Wuppertal 2015 – scientific programme

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T: Fachverband Teilchenphysik

T 46: Top: Boosted b-tagging, single top

T 46.3: Talk

Tuesday, March 10, 2015, 17:15–17:30, L.09.31 (HS 11)

Measurement of the double-vertex reconstruction efficiency of the Inclusive Vertex Finder with accidentally overlapping b-jets in ttbar events — Ivan Marchesini, Dominik Nowatschin, Jochen Ott, Alexander Schmidt, and •Heiner Tholen — University of Hamburg

In LHC Run II, CMS b-tagging algorithms will employ a new core algorithm, named Inclusive Vertex Finder (IVF). The IVF is designed to perform decay vertex reconstruction of long-lived particles, such as B hadrons. Using only tracks from the silicon tracker, it does not depend on jet clustering and allows for higher reconstruction efficiency of decay vertices, which particularly applies to topologies with two or more decay vertices at low distance. Thus, the IVF will offer increased sensitivity for SM measurements (e.g. angular correlations), but also for the search of BSM physics (e.g. final states with boosted Higgs bosons decaying into b-quarks).

For the first time, the dependence of the IVF reconstruction efficiency on the distance of vertices in the η−φ plane is investigated with a data-driven approach. We use a clean set of top quark pair events, selected from data recorded in 2012 in pp-collisions at 8 TeV with the CMS detector, and perform a template fit to a 2D-distribution of the masses of the vertices in an event. Correction factors are derived for the application to simulated events. We conclude that our technique will enable precise calibration of double vertexing with the IVF in the LHC Run II.