Search

Zeitschrift für Physik / C 69(3), 405-408 (1996). doi:10.1007/BF02907420, Using the ARGUS detector at the e+e− storage ring DORIS II at DESY we have measured the parameters of a charmed strange meson D*s2+(2573) decaying into D0K+. The mass of this state was found to be (2574.5±3.3±1.6) MeV/c2. The measured value of its width is (10.4±8.3±3.0) MeV and the product of the production cross section and branching ratio for this channel was determined to be (10.6±4.2−1.2+2.3) pb., Published by Springer, Heidelberg

16 pp. (1996)., We use the BLM scale-fixing prescription to derive a renormalization-scheme invariant relation between the coefficient function for the Bjorken sum rule for polarized deep inelastic scattering and the $R$-ratio for the $e^+ e^−$ annihilation cross section. This relation provides a generalization of the Crewther relation to non-conformally invariant gauge theories. The derived relations allow one to calculate unambiguously without renormalization scale or scheme ambiguity the effective charges of the polarized Bjorken and the Gross-Llewellen Smith sum rules from the experimental value for the effective charge associated with $R$-ratio. Present data are consistent with the generalized Crewther relations, but measurements at higher precision and energies will be needed to decisively test these fundamental relations in QCD.

28 pp. (1996)., The various four-fermion production channels in e + e − annihilation are discussed and the CC11 process $e^+e^- \to \bar f_{1}^{u}f_{1}^{d}f_{2}^d\bar f_{2}^{d}≠ e$ , is studied in section $d^2\sigma/ds_1 ds_2$ , with $s_1 , s_2$ being the invariant masses squared of the two fermion pairs, may be expressed by six generic functions. All but one may be found in the literature. The cross section, including initial-state radiation and the Coulomb correction, is discussed and compared with other calculations from low energies up to √ s = 2 TeV.

11 pp. (1996)., We describe the program package gentle/4fan, which consists of the Fortran codes gentle\_4fan.f, 4fan.f, and gentle\_nc\_qed.f and is devoted to the description of e+ e- annihilation into four fermions. The codes are based on the semi-analytical approach. Initial state QED corrections are taken into account. The program versions, which are described here were used in the 1995 workshop `Physics at LEP2'.

8 pp. (1996)., We give a short review of the results for four fermion production, which have been obtained by the semi-analytical approach. The angular degrees of freedom (typically five or more) are integrated over analytically while the integrations over invariant fermion pair masses (typically two or more) remain to be performed by numerical methods. In addition to doubly resonating cross sections from virtual two boson production, QED corrections and background contributions were determined. However, a large variety of final state topologies has not been treated so far.

7 pp. (1996)., Constraints on extra neutral gauge bosons are obtained from $e^+e^-\rightarrow f\bar f$ at NLC energies. Model independent limits on the $Z'f\bar f$ couplings and lower limits on the $Z'$ mass are discussed. Typical GUTs with $M_{Z'}$ up to (3 -- 6) $\sqrt{s}$ can be excluded. A distinction between different GUT scenarios is possible if $M_{Z'}\le 3\sqrt{s}$. Radiative corrections give only small changes to the $Z'$ exclusion limits provided that appropriate cuts are applied.

14 pp. (1996)., Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, we have made two measurements of the mixing parameter χ d using kaons as flavour tags. Using D ∗+ K ± correlations we found χ d = 0.20 ± 0.13 ± 0.12 and from the study of (D ∗+ ℓ − ) K ± correlations we obtained χ d = 0.19 ± 0.07 ± 0.09. The branching ratio for B → D ∗+ X has been updated: Br( B → D ∗+ X) = (19.6 ± 1.9) %. We have also determined the average multiplicity of charged kaons in B 0 decays to be 0.78 ± 0.08.

41 pp. (1996)., A new Monte Carlo event generator for wide angle Bhabha scattering and muon pair production in $e~+e~-$ collisions is described. The program includes complete one-loop electroweak corrections, and QED radiative corrections. The O($\alpha$) QED correction uses the exact matrix element. Higher order QED corrections are included in an improved soft photon approximation with exponentiation of initial state radiation. Events are generated in the full phase space of the final state including explicit mass effects in the region of collinear mass singularities. The program is intended for centre of mass energies around and above the Z peak and for Bhabha scattering at angles greater than $10~{\circ}$ .

In two-photon collisions at LEP2 and a future e + e − linear collider heavy quarks (mainly charm) will be pair-produced rather copiously. The production via direct and resolved photons can be distinguished experimentally via a remnant-jet tag. We study correlations of the heavy quarks at next-to-leading order in QCD in the direct channel, which is free from phenomenological parton densities in the photon. These correlations are therefore directly calculable in perturbative QCD and provide a stringent test of the production mechanism.

6 pp. (1996)., Using the ARGUS detector at the e + e − storage ring DORIS II, we have measured the semileptonic branching ratios of the D 0 meson to be Br ( D 0 → e + ν e X ) = (6.9 ± 0.3 ± 0.5) % and Br ( D 0 → μ + ν μ X ) = (6.0 ± 0.7 ± 1.2) %, and the semileptonic branching ratio of the charmed hadron mixture from e + e − annihilation around 10 GeV to be Br ( c → e + ν e X ) = (9.6 ± 0.4 ± 1.1) %.

11 pp. (1995)., Lepton spectra in τ decays have been studied with the ARGUS detector at thee+e− storage ring DORIS II at DESY using the “pseudo-rest-frame” technique. We have improved upper limits for two-body τ-decays into a lepton and an unobservable particle.

27 pp. (1995)., A complete tree-level calculation of the reaction in the electroweak standard theory for the energy range of LEP200 and the Next Linear Collider is presented. The matrix elements were calculated by means of the package CompHEP, and phase space integration and event generation were carried out with the computer programs BASES/SPRING. Cross sections for the final state, the rate for Higgs production and for different background contributions are studied as a function of the cms energy and the Higgs mass in the range from 80 to 140 GeV. At LEP200 energies, the Higgs bremsstrahlung reaction and the two-body process e+e−→ZZ are dominant while near 500 GeV the Higgs fusion and two-to-three body background processes govern the final state. Interference patterns were searched for and found to be negligible except for , where interferences are found to be of comparable strength with the Higgs signal diagrams. Some cancellations between different background diagrams are observed which are expected within the Standard Model. Missing transverse momentum and visible energy distributions for the final state indicate some further possibilities of removing background for Higgs searches. A suggestion for an approximate treatment of the reaction is presented so that much computer time can be saved in Monte Carlo simulations.

9 pp. (1995)., Using the ARGUS detector at the storage ring DORIS II we have measured τ decays into three charged mesons containingK* mesons. Exploiting the good particle identification capabilities of the detector we have determined the following branching ratios:\(Br\left( {\tau ^ -\to \overline {K^{*0} } \pi ^ -v_\tau} \right) = \left( {0.25 \pm 0.10 \pm 0.05} \right)\% \),Br(τ−→K*0K−vτ)= (0.20±0.05±0.04)%, andBr(τ−→K*−X0vτ) =(1.15±0.15−0.18+0.13)%.

11 pp. (1995)., The measurement of the forward-backward asymmetries of heavy quarks provides one of the most precise determinations of $\sin~2\theta_W$ in $Z$ decays. We discuss in detail the one--loop QCD radiative corrections to these asymmetries. Results are given for single heavy--quark jet asymmetries and asymmetries of the thrust axis, as well as for heavy--quark two--jet final states.}

10 pp. (1995)., The cross sections for the reaction e + e − → l l q q and for similar four fermion production processes at LEP 1, LEP 2 and the NLC are calculated. Due to the extraordinary symmetry properties of the process, very compact analytical formulae describe the double differential distributions in the invariant masses of the l l and q q pairs. The total cross sections may be obtained with two numerical integrations.

24 pp. (1995)., SMATASY is an interface for the ZFITTER package and may be used for the model independent description of the Z resonance at LEP 1 and SLC. It allows the determination of the Z mass and width and its resonance shape parameters r and j for cross-sections and their asymmetries. The r describes the peak height and j the interference of the Z resonance with photon exchange in each scattering channel and for $\sigma_T$, $\sigma_{FB}$, $\sigma_{lr}$, $\sigma_{pol}$ etc. separately. Alternatively, the helicity amplitudes for a given scattering channel may be determined. We compare our formalism with other model independent approaches. The model independent treatment of QED corrections in SMATASY is applicable also far away from the Z peak.

8 pp. (1995)., Predictions for Higgs production with processes of the type e + e − → μ μ b b at LEP 2 and the NLC are calculated. Short analytical formulae describe the double differential distribution in the invariant masses of the μ μ and b b pairs. The total cross section may be obtained with two numerical integrations. The various Higgs-background interferences vanish either identically or are small. The background contributions depend strongly on cuts applied to the invariant masses.

11 pp. (1995)., We evaluate the two-loop O ( α s G F m t 2 ) correction to the ZZH coupling in the Standard Model by means of a low-energy theorem, assuming that the top quark is much heavier than the Higgs boson. We then construct a heavy-top-quark effective Lagrangian for the ZZH interaction that accommodates the O ( G F m t 2 ) and O ( α s G F m t 2 ) corrections and derived from it the corresponding corrections to the H → ZZ decay as well as those to Higgs-boson production at LEP1, via Z → ƒ ƒ H and at LEP2, via e + e − → ZH . In all cases, the leading O ( G F m t 2 ) terms are considerably screened by their QCD corrections, if the on-shell renormalization scheme with G F as a basic parameter is employed.

Proceedings, Workshop, Annecy, Gran Sasso, Hamburg, Hamburg, Germany, 4 Feb 1995 - 1 Sep 1995 ; (1995).

152 pp. (1995)., A novel approach to study electroweak physics at one-loop level in generic ${\rm SU(2)_L \times U(1)_Y}$ theories is introduced. It separates the 1-loop corrections into two pieces: process specific ones from vertex and box contributions, and universal ones from contributions to the gauge boson propagators. The latter are parametrized in terms of four effective form factors $\bar{e}^2(q^2)$, $\bar{s}^2(q^2)$, $\bar{g}_Z^2(q^2)$ and $\bar{g}_W^2 (q^2)$ corresponding to the $\gamma\gamma$, $\gamma Z$, $ZZ$ and $WW$ propagators. Under the assumption that only the Standard Model contributes to the process specific corrections, the magnitudes of the four form factors are determined at $q~2=0$ and at $q^2=m^2_Z$ by fitting to all available precision experiments. These values are then compared systematically with predictions of ${\rm SU(2)_L \times U(1)_Y}$ theories. In all fits $\alpha_s(m_Z)$ and $\bar{\alpha}(m_Z^2)$ are treated as external parameters in order to keep the interpretation as flexible as possible. The treatment of the electroweak data is presented in detail together with the relevant theoretical formulae used to interpret the data. No deviation from the Standard Model has been identified. Ranges of the top quark and Higgs boson masses are derived as functions of $\alpha_s(m_Z)$ and $\bar{\alpha}(m^2_Z)$. Also discussed are consequences of the recent precision measurement of the left-right asymmetry at SLC as well as the impact of a top quark mass and an improved $W$ mass measurement.

19 pp. (1995)., Deep inelastic scattering (DIS) events, selected from 1993 data taken by the H1 experiment at HERA, are studied in the Breit frame of reference. The fragmentation function of the quark is compared with those of e + e − data. It is shown that certain aspects of the quarks emerging from within the proton in e − p interactions are essentially the same as those of quarks pair-created from the vacuum in e + e − annihilation. The measured area, peak position and width of the fragmentation function show that the kinematic evolution variable, equivalent to the e + e − squared centre of mass energy, is in the Breit frame the invariant square of the four-momentum transfer. We comment on the extent to which we have evidence for coherence effects in pArton showers.

University of Glasgow, Diss., 1995; 173 pp. (1995). = University of Glasgow, Diss., 1995

24 pp. (1995)., We present low-energy theorems for the calculation of loop amplitudes with external scalar or pseudoscalar Higgs bosons which are light compared to the loop particles. Starting from existing lowest-order versions of these theorems, we show how their applicability may be extended to the two--loop level. To illustrate the usefulness of these theorems, we discuss a number of applications to Higgs production and decay at and beyond the one--loop order.

10 pp. (1995)., Leptons, quarks and gauge bosons are assumed to be pointlike particles in the Standard Model. Stringent bounds on the radii of quarks and leptons and their weak anomalous magnetic moments can be derived from the high-precision measurements at LEP and SLC. We find a model-independent bound ofR≲10−17 cm for quark and lepton radii. HERA will provide complementary information on the electromagnetic static properties of the quarks and the parameters of the charged quark currents.

33 pp. (1995)., We present new sets of fragmentation functions for charged pions and kaons, both at leading and next-to-leading order. They are fitted to TPC data taken at energy $\sqrt s=3D29$GeV and describe excellently a wealth of other $e~+e~-$ data on charged-hadron production, ranging from $\sqrt s=3D5.2$GeV way up to LEP1 energy. They also agree with data on the production of neutral pions and kaons, if one makes the natural assumption that the respective fragmentation funct= ions are related to the charged counterparts by SU(2) symmetry. We also list simple parameterizations of the $x$ and $Q~2$ dependence of our results, which may be implemented conveniently in applications.

The cross-section for the reaction $e^+e^- \rightarrow b\bar{b}\mu^+\mu^-$ is calculated with a semi-analytical integration of the phase space. Compact formulae are obtained for the total cross section and for invariant mass distributions of the $\mu^+\mu^-$ and $b\bar{b}$ pairs. The background diagrams to $ZH$ production yield analytically cumbersome but numerically small contributions. The numerical results are compared with those from a Monte Carlo approach., Comment: 6 latex pages; 3 figures, feinman.sty and nuclphys.sty included as uuencoded file, CERN-TH.703/94, LMU 08/94

Technische Universitat Braunschweig, Diplomarbeit, 1994; 93 pp. (1994). = Technische Universitat Braunschweig, Diplomarbeit, 1994

37 pp. (1994)., We analyze the prospects of measuring the parity of Higgs particles in the Standard Model and its supersymmetric extensions. Higgs decays are discussed in this context as well as production processes including, in particular, the fusion of Higgs particles in linearly polarized photon--photon collisions.

6 pp. (1994)., A study of the Standard Model reaction $\mathrm{e}^+\mathrm{e}^- \rightarrow (\mathrm{Z}^0\mathrm{Z}^0) \rightarrow f_1\bar{f_1}f_2\bar{f_2}$ including the effects of the finite $\mathrm{Z}^0$~width and initial state radiative corrections is presented. All angular phase space integrations are performed analytically. The remaining invariant masses are integrated numerically. Semi-analytical and numerical results in the energy range $\sqrt{s}=200\;$GeV to $1\;$TeV are reported.

10 pp. (1994)., A study of the semi-analytical approach to four-fermion production in $e^+ e^−$ annihilation is presented. We classify all possible four-fermion final states and present results of new calculations for the ‘basic’ processes with the $WW$ , $ZZ$ , and $ZH$ off-shell production together with some examples of ‘background’ processes. The Initial State Radiative corrections are included for the basic processes. Several numerical examples are given in the energy range from LEP 2 up to $\sqrt{s} = 1$ TeV .

16 pp. (1994)., A complete tree-level calculation of the reaction\(e^ +e^ -\to \mu ^ +\mu ^ -b\bar b\) in the electroweak standard theory for the energy range of LEP200 and the next linear collider is presented. The matrix elements have been calculated by employing the computer program CompHEP, the phase space integrals by the Monte Carlo integrator and event generator BASES/SPRING. The dependence of the 4-fermion cross section on energy and the Higgs boson mass is studied in detail. Interference contributions between the various diagrams are found not to alter significantly the production and decay properties of the Higgs boson. It is shown that already the counting rate of the reaction\(e^ +e^ -\to \mu ^ +\mu ^ -b\bar b\) at LEP200 can provide evidence for the existence of the Higgs boson.

10 pp. (1994)., Model independent constraints on the mass of extra neutral gauge bosons and their couplings to charged leptons are given for LEPII and a 500\,GeV $e~+e~-$ collider. Analytical exclusion limits are derived in the Born approximation. The $Z'$ limits obtained with radiative corrections are always worse than those calculated at the Born level. Polarized beams are only useful for degrees of polarization essentially larger than 50\%. Known discovery limits on extra $Z$ bosons predicted by popular $Z'$ models are reproduced as special cases. The $Z'$ constraints are compared to those predicted by four fermion contact interactions.

We collect and update theoretical predictions for the production rate and decay branching fractions of the Standard Model Higgs boson that will be relevant for the Higgs search at LEP200. We make full use of the present knowledge of radiative corrections. We estimate the systematics arising from theoretical and experimental uncertainties., 27 pages

10 pp. (1994)., The possibility of grand unification of the standard model (SM) with fermion spectrum extended to include mirror fermions is examined. SM gauge couplings do not automatically unify. SO(10) grand unification is studied with one intermediate scale. Renormalization group equations (RGE) for fermion Yukawa couplings and the scalar self-coupling are studied numerically at one and two loop level. Strong restrictions for mirror fermion masses are obtained assuming perturbative unification. Mirror masses much smaller than the tree unitarity bounds are required. In particular mirror leptons have to be around 50 GeV. Consistency of the mirror fermion model with LEP precision data is established. A direct search for single production of mirror neutrinos at LEP could exclude or confirm the GUT version of the mirror fermion model.

31 pp. (1994). doi:10.3204/PUBDB-2017-05373, We elaborate on the production of the Standard Model Higgs particle at high-energy $e~+e~-$ colliders through the reaction $e~+e~- \rightarrow ZH$. Particular emphasis is put on the intermediate mass range. In addition to the signal we discuss in detail the background processes. Angular distributions which are sensitive to the spin and parity of the Higgs particle are analyzed.

79 pp. (1994)., We review the status of the theoretical predictions for W-pair production in e+e− collisions within the electroweak standard model (SM). We first consider for on-shell W bosons the lowest-order cross-section within the SM, the general effects of anomalous couplings, the radiative corrections within the SM, and approximations for them. Then we discuss the inclusion of finite-width effects in the lowest order and the existing results for radiative corrections to off-shell W-pair production, and we outline the general strategy for calculating radiative corrections within the pole scheme. We summarize the theoretical predictions for the total and partial W-boson widths including radiative corrections and discuss the quality of an improved Born approximation. Finally, we provide a general discussion on the structure-function method for calculating large-logarithmic higher-order corrections associated with collinear photon radiation.

9 pp. (1993)., The Higgs sector of the minimal supersymmetric extension of the standard model (MSSM) becomes phenomenologically hard to distinguish from the standard model (SM) in the limit that the CP-odd scalar,A0, is much heavier than theZ boson. If, in addition, all the superpartners lie outside the kinematic reach of present-day (or near-future) colliders the only experimental evidence for supersymmetry (SUSY) might be through internal loops involving superpartners. We have calculated sfermion-induced radiative corrections toe+e−→Zh0 andZ→γh0 in the MSSM, which are enhanced for highmt.

Universität Hamburg, Diplomarbeit, 1993; 65 pp. (1993). = Universität Hamburg, Diplomarbeit, 1993

78 pp. (1993)., The authors review and update results bearing on the phenomenon of particle-antiparticle mixing in the neutral beauty meson sector. Their main focus is on the mixing ratio xs, defined as xs=( Delta M)/ Gamma , relevant for Bs0-Bs0 mixing. They present theoretical estimates of this quantity in the standard model (SM) and find that xs=O(10), which makes time-dependent oscillation measurements mandatory. They also discuss estimates of xs in a number of extensions of the SM, some of which admit smaller values of xs. Present and future experimental facilities where such measurements can be undertaken are reviewed on a case-to-case basis. These include the high luminosity LEP option, asymmetric threshold B-factories, the ep collider HERA, and hadron colliders, such as the Fermilab Tevatron, LHC and SSC.

9 pp. (1993)., Using the ARGUS detector at the e+e− storage ring DORIS II, we have determined the Michel parameters ϱ and ξ of τ → μννandτ → eνν decays. From a data sample with 333 events/pb around s= 10GeV, we select 3230 events ǂe+e−→ τ+τ−→ (μ±μμ)(eǂvv) and determine ϱ from the e and μ momentum spectra and ξ from the correlations between e and μ momenta. For ϱ we obtain ϱτ→e = 0.79 ± 0.08 ± 0.06 and ϱτ→μ = 0.76 ± 0.08 in accordance with the V - A structure of the decays. The momentum correlations are only sensitive to the product ξτ→eξτ→μ. Setting ξτ→e = ξτ→μ, we obtain |ξτ| = 0.90 ± 0.15 ± 0.10 also in accordance with V - A. The updated decay fractions are B(τ →evv) = (17.5 ± 0.3 ± 0.5)% and B(τ → μvv) = (17.4 ± 0.3 ± 0.5)%.

19 pp. (1993)., Using the detector ARGUS at the $e^+e^−$ storage ring DORIS II, we have investigated inclusive momentum spectra of charged pions, kaons, and protons from decays of the υ(4S) meson. The kaon spectra have been measured in two independent ways, by coherently exploiting the detector's particle identification capabilities, and by detecting decays in-flight. The extracted mean multiplicities for charged hadrons are 7.17±0.05±0.14 pions, 1.56±0.03±0.05 kaons and 0.110±0.010±0.007 protons per υ(4S) decay, where pions and protons fromKso and Δ decays have been subtracted.

8 pp. (1993)., Using the ARGUS detector at the e+e− storage ring DORIS II at DESY, we have observed a new charmed baryon state in the channel Λc+π+π−. (All references to a specific charged state also imply the charge conjugate state.) The mass of this state was measured to be (2626.6 ± 0.5 ± 1.5) MeV/c2. The product of the production cross section and branching ratio for this channel was determined to be (11.5 ± 2.5 ± 3.0) pb, and the natural width estimated to be smaller than 3.2 MeV/c2 at 90% CL.

31 pp. (1993)., We discuss the Higgs scenario in the minimal supersymmetric extension of the Standard Model ate+e− linear colliders operating in the c.m. energy range between 300 and 500 GeV. Besides decays of the Higgs particles into ordinary fermions and cascade decays, we analyze also decays into gaugino/Higgsinos and in particular, neutral Higgs decays into the lightest supersymmetric particles which are invisible ifR-parity is conserved. The cross sections for the various production channels of SUSY Higgs particles ine+e− collisions are discussed in detail. The lightest Higgs boson cannot escape detection, and in major parts of the MSSM parameter space all five Higgs particles can be observed.

22 pp. (1993)., Using the ARGUS detector at the DORIS II $e^+e^−$ storage ring we have studied the three-pion hadronic final state in the decay $τ^- → π^-π^-π^+v_τ$. From about 7500 events we conclude that the three-pion system is dominated by the $J^P=1^+$ resonancea1 (1260) decaying preferentially via $ρ^0π^-$. Our data restrict a possible ρπ contribution of three-pion states without intermediate resonances to less than 6% at 95% CL. Fitting a model by Isgur et al. to the data yieldsma1=(1.211±0.007±0.0500.0)GeV/c$^2$ and $Γ$a1=(0.446±0.0021±0.1400.0)GeV/c$^2$. The second errors reflect the model dependence of the result. This is the currently most significant determination of thea1 resonance parameters. The ratio ofS- and D-wave amplitudes for the ρ0π- intermediate state of thea1− decay at the nominala1− mass was found to beD/S=−0.11±0.02. Using thisD/S ratio we update our former measurement of the parity violating asymmetry parameterγ $AV=2gAgV/(g^2_A+g^2_V)$ to 1.25±0.23±0.080.15. The branching ratio of the decay $τ^- → π^-π^-π^+v_τ$ is determined to be Br($τ^- → π^-π^-π^+v_τ$)=(6.8±0.1±0.5)%.

12 pp. (1993)., With a current-splitting technique, we calculate the gauge-invariant initial-state radiation to order O(α) with soft-photon exponentiation for on- and off-shell W-pair production. This result generalizes the convolution formula, which is known from the description of the Z resonance, to the case of the production of two W-bosons. After up to eightfold analytical integrations, a sufficiently smooth integral over three invariant masses remains to be treated numerically. Including the Coulomb singularity, the largest corrections are covered. We discuss the corrections in a large energy range up to √s = 1 TeV and draw numerical conclusions on their influence on the W-mass determination at LEP 200.

Universität Hamburg, Diss., 1993; 75 pp. (1993). = Universität Hamburg, Diss., 1993

16 pp. (1993)., A search has been performed for rareB meson decays intoDs− mesons arising fromb→u transitions,W exchange modes,B+ annihilation processes, and decays where theDs+ is not produced via aW→c s¯s¯ quark pair coupling, using the ARGUS detector operating on the Ψ(4S) resonance at thee+e− storage ring DORIS II. Upper limits for individual decay modes are obtained. In addition, from a study ofDs+ℓ- correlations an upper limit of BR (B→Ds+ℓ-X) (90% CL) is determined.

6 pp. (1993)., We calculate the gauge-invariant initial-state lowest order, $\mathcal O(\alpha)$ radiative corrections for on- and off-shell W-pair production. The soft photon inclusive exponentiation is included. This result generalizes the convolution formula, which is know from the description of the $Z$ resonance, to the case of the production of two $W$-bosons. Including the Coulomb singularity, the dominant corrections are covered. We present numerical results in a large energy range from LEP 200 up to NLC, $\sqrt s = 1$ TeV.

131 pp. (1993)., We present a synopsis of Higgs-boson phenomenology at one loop in the standard model. Two-loop effects are reported on as far as present knowledge goes. The phenomena are classified according to the number of external particles participating in the interaction. The relevant classes correspond to two-, three-, four-, and five-point functions. Two-point functions are the source of indirect evidence for the Higgs boson; three-point functions control its two-body decays and its production through fusion processes at hadron and photon colliders; four-point functions trigger its three-body decays and its associated production with another particle that balances the quantum numbers or serves as a signal; five-point functions mediate Higgs-boson four-body decays and production from intermediate-boson fusion at hadron, ep, and e+e− colliders. Of course, the study of quantum corrections to these processes is interesting in its own right, since it provides a deeper insight into the completely untested Higgs sector of the electroweak theory. However, in some cases the effects are very significant and their neglect leads to rather inadequate predictions, e.g., in the case of the H → bb decay or the gluon-fusion mechanism. The purpose of this article is to deliver a broad review of the quantum effects related to the Higgs boson, to highlight their phenomenological relevance, to list the most important formulae for quick reference, and to generate a rich bibliography, so that the interested reader can find the source of the results. We shall illustrate the effects in numerous figures and investigate various limiting cases, e.g., light or heavy virtual fermions, a heavy Higgs boson, etc. For the reader's convenience, we shall collect the relevant two-, three-, and four-point loop integrals as well as the boson vacuum polarizations and fermion self-energies in a number of appendices.

13 pp. (1993)., Using the ARGUS detector at the DORIS-II electron-positron storage ring at DESY, we have investigated the exclusive decay $D∗+→ D^0 π^+, D^0→ K_S^0 π^+π^−$. From a partial wave analysis of the $K_S^0 π+^π^−$ system we find that (71.8± 4.2 ± 3.0)% are $D^0→ K∗^−π^+$ and (22.7 ± 3.2 ± 0.9)% are $D^0→K^0_ϱ 0$ with a relative phase of (−137 ± 7 ± 3)° between the channels. The remaining fraction can be described by several channels involving excited resonances, but not by a three-body phase space decay, thus giving first evidence for D0 decays into $K^0_∗(1430)^−π^+,K^0f^0(1975), K^0f^2(1270), and K^0f^0(1400)$.