Discription: Em Julho de 2012 foi anunciado no CERN a descoberta da partícula de Higgs, prevista em 1964 por Higgs, Englert e Brout. Os dois primeiros viriam a ter o Premio Nobel de 2013. Esta partícula corresponde a um campo de spin zero, necessário para dar massa às restantes partículas do Modelo Standard das Interacções Electrofracas. Não há nada de fundamental na teoria que determine o número de partículas escalares. Assim, ao mesmo tempo que se determinam as propriedades da partícula encontrada, é necessário procurar que alterações se prevêem caso existam mais partículas escalares; os chamados modelos de multi-Higgs. Neste projecto, pretende-se explorar as consequências para o LHC da presença de mais do que um Higgs. O projecto poderá ter mais interface com as experiências ou ser mais teórico, consoante os interesses da/o aluna/o.

Discription: Uma das questões fundamentais ainda não resolvidas na física de partículas é explicar porque o nosso Universo é dominado por matéria e não observamos antimatéria nele. A observação desta assimetria matéria-antimatéria constitui também uma evidência da existência de física para além do modelo padrão das interacções fortes e electrofracas. Na tentativa de encontrar uma solução para este problema, várias abordagens e modelos teóricos têm sido propostos ao longo dos últimos anos. Em particular, a leptogénese é um dos mecanismos mais apelativos para explicar esta assimetria, dada a sua relação estreita com a física de neutrinos. Neste projecto, pretende-se abordar algumas das questões em aberto neste campo.

Discription: A origem das massas e misturas dos fermiões constitui um dos problemas fundamentais ainda não resolvidos na física de partículas. Uma possibilidade de abordar esta questão consiste em estender o modelo padrão das interacções electrofracas e fortes postulando a existência de simetrias (horizontais) de familia. Em particular, o uso de simetrias discretas de sabor tem-se tornado popular pelo poder preditivo destas para explicar os angulos de mistura medidos recentemente nas experiências de oscilações de neutrinos. Algumas das questões em aberto neste campo serão abordadas neste projecto.

Discription: There are several good motivations to extend the scalar sector of the Standard Model (SM). Models with an extended scalar sector usually have new sources of CP violation. It is already established that the SM cannot account for the observed baryon asymmetry of the Universe requiring new sources of CP violation. Furthermore some of these extensions may also provide good dark matter candidates. In addition, the existence of a richer scalar sector has important implications for flavour physics.The Large Hadron Collider (LHC) at CERN continues its experimental quest for Physics Beyond the Standard Model after its recent major discovery of one Higgs boson. The future of this field is exciting! The directions of the research work will depend on specific interests of the student. The student will start by being introduced to this important topic of research.

Discription: In the standard model, neutrinos are strictly massless. As a result, one can conclude that the observation of neutrino masses and oscillations provides clear evidence for Physics Beyond the SM. With massive neutrinos there may be CP violation in the leptonic sector, unlike in the standard model where there is neither mixing nor CP violation in the leptonic sector. The fact that neutrinos have no electrical charge allows for more terms to be present in the Lagrangian than in the quark sector, and this has extremely important phenomenological implications. In particular it allows for a new mechanism to explain why there is matter in the Universe rather than just radiation. Without matter life would not be possible. This new mechanism is called Leptogenesis. The directions of the research work will depend on specific interests of the student. The student will start by being introduced to this important topic of research.

Discription: We expect to find New Physics at the LHC-CERN. There is no known fundamental principle why the Universe should have only 4 dimensions. Extra dimension (ED) models are inspired by string theory, which itself is based on the existence of additional spatial dimensions. As known, string theory is a main candidate for an all-including quantum theory which allows for gravity, thus unifying all elementary particle interactions. ED models have some advantages over supersymmetric theories (which is another serious candidate for New Physics). Besides the fact that they lead to the unification of the gauge couplings, either at high 10^16 GeV scales for small warped extra dimension models, or at the lower TeV scales for large flat ED models, they also address the long standing puzzle of the gauge hierarchy problem, i.e. the huge discrepancy between the gravitational scale and the electroweak scale. Furthermore, there is a viable Kaluza-Klein WIMP candidate for the dark matter of the universe. In addition, ED models explain the large mass hierarchy of the different types and generations of the SM fermions through a geometrical mechanism. But what are the finer points of the fermion mass hierarchy, mixing and CP violation, within ED models?
We also shall explore New Physics, in particular models inspired on ED, with vector-like (extra) quarks and multi-Higgs models.

Discription: For several decades, particle physicists have been searching for hints of New Physics, a fundamental theory which must replace the Standard Model we currently have. Up to now, no definitive New Physics signals have been detected. In December 2015, the two LHC collaborations reported a peculiar excess in the two-photon channel around 750 GeV, and it resulted in a hurricane of theoretical publications. Hundreds of theoretical models could accommodate this signal, but without further data, we cannot safely distinguish them. However some information can be extracted even right now on purely kinematical basis. If two photons appear in (cascade) decays of hypothetical heavy particle(s), the exact invariant mass profile of the excess depends on the phase space available and on the number of accompanying undetected particles. In this project, we will derive the invariant mass shapes for various assumptions on decay multiplicity, and check which one gives a better fit to the data. This project will allow a student to obtain a concrete scientific result and to quickly jump into an activity at the bleeding edge of particle physics.

To answer these questions research at CFTP includes many hot topics in theoretical particle physics and cosmology : Fermion Masses & Mixing, CP Violation, Baryogenesis, Leptogenesis, Neutrino Physics, B Physics, Supersymmetry, LFV, Extra Dimensions, Cosmology, Dark Matter & Dark Energy, Inflation, Nuclear Physics, Hadronic Matter, Chiral Symmetry, Confinement. Please see also our list of publications. We have also a strong interaction with theoretical and experimental groups at LIP and at CERN.
These questions, at the frontier of the field, are aligned with the big experimental effort being done or planed for the next decade, in particular at CERN and JLab. These questions are connected in many ways and we organize ourselves in four main lines of research that cover all the above topics.

Research Team: G.C. Branco, D. Emmanuel-Costa, R. González Felipe, F. Joaquim, L. Lavoura, M.N. Rebelo, J.P. Silva, J. I. Silva-Marcos, J. C. Romao and Long Term Visiting Professor F. Botella (U.Valencia)
Since the SM gauge group does not determine the number of scalars, the pressing phenomenological question is to determine how many fundamental scalars there are and what their exact nature is. An extended Higgs sector may give new sources of CP violation with important implications for Neutrino Physics and Leptogenesis. It can allow for the possibility of having spontaneous CP violation, and in some extensions together, with the inclusion of at least one vectorial quark, allow for a common origin for all CP violations. It can also provide a viable DM candidate. Included in this topic are the study of the origin of fermion masses and mixing, CP violation at B factories, baryogenesis, Physics at colliders and flavor Physics.

Research Team: G.C. Branco, D. Emmanuel-Costa, R. González Felipe, F. Joaquim, L. Lavoura ,João Pulido , M.N. Rebelo, J. C. Romão, J.I. Silva-Marcos and Long Term Visiting Professor J. W. F. Valle (U.Valencia)
Oscillation experiments have achieved high precision in determining the neutrino mass and mixing pattern. The most important new result is the theta13 mixing angle recently measured by the Daya-Bay and RENO reactor experiments. The fact that theta13 is not close to zero may allow for the discover of CP violation in the lepton sector. The old and long standing mystery regarding the origin of fermion masses and mixing seems now even more intriguing: why are the neutrino masses very suppressed and mixings large, in contrast with what is observed in the quark sector. Included in this topic are the study of neutrino-mass generation mechanisms, neutrino Oscillations, CP-Violation in the Leptonic sector and Baryogenesis through leptogenesis. Grand Unified Theories, with an extended Higgs sector are also under study in this topic, as well as models dor Dm from the Higgs sector.

Research Team: G.C. Branco, D. Emmanuel-Costa, R. González Felipe, F. Joaquim, L. Lavoura, P.A. Parada ,João Pulido , M.N. Rebelo, J.P. Silva, J.I. Silva-Marcoss and Long Term Visiting Professor F. Botella (U.Valencia)
The origin of fermion masses and mixing and of CP violation are some of the major outstanding problems in particle physics. These members of CFTP have been working actively in CP violation, as well as in attempts at understanding the observed patterns of fermion masses and mixing, both in the quark and in the leptonic sector. We are especially interested in pursuing the following topics of research: Family symmetries and patterns of neutrino mass matrices; Baryogenesis through leptogenesis; CP violation at B factories; Physics at colliders.

Research Team: J.C. Romão, G.C. Branco, F. Joaquim, D. Emmanuel-Costa, L. Lavoura
Supersymmetry (SUSY) allows for deviations from the SM that are very small at the electroweak scale, while offering a solution to the hierarchy problem and provide a DM candidate. Also SUSY seesaw models offer an explanation for the smallness of the neutrino masses and open a window into charged LFV. The experimental search for SUSY plays an important role in the analysis of the LHC data. The present indication of a light Higgs boson with mass around 125 GeV is compatible with a heavy spectrum. The next phase of LHC at 14 TeV will be crucial to find out if this beautiful idea plays a role at present energies. Included in this topic are supersymmetric unification, supersymmetric neutrino-mass generation mechanisms, CP violation in supersymmetry, Lepton-flavour violation (LFV), and Drak Matter.

Research Team: T. Peña and Alfred Stadler, also in collaboration with Jefferson Laboratory
In this area, our general objective is to create innovative theoretical methods to interpret data from large experimental infrastructures (e.g. at Jlab, HADES, PANDA/FAIR, LHCb). Meson and baryon electromagnetic form factors are among the most fundamental observables in hadron physics and they will be a focus of our activity. They are essential for the puzzle of connecting the observed properties of mesons and baryons and the underlying QCD quark-gluon dynamics. Also the interpretation of the nuclear matter emissivity from experiments of elementary reactions and of heavy ion collisions, needs a detailed knowledge of those form factors in the timelike region. Our approach in Minkowski space makes our group unique because it enables calculations of transition form factors in the timelike region, where lattice QCD and the Dyson-Schwinger approach do not work yet. We aim to contribute to the new accuracy era made possible by the LHC. The interpretation of recent data from the LHCb detector on exotic quark structures, as tetraquarks, and on quarkonia states from the CMS detector, demands precision spectroscopic calculations that supersede the old generation of quark models of the 1980's.