Data-driven precision determination of the material budget in ALICE

Abstract

The knowledge of the material budget with a high precision is fundamental for measurements of direct photon production using the photon conversion method due to its direct impact on the total systematic uncertainty. Moreover, it influences many aspects of the charged-particle reconstruction performance. In this article, two procedures to determine data-driven corrections to the material-budget description in ALICE simulation software are developed. One is based on the precise knowledge of the gas composition in the Time Projection Chamber. The other is based on the robustness of the ratio between the produced number of photons and charged particles, to a large extent due to the approximate isospin symmetry in the number of produced neutral and charged pions. Both methods are applied to ALICE data allowing for a reduction of the overall material budget systematic uncertainty from 4.5% down to 2.5%. Using these methods, a locally correct material budget is also achieved. The two proposed methods are generic and can be applied to any experiment in a similar fashion.

arXiv comment22 pages, 5 captioned figures, 3 tables, authors from page 17, published version, figures at http://alice-publications.web.cern.ch/node/9207

References in corpus (30)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• An Introduction to PYTHIA 8.2
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• Performance of the ALICE Experiment at the CERN LHC
• The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
• Performance of the ALICE VZERO system
• Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
• The production of photons in relativistic heavy-ion collisions
• Hadronic Production of Thermal Photons
• Production of charged pions, kaons and (anti-)protons in Pb-Pb and inelastic pp collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Direct photon production in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$ = 2.76 TeV
• Transverse momentum spectra and nuclear modification factors of charged particles in pp, p-Pb and Pb-Pb collisions at the LHC
• Neutral pion and $\eta$ meson production in proton-proton collisions at $\sqrt{s}=0.9$ TeV and $\sqrt{s}=7$ TeV
• Hard diffraction in hadron--hadron interactions and in photoproduction
• Charged-particle multiplicities in proton-proton collisions at $\sqrt{s}$ = 0.9 to 8 TeV
• Pseudo-Critical Enhancement of Thermal Photons in Relativistic Heavy-Ion Collisions
• Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions
• Production of light-flavor hadrons in pp collisions at $\sqrt{s}$ = 7 and $\sqrt{s}$ = 13 TeV
• ${\pi }^0$ and $\eta$ meson production in proton-proton collisions at $\sqrt{s}=8$ TeV
• Universal Parametrization of Thermal Photon Rates in Hadronic Matter
• Neutral pion and $\eta$ meson production in p-Pb collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}=5.02$ TeV
• Ideal Hydrodynamics for Bulk and Multistrange Hadrons in $\sqrt{s_{NN}}$=200\,AGeV Au-Au Collisions
• Collision centrality and ${\tau }_0$ dependence of the emission of thermal photons from fluctuating initial state in ideal hydrodynamic calculation
• Direct photon production at low transverse momentum in proton-proton collisions at $\sqrt{s}$ = 2.76 and 8 TeV
• Thermal photon emission from the pi-rho-omega system
• Neutral pion and $\eta$ meson production at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV
• Calibration of the photon spectrometer PHOS of the ALICE experiment
• Electromagnetic probes
• Performance of the ALICE Electromagnetic Calorimeter

Cited by in corpus (1)

• Measurement of $\omega$ meson production in pp and p$-$Pb collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}=5.02$ TeV