Search For Heavy Pointlike Dirac Monopoles

We have searched for central production of a pair of photons with high transverse energies in $p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV using $70 pb^{-1}$ of data collected with the D\O detector at the Fermilab Tevatron in 1994--1996. If they exist, virtual heavy pointlike Dirac monopoles could rescatter pairs of nearly real photons into this final state via a box diagram. We observe no excess of events above background, and set lower 95% C.L. limits of $610, 870, or 1580 GeV/c^2$ on the mass of a spin 0, 1/2, or 1 Dirac monopole.Comment: 12 pages, 4 figure

Search for High Mass Photon Pairs in p-pbar --> gamma-gamma-jet-jet Events at sqrt(s)=1.8 TeV

A search has been carried out for events in the channel p-barp --> gamma gamma jet jet. Such a signature can characterize the production of a non-standard Higgs boson together with a W or Z boson. We refer to this non-standard Higgs, having standard model couplings to vector bosons but no coupling to fermions, as a "bosonic Higgs." With the requirement of two high transverse energy photons and two jets, the diphoton mass (m(gamma gamma)) distribution is consistent with expected background. A 90(95)% C.L. upper limit on the cross section as a function of mass is calculated, ranging from 0.60(0.80) pb for m(gamma gamma) = 65 GeV/c^2 to 0.26(0.34) pb for m(gamma gamma) = 150 GeV/c^2, corresponding to a 95% C.L. lower limit on the mass of a bosonic Higgs of 78.5 GeV/c^2.Comment: 9 pages, 3 figures. Replacement has new H->gamma gamma branching ratios and corresponding new mass limit

Ratio of the Isolated Photon Cross Sections at \sqrt{s} = 630 and 1800 GeV

The inclusive cross section for production of isolated photons has been measured in \pbarp collisions at $\sqrt{s} = 630$ GeV with the \D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy ($E_T$) range from 7-49 GeV and have pseudorapidity $|\eta| < 2.5$. This measurement is combined with to previous \D0 result at $\sqrt{s} = 1800$ GeV to form a ratio of the cross sections. Comparison of next-to-leading order QCD with the measured cross section at 630 GeV and ratio of cross sections show satisfactory agreement in most of the $E_T$ range.Comment: 7 pages. Published in Phys. Rev. Lett. 87, 251805, (2001

Limits on WWZ and WW\gamma couplings from p\bar{p}\to e\nu jj X events at \sqrt{s} = 1.8 TeV

We present limits on anomalous WWZ and WW-gamma couplings from a search for WW and WZ production in p-bar p collisions at sqrt(s)=1.8 TeV. We use p-bar p -> e-nu jjX events recorded with the D0 detector at the Fermilab Tevatron Collider during the 1992-1995 run. The data sample corresponds to an integrated luminosity of 96.0+-5.1 pb^(-1). Assuming identical WWZ and WW-gamma coupling parameters, the 95% CL limits on the CP-conserving couplings are -0.33<lambda<0.36 (Delta-kappa=0) and -0.43<Delta-kappa<0.59 (lambda=0), for a form factor scale Lambda = 2.0 TeV. Limits based on other assumptions are also presented.Comment: 11 pages, 2 figures, 2 table

The Dijet Mass Spectrum and a Search for Quark Compositeness in bar{p}p Collisions at sqrt{s} = 1.8 TeV

Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| < 1.0). The order alpha_s^3 QCD predictions are in good agreement with the data and we rule out models of quark compositeness with a contact interaction scale < 2.4 TeV at the 95% confidence level.Comment: 11 pages, 4 figures, 2 tables, submitted to Phys. Rev. Let

Zgamma Production in pbarp Collisions at sqrt(s)=1.8 TeV and Limits on Anomalous ZZgamma and Zgammagamma Couplings

We present a study of Z +gamma + X production in p-bar p collisions at sqrt{S}=1.8 TeV from 97 (87) pb^{-1} of data collected in the eegamma (mumugamma) decay channel with the D0 detector at Fermilab. The event yield and kinematic characteristics are consistent with the Standard Model predictions. We obtain limits on anomalous ZZgamma and Zgammagamma couplings for form factor scales Lambda = 500 GeV and Lambda = 750 GeV. Combining this analysis with our previous results yields 95% CL limits |h{Z}_{30}| < 0.36, |h{Z}_{40}| < 0.05, |h{gamma}_{30}| < 0.37, and |h{gamma}_{40}| < 0.05 for a form factor scale Lambda=750 GeV.Comment: 17 Pages including 2 Figures. Submitted to PR

A Measurement of the W Boson Mass

We report a measurement of the W boson mass based on an integrated luminosity of 82 pb$^{-1}$ from \ppbar collisions at $\sqrt{s}=1.8$ TeV recorded in 1994--1995 by the \Dzero detector at the Fermilab Tevatron. We identify W bosons by their decays to $e\nu$ and extract the mass by fitting the transverse mass spectrum from 28,323 W boson candidates. A sample of 3,563 dielectron events, mostly due to Z to ee decays, constrains models of W boson production and the detector. We measure \mw=80.44\pm0.10(stat)\pm0.07(syst)~GeV. By combining this measurement with our result from the 1992--1993 data set, we obtain \mw=80.43\pm0.11 GeV.Comment: 11 pages, 5 figure

Measurement of the W boson mass using electrons at large rapidities

We report a measurement of the W boson mass based on an integrated luminosity of 82/pb from p-pbar collisions at sqrt(s) = 1.8 TeV recorded in 1994-1995 by the D0 detector at the Fermilab Tevatron. We identify W bosons by their decays to e-nu, where the electron is detected in the forward calorimeters. We extract the mass by fitting the transverse mass and the electron and neutrino transverse momentum spectra of 11,089 W boson candidates. We measure Mw = 80.691 +- 0.227 GeV. By combining this measurement with our previously published central calorimeter results from data taken in 1992-1993 and 1994-1995, we obtain Mw = 80.482 +- 0.091 GeV

Search for New Physics Using Quaero: A General Interface to - D0 Event Data

We describe Quaero, a method that i) enables the automatic optimization of searches for physics beyond the standard model, and ii) provides a mechanism for making high energy collider data generally available. We apply Quaero to searches for standard model WW, ZZ, and ttbar production, and to searches for these objects produced through a new heavy resonance. Through this interface, we make three data sets collected by the D0 experiment at sqrt(s)=1.8 TeV publicly available

Origin and development of oligoadenylate synthetase immune system

Abstract Background Oligoadenylate synthetases (OASs) are widely distributed in Metazoa including sponges, fish, reptiles, birds and mammals and show large variation, with one to twelve members in any given species. Upon double-stranded RNA (dsRNA) binding, avian and mammalian OASs generate the second messenger 2'-5'-linked oligoadenylate (2-5A), which activates ribonuclease L (RNaseL) and blocks viral replication. However, how Metazoa shape their OAS repertoires to keep evolutionary balance to virus infection is largely unknown. We performed comprehensive phylogenetic and functional analyses of OAS genes from evolutionarily lower to higher Metazoa to demonstrate how the OAS repertoires have developed anti-viral activity and diversified their functions. Results Ancient Metazoa harbor OAS genes, but lack both upstream and downstream genes of the OAS-related pathways, indicating that ancient OASs are not interferon-induced genes involved in the innate immune system. Compared to OASs of ancient Metazoa (i.e. sponge), the corresponding ones of higher Metazoa present an increasing number of basic residues on the OAS/dsRNA interaction interface. Such an increase of basic residues might improve their binding affinity to dsRNA. Moreover, mutations of functional residues in the active pocket might lead to the fact that higher Metazoan OASs lose the ability to produce 3'-5'-linked oligoadenylate (3-5A) and turn into specific 2-5A synthetases. In addition, we found that multiple rounds of gene duplication and domain coupling events occurred in the OAS family and mutations at functionally critical sites were observed in most new OAS members. Conclusions We propose a model for the expansion of OAS members and provide comprehensive evidence of subsequent neo-functionalization and sub-functionalization. Our observations lay the foundation for interrogating the evolutionary transition of ancient OAS genes to host defense genes and provide important information for exploring the unknown function of the OAS gene family