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Search Results: 1 - 10 of 156464 matches for " F. del Aguila "
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Model-independent determination of $Z'$ couplings at LEP 200
F. del Aguila
Physics , 1994, DOI: 10.1016/0920-5632(94)90674-2
Abstract: All couplings of a new heavy gauge boson to ordinary fermions can be determined in a model-independent way at a large $e^+e^-$ collider for large enough statistics. No such determination is possible at LEP 200, however, because its design integrated luminosity is too low for existing and forthcoming limits on $Z'$ interactions. At any rate, it should be possible to distinguish between models for $Z'$ masses $< 1\ TeV$, or to set limits of this order on $Z'$ masses for definite models. These are (preliminary) $1\sigma $ limits. We neglect systematic errors and assume an integrated luminosity of $0.5\ fb^{-1}$.
The Physics of Z' bosons
F. del Aguila
Physics , 1994,
Abstract: In these lectures we review the simplest gauge extensions of the standard model, and the present and future limits on new weak interactions.
Quark mixing: determination of top couplings
F. del Aguila
Physics , 1999,
Abstract: The top flavour-changing neutral couplings can be large in extended models with vector-like quarks. In the next decade(s) the CERN Large Hadron Collider will allow to measure (bound) them with a precision of few per cent.
Diagnostic Power of Future Colliders for Z'Couplings to Quarks and Leptons: e+e- versus pp Colliders
F. del Aguila,M. Cvetic
Physics , 1993, DOI: 10.1103/PhysRevD.50.3158
Abstract: We study the diagnostic power of future $e^+e^-$ colliders with ${\sqrt {s}} = 500$ GeV (the New Large Collider ($NLC$)) for a model independent determination of the $Z'$ gauge couplings to quarks and leptons. The interference of the $Z'$ propagator with the photon and the $Z$ propagator in the two-fermion final state probes are sensitive to the magnitude as well as relative signs of quark and lepton charges. For $Z'$ with $M_{Z'} \sim 1 $ TeV {\it all } the quark and lepton charges can be determined to around $10-20 \%$, provided heavy flavor tagging and longitudinal polarization of the electron beam is available. The errors are $2-10$ times larger without polarization, and very little information can be obtained about quark charges without heavy flavor tagging. We point out the complementarity of future hadron colliders. At the CERN Large Hadron Collider ($LHC$) primarily the magnitude of three out of four corresponding couplings can be measured; however, their error-bars are typically by a factor of $\sim 2$ smaller than those at the $NLC$.
CP Phases in Models with Some Fermion Masses Vanishing and/or Degenerate
F. del Aguila,M. Zralek
Physics , 1996,
Abstract: We count the number of CP breaking phases in models with $SU(2)_L\times U(1)_Y$ and $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ electroweak gauge groups and extended matter contents with some fermion masses vanishing and/or degenerate. Quarks and leptons, including Majorana neutrinos, are treated in a similar way. CP violation is characterized in the mass-eigenstate and in the weak-eigenstate bases. Necessary and sufficient conditions for CP conservation, invariant under weak basis redefinitions are also studied in these models. CP violating factors entering in physical observables and only invariant under phase redefinitions are discussed.
Top mixing in effective theories
F. del Aguila,J. Santiago
Physics , 2000, DOI: 10.1016/S0920-5632(00)00820-3
Abstract: We review how top mixing with light quarks constrains new physics beyond the Standard Model using the effective Lagrangian approach.
Large top mixing from extra dimensions
F. del Aguila,J. Santiago
Physics , 2000,
Abstract: Fermion mixing is conveniently described using the effective Lagrangian formalism. We apply this approach to study top mixing in models with an infinite tower of Kaluza-Klein fermion excitations. In the Randall-Sundrum background with a boundary Higgs and phenomenologically viable values of the model parameters, the only effect eventually observable is the loss of universality of the top couplings. Their deviation from the SM predictions can be up to 4 % if the five-dimensional Yukawa couplings times the AdS_5 curvature scale are < 10.
Universality limits on bulk fermions
F. del Aguila,J. Santiago
Physics , 2000, DOI: 10.1016/S0370-2693(00)01110-2
Abstract: The Kaluza-Klein fermion excitations induce mixing between the Standard Model fermions and loss of universality. The flavour mixing not present in the Standard Model can be made to vanish aligning the Yukawa couplings and the Dirac masses of the heavy modes, but universality is only recovered when these masses go to infinity. This implies a bound on the lightest new heavy quark, M1 \~ 3-5 TeV, which together with the electroweak precision data limits will allow the Large Hadron Collider to provide a crucial test of the Randall-Sundrum ansatz for solving the gauge hierarchy.
Signals from extra dimensions decoupled from the compactification scale
F. del Aguila,J. Santiago
Physics , 2001, DOI: 10.1088/1126-6708/2002/03/010
Abstract: Multilocalization provides a simple way of decoupling the mass scale of new physics from the compactification scale of extra dimensions. It naturally appears, for example, when localization of fermion zero modes is used to explain the observed fermion spectrum, leaving low energy remnants of the geometrical origin of the fermion mass hierarchy. We study the phenomenology of the simplest five dimensional model with order one Yukawa couplings reproducing the standard fermion masses and mixing angles and with a light Kaluza-Klein quark Q_{2/3} saturating experimental limits on V_{tb} and m_Q, and then with observable new effects at Tevatron.
Neutrino oscillations beyond the Standard Model
del Aguila, F.;Syska, J.;Zralek, M.
High Energy Physics - Phenomenology , 2008, DOI: 10.1088/1742-6596/136/4/042027
Abstract: We address the possible impact of New Physics on neutrino oscillation experiments. This can modify the neutrino production, propagation and/or detection, making the full cross section non-factorizable in general. Thus, for example, the neutrino flux may not be properly described assuming an unitary MNS matrix and/or neutrinos may propagate differently depending of their Dirac or Majorana character. Interestingly enough, present limits on New Physics still allow for observable effects at future neutrino experiments.
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