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Manuscript Title: A GEANT extension for polarized neutron-proton scattering.
Authors: H.W. den Bok, Z. Papandreou, Th.S. Bauer, E. Voutier, M.E. Brandan
Program title: SAIDINTF
Catalogue identifier: ACLS_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 74(1993)375
Programming language: Fortran.
Computer: DECstation 5500.
Operating system: DEC-ULTRIX V4.2(rev.47), DomainOS rel. 10.3(bsd4.
RAM: 400K words
Word size: 32
Keywords: Particle physics, Elementary, Detector design, Nuclear physics, General experiment, Monte carlo, Polarized elastic Neutron-proton Scattering.
Classification: 11.7, 17.4.

External routines: Other programs necessary for saidintf.
-Function RNDM(DUMMY) generates random numbers uniformly distributed between 0 and 1
-GEANT version 3.14, CERN package for simulation and visualisation of detectors and detector response.

Nature of problem:
The GEANT package has proven to be very useful in simulating the behaviour of a neutron polarimeter. However, GEANT lacks the treatment of polarization in elastic nucleon-nucleon scattering channels. Therefore, polarization was introduced for elastic neutron-proton scattering processes which are treated within the core of the GEANT hadronic interaction software.

Solution method:
Realistic differential cross sections and analyzing powers are introduced in the Monte Carlo generation of the final state in polarized neutron-proton scattering. Apart from the generation of asymmetries caused by the analyzing power of the scattering, realistic angular distributions of the scattered particles are introduced as well. The analyzing powers and differential cross sections are obtained from the SAID phase-shift analysis code.

Polarized neutron-proton scattering is only evaluated if the kinetic energy of the incoming neutron is between 1 and 500 MeV and if the scattering occurs in pure hydrogen (proton target). Only the sideways polarization is treated (px).

Running time:
The software is implemented as a patch in the existing GEANT hadron cascade and is called only under very specific conditions. No significant difference in runtime with respect to the original code is observed.