Engineering topics
Corcoran, M.
Publications and source records attributed to Corcoran, M..
Measurement of angular correlations of jets at root s=1.96 TeV and determination of the strong coupling at high momentum transfers
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Measurement of the semileptonic charge asymmetry in B 0 meson mixing with the D0 detector
Not Available
Search for Zγ events with large missing transverse energy in pp̄ collisions at √s=1.96 TeV
We present the first search for new phenomena in Zγ final states with large missing transverse energy using data corresponding to an integrated luminosity of 6.2 fb⁻¹ collected with the D0 experiment in pp̄ collisions at √s=1.96 TeV. This signature is predicted in gauge-mediated supersymmetry-breaking models, where the lightest neutralino χ˜⁰₁ is the next-to-lightest supersymmetric particle and is produced in pairs, possibly through decay from heavier supersymmetric particles. The χ˜⁰₁ can decay either to a Z boson or a photon and an associated gravitino that escapes detection. We exclude this model at the 95% C.L. for supersymmetry-breaking scales of Λ<87 TeV.
Measurement of the top-quark mass in pp̄ collisions using events with two leptons
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Combined Search for the Standard Model Higgs Boson Decaying to bb̄ Using the D0 Run II Data Set
We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into bb̄ using the data sample collected with the D0 detector in pp̄ collisions at √s=1.96 TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV≤M H ≤150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120 GeV≤M H ≤145 GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.
Search for the standard model Higgs Boson in associated W H production in 9.7 fb – 1 of p p ¯ collisions with the D0 detector
Here, we present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a $b$-quark jet. The search is primarily sensitive to $WH\to\ell\nu b\bar{b}$ production and uses data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=1.96$ TeV. We observe agreement between data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2$\times\sigma_{\rm SM}$, where $\sigma_{\rm SM}$ is the standard model Higgs boson production cross section, while the expected limit is 4.7$\times\sigma_{\rm SM}$.
Search for Higgs boson production in oppositely charged dilepton and missing energy events in pp̄ collisions at √s=1.96 TeV
We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in H→WW decays. The events are selected from data corresponding to 8.6 fb⁻¹ of integrated luminosity in pp̄ collisions at √s=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.
Observation of a narrow mass state decaying into Υ(1S)+γ in pp̄ collisions at √s=1.96 TeV
Using data corresponding to an integrated luminosity of 1.3 fb⁻¹, we observe a narrow mass state decaying into Υ(1S)+γ, where the Υ(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551±0.014(stat)±0.017(syst) GeV/c², which is consistent with that of the state recently observed by the ATLAS Collaboration.
Search for WH associated production in pp̄ collisions at √s=1.96 TeV
This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L≈5.3 fb⁻¹ collected with the D0 detector at the Fermilab Tevatron pp̄ Collider. Events containing a W→lν candidate (with l corresponding to e or μ) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a b quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the WH production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson (M H ). The observed and expected 95% C.L. upper limits obtained for an assumed M H =115 GeV are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.
Measurement of the differential cross section dσ/dt in elastic pp̄ scattering at √[s]=1.96 TeV
Not Available
Combination of searches for anomalous top quark couplings with 5.4 fb(-1) of p(p)over-bar collisions
We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in t{bar t} events. We set upper limits on anomalous tWb coupling form factors using data collected with the D0 detector at the Tevatron p{bar p} collider corresponding to an integrated luminosity of 5.4 fb{sup -1}.
Search for Violation of Lorentz Invariance in Top Quark Pair Production and Decay
Not Available
Measurement of the WZ and ZZ production cross sections using leptonic final states in 8.6 fb⁻¹ of pp̄ collisions
We study the processes pp̄→WZ→l ± νl⁺l⁻ and pp̄→ZZ→l⁺l⁻νν¯, where l=e or μ. Using 8.6 fb⁻¹ of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the WZ production cross section to be 4.50 +0.63 –0.66 pb which is consistent with, but slightly larger than, the prediction of the standard model. The ZZ cross section is measured to be 1.64±0.46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ→l⁺l⁻l⁺l⁻ channel yields a ZZ cross section of 1.44 +0.35 –0.34 pb.
Interactions in Massive Colliding Wind Binaries
The most massive stars (M> 60 Solar Mass) play crucial roles in altering the chemical and thermodynamic properties of their host galaxies. Stellar mass is the fundamental stellar parameter that determines their ancillary properties and which ultimately determines the fate of these stars and their influence on their galactic environs. Unfortunately, stellar mass becomes observationally and theoretically less well constrained as it increases. Theory becomes uncertain mostly because very massive stars are prone to strong, variable mass loss which is difficult to model. Observational constraints are uncertain too. Massive stars are rare, and massive binary stars (needed for dynamical determination of mass) are rarer still: and of these systems only a fraction have suitably high orbital inclinations for direct photometric and spectroscopic radial-velocity analysis. Even in the small number of cases in which a high-inclination binary near the upper mass limit can be identified, rotational broadening and contamination of spectral line features from thick circumstellar material (either natal clouds or produced by strong stellar wind driven mass loss from one or both of he stellar components) biases the analysis. In the wilds of the upper HR diagram, we're often left with indirect and circumstantial means of determining mass, a rather unsatisfactory state of affairs.
The Spatially-resolved Interacting Winds of Eta Carinae: Implications on the Orbit Orientation
Medium-dispersion long slit spectra, recorded by HST/STIS (R=8000, Theta=0.l"), resolve the extended wind-wind interaction region of the massive binary, Eta Carinae. During the high state, extending for about five years of the 5.54-year binary period, lines of [N II], [Fe III], [S III], [Ar III] and [Ne III] extend outwards to 0.4" with a velocity range of -500 to +200 km/s. By comparison, lines of [Fe II] and [Ni II] extend to 0.7" with a velocity range of -500 to +500 km/s. During the high state, driven by the lesser wind of Eta Car B and photo-ionized by the FUV of Eta Car B, the high excitation lines originate in or near the outer ballistic portions of the wind-wind interaction region. The lower excitation lines ([Fe II] and [Ni II D originate from the boundary regions of the dominating wind of Eta Car A. As the binary system has an eccentricity exceeding 0.9, the two stars approach quite close across the periastron, estimated to be within 1 to 2 AU. As a result, Eta Car B moves into the primary wind structure, cutting off the FUV supporting the ionization of the high state lines. Forbidden emission lines of the doubly-ionized species disappear, He II 4686 drops along with the collapse of the X-ray flux. This behavior is understood through the 3-D models of A. Okazaki and of E. R. Parkin and Pittard. Discussion will address the orbit orientation relative to the geometry of the Homunculus, ejected by Eta Carinae in the 1840s.
Resolving the Massive Binary Wind Interaction Of Eta Carinae with HST/STIS
We have resolved the outer structures of the massive binary interacting wind of Eta Carinae using the HST/STIS. They extend as much as 0.7' (1600AU) and are highly distorted due to the very elliptical orbit of the binary system. Observations conducted from 1998.0 to 2004.3 show spatial and temporal variations consistent with a massive, low excitation wind, seen by spatially resolved, velocity-broadened [Fe II], and a high excitation extended wind interaction region, seen by[Fe III], in the shape of a distorted paraboloid. The highly excited [Fe III] structure is visible for 90% of the 5.5-year period, but disappears as periastron occurs along with the drop of X-Rays as seen by RXTE. Some components appear in [Fe II] emission across the months long minimum. We will discuss the apparent differences between the bowshock orientation derived from the RXTE light curve and these structures seen by HST/STIS. Monitoring the temporal variations with phase using high spatial resolution with appropriate spectral dispersions proves to be a valuable tool for understanding massive wind interactions.