Top quark IIHE Future interests  Towards data taking → new software  Have a broader physics output  Link theory-experiment  Calibration and commissioning tools Jorgen D’Hondt

June 2006, Louvain-la-Neuve (CP3)Jorgen D'Hondt (Brussels - IIHE)2 Future directions (next 2-3 years) Profit from the experience on reconstruction studies from the past : 1)Prepare for top quark physics (slide-1)  new event selection taking into account an incomplete detector and a not well known detector performance  develope analyse to get first top mass and cross sections measurement  most of the other measurements require more accumulated data (resonance searches, anomalous couplings, etc.) 2)Calibration and commissioning (slide-2)  develope tools to calibrate the jet energy scale and the b-tagging performance using top quark events  to be applied on first 0.1-1fb -1 of data  special accelerator settings (no pile-up for example)  develope tools to observe obvious problems between data & simulation 3)Search beyond the Standard Model (slide-3)  many signals of new physics could be visible in top quark processes  develope statistical tools to quantify possible deviations

June 2006, Louvain-la-Neuve (CP3)Jorgen D'Hondt (Brussels - IIHE)3 Prepare for first data (0.1-1fb -1 ) 1)Event selection  develope reconstruction tools which can be applied on the first data  jet reconstruction is a key element for top quarks → but how can we define jets at start-up ?  design a very simple event selection which is not very efficient but is robust against detector performance 2)Detector understanding  important parts of the detector will not be there (vertex, forward ECAL)  which parts of the detector are most crucial for reconstructing the top quark events ?  can we only use the barrel part of the detector ? is this unbiased ? 3)Physics results (example from ATLAS study)  few physics results will be poluted by our understanding of the QCD background → how to deal with this ?  a rough confirmation of Tevatrons top quark mass and cross section extrapolation is crucial

June 2006, Louvain-la-Neuve (CP3)Jorgen D'Hondt (Brussels - IIHE)4 Calibration and commissioning 1)Top quark decays for jet energy scale calibration  single-lepton decay channel  apply W-mass and top quark mass constraint to estimate the jet energy scale → it was shown that this is possible with few data (less than 1fb -1 )  how to adapt our analyse for these first data ? 2)Top quark decays for b-tag performance  di-lepton decay channel  mainly the barrel will be used at start-up (missing forward ECAL)  how well can we estimate/confirm the b-tag performance ?  how to adapt our analyse for these first data ? 3)Search for obvious deviations between data and simulation  top quark events are complicated and are a first check for the performance of the complete detector  any deviations between data and simulation can be useful for many other processes  prepare to interprete these deviations

June 2006, Louvain-la-Neuve (CP3)Jorgen D'Hondt (Brussels - IIHE)5 Search beyond the Standard Model 1)Identify sensitive differential distributions  consider general models beyond the Standard Model (SUSY,TC,etc.)  develope a robust event selection to enhance a general signal  check for which kinematic or other observables a deviation from the Standard Model is clear 2)Statistical method for hypothese testing  learn from Tevatron paper hep-ex/ (CDF Run-II)  combined Kolmogorov-Smirnov test for example  check robustness of the method  prepare to interprete a possible deviations 3)Collaboration  clearly with theorists!  same tools can be applied on single-top processes

June 2006, Louvain-la-Neuve (CP3)Jorgen D'Hondt (Brussels - IIHE)6 General issues connected to top quark physics 1)Colour Reconnection  gluon/colour exchange between colour strings in the same event  existance confirmed in meson decay, but not in WW at LEP  could be present in top quark events  first phenomenological implementations are being developed  possible this has to be taken into account or measured at the LHC 2)Definition of top quark mass  we measure a pole-mass but in Standard Model calculations an mass is needed in an MS-bar scheme  how can we make our estimators more robust for these theoretical uncertainties ? 3)Can we make our top quark studies more robust versus general theoretical uncertainties ?  for example radiation effects of higher order effects 4)Extend our studies to more top quark pair decay channels