Kisel, I.

Kulakov, I.

Vassiliev, I.

Zyzak, M.

GSI Repository

The KF Particle Finder package for short-lived particles reconstructionfor CBM∗M. Zyzak1,2,3, I. Kisel1,2,3, I. Kulakov1,2,3, and I. Vassiliev1,31Uni-Frankfurt, Germany; 2FIAS, Frankfurt am Main, Germany; 3GSI, Darmstadt, GermanyToday the most interesting physics is hidden in the prop-erties of short-lived particles which can not be registereddirectly by a detector system but only reconstructed fromtheir decay products. Also, short-lived particles which havea very small production probability are of the particular in-terest. Thus, a statistically significant result can be obtainedonly in case of the operation with a high rate of collisionsup to 107 Hz. This raises the problem of data processingand storage. Therefore only those events are selected forthe further analysis that can potentially contain interestingparticles. The CBM experiment requires the full recon-struction of events, including reconstruction of short-livedparticles, already at the selection stage.A fast and efficient KF Particle Finder package for short-lived particles reconstruction and selection is developed forthe CBM experiment. A search for about 50 decay chan-nels has been currently implemented. At first, all tracksare divided into groups of secondary and primary tracksfor further analysis. Primary tracks are those, which areproduced directly in the collision of beam and target ions.Tracks from decays of resonances (strange, multi-strangeand charmed resonances, light vector mesons, charmo-nium) are also considered as primaries since they are pro-duced directly at the point of the primary vertex. Secondarytracks are produced by the short-lived particles, which de-cay not in the primary vertex point and can be well sep-arated. These particles include strange particles (K 0s andΛ), multi-strange hyperons (Ξ and Ω) and charmed parti-cles (D0, D±,D±s and Λc).Figure 1: Block diagram of the KF Particle Finder algo-rithm.Then tracks are combined according to the block dia-∗This work was supported by the Hessian LOEWE initiative throughthe Helmholtz International Center for FAIR (HIC for FAIR) and EU-FP7 HadronPhysics2. Das Projekt wird vom Hessischen Ministerium fuerWissenschaft und Kunst gefoerdert.gram in Figure 1 and particle-candidates are produced fromthese combinations. The particles are reconstructed withthe KF Particle package [1], which is based on the Kalmanfilter (KF) method and finds parameters of the particle, suchas decay vertex, momentum, energy, mass, etc., togetherwith their errors. All particles of the event are reconstructedat once that makes the algorithm local with respect to thedata and therefore very fast.KF Particle Finder achieves a high efficiency of the parti-cle reconstruction. For example, efficiencies ofK 0s , Λ, Ξ−and Ω− reconstruction are 15.3%, 17.8%, 5.0% and 2.5%respectively for 240 000 of minimum bias Au+Au colli-sions at 25 AGeV. The corresponding signal to backgroundratios are 3.5, 5.1, 42.2 and 4.3.In order to utilize all possible resources of modern CPUsand to achieve the highest possible speed KF ParticleFinder is based on the SIMD instructions. Also, the al-gorithm has been parallelized between cores of the mod-ern CPUs and demonstrates a strong linear scalability onmany-core servers with respect to the number of cores (seeFigure 2).Figure 2: Scalability of the KF Particle Finder pack-age with minimum bias Au+Au events at 25 AGeV on amany-core server lxir075 equipped with four Intel E7-4860(2.27 GHz) CPUs.Summarizing, the KF Particle Finder package recon-structs about 50 of the most important decay channels forthe CBM experiment with a high efficiency and a highsignal to background ratio achieving speed of 1.5 ms perAu+Au minimum bias collisions at 25 AGeV on a singlecore.References[1] S. Gorbunov and I. Kisel, Reconstruction of decayed particlesbased on the Kalman filter. CBM-SOFT-note-2007-003, 7 May2007.PHN-NQM-EXP-50 GSI SCIENTIFIC REPORT 201280

The KF Particle Finder package for short-lived particles reconstruction for CBM

The KF Particle Finder package for short-lived particles reconstructionfor CBM∗M. Zyzak1,2,3, I. Kisel1,2,3, I. Kulakov1,2,3, and I. Vassiliev1,31Uni-Frankfurt, Germany; 2FIAS, Frankfurt am Main, Germany; 3GSI, Darmstadt, GermanyToday the most interesting physics is contained in theproperties of short-lived particles which can not be regis-tered by a detector system directly but only reconstructedthrough their decay products. Also, short-lived particleswhich have a very small production probability are of theparticular interest. Thus, a statistically significant resultcan be obtained only in case of the operation with a highrate of collisions up to 107 Hz. This raises the problem ofdata processing and storage. Therefore only those eventsare selected for the further analysis that can potentially con-tain interesting particles. The CBM experiment requiresthe full reconstruction of events, including reconstructionof short-lived particles, already at the selection stage.A fast and efficient algorithm based on the Kalman fil-ter (KF) method for finding, reconstruction and selectionof short-lived particles is developed. A search for about 50particles (decay channels) has been implemented. At firstall tracks are divided into two groups for a further analy-sis: secondary and primary. Secondary tracks are producedin a decay of short-lived particles that have sufficient life-time to move away from the primary vertex. These par-ticles are strange particles (K0s -mesons and Λ-hyperons),multi-strange hyperons (Ξ and Ω) and charmed particles(D0, D±, D±s and Λc). Primary tracks are those, whichare produced directly in the collision of a beam with a tar-get. Tracks from the resonances decays (strange, multi-strange and charmed resonances, light vector mesons, char-monium) are also considered as primary since they are pro-duced directly at the point of the primary vertex due to theextremely small lifetime.Figure 1: Block diagram of the KF Particle Finder algo-rithm.∗This work was supported by the Hessian LOEWE initiative throughthe Helmholtz International Center for FAIR (HIC for FAIR) and EU-FP7 HadronPhysics2. Das Projekt wird vom Hessischen Ministerium fuerWissenschaft und Kunst gefoerdert.Selected tracks are combined into particle-candidates ac-cording to the block diagram in Figure 1. The particles arereconstructed with the KFParticle package [1]. All parti-cles are reconstructed in one go that makes the algorithmlocal with respect to the data and therefore very fast.KF Particle Finder achieves a high efficiency of the par-ticle reconstruction. For example, the efficiency of thestrange particles reconstruction for 240 000 of minimumbias Au+Au collisions at 25 AGeV as well as a signal tobackground ratio is given in Table 1.Particle K0s Λ Ξ− Ω−Efficiency, % 15.3 17.8 5.0 2.5S/B 3.5 5.1 42.2 4.3Table 1: The efficiency and a signal to background ratio(S/B) for strange particles.In order to utilize all possible resources of modern CPUsand to achieve the highest possible speed KF ParticleFinder is based on the SIMD instructions. Also, the al-gorithm has been parallelized between cores of the mod-ern CPUs and demonstrates a strong linear scalability onmany-core servers with respect to the number of cores (seeFigure 2).Figure 2: Scalability of the KF Particle Finder pack-age with minimum bias Au+Au events at 25 AGeV on amany-core server lxir075 equipped with four Intel E7-4860(2.27 GHz) CPUs.Summarizing, the KF Particle Finder package recon-structs about 50 of the most important decay channels forthe CBM experiment with a high efficiency and a highsignal to background ratio achieving speed of 1.5 ms perAu+Au minimum bias collisions at 25 AGeV on a singlecore.References[1] S. Gorbunov and I. Kisel, Reconstruction of decayed particlesbased on the Kalman filter. CBM-SOFT-note-2007-003, 7 May2007.GSI SCIENTIFIC REPORT 2012 PHN-NQM-EXP-4979

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The KF Particle Finder package for short-lived particles reconstruction for CBM

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