Rare Decays of the
Pseudoscalar Higgs

TeV4LHC@BNL Workshop

Bryan J. Field

Stony Brook University

Brookhaven National Laboratory

Friday, February 4, 2005

Outline

Brief review of the Pseudoscalar Higgs

Current MSSM branching ratios

Squarks and squark mixing

New three point functions

New decay widths and squark contributions

A0 → Z0

A0 → Z0Z0

Improved branching ratios

Conclusion

MSSM and the Pseudoscalar

MSSM has five physical Higgs bosons

One CP-odd Pseudoscalar (A0)

Couples differently to up- and down-type quarks as well as up- and down- type squarks

Interested in top and bottom quarks and stop and sbottom squarks

The parameter tan() (partially) controls the ratio of up- and down- type contributions

Pseudoscalar has no tree-level coupling to W∓/Z0 vector bosons

Need one-loop level contributions

HDecay Output

Squarks and Squark Mixing

R/L handed quarks have scalar super-partners (denoted with tilde)

Right and left handed squarks can mix into different mass eigenstates

This is done squark by squark in the simplest case (ignore generational mixing)

Introduce angles to diagonalize the mass eigenstates for each squark

The mixing angles are not completely free parameters

We pick m2 and Lagrangian parameters

Three Point Functions

Quark contributions are known, squark contributions are not known

Need to generate the one-loop three-point squark contributions ()

These contributions come in two types for our processes (triangle and bubble)

The squark contributions do not interfere with the quark contributions (tensor structure)

This could be a window into the squark mixing (may not be optimal)

What do they look like?

Feynman Diagrams

Squark loops need not be

mass eigenstate diagonal

Need These Three-Point Functions

Decay Widths (Z0)

Decay Widths (Z0Z0)

Branching Ratios

Conclusions

The Z0 channel has negligible squark contributions, particularly at high MA0

Maximum with large stop mixing and small sbottom mixing (light squarks)

The Z0Z0 channel can have considerable squark contributions

Same maximum as Z0 channel

Large sbottom mixing introduces a dip in the decay width

Bryan Field

2005-02-01T16:23:06