The effect of event background uctuations on charged particle jet reconstruction in Pb-Pb collisions at √sNN = 2:76TeV has been measured with the ALICE experiment. The main sources of non-statistical uctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high pt particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti-kt jet finder. The inuence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track pt between 0.15 GeV/c and 2 GeV/c. For embedded jets reconstructed from charged particles with pt > 0:15 GeV/c, the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/c, which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the uctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured uctuations with steeply falling spectra. © 2012 SISSA.
Measurement of event background uctuations for charged particle jet reconstruction in Pb-Pb collisions at √sNN = 2:76 TeV
BRUNO, GIUSEPPE EUGENIO;CARMINATI, FLAVIO;COSTA, FIAMMETTA;DAS, KESHABANANDA;DI BARI, DEBORAH;FERRETTI, ANDREA;MULLER, HEIKO;PERINI, DAVIDE;ROY, PARTHA PRATIM;SANTORO, ROMUALDO;SEGATO, GINO;TOIA, ALESSIO;
2012-01-01
Abstract
The effect of event background uctuations on charged particle jet reconstruction in Pb-Pb collisions at √sNN = 2:76TeV has been measured with the ALICE experiment. The main sources of non-statistical uctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high pt particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti-kt jet finder. The inuence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track pt between 0.15 GeV/c and 2 GeV/c. For embedded jets reconstructed from charged particles with pt > 0:15 GeV/c, the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/c, which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the uctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured uctuations with steeply falling spectra. © 2012 SISSA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.