Dergi makalesi Açık Erişim

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

2017    CERN İşbirliği

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 $\text{TeV}$ for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb ${}^{-1}$ of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 $\text{TeV}$ . The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 $\text{GeV}$ is quantified using a novel, data-driven, method. The method uses the energy loss, $\phantom{\rule{0.333333em}{0ex}}\text{d}E/dx$ , to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is $0.061±0.006\phantom{\rule{4pt}{0ex}}\text{(stat.)}±0.014\phantom{\rule{4pt}{0ex}}\text{(syst.)}$ and $0.093±0.017\phantom{\rule{4pt}{0ex}}\text{(stat.)}±0.021\phantom{\rule{4pt}{0ex}}\text{(syst.)}$ for jet transverse momenta of 200–400 $\text{GeV}$ and 1400–1600 $\text{GeV}$ , respectively.