CHIPS approximation of proton- nuclear Coulomb scattering Mikhail Kosov, 12 th Geant4 Workshop (GB, Sept. 2007)

CHIPS approximation of proton-nuclear Coulomb scattering

Mikhail Kosov, 12th Geant4 Workshop (GB, Sept. 2007)

M.Kosov. CHIPS G4QElastic G4.9.0 2September 12-20, 2007

Typical features of Elastic scattering The final state for electromagnetic and

hadronic scattering is the same, so they interfere on the amplitude level.

Nobody can separate the EM and Hadronic scattering, but the measured “EM” part (probably a “EM/H interference” part) can be approximated as an independent discrete process (with a correction for leptons: e, m)

The low t electromagnetic part can be still simulated by a continuous process


CHIPS (w Coulomb)CHIPS (hadronic)SAID (G4Lpp)G4LElastic (LHEP)


Fit (w Coulomb)8.2 (simulation)G4HadronElastic(8.2p2)G4LElastic (8.2)

nucleargloria


Approximation of “Coulomb scattering”

t

e

dt

d tb

q

e

dq

d bq

2

-t = q2

Infinite differential cross-section has a finite integral

a) at high energy it is only a few mb

b) at low energy it can be barns

c) Below Coulomb threshold it is pure electromagnetic


Fit (w Coulomb)8.2 (simulation)G4HadronElastic(8.2p2)G4LElastic (no 3He)

S-wave at low energiesAdditional t-cut

Dominance of Coulomb

nucleargloria





QE

?


QEQE


Increased QE

Stops at 900 (CM)Continues to 1800


QEQE



Quasi-ElasticQE



QE


QE


CHIPS Glauber calculation

Lack of data

Only QEQE

QE



The same fit can be done for pions

There is a fundamental difference between the pion and the muon elastic scatteringMuons do not have the hadronic scattering partMuons do not have the EM/H interference partMuons do not have screening in the interactions

Data for pion and for muon Multiple Scattering should be found and compared

The discrete and continuous processes must be consistent, otherwise the Stopping Ranges for hadrons can be spoiled


CHIPSG4QElasticCoherent Elastic


CHIPSG4QElastic


Conclusion

If the Electromagnetic group is ready for the consistent improvement of “Multiple Scattering”, CHIPS can provide a discrete process G4QEMElastic for pions & protons

At high energies the cross-section is order of magnitude smaller than the hadronic part

At low energy the EM cross-section is huge and the small stepping should be avoided

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CHIPS approximation of proton- nuclear Coulomb scattering Mikhail Kosov, 12 th Geant4 Workshop (GB, Sept. 2007)