1,053 research outputs found

    SiLC simulation status report

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    The SiLC - Silicon for the Linear Collider - collaboration aims to develop silicon detector technology for tracking in the international linear collider experiments. The R & D programme involves a substantial effort in simulation of the response of detector designs. In this contribution, an overview of ongoing efforts in this area is given.Comment: proceedings of LCWS0

    Top-quark mass measurements at the LHC: alternative methods

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    Alternative top quark mass determinations can provide inputs to the world average with orthogonal systematic uncertainties and may help to refine the interpretation of the standard method. Among a number of recent results I focus on the extractions by ATLAS and CMS of the top quark pole mass from the top quark pair and tt + 1 jet production cross-section, which have now reached a precision of 1%

    Top-quark pair-production with one jet and parton showering at hadron colliders

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    We present heavy-flavor production in association with one jet in hadronic collisions matched to parton shower Monte Carlo predictions at next-to-leading order QCD with account of top-quark decays and spin correlations. We use the POWHEGBOX for the interface to the parton shower programs PYTHIA or HERWIG. Phenomenological studies for the LHC and the Tevatron are presented with particular emphasis on the inclusion of spin-correlation effects in top decay and the impact of the parton shower on the top-quark charge asymmetries. As a novel application of the present calculation the measurement of the top-quark mass is discussed.Comment: 4 pages latex, 6 figures, Procs. of XX International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2012

    Weight change and quality of life in a community-based population

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    *Objectives:* This study investigates the longitudinal association between 5-year weight change and quality of life (QoL) in Dutch men and women.

*Design:* A prospective cohort study (1998, 2000, 2003) in a population based sample. Subjects: 2,414 men and women from the Maastricht region of the Netherlands.

*Measurements:* QoL outcomes were measured by the RAND-36 (eight subscales and two overall composite scores, physical and mental health (PCS and MCS)). Weight was measured on a scale. Weight change was calculated as change in weight between 1998 and 2003. In addition, 5-year weight change was also categorized in three groups: weight losers, weight maintainers, and weight gainers. All analyses were stratified for gender.

*Results:* A total of 598 men (50%) and 646 women (54%) maintained their weight, 177 men (15%) and 163 women (14%) lost more than 2.5 kg, and 410 men (35%) and 379 women (32%) gained more than 2.5 kg. Associations between 5-year weight change and QoL were found for MCS ([beta] = 0.13, 95% CI: 0.02|0.24) in women, and PCS ([beta] = -0.09, 95% CI: -0.17|-0.00; [beta] = -0.10, 95% CI: -0.19|-0.01) in men and women respectively. Moreover, associations between weight change and QoL were most pronounced for women of normal weight and obese men. Furthermore, in both genders, weight gainers showed a greater reduction on all physical components of QoL compared with weight maintainers. However, after 5-years weight gainers and weight losers did not significantly differ from weight maintainers in the mean change of MCS and PCS.

*Conclusion:* Weight gain was inversely associated with the physical domains of QoL in women and obese men. Conversely, in women, weight gain was positively associated with the mental domains of QoL. No differences between weight losers and weight gainers were found in mean change of QoL compared with weight maintainers

    Determination of the top quark mass circa 2013: methods, subtleties, perspectives

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    We present an up-to-date overview of the problem of top quark mass determination. We assess the need for precision in the top mass extraction in the LHC era together with the main theoretical and experimental issues arising in precision top mass determination. We collect and document existing results on top mass determination at hadron colliders and map the prospects for future precision top mass determination at e+e- colliders. We present a collection of estimates for the ultimate precision of various methods for top quark mass extraction at the LHC.Comment: 26 pages. Snowmass White Pape

    Global and optimal probes for the top-quark effective field theory at future lepton colliders

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    We study the sensitivity to physics beyond the standard model of precise top-quark pair production measurements at future lepton colliders. A global effective-field-theory approach is employed, including all dimension-six operators of the Warsaw basis which involve a top-quark and give rise to tree-level amplitudes that interfere with standard-model e+ettˉbW+bˉWe^+e^-\to t\,\bar t\to bW^+\bar bW^- ones in the limit of vanishing bb-quark mass. Four-fermion and CP-violating contributions are taken into account. Circular-collider-, ILC- and CLIC-like benchmark run scenarios are examined. We compare the constraining power of various observables to a set of statistically optimal ones which maximally exploit the information contained in the fully differential bW+bˉWbW^+\bar bW^- distribution. The enhanced sensitivity gained on the linear contributions of dimension-six operators leads to bounds that are insensitive to quadratic ones. Even with statistically optimal observables, two centre-of-mass energies are required for constraining simultaneously two- and four-fermion operators. The impact of the centre-of-mass energy lever arm is discussed, that of beam polarization as well. A realistic estimate of the precision that can be achieved in ILC- and CLIC-like operating scenarios yields individual limits on the electroweak couplings of the top quark that are one to three orders of magnitude better than constraints set with Tevatron and LHC run I data, and three to two hundred times better than the most optimistic projections made for the high-luminosity phase of the LHC. Clean global constraints can moreover be obtained at lepton colliders, robustly covering the multidimensional effective-field-theory space with minimal model dependence.Comment: 6 appendices, 66 pages, 37 figures, 10 tables, codes and numerics at https://github.com/gdurieux/optimal_observables_ee2tt2bwb

    CP-violating top quark couplings at future linear e+ee^+e^- colliders

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    We study the potential of future lepton colliders to probe violation of the CP symmetry in the top quark sector. In certain extensions of the Standard Model, such as the two-Higgs-doublet model (2HDM), sizeable anomalous top quark dipole moments can arise, that may be revealed by a precise measurement of top quark pair production. We present results from detailed Monte Carlo studies for the ILC at 500~\GeV{} and CLIC at 380~\gev{} and use parton-level simulations to explore the potential of high-energy operation. We find that precise measurements in e+ettˉe^+e^- \rightarrow t\bar{t} production with subsequent decay to lepton plus jets final states can provide sufficient sensitivity to detect Higgs-boson-induced CP violation in a viable two-Higgs-doublet model. The potential of a linear e+ee^+e^- collider to detect CP-violating electric and weak dipole form factors of the top quark exceeds the prospects of the HL-LHC by over an order of magnitude
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