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Search for strange particles Physics Discussion of the ALICE Measurement

This physics discussion revolves around the ALICE measurement focusing on V0 and cascade decays of strange hadrons, including K0s, Λ, anti-Λ, Ξ-. Utilizing the simplified ALICE event display based on ROOT, participants will visually analyze small event samples and perform statistical analysis. The exercise involves visual identification, classification, and analysis of V0 decays and cascades. Through the analysis tool, students will fit background and peaks, subtracting to determine the number of particles. The goal is to understand data analysis, particle decays, conservation laws, and invariant mass. By comparing yields and using particle ratios, participants will calculate the temperature of Quark Gluon Plasma. The exercises cover merging results, fitting peaks, calculating yields, and discussing strangeness enhancement. The proposal includes using spreadsheets to collect and compare results. Discussions will involve comparing institute and ALICE results, addressing errors, and exploring physics implications.

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Search for strange particles Physics Discussion of the ALICE Measurement

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  1. Search for strange particles • Physics Discussion of the ALICE Measurement • topic of the measurement, what should be combined/shown/discussed (and how) • the signature • V0 (and cascade) decays of strange hadrons (K0s, Λ, anti-Λ, Ξ-) • the tools • Simplified ALICE event display based on ROOT • Combine visual analysis of small event sample with large statistics analysis • The results ALICE exercise - D. Hatzifotiadou

  2. Visual identification of V0 decays and cascades Ξ-→π-Λ→ π-p π- K0s→ p+p- Bachelor (single track) and two opposite tracks coming from a secondary vertex L ®p-p anti Λ→ p-π+ Two opposite tracks from a secondary vertex Monte Carlo PbPb event ALICE exercise - D. Hatzifotiadou

  3. The analysis tool : simplifiedALICE event display based on ROOT 3 views of ALICE – 3D, rφ, rz V0 finder and cascade finder Highlights V0 (cascade) Recognise from decay pattern Calculate invariant mass Classify according to mass Fill tables Fillhistograms Runs on LINUX, Ubuntu, MacOSX ALICE exercise - D. Hatzifotiadou

  4. ALICE exercise - D. Hatzifotiadou From PawelDebski

  5. From PawelDebski ALICE exercise - D. Hatzifotiadou

  6. ALICE exercise - D. Hatzifotiadou

  7. 2ndpart of exercise • Analyse big event sample (2000 events) • Invariant mass histograms for Ks, L, anti-L • Fit 2nd degree polynomial to background • Fit gaussian to peak • Get number of Ks, L, anti-L after background subtraction + option to see combinatorial background (without common secondary vertex requirement) ALICE exercise - D. Hatzifotiadou

  8. ALICE exercise - D. Hatzifotiadou

  9. Outline of exercise • Students (each group): Visual analysis of 30 events – tables + invariant mass histograms • Institute (all groups): Add up numbers / merge histograms • 30-event samples for visual analysis, 7 TeV proton-proton (6) • 5-event sample Pb-Pb (1) • Students (each group): Analysis of 2000 events- invariant mass histograms • Students (each group): Try to fit background / peak / subtract -> find number of particles • Institute (all groups): Merge histograms • Institute (all groups): Fit background / peak / subtract -> find number of particles • 2000 event samples 7 TeV proton-proton (7) • 1500 event sample lead-lead • Calculate yields of each particle type • (assumptions on initial number of events from which the sample has been extracted • correction factors for efficiency) ALICE exercise - D. Hatzifotiadou

  10. Goals • Flavour of data analysis • Concept of particle decays • Concept of some conservation laws and invariant mass • Results • Count numbers of particle species (K0s, Λ, anti-Λ) • Calculate yields of particles • Compare with ALICE results • Use particle ratios to calculate T (temperature of QGP) • For the institutes, if enough time… • Strangeness enhancement : need to make ratio i.e. yield of Λin pp / yield of Λ in Pb-Pb • Show published strangeness enhancement plots from ALICE (+ other HI experiments) • Explain on the plots what they would need to measure, in addition, to reproduce them ALICE exercise - D. Hatzifotiadou

  11. Proposal to institutes to use, for the collection of results, such a spreadsheet on http://www.editgrid.com/user/alice-masterclass/results-2012-example.csv Username alice-masterclass Password alice ALICE exercise - D. Hatzifotiadou

  12. Proposal to moderators to use, for the collection of all results, such a spreadsheet on http://www.editgrid.com/user/alice-masterclass/results-2012-collection.csv Username alice-masterclass Password alice ALICE exercise - D. Hatzifotiadou

  13. Discussion • Compare results of different institutes • with each other • with ALICE results • Mention errors • Physics discussion • Also in the proposal to the institutes to discuss locally • Calculation of the temperature of the Quark Gluon Plasma from particle ratios ALICE exercise - D. Hatzifotiadou

  14. Temperature calculation from particle ratios The number of produced Kaons and Lambdas can be used as a thermometer of the matter produced in the collisions NK0s = 123.9 ± 7 NΛ = 28.8 ± 3 Nπ+ = 792.1 ± 44.1 For central (0-5%) PbPb NK0s/ Nπ+ = 0.156 ± 0.012 NΛ / Nπ+ = 0.036 ± 0.004 T = 120-180 MeV Corresponds to ~1012 K Curves produced with thermal model. Relates relative abundance of particles with temperatures in the fireball ALICE exercise - D. Hatzifotiadou

  15. Backup slide ALICE exercise - D. Hatzifotiadou

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