Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Search for charginos in e+e- interactions at sqrt(s) = 189 GeV

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure

Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure

Limits on the production of scalar leptoquarks from Z (0) decays at LEP

A search has been made for pairs and for single production of scalar leptoquarks of the first and second generations using a data sample of 392000 Z0 decays from the DELPHI detector at LEP 1. No signal was found and limits on the leptoquark mass, production cross section and branching ratio were set. A mass limit at 95% confidence level of 45.5 GeV/c2 was obtained for leptoquark pair production. The search for the production of a single leptoquark probed the mass region above this limit and its results exclude first and second generation leptoquarks D0 with masses below 65 GeV/c2 and 73 GeV/c2 respectively, at 95% confidence level, assuming that the D0lq Yukawa coupling alpha(lambda) is equal to the electromagnetic one. An upper limit is also given on the coupling alpha(lambda) as a function of the leptoquark mass m(D0)

Updated precision measurement of the average lifetime of B hadrons

The measurement of the average lifetime of B hadrons using inclusively reconstructed secondary vertices has been updated using both an improved processing of previous data and additional statistics from new data. This has reduced the statistical and systematic uncertainties and gives \tau_{\mathrm{B}} = 1.582 \pm 0.011\ \mathrm{(stat.)} \pm 0.027\ \mathrm{(syst.)}\ \mathrm{ps.} Combining this result with the previous result based on charged particle impact parameter distributions yields \tau_{\mathrm{B}} = 1.575 \pm 0.010\ \mathrm{(stat.)} \pm 0.026\ \mathrm{(syst.)}\ \mathrm{ps.

The origin of variations in the isotopic record of scleractinian corals: II. Carbon

This study examines the relationship between theδ13C of the skeleton of a zooxanthellate coral (Montastraea annularis) growing on the Florida Reef Tract and environmental variables (insolation and temperature), physiological variables (growth rate, respiration, calcification, and photosynthesis). Colonies of this species were grown in the field for a212year study period, during which the rates of photosynthesis, respiration, and calcification were measured on fifteen separate occasions, spaced approximately equally throughout the study period. The corals were stained with alizarin-red S within seven days after each set of physiological measurements. At the end of the period the corals were sacrificed and their skeletal extension, density, and skeletalδ13C determined. Despite substantial high-frequency variations, a strong seasonal cycle was evident in the skeletalδ13C records of all the corals throughout the experimental period. The skeletalδ13C andδ18O values varied approximately in phase, and showed a weak, but statistically significant positive relationship with each other. Theδ13C of the coral skeletons, when corrected for changes in theδ13C of dissolved inorganic carbon (DIC), exhibited an inverse correlation with P/R, a finding opposite to what was expected based on current models of isotopic fractionation in coral skeletons. Although such findings tend to support the model of Erez (1978) that increases in photosynthesis act to isotopically deplete theδ13C of the coral skeleton, we note that the inverse association betweenδ13C and P/R arises because of a slight positive association betweenδ13C and respiration. We therefore believe that the association may be a result of seasonal variation in some parameters of the system which was not constrained in our study. Alternatives include (1) variations in theδ13C of the DIC which are translated into theδ13C of the food chain, (2) changes from heterotrophy to autotrophy, and (3) changes in the partitioning ofδ13C between the zooxanthellae and the coral tissue. Based on previous studies which we have carried out we believe that changes in the skeletalδ13C are not related to sexual reproduction or growth rate. Contrary to previous work we were unable to measure any significant differences in the skeletalδ13C between the fast growing tops of the coral and the slower growing sides

The origin of variations in the isotopic record of scleractinian corals: I. Oxygen

Previous investigations of the δ 18O of the skeletons of Florida specimens of the reef coral Montastraea annularis have failed to produce the full temperature range suggested by calibration studies of other corals. Explanations for this phenomenon include different relationships between temperature and the δ 18O of skeletons of Floridian corals, changing δ 18O of the water, physiological variables (“vital effects”), and an insufficient number of samples taken per year with consequent superposition of calcium carbonate precipitated at different times within an individual sample. In this study, we investigate all of these hypotheses, by measuring the δ 18O of corals grown in the field which were periodically stained with alizarin-red S and where the δ 18O of the water was measured and the temperature continuously recorded. We compare the effect of sampling the coral skeletons at different resolutions and the effect of sampling within different skeletal elements. Our study shows that discrete, high-resolution sampling of coral exotheca (fifty samples a year) is necessary to reproduce temperatures for this species in Florida waters. Coral skeletons sampled using lower resolution methods showed an artificial attenuation of the annual range in skeletal δ 18O, with similar δ 18O minima during the skeleton represented by the summer months, but larger differences in the winter δ 18O maxima. Replicate isotope transects from fast and slow growing areas and different regions of the corallite were also compared. The δ 18O of rapidly growing (8 mm/y) portions of the colony was 0.1 to 0.2‰ heavier than the slowest growing (1.1 mm/y) portions of the colony. This difference as well as the difference between the skeleton sampled at high and low resolutions appears to result in part from the attenuation of the δ 18O signal as a result of the reduced sampling rate in slower growing sections of the coral and is not solely a result of variable kinetic effects