  Spin correlations for tau lepton decays are included in the Pythia 8 event
generation software and the spin correlations for the decays of tau leptons
produced from electroweak and Higgs bosons are calculated. Decays of the tau
lepton using sophisticated resonance models are included in Pythia 8 for all
channels with experimentally observed branching fractions greater than 0.04%.
The mass distributions for the decay products of these channels are validated
and the technical implementation of these decays is described.
  A measurement of the inclusive Z to di-tau cross-section using 1.0 inverse fb
of data from pp collisions at sqrt(s) = 7 TeV collected with the LHCb detector
is presented. Reconstructed final states containing two muons, a muon and an
electron, a muon and a charged hadron, or an electron and a charged hadron are
selected as candidates. The cross-section for Z bosons with a mass between 60
and 120 GeV decaying into tau leptons with pseudo-rapidities between 2.0 and
4.5 and transverse momenta greater than 20 GeV is measured to be 72.3 +- 3.5 +-
2.9 +- 2.5 pb. The first uncertainty is statistical, the second uncertainty is
systematic, and the third is to due the integrated luminosity uncertainty.
  Limits on the production of neutral Higgs bosons decaying into tau lepton
pairs with pseudo-rapidities between 2.0 and 4.5 are set at a 95% confidence
level using the same LHCb dataset. A model independent upper limit on the
production of neutral Higgs bosons decaying into tau leptons is set and ranges
between 8.6 pb for a Higgs boson mass of 90 GeV to 0.7 pb for a Higgs boson
mass of 250 GeV. An upper limit on tan-beta in the CP-odd Higgs mass and
tan-beta plane is set for the mh-max scenario of the minimal supersymmetric
model and varies from 34 for a CP-odd Higgs boson mass of 90 GeV to 70 for a
CP-odd Higgs boson mass of 140 GeV.
