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Tapan Nayak For the ALICE Collaboration

Proton-proton physics in ALICE. Tapan Nayak For the ALICE Collaboration. p. p. Motivation. Rich pp-physics program at unexplored energies: Soft physics (low p T ) program First time: above the cosmic “knee” Min. bias events, constraints for under-lying event

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Tapan Nayak For the ALICE Collaboration

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  1. Proton-proton physics in ALICE Tapan Nayak For the ALICE Collaboration QM06: pp physics in ALICE

  2. p p Motivation • Rich pp-physics program at unexplored energies: • Soft physics (low pT) program • First time: above the cosmic “knee” • Min. bias events, constraints for under-lying event • Multi-parton interactions (high multiplicity pp events) • Interplay of non-perturbativevs.perturbative physics • New x-Bjorken region (10-3-10-5) • Heavy Flavour • mini-jets and jets • Hadronization processes • Fragmentation processes • Collision energy dependence all above • Potential for new physics • 2.pp collisions provide basis for understanding heavy-ion collisions QM06: pp physics in ALICE

  3. Low Luminosity (pp) Low b (Ions) CERN - Large Hadron Collider (LHC) • pp @ 14TeV • Luminosity (Lmax):1034cm-2 sec-1 • Lmax for ALICE: 3x1030cm-2 sec-1(200 kHz rate limit as TPC drift time is 90msec) • LHC Schedule: • Aug 2007: Collider Closure • Nov 2007: FIRST collisions: pp @ 900 GeV • Dec 2007: pp @ 2200 GeV(?) • 2008: pp @ 14TeV at low luminosity (~6x1026 cm-2sec-1) • LOW LUMINOSITY runs are ideal for ALICE QM06: pp physics in ALICE

  4. ACORDE cosmics FMD ch multiplicity V0, T0 Trigger + multiplicity HMPID PID (RICH) @ high pt TOF PID TRD Electron ID PMD g multiplicity TPC Tracking, dEdx ITS Low pt tracking Vertexing MUON m-pairs PHOS g,p0 ALICE layout EM Calorimeter (future) QM06: pp physics in ALICE

  5. Central Barrel (-0.9 < h < 0.9) • tracking, PID (ITS, TPC, TRD, TOF) • single arm RICH • single arm EM cal (PHOS) • Multiplicity • charged (barrel+FMD): (-5.4 < h < 3) • photons in PMD (-2.3 < h < -3.7) • Forward muon arm (2.4 < h < 4.0) • absorber, dipole magnet • tracking and trigger chambers • Trigger, timing, luminosity: • ZDC, V0, T0, CRT • EM Calorimeter (future) (charged particles) Unique features of ALICE • Soft (100MeV) to hard (>100GeV) physics • low pT cut-off (~100 MeV): • => Low magnetic field: 0.2-0.5 T & Low material budget: 7% • excellent tracking and PID • dedicated di-electrons and di-muons • high resolution calorimeter for direct photons QM06: pp physics in ALICE

  6. Offline Framework 1. Event Generators 2. Simulation 3. Reconstruction 4. Analysis FLUKA G3 G4 ISAJET Virtual MC AliEn + LCG AliRoot AliReconstruction HIJING AliSimulation EVGEN MEVSIM • Physics Data Challenge (2006) • 100M pp events being produced using GRID • 10M already produced • Configuration: • min. bias events with Pythia • addition of special physics events • Most of the Analysis framework exists STEER PYTHIA6 PDF PMD EMCAL TRD ITS PHOS TOF ZDC RICH HBTP STRUCT CRT START FMD MUON TPC RALICE ESD HBTAN JETAN Analysis ROOT QM06: pp physics in ALICE

  7. central Pb–Pb pp DpT/pT (%) pp central Pb–Pb DpT/pT (%) For 2 < pT < 100GeV: 1-5% For pT < 2GeV: 0.5-0.8% pT (GeV/c) pT (GeV/c) Detector Performance Momentum Resolution QM06: pp physics in ALICE

  8. Topological identification (K0, K+, K-, L): up to ~ 10 GeV Leptons (e, m), photons, p0, h: • electrons in TRD: p > 1 GeV, • muons: p > 5 GeV • p0 in PHOS: 1 < p < 80 GeV separation @ 3s separation @ 2s Particle Identification Stable hadrons (p, K, p): • 100MeV<p<5 GeV (few 10GeV) QM06: pp physics in ALICE

  9. Pseudo-rapidity distributions pp @ 14TeV Min bias ALICE UA5, ZPC 33 (1986), CDF, PRD 41 (1990) Reconstruction with TPC dN/dh dN/dh All charged particles h h Reconstruction with SPD dN/dh PDC06 data:400K events (corrections)100K events (analysis)Different event sample! h All Charged particles Good agreement in central region QM06: pp physics in ALICE

  10. Multiplicity distributions ALICE Probability for an event to have larger than Nch multiplicity (|h|<0.9) E735: Phys. Lett. B 435 (1998) 453 Walker PRD 69 (2004) 14TeV 5.5TeV Multiplicity reach 2.2TeV 546GeV 1800GeV <N1>=31 900GeV 900GeV Multiplicity reaching to >10 times the mean value – interesting for multi-parton interactions, event structure, HBT, multiplicity correlations, rapidity gaps …. 200GeV <N1>=20 Nch N/<N1> High multiplicity trigger (threshold on # of SPC chips hit >40 >60 >80 Full phase space Violation of KNO scaling: Multiplicity distributions expected to “scale” as per to single parton-parton interactions. Deviations attributed to multiparton interactions, jet-minijets. QM06: pp physics in ALICE

  11. pp @ 14TeV Min bias CDF: PRL 61, 1819 (1988) ALICE pT (GeV/c) Charged particles pT reach • With 100k events, up to 10 GeV/c • With 100M events, up to 50 GeV/c pT distributions QM06: pp physics in ALICE

  12. CDF: PRD 65,72005(2002) <pT> Nch E735 Fermilab Protons • <pT> vs. multiplicity shows different behavior for different identified particles. • In ALICE: inclusive and identified particles will be used in the study with low to high pT range Kaons <pT> Pions Nch Mean pTvs. Multiplicity ALICE pp @ 14TeV CDF data pT>0.4GeV/c All pT QM06: pp physics in ALICE

  13. L reconstruction pp@14TeV (p,p-) K0s (L+L)/K0s pp @ 14TeV Strangeness: Baryons, Mesons • Baryon production mechanism • Constraints for underlying events • PYTHIA for min. bias and underlying events (with different settings) give different results. • Flavour dependence of the ratio QM06: pp physics in ALICE

  14. String Junction Standard case q q q This is suppressed  exp (-1/2 y) Proton – antiproton asymmetry in % H1: Δη ~ 7 – 9.61 ← η Baryon # transfer in rapidity Rossi & Veneziano: gluons carry baryon number resulting in substantial baryon production in central rapidity region. (Kopeliovitch & Zakharov Z. Phys. C43 (1989) 241). Expectation at LHC: • ALICE advantages: • Large rapidity gap • Asymmetry vs. multiplicity • With protons, L, X, W ….. • Statistics: • 108 events (one month): • 109p, 107 p, 106 L, • 104X, 103W QM06: pp physics in ALICE

  15. Heavy flavour in pp • Motivation: • small xBJ physics • pQCD in a new energy domain • HQ fragmentation functions • gluon shadowing • quarkonia production mechanism, charm and beauty cross sections • ALICE advantages: • combination of electronic, muonic and hadronic channels: • Central barrel (-0.9<h<0.9) and Muon arm (2.5<h<4) • coverage close to pT~0 for quarkonia and open charm • high precision vertexing • Physics analysis: • hadronic decays: D0K p, D+-Kpp, DsK K*, Dsfp, … • Leptonic decays: • B l (e or m) + anything. • Inv. mass of lepton pairs:BB, DD, J/Y, Y’,  family, B J/Y + anything. • BB  mmm (J/Ym) • e-m correlations. • W+-  l+-n, Z0l+l-. • J/y polarization QM06: pp physics in ALICE

  16. pp @ 14TeV Pb+Pb at 5.5TeV up to 11–14 GeV/c with 70M evts rec. track e Primary Vertex B 109 events d0 X D0 Kp (ct = 124mm) B  e + X QM06: pp physics in ALICE

  17. m+m- Minv e+e- Minv m+m- Minv Quarkonia Muonic channel Electronic channel • Statistics: in one year of data (109 min bias events): • 8.5x106 J/Y and 6.5x103U in the muonic chanel • 5x105 J/Y in the electronic channel QM06: pp physics in ALICE

  18. hadrons Parton distribution functions Hard scattering c.s. Fragmentation function c a b d hadrons leading particle High pT and jets in pp • Motivation: • test of perturbative QCD predictions • Jet fragmentation properties • understanding the hadronization processes • Jet rates: • pT>100GeV: • Physics analysis: • Jet trigger (for >100GeV) • high pT spectra • Jet reconstruction & jet structure observables: • jT , fragmentation function, jet-shape • di-hadron correlations • g-Jet correlations QM06: pp physics in ALICE

  19. 2-Jet in pp Displays for pT threshold 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 QM06: pp physics in ALICE

  20. Direct photons in pp Dominant processes (pQCD contributions) g + q → γ+ q (Compton) q + q → γ + g (Annihilation) R PHOS • Motivation: • thermal photon spectrum • QCD tests, PDF determination • pp: initial stages • Physics analysis: • thermal photon identification • prompt photons: isolation method • photon HBT • Photon tagged jets (g-jet correl.) • Eg = Ejet (g energy provides independent measure of jet energy) • emitted in opposite direction • ALICE can measure photon tagged jets with • Eg > 20 GeV (PHOS + TPC) • Eg > 40 GeV (EMCAL+TPC) QM06: pp physics in ALICE

  21. Summary • ALICE advantages at LHC: • Low pT, excellent PID & vertex; and reconstruction of high pT jets • Ideal to study min. bias & underlying events at low luminosity • Unique physics with one year data: • Global event characteristics: (inclusive and identified) • h distributions • multiplicity distributions, fluctuations/correlations • pT distributions • Particle ratios, strangeness • Baryon transport, rapidity gap • <pT> vs. multiplicity • Heavy quarks (total c and b cross sections) • high pT spectra, jets • direct photons • ……… • pp study provides important benchmark for all heavy-ions topics • ALICE pp program is complementary to dedicated pp experiments @ LHC QM06: pp physics in ALICE

  22. TPC sector test: Cosmic rays Single event display of one pp event QM06: pp physics in ALICE

  23. The ALICE Collaboration Thanks to many of the colleagues who have helped to put the talk together - ALICE Physics working groups and in particular to ALICE First Physics working group, • Main references: • ALICE PPR – Vol-1 • 2. ALICE PPR – Vol-2 QM06: pp physics in ALICE

  24. Luminosity is related to the rate & cross section: • L in pp measured by: V0, T0, ITS and Luminometers • Reduction in luminosity at ALICE IP from LHC max: 1034 • Final L from theoretical c.s. and TOTEM measurements • Expected uncertainty in estimated L : ~5% Compilation by R.M. Godbole et al. QGSM model predictions: A.B. Kaidalov Sqrt(S) TeV s (total) s (el) s (SD) <Nch> (ND) <Nch> (inel) dN/dh (h=0) (ND) dN/dh (h=0) (inel) 0.9 66 12.5 6.3 35 32 3.4 3 Total cross section 2.2 75 15 7.6 45 41 4 3.5 5.5 89 19 9.5 60 55 4.9 4.3 14 103 26 13 77 71 5.9 5.0 Luminosity & cross sections QM06: pp physics in ALICE

  25. LHC Beam Parameters QM06: pp physics in ALICE

  26. QM06: pp physics in ALICE

  27. B factories Tevatron LHC QM06: pp physics in ALICE

  28. 108 106 104 102 100 Q2 (GeV2) 100 GeV J/ψ QM06: pp physics in ALICE

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