Search for narrow resonances in e+e− annihilation at petra

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-$\text{2}\text{3}$ quarks exists in this energy range.     

The total hadronic cross section for e+e− annihilation between 3.1 and 4.8 GeV center of mass energy

Using the solenoidal magnetic detector PLUTO, we have measured the total cross section for e⁺e^? annihilation into hadrons. Results are presented for center of mass energies between 3.6 and 4.8 GeV, and in the regions of the $\text{J}\text{ψ}$(3.1) and ψ(3.7) resonances. We also present results for the 2 prong cross section in the energy range 3.6 to 4.8 GeV.     

Two-particle correlations in e+e− annihilation

We present measurements of two-particle angular correlations in hadron jets produced in e⁺e^? annihilation between 7.7 and 31.6 GeV c.m. energy. The data are compared to predictions of high order perturbative QCD calculations.     

A study of jets in electron positron annihilation into hadrons in the energy range 3.1 to 9.5 GeV

From an analysis of data taken with the detector PLUTO and the DORIS storage rings we have obtained evidence for jet structure in e⁺e^? annihilation with hadrons. Results for mean sphericity, mean thrust, the angular dependence of the jet axis and for 〈p_t〉 and 〈p_∥〉 with respect to the jet axis are presented. At 9.4 GeV we also discuss the angular dependence of the charged and neutral deposited energy with respect to the jet axis.     

Determination of the electronic branching ratio of the ϒ(9.46) and an upper limit for its total width

We have measured the reaction e⁺e^? → e⁺e^? at the ? Using athe excess of electron pairs over the QED expectation we obtain an electronic branching ratio of B_ee = (5.1 ± 3.0) %. Combining this with publishe values of the muonic branching ratio B_μμ we conclude that the ? is a narrow state with a total width < 180 keV at 95% C.L.     

Phase transitions and magnetic monopoles in SO(10)

In a unified gauge theory based on SO(10), the combination of a strongly first order phase transition and a magnetic confinement mechanism can suppress the density of magnetic monopoles at the time of nucleosynthesis. However, this only occurs if SO(10) breaks down to SU(3)_c ? U (1)_em via SU(4)_c ? [SU(2)_L × SU(2)_R]. For the other symmetry breaking patterns of SO(10) obtained with a minimal Higgs system, the potential conflict with the standard big bang cosmology is not naturally avoided.     

Measurement of the branching ratios for the decays J/ψ(3.1) → fω and J/ψ(3.1) → Bπ

Decays of the J/ψ (3.1) resonance into final states with four charged and one neutral pion have been investigated. We measured the branching ratios J/ψ (3.1) → fω/all = 0.40 ± 0.14)% and J/ψ (3.1) → (B⁺π^? + B^?π⁺)/all = (0.28 ± 0.07)%.     

Evidence for the τ → νϱπ decay mode

Annihilation of e⁺e^? into final states with a single electron has been studied with the PLUTO detector at the DORIS storage ring at CMS energies from 3.6 to 5 GeV. In the sample of 4-prong events without any detected photon we observe 21 events which we assign to the reaction e⁺e^? → τ⁺τ^? → ννe + ν?⁰π. We obtain a branching ratio for τ⁺ → ν?⁰π⁺ of 0.050 ± 0.015 with an overall systematic uncertainty of 30%. The data are consistent with the ?π coming from an A₁ meson.     

Hadron production from photon-photon interactions in the CM energy range from 1 to 5 GeV

We present the first data on photon-photon annihilation into hadrons for CM energies > 1 GeV obtained with the detector PLUTO at the e⁺e^? storage ring PETRA. Cross sections are extracted using an inelastic eγ scattering formalism. The results are compared to expectations from Regge-like models.     

Lepton and hadron pair production in two-photon reactions

We have measured the production of charged particle pairs in e⁺e^? initiated two-photon reactions. The observed rates and invariant mass spectra agree with expectations from QED if a resonant π⁺π^? production at the f⁰ mass is added. Assuming dominance of the helicity 2 production we obtain the width Γ(f⁰→γγ) = 2.3 ± 0.5 keV.     

Auxiliary-field anomalies

In general, quantum corrections to matter-supergravity couplings uniquely determine what are acceptable auxiliary fields for N = 1 supergravity, and partially determine those for N = 2. This is because one-loop corrections produce anomalies in not only the local superscale transformations, but also in the local (Poincaré) supersymmetry transformations themselves, except for special cases: in particular, for N = 1 the $\text{n =}\text{1}\text{3}$ minimimal set of auxiliary fields is uniquely chosen.     

The large N limit of the O(N) Heisenberg spin system in two dimensions

The large N limit of the O(N) Heisenberg spin system in two dimensions (a lattice version of the non-linear σ-model) is analysed by the collective field technique. A compact expression for the mass gap and the β-function is obtained for arbitrary but fixed gN. The strong and weak coupling limits of this expression correctly reproduce the known results.     

Measurement of the J/ψ radiative decay into f0(1270)γ

The J/ψ decay modes f⁰(1270)γ and ρπ have been studied in e⁺e^? collision at 3.1 GeV center of mass energy leading to the π⁺π^?γ and π⁺π^?π⁰ final states. The f⁰γ decay branching ratio is measured to be (0.20 ± 0.07) × 10^?2, a value comparable to the J/ψ radiative decay rates into the ηγ and η′γ channels. The J/ψ decay branching ratio into ?π is measured to be (1.6 ± 0.4) × 10^?2.     

Observation of the decay τ → πv

The decay of the heavy lepton τ into πv has been established using the magnetic detector PLUTO. The branching ratio is determined to be BR(τ→πv)=(9.0 ± 2.9)% with an additional systematic uncertainty of 2.5%. This value is in good agreement with the theoretical prediction.     

Multiplicity distributions in e+e− annihilations at petra energies

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.     

Measurement of the f0(1270) polarization in the J/ψ → f0γ decay

The polarization of the f⁰(1270) and ?⁰(770) produced in the J/ψ decays into f⁰γ and ?⁰π⁰ are measured in e⁺e^? collisions at 3.1 GeV. A fit to the f⁰ production and decay angular distributions yields the values A₁/A₀ = 0.6 ± 0.3 and A₂/A₀ = 0.3 _?1.6^+0.6, where A_λ are the f⁰ helicity amplitudes. These results are in good agreement with the values predicted from a QCD two-gluon-exchange model. In addition an upper limit of 2.3 × 10^?4 is obtained for the J/ψ → f′⁰(1514) γ decay branching ratio which implies Γ(J/ψ → f′γ)/Γ(J/ψ → f⁰γ) ? 0.12 ± 0.05.     

Electroproduction and annihilation in the deep-inelastic limit

It is shown, in a specific field theory, that the electroproduction and annihilation structure functions yield the same threshold behaviors, i.e., if $\text{F(ω)=C(1?ω)}{}^{\mathrm{\gamma }}\text{,}\text{then}\text{F}\text{(ω)=C(ω?1)}{}^{\mathrm{\gamma }}\text{,}\text{where}\text{γ}$ is not an integer in general.     

Quasi-elastic and deep-inelastic dissipative processes

Quasi-elastic and deep inelastic rates are calculated assuming that the colliding nuclei move on classical trajectories and that the excitations and the particle or energy exchanges are due to the shell-model wells interacting with the nucleons. (One-body collisions). This allows a microscopic, parameter free, calculation of the optical potential, as well as the energy and the angular momentum losses, and is a good approximation as long as the collision is peripheral. The correction due to two-body collisions between individual nucleons is also evaluated. The focus will be on the evolution of the various reaction rates as a function of energy. The system chosen for the discussion is ¹⁶O + ¹⁶O from 3 MeV/A to 60 MeV/A.     

Leading particles and charged particle multiplicity in annihilation and non-annihilation interactions

Using data from our K^?p experiment at 8.25 GeV/c we have investigated the charged particle multiplicity, and the variation of charged pion multiplicity as a function of the effective mass squared of all pions, for various samples of data, and compared our results with $\text{p}$p annihilation data and pp data. Evidence is presented which suggests that the difference in behaviour between the annihilation and non-annihilation data is not due to some specific mechanism such as baryon exchange, but is related to the absence of leading particles in the former case.     

Relationship between the cross section for deep-inelastic scattering and the cross section for inclusive annihilation

Arguments have been presented that suggest that available experimental data on the structure functions for the processes ep → eX and e ⁺ e ^? → p( $\bar p$ )X do not confirm the so-called reciprocity relation, which was obtained in the leading-logarithm approximation of perturbation theory. It has also been shown that the asymptotic relationship between the above processes that was obtained on the basis of more general considerations is compatible with existing data.