We present measurements of the inclusive production of antideuterons in $e^+e^-$ annihilation into hadrons at $\approx 10.58 \mathrm{\,Ge\kern -0.1em V}$ center-of-mass energy and in $\Upsilon(1S,2S,3S)$ decays. The results are obtained using data collected by the BABAR detector at the PEP-II electron-positron collider. Assuming a fireball spectral shape for the emitted antideuteron momentum, we find $\mathcal{B}(\Upsilon(1S) \to \bar{d}X) = (2.81 \pm 0.49 \mathrm{(stat)} {}^{+0.20}_{-0.24} \mathrm{(syst)})/! \times /! 10^{-5}$, $\mathcal{B}(\Upsilon(2S) \to \bar{d}X) = (2.64 \pm 0.11 \mathrm{(stat)} {}^{+0.26}_{-0.21} \mathrm{(syst)})/! \times /! 10^{-5}$, $\mathcal{B}(\Upsilon(3S) \to \bar{d}X) = (2.33 \pm 0.15 \mathrm{(stat)} {}^{+0.31}_{-0.28} \mathrm{(syst)})/! \times /! 10^{-5}$, and $\sigma (e^+e^- \to \bar{d}X) = (9.63 \pm 0.41 \mathrm{(stat)} {}^{+1.17}_{-1.01} \mathrm{(syst)}) \mbox{\,fb}$.
The strong coupling alpha_s(M_Z^2) has been measured using hadronic decays of Z^0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order, O(alpha_s^2), and including resummed analytic formulae based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between alpha_s(M_Z^2) values extracted from these different measures. Combining all results we obtain alpha_s(M_Z^2) = 0.1200 \pm 0.0025(exp.) \pm 0.0078(theor.), where the dominant uncertainty is from uncalculated higher order contributions.
Measurements of the charged multiplicities for hadron production in e + e − annihilation in the center of mass energy range 9–32 GeV have been made. The average charged multiplicity has an energy dependence much stronger than ln s and similar to that reported for pp collisions. Quantitative differences are observed in the magnitude of both the average multiplicity 〈 n ch 〉 and the dispersion D ch for e + e − and pp interactions at the same center of mass energy. 〈 n ch 〉 and the ratio 〈 n ch / D ch in e + e − annihilations are significantly larger than in pp collisions and are found to be in overall agreement with QCD predictions. KNO scaling is seen to be satisfied.
The cross section for the process e + e − → multihadrons has been measured at the highest PETRA energies. We measure R (the total cross section in units of the point-like e + e - → μ + μ - cross section) to be 2.9 ± 0.7, 4.0 ± 0.5, 4.6 ± 0.4 and 4.2 ± 0.6 at s of 22, 27.7, 30 and 31.6 GeV, respectively. The observed average multiplicity, together with existing low energy data, indicate a rapid increase in multiplicity with increasing energy.
The total cross section for electron-positron annihilation into three or more hadrons has been measured for centre of mass energies between 1.4 and 2.0 GeV. The data were obtained at ADONE by the BB̄ experiment.
We report experimental results on the cross section for the reaction e + e − → hadrons as a function of the total c.m. energy in the range W = 1.42–3.09 GeV. The results, combined with those already existing below the charm threshold, clearly indicate a structure for R ( W ) = α ( e + e − → hadrons)/ α ( e + e − → μ + μ − ) in that energy region.
We have performed a search for narrow resonances in the center of mass energy range from 29.90 to 31.46 GeV using the e + e − storage ring PETRA at DESY. We present the total cross section for hadron production and an upper limit for resonance production, indicating that no bound state of charge- 2 3 quarks exists in this energy range.
Hadron production by e + e − annihilation has been studied for c.m. energies W between 13 and 31.6 GeV. As a function of 1n W the charged particle multiplicity grows faster at high energy than at lower energies. This is correlated with a rise in the plateau of the rapidity distribution. The cross section s d σ /d x is found to scale within ±30% for x > 0.2 and 5 ⩽ W ⩽ 31.6 GeV.
We have observed e + e − hadrons at C.M. energies of 13 GeV and 17 GeV at PETRA using the TASSO detector. We find R (13 GeV) = 5.6 ± 0.7 and R (17 GeV) = 4.0 ± 0.7. The additional systematic uncertainty is 20%. Comparing inclusive charged hadron spectra we observe scaling between 5 GeV and 17 GeV for x = p / p beam > 0.2; however the 13 GeV cross section is above the 17 GeV cross section for smaller x . This may be due to copious bb̄ production. The events become increasingly jet like at high energies as evidenced by a shrinking sphericity distribution with increasing energy.
Results on e + e − annihilation into hadrons at c.m. energies between 22 and 31.6 GeV are presented. The data were accumulated with the PLUTO detector at PETRA. The events are dominantly of the two-jet type. The value of the relative hadronic cross section R =3.88 ± 0.22 along with the details of the sphericity and thrust distribution rule out an open (tt̄) channel (Q t = 2 3 ) below 30 GeV. The inclusive muon results support the above conclusion.
Forum