A search for massive photinos at petra

We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e⁺e^? collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c² at the 95% confidence level, subject to the assumptions d=(100 GeV)² and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}\text{=40}\text{GeV}\text{/c}{}^2$, where d is the supersymmetry breaking scale parameter and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}$ is the scalar electron mass.     

A measurement of the reaction e+e- →e+e-η′ and the radiative width Γη′→γγ at petra

The reaction e⁺e^- → e⁺e^-η' has been observed in the JADE experiment at PETRA, by detecting the final state π⁺π^-γ, resulting from the decay η' → γ?⁰. The cross section was measured at an average beam energy of 17.15 GeV to be σ(e⁺e^- → e⁺e^-η') = 2.2 ± 0.2 (stat.) ± 0.4(syst.) nb, yielding the radiative width Γ_η'γγ= 5.0 ± 0.5(stat.) ± 0.9 (syst.) keV.     

A search for monojet events produced by virtual Z0 bosons in e+e− annihalation at petra

A search was performed for the associated production of two different Higgs bosons via a virtual Z⁰ in e⁺e^? annihilation (e⁺e^? → h₁⁰h₂⁰) using the JADE detector at PETRA. This was motivated by the interpretation of the monojet events observed at the CERN p$\text{p}$ collider as anomalous Z⁰ decays into two neutral Higgs bosons (h₁⁰ and h₂⁰), where h₁⁰ is stable and escapes detection while h₂⁰ decays into hadrons. Single- or di-jet events with large momentum imbalance are then expected at PETRA energies. No evidence for such events was found in our data; this excludes h₂⁰ masses in the range of 1 to 21 GeV with 95% CL, if the branching fraction for Z⁰ → h₁⁰h₂⁰ is a larger than one half that for $\text{Z}{}^0\text{→ v}{}_{\mathrm{\mu }}\text{v}{}_{\mathrm{\mu }}$. The possibility that the monojets could originate from supersymmetric higgsino production from Z⁰ decay is also examined.     

Duality and radiative corrections to leptonic widths in heavy quark systems

We use a duality argument to estimate the gluonic radiative corrections of orders α_s and α_s² to the leptonic widths for heavy quark systems.     

Search for narrow resonances in e+e− annihilation at c.m. energies between 29.90 and 31.46 GeV

A search for narrow resonances in e⁺e^? annihilation at c.m. energies between 29.90 and 31.46 GeV provides no evidence for the existence of such states. The 90% confidence upper limit on the integrated resonance cross section is 38 nb MeV, significantly below the value expected for the lowest (t,t?) bound state.     

Upper limit on beauty lifetime and lower limit on weak mixing angles

Muons from a multihadron sample are used to determine an upper limit τ<1.4 × 10^?12s (95% CL) on the lifetime of beauty particles. The data are obtained with the JADE detector at PETRA. The result is interpreted within the standard model.     

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.     

Search for new flavour production at PETRA

The topological distribution of hadrons from the reaction e⁺e^?→multihadrons has been studied at PETRA energies between $\text{s}\text{=22}\text{and}\text{31.6 GeV}$. No evidence is seen for spherical events which would be expected if massive particles bearing new flavours were produced.     

A measurement of the electroweak induced charge asymmetry in e+e−→bb̄

The forward-backward charge asymmetry for the process $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{b}\text{b}\text{?}\text{→ μ}{}^{\mathrm{\pm }}\text{+}$ hadrons has been measured using the JADE detector at PETRA. An asymmetry of (?22.8 ± 6.0 ± 2.5)% was observed at an average center of mass energy of 34.6 GeV. For comparison, an asymmetry of ?25.2% is expected on the basis of the standard Glashow-Salam-Weinberg model.     

A measurement of the η radiative width Γη→γγ

The radiative width of the η meson has been measured at PETRA in photon-photon collisions. The resulting value is Γ_η→γγ = 0.53±0.04±0.04 keV.     

The strangeness-conserving effective weak interaction in the quark basis

Strong interaction corrections to the Glashow-Salam-Weinberg model of electroweak interaction are studied, for the up and down quarks only, to all orders of leading logarithms using renormalization-group techniques. The resulting quark effective weak hamiltonian is explicitly written out in a form convenient for obtaining matrix elements. The accuracy of this result is estimated by a comparison with finite, one-loop calculations of parity-violating parts of the interaction.     

Comparison of three-jet events with QCD shower models

Distributions of particles in three-jet events from e⁺e^? → hadrons are compared with different fragmentation schemes, i.e. the Lund string model, independent parton fragmentation and QCD shower models. Effects specific to the string scheme, which have been seen in the data, are also reproduced by QCD shower models if soft gluon interference effects are included.     

Observation of a charge asymmetry in e+e− → μ+μ−

The angular distribution and the s dependence of the total cross section for the process e⁺e^? → μ⁺μ^? have been measured using the JADE detector at PETRA. After radiative corrections, a forward-backward asymmetry of ?(11.8±3.8) % was observed at an average centre of mass energy of 33.5 GeV. For comparison, an asymmetry of ?7.8 % is expected on the basis of the standard Glashow-Salam-Weinberg model.     

Observation of planar three-jet events in e+e− annihilation and evidence for gluon bremsstrahlung

Topological distributions of charged and neutral hadrons from the reaction e⁺e^? → multihadrons are studied at √s of about 30 GeV. An excess of planar events is observed at a rate which cannot be explained by statistical fluctuations in the standard two-jet process. The planar events, mostly consisting of a slim jet on one side and a broader jet on the other, are shown actually to possess three-jet structure by demonstrating that the broader jet itself consists of two collinear jets in its own rest system. Detailed agreement between data and predictions is obtained if the process $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→q}\text{q}\text{?}\text{g}$ is taken into account. This strongly suggests gluon bremsstrahlung as the origin of the planar three-jet events. By comparison of the data with the qq?g-model we obtain a value for the strong coupling constant of α_S(q² = 0.17 ± 0.04.     

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.     

On extracting weak quark couplings from bottom and top decays

We list and discuss the various types of systematic uncertainties one faces when extracting quark mixing angles from the decays of bottom and top hadrons. Evaluating various suggested methods we conclude that a study of the lepton energy spectrum in B and T decays provides a reasonable way of obtaining the ratio of mixing angles; yet analysis of just the endpoint region will not lead to a reliable determination. Such results should be backed up by other studies based on very energetic kaons and on the mode $\text{B}{}^{\mathrm{?}}\text{→τ}{}^{\mathrm{?}}\text{ν}{}_{\mathrm{\tau }}$. A dedicated effort should be made to search for flavour changing neutral currents in channels like B, T→τ⁺τ^?X.     

Heavy quark yields at high energies

It is shown that the absorption correction due to gluon rescattering changes drastically the value of the cross section for heavy quark production at and also the ratio of c and b cross sections. The cross section for b-quark production, estimated from the data on muon and J/ψ production should be increased by a factor of about 2–2.5 at Fermilab-Tevatron energies.     

Probing the top quark flavor-changing couplings at CEPC

We propose to study the flavor properties of the top quark at the future Circular Electron Positron Collider(CEPC) in China.We systematically consider the full set of 56 real parameters that characterize the flavor-changing neutral interactions of the top quark,which can be tested at CEPC in the single top production channel.Compared with the current bounds from the LEP2 data and the projected limits at the high-luminosity LHC,we find that CEPC could improve the limits of the four-fermion flavor-changing coefficients by one to two orders of magnitude,and would also provide similar sensitivity for the two-fermion flavor-changing coefficients.Overall,CEPC could explore a large fraction of currently allowed parameter space that will not be covered by the LHC upgrade.We show that the c-jet tagging capacity at CEPC could further improve its sensitivity to top-charm flavor-changing couplings.If a signal is observed,the kinematic distribution as well as the c-jet tagging could be exploited to pinpoint the various flavor-changing couplings,providing valuable information about the flavor properties of the top quark.     

A study of the reaction p + p → p + p + X at ISR energies

We have performed an experiment to investigate the reaction p + p → p₁ + p₂ + X at the CERN Intersecting Storage Rings (ISR). The dependence of the cross-section on the mass and rapidity of the system X, and on the momentum transfer squared t₁, t₂ to the outgoing protons is studied. We observe signals for the production of ?, ω, f, and A₂ mesons in the missing-mass spectra, and conclusions are made about the contribution of double-Pomeron exchange.