1. Comparison HARP data with GEANT4 and MARS Simulations NUFACT06, UC Irvine 28 August 2006 Stephen Brooks 1, Paul Soler 2, Kenny Walaron 2 1 Rutherford Appleton Laboratory 2 University of Glasgow/RAL

2. 2 NUFACT06, UC Irvine 28 August, 2006 Motivation o Determination of proton energy at a Neutrino Factory needs simulations of protons on different targets o Mars 14 predicts broad spectrum above 5 GeV/c Zisman, ISS Accelerator WG summary  – : 6 – 11 GeV  + : 9 – 19 GeV We adopted 10 ± 5 GeV as representative range

3. 3 NUFACT06, UC Irvine 28 August, 2006 Motivation o Need to validate hadronic models for neutrino target simulations o There were comparisons of Geant4 and Mars15 target simulations reported at NUFACT05 (Brooks, Walaron) o Problem: no good agreement amongst different hadronic models of Geant4 and Mars. Geant4 QGSP model Pion yields passing through front-end of Neutrino Factory

4. 4 NUFACT06, UC Irvine 28 August, 2006 Motivation o Geant 4 secondaries after protons impinging on target o Fate of Geant 4 secondaries at a Neutrino Factory front-end

5. 5 NUFACT06, UC Irvine 28 August, 2006 Geant4/MARS Hadronic Models o Geant4 hadronic models: (see G4 Physics Reference Manual) R. Raja talk plenary –LHEP: GHEISHA parametrization used in GEANT3, normally valid E<25 GeV –LHEP-BERT: E 3 GeV GHEISHA –LHEP-BIC: E 3 GeV GHEISHA –QGSP: E 25 GeV quark-gluon string pre-compound –QGSP-BERT: E 25 GeV quark-gluon string pre-compound model –QGSP-BIC: E 25 GeV quark-gluon string model –QGSC: E 25 GeV quark-gluon string with CHIPS (Chiral invariant Phase Space) model o MARS 15 hadronic model: –“Cascade-Exciton Model” for E<5 GeV – Inclusive hadron production parametrisation for E>5 GeV o Need to establish validity of models by contrasting to HARP data

6. 6 NUFACT06, UC Irvine 28 August, 2006 HARP Experiment o HARP: investigation of pion and kaon cross-sections from protons impinging on a variety of targets between 1.5-15 GeV/c Described D Schmitz, S Borgi talks

7. 7 NUFACT06, UC Irvine 28 August, 2006 HARP Data o HARP results so far: –Aluminium target (5%  I ) at 12.9 GeV/c (K2K target) in forward direction: published Nucl.Phys.B732:1-45,2006 –Beryllium target at 8.9 GeV/c (MiniBooNE) and carbon at 12 GeV/c in forward direction: see David Schmitz’s talk in plenary session –Large angle tantalum target at 3, 5, 8 GeV/c: see Silvia Borghi’s talk in WG3 o I will not describe analysis. Refer to papers and other talks. o This talk is comparison of HARP 12.9 GeV/c cross-section data to cross- section predictions from Geant4 and MARS models. HARP 5%  I 12.9 GeV data

8. 8 NUFACT06, UC Irvine 28 August, 2006 HARP Data o Differential cross-section definition used in HARP analysis: –Number protons: –Target nuclei per unit area: –Number of observed particles of type  ’ in momentum bin p i’ and angle  j’ : –Inverse of correction matrix that corrects for detector efficiency and resolution: o For simulated data, we only need: (MC truth makes effic. matrix unitary) –Monte Carlo samples: 5x10 6 pot at 5%  I and 5x10 6 pot at 1%  I –Linear extrapolation to 0%  I corrects for re-absorption in target.

9. 9 NUFACT06, UC Irvine 28 August, 2006 HARP Data o Differential cross-sections: Sangford-Wang HARP

10. 10 NUFACT06, UC Irvine 28 August, 2006 Comparison G4 with HARP  Comparison Geant4 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad 30-60 mrad60-90 mrad Deficit HARP 1.0-2.0 GeV/c

11. 11 NUFACT06, UC Irvine 28 August, 2006 Comparison G4 with HARP 90-120 mrad120-150 mradDeficit HARP 1.0-1.5 GeV/c  Comparison Geant4 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad

12. 12 NUFACT06, UC Irvine 28 August, 2006 Comparison G4 with HARP 150-180 mrad180-210 mradDeficit HARP ~1.0 GeV/c  Comparison Geant4 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad

13. 13 NUFACT06, UC Irvine 28 August, 2006 Comparison G4 with HARP Deficit HARP 1.0-2.0 GeV/c Total cross-section vs momentumTotal cross-section vs angle  Comparison Geant4 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad

14. 14 NUFACT06, UC Irvine 28 August, 2006 Comparison G4 with HARP o However, can tune parameters in Geant 4 (e.g. tune of QGSC model) V. Ivantchenko

15. 15 NUFACT06, UC Irvine 28 August, 2006 Comparison MARS 15 with HARP Deficit MARS 1.0-2.0 GeV/c  Comparison MARS 15 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad

16. 16 NUFACT06, UC Irvine 28 August, 2006 Comparison MARS 15 with HARP  Comparison MARS 15 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad Good agreement

17. 17 NUFACT06, UC Irvine 28 August, 2006 Comparison MARS 15 with HARP  Comparison MARS 15 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad Good agreement

18. 18 NUFACT06, UC Irvine 28 August, 2006 Comparison MARS 15 with HARP  Comparison MARS 15 with HARP 12.9 GeV/c Aluminium data (5%  I ) as a function of angle o Forward direction: 30-210 mrad Deficit HARP 1.0-2.0 GeV/c Total cross-section vs momentumTotal cross-section vs angle

19. 19 NUFACT06, UC Irvine 28 August, 2006 Comparison MARS/Geant4 with HARP o MARS differences with HARP data smaller (<40%) than with G4-QGSC (~100% at low momentum, low angle) QGSC MARS MC-HARP HARP

20. 20 NUFACT06, UC Irvine 28 August, 2006 Outlook o We have compared HARP data to GEANT4 and MARS15 o Deficit of HARP data with respect to Geant 4 and MARS simulations between 1.0-2.0 GeV/c for low angle o MARS simulation has better agreement than best GEANT4 simulation (QGSC) o However, can tune parameters of G4-QGSC to obtain better agreement. o Still need to include FLUKA as another model for comparison o As HARP data becomes available, there will be a comprehensive programme of comparison of MC models with all data and to phenomenological models