Showing papers by "Jie Zhang published in 2000"
TL;DR: In this article, a search for the Standard Model Higgs boson in the data sample collected with the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV, was performed.
157 citations
TL;DR: In this article, a search for charged Higgs bosons produced in pairs is performed with data collected at centre-of-mass energies ranging from 189 to 209 GeV by ALEPH at LEP, corresponding to a total luminosity of 629 invpb.
86 citations
TL;DR: In this paper, the cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented.
Abstract: The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no significant deviation from the Standard Model predictions. This enable constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale Lambda of eeff contact interactions are typically in the range from 2-10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV for large values of their Yukawa couplings.
62 citations
Hirosaki University1, Saitama University2, Tibet University3, Academia Sinica4, Southwest Jiaotong University5, Kanagawa University6, Utsunomiya University7, University of Tokyo8, Konan University9, Shibaura Institute of Technology10, Yunnan University11, Yokohama National University12, Shonan Institute of Technology13
TL;DR: In this paper, a high-density air shower array was used to search for γ-ray signals from the BL Lac object Mrk 501 during the period in 1997 from February through August.
Abstract: In 1997, the BL Lac object Mrk 501 entered a very active phase and was the brightest source in the sky at TeV energies, showing strong and frequent flaring. Using the data obtained with a high-density air shower array that has been operating successfully at Yangbajing in Tibet since 1996, we searched for γ-ray signals from this source during the period in 1997 from February through August. Our observation detected multi-TeV γ-ray signals at the 3.7 σ level during this period. The most rapid increase in the excess counts was observed between April 7 and June 16, and the statistical significance of the excess counts in this period was 4.7 σ. Among several observations of flaring TeV γ-rays from Mrk 501 in 1997, this is the only observation using a conventional air shower array. We present the energy spectrum of γ-rays, which will be worth comparing with those obtained by imaging atmospheric Cerenkov telescopes.
41 citations
TL;DR: The chiral symmetry relation and scaling of the overlap fermions are studied numerically on the quenched lattices at 3 couplings with about the same physical volume and the critical slowing down sets in abruptly at a very small quark mass close to those of the physical u and d quarks.
Abstract: The chiral symmetry relation and scaling of the overlap fermions are studied numerically on the quenched lattices at 3 couplings with about the same physical volume. We find that the generalized Gell-Mann-Oakes-Renner relation is satisfied to better than 1% down to the smallest quark mass at m(0)a = 0.006. We also obtain the quark mass from the PCAC relation and the pseudoscalar masses. The renormalization group invariant quark mass is shown to be fairly independent of scale. The pi and rho masses at a fixed m(pi)/m(rho) ratio indicate small O(a(2)) corrections. It is found that the critical slowing down sets in abruptly at a very small quark mass close to those of the physical u and d quarks.
41 citations
TL;DR: In this article, an experimental investigation of the structure of identified quark and gluon jets is presented; this allows for tests of QCD over a wide range of transverse momentum scales.
Abstract: An experimental investigation of the structure of identified quark and gluon jets is presented. Observables related to both the global and internal structure of jets are measured; this allows for tests of QCD over a wide range of transverse momentum scales. The observables include distributions of jet-shape variables, the mean and standard deviation of the subjet multiplicity distribution and the fragmentation function for charged particles. The data are compared with predictions of perturbative QCD as well as QCD-based Monte Carlo models. In certain kinematic regions the measurements are sensitive mainly to perturbatively calculable effects, allowing for a test of QCD. The comparisons are also extended into regions where nonperturbative effects become large, and in this way the transition from hard to soft QCD is investigated. It is found that by including leading and next-to-leading logarithmic contributions in the QCD predictions, the agreement with the data can be extended to lower transverse momentum scales, especially for gluon jets.
40 citations
TL;DR: In this article, the authors used the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays and selected 23 candidates with an estimated purity of 71%.
38 citations
TL;DR: In this article, the mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects, and the measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.
Abstract: Hadronic Z decay data taken with the ALEPH detector at LEP1 are used to measure the three-jet rate as well as moments of various event-shape variables. The ratios of the observables obtained from b-tagged events and from an inclusive sample are determined. The mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects. Taking the first moment of the $y_3$
distribution, which is the observable with the smallest hadronization corrections and systematic uncertainties, the result is
\[m_b(M_{\mathrm Z}) = \left[3.27 \pm 0.22 (\mathrm{stat}) \pm 0.22 (\mathrm{exp}) \pm 0.38 (\mathrm{had}) \pm 0.16 (\mathrm{theo})\right] \;\gevcc\quad. \] The measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.
30 citations
TL;DR: The Instituto de Fisica Teorica Universidade Estadual Paulista, Rua Pamplona 145, 01405-900, Sao Paulo, Brazil as discussed by the authors.
29 citations
TL;DR: In this paper, the ALEPH detector at LEP1 has been used to search for γγ production of the glueball candidates f0(1500) and fJ(1710) via their decay to π+π−.
28 citations
TL;DR: Two-particle correlations of Lambda Lambda and pairs have been studied in multihadronic Z decays recorded with the ALEPH detector at LEP in the years from 1992 to 1995 as discussed by the authors.
Journal Article•
TL;DR: The replicative form of the Periplaneta fuliginosa densovirus (PfDNV) genome was cloned and its complete nucleotide sequence was determined and the organization of PfDNV genome was compared to those of other parvoviruses.
Abstract: The replicative form (RF) of the Periplaneta fuliginosa densovirus (PfDNV) genome was cloned and its complete nucleotide sequence was determined. The PfDNV genome is 5454 nucleotides (nt) in length with distal 201-nt long inverted terminal repeats (ITRs). The first 122 nt at the 5'-end and the terminal 122 nt at the 3'-end of both strands are palindromes with identical sequences, of which each can fold into a typical U-shaped hairpin structure. The coding regions of PfDNV genome are evenly distributed in the 5'-halves of both strands. PfDNV genome contains seven major open reading frames (ORFs), four of which on the plus DNA strand may encode non-structural (NS) proteins, while the others on the minus DNA strand may encode structural proteins. Two potential functional promoters (P3 and P97) were found within the ITRs on both strands. The ORF2 polypeptide contains a highly conserved NTP-binding domain of NS proteins of parvoviruses. The ORF5 polypeptide has significant homology to the conserved PGY region of coat proteins of parvoviruses. The ORF6 polypeptide has distinct homology to the structural polypeptides of insect parvoviruses. The organization of PfDNV genome was compared to those of other parvoviruses.
TL;DR: In this paper, the decay of hadronic Z decays recorded with the ALEPH detector from 1991 to 1995 is observed, based on tagging the final state with two φ mesons in the same hemisphere.
TL;DR: In this article, the authors considered optimal taxation in an endogenous growth model where private education investments are imperfectly observable and showed that consumption taxation is better than labor income taxation for public provision of goods unless educational investment is completely unobservable.
TL;DR: In this paper, the authors measured the decay branching fraction of the W boson into hadrons at lower center-of-mass energies and showed that B(W → hadrons) = 66.97 ± 0.65(stat.) ± 0.32(syst.)%, allowing a determination of the CKM matrix element |Vcs| = 0.951 ± 0.,
TL;DR: In this article, a scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime.
Abstract: Searches for topologies characteristic of Gauge Mediated SUSY Breaking models (GMSB) are performed by analysing 173.6 pb^-1 of data collected at Ecm = 188.6~GeV with the ALEPH detector.These topologies include acoplanar photons, non-pointing single photon, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and four leptons plus missing energy final states.No evidence for these new phenomena is observed and limits on production cross sections and sparticle masses are derived. A scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime.
Journal Article•
TL;DR: The results of this study suggest that there is a close relationship between c-myc gene and mdr1 gene, which may be involved in regulating the expression of mDR1.
Abstract: Objective To investigate the relationship between c-myc expression and mdr1 regulation in multidrug resistance (MDR) tumor cell line KBv200. Methods A DNA sequence encoding the ribozyme gene was incorporated into a eukaryotic expression vector (pH beta Apr-1 neo) and transfected into the cell line KB, which is resistant to vincristine and expresses the MDR phenotype. The changes of c-myc protein, P-glycoprotein (P-gp) and c-myc mRNA in the KB cell line were assessed before and after treatment with anti-mdr1-ribozyme using immunohisto-chemistry, flow cytometry and semi-quantitative RT-PCR methods. Results The results demonstrate elevated levels of c-myc mRNA and c-myc protein as well as P-gp in KBv200 cells which are resistant to vincristine (VCR), compared to these of the KB cell which is not resistant to VCR. The expression of c-myc protein, P-gp and c-myc mRNA in the multidrug resistant cell, KBv200, displayed higher than that in the sensitive cell, KB. However, after reversing the multidrug resistance phenotype by anti-mdr1-ribozyme, the level of c-myc protein, P-gp and c-myc mRNA expression showed significant down-regulation in KBv/5 mR3, without difference in KB/5 mR3 and KB. Conclusion The results of our study suggest that there is a close relationship between c-myc gene and mdr1 gene. c-myc may be involved in regulating the expression of mdr1.
TL;DR: In this paper, the ALEPH detector at LEP collected at center-of-mass energies from 189 GeV to 202 GeV, corresponding to an integrated luminosity of 411 pb-1, are analysed in a search for the scalar top in the decay channels'stop -> c/u neutralino' for small mass differences between the stop and the lightest neutralino.
27 Jul 2000
TL;DR: The BABAR detector at SLAC PEP-II has been recording data at energies on and around the Upsilon(4S) resonance since May 1999 as mentioned in this paper, and the performance presently achieved by the experiment in the areas of tracking, vertexing, calorimetry and particle identification is reviewed.
Abstract: The BABAR detector, situated at the SLAC PEP-II asymmetric e^+e^- collider, has been recording data at energies on and around the Upsilon(4S) resonance since May 1999. In this paper, we briefly describe the PEP-II B Factory and the BABAR detector. The performance presently achieved by the experiment in the areas of tracking, vertexing, calorimetry and particle identification is reviewed. Analysis concepts that are used in the various papers submitted to this conference are also discussed.
TL;DR: In this paper, a search for gamma-gamma decays of a Higgs boson is performed in the data sample collected at LEP with the ALEPH detector between 1991 and 1999.
27 Jul 2000
TL;DR: In this article, exclusive decays of B mesons into final states containing charmonium using data collected with the BABAR detector at the PEP-II storage rings were reported.
Abstract: We report on exclusive decays of B mesons into final states containing charmonium using data collected with the BABAR detector at the PEP-II storage rings. The charmonium states considered here are J/psi, psi(2S), and chi_C1. Branching fractions for several exclusive final states, a measurement of the decay amplitudes for the B0 --> J/psi K* decay, and measurements of the B0 and B+ masses are presented. All of the results we present here are preliminary.
01 Jan 2000
TL;DR: In this article, single top production via flavour changing neutral currents in the reactions e + e − → t c / u is searched for in approximately 411 −pb −1 of data collected by ALEPH at center-of-mass energies in the range between 189 and 202 −GeV.
27 Jul 2000
TL;DR: In this paper, the flight length difference between the two B mesons which are pair-produced in the Y(4S) decay was determined from the two mesons' trajectories.
Abstract: Data collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC are used to study the lifetimes of the B^0 and B^+ mesons. The data sample consists of 7.4 fb-1 collected near the Y(4S) resonance. B^0 and B^+ mesons are fully reconstructed in several exclusive hadronic decay modes to charm and charmonium final states. The B lifetimes are determined from the flight length difference between the two B mesons which are pair-produced in the Y(4S) decay. The preliminary measurements of the lifetimes are tau_B0 = 1.506+/-0.052(stat)+/-0.029(syst) ps, tau_B+ = 1.602+/-0.049(stat)+/-0.035(syst) ps, and of their ratio is tau_B+/tau_B0 = 1.065+/-0.044(stat)+/-0.021(syst)
Posted Content•
TL;DR: The concept of allocative and productive efficiency as discussed by the authors is a static concept in the sense that they relate to welfare at a point in time, i.e., they reflect the outcome at a single point of time of resource allocation and production decisions.
Abstract: Allocative and productive efficiency are static concepts in the sense that they relate to welfare at a point in time. Allocative and productive efficiency reflect the outcome at a single point in time of resource allocation and production decisions.
27 Jul 2000
TL;DR: In this article, preliminary results of a search for charmless two-body B decays to charged pions and kaons using data collected by the BABAR detector at the Stanford Linear Accelerator Center's PEP-II storage ring were presented.
Abstract: We present preliminary results of a search for charmless two-body B decays to charged pions and kaons using data collected by the BABAR detector at the Stanford Linear Accelerator Center's PEP-II storage ring. In a sample of 8.8 million produced B-anti-B pairs we measure the branching fractions B(B^0 --> pi^+pi^-) = (9.3^{+2.6}_{-2.3}^{+1.2}_{-1.4}) x 10^{-6} and B(B^0 --> K^+\pi^-) = (12.5^{+3.0}_{-2.6}^{+1.3}_{-1.7}) x 10^{-6}, where the first uncertainty is statistical and the second is systematic. For the decay B^0 --> K^+K^- we find no significant signal and set an upper limit of B(B^0 --> K^+K^-) 6.6 x 10^{-6} at the 90% confidence level.
27 Jul 2000
TL;DR: In this article, a preliminary study of time dependence of B^0-anti-B^0 oscillations using dilepton events is presented, where the flavor of the B meson is determined by the charge sign of the lepton and the time evolution of the oscillations is studied by reconstructing the time difference between the decays of B mesons produced by the Y(4S) decay.
Abstract: A preliminary study of time dependence of B^0-anti-B^0 oscillations using dilepton events is presented. The flavor of the B meson is determined by the charge sign of the lepton. To separate signal leptons from cascade and fake leptons we have used a method which combines several discriminating variables in a neural network. The time evolution of the oscillations is studied by reconstructing the time difference between the decays of the B mesons produced by the Y(4S) decay. With an integrated luminosity of 7.7 fb-1 collected on resonance by BABAR at the PEP-II asymmetric B Factory, we measure the difference in mass of the neutral B eigenstates, Delta_mB0 to be (0.507+/-0.015+/-0.022) x 10^{12} hbar-s^{-1}.
27 Jul 2000
TL;DR: In this article, preliminary results of a search for charmless two-body B decays to charged pions and kaons using data collected by the BABAR detector at the Stanford Linear Accelerator Center's PEP-II storage ring were presented.
Abstract: We present preliminary results of a search for charmless two-body B decays to charged pions and kaons using data collected by the BABAR detector at the Stanford Linear Accelerator Center's PEP-II storage ring. In a sample of 8.8 million produced B-anti-B pairs we measure the branching fractions B(B^0 --> pi^+pi^-) = (9.3^{+2.6}_{-2.3}^{+1.2}_{-1.4}) x 10^{-6} and B(B^0 --> K^+\pi^-) = (12.5^{+3.0}_{-2.6}^{+1.3}_{-1.7}) x 10^{-6}, where the first uncertainty is statistical and the second is systematic. For the decay B^0 --> K^+K^- we find no significant signal and set an upper limit of B(B^0 --> K^+K^-) 6.6 x 10^{-6} at the 90% confidence level.
TL;DR: The expression of TSP-1, CD44H and CD44V6 is significantly related to histopathological types and might be a prognostic indicator in lung adenocarcinoma.
Abstract: Objective To analyze the expression of CD44H, C D4 4V6 and TSP 1 in human lung cancer tissues and their prognostic significance. WTHZ M ethods A total of 112 lung cancer samples were examined for CD44H, CD44 V6 and TSP 1 expression by immunohistochemical staining. Moreover, 25 cases out of them were detected for TSP 1 by RT PCR assay simultaneously. Resul ts Stronger expression of TSP 1 was demonstrated in adenocarcinomas (7 4.36％) as compared with squamous cell carcinomas (47.17％， WTBX P WTBZ ＝0 .03) and small cell lung cancer (35.71％, WTBX P WTBZ ＝0.02). All of small cell lung cancer had significantly low expression of CD44H and CD44V6. Adenocar cinomas (61.54％) showed stronger CD44H membranous expression than squamous cell carcinomas did (50.94％， WTBX P WTBZ ＝ 0.036 ). Whereas, squamous cell carcinomas (50.94％) showed stronger CD44V6 membranous expression than ad enocarcinomas did (17.95％, WTBX P WTBZ ＝0.003). Kaplan Meier survival s tati stical analysis for 100 cases with complete follow up data indicated that there was no significant relationship among TSP 1, CD44H, CD44V6 expr ession and overall survival rate. However, after stratifying by histopathologica l types, the overall survival rate of patients with low expression of TSP 1 was significantly higher than that of moderate／high expression groups in adenocarc inomas (Log Rank＝0.0163). Immunohistochemical and RT PCR technique were utiliz ed in 25 out of 112 cases simultaneously. The accordance rate of the two methods was 84％, and no significant difference was found between them. WTHZ Conclusion The expression of TSP 1, CD44H and CD44V6 is sign ificantly related to histopathological types. TSP 1 expression might be a progn ostic indicator in lung adenocarcinoma. TSP 1 can be detected reliably in forma lin fixed, paraffin embedded tissues by immunohistochemical method.
Journal Article•
TL;DR: Although loss of caspase3 expression may contribute to hepato-carcinogenesis, its expression may not be related to cell apoptosis in HCC.
Abstract: Objective To investigate the relationship between caspase3 expression and apoptosis in hepatocellular carcinoma (HCC) Methods In situ hybridization was employed to determine caspase3 expression, and in situ end labeling was used to detect apoptotic cells in HCC Results Twenty one of 39 (538%) cases of HCC were found to express caspase3 transcripts, while 462% of HCC failed to express it Adjacent non cancerous liver tissues showed more caspase3 positiveity (875%, 7/8) as compared with HCC ( P 005) The expression of caspase3 was correlated with HCC differentiation, as 722% (13/18) of moderately to well differentiated HCC showed positive caspase3 transcripts, while only 381% of poorly differentiated HCC was caspase3 positive ( P 005) No relationship was found between caspase3 and tumor size or grade or metastasis, although 625% (5/8) of HCC with metastasis was caspase3 positive but it did not differ significantly from that without metastasis ( P 005) Expression of caspase3 alone did not affect the apoptosis index (AI) of HCC AI was 71‰ in caspase3 positive tumors ( n =21), as compared to 66‰ ( n =18) in caspase3 negative cases ( P 005) Conclusion Although loss of caspase3 expression may contribute to hepato carcinogenesis, its expression may not be related to cell apoptosis in HCC