Marco Diaz - Academia.edu (original) (raw)

Papers by Marco Diaz

Journal of the European Ceramic Society, 2000

The main objective of this work is to show that the difficulties involving substantial difference... more The main objective of this work is to show that the difficulties involving substantial differences in particle size and density of commercial molybdenum and mullite powders, when attempts are made to produce homogeneous and/or functionally graded materials, can be overcome by intelligent choice of processing parameters. The flocculant effect of an anionic polyelectrolyte on Mo particles in water and in

The Astrophysical Journal Supplement Series, 1993

It is analyzed the branching ratio B(brightarrowsgamma)B(b\rightarrow s\gamma)B(brightarrowsgamma) in the context of minimal N=1N=1N=1 supe... more It is analyzed the branching ratio B(brightarrowsgamma)B(b\rightarrow s\gamma)B(brightarrowsgamma) in the context of minimal N=1N=1N=1 supergravity with radiatively broken electroweak symmetry group. There is a strong dependence on supersymetric parameters, but constraints on the charged Higgs mass in non-supersymmetric models are relaxed, due to large contribution from the chargino/up-type squark sector that interacts destructively with the Standard Model and the charged Higgs contributions. Large suppressions/enhancements of the branching fraction are found for large values of tanbeta\tan\betatanbeta.

Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Stand... more Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Standard Model (SM). In contrast, we present an improved calculation of an upper limit on the lightest higgs mass in supersymmetric (susy) models, by summing to all orders in perturbation theory the leading and next--to--leading logarithms with a renormalization group equation technique, and by

Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Stand... more Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Standard Model (SM). In contrast, we present an improved calculation of an upper limit on the lightest higgs mass in supersymmetric (susy) models. We study the possibility that these bounds do not overlap, and find that i) a gap between the SM and the

Journal of High Energy Physics, 2001

Nuclear Physics B - Proceedings Supplements, 2000

In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpo... more In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpotential, which can explain the solar and atmospheric neutrino problems, we study the unification of gauge and Yukawa couplings at the GUT scale. We show that bottom-tau Yukawa coupling unification can be achieved at any value of tan β, and that the strong coupling constant prediction from unification of gauge couplings is closer to the experimental value compared with the MSSM. We also study the predictions for V cb in a Yukawa texture ansätze.

Physics Letters B, 1994

It is analyzed the branching ratio B(b → sγ) in the context of minimal N = 1 supergravity with ra... more It is analyzed the branching ratio B(b → sγ) in the context of minimal N = 1 supergravity with radiatively broken electroweak symmetry group. There is a strong dependence on supersymetric parameters, but constraints on the charged Higgs mass in non-supersymmetric models are relaxed, due to large contribution from the chargino/up-type squark sector that interacts destructively with the Standard Model and the charged Higgs contributions. Large suppressions/enhancements of the branching fraction are found for large values of tan β.

Physics Letters B, 1999

We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymm... more We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymmetric Standard Model (MSSM) which incorporates R-Parity violation through a bilinear superpotential term. Contrary to what happens in the MSSM, we show that bottom-tau unification at the scale M GU T where the gauge couplings unify can be achieved for any value of tan β by choosing appropriately the sneutrino vacuum expectation value. In addition, we show that bottom-tau-top unification occurs in a slightly wider tan β range than in the MSSM.

Physics Letters B, 1993

The calculation of the one-loop induced decay rate b ~ s7 is improved by including radiative corr... more The calculation of the one-loop induced decay rate b ~ s7 is improved by including radiative corrections to the charged Higgs mass and to the charged-Higgs-fermion-fermion vertex. It is shown how the radiative corrections modify the excluded zone in the tan fl-m,4 plane, imposed by the non-observation of this decay. In particular, a light CP-odd Higgs at large tan fl becomes allowed.

Physical Review D, 2000

We examine the spectrum of superparticles obtained from the minimal SO(10) grand unified model, w... more We examine the spectrum of superparticles obtained from the minimal SO(10) grand unified model, where it is assumed the gauge symmetry breaking yields the Minimal Supersymmetric Standard Model (MSSM) as the effective theory at M GU T ∼ 2 × 10 16 GeV. In this model, unification of Yukawa couplings implies a value of tan β ∼ 45 − 55. At such high values of tan β, assuming universality of scalar masses, the usual mechanism of radiative electroweak symmetry breaking breaks down. We show that a set of weak scale sparticle masses consistent with radiative electroweak symmetry breaking can be generated by imposing non-universal GUT scale scalar masses consistent with universality within SO(10) plus extra D-term contributions associated with the reduction in rank of the gauge symmetry group when SO(10) spontaneously breaks to SU (3)×SU (2)×U (1). We comment upon the consequences of the sparticle mass spectrum for collider searches for supersymmetry. One implication of SO(10) unification is that the light bottom squark can be by far the lightest of the squarks. This motivates a dedicated search for bottom squark pair production at pp and e + e − colliders.

Nuclear Physics B, 1998

We consider the charged scalar boson phenomenology in the simplest effective low-energy Rparity b... more We consider the charged scalar boson phenomenology in the simplest effective low-energy Rparity breaking model characterized by a bilinear violation of R-parity in the superpotential. This induces a mixing between staus and the charged Higgs boson. We show that the charged Higgs boson mass can be lower than expected in the MSSM, even before including radiative corrections. We also study the charged scalar boson decay branching ratios and show that the R-parity-violating decay rates can be comparable or even bigger than the R-parity conserving ones. Moreover, if the stau is the LSP it will have only decays into standard model fermions. These features could have important implications for charged supersymmetric scalar boson searches at future accelerators. (~ 1998 Elsevier Science B.V.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

New developments in Thin Gap Chambers (TGC) detectors to provide fast trigger and high precision ... more New developments in Thin Gap Chambers (TGC) detectors to provide fast trigger and high precision muon tracking under sLHC conditions are presented. The modified detectors are shown to stand a high total irradiation dose equivalent to 6 Coulomb/cm of wire, without showing any deterioration in their performance. Two large (1.2 × 0.8 m 2 ) prototypes containing four gaps, each gap providing pad, strips and wires readout, with a total thickness of 50 mm, have been constructed. Their local spatial resolution has been measured in a 100 GeV/c muon test beam at CERN. At perpendicular incidence angle, single gap position resolution better than 60 µm has been obtained. For incidence angle of 20 o resolution of less than 100 µm was achieved. TGC prototypes were also tested under a flux of 10 5 Hz/cm 2 of 5.5-6.5 MeV neutrons, showing a high efficiency for cosmic muons detection.

The European Physical Journal C, 2005

We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear... more We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear R-Parity violation. The relatively high value of tan β makes the one-loop contribution to the neutrino mass matrix as important as the tree-level one. The atmospheric angle is nearly maximal, and its deviation from maximal mixing is related to the smallness of the ratio between the solar and atmospheric mass scales. There is also a common origin for the small values of the solar and reactor angles, but the later is much smaller due the large mass ratio between the lightest two neutrinos. There is a high dependence of the neutrino mass differences on the scalar mass m 0 and the gaugino mass M 1/2 , but a smaller one of the mixing angles on the same sugra parameters. Measurements of branching ratios for the neutralino decays can give important information on the parameters of the model. There are good prospects at a future Linear Collider for these measurements, but a more detailed analysis is necessary for the LHC.

Physics Letters B, 2012

ABSTRACT 10 pages plus author list (22 pages total), 3 figures, 3 tables, submitted to Physics Le... more ABSTRACT 10 pages plus author list (22 pages total), 3 figures, 3 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at this http URL, See paper for full list of authors

Journal of the European Ceramic Society, 2000

The main objective of this work is to show that the difficulties involving substantial difference... more The main objective of this work is to show that the difficulties involving substantial differences in particle size and density of commercial molybdenum and mullite powders, when attempts are made to produce homogeneous and/or functionally graded materials, can be overcome by intelligent choice of processing parameters. The flocculant effect of an anionic polyelectrolyte on Mo particles in water and in

The Astrophysical Journal Supplement Series, 1993

It is analyzed the branching ratio B(brightarrowsgamma)B(b\rightarrow s\gamma)B(brightarrowsgamma) in the context of minimal N=1N=1N=1 supe... more It is analyzed the branching ratio B(brightarrowsgamma)B(b\rightarrow s\gamma)B(brightarrowsgamma) in the context of minimal N=1N=1N=1 supergravity with radiatively broken electroweak symmetry group. There is a strong dependence on supersymetric parameters, but constraints on the charged Higgs mass in non-supersymmetric models are relaxed, due to large contribution from the chargino/up-type squark sector that interacts destructively with the Standard Model and the charged Higgs contributions. Large suppressions/enhancements of the branching fraction are found for large values of tanbeta\tan\betatanbeta.

Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Stand... more Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Standard Model (SM). In contrast, we present an improved calculation of an upper limit on the lightest higgs mass in supersymmetric (susy) models, by summing to all orders in perturbation theory the leading and next--to--leading logarithms with a renormalization group equation technique, and by

Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Stand... more Vacuum stability and metastability imply lower limits on the mass of the higgs boson in the Standard Model (SM). In contrast, we present an improved calculation of an upper limit on the lightest higgs mass in supersymmetric (susy) models. We study the possibility that these bounds do not overlap, and find that i) a gap between the SM and the

Journal of High Energy Physics, 2001

Nuclear Physics B - Proceedings Supplements, 2000

In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpo... more In a supersymmetric model where R-Parity and lepton number are violated bilinearly in the superpotential, which can explain the solar and atmospheric neutrino problems, we study the unification of gauge and Yukawa couplings at the GUT scale. We show that bottom-tau Yukawa coupling unification can be achieved at any value of tan β, and that the strong coupling constant prediction from unification of gauge couplings is closer to the experimental value compared with the MSSM. We also study the predictions for V cb in a Yukawa texture ansätze.

Physics Letters B, 1994

It is analyzed the branching ratio B(b → sγ) in the context of minimal N = 1 supergravity with ra... more It is analyzed the branching ratio B(b → sγ) in the context of minimal N = 1 supergravity with radiatively broken electroweak symmetry group. There is a strong dependence on supersymetric parameters, but constraints on the charged Higgs mass in non-supersymmetric models are relaxed, due to large contribution from the chargino/up-type squark sector that interacts destructively with the Standard Model and the charged Higgs contributions. Large suppressions/enhancements of the branching fraction are found for large values of tan β.

Physics Letters B, 1999

We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymm... more We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymmetric Standard Model (MSSM) which incorporates R-Parity violation through a bilinear superpotential term. Contrary to what happens in the MSSM, we show that bottom-tau unification at the scale M GU T where the gauge couplings unify can be achieved for any value of tan β by choosing appropriately the sneutrino vacuum expectation value. In addition, we show that bottom-tau-top unification occurs in a slightly wider tan β range than in the MSSM.

Physics Letters B, 1993

The calculation of the one-loop induced decay rate b ~ s7 is improved by including radiative corr... more The calculation of the one-loop induced decay rate b ~ s7 is improved by including radiative corrections to the charged Higgs mass and to the charged-Higgs-fermion-fermion vertex. It is shown how the radiative corrections modify the excluded zone in the tan fl-m,4 plane, imposed by the non-observation of this decay. In particular, a light CP-odd Higgs at large tan fl becomes allowed.

Physical Review D, 2000

We examine the spectrum of superparticles obtained from the minimal SO(10) grand unified model, w... more We examine the spectrum of superparticles obtained from the minimal SO(10) grand unified model, where it is assumed the gauge symmetry breaking yields the Minimal Supersymmetric Standard Model (MSSM) as the effective theory at M GU T ∼ 2 × 10 16 GeV. In this model, unification of Yukawa couplings implies a value of tan β ∼ 45 − 55. At such high values of tan β, assuming universality of scalar masses, the usual mechanism of radiative electroweak symmetry breaking breaks down. We show that a set of weak scale sparticle masses consistent with radiative electroweak symmetry breaking can be generated by imposing non-universal GUT scale scalar masses consistent with universality within SO(10) plus extra D-term contributions associated with the reduction in rank of the gauge symmetry group when SO(10) spontaneously breaks to SU (3)×SU (2)×U (1). We comment upon the consequences of the sparticle mass spectrum for collider searches for supersymmetry. One implication of SO(10) unification is that the light bottom squark can be by far the lightest of the squarks. This motivates a dedicated search for bottom squark pair production at pp and e + e − colliders.

Nuclear Physics B, 1998

We consider the charged scalar boson phenomenology in the simplest effective low-energy Rparity b... more We consider the charged scalar boson phenomenology in the simplest effective low-energy Rparity breaking model characterized by a bilinear violation of R-parity in the superpotential. This induces a mixing between staus and the charged Higgs boson. We show that the charged Higgs boson mass can be lower than expected in the MSSM, even before including radiative corrections. We also study the charged scalar boson decay branching ratios and show that the R-parity-violating decay rates can be comparable or even bigger than the R-parity conserving ones. Moreover, if the stau is the LSP it will have only decays into standard model fermions. These features could have important implications for charged supersymmetric scalar boson searches at future accelerators. (~ 1998 Elsevier Science B.V.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

New developments in Thin Gap Chambers (TGC) detectors to provide fast trigger and high precision ... more New developments in Thin Gap Chambers (TGC) detectors to provide fast trigger and high precision muon tracking under sLHC conditions are presented. The modified detectors are shown to stand a high total irradiation dose equivalent to 6 Coulomb/cm of wire, without showing any deterioration in their performance. Two large (1.2 × 0.8 m 2 ) prototypes containing four gaps, each gap providing pad, strips and wires readout, with a total thickness of 50 mm, have been constructed. Their local spatial resolution has been measured in a 100 GeV/c muon test beam at CERN. At perpendicular incidence angle, single gap position resolution better than 60 µm has been obtained. For incidence angle of 20 o resolution of less than 100 µm was achieved. TGC prototypes were also tested under a flux of 10 5 Hz/cm 2 of 5.5-6.5 MeV neutrons, showing a high efficiency for cosmic muons detection.

The European Physical Journal C, 2005

We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear... more We study a particular texture of the neutrino mass matrix generated in supergravity with bilinear R-Parity violation. The relatively high value of tan β makes the one-loop contribution to the neutrino mass matrix as important as the tree-level one. The atmospheric angle is nearly maximal, and its deviation from maximal mixing is related to the smallness of the ratio between the solar and atmospheric mass scales. There is also a common origin for the small values of the solar and reactor angles, but the later is much smaller due the large mass ratio between the lightest two neutrinos. There is a high dependence of the neutrino mass differences on the scalar mass m 0 and the gaugino mass M 1/2 , but a smaller one of the mixing angles on the same sugra parameters. Measurements of branching ratios for the neutralino decays can give important information on the parameters of the model. There are good prospects at a future Linear Collider for these measurements, but a more detailed analysis is necessary for the LHC.

Physics Letters B, 2012

ABSTRACT 10 pages plus author list (22 pages total), 3 figures, 3 tables, submitted to Physics Le... more ABSTRACT 10 pages plus author list (22 pages total), 3 figures, 3 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at this http URL, See paper for full list of authors