Particle identification in ALICE: a Bayesian approach

Abstract

We present a Bayesian approach to particle identification (PID) within the ALICE experiment. The aim is to more effectively combine the particle identification capabilities of its various detectors. After a brief explanation of the adopted methodology and formalism, the performance of the Bayesian PID approach for charged pions, kaons and protons in the central barrel of ALICE is studied. PID is performed via measurements of specific energy loss ($\mathrm{d}E/\mathrm{d}x$) and time-of-flight. PID efficiencies and misidentification probabilities are extracted and compared with Monte Carlo simulations using high-purity samples of identified particles in the decay channels ${\mathrm{K}}_S^0\to {\pi }^{-}{\pi }^{+}$, $\varphi \to {\mathrm{K}}^{-}{\mathrm{K}}^{+}$, and $\Lambda \to \mathrm{p}{\pi }^{-}$ in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. In order to thoroughly assess the validity of the Bayesian approach, this methodology was used to obtain corrected $p_{\mathrm{T}}$ spectra of pions, kaons, protons, and D${}^0$ mesons in pp collisions at $\sqrt{s}=7$ TeV. In all cases, the results using Bayesian PID were found to be consistent with previous measurements performed by ALICE using a standard PID approach. For the measurement of D${}^0\to {\mathrm{K}}^{-}{\pi }^{+}$, it was found that a Bayesian PID approach gave a higher signal-to-background ratio and a similar or larger statistical significance when compared with standard PID selections, despite a reduced identification efficiency. Finally, we present an exploratory study of the measurement of ${\Lambda }_{\mathrm{c}}^{+}\to \mathrm{p}{\mathrm{K}}^{-}{\pi }^{+}$ in pp collisions at $\sqrt{s}=7$ TeV, using the Bayesian approach for the identification of its decay products.

32 pages, 15 captioned figures, 1 table, authors from page 26, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/2285

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Cited by in corpus (18)

• Production of charged pions, kaons and (anti-)protons in Pb-Pb and inelastic pp collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Multiplicity dependence of light-flavor hadron production in pp collisions at $\sqrt{s}$ = 7 TeV
• D-meson production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV and in pp collisions at $\sqrt{s}=7$ TeV
• ${\Lambda }_{\mathrm{c}}^{+}$ production in pp collisions at $\sqrt{s}=7$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production and baryon-to-meson ratios in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV at the LHC
• Production of light-flavor hadrons in pp collisions at $\sqrt{s}$ = 7 and $\sqrt{s}$ = 13 TeV
• Higher harmonic flow coefficients of identified hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production in pp and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Measurement of prompt D${}^0$, ${\Lambda }_c^{+}$, and ${\Sigma }_c^{0,++}$(2455) production in pp collisions at $\sqrt{s}=13$ TeV
• The ALICE Transition Radiation Detector: construction, operation, and performance
• Anisotropic flow and flow fluctuations of identified hadrons in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Charm production and fragmentation fractions at midrapidity in pp collisions at $\sqrt{s}=13$ TeV
• Elliptic flow of identified hadrons in small collisional systems measured with ALICE
• Non-linear flow modes of identified particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Particle identification with machine learning from incomplete data in the ALICE experiment
• Machine-learning-based particle identification with missing data
• Classifiers for centrality determination in proton-nucleus and nucleus-nucleus collisions
• Genetic Algorithm for determination of the event collision time and particle identification by time-of-flight at NICA SPD