This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.
Measured cross sections and forward-backward asymmetries for non-radiative E+ E- --> E+ E- events.
Differential cross sections for non-radiative E+ E- --> E+ E- events at centre of mass energy 189 GeV.
Differential cross sections for non-radiative E+ E- --> E+ E- events at centre of mass energy 192 GeV.
These final results on e+e- -> W+W- production cross-section measurements at LEP2 use data collected by the DELPHI detector at centre-of-mass energies up to 209 GeV. Measurements of total cross-sections, W angular differential distributions and decay branching fractions, and the value of the CKM element |V_{cs}| are compared to the expectations of the Standard Model. These results supersede all values previously published by DELPHI.
W pair production cross section for the fully hadronic channel.
W pair production cross section for the semi-leptonic decay channel.
W pair production cross section for the fully leptonic decay channel.
The leptoproduction of J/psi mesons is studied in inelastic reactions for four momentum transfers 2<Q^2<100GeV^2. The data were taken with the H1 detector at the electron proton collider HERA and correspond to an integrated luminosity of 77 pb-1. Single differential and double differential cross sections are measured with increased precision compared with previous analyses. New leading order calculations within the non-relativistic QCD factorisation approach including colour octet and colour singlet contributions are compared with the data and are found to give a reasonable description of most distributions. An exception is the shape of the distribution in the J/psi fractional energy, z, which deviates significantly from that of the data. Comparisons with photoproduction are made and the polarisation of the produced J/psi meson is analysed.
J/PSI leptoproduction differential cross section as a function of Q**2.
J/PSI leptoproduction differential cross section as a function of Z.
J/PSI leptoproduction differential cross section as a function of W.
Three-jet production is studied for the first time in deep-inelastic positron-proton scattering. The measurement carried out with the H1 detector at HERA covers a large range of four-momentum transfer squared 5 < Q^2 < 5000 GeV^2 and invariant three-jet masses 25 < M_(3jet) < 140 GeV. Jets are defined by the inclusive k_T algorithm in the Breit frame. The size of the three-jet cross section and the ratio of the three-jet to the dijet cross section R_(3/2) are described over the whole phase space by the predictions of perturbative QCD in next-to-leading order. The shapes of angular jet distributions deviate significantly from a uniform population of the available phase space but are well described by the QCD calculation.
The inclusive 3-Jet cross section as a function of Q**2.
The ratio of 3 jets to 2 jets as a function of Q**2.
The inclusive 3-JET cross section as a function of Bjorken scaling variableX for the Q**2 range 5 to 100 GeV**2.
Jet production in charged and neutral current events in the kinematic range of Q^2 from 640 to 35000 GeV^2 is studied in deep-inelastic positron-proton scattering at HERA. The measured rate of multi-jet events and distributions of jet polar angle, transverse energy, dijet mass, and other dijet variables are presented. Using parton densities derived from inclusive DIS cross sections, perturbative QCD calculations in NLO are found to give a consistent description of both the neutral and charged current dijet production. A direct, model independent comparison of the jet distributions in charged and neutral current events confirms that the QCD dynamics of the hadronic final state is independent of the underlying electroweak scattering process.
Rates of charged current events as a function of Q**2.
Rates of neutral current events as a function of Q**2.
Normalised distribution in Y2 for NC and CC dijet events. Y2 is the smallest scaled value of KT (KTJET**2/W**2) given by the combination of (2+1) jets. The +1 refers to the proton remnant jet.
An analysis of the data collected in 1997 and 1998 with the DELPHI detector at e+e- collision energies close to 183 and 189 GeV was performed in order to extract the hadronic and leptonic fermion-pair cross-sections, as well as the leptonic forward-backward asymmetries and angular distributions. The data are used to put limit on contact interactions between fermions, the exchange of R-parity violating SUSY sneutrinos, Z' bosons and the existence of gravity in extra dimensions.
No description provided.
No description provided.
No description provided.
The electroproduction of rho mesons with proton diffractive dissociation for Q^2 > 7 GeV^2 and the elastic electroproduction of Phi mesons for Q^2 > 6 Gev^2 are studied in e^+ p collisions at HERA with the H1 detector, for an integrated luminosity of 2.8 pb-1. The dependence of the cross sections on P_t^2 and Q^2 is measured, and the vector meson polarisation obtained. The cross section ratio between proton dissociative and elastic production of rho mesons is measured and discussed in the framework of the factorisation hypothesis of diffractive vertices. The ratio of the elastic cross section for Phi and rho meson production is investigated as a function of Q^2.
Corrected PT**2 distribution for RHO production from the proton dissociative sample. Statistical errors only.
Cross sections and ratio of proton dissociative to elastic cross sections.
Cross sections and ratio of proton dissociative to elastic cross sections.
The total cross sections for the elastic electroproduction of $\rh0$ and $J/\Psi$ mesons for $Q~2$ $>$ 8 GeV$~2$ and $\langle W \rangle \simeq 90$ GeV/c$~2$ are measured at HERA with the H1 detector. The measurements are for an integrated electron$-$proton luminosity of $\simeq$3pb$~{-1}$. The dependences of the total virtual photon$-$proton ($\gamma~* p$) cross sections on $Q~2$, $W$ and the momentum transfer squared to the proton ($t$), and, for the $\rho$, the dependence on the polar decay angle ($\cos \theta~*$), are presented. The $J/\Psi$ : $\rh0$ cross section ratio is determined. The results are discussed in the light of theoretical models and of the interplay of hard and soft physics processes.
Overall EP cross section for M(PI+PI-) < 1.5 GEV.
Overall EP cross section, taking into account the J/PSI --> LEPTON+ LEPTON - branching fraction 0.12.
Integrated EP cross section.
The cross section for the elastic photoproduction of \r0\ mesons ($\gamma p \rightarrow \rho~0 p$) has been measured with the H1 detector at HERA for two average photon-proton centre-of-mass energies of 55 and 187GeV. TheFcenterline lower energy point was measured by observing directly the $\rho~{0}$ decay giving a cross section of $9.1\pm 0.9\,(\stat)\pm 2.5\,(\syst)\;\mu$b. The logarithmic slope parameter of the differential cross section, ${\rm d}\sigma/{\rm d}t$, is found to be $10.9 \pm 2.4\,(\stat) \pm 1.1\,(\syst)\;$GeV$~{-2}$. The \r0\ decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be $13.6\pm 0.8\,(\stat)\pm 2.4\,(\syst)\;\mu$b.
PI+ PI- cross section.
RHO0 cross section by selecting Mpipi to lie between 2Mpi and Mrho + 5width0.
No description provided.
Using the CELLO detector, we have measured cross sections for the processγγ→π+π− in the mass range 0.75–1.9 GeV/c2. A partial wave fit to the data indicates the presence of a sizeableS-wave amplitude with signs of resonant behaviour. Values for the γγ width of thef2(1270) are given, showing the model-dependence of this quantity. At higher dipion masses, the model of Brodsky and Lepage is found to give an order of magnitude description of the data.
No description provided.
No description provided.
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