Phys.Rev.D

We measure the relative rate of production of orbitally excited (L=1) states of B mesons (B**) by observing their decays into Bπ±. We reconstruct B mesons through semileptonic decay channels using data collected in pp¯ collisions at s=1.8TeV. The fraction of light B mesons that are produced as L=1B** states is measured to be 0.28±0.06(stat)±0.03(syst). We also measure the collective mass of the B** states, and quantify the result by quoting the (model-dependent) mass of the lowest B** state to be m(B1)=5.71±0.02GeV/c2.

Phys.Rev.Lett.

We have searched for direct production of scalar top quarks at the Collider Detector at Fermilab in 88 pb-1 of p anti-p collisions at s**(1/2) = 1.8 TeV. We assume the scalar top quark decays into either a bottom quark and a chargino or a bottom quark, a lepton, and a scalar neutrino. The event signature for both decay scenarios is a lepton, missing transverse energy, and at least two b-quark jets. For a chargino mass of 90 GeV/c2 and scalar neutrino masses of at least 40 GeV/c2, we find no evidence for scalar top production and present upper limits on the production cross section in both decay scenarios.

Eur.Phys.J.C

The$\tau$polarisation has been studied with the${\rm e^+e^-}\to \tau^+\tau^-$data collected by the DELPHI detector at LEP in

Phys.Lett.B

The branching ratio for the leptonic decay of charged B mesons ( B − →τ − ν ̄ τ ) has been measured using selected leptonic τ − →ℓ − ν τ ν ̄ ℓ and hadronic τ − → ν τ X decays in Z → b b ̄ decays recorded by DELPHI at LEP1 in 1992–1995. The result, BR ( B − →τ − ν ̄ τ )<1.1×10 −3 at the 90% confidence level, is consistent with standard model expectations and puts a constraint on the ratio tan β / M H ± <0.46 (GeV/ c 2 ) −1 in the framework of models with two Higgs doublets (type II Higgs doublet model). From the missing energy distribution in Z → b b ̄ decays without identified leptons, the b →τ ν ̄ τ X branching ratio has been measured in the hadronic channel τ → ν τ X′. The result, BR ( b →τ ν ̄ τ X )=(2.19±0.24 ( stat )±0.39 ( syst ))% , is consistent with the Standard Model prediction and with previous experimental measurements.

Phys.Lett.B

The study of the directional dependence of two-particle correlations in the hadronic decays of the Z 0 boson is performed using the data collected by the DELPHI experiment in the 1992–1995 running periods. The comparison between the transverse, R ⊥ , and longitudinal, R ∥ , correlation radii confirms the string model prediction that the transverse correlation length is smaller than the longitudinal one, with the measured values of R ⊥ =0.53±0.08 fm and R ∥ =0.85±0.08 fm , for selected Z 0 →q q ̄ events.

Eur. Phys. J. A

The mass spectrum is calculated for those dileptons which are produced in the early phase of a heavy ion collisions via the direct production NN -> (l^+)(l^-)X and via the Compton process GN -> (l^+)(l^-)X with prompt gluons radiated in preceding NN interactions. Both mechanisms produce a mass spectrum which decreases steeply with invariant mass of the l^+l^- pair and which is below the CERES data for Pb-Au collisions by about one order of magnitude.

Phys. Lett. B

In the context of a two-flavour approximation we reinterpret the published NOMAD limit on ν μ → ν τ oscillations in terms of ν e → ν τ oscillations. At 90% C.L. we obtain sin 2 2θ eτ < 5.2×10 −2 for large Δm 2 , while for sin 2 2 θ eτ =1 the confidence region includes Δm 2 <11 eV 2 / c 4 .

JETP Lett.

An algorithm is proposed for the determination of the asymptotics of a sum of a perturbation series from the given values of its coefficients in the strong-coupling limit. When applied to the \Phi^4 theory, the algorithm yields the \beta(g)\propto g^\alpha behavior with \alpha\approx 1 at large g for the Gell-Mann - Low function.

J. Exp. Theor. Phys.

High orders of perturbation theory can be calculated by the Lipatov method, whereby they are determined by saddle-point configurations (instantons) of the corresponding functional integrals. For most field theories, the Lipatov asymptotics has the functional form c a^N \Gamma(N+b) (N is the order of perturbation theory), and the relative corrections to it have a form of a series in powers of 1/N. It is shown that this series diverges factorially and its high-order coefficients can be calculated using a procedure similar to Lipatov's one. The K-th expansion coefficient has the form const(\ln(S1/S0))^{-K}\Gamma(K+(r1-r0)/2), where S0 and S1 are the values of the action for the first and the second instanton of the field theory under consideration, while r0 and r1 are the corresponding numbers of zero modes. The instantons satisfy the same equation as in the Lipatov method and are assumed to be renumbered in order of increasing of their action. This result has the universal character and is valid in any field theory for which the Lipatov asymptotic form is as specified above.

Phys. Rev. Lett.

We have reconstructed the radiative decays $\chi_{b}(1P) \to \Upsilon(1S) \gamma $ and $\chi_{b}(2P) \to \Upsilon(1S) \gamma $ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $\Upsilon(1S)$ mesons that originate from these decays. For $\Upsilon(1S)$ mesons with $p^{\Upsilon}_{T}>8.0$ GeV/$c$, the fractions that come from $\chi_{b}(1P)$ and $\chi_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))%$ and $(10.5\pm4.4(stat)\pm1.4(sys))%$, respectively. We have derived the fraction of directly produced $\Upsilon(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))%$.

Phys.Rev.Lett.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb$^{-1}$ of $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top quark decays to a charm quark and a neutralino, or scalar bottom quark decays to a bottom quark and a neutralino. The numbers of events that pass our selection for each process show no deviation from Standard Model expectations. We compare our results to next-to-leading order calculations for the scalar quark production cross sections to exclude regions in scalar quark-neutralino parameter space.

Eur. Phys. J. C

The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the Delphi detector at the Z resonance between 1992 and

Phys.Atom.Nucl.

The total and topological 4Hep cross sections as well as the cross sections of the separate 4Hep interaction channels and the differential cross sections of the elastic 4Hep scattering were measured using the 2m hydrogen bubble chamber exposed to a separated beam of alpha-particles from the ITEP synchrotron at 5 GeV/c (the kinetic energy of the initial protons in the nuclear rest frame was 620 MeV). The data obtained have been compared with the results of the previous experiments and with the theoretical predictions based on the Glauber-Sitenko multiple-scattering theory.

Phys. Lett. B

The longitudinal polarization of the Λ b baryon is measured at the LEP e + e − collider by DELPHI. It is determined from the charged lepton and neutrino energy spectra in 249±19 Λ b semileptonic decays reconstructed in ≈3.5 million hadronic Z 0 decays using Λ 0 -lepton correlations. The measured polarization is: P Λ b =−0.49 −0.30 +0.32 (stat.)±0.17(syst.)

Eur.Phys.J.A

The Pauli Exclusion Principle (PEP) was tested with the NEMO-2 detector. Limits at the 90% C.L. on the violation of PEP for p-shell nucleons in 12C were obtained. Specifically, transitions to the full

Phys. Lett. B

The total cross section of the reaction $pp\to ppK^+K^-$ has been determined for proton--proton reactions with $p_{beam}=3.67 GeV/c$. This represents the first cross section measurement of the $pp \to ppK^-K^+$ channel near threshold, and is equivalent to the inclusive $pp\to ppK^-X$ cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive $pp\to ppK^+X$ meson production at the same CM energy above the corresponding threshold. This large difference in the $K^+$ and $K^-$ meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.

AIP Conf.Proc.

ANKE is a second generation experimental facility at the internal beam of the accelerator COSY at the Forschungszentrum Jülich (Germany). It has recently (May 1998) been installed in the ring, commissioned and immediately after this been exploited for first experiments. Using circulating beams of protons with energies between 1.0 and 2.3 GeV, sub- and near threshold production of K + mesons in collisions with carbon-strip targets has been investigated. The detection system of ANKE used for the first measurements is capable of detecting positively charged ejectiles in the momentum range between about 100 and 600 MeV/c. In particular, it has been optimized for K + identification in the presence of an intense background of protons and pions. The final results of the experiments (cross sections and momentum spectra) will be used to obtain more detailed information on the subthreshold production mechanism.

Nucl. Phys. B Proc. Suppl.

We rewiew the present status of the Baikal Neutrino Project and present the results of a search for high energy neutrinos with the detector intermediate stage NT-96.

Phys.Rev.D

This paper reports an updated measurement of the Standard Model CP violation parameter $\sin2\beta$ using the CDF Detector at Fermilab. The entire Run I data sample of 110 pb$^{-1}$ of proton antiproton collisions at $\sqrt{s}=1.8 TeV$ is used to identify a signal sample of $\sim 400$ $B \to J/\psi K^0_S$ events, where $J/\psi \to \mu^+\mu^-$ and $K_S^0 \to \pi^+\pi^-$. The flavor of the neutral B meson is identified at the time of production by combining information from three tagging algorithms: a same-side tag, a jet-charge tag, and a soft-lepton tag. A maximum likelihood fitting method is used to determine $\sin2\beta = 0.79 {+0.41\atop-0.44}$(stat+syst). This value of $\sin 2 \beta$ is consistent with the Standard Model prediction, based upon existing measurements, of a large positive CP violating asymmetry in this decay mode.

Phys.Rev.Lett.

We have studied the production of B hadrons in 1.8-TeV p-pbar collisions. We present measurements of the fragmentation fractions, f_u, f_d, f_s and f_baryon, of produced b quarks that yield B^+, B^0, B^0_s and Lambda_b hadrons. Reconstruction of several electron-charm final states yields f_s/(f_u+f_d)=0.213+/-0.068 and f_baryon/(f_u+f_d)=0.118+/-0.042, assuming f_u=f_d. If all B hadrons produced in p-pbar collisions cascade to one of these four hadrons, we determine f_u=f_d=0.375+/-0.023, f_s=0.160+/-0.044 and f_baryon=0.090+/-0.029. If we do not assume f_u=f_d, we find f_d/f_u=0.84+/-0.16.

Phys. Rev. Lett.

We present the results of a search for pair production of a fourth-generation charge -1/3 quark (b') in sqrt(s)=1.8 TeV ppbar collisions using 88 pb^(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b' -> bZ and that the b' mass is greater than m_Z + m_b. We studied the decay mode b'b'bar -> ZZ b bbar where one Z0 decays into e^+e^- or mu^+ mu^- and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the cross section of ppbar -> b'b'bar times [BR (b' -> bZ)]^2 is established as a function of the b' mass. We exclude at 95% confidence level a b' quark with mass between 100 and 199 GeV/c^2 for BR(b' -> bZ) = 100%.

Phys.Rev.Lett.

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->l nu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a ttbar sample isolated in 106 +/- 4 inverse picobarns of data collected in ppbar collisions at sqrt(s)=1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V--A weak decay, we find that the fraction of W's with zero helicity in the top rest frame is F_0 = 0.91 +/- 0.37 (stat) +/- 0.13 (syst), consistent with the standard model prediction of F_0=0.70 for a top mass of 175 GeV/c**2.

Eur.Phys.J.C

A precise measurement of the strange quark forward-backward asymmetry used 3.2M multihadronic events around the Z$^0$peak collected by the DELPHI experiment from 1

Phys.Rev.Lett.

We report a measurement of the fraction of b quarks produced diffractively in p¯p collisions at s=1.8 TeV. Diffraction is identified by the absence of particles in a forward pseudorapidity region. From events with an electron of transverse momentum 9.5