A measurement of the inclusive production of π0 mesons in hadronic Z decays is presented and compared to Monte Carlo model predictions. The analysis is based on approximately 2 million hadronic events recorded with the ALEPH detector at LEP at a centre-of-mass energy of ⊡s = 91.2 GeV. Neutral pions are reconstructed using photons measured in the electromagnetic calorimeter and photons from conversion pairs. The inclusive π0 momentum spectrum is measured in the range 0.025 < xp = p/pbeam < 1. In this range the number of π0 per hadronic Z is found to be 4.80 ± 0.07(stat) ± 0.31(sys). The differential inclusive π0 cross section is also measured as a function of transverse momentum with respect to the event plane (pTin and pTout).
PI0 multiplicity and cross sections for events with two converted photons.
PI0 multiplicity and cross sections for events with only one converted photon. Final data point for full x range uses jetset 7.4 monte carlo extrapolation prediction.
PI0 cross sections as a function of the transverse momentum PTOUT relative to the plane defined by the sphericity tensor.
Two samples of exclusive semileptonic decays, 579 B 0 → D ∗+ ℓ − ν ℓ events and 261 B 0 → D + ℓ − ν ℓ events, are selected from approximately 3.9 million hadronic Z decays collected by the ALEPH detector at LEP. From the reconstructed differential decay rate of each sample, the product of the hadronic form factor F (ω) at zero recoil of the D (∗)+ meson and the CKM matrix element | V cb | are measured to be F D ∗+ (1)|V cb | = (31.9 ± 1.8 stat ± 1.9 syst ) × 10 −3 , F D + (1)| V cb | = (27.8 ± 6.8 stat ± 6.5 syst ) × 10 −3 . The ratio of the form factors F D + (1) and F D ∗+ (1) is measured to be F D + (1) F D ∗+ (1) = 0.87 ± 0.22 stat ± 0.21 syst . A value of | V cb | is extracted from the two samples, using theoretical constraints on the slope and curvature of the hadronic form factors and their normalization at zero recoil, with the result | V cb | = (34.4 ± 1.6 stat ± 2.3 syst ± 1.4 th ) × 10 −3 . The branching fractions are measured from the two integrated spectra to be Br ( B 0 → D ∗+ ℓ − ν ℓ ) = (5.53 ± 0.26 stat ±0.52 syst ) %, Br ( B 0 → D ∗+ ℓ − ν ℓ ) = (2.35 ± 0.20 stat ± 0.44 syst ) %.
The formfactors are evaluated at zero recoil of D meson. Two different methods are used (see text for details). VCB is the KCM matrix element. The formfactor fitted to dependence: FF(OM) = FF(1)*(1-CONST*(OM-1)).
VCB is the KCM matrix element.
VCB is the KCM matrix element.
The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
Corrected F2P measurements averaged over all energies. Data are the statistically weighted averages given at the centre of each bin.
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The cross section limits are set using two methods. The first (C=COUNT) is a simple counting experiment, and the second (C=SHAPE) use the shape of the dij et mass spectrum input to a likelihood fit.
The reaction $\gamma p \rightarrow \omega p$ $(\omega \rightarrow \pi~+\pi~-\pi~0$ and $\pi~0\rightarrow\gamma\gamma)$ has been studied in $ep$ interactions using the \mbox{ZEUS} detector at photon-proton centre-of-mass energies between $70$ and $90\uni{GeV}$ and $|t| < 0.6\uni{GeV}~2$, where $t$ is the squared four momentum transferred at the proton vertex. The elastic \ome photoproduction cross section has been measured to be $\sigma_{\gamma p\rightarrow \omega p} = 1.21\pm 0.12\pm 0.23 \mu\mbox{b}$. The differential cross section $d\sigma_{\gamma p\rightarrow \omega p} /d|t|$ has an exponential shape $\mbox{e}~{-b |t|}$ with a slope $b = 10.0\pm 1.2\pm 1.3\uni{GeV}~{-2}$. The angular distributions of the decay pions are consistent with {\it s}-channel helicity conservation. When compared to low energy data, the features of $\omega$ photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the $\rho~0$ and $\phi$ photoproduction cross sections at HERA show a similar behaviour.
Total Elastic Cross Section.
No description provided.
SLOPE OF DSIG/DT distribution.
The differential cross section $d\sigma/dt$ for elastic $\rho~0$ photoproduction, $\gamma p \rightarrow \rho~0 p (\rho~0 \rightarrow \pi~+ \pi~-)$, has been measured in $ep$ interactions at HERA. The squared four-momentum exchanged at the proton vertex, $t$, has been determined directly by measuring the momentum of the scattered proton using the ZEUS Leading Proton Spectrometer (LPS), a large scale system of silicon micro-strip detectors operating close to the HERA proton beam. The LPS allows the measurement of the momentum of high energy protons scattered at small angles with accuracies of 0.4% for the longitudinal momentum and 5 MeV for the transverse momentum. Photoproduction of $\rho~0$ mesons has been investigated in the interval $0.073< |t| <0.40 GeV~2$, for photon virtualities $Q~2<1 GeV~2$ and photon-proton centre-of-mass energies $W$ between 50 and 100 GeV. In the measured range, the $t$ distribution exhibits an exponential shape with a slope parameter $b = 9.8 \pm 0.8 (stat.) \pm 1.1 (syst.) GeV~{-2}$. The use of the LPS eliminates the contamination from events with diffractive dissociation of the proton into low mass states.
SLOPE OF THE DSIG/DT distribution.
Total cross section integrated over t region.
Additional cross section, SIG, not given in the paper.
We have searched for a heavy neutral gauge boson, Z ′, using the decay channel Z ′ → ee . The data were collected with the DØ detector at the Fermilab Tevatron during the 1992–1993 p p collider run at s =1.8 TeV from an integrated luminosity of 15±1 pb −1 . Limits are set on the cross section times brancing ratio for the process p p → Z′ → ee as a function of the Z ′ mass. We exclude the existence of a Z ′ of mass less than 490 GeV/c 2 , assuming a Z ′ with the same coupling strengths to quarks and leptons as the standard model Z boson.
No description provided.
We present measurements of the structure function \Ft\ in $e~+p$ scattering at HERA in the range $3.5\;\Gevsq < \qsd < 5000\;\Gevsq$. A new reconstruction method has allowed a significant improvement in the resolution of the kinematic variables and an extension of the kinematic region covered by the experiment. At $ \qsd < 35 \;\Gevsq$ the range in $x$ now spans $6.3\cdot 10~{-5} < x < 0.08$ providing overlap with measurements from fixed target experiments. At values of $Q~2$ above 1000 GeV$~2$ the $x$ range extends to 0.5. Systematic errors below 5\perc\ have been achieved for most of the kinematic region. The structure function rises as \x\ decreases; the rise becomes more pronounced as \qsd\ increases. The behaviour of the structure function data is well described by next-to-leading order perturbative QCD as implemented in the DGLAP evolution equations.
No description provided.
No description provided.
No description provided.
The 132 pbt - 1 of data collected by ALEPH from 1991 to 1994 have been used to analyze η and ω production in τ decays. The following branching fractions have been measured: \(B\left( {{\tau ^ - } \to {\nu _\tau }\omega {h^ - }} \right) = \left( {1.91 \pm 0.07 \pm 0.06} \right) \times {10^{ - 2}},\)\(B\left( {{\tau ^ - } \to {\nu _\tau }\omega {h^ - }{\pi ^0}} \right) = \left( {4.3 \pm 0.6 \pm 0.5} \right) \times {10^{ - 3}},\)\(B\left( {{\tau ^ - } \to {\nu _\tau }\eta {K^ - }} \right) = \left( {2.9_{ - 1.2}^{ + 1.3} \pm 0.7} \right) \times {10^{ - 4}},\)\(B\left( {{\tau ^ - } \to {\nu _\tau }\eta {h^ - }{\pi ^0}} \right) = \left( {1.8 \pm 0.4 \pm 0.2} \right) \times {10^{ - 3}}\) and the 95% C.L. limit B(τ− → ντηπt -) < 6.2 × 10t - 4 has been obtained. The ωπt- and ηπt -π0 rates and dynamics are found in agreement with the predictions made from e+e∼ - annihilation data with the help of isospin invariance (CVC).
$\pi^+\pi^-\pi^0$ mass distribution (two entries per event) in the $\pi^{\pm}\pi^+\pi^-\pi^0$ final state for the one-photon sample. The bin size has been chosen to display the detailed shape of the $\omega$ peak. The non-resonant contribution is represented by a simple polynomial. Non-$\tau$ background has been subtracted. The error has been set to zero if it is smaller than the point size.
$\pi^+\pi^-\pi^0$ mass distributions (two entries per event) in the $\pi^{\pm}\pi^+\pi^-\pi^0$ final state for the two-photon sample. The bin size has been chosen to display the detailed shape of the $\omega$ peak. The non-resonant contribution is represented by a simple polynomial. Non-$\tau$ background has been subtracted. The error has been set to zero if it is smaller than the point size.
Background-subtracted $\omega\pi$ mass spectrum for the data presented here, plotted as black dots. The error has been set to zero if it is smaller than the point size.
We present results from a search for anomalous WW and WZ production in ppbar collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum spectrum of the W boson yields direct limits on the CP-conserving anomalous WWgamma and WWZ coupling parameters of -0.9 < delta kappa < 1.1 (with lambda = 0) and -0.6 < lambda < 0.7 (with delta kappa = 0) at the 95% confidence level, for a form factor scale Lambda = 1.5 TeV, assuming that the WWgamma and WWZ coupling parameters are equal.
CONST(NAME=SCALE) is the model parameter, used in the modification of the couplings as follows: g = g0/(1 + M(gamma Z)**2/CONT(NAME=SCALE)**2)**n.
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