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The aim of this study is to investigate the possibility of assessment of the effect of preparatory surface plastic deformation by hydraulic shot blasting on the fatigue strength of cylindrical parts of different diameters (10-40 mm) of D16T alloy with circular notches of semicircular section, based on measurements of residual stress (initial deformations) of a witness sample. The residual stresses of smooth parts were used to calculate the residual stresses of parts with stress raisers. These were used to predict the increment of these parts fatigue limit caused by hardening hydraulic shot blasting. It was found that the highest compressive residual stresses in the smooth parts obtained through calculations differ from the observed values not more than by 7%, and in notched parts by 8%. Using the criterion of mean integral residual stresses, we calculate the increments of the fatigue limit of parts due to superficial hardening. The discrepancy between the experimental and calculated increment values of the fatigue limit of hardened parts with raisers does not exceed 17%.

A search for the pair production of fourth generation b'-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging from 196 to 209 GeV, corresponding to an integrated luminosity of 420 pb⁻1. No evidence for a signal was found. Upper limits on BR(b' -> bZ) and BR(b' -> cW) were obtained for b' masses ranging from 96 to 103 GeV/c². These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of R_(C)KM=|V_(c)b'/V_(t)b'V_(t)b|, where V_(c)b', V_(t)b' and V_(t)b are elements of the extended CKM matrix.

The production of single photons has been studiedin the reaction e+e- –> gamma+ invisible particles at centre-of-mass energies of 183 GeV and 189 GeV.A previously published analysis of events with multi-photonfinal states accompanied by missing energy has been updated with 189 GeV data.The data were collected with the DELPHI detector and correspondto integrated luminosities of about 51 pb⁻1and 158 pb⁻1at thetwo energies.The number of light neutrino families is measured to be2.860.13(stat)0.14(syst). The absence ofan excess of events beyond that expected from Standard Modelprocesses is used to set limits on new physicsas described by supersymmetric and composite models.A limit on the gravitational scale is also determined.

A search for excited lepton production in e+e- collisions was performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies ranging from 189 GeV to 209 GeV, corresponding to an integrated luminosity of approximately 600 pb⁻1. No evidence for excited lepton production was found. In searches for pair-produced excited leptons, lower mass limits were established in the range 94 - 103 GeV/c², depending on the channel and model assumptions. In searches for singly-produced excited leptons, upper limits on the parameter f/Lambda were established as a function of the mass.

An experimental study of the normalized three-jet rate of b quark events with respect to light quark events (light= l = u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_(b) and the b running mass: m_(b)(M_(Z)). Data are found to be better described when using the running mass. The measurement yields: m_(b)(M_(Z)) = 2.95 +- 0.18(stat) +- 0.13(exp) +- 0.19(had) +- 0.12(theo) GeV/c2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determination by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independance of the strong coupling constant with an accuracy of 7 per mille

Double-tagged interactions of photons with virtualities Q² between 10GeV² and 200GeV² are studied with the data collected by DELPHI at LEP2 from 1998 to 2000, corresponding to an integrated luminosity of 550pb⁻1. The gamma*gamma* -> mu+mu- data agree with QED predictions. The cross-section of the reaction gamma*gamma* -> hadrons is measured and compared to the LO and NLO BFKL calculations.

Theτpolarisation has been studied with the\\eett{}{d}{a}ta collected by the DELPHI detector at LEP in 1993, 1994 and 1995 around the\\Z{}{r}{e}sonance firstly through the exclusive decay channels\\mbox{\\rm e}{ν}{ν̄} ,μνν̄ ,πν ,ρνand\\aone{ν}{}{a}nd secondly with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision. The results have been combined with those previously published on 1990 to 1992 DELPHI data, to produce results which reflect the full LEP-1 statistics. The fit of theτpolarisation dependence on the production angle yielded the polarisation parameters\\atau{=}{0}{.}1359 ± 0.0096andæle=0.1382 ± 0.0116 . From these results the ratio of the vector and axial-vector effective couplings\\barvt / \\barat = 0.0683±0.0048and\\barve / \\barae = 0.0694±0.0058have been derived, compatible with e -τuniversality. With the assumption of lepton universality,the ratio of vector to axial-vector effective couplings for leptons\\barvl / \\baral = 0.0687±0.0037was obtained, implying a value of the effective weak mixing angle\\s{2}{t}{h}w = 0.23282±0.00092 .

The probability P(c --> D*(+)) that a charm quark fragments into a D*+ meson and the c --> l(+) semileptonic branching fraction were measured in Z(0) decay into c (c) over bar events. From the analysis of 3.5 Million Z(0) events collected from 1992 to 199