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(Low momentum) Hadron-Nucleus interactions in ALICE

(Low momentum) Hadron-Nucleus interactions in ALICE. Marco van Leeuwen, Utrecht University For the ALICE collaboration. LPCC detector simulation workshop 6-7 October 2011. Motivation. Low-momentum hadron production is of interest for ALICE/heavy ion physics. ALICE, PRL 105, 072002.

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(Low momentum) Hadron-Nucleus interactions in ALICE

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  1. (Low momentum) Hadron-Nucleus interactions in ALICE Marco van Leeuwen, Utrecht University For the ALICE collaboration LPCC detector simulation workshop 6-7 October 2011

  2. Motivation Low-momentum hadron production is of interest for ALICE/heavy ion physics ALICE, PRL 105, 072002 ALICE, Quark Matter 2011 Pb+Pb: Radial flow and hadrochemistry p/p ratio: baryon transport in p+p and Pb+Pb (baryon chemical potential)

  3. Hadron-nucleus cross sections • Tracking efficiency depends on hadron-nucleus cross sections • Inelastic interactions: • Track lost after interaction • Elastic interactions: • Track deflected; losses depend on angle+cuts • Low momentum cross sections: non-trivial momentum, charge dependence

  4. Inelastic cross sections and efficiency GEANT3 cross section Fraction of particlessuffering inelastic collision at R<80 cm NB: anti-protons off scale In ALICE: 100 mb for x-Si corresponds to ~1% loss (depends on material budget) How well do we know the cross sections?

  5. x-p cross sections Data: PDG • Proton targets: • Lots of data available (PDG) • Elastic and total cross section • GEANT3 cross section accurate

  6. x-d cross sections Data: PDG p: Resonant peak underestimated K: Cross sections overestimated p: cross section too large in GEANT3 • Deuteron targets • Smallest nucleus • Lots of data (PDG, total xsec only) NB: GEANT3(GHEISHA) interpolates from p to Al

  7. p-A cross sections Data: A.S. Clough et al, Nucl Phys B76, 15F.Binon et al Nucl Phys B17. 168, D. Ashery et al PRC23, 2173, A Caroll, PRC 14, 635 GEANT4: v9.5b1 Small charge dependence at low p for C, no dependence for Al Not much elastic data GEANT4: good agreement GEANT3: reasonable agreement

  8. K-A cross sections Data: D.V. Bugg et al, Phys Rev 168, 1466, E. Friedmann et al, PRC 55,1304 Not much data GEANT3: Rise of K- at low p too strong (see K-d) GEANT4: better agreement with data. CHIPS better than FTFP

  9. p-A cross sections Data: Bendiscioli and Kharzeev, Riv.Nuovo Cim.17N6, 1-142 GEANT3: cross section too large by factor 1.5 or so (500-1000 mb) GEANT4 (2 phys lists), FLUKA better ALICE practice (so far): use GEANT3 + GEANT/FLUKA correction

  10. p-A data: R.F. Carlson, Atomic Data and Nuclear Data Tables 63 (1996) σ σ σ Good agreement between data and GEANT3, 4

  11. Conclusion • Hadron-p cross sections well-tuned in GEANT3 • GEANT3: some disagreements for hadron-A • Largest differences for anti-p, K-(affect results at 5-10% level) • Solution until now: use FLUKA-based correction for anti-p • GEANT4 • Improvements for all particles • Largest effect: anti-p • Note: non-trivial A-dependence for pions (d to C); not investigated in detail

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