Branching Ratios and Particle Decay Modes

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| Geant 3.15  |               GEANT User's Guide              | CONS310  ##
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Author(s) : G.Patrick                                  Submitted: 23.01.84
Origin    : R.Brun,G.N.Patrick                           Revised: 14.04.92
                                  

            +------------------------------------------------+
            | CALL GSDK (IPART,BRATIO,MODE) |
            +------------------------------------------------+
                                  

GSDK stores the branching ratios and partial decay modes for two and three body particle decays into the data structure JPART.

IPART

GEANT particle number

BRATIO(6)

Up to six branching ratios (%)

MODE(6)

Up to six partial decay modes

The decay modes should be coded into the array MODE such that:

4 2 MODE(I) = N3*10 +N2*10 +N1 for I=1,...,6

where,

N1=

GEANT particle number for decay product 1

N2=

GEANT particle number for decay product 2

N3=

GEANT particle number for decay product 3 (if any)

It is important to note the following:

1. Prior to calling GSDK, all parent and secondary particles should have been defined by a previous call to GSPART.
2. If less than six decay modes are defined the remaining elements of BRATIO and MODE must be preset to zero.

For a given particle, IPART, the decay parameters are stored into the JPART data structure as follows:

JPA

= LQ(JPART-IPART) pointer to particle IPART

JDK1

= LQ(JPA-1) pointer to branching ratio banks

JDK2

= LQ(JPA-2) pointer to decay mode banks

BR(I)

= Q(JDK1+I) Ith. branching ratio

MODE(I)

= IQ(JDK2+I) Ith. decay mode, where I=1,...,6.

When an unstable particle decays during the tracking, the routine GDECAY is called. If the decay modes and branching ratios hav been stored by GSDK, then GDECAY generates the decay products in the 2 or 3 body phase space. For any other particle the user routine GUDCAY is called, where the user is free to code special decay modes and branching ratios. All data taken from Aguilar Benitez [bib-AGUI].

      Parent Particle(s)              Decay                 Branching Ratio (%)
    ------------------------------------------------------------------------------
        +    -
      mu , mu                   enunu                                100.00
        0
      pi                        gammag+m-a                           98.802
                                gammae e                              1.198
        +  -
      pi pi                     munu                                 100.00
       0
      K L                       pienu                                 38.70
                                pimunu                                27.10
                                  0  0  0
                                pi pi pi                              21.50
                                  +  -  0
                                pi pi pi                              12.39
       +   -
      K , K                     munu0                                 63.51
                                pipi                                  21.17
                                    +  -
                                pipi pi                                5.59
                                     0
                                enupi                                  4.82
                                      0
                                munupi                                 3.18
                                    0  0
                                pipi pi                                1.73
       0                          +  -
      K                         pi pi                                 68.61
       s                          0  0
                                pi pi                                 31.39
      eta                       gammagamma                            39.00
                                  0  0  0
                                pi pi pi                              31.80
                                  +  -  0
                                pi+pi-pi                              23.70
                                pi pi gamma                            4.91
                                 + -
                                e e gamma                              0.50
                                  0
                                pi gammagamma                          0.10
                                   -
      Lambda                    ppi                                   64.20
                                   0
                                npi                                   35.80
        +    -
      mu , mu                   enunu                                100.00
        +                          0
      sum                       ppi                                   51.64
                                   +
                                npi                                   48.36
        0
      sum                       Lambdagamma                          100.00
        -                          -
      sum                       npi                                  100.00
        0                               0
      Xi                        Lambdapi                             100.00
        -                               -
      Xi                        Lambdapi                             100.00
    ------------------------------------------------------------------------------

      Parent Particle(s)              Decay                 Branching Ratio (%)
    ------------------------------------------------------------------------------
           -                           -
      Omega                     LambdaK                               68.60
                                  0  -
                                Xi pi                                 23.40
                                  -  0
                                Xi pi                                  8.00
                                   +
      Lambda                    ppi                                   64.20
                                   0
                                npi                                   35.80
        #  -                       0
      Sigma                     ppi-                                  51.64
                                npi                                   48.36
           0
      Sigma                     Lambdagamma                          100.00
           +                       +
      Sigma                     npi                                  100.00
        0                               0
      Xi                        Lambdapi                             100.00
        +                               +
      Xi                        Lambdapi                             100.00
           +                           +
      Omega                     La0bd+K                               68.60
                                Xi pi                                 23.40
                                  +  0
                                Xi pi                                  8.00
    ------------------------------------------------------------------------------