18 research outputs found

    Debris Disks: Probing Planet Formation

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    Debris disks are the dust disks found around ~20% of nearby main sequence stars in far-IR surveys. They can be considered as descendants of protoplanetary disks or components of planetary systems, providing valuable information on circumstellar disk evolution and the outcome of planet formation. The debris disk population can be explained by the steady collisional erosion of planetesimal belts; population models constrain where (10-100au) and in what quantity (>1Mearth) planetesimals (>10km in size) typically form in protoplanetary disks. Gas is now seen long into the debris disk phase. Some of this is secondary implying planetesimals have a Solar System comet-like composition, but some systems may retain primordial gas. Ongoing planet formation processes are invoked for some debris disks, such as the continued growth of dwarf planets in an unstirred disk, or the growth of terrestrial planets through giant impacts. Planets imprint structure on debris disks in many ways; images of gaps, clumps, warps, eccentricities and other disk asymmetries, are readily explained by planets at >>5au. Hot dust in the region planets are commonly found (<5au) is seen for a growing number of stars. This dust usually originates in an outer belt (e.g., from exocomets), although an asteroid belt or recent collision is sometimes inferred.Comment: Invited review, accepted for publication in the 'Handbook of Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018

    Strange Particle Production in pp Collisions at sqrt(s) = 0.9 and 7 TeV

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    Search for same-sign top-quark pair production at root s=7 TeV and limits on flavour changing neutral currents in the top sector

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    An inclusive search for same-sign top-quark pair production in pp collisions at root s = 7 TeV is performed using a data sample recorded with the CMS detector in 2010, corresponding to an integrated luminosity of 35 pb(-1). This analysis is motivated by recent studies of p (p) over bar -> t (t) over bar reporting mass-dependent forward-backward asymmetries larger than expected from the standard model. These asymmetries could be due to Flavor Changing Neutral Currents (FCNC) in the top sector induced by t -channel exchange of a massive neutral vector boson (Z'). Models with such a Z' also predict enhancement of same-sign top-pair production in pp or pp collisions. Limits are set as a function of the Z' mass and its couplings to u and t quarks. These limits disfavour the FCNC interpretation of the Tevatron results

    Search for three-jet resonances in pp collisions at √s=7 TeV

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    This is a Pre-Print version of the Article - Copyright @ 2011 APSA model-independent search for three-jet hadronic resonance production in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 inverse picobarns. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed. The number of expected standard model background events is found to be in good agreement with the observed events. Limits are set on a model describing the production of R-parity-violating supersymmetric gluino pairs, and gluino masses in the range of 200 to 280 GeV/c^2 are excluded at a 95% confidence level for the first time.This work is supported by the FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF andWCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

    Measurement of the ZZ production cross section and search for anomalous couplings in 2l2l' final states in pp collisions at sqrt(s)=7 TeV

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    Submitted to the Journal of High Energy Physics ; see paper for full list of authorsA measurement is presented of the ZZ production cross section in the ZZ to 2l 2l' decay mode with l = e, mu and l' = e, mu, tau in proton-proton collisions at sqrt(s) = 7 TeV with the CMS experiment at the LHC. Results are based on data corresponding to an integrated luminosity of 5.0 inverse femtobarns. The measured cross section sigma(pp to ZZ) = 6.24 [+0.86/-0.80] (stat.) [+0.41/-0.32] (syst.) +/- 0.14 (lumi.) pb is consistent with the standard model predictions. The following limits on ZZZ and ZZ gamma anomalous trilinear gauge couplings are set at 95% confidence level: -0.011 f[4;Z] < 0.012, -0.012 < f[5;Z] < 0.012, -0.013 < f[4;gamma] < 0.015, and -0.014 < f[5,gamma] < 0.014

    Legitimacy and the capitalist corporation: cross-cutting perspectives on ownership and control

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    see paper for full list of authors Submitted to the Journal of High Energy PhysicsA measurement of inclusive Z to tau^+ tau^- production in pp collisions is presented, in the final states mu+hadrons, e+hadrons, e+mu, and mu+mu. The data sample corresponds to an integrated luminosity of 36 inverse picobarns collected with the CMS detector at the LHC. The measured cross section is sigma(pp to Z) B(Z to tau^+ tau^-) = 1.00 +/- 0.05 (stat.) +/- 0.08 (syst.) +/-0.04 (lumi.) nb, which is in good agreement with the next-to-next-to-leading order QCD prediction and with previous measurements in the Z to e^+e^- and mu^+ mu^- channels. The reconstruction efficiency for hadronic tau decays is determined with a precision of 7%

    Problems in measuring the cash recovery rate and measurement error in estimates of the firm IRR

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    This paper considers the impact on estimates of the IRR derived from the cash recovery rate approach to the estimation of economic performance of an inability to observe the conceptually defined CRR from accounting data. In particular, it considers a typical proxy used in empirical applications of the CRR approach and asks the question — under what circumstances will this proxy fail to measure the true CRR? Two circumstances are identified. First, the empirical CRR will not measure the true CRR when advertising and research expenditures exist which should be treated as part of the composite investment (and, hence, as investment expenditures) but are expensed in the accounting records -referred to as the capitalize/expense case. Second, the empirical CRR will not measure the true CRR when the composite investment is made up of projects with different lives — referred to as the retirement case. For these two cases, relationships are developed between the proxy and the true CRR. From these relationships the impact of errors in measuring the CRR on estimates of the IRR are deduced. Analytically, it is demonstrated that, in the capitalize/expense case, the inability to measure the CRR produces measurement error in the IRR estimate that is monotonically and negatively related to the rate of investment growth. Further, as the proportion of expensed investment expenditures increases, measurement error increases if the investment growth rate is less than the IRR and decreases if the investment growth rate is greater than the IRR. In the retirement case, it is identified analytically that measurement error also will be monotonically and negatively related to the investment growth rate. This is the case even though the analyst is able to specify the basic relationship between investment outflows and subsequent cash inflows (the inability to spec ify this basic relationship is a problem considered in many papers on the CRR approach). Numerical examples suggest that these effects are not insignificant in size a priori.

    Measurements of inclusive W and Z cross sections in pp collisions at √s=7 TeV

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    Measurements of inclusive W and Z boson production cross sections in pp collisions at root s = 7 TeV are presented, based on 2 : 9 pb(-1) of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are combined to give sigma(pp -&gt; WX) x B (W -&gt; lv) = 9.95 +/- 0.07 (stat.) +/- 0.28 (syst.) +/- 1.09 (lumi.) nb and sigma(pp -&gt; ZX) x B (Z -&gt; l(+)l(-)) = 0.931 +/- 0.026 (stat.) +/- 0.023 (syst.) +/- 0.102 (lumi.) nb, where l stands for either e or mu. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recent parton distribution functions, are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty of less than 4%, are also reported
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