ZGOUBI USERS' GUIDE - HEP

60 4 DESCRIPTION OF THE AVAILABLE PROCEDURES44€. 3 ¯‡°±4ª w´> w53´4´4SPNTRK: Spin trackingThe keyword SPNTRK permits switching on the spin tracking option. It also permits the attribution of an initial spincomponent to each one of the IMAX particles of the beam, following a distribution that depends on the option index KSO.It must be preceded by PARTICUL for the definition of mass and gyromagnetic factor.KSO = 1 (respectively 2, 3): the IMAX particles of the beam are given a longitudinal (1,0,0) spin component (respectivelytransverse horizontal (0,1,0), vertical (0,0,1)).KSO = 4: initial spin components are entered explicitly for each one of the IMAX particles of the beam.¥KSO = 5: random generation of IMAX initial spin conditions as described in Fig. 8. Given a mean polarization axis (S)defined by its angles and , and a cone of angle A with respect to this axis, the IMAX spins are sorted randomly in aGaussian distributionÈ @@ P>¬« P©and within a cylindrical uniform distribution around the (S) axis. Examples of simple distributions available by this meanare given in Fig. 9.δAZSAP oYT oXFigure 8: Spin distribution as obtained with option KSO = 5.The spins are distributed within an annular strip P ´ (standard deviation) at an angle ´ with respectto the axis of mean polarization (S) defined byand ¥.