ARGUS Collaboration Research Articles

Study of B oscillations at the DØ Experiment

Bd mixing was observed in 1987 by the ARGUS Collaboration [1], and gave first indication that the top quark was heavy which was discovered in 1995 at Tevatron [2,3], 8 years later. Following the observation of mixing, precise measurements of the Bd mixing parameter χd came from ARGUS [4] and CLEO [5] collaborations in 1992 and 1993 respectively. The main motivation for performing the BB mixing measurement lies in the determination of the CKM matrix element Vtd, that provides one of the constraints on the unitarity triangle. Vtd is accessible experimentally through the box diagrams in Fig. 1, by measuring the mass difference ∆md in Bd mixing. The relation between ∆md and Vtd can be seen in Eq. 1.

Decaysηc→γγ andηb→γγ: A test for potential models

We use a simple perturbation theory argument and measurements of charmonium leptonic widths $\Gamma (\psi_{NS} \rightarrow e^+e^-)$ to estimate the ratio \mbox{$R_\circ \equiv {\vert \Psi _{\eta_{c1S}}(0) \vert}^2 /{\vert\Psi_{\psi_{1 S}}(0)\vert}^2$} in the general context of non- relativistic potential models. We obtain $R_\circ = 1.4 \pm 0.1$. We then apply well known potential model formulas, which include lowest order QCD corrections, to find $\Gamma (\eta_c \rightarrow \gamma \gamma )/\Gamma (\psi_{1S} \rightarrow e^+e^-) \approx 2.2\pm 0.2$. The central value for $\Gamma (\psi_{1S} \rightarrow e^+ e^-)$in the 1992 Particle Data Tables then leads to a (non relativistic) prediction $\Gamma (\eta_c \rightarrow \gamma \gamma )\approx 11.8\pm 0.8 $ keV. This prediction is in good agreement with a recent measurement by the ARGUS collaboration, is consistent with a recent measurement by the L3 collaboration but is significantly higher than several earlier measurements and than previous theoretical estimates, which usually assume $R_\circ =1$. The correction to $R_\circ =1$ is estimated to be smaller but nonnegligible for the $b\bar b$ system. Using the current central measurement for $\Gamma (\Upsilon_{1S}\rightarrow e^+e^-)$ we find $\Gamma (\eta_b\rightarrow \gamma \gamma )\approx 0.58\pm 0.03$ keV. A rough estimate of relativistic corrections reduces the expected two photon rates to about 8.8 keV and 0.52 keV for the $\eta_c$ and $\eta_b$ mesons respectively. Such corrections

New results on charmed baryons from ARGUS

In the following, new results on charmed-baryon decays are presented by the ARGUS Collaboration. The experimental data have been recorded with the ARGUS detector operating at the e+ e− storage ring DORIS II at DESY, Hamburg. In these data, the excited charmed baryon Λc* + decaying into Λc+π+π- is observed for the first time. The results of a study of the decay\(\Lambda _c^ + \to p\bar K^0 \pi ^ + \pi ^ - \) are described. In addition, the observation of semi-leptonic decays of the Ξc0 and Ωc0 baryons are presented.

Bd0-B-bard0 mixing and the prediction of the top-quark mass in an independent particle potential model.

Considering ${B}_{d}^{0}\ensuremath{-}{\overline{B}}_{d}^{0}$ mixing in a potential model of independent quarks by taking the effective interaction Hamiltonian of the standard Salam-Weinberg-Glashow model and subsequently diagonalizing the corresponding mass matrix with respect to ${B}_{d}^{0}$ and ${\overline{B}}_{d}^{0}$ states, we obtain an expression for the mass difference $\ensuremath{\Delta}{M}_{{B}_{d}^{0}}$ in terms of the $t$-quark mass ${m}_{t}$. Using the recent observation of the mixing parameter ${x}_{d}=0.72\ifmmode\pm\else\textpm\fi{}0.15$ by the ARGUS Collaboration, we predict the lower bound on the top-quark mass as ${m}_{t}\ensuremath{\ge}149$ GeV. Further, a consideration of experimental mass difference $\ensuremath{\Delta}{M}_{{B}_{d}^{0}}=(4.0\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ GeV also leads to ${m}_{t}={167}_{\ensuremath{-}17}^{+16}$ GeV which is in agreement with the recent experimental bound as well as other theoretical predictions. However, such a prediction of ${m}_{t}$ that utilizes the experimental value of the CKM matrix element $|{V}_{\mathrm{td}}|$ may not appear convincing in view of the large uncertainties in the measurement of $|{V}_{\mathrm{td}}|$ so far reported. Therefore using the range of ${m}_{t}$ values within its bounds predicted from other independent works, we make a reasonable estimation of $|{V}_{\mathrm{td}}|$.

Effects of an extra Z' in the heavy-quark sector

In the light of the recent experimental result of the ARGUS Collaboration at DESY on \(B^0 \bar B^0 \) mixing, we examine its implication on the mass of the extra Z'-boson in theSpL (6)×UY (1) extension of the standard electroweak theory by considering the contributions of the tree level diagrams mediated by this extra Z'-boson. It is found that for the calculated bound onmZ', large values ofxs can be explained. In addition, it is found that the tree level contributions to ΔmD for the \(D^0 \bar D^0 \) system is at least an order of magnitude higher than the standard-model box diagram contributions.

Recent ARGUS results on τ/charm physics

The recent experimental results on τ and charm decays obtained by the ARGUS collaboration are presented in this talk. The results include new measurements of many exclusive decay modes of the τ lepton and of the inclusive three prong decay mode. They confirm the current world averages and stress the τ decay problem. A study of the hadronic τ decays into π − π 0 ν τ and π − π − π + ν τ performed. We searched in 29 different channels for neutrinoless τ d ecays. No evidence was found for these decays. The decay D + → K ∗+ K *0 , which is observed for the first time, is shown together with th e decay of the D s + meson into the same final state. These decays represent one of the few known decays of D mesons into two vector mesons. Furthermore a measurement of the semileptonic Λ c + decay is shown.

Pion parameters and four quark condensates from τ-decay data

A modified finite energy sum rules procedure is presented and applied for the phenomenological analysis of the difference of vector and axial-vector two-point current correlators. In the chiral limit π→evy decay axial formfactorFA, electro-magnetic difference of pion masses and the four quark condensates of dimensions six and eight are determined with improved accuracy, using the data on τ→v+nπ decays obtained by ARGUS collaboration. Our values forFA and Δmem are close to the measured ones, whileC6 exceeds 2.5–3 times the value given by the vaccum saturation hypothesis.

Exclusive hadronic decays of B mesons

The recent experimental results on exclusive hadronic decays of B mesons obtained by the ARGUS collaboration are presented in the talk. The results include exclusive hadronic decays involving a b → c transition, namely B decays with a D, D ∗ plus several pions and B decays to J/ψ or ψ′ mesons plus Kaons have been studied. The measurements of branching ratios for two-body B decays involving a J/ψ or ψ′ meson are of wide interest in the light of proposals for the study of CP violation in future experiments. The branching ratios are compared with the predictions of the model of Bauer, Stech and Wirbel and with a model of A.V. Dobrovolskaya. Using the cleanest decay channels, the masses and mass difference of the charged and neutral B meson are obtained. This mass difference is then compared with the mass splitting in other isospinmultipletts and with theoretical models.

The ARGUS microvertex drift chamber

The ARGUS collaboration is currently building a new microvertex drift chamber (μVDC) as an upgrade of their detector. The μVDC is optimized for B-meson physics at DORIS energies. Important design features are minimal multiple scattering for low-momentum particles and three-dimensional reconstruction of decay vertices with equal resolutions in r- φ and r- z. Vertex resolutions of 15–25 μm are expected. Prototypes of the μVDC have been tested with different gas mixtures at various pressures. Spatial resolutions as small as 20 μm were obtained using CO 2/propane at 4 bar and DME at 1 bar. New readout electronics have been developed for the μVDC aiming at low thresholds for the TDC measurements. Employing a novel idea for noise and cross-talk suppression, which is based on a discrimination against short pulses, very low threshold settings are possible.

PHYSICS OF TOP AND CP VIOLATION IN B DECAYS IN THE LIGHT OF THE ARGUS MEASUREMENTS

Implications of the significant [Formula: see text] mixing, observed by the ARGUS collaboration, on our present understanding of nature are discussed. Our emphasis is on the consequences of the standard model with a heavy top quark. We discuss also the future prospects of the observation of CP violation in B decays.

B meson decays and Kobayashi-Maskawa matrix

We compute Γ(B +→p p π +) and Γ(B 0→p p π +π −) by a dynamical model where one of the final pions are produced by Δ resonance decay. We also analyze the end-point behaviour of the electron spectrum in the decay→evX, by a calculated B meson wave function and partonic widths as given by QCD. By using recent data from the ARGUS Collaboration we obtain | V bc |=(4.8±0.4)×10 −2 and | V bu / V bc |=0.10±0.02.

Charmed baryon isodoublet mass splitting in quantum chromodynamics revitalized

We calculate the isodoublet mass splitting of charmed baryons in the quark model in QCD, which includes the relativistic correction and the explicit use of running QCD coupling constants with flavors. The model was applied and tested in the past for the calculations of isodoublet mass splittings of several hadrons. Our theoretical result ( Δm th( Σ c ++− Σ c 0)≅1.5±0.2 MeV) is in agteement with the recent experimental result ( Δm ex( Σ c ++− Σ c 0)=1.2±0.7±0.3 MeV) by the ARGUS Collaboration at the DORIS II storage ring.

Loop-induced charmless B decays and B-B-bar mixing.

We calculate the rate of the inclusive loop-induced process $b\ensuremath{\rightarrow}d+\ensuremath{\cdots}$ for three and four families using the constraint of $B\ensuremath{-}\overline{B}$ mixing on the quark masses and mixings. We find that the level of background which this process provides to the tree-level $b\ensuremath{\rightarrow}u+\ensuremath{\cdots}$ decay may reach 10% if $|\frac{{V}_{\mathrm{ub}}}{{V}_{\mathrm{cb}}}|$ and may grow to about 40% if $|\frac{{V}_{\mathrm{ub}}}{{V}_{\mathrm{cb}}}|=0.07$. The branching ratio of $b\ensuremath{\rightarrow}d+\ensuremath{\cdots}$ may reach its highest level of 0.5% if $|\frac{{V}_{\mathrm{ub}}}{{V}_{\mathrm{cb}}}|=0.2 \mathrm{and} 0.1%$ if ${V}_{\mathrm{ub}}=0$. In the latter case $b\ensuremath{\rightarrow}d+\ensuremath{\cdots}$ cannot account by itself for the charmless baryonic modes observed recently by the ARGUS collaboration.

Observation of Charmless B Decays

Annals of the New York Academy of SciencesVolume 535, Issue 1 p. 292-302 Observation of Charmless B Decays DAVID B. MacFARLANE, DAVID B. MacFARLANE ARGUS Collaborationa McGill University Montreal, Quebec, Canada H3A 2T8Search for more papers by this author DAVID B. MacFARLANE, DAVID B. MacFARLANE ARGUS Collaborationa McGill University Montreal, Quebec, Canada H3A 2T8Search for more papers by this author First published: July 1988 https://doi.org/10.1111/j.1749-6632.1988.tb51517.x See the appendix for a listing of the current members of the ARGUS collaboration. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume535, Issue1International Symposium on Production and Decay of Heavy FlavorsJuly 1988Pages 292-302 RelatedInformation

An Improved Upper Limit of the vT Mass from the Decay, τ‐π‐π‐π‐π+π+vτ

Annals of the New York Academy of SciencesVolume 535, Issue 1 p. 535-539 An Improved Upper Limit of the vT Mass from the Decay, τ-π-π-π-π+π+vτ BERNHARD SPAAN, BERNHARD SPAAN ARGUS Collaboration Institut für Physik Universität Dortmund Dortmund, Federal Republic of Germany Supported by the German Bundesministerium für Forschung und Technologie under Contract No. 054DO5 1P.Search for more papers by this author BERNHARD SPAAN, BERNHARD SPAAN ARGUS Collaboration Institut für Physik Universität Dortmund Dortmund, Federal Republic of Germany Supported by the German Bundesministerium für Forschung und Technologie under Contract No. 054DO5 1P.Search for more papers by this author First published: July 1988 https://doi.org/10.1111/j.1749-6632.1988.tb51545.x AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume535, Issue1International Symposium on Production and Decay of Heavy FlavorsJuly 1988Pages 535-539 RelatedInformation

Implications of large Bd0-B-bard0 mixing.

Implications of the large ${B}_{d}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $_{d}^{0}$ mixing measured by the ARGUS Collaboration are examined. Possible large top-quark mass is estimated. In addition, large CP-nonconservation effects in the two-body nonleptonic decays of ${B}_{d}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $_{d}^{0}$ and ${B}_{s}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $_{s}^{0}$ are recalculated. The results show that we still need \ensuremath{\sim}${10}^{6}$ ${B}_{d}$,${\mathit{s}}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $_{d}$,${\mathit{s}}^{0}$ pairs for testing these CP-nonconservation effects in the ${B}_{d}$,${\mathit{s}}^{0}$-B\ifmmode\bar\else\textasciimacron\fi{} $_{d}$,${\mathit{s}}^{0}$ system.