1,369 research outputs found
Measurement of Spin Correlations in tt Systems in the muon+jets Channel using a Matrix Element Method with the CMS Detector at the LHC
Get PDFIn this work, the consistency of the spin correlation strength in top quark pair events with the Standard Model (SM) prediction is tested in the muon+jets final state. The events are obtained from pp collisions at a centre-of-mass energy of sqrt(s) = 8 TeV, corresponding to an integrated luminosity of 19.7 fb^(-1). Using a Matrix Element Method, event likelihoods are calculated under two different top quark pair hypotheses: the SM hypothesis and a hypothesis which predicts zero spin correlation. Using the event likelihoods, a variable sensitive to the spin correlation strength is constructed. In a hypothesis testing procedure, the data are found to favour the SM hypothesis. Using a template fit method, the fraction of events that show SM spin correlations is measured to be f = 0.72 +/- 0.08 (stat) +0.15 -0.13 (syst), representing the most precise measurement of this quantity in the lepton+jets channel to date
Top-Quark Properties at the LHC
No full textA review of recent measurements of top-quark properties is presented. Inclusive and differential top-quark pair charge asymmetry measurements using the full Run I dataset are found to be in agreement with the standard model (SM) predictions. Results of spin correlation in top-quark pairs are presented and interpreted in terms of the SM predicted values and new physics models. Limits are set on flavour-changing neutral currents (FCNC), in particular with a Higgs boson in the final state
Measurements of Spin Correlations in CMS
No full textWe present an overview of the measurements of spin correlations in the CMS Collaboration. We present two analyses both in the dilepton channel using proton-proton collisions at TeV based on an integrated luminosity of 5.0 fb. The spin correlations and polarization are measured using angular asymmetries. The results are consistent with unpolarized top quarks and Standard Model spin correlation. The second analysis sets a limit on the real part of the top-quark chromo-magnetic dipole moment of at confidence level through the measured azimuthal angle difference between the two charged leptons from production.We present an overview of the measurements of spin correlations in the CMS Collaboration. We present two analyses both in the dilepton channel using proton-proton collisions at TeV based on an integrated luminosity of 5.0 fb. The spin correlations and polarization are measured using angular asymmetries. The results are consistent with unpolarized top quarks and Standard Model spin correlation. The second analysis sets a limit on the real part of the top-quark chromo-magnetic dipole moment of at confidence level through the measured azimuthal angle difference between the two charged leptons from production
Measurements of top-quark properties at the LHC
No full textMeasurements of several top-quark properties are presented, obtained from the ATLAS and CMS data collected in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV. The results include measurements of the top pair charge asymmetry, the top quark polarization in pair production and single top production, the W helicity in top decays. Results of spin correlation in topquark pairs are presented and interpreted in terms of the SM predicted values. The results are compared with predictions from the standard model as well as new physics models. The cross section of ttbar events produced in association with a W, Z boson or a photon is also presented
Fertilizer Response and Profitability in Rwanda: A Synthesis of Findings from MINAGRI Studies Conducted by The Food Security Research Project (FSRP) and The FAO Soil Fertility Initiative
Get PDFREPUBLIC OF RWANDA, MINISTRY OF AGRICULTURE, ANIMAL RESOURCES, AND FORESTRYfood security, food policy, Rwanda, fertilizer, Agribusiness, Crop Production/Industries, Q18,
Protocol 14 and new Strasbourg procedures : Towards greater efficiency ? And at what price?
No full textThis article critically examines the various measures recently adopted by the Committee of Ministers of the Council of Europe and aimed at guaranteeing the continued effectiveness of the European Court of Human Rights in the context of its steadily expanding workload. The author argues that, while reforms were needed, some of the measures adopted are open to criticism for addressing the wrong problems and for undermining the fundamental right of individual petition
Top-Quark Properties at the LHC
No full textA review of recent measurements of top-quark properties is presented. Inclusive and differential top-quark pair charge asymmetry measurements using the full Run I dataset are found to be in agreement with the standard model (SM) predictions. Results of spin correlation in top-quark pairs are presented and interpreted in terms of the SM predicted values and new physics models. Limits are set on flavour-changing neutral currents (FCNC), in particular with a Higgs boson in the final state
Re-reengineering the dream: agility as competitive adaptability
Get PDFOrganizational adaptation and transformative change management in technology-based organizations is explored in the context of collaborative alliances. A Re-reengineering approach is outlined in which a new Competitive Adaptability Five-Influences Analysis approach under conditions of collaborative alliance, is described as an alternative to Porter’s Five-Forces Competitive Rivalry Analysis model. Whilst continuous change in technology and the associated effects of technology shock (Dedola & Neri, 2006; Christiano, Eichenbaum & Vigfusson, 2003) are not new constructs, the reality of the industrial age was and is a continuing reduction in timeline for relevance and lifetime for a specific technology and the related skills and expertise base required for its effective implementation. This, combined with increasing pressures for innovation (Tidd & Bessant, 2013) and at times severe impacts from both local and global economic environments (Hitt, Ireland & Hoskisson, 2011) raises serious challenges for contemporary management teams seeking to strategically position a company and its technology base advantageously, relative to its suppliers, competitors and customers, as well as in predictive readiness for future technological change and opportunistic adaptation. In effect, the life-cycle of a technology has become typically one of disruptive change and rapid adjustment, followed by a plateau as a particular technology or process captures and holds its position against minor challenges, eventually to be displaced by yet another alternative (Bower & Christensen, 1995)
Constraining new physics through the spin density matrix
No full textThe negative results obtained by searches for heavy new resonances are excluding ever more of the potential phase space where they could be directly produced at the LHC, hinting that they might be out of reach given our current facilities. This in turn makes the Effective Field Theory (EFT) description increasingly attractive as a way to explore the physics beyond the Standard Model (SM). In this approach the focus is on precision measurements and constraints are set on the EFT operators in terms of deviations with respect to SM predictions. In this talk, the basics of the EFT approach and operators will be discussed, with an emphasis on those affecting the top pair production process and how are they constrained through a measurement of the top pair spin density matrix in the dileptonic channel by the CMS experiment
Evidence for the 125 GeV Higgs boson decaying to a pair of τ leptons
Get PDFOpen Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.A search for a standard model Higgs boson decaying into a pair of τ leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of 4.9 fb−1 at a centre-of-mass energy of 7 TeV and 19.7 fb−1 at 8 TeV. Each τ lepton decays hadronically or leptonically to an electron or a muon, leading to six different final states for the τ -lepton pair, all considered in this analysis. An excess of events is observed over the expected background contributions, with a local significance larger than 3 standard deviations for m H values between 115 and 130 GeV. The best fit of the observed H → τ τ signal cross section times branching fraction for m H = 125 GeV is 0.78 ± 0.27 times the standard model expectation. These observations constitute evidence for the 125 GeV Higgs boson decaying to a pair of τ leptons
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