Homepage of Ayres Freitas

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My working area is theoretical high energy elementary particle physics. Currently, most results both from low and high energy experiments are well described by a theory called the Standard Model. This model is larglely defined by a few symmetries, some of which must be broken. However, the Standard Model contains only an unsatisfactory explanation for these broken symmetries. In particular, the Standard Model fails to describe the origion of ordinary matter as well as dark matter in the universe. These shortcomings have spawned many new ideas like supersymmetry, extra dimensions, technicolor and little Higgs models, which all predict many new heavy particles.

My research mostly deals with the phenomenology of these new particles and their interactions at future colliders, most notably at the Large Hadron Collider (LHC), which will start operation in 2008. Furthermore, models for physics beyond the Standard Model can be constrained by existing precision data and possibly could be discovered at future experiments, most notably at the Large Hadron Collider (LHC). Of special interest to me are precision analyses that would allow to reconstruct the underlying framework of a model from experimental data. I am working on methods to determine the spin and couplings of newly discovered particles, as well as ideas to detect particles that would be particularly eluvise. One main focus has been on supersymmetric models, but also on models with extra dimensions, extended gauge groups and little Higgs models.

Some of the new physics models quite naturally could explain the origin of ordinary matter and/or dark matter in the universe. This opens up striking connections between collider physics and astrophysics and cosmology.

On the technical side, development of loop calculation techniques and Monte-Carlo tools are very important for the interpretation of the flood of new data expected from the LHC. Recently there has been much progress in both areas, leading to automated computer programs. I have been working on methods for electroweak one- and two-loop calculations, as well as implementation of new models in Monte-Carlo generators.

Recent projects and publications:

General Analysis of Decay Chains With Three-Body Decays Involving Missing Energy
C.-Y. Chen, A. Freitas, arXiv:1110.6192

Feasibility of Slepton Precision Measurements at a Muon Collider
A. Freitas, arXiv:1107.3853

Axinos in Cosmology and at Colliders
A. Freitas, F. D. Steffen, N. Tajuddin, D. Wyler, JHEP 1106, 036 (2011)

General Analysis of Signals with Two Leptons and Missing Energy at the Large Hadron Collider
C.-Y. Chen, A. Freitas, JHEP 1102, 002 (2011)

Multi-Photon Signals from Composite Models at LHC
A. Freitas, P. Schwaller, JHEP 1102, 002 (2011)

The Matrix Element Method and QCD Radiation
J. Alwall, A. Freitas, O. Mattelaer, Phys. Rev. D 83, 074010 (2011)

Dirac Neutralinos and Electroweak Scalar Bosons of N=1/N=2 Hybrid Supersymmetry at Colliders
S. Choi, D. Choudhury, A. Freitas, J. Kalinowski, J. Kim, P. Zerwas, JHEP 1008, 025 (2010)

Measuring Sparticles with the Matrix Element
J. Alwall, A. Freitas, O. Mattelaer, AIP Conf. Proc. 1200, 442 (2010)

Computer codes:

Slepton production at lepton colliders:

NLO corrections to R-smuon production,	e⁺e⁻ → μ_R⁺μ_R⁻	(Installation and user's guide)
NLO corrections to L-smuon production,	e⁺e⁻ → μ_L⁺μ_L⁻	(Installation and user's guide)
NLO corrections to R-selectron production,	e⁺e⁻ → e_R⁺e_R⁻	(Installation and user's guide)
NLO corrections to R-selectron production in e-e- collisions,	e⁻e⁻ → e_R⁻e_R⁻	(Installation and user's guide)
NLO corrections to muon-sneutrino production,	e⁺e⁻ → ν_&muν_&mu^*	(Installation and user's guide)
NLO corrections to electron-sneutrino production,	e⁺e⁻ → ν_eν_e^*	(Installation and user's guide)

Littlest Higgs model with T-parity broken by WZW term:

CalcHEP model file