evidence for jet structure and the jet-axis angular distribution are reported. We give inclusive distributions of the hadrons in Feynman x, rapidity, and transverse momentum relative to the jet axis.
Observed particle PT with respect to jet axis for events with three or more detected charged particles.
No description provided.
No description provided.
We have observed an azimuthal asymmetry in inclusive hadron production by e+e− annihilation at the center-of-mass energy s=7.4 GeV. The asymmetry is caused by the polarization of the circulating beams in the storage ring and allows separate determination of the transverse and longitudinal structure functions. We find that transverse production dominates for x>0.2 where x is the scaling variable 2ps.
We have measured the asymmetry of the cross section for γp→π+n from a polarized target at 5 and 16 GeV. The range of four-momentum transfer was 0.02<~−t<~1.0 GeV2. The π+ mesons were produced in a polarized butanol target and detected with the Stanford Linear Accelerator Center 20−GeVc spectrometer. A sizable asymmetry was found at both 5 and 16 GeV, a typical value being -0.6 near −t=0.3 GeV2. A small amount of data on the asymmetry of other photoproduction processes was also obtained.
No description provided.
Measurements of multihadron production in e+e− annihilation at center-of-mass energies between 2.6 and 7.8 GeV are presented. Aside from the narrow resonances ψ(3095) and ψ(3684), the total hadronic cross section is found to be approximately 2.7 times the cross section for the production of muon pairs at c.m. energies below 3.7 GeV and 4.3 times the muon-pair cross section at c.m. energies above 5.5 GeV. Complicated structure is found at intermediate energies. Charged-particle multiplicities and inclusive momentum distributions are presented.
The total cross section for hadron production by e+e− annihilation has been measured at center-of-mass energies between 2.4 and 5.0 GeV. Aside from the very narrow resonances ψ(3105) and ψ(3695), the cross section varies between 32 and 17 nb over this region with structure in the vicinity of 4.1 GeV.
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