Stopping Particles in Geant4: Overview and Remarks for Development Julia Yarba Fermilab 16th Geant4 Collaboration Workshop 09/19/2011 1

Outline Motivation: Comparison vs exp.data and review of the current status of simulation is the best basis for further development plans Models Comparison to data and remarks: – antiproton –  – K - Some remarks on   Julia Yarba, FNAL – 09/19/2011 2

Stopping Models “Traditional” (originates in Gheisha): – Very simplistic approach – Not much development over years – Early attempts to implement “alternatives” for pi- and K- seem abandoned and don’t give any good results (part of) CHIPS: – Active development in recent times – More realistic results, although far from perfect – VERY slow (factor up to ~300 in CPU vs “traditional”) – Tied to the whole CHIPS code - usage inconvenience Recent developments in FTF ? Julia Yarba, FNAL – 09/19/2011 3

Antiproton Conclusions and suggestions are limited by the validation constrains, the ONLY available data for pbar on H CHIPS (out of the box) is much more realistic than “traditional” but far from perfection (see next slide) – Some say it’s a matter of “tuning” – For development: can we make “tuned” version a default ? Both models are very “stable” from version to version – no development at all ? Newly added simulation of antibaryons in FTF – Untested because interface is not publicly available – Question: is it modular, or does it drag along the whole FTF ? – For development: can we make the interface available ? Julia Yarba, FNAL – 09/19/2011 4

Antiproton (cont.) Data Sets: C.Amsler, Rev.Mod.Phys.70,1293(1998) and reference materials Julia Yarba, FNAL – 09/19/ This “makes sense” but NOT agreement Other data sets ? Comparison to FTF will be interesting Speed and convenience of use are also important Results for G4.9.5.b01

Pion- Conclusions driven by validation vs available data, but so far not much attempt to look beyond that (“common sense” basis) CHIPS (out of the box) give good results for heavier targets (see next slide) – For development: can we improve for lighter targets ? Some variations (not always good) in recent times; most recent version(s) return to “normal”; also, some more improvement for heavier targets (details later) Julia Yarba, FNAL – 09/19/2011 6

Pion- (cont.) Data Sets: R.Madey et al.,Phys.Rev.C25,3050(1982) Julia Yarba, FNAL – 09/19/ Any plan to improve CHIPS for lighter targets ? Other data ? Again, speed and convenience of use are important

Pion- (cont.) Julia Yarba, FNAL – 09/19/ Definitely improvement

Kaon- Some exp.data for K- on H recently extracted from papers – “Decay” modes and BR’s – Energy spectra for secondary pi0’s – (I think) More data for K- on H are there but need to be reviewed “Traditional” code is a crude approximation CHIPS gives more sensible results but is far from good – For development: review the BR’s ? – For development: review how kinematics of secondary is modeled ? Look at other reactions/observables ? (I have a few very preliminary plots for heavier targets but more work is needed) Julia Yarba, FNAL – 09/19/2011 9

Kaon- Data Sets: K.Larson et al., Phys.Rev.D47,799(1993) Julia Yarba, FNAL – 09/19/ B(K - p->   )=6.7%; B(K - p->     )=27.5% From Nucl.Phys.B209,16(1982): B(K - p->  )=0.35%

Kaon- Data Sets: K.Larson et al., Phys.Rev.D47,799(1993) Julia Yarba, FNAL – 09/19/   

Muon- (general remarks) Plenty of exp.data (Still) Plans for inclusion in tests “Traditional” and CHIPS models “Traditional” is default in all Physics Lists “Traditional also includes G4MuMinusCaptureCascade class but it’s unclear if it’s tested/used Possible interest from FNAL scientific community: separate implementation of contributing processes (i.e. code development) G4/FNAL group is would like to shape this part of validation activity for overlap/benefit with FNAL scientific program (discussion in progress) Julia Yarba, FNAL – 09/19/

Summary Development plans can benefit from validation feedback For stopping hadrons CHIPS appears to be more realistic, but needs serious improvements needed in both physics aspects (mult., BR’s, kinematics of secondary) and the code infrastructure (modularity) For stopping muons, the question remains open – perhaps, more can invested in “traditional” code (val. coming) Development of interface to stopping physics in FTF will be very useful Julia Yarba, FNAL – 09/19/