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The ALICE Measurement Looking for strange particles in ALICE

The ALICE Measurement Looking for strange particles in ALICE Find channel possibl e to observe visually Requirement : physics measurement ALICE strong on tracking and PID – not enough calorimeter coverage Proposal to look for V0 and cascade decays (of strange hadrons)

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The ALICE Measurement Looking for strange particles in ALICE

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  1. The ALICE Measurement • Looking for strange particles in ALICE • Find channel possible to observe visually • Requirement : physics measurement • ALICE strong on tracking and PID – not enough calorimeter coverage • Proposal to look for V0 and cascade decays (of strange hadrons) • Strangeness enhancement : first signature for quark gluon plasma • Seen by previous heavy ion experiments • Need to compare lead lead collision data with proton proton data • Develop and test with firstLHC data (900 GeV proton proton) 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. Looking for strange particles in ALICE (K0s, Λ, Ξ-) recognisefrom decay pattern calculate invariant mass classify according to mass fill tables fillhistograms • Simplified ALICE event display based on ROOT (LINUX, Ubuntu, MacOSX) • V0 finder and cascade finder • P.Debski, P.Foka, DH, B.Hippolyte, A.Maire, M.Tadel ALICE exercise - D. Hatzifotiadou

  4. ALICE exercise - D. Hatzifotiadou From PawelDebski

  5. From PawelDebski ALICE exercise - D. Hatzifotiadou

  6. Goals • Flavour of data analysis • Concept of particle decays • Concept of some conservation laws and invariant mass • 2.76 TeV lead collision data (end 2010) not available for the exercise • Count numbers of particle species (K0s, Λ, anti-Λ and Ξ-)* • Calculate yields of particles • Compare with Monte Carlo predictions • Compare with ALICE published results • Some discussion of errors • First (experimental) phase • No background subtraction, efficiency etc • No Windows implementation • *in a sample of 100 events ALICE exercise - D. Hatzifotiadou

  7. ALICE exercise - D. Hatzifotiadou

  8. Some numbers • FrascatiMasterClass : 41 pupils from all over Italy, 2 pupils /school • part of a four-day programme in Frascati “Stage InvernaleResidenziale”, 7-10 February (outside “International Masterclasses” schedule) • http://www.lnf.infn.it/edu/stagelnf/2011/masterclass11.html • Graz: problems with ROOT installation; did LEP exercise • Bergen : 70 pupils • Oslo : 35 pupils (?) • GSI Darmstadt/Frankfurt 30 pupils • Torino : 80 pupils in the morning, 56 staying for the exercise • Lodz : 60 pupils + 3 teachers • Nantes : 35 pupils + 3 adults (1 class) • http://indico.in2p3.fr/internalPage.py?pageId=0&confId=5167 • Heidelberg : 36 pupils + 2 teachers (2 classes) • CERN : 27 pupils + 3 teachers (classe première scientifiqueLycée International de Ferney) • Debriefing meeting + EVO 18.3.2011 • Debriefing EVO Meeting 1.4.2011 ALICE exercise - D. Hatzifotiadou

  9. http://cdsweb.cern.ch/record/1341286 CERN 25.3.2011 ALICE exercise - D. Hatzifotiadou

  10. http://indico.in2p3.fr/internalPage.py?pageId=0&confId=5167Subatech Nantes 25.3.2011 ALICE exercise - D. Hatzifotiadou

  11. Feedback • Generalappreciation varies • Some found difficult to understand - others liked the exercise • Somewere enthusiastic – others found it boring • Event samples generated a lot of discussion • In 100 events include K0s, Λ, anti-Λ(percentage as from data analysis) • and Ξ–(10 x percentage as from data analysis) • Too complicated (selected V0s, often V0 finder finds more V0s in the same event) • Event without V0s (“empty”) : should they exist or not? • Repetition of “same V0s” in many samples • Background • Not considered – another version developed to take it into account (see next) • V0 finder – cascade finder : mechanical (just click a button) • But can one find V0s by eye? • Some technical problems • Computer crashes (version of root? Graphics?) – no crash on MacOSX ALICE exercise - D. Hatzifotiadou

  12. Various remarks and suggestions • Should implement counter for events analysed • Display event number / sample number separately • Histograms not optimised • Change histogram binning • Need to update automatically • Add histogram facility : ok for single files, not functioning for multiple files • Book-keeping of results • Clicking of buttons required to save results in tables ad histograms • Often children forget – information lost • Have to modify ALICE exercise - D. Hatzifotiadou

  13. GSI version • Developed another version of the exercise • Analyse “visually” a small sample of events (20 instead of 100) • Run analysis program in the background analysing some thousands of events • Invariant mass plots • Fit background and substract • This certainly answers the question asked by many • Is this how you do the analysis in reality (scanning each event by eye)? ALICE exercise - D. Hatzifotiadou

  14. CERN MasterClass - Feedback • Teacher made an evaluation sheet • 20 replies from the pupils • Answers cover the whole spectrum • General impression positive • Enjoyed the day, feel that they learnt a lot • Proposed improvements • Same teacher had participated last year in CERN masterclass with OPAL exercise • He liked the new one (ALICE) better • One of the instructors: it was fun and it was something different • encouraging ALICE exercise - D. Hatzifotiadou

  15. Videoconference • Discussion on QGP and strangeness enhancement • too much at the end of a long day? • Proposed questions to ask (baryon number conservation) – too difficult – dropped • Opted for having the results reported and filling excel sheets “online” • No uploading of documents • Some of the pupils said that they liked the quiz • Some of the organisers question whether the quiz should be done locally • Some expressed the opinion that we should have an ALICE special quiz • The time of the video-conference makes the whole event end too late • Can everything be brought forward? • For CERN masterclass – less important (they have spent the day at CERN) • Some report technical problems, echo, etc. ALICE exercise - D. Hatzifotiadou

  16. Conclusions • “Looking for strange particles with ALICE” • starting point • developed with limited resources • Overall experience positive • Brought new institutes in the game • Generated interest, dialogue and new ideas • People get more involved when they present their experiment • Some technical problems (computer crashes) • Criticism to be taken into account for the future developments ALICE exercise - D. Hatzifotiadou

  17. Future • Revisit the exercise and its aims • Original idea of looking for strangeness enhancement: • Compare data from Pb-Pb collisions and pp collisions at higher energies (Can the event display easily deal with thousands of tracks?) • Smaller data samples • Viewer, histogram facility, calculator : need modifications • Idea of small scale visual analysis combined with larger scale “real” analysis and background fitting and subtraction : interesting, to be investigated • ( time needed ; too complex ?) • In search of manpower ALICE exercise - D. Hatzifotiadou

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