Showing papers by "Jun Lu published in 1996"

Measurement of dijet angular distributions by the collider detector at fermilab

Abstract: We have used 106 pb^-1 of data collected in proton-antiproton collisions at sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular distributions in events with two jets in the final state. The angular distributions agree with next to leading order (NLO) predictions of Quantum Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at 95% confidence level (CL) a model of quark substructure in which only up and down quarks are composite and the contact interaction scale is Lambda_ud(+) < 1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6 TeV.

Measurement of correlated μ-b¯ jet cross sections in pp¯ collisions at s=1.8 TeV

Abstract: We report on measurements of differential $\mu - {\bar b}$ cross sections, where the muon is from a semi-leptonic $b$ decay and the ${\bar b}$ is identified using precision track reconstruction in jets. The semi-differential correlated cross sections, d$\sigma$/d$\Et^{{\bar b}}$, d$\sigma$/d$\pt^{{\bar b}}$, and d$\sigma$/d$\delta\phi(\mu - {\bar b})$ for $\pt^{\mu}>$~9 GeV/c, $|\eta^{\mu}| $~10 GeV, $|\eta^{{\bar b}}|<$~1.5, are presented and compared to next-to-leading order QCD calculations.

Measurement of σB(W→ev) and σB(Z0→e+e-) in pp̄ collisions at √s = 1.8 TeV

Abstract: We present a measurement of $\sigma \cdot B(W \to e u)$ and $\sigma \cdot B(Z^0 \to e^+e^-)$ in proton - antiproton collisions at $\sqrt{s} =1.8$ TeV using a significantly improved understanding of the integrated luminosity. The data represent an integrated luminosity of 19.7 pb$^{-1}$ from the 1992-1993 run with the Collider Detector at Fermilab (CDF). We find $\sigma \cdot B(W \to e u) = 2.49 \pm 0.12$~nb and $\sigma \cdot B(Z^0 \to e^+e^-) = 0.231 \pm 0.012$~nb.

Ratios of bottom meson branching fractions involving J/ psi mesons and determination of b quark fragmentation fractions.

Abstract: We report a measurement of the ratios of the decay rates of the ${B}^{+}$, ${B}^{0}$, and ${B}_{s}^{0}$ mesons into exclusive final states containing a $\frac{J}{\ensuremath{\psi}}$ meson. The final states were selected from 19.6 pb-1 of $p\overline{p}$ collisions recorded by the Collider Detector at Fermilab. These data are interpreted to determine the $b$ quark fragmentation fractions ${f}_{u}$, ${f}_{d}$, and ${f}_{s}$. We also determine the branching fractions for the decay modes ${B}^{+}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}{K}^{+}}$, ${B}^{+}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}{K}^{*}{(892)}^{+}}$, ${B}^{0}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}{K}^{0}}$, ${B}^{0}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}{K}^{*}{(892)}^{0}}$, and ${B}_{s}^{0}\ensuremath{\rightarrow}\frac{J}{\ensuremath{\psi}\ensuremath{\varphi}(1020)}$. We discuss the implications of these measurements to $B$ meson decay models.

Reconstruction of B0→J/ΨKS0 and Measurement of Ratios of Branching Ratios Involving B→J/ΨK* and B+→J/ΨK+

Abstract: We report on the reconstruction of the decay mode B{sup 0o} {yields} J/{psi}K{sup 0}{sub s} using 193 pb{sup -1} of data collected by the Collider Detector at Fermilab in p{bar p} collisions at sqrt[s] = 18 TeV A signal of 418{+-}69 events, with a signal-to-background ratio of 9:1, is observed Three additional decay modes B{sup +} {yields} J/{psi}K{sup +}, B{sup 0} {yields} J/{psi}K{sup *}(892){sup 0}, and B{sup +} {yields} J/{psi}K{sup *}(892){sup +} are reconstructed We measure three ratios of branching ratios, each one relative to the B{sup +} {yields} J/{psi}K{sup +} mode We also report the ratio of decay rates, {gamma}(B {yields} J/{psi}K{sup *})/{gamma}(B {yields} J/{psi}K), for the vector-vector relative to the vector-pseudoscalar modes, to be 132{+-}023(stat){+-}016(syst)

Search for charged Higgs boson decays of the top quark using hadronic τ decays

Abstract: We present the result of a search for charged Higgs boson decays of the top quark, produced in $p\overline{p}$ collisions at $\sqrt{s}=1.8$ TeV. When the charged Higgs boson is heavy and decays to a $\ensuremath{\tau}$ lepton, which subsequently decays hadronically, the resulting events have a unique signature: large missing transverse energy and the low-charged-multiplicity $\ensuremath{\tau}$. Data collected in 1992 and 1993 at the Collider Detector at Fermilab, corresponding to 18.7\ifmmode\pm\else\textpm\fi{}0.7 ${\mathrm{pb}}^{\ensuremath{-}1}$, exclude new regions of combined top quark and charged Higgs boson mass, in extensions to the standard model with two Higgs doublets.

Properties of Jets in W Boson Events from 1.8 TeV p¯p Collisions

Abstract: We present a study of events with Z bosons and hadronic jets produced in {bar p}p collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 Z{yields}e{sup +}e{sup -} decays from 106 pb{sup -1} of integrated luminosity collected using the CDF detector at the Fermilab Tevatron Collider. The Z+{ge}n jet cross sections and jet production properties have been measured for n = 1 to 4. The data are compared to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

Search for chargino-neutralino production in pp collisions at s=1.8 tev

Abstract: We have searched for chargino-neutralino production ({tilde {xi}}{sub 1}{sup {+-}}{tilde {xi}}{sub 2}{sup 0}) in 1.8 TeV p{bar p} collisions, followed by their leptonic decays {tilde {xi}}{sub 1}{sup {+-}}{yields}{tilde {xi}}{sub 1}{sup 0}{ell}{sup {+-}}{nu} and {tilde {xi}}{sub 2}{sup 0}{yields}{tilde {xi}}{sub 1}{sup 0}{ell}{sup +}{ell}{sup -}. These trilepton events are expected within a framework of the minimal supersymmetric standard model (MSSM). In a 19.1 pb{sup -1} data sample collected with a Collider Detector at Fermilab, no trilepton events were observed. Upper limits on {sigma}(p{bar p} {yields}{tilde {xi}}{sub 1}{sup {+-}}{tilde {xi}}{sub 2}{sup 0})BR({tilde {xi}}{sub 1}{sup {+-}}{tilde {xi}}{sub 2}{sup 0}{yields}3{ell}+X) were obtained for various MSSM parameter space regions, yielding new 95% confidence level lower limits for the neutralino ({tilde {xi}}{sub 2}{sup 0}) mass which extend as high as 49 GeV/c{sup 2}.

Search for flavor-changing neutral current B meson decays in pp̄ collisions √s = 1.8 Te V

Abstract: We report on a search for the flavor-changing neutral current decays B{sub d,s}{sup 0}{yields}{mu}{sup +}{mu}{sup -}, B{sup +}{yields}{mu}{sup +}{mu}{sup -}K{sup +}, and B{sup 0}{yields}{mu}{sup +}{mu}{sup -}K*{sup 0} using data from p{bar p} collisions at {radical}s= 1.8 TeV, collected with the Collider Detector at Fermilab during the 1992-1993 running period. We find no indication of such decays and we set the following 90% confidence level upper limits on branching ratios: B(B{sup 0}{yields}{mu}{sup +}{mu}{sup -})<1.6x10{sup -6}, B(B{sub s}{sup 0}{yields}{mu}{sup +}{mu}{sup -})<8.4 x 10{sup -6}, B(B{sup +}{yields}{mu}{sup +}{mu}{sup -}K{sup +})<1.0x10{sup -5}, and B(B{sup 0}{yields}{mu}{sup +}{mu}{sup -}K*{sup 0})<2.5x10{sup -5}.

Measurement of the branching fraction B(B+u→J/ψπ+) and Search for B+c→J/ψπ+

Abstract: We report on a measurement of the branching fraction of the Cabibbo-suppressed decay ${B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}$, where $J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. The data were collected by the Collider Detector at Fermilab during 1992--1995 and correspond to an integrated luminosity of $110{\mathrm{pb}}^{\ensuremath{-}1}$ in $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$. A signal of ${28}_{\ensuremath{-}9}^{+10}$ events is observed and we determine the ratio of branching fractions $B({B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+})/B({B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{+})$ to be $[{5.0}_{\ensuremath{-}1.7}^{+1.9}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{syst})]%$. Using the world average value for $B({B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{+})$, we calculate the branching fraction $B({B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+})$ to be $({5.0}_{\ensuremath{-}1.9}^{+2.1})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. We also search for the decay ${B}_{c}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}$ and report a $95%$ confidence level limit on $\ensuremath{\sigma}({B}_{c}^{+})B({B}_{c}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+})/\ensuremath{\sigma}({B}_{u}^{+})B({B}_{u}^{+}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{+})$ as a function of the ${B}_{c}^{+}$ lifetime.

Properties of Jets in W boson events form 1.8 TeV {ovr p}p collisions.

Abstract: We present a study of events with W bosons and hadronic jets produced in {ovr p}p collisions at a center of mass energy of 1.8 TeV. The data consist of 51 400 W{sup +-}{yields}e{sup +-}{nu} decay candidates from 108 pb{sup -1} of integrated luminosity collected using the CDF detector at the Fermilab Tevatron Collider. Cross sections and jet production properties have been measured for W+{>=}1 to {>=}4 jet events. The data are compared to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.

Presence of free radicals in pigment gallstone in vivo.

Abstract: OBJECTIVE To clarify whether free radical, which may play a role in pigment gallstone formation, is present in pigment gallstones in vivo. MATERIALS AND METHODS Free radical signal of gallstones from 18 patients was detected by electron paramagnetic resonance spectroscopy at 77K under anaerobic condition and in air (control). As soon as the anaerobic determination was finished, the fresh anaerobic sample was exposed to air and stored in a freezer at -20 degrees C. RESULTS Free radical signal (g = 2.0038) was detected in fresh anaerobic samples containing more than 2% bilirubin compound, and the signal intensity correlated linearly with the content of calcium bilirubinate (r = +0.95, P < 0.0005). During the storage at -20 degrees C and exposure to air, the signal intensity of each anaerobic sample and its control increased gradually, eventually reaching the same stable level. Fe(III) signal intensity was enhanced synchronously and related linearly with free radical signal (r = +0.99, P < 0.0005). CONCLUSIONS Free radical exists originally in pigment gallstones in vivo, and it may play an important role in pigment gallstone formation. The free radical signal carried by gallstones may be strengthened by the action of oxygen in air on bilirubin. The transition metal ions probably take part in the formation of bilirubin free radical.

On temporal versioning in object oriented databases.

Abstract: This paper describes the development of the data model TVM which contains a new concept, temporal versioning. This generalises the ideas of temporal databases and version management to object-oriented databases. TVM provides a new approach for data modelling and management; it allows the user to define a multi-dimensional temporal storage space and to model the evolution of objects within that space. It supports historical versions and alternative versions of objects at instance level and as well as schema level. as how these different solutions can be combined have not yet been tackled. Many applications require databases that support both temporal data and version management (such as design of engineering objects). Figure 1 shows a Car-Manufacturing Database. There are several types of lock which can be used in this car model. These locks are an alternatives of each other and valid at same time. The historical information of engine design is important, the updated data is need to be preserved. It is considered historical (temporal)

Measurement of the mass of the Bs0 meson.

Abstract: We measure the mass of the ${\mathit{B}}_{\mathit{s}}^{0}$ meson by reconstructing the decay chain ${\mathit{B}}_{\mathit{s}}^{0}$\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\varphi}, J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$, and \ensuremath{\varphi}\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{\ensuremath{-}}}$. The data are obtained from 19.3 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ of integrated luminosity of p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s=1.8 TeV using the Collider Detector at Fermilab. A sample of 80 000 inclusive J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$ events is used to study systematic biases in track reconstruction and to calibrate the momentum scale. We reconstruct the kinematically similar decays ${\mathit{B}}^{+}$\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathit{K}}^{+}$ and ${\mathit{B}}^{0}$\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathit{K}}^{\mathrm{*}0}$ to study the mass measurement technique used for the ${\mathit{B}}_{\mathit{s}}^{0}$ meson. Based on the observation of 32 \ifmmode\pm\else\textpm\fi{} 6 candidates, the mass of the ${\mathit{B}}_{\mathit{s}}^{0}$ meson is measured to be 5369.9 \ifmmode\pm\else\textpm\fi{} 2.3 \ifmmode\pm\else\textpm\fi{} 1.3 MeV/${\mathit{c}}^{2}$ and the mass difference between ${\mathit{B}}_{\mathit{s}}^{0}$ and the average mass of ${\mathit{B}}^{+}$ and ${\mathit{B}}^{0}$ is determined to be 89.7 \ifmmode\pm\else\textpm\fi{} 2.7 \ifmmode\pm\else\textpm\fi{} 1.2 MeV/${\mathit{c}}^{2}$. \textcopyright{} 1996 The American Physical Society.

Observation of ballistic transport in the upper subband of a two-dimensional electron system

Abstract: We report a specially designed transverse magnetic focusing experiment on a two-dimensional electron system confined to a square quantum well with two electric subbands occupied. The reflecting barrier of a usual magnetic focusing device is replaced by a surface-gate-induced, tunable potential barrier that allows us to selectively reflect and magnetically focus the upper subband electrons while the lower subband electrons pass over the barrier and are not focused. We observe the focusing of the upper subband electrons. The weakness of the focusing signal for the upper subband ballistic electrons suggests that they have a surprisingly short ballistic mean free path compared to the lower subband electrons.

The Events That Occur when Cisplatin Encounters Cells

Abstract: The chemical studies on the cellular response to platinum anticancer complexes are reviewed by treating the cell as a complex reacting system comprising several critical targets. In this multiple-target system, the contributions of non-DNA targets cannot be underestimated. The biological events observed in the response should be interpreted as the step-by-step results of a process in which the concert of related chemical reactions generates a sequence of chemical events. According to the multiple-target model the molecules in the plasma membrane, phospholipids and proteins, are the frontier targets. It is shown, on the basis of thermodynamic considerations, that the membrane proteins are attacked preferentially, while platinum binding to the phospholipids is relatively weak and reversible. Nevertheless, the weak and transient interaction with the phospholipids causes alterations in conformation which are transmitted and amplified further, resulting in changes in the structure and function of membranes, such as the permeability. The chemical events that occur in the course of platinum-phospholipid interactions include platinum binding, the subsequent conformational changes of the phospholipids and a change in the structure of the bilayer. In addition, the action of platinum complexes on the cytoskeleton is summarized in terms of a perturbation of the process of polymerization of skeletal protein. The sequence of chemical events, platinum binding to the monomeric protein and the induced conformational change and perturbations to the self-association of the monomer, is shown to be important in the cell damaging process. Platinum binding to actin was shown to be fatal to the cell by inducing cross-linking and aggregation and depolymerization and disorganization of the microfilaments. Various platinum complexes have been compared and several trends in their structure-activity are discussed. The other relevant events, apoptosis and drug resistance are also emphasized with the involvement of targets other than DNA.

Ballistic transport in the upper subband of a two-dimensional electron system

Abstract: We report the observation of ballistic transport of upper subband electrons in a two-dimensional electron system (2DES) confined to a square quantum well with two occupied electrical subbands. We have performed two types of experiments. In the first type, we use a specially designed transverse magnetic focusing device in which the usual reflecting barrier is replaced by a surface-gate-induced, tunable potential barrier to selectively reflect and magnetically focus the upper subband electrons. In the second type of experiment, we create a surface-gate-induced, periodic potential in a double-subband-occupied 2DES and measure the magnetoresistance along the modulation direction. Fourier analysis is used to separate the commensurability oscillations originating from ballistic electrons of different subbands.