Double Diffraction Dissociation at the Fermilab Tevatron Collider

We present results from a measurement of double diffraction dissociation in $\bar pp$ collisions at the Fermilab Tevatron collider. The production cross section for events with a central pseudorapidity gap of width $\Delta\eta^0>3$ (overlapping $\eta=0$) is found to be $4.43\pm 0.02{(stat)}{\pm 1.18}{(syst) mb}$ [$3.42\pm 0.01{(stat)}{\pm 1.09}{(syst) mb}$] at $\sqrt{s}=1800$ [630] GeV. Our results are compared with previous measurements and with predictions based on Regge theory and factorization.Comment: 10 pages, 4 figures, using RevTeX. Submitted to Physical Review Letter

Dichromatic dark matter

Both the robust INTEGRAL 511 keV gamma-ray line and the recent tentative hint of the 135 GeV gamma-ray line from Fermi-LAT have similar signal morphologies, and may be produced from the same dark matter annihilation. Motivated by this observation, we construct a dark matter model to explain both signals and to accommodate the two required annihilation cross sections that are different by more than six orders of magnitude. In our model, to generate the low-energy positrons for INTEGRAL, dark matter particles annihilate into a complex scalar that couples to photon via a charge-radius operator. The complex scalar contains an excited state decaying into the ground state plus an off-shell photon to generate a pair of positron and electron. Two charged particles with non-degenerate masses are necessary for generating this charge-radius operator. One charged particle is predicted to be long-lived and have a mass around 3.8 TeV to explain the dark matter thermal relic abundance from its late decay. The other charged particle is predicted to have a mass below 1 TeV given the ratio of the two signal cross sections. The 14 TeV LHC will concretely test the main parameter space of this lighter charged particle.University of Wisconsin--Madison (Start-up funds)SLAC National Accelerator Laboratory (US DOE contract DE-AC02-76SF00515)Aspen Center for Physics (NSF Grant No. 1066293)United States. National Aeronautics and Space Administration (Einstein Postdoctoral Fellowship grant number PF2-130102)Smithsonian Astrophysical Observatory (Chandra X-ray Center, NASA under contract NAS8-03060

Risk propensity in the foreign direct investment location decision of emerging multinationals

A distinguishing feature of emerging economy multinationals is their apparent tolerance for host country institutional risk. Employing behavioral decision theory and quasi-experimental data, we find that managers’ domestic experience satisfaction increases their relative risk propensity regarding controllable risk (legally protectable loss), but decreases their tendency to accept non-controllable risk (e.g., political instability). In contrast, firms’ potential slack reduces relative risk propensity regarding controllable risk, yet amplifies the tendency to take non-controllable risk. We suggest that these counterbalancing effects might help explain observation that risk-taking in FDI location decisions is influenced by firm experience and context. The study provides a new understanding of why firms exhibit heterogeneous responses to host country risks, and the varying effects of institutions

Methods for specifying the target difference in a randomised controlled trial : the Difference ELicitation in TriAls (DELTA) systematic review

Peer reviewedPublisher PD

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

The 'knowledge politics' of democratic peace theory

How do academic ideas influence US foreign policy, under what conditions and with what consequences? This article traces the rise, ‘securitisation’ and political consequences of democratic peace theory (DPT) in the United States by exploring the work of Doyle, Diamond and Fukuyama. Ideas influence US foreign policy under different circumstances, but are most likely to do either during and after crises when the policy environment permits ‘new thinking’, or when these ideas have been developed through state-connected elite knowledge networks, or when they are (or appear paradigmatically congenial to) foreign policymakers’ mindsets, or, finally, when they become institutionally-embedded. The appropriation of DPT by foreign policymakers has categorised the world into antagonistic blocs – democratic/non-democratic zones of peace/turmoil – as the corollary to a renewed American mission to make the world ‘safer’ through ‘democracy’ promotion. The roles of networked organic intellectuals – in universities and think tanks, for instance – were particularly important in elevating DPT from the academy to national security managers

Measurement of the Top Quark Mass with the Collider Detector at Fermilab

This report describes a measurement of the top quark mass in \ppbar collisions at a center of mass energy of 1.8 TeV. The data sample was collected with the CDF detector during the 1992--95 collider run at the Fermilab Tevatron, and corresponds to an integrated luminosity of 106 \pb. Candidate $t\bar{t}$ events in the ``lepton+jets'' decay channel provide our most precise measurement of the top quark mass. For each event a top mass is determined by using energy and momentum constraints on the production of the \ttbar pair and its subsequent decay. A likelihood fit to the distribution of reconstructed masses in the data sample gives a top mass in the lepton+jets channel of 176.1\pm 5.1 (stat.)\pm 5.3 (syst.) \gevcc. Combining this result with measurements from the ``all-hadronic'' and ``dilepton'' decay topologies yields a top mass of 176.1\pm 6.6 \gevcc.Comment: 158 pages, 41 figure

Search For Charged Higgs Decays of the Top Quark Using Hadronic Decays of the Tau Lepton

This Letter describes a direct search for charged Higgs boson production in proton-antiproton collisions at sqrt(s)=1.8 TeV recorded by the Collider Detector at Fermilab. Two-Higgs-doublet extensions to the standard model predict the existence of charged Higgs bosons. In such models, the branching fraction for top quarks B(t --> H b --> tau nu b) can be large. This search uses the hadronic decays of the tau lepton in this channel to significantly extend previous limits on charged Higgs production.Comment: 6pages, 4 figures, 1 table; LaTeX; submitted to PR

Limits on WWZWWZ and WWγWW\gamma couplings from WWWW and WZWZ production in pp‾p\overline{p} collisions at s=1.8\sqrt{s} = 1.8 TeV

Direct limits are set on $WWZ$ and $WW\gamma$ three-boson couplings in a search for $WW$ and $WZ$ production with high transverse momentum in $p\overline{p}$ collisions at $\sqrt{s} = 1.8$ TeV, using the Collider Detector at Fermilab. The results are in agreement with the SU(2) $\times$ U(1) model of electroweak interactions. Assuming Standard Model $WW\gamma$ coupling, the the limits are interpreted as direct evidence for a non-zero $WWZ$ coupling at subprocess energies near 500 GeV. Alternatively, assumiong identical $WWZ$ and $WW\gamma$ couplings, bounds $-0.11 < \kappa < 2.27$ and $-0.81 < \lambda < 0.84$ are obtained at $95\%$ CL for a form factor scale 1000 GeV.Comment: 16 pages, submitted to PRL, URL: http://www-cdf.fnal.gov/physics/pub95/cdf2951_vvprl.p

Measurement of the BB Meson Differential Cross Section, dσ/dpTd\sigma/dp_T, in ppˉp\bar{p} Collisions at s=1.8\sqrt{s} = 1.8 TeV

This paper presents the first direct measurement of the $B$ meson differential cross section, $d\sigma/dp_T$, in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV using a sample of $19.3 \pm 0.7$ pb$^{-1}$ accumulated by the Collider Detector at Fermilab (CDF). The cross section is measured in the central rapidity region $|y| 6.0$ GeV/$c$ by fully reconstructing the $B$ meson decays $B^{+}\to J/\psi K^{+}$ and $B^{0}\to J/\psi K^{*0}(892)$, where $J/\psi \to \mu^+\mu^-$ and $K^{*0} \to K^+ \pi^-$. A comparison is made to the theoretical QCD prediction calculated at next-to-leading order.Comment: 14 pages. Submitted to Phys. Rev. Lett. The postscript file is at http://www-cdf.fnal.gov/physics/pub95/cdf2893_bexcl_xsection.p