New-physics event generation

Introduction

Using my Apollo generator I generated events coming from proton-antiproton collisions at the Tevatron collider. I worked on the Drell-Yan (2→2), top-antitop to leptons (2→6) and chargino-neutralino to trileptons (2→6) processes. The originality comes from the fact that I did not fix the new-physics theory parameters; I let the generator surf the parameter space and generate events by sampling kinematic variables and theory parameters simultaneously. The importance sampling helps us concentrate in the parameter-space regions where the new-physics cross-section is higher. I present here results from Drell-Yan and chargino-neutralino production. Please note that this is work in progress and the full capacity of this generator has not been utilized yet.

Exotic Drell-Yan

I let the two couplings, Z pole-mass and lepton mass vary, which allows us to study anomalous couplings, new gauge bosons and 4th generation leptons simultaneously. This results into an 8-dimensional Monte Carlo integral (4 kinematic variables and 4 theory parameters), which smoothly converged.

After making sure that the Standard Model Drell Yan agrees with Madevent, I started floating the 4 parameters and I see that indeed the sampling is such that the cross section is maximized: Remember, one file has all these parameters and also the kinematics. So you can now start playing! Starting from upper-left and going clock-wise you can see: a) the Z invariant mass distribution for three different ranges of the Z pole mass, b) the forward-backward asymmetry for two different selections of the right-handed and left-handed couplings, c) the transverse mass of the leptons as a function of the exotic lepton mass, d) lepton transverse mass as a function of the lepton mass, e) lepton transverse mass as a function of the lepton mass, f) comparison between dedicated Standard-Model generation and the multi-parameter one, constraining the Z pole mass to be close to the Standard Model (in order to study smearing effects). And all this with only 1 generation and 1 file.

Chargino-Neutralino production

Although I already have the infrastructure to vary the mSUGRA parameters instead of masses and couplings (and real time calculate the masses and couplings from the renormalization group equations), I show here the result of directly floating three couplings and three masses (of chargino and two neutralinos) simultaneously. This results into an 8-dimensional Monte Carlo integral (4 kinematic variables and 4 theory parameters), which smoothly converged.

Upper left: The sampling of the lightest neutralino (lower masses lead to higher cross section and they are preferred).
Upper right: Some of masses of chargino and next-to-lightest (NL) neutralino as a function of lightest neutralino mass.
Bottom: Transverse momentum of lepton coming from NL neutralino, as a function of the NL neutralino mass.
These are just few examples to raise your interest. A more complete study of new signals, cut optimization, exclusion limits etc. is under way. Please visit the Pheno08 talk.