Top quark physics @ IIHE Future interests

1. Top quark physics @ IIHEFuture interests Towards data taking → new software Have a broader physics output Link theory-experiment Calibration and commissioning tools Jorgen D’Hondt

2. Future directions (next 2-3 years) • Profit from the experience on reconstruction studies from the past : • 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.) • 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 • 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 Jorgen D'Hondt (Brussels - IIHE)

3. Prepare for first data (0.1-1fb-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 • 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 ? • 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 Jorgen D'Hondt (Brussels - IIHE)

4. Calibration and commissioning • 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 ? • 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 ? • 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 Jorgen D'Hondt (Brussels - IIHE)

5. Search beyond the Standard Model • 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 • Statistical method for hypothese testing • learn from Tevatron paper hep-ex/0412042 (CDF Run-II) • combined Kolmogorov-Smirnov test for example • check robustness of the method • prepare to interprete a possible deviations • Collaboration • clearly with theorists! • same tools can be applied on single-top processes Jorgen D'Hondt (Brussels - IIHE)

6. General issues connected to top quark physics • 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 • 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 ? • Can we make our top quark studies more robust versus general theoretical uncertainties ? • for example radiation effects of higher order effects • Extend our studies to more top quark pair decay channels Jorgen D'Hondt (Brussels - IIHE)