1 / 38

Summary of hadronic tests and benchmarks in ALICE

Summary of hadronic tests and benchmarks in ALICE. Isidro González CERN EP-AIP/Houston Univ. Geant4 workshop 2002 30 - September - 2002. Summary. ALICE interest Proton thin-target benchmark Experimental and simulation set-up Conservation laws Azimuthal distributions

jblackston
Download Presentation

Summary of hadronic tests and benchmarks in ALICE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Summary of hadronic tests and benchmarks in ALICE Isidro González CERN EP-AIP/Houston Univ. Geant4 workshop 2002 30 - September - 2002

  2. Summary • ALICE interest • Proton thin-target benchmark • Experimental and simulation set-up • Conservation laws • Azimuthal distributions • Double differential cross sections • Conclusions • Neutron transmission benchmark • Expermintal and simulation set-up • Flux distribution • Conclusions

  3. ALICE • Low momentum particle is of great concern for central ALICE and the forward muon spectrometer because: • ALICE has a rather open geometry (no calorimetry to absorb particles) • ALICE has a small magnetic field • Low momentum particles appear at the end of hadronic showers • Residual background which limits the performance in central Pb-Pb collisions results from particles "leaking" through the front absorbers and beam-shield. • In the forward direction also the high-energy hadronic collisions are of importance.

  4. Proton Thin TargetExperimental Set-Up

  5. Revision of ALICE Note 2001-41 with Geant4.4.1 (patch 01) Processes used: Transportation Proton Inelastic:G4ProtonInelasticProcess Models: Parameterised: G4L(H)EProtonInelastic Precompound: G4PreCompoundModel Geometry used: Very low cross sections: Thin target is rarely “seen” CPU time expensive One very large material block One interaction always takes place Save CPU time Stopevery particle after the interaction Store its cinematic properties Proton Thin TargetSimulation Set-Up

  6. Systems in the reaction: Target nucleus Incident proton Emitted particles Residual(s): unknown in the parameterised model Conservation Laws: Energy (E) Momentum (P) Charge (Q) Baryon Number (B) Conservation Laws

  7. Conservation Laws in Parameterised Model • The residual(s) is unknown It must be calculated • Assume only one fragment • Residual mass estimation: • Assume B-Q conservation: • We found negative values of Bres and Qres • Assume E-P conservation • Eres and Pres are not correlated  unphysical values for Mres • Aluminum is the worst case

  8. Conservation Laws in the Precompound Model • There were some quantities not conserved in the initial tested versions • Charge and baryon number are now conserved! • Momentum is exactly conserved • Energy conservation: • Is very sensitive to initial target mass estimation  Use G4NucleiProperties • Width can be of the order of a few MeV

  9. y  x z Azimuthal Distributions • j defined in the plane perpendicular to the direction of the incident particle (x) • Known bug in GEANT3 implementation of GHEISHA • Expected to be flat • Plotted for different types of p and nucleons

  10. Azimuthal Distributions • j distributions are correct! However… • Parameterised model: • At 113 & 256MeV: No p is produced • At 597 & 800MeV: • Pions are produced in Aluminium and Iron • (Almost) no p is produced for Lead • Precompound model: • Not able to produce p, they should be produced by some intranuclear model

  11. Now Before Parameterised model:jpions: (p,Al) @ 597 MeV

  12. Now Before Parameterised model:jnucleons: (p,Al) @ 597 MeV

  13. Double differentials • Real comparison with data • We plot • Which model is better?… Difficult to say • GHEISHA is better in the low energy region (E < 10 MeV) • Precompound is better at higher energies(10 MeV < E < 100 MeV) • None of the models reproduce the high energy peak

  14. Double Differentials GHEISHA Precompound

  15. Double Differential Ratio Al @ 113 Precompound GHEISHA

  16. Double Differential Ratio Al @ 256 Precompound GHEISHA

  17. Double Differential Ratio Fe @ 256 Precompound GHEISHA

  18. Double Differential Ratio Fe @ 597 Precompound GHEISHA

  19. Double Differential Ratio Pb @ 597 Precompound GHEISHA

  20. Double Differential Ratio Pb @ 800 Precompound GHEISHA

  21. Conclusions Proton • Several bugs were found in GEANT4 during proton inelastic scattering test development. • Most of them are currently solved. • The parameterised model cannot satisfy the physics we require. • Precompound model agreement with data improved for • Light nuclei • Low incident energies • Low angles • An intranuclear cascade model would be very welcome • May solve the double differentials disagreement • May produce correct distribution of particle flavours

  22. Tiara Facility

  23. Top View Side View Target Views

  24. Simulation Geometry • Block of test shield placed at z > 401 cm • Different test shield material and thickness: • Iron: • 20 cm • 40 cm • Concrete: • 25 cm • 50 cm • 2 incident neutrons energy spectra. Peak at: • 43 MeV • 68 MeV

  25. Volumes to estimate the flux (“track length” method) x = 0, 20 & 40 cm x y 401 cm Simulation Set-up

  26. 43 MeV 68 MeV Experimental Experimental Simulated Simulated Energy Spectrum Simulation(Consistency check)

  27. Simulation Physics • Electromagnetics: for e± and g • Neutron decay • Hadronic elastic and inelastic processes for neutron, proton and alphas • Tabulated (G4) cross-sections for inelastic hadronic scattering • Precompound model is selected for inelastic hadronic scattering • Neutron high precision (E < 20 MeV) code with extra processes: • Fission • Capture • 1 million events simulated for each case

  28. Preliminary Results: 43 MeVTest Shield: Iron – Thickness: 20 cm

  29. Preliminary Results: 68 MeVTest Shield: Iron – Thickness: 20 cm

  30. Preliminary Results: 43 MeVTest Shield: Iron – Thickness: 40 cm

  31. Preliminary Results: 68 MeVTest Shield: Iron – Thickness: 40 cm

  32. Preliminary Results: 43 MeVTest Shield: Concrete – Thickness: 25 cm

  33. Preliminary Results: 68 MeVTest Shield: Concrete – Thickness: 25 cm

  34. Preliminary Results: 43 MeVTest Shield: Concrete – Thickness: 50 cm

  35. Preliminary Results: 68 MeVTest Shield: Concrete – Thickness: 50 cm

  36. Bonner Sphere Geometry • Sensitive volume made of 3He and Kr • Moderator made of Poliethylene • Several moderator sizes considered

  37. Bonner Sphere Simulation • Need to use: • Spheres (rarely used in HEP) • Boolean solids (Cilinder – Sphere) • Bug in tracking with spheres • Already reported • We have not yet tested boolean solids

  38. Conclusions Neutron • The MC peak, compared to the data, is: • narrower • higher • Though the simulation does not match the data: • Iron simulation shows better agreement than Concrete • For concrete 43 MeV seems better than 68 MeV • Higher statistics will come soon • Bonner Sphere detector simulation could not be done with previous GEANT4 releases Note: Linux gcc 2.95 supported compiler used

More Related