Supersymmetry Common Blocks and Routines

The parameters available to the SUSY user are stored in the common block PYMSSM. In general, options are set by the IMSS array, while real valued parameters are set by RMSS. The entries IMSS(0) and RMSS(0) are not used, but are available for compatibility with the C programming language. Note also that most options are only used by PYTHIA's internal SUSY machinery and are ineffective when external spectrum calculations are used, see section .

Purpose:

to give access to parameters that allow the simulation of the MSSM.

IMSS(1) :

(D=0) level of MSSM simulation.

= 0 :

No MSSM simulation.

= 1 :

A general MSSM simulation. The parameters of the model are set by the array RMSS.

= 2 :

An approximate SUGRA simulation using the analytic formulae of [Dre95] to reduce the number of free parameters. In this case, only five input parameters are used. RMSS(1) is the common gaugino mass $m_{1/2}$, RMSS(8) is the common scalar mass $m_0$, RMSS(4) fixes the sign of the higgsino mass $\mu$, RMSS(16) is the common trilinear coupling $A$, and RMSS(5) is $\tan\beta=v_2/v_1$.

= 11 :

Read spectrum from a SUSY Les Houches Accord conformant file. The Logical Unit Number on which the file is opened should be put in IMSS(21). If a decay table should also be read in, the corresponding Unit Number (normally the same as the spectrum file) should be put in IMSS(22). Cross sections are still calculated by PYTHIA, as are decays for those sparticles and higgs bosons for which a decay table is not found on the file.

= 12 :

Invoke a runtime interface to ISASUSY [Bae93] for determining SUSY mass spectrum and mixing parameters. This provides a more precise solution of the renormalization group equations than is offered by the option = 2 above. The interface automatically asks the SUGRA routine (part of ISASUSY) to solve the RGE's for the weak scale mass spectrum and mixing parameters. The mSUGRA input parameters should be given in RMSS as usual, i.e.: RMSS(1) = $m_{1/2}$, RMSS(4) = sign($\mu$), RMSS(5) = $\tan\beta$, RMSS(8) = $m_0$, and RMSS(16)= $A$. As before, we are using the conventions of [Hab85,Gun86a] everywhere. Cross sections and decay widths are still calculated by PYTHIA, using the output provided by ISASUSY. Note that since PYTHIA cannot always be expected to be linked with the ISAJET library, a new dummy routine and a new dummy function have been added. These are SUGRA and VISAJE, located towards the very bottom of the PYTHIA source code. These routines must be removed and PYTHIA recompiled before a proper linking with ISAJET can be achieved. Furthermore, the common block sizes and variable positions accessed in the SUGRA routine have to match those of theISAJET version used, see subsection .

IMSS(2) :

(D=0) treatment of U(1), SU(2), and SU(3) gaugino mass parameters.

= 0 :

The gaugino parameters $M_1, M_2$ and $M_3$ are set by RMSS(1), RMSS(2), and RMSS(3), i.e. there is no forced relation between them.

= 1 :

The gaugino parameters are fixed by the relation $(3/5) \, M_1/\alpha_1 =M_2/\alpha_2=M_3/\alpha_3=X$ and the parameter RMSS(1). If IMSS(1)=2, then RMSS(1) is treated as the common gaugino mass $m_{1/2}$ and RMSS(20) is the GUT scale coupling constant $\alpha_{GUT}$, so that $X=m_{1/2}/\alpha_{GUT}$.

= 2 :

$M_1$ is set by RMSS(1), $M_2$ by RMSS(2) and $M_3 = M_2\alpha_3/\alpha_2$. In such a scenario, the U(1) gaugino mass behaves anomalously.

IMSS(3) :

(D=0) treatment of the gluino mass parameter.

= 0 :

The gluino mass parameter $M_3$ is used to calculate the gluino pole mass with the formulae of [Kol96]. The effects of squark loops can significantly shift the mass.

= 1 :

$M_3$ is the gluino pole mass. The effects of squark loops are assumed to have been included in this value.

IMSS(4) :

(D=1) treatment of the Higgs sector.

= 0 :

The Higgs sector is determined by the approximate formulae of [Car95] and the pseudoscalar mass $M_{\mathrm{A}}$ set by RMSS(19).

= 1 :

The Higgs sector is determined by the exact formulae of [Car95] and the pseudoscalar mass $M_{\mathrm{A}}$ set by RMSS(19). The pole mass for $M_{\mathrm{A}}$ is not the same as the input parameter.

= 2 :

The Higgs sector is fixed by the mixing angle $\alpha$ set by RMSS(18) and the mass values PMAS(I,1), where I=25,35,36, and 37.

IMSS(5) :

(D=0) allows you to set the $\tilde{\mathrm t}$, $\tilde{\mathrm b}$ and $\tilde\tau$ masses and mixing by hand.

= 0 :

no, the program calculates itself.

= 1 :

yes, calculate from given input. The parameters RMSS(26) - RMSS(28) specify the mixing angle (in radians) for the sbottom, stop, and stau. The parameters RMSS(10) - RMSS(14) specify the two stop masses, the one sbottom mass (the other being fixed by the other parameters) and the two stau masses. Note that the masses RMSS(10), RMSS(11) and RMSS(13) correspond to the left-left entries of the diagonalized matrices, while RMSS(12) and RMSS(14) correspond to the right-right entries. Note that these entries need not be ordered in mass.

IMSS(7) :

(D=0) treatment of the scalar masses in an extension of SUGRA models. The presence of additional U(1) symmetries at high energy scales can modify the boundary conditions for the scalar masses at the unification scale.

= 0 :

No additional $D$-terms are included. In SUGRA models, all scalars have the mass $m_0$ at the unification scale.

= 1 :

RMSS(23) - RMSS(25) are the values of $D_X, D_Y$ and $D_S$ at the unification scale in the model of [Mar94]. The boundary conditions for the scalar masses are shifted based on their quantum numbers under the additional U(1) symmetries.

IMSS(8) :

(D=0) treatment of the $\tilde\tau$ mass eigenstates.

= 0 :

The $\tilde\tau$ mass eigenstates are calculated using the parameters
RMSS(13,14,17).

= 1 :

The $\tilde\tau$ mass eigenstates are identical to the interaction eigenstates, so they are treated identically to $\tilde{\mathrm e}$ and $\tilde{\mu}$ .

IMSS(9) :

(D=0) treatment of the right handed squark mass eigenstates for the first two generations.

= 0 :

The $\tilde{\mathrm q}_R$ masses are fixed by RMSS(9). $\tilde{\mathrm d}_R$ and $\tilde{\mathrm u}_R$ are identical except for Electroweak $D$-term contributions.

= 1 :

The masses of $\tilde{\mathrm d}_R$ and $\tilde{\mathrm u}_R$ are fixed by RMSS(9) and RMSS(22) respectively.

IMSS(10) :

(D=0) allowed decays for $\tilde{\chi}_2$.

= 0 :

The second lightest neutralino $\tilde{\chi}_2$ decays with a branching ratio calculated from the MSSM parameters.

= 1 :

$\tilde{\chi}_2$ is forced to decay only to $\tilde{\chi}_1 \gamma$, regardless of the actual branching ratio. This can be used for detailed studies of this particular final state.

IMSS(11) :

(D=0) choice of the lightest superpartner (LSP).

= 0 :

$\tilde{\chi}_1$ is the LSP.

= 1 :

$\tilde{\chi}_1$ is the next to lightest superparter (NLSP) and the gravitino is the LSP. The $\tilde{\chi}_1$ decay length is calculated from the gravitino mass set by RMSS(21) and the $\tilde{\chi}_1$ mass and mixing.

IMSS(21) :

(D=0) Logical Unit Number for SUSY Les Houches Accord spectrum read-in. Only used if IMSS(1)=11.

IMSS(22) :

(D=0) Read-in of SUSY Les Houches Accord decay table.

= 0 :

No decays are read in. The internal PYTHIA machinery is used to calculate decay rates.

> 0 :

Read decays from LHA3 file on unit number IMSS(22). During initialization, decay tables in the file will replace the values calculated by PYTHIA. Particles for which the file does not contain a decay table will thus still have their decays calculated by PYTHIA. In normal usage one would expect IMSS(22) to be equal to IMSS(21), to ensure that the spectrum and decays are consistent with each other, but this is not a strict requirement.

IMSS(23) :

(D=0) writing of MSSM spectrum data.

= 0 :

Don't write out spectrum.

> 0 :

Write out spectrum in LHA3 format (calculated by PYTHIA or otherwise) to file on unit number IMSS(23).

IMSS(24) :

(D=0) writing of MSSM particle decay table.

= 0 :

Don't write out decay table.

> 0 :

Write out decay table in LHA3 format to file on unit number IMSS(24). Not implemented in the code yet. In normal usage one would expect IMSS(24) to be equal to IMSS(23), to ensure that the spectrum and decays are consistent with each other, but this is not a strict requirement.

IMSS(51) :

(D=0) Lepton number violation on/off (LLE type couplings).

= 0 :

All LLE couplings off. LLE decay channels off.

= 1 :

All LLE couplings set to common value given by $10^\texttt{\scriptsize -RMSS(51)}$.

= 2 :

LLE couplings set to generation-hierarchical `natural' values with common normalization RMSS(51) (see section ).

= 3 :

All LLE couplings set to zero, but LLE decay channels not switched off. Non-zero couplings should be entered individually into the array RVLAM(I,J,K). Because of the antisymmetry in I and J, only entries with I$<$J need be entered.

IMSS(52) :

(D=0) Lepton number violation on/off (LQD type couplings).

= 0 :

All LQD couplings off. LQD decay channels off.

= 1 :

All LQD couplings set to common value given by $10^\texttt{\scriptsize -RMSS(52)}$.

= 2 :

LQD couplings set to generation-hierarchical `natural' values with common normalization RMSS(52) (see section ).

= 3 :

All LQD couplings set to zero, but LQD decay channels not switched off. Non-zero couplings should be entered individually into the array RVLAMP(I,J,K).

IMSS(53) :

(D=0) Baryon number violation on/off

= 0 :

All UDD couplings off. UDD decay channels off.

= 1 :

All UDD couplings set to common value given by $10^\texttt{\scriptsize -RMSS(53)}$.

= 2 :

UDD couplings set to generation-hierarchical `natural' values with common normalization RMSS(53) (see section ).

= 3 :

All UDD couplings set to zero, but UDD decay channels not switched off. Non-zero couplings should be entered individually into the array RVLAMB(I,J,K). Because of the antisymmetry in J and K, only entries with J$<$K need be entered.

RMSS(1) :

(D=80. GeV) If IMSS(1)=1 $M_1$, then U(1) gaugino mass. If IMSS(1)=2, then the common gaugino mass $m_{1/2}$.

RMSS(2) :

(D=160. GeV) $M_2$, the SU(2) gaugino mass.

RMSS(3) :

(D=500. GeV) $M_3$, the SU(3) (gluino) mass parameter.

RMSS(4) :

(D=800. GeV) $\mu$, the higgsino mass parameter. If IMSS(1)=2, only the sign of $\mu$ is used.

RMSS(5) :

(D=2.) $\tan\beta$, the ratio of Higgs expectation values.

RMSS(6) :

(D=250. GeV) Left slepton mass $M_{\tilde{\ell}_L}$. The sneutrino mass is fixed by a sum rule.

RMSS(7) :

(D=200. GeV) Right slepton mass $M_{\tilde{\ell}_R}$.

RMSS(8) :

(D=800. GeV) Left squark mass $M_{\tilde{\mathrm q}_L}$. If IMSS(1)=2, the common scalar mass $m_0$.

RMSS(9) :

(D=700. GeV) Right squark mass $M_{\tilde{\mathrm q}_R}$. $M_{\tilde{\mathrm d}_R}$ when IMSS(9)=1.

RMSS(10) :

(D=800. GeV) Left squark mass for the third generation $M_{\tilde{\mathrm q}_L}$. When IMSS(5)=1, it is instead the $\tilde{\mathrm t}_2$ mass, and $M_{\tilde{\mathrm q}_L}$ is a derived quantity.

RMSS(11) :

(D=700. GeV) Right sbottom mass $M_{\tilde{\mathrm b}_R}$. When IMSS(5)=1, it is instead the $\tilde{\mathrm b}_1$ mass.

RMSS(12) :

(D=500. GeV) Right stop mass $M_{\tilde{\mathrm t}_R}$ If negative, then it is assumed that $M_{\tilde{\mathrm t}_R}^2 < 0$. When IMSS(5)=1, it is instead the $\tilde{\mathrm t}_1$ mass.

RMSS(13) :

(D=250. GeV) Left stau mass $M_{\tilde\tau _L}$.

RMSS(14) :

(D=200. GeV) Right stau mass $M_{\tilde\tau _R}$.

RMSS(15) :

(D=800. GeV) Bottom trilinear coupling $A_{\b }$. When IMSS(5)=1, it is a derived quantity.

RMSS(16) :

(D=400. GeV) Top trilinear coupling $A_{\t }$. If IMSS(1)=2, the common trilinear coupling $A$. When IMSS(5)=1, it is a derived quantity.

RMSS(17) :

(D=0.) Tau trilinear coupling $A_{\tau}$. When IMSS(5)=1, it is a derived quantity.

RMSS(18) :

(D=0.1) Higgs mixing angle $\alpha$. This is only used when all of the Higgs parameters are set by you, i.e IMSS(4)=2.

RMSS(19) :

(D=850. GeV) Pseudoscalar Higgs mass parameter $M_{\mathrm{A}}$.

RMSS(20) :

(D=0.041) GUT scale coupling constant $\alpha_{\mathrm{GUT}}$.

RMSS(21) :

(D=1.0 eV) The gravitino mass. Note nonconventional choice of units for this particular mass.

RMSS(22) :

(D=800. GeV) $\tilde{\mathrm u}_R$ mass when IMSS(9)=1.

RMSS(23) :

(D=10$^4$ GeV$^2$) $D_X$ contribution to scalar masses when IMSS(7)=1.

RMSS(24) :

(D=10$^4$ GeV$^2$) $D_Y$ contribution to scalar masses when IMSS(7)=1.

RMSS(25) :

(D=10$^4$ GeV$^2$) $D_S$ contribution to scalar masses when IMSS(7)=1.

RMSS(26) :

(D=0.0 radians) when IMSS(5)=1 it is the sbottom mixing angle.

RMSS(27) :

(D=0.0 radians) when IMSS(5)=1 it is the stop mixing angle.

RMSS(28) :

(D=0.0 radians) when IMSS(5)=1 it is the stau mixing angle.

RMSS(29) :

(D= $2.4 \times 10^{18}$ GeV) The Planck mass, used for calculating decays to light gravitinos.

RMSS(30) - RMSS(33) :

(D=0.0,0.0,0.0,0.0) complex phases for the mass parameters in RMSS(1) - RMSS(4), where the latter represent the moduli of the mass parameters for the case of nonvanishing phases.

RMSS(40), RMSS(41) :

used for temporary storage of the corrections $\Delta m_{\t }$ and $\Delta m_{\b }$, respectively, in the calculation of Higgs properties.

RMSS(51) :

(D=0.0) when IMSS(51)=1 it is the negative logarithm of the common value for all lepton number violating $\lambda$ couplings (LLE). When IMSS(51)=2 it is the constant of proportionality for generation-hierarchical $\lambda$ couplings. See section .

RMSS(52) :

(D=0.0) when IMSS(52)=1 it is the negative logarithm of the common value for all lepton number violating $\lambda'$ couplings (LQD). When IMSS(52)=2 it is the constant of proportionality for generation-hierarchical $\lambda'$ couplings. See section .

RMSS(53) :

(D=0.0) when IMSS(53)=1 it is the negative logarithm of the common value for all baryon number violating $\lambda''$ couplings (UDD). When IMSS(53)=2 it is the constant of proportionality for generation-hierarchical $\lambda''$ couplings. See section .

Purpose:

to provide information on the neutralino, chargino, and sfermion mixing parameters. The variables should not be changed by you.

ZMIX(4,4) :

the real part of the neutralino mixing matrix in the Bino-neutral Wino-Up higgsino-Down higgsino basis.

UMIX(2,2) :

the real part of the chargino mixing matrix in the charged Wino-charged higgsino basis.

VMIX(2,2) :

the real part of the charged conjugate chargino mixing matrix in the wino-charged higgsino basis.

SMZ(4) :

the signed masses of the neutralinos.

SMW(2) :

the signed masses of the charginos.

SFMIX(16,4) :

the sfermion mixing matrices T in the L-R basis, identified by the corresponding fermion, i.e. SFMIX(6,I) is the stop mixing matrix. The four entries for each sfermion are $\mathrm{T}_{11}, \mathrm{T}_{12}, \mathrm{T}_{21},$ and $\mathrm{T}_{22}$.

ZMIXI(4,4) :

the imaginary part of the neutralino mixing matrix in the Bino-neutral Wino-Up higgsino-Down higgsino basis.

UMIXI(2,2) :

the imaginary part of the chargino mixing matrix in the charged Wino-charged higgsino basis.

VMIXI(2,2) :

the imaginary part of the charged conjugate chargino mixing matrix in the wino-charged higgsino basis.

Purpose:

to provide information on lepton and baryon number violating couplings.

RVLAM(3,3,3) :

the lepton number violating $\lambda_{ijk}$ couplings. See IMSS(51), RMSS(51).

RVLAMP(3,3,3) :

the lepton number violating $\lambda'_{ijk}$ couplings. See IMSS(52), RMSS(52).

RVLAMB(3,3,3) :

the baryon number violating $\lambda''_{ijk}$ couplings. Currently not used.

The following subroutines and functions need not be accessed by the user, but are described for completeness.

SUBROUTINE PYAPPS :

uses approximate analytic formulae to determine the full set of MSSM parameters from SUGRA inputs.

SUBROUTINE PYGLUI :

calculates gluino decay modes.

SUBROUTINE PYGQQB :

calculates three body decays of gluinos into neutralinos or charginos and third generation fermions. These routines are valid for large values of $\tan\beta$.

SUBROUTINE PYCJDC :

calculates the chargino decay modes.

SUBROUTINE PYHEXT :

calculates the non-Standard Model decay modes of the Higgs bosons.

SUBROUTINE PYHGGM :

determines the Higgs boson mass spectrum using several inputs.

SUBROUTINE PYINOM :

finds the mass eigenstates and mixing matrices for the charginos and neutralinos.

SUBROUTINE PYMSIN :

initializes the MSSM simulation.

SUBROUTINE PYLHA3 :

to read in or write out SUSY Les Houches Accord spectra and decay tables. Can also be used stand-alone, before the call to PYINIT, to read in SUSY Les Houches Accord decay tables for specific particles. See section for how to do this.

SUBROUTINE PYNJDC :

calculates neutralino decay modes.

SUBROUTINE PYPOLE :

computes the Higgs boson masses using a renormalization group improved leading-log approximation and two-loop leading-log corrections.

SUBROUTINE PYSFDC :

calculates sfermion decay modes.

SUBROUTINE PYSUBH :

computes the Higgs boson masses using only renormalization group improved formulae.

SUBROUTINE PYTBDY :

samples the phase space for three body decays of neutralinos, charginos, and the gluino.

SUBROUTINE PYTHRG :

computes the masses and mixing matrices of the third generation sfermions.

SUBROUTINE PYRVSF :

$R$-violating sfermion decay widths.

SUBROUTINE PYRVNE :

$R$-violating neutralino decay widths.

SUBROUTINE PYRVCH :

$R$-violating chargino decay widths.

SUBROUTINE PYRVGW :

calculates $R$-violating 3-body widths using PYRVI1, PYRVI2, PYRVI3, PYRVG1, PYRVG2, PYRVG3, PYRVG4, PYRVR, and PYRVS.

FUNCTION PYRVSB :

calculates $R$-violating 2-body widths.

SUBROUTINE SUGRA :

dummy routine, to avoid linking problems when ISAJET is not linked; see IMSS(1) = 12.

FUNCTION VISAJE :

dummy routine, to avoid linking problems when ISAJET is not linked; see IMSS(1) = 12.