Starting_the_Stack

 The framework of UMC is such that the user may "start" an event at any desired point - e.g. with a charged Kaon entering the degrader, or with a particular rare K decay mode. To do so, the user simply sets the stack variables to values corresponding to the desired initial situation. This is done in the routine USTART (see KAON_BEAM). Events can also be started using USTACK dumps from previous runs of the program (see documentation of WRTSTK and RDSTK).

Stack_Variables

The variables in USTACK are:

DOUBLE PRECISION EU INTEGER NPU,IQU,ITU,IAUX,IRU REAL XU,YU,ZU,DNEARU,UU,VU,WU,TNS COMMON/USTACK/EU(30),XU(30),YU(30),ZU(30),DNEARU(30),UU(30), 1 VU(30),WU(30),TNS(30),IQU(30),ITU(30),IAUX(30),IRU(30),NPU

Name(s) Function

NPU The number of particles on the USTACK. Note that NPU points to the top particle on the stack (the one being tracked).

EU Total energy of the particle in MeV (DOUBLE PRECISION )

XU,YU,ZU The X,Y,Z positions in centimeters.

DNEARU *The distance to the nearest boundary in cm.

UU,VU,WU The directional cosines of the particle.

IQU The integer charge of the particle.

ITU Particle type index. ( See table below.)

IAUX Auxillary type index. ( " " " )

ITU...IAUX......Type

1......0......Photons

1......1......Neutrino

2......x......Electron

3......x......Muon

4......x......Neutral Pion

5......x......Charged Pion

6......0......Charged Kaons IQU=+/- 1

7......x......K Long

8......x......K short

9......x......Proton

10......x......Neutron

11......x......Familon ( Mass= FAMASS ) x ==> don't care

Note the values of ITU indicate a particle's mass while IAUX values are used to distinguish between different particles of the same mass.

IRU Region index

NPU Stack pointer, equal to number of particles on the stack.

TNS Time in nsec.