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Javier Ferrandis

Publications and source records attributed to Javier Ferrandis.

17 recordsLinked to original sources

alpha ~ pi/2 from supersymmetric spontaneous flavor breaking

We propose a flavor model where both CP and flavor symmetries are broken at the supersymmetric level. The model is an effective SU(5) theory based on a U(2) horizontal symmetry. The minimum of the supersymmetric scalar potential can be solved to yield a realistic pattern of charged fermion masses. The Higgs sector contains a symmetric, an antisymmetric and two vector fields, plus their U(2) conjugates. These Higgs fields are the only fields strictly required to break the flavor and CP symmetries and generate masses for all charged fermions including the up-quark. The model predicts the existence of an absolute minimum in the space of CP-phases. The value alpha ~ pi/2 is predicted in a particular limit of the parameter space of the model.

hep-ph

Is the beta phase maximal ?

The current experimental determination of the absolute values of the CKM elements indicates that 2|Vub / Vcb/ Vus| = (1-z) with z given by z = 0.19 +(-) 0.14. This fact implies that irrespective of the form of the quark Yukawa matrices, the measured value of the SM CP phase beta is approximately the maximum allowed by the measured absolute values of the CKM elements. This is beta = pi/6 - z/sqrt{3} for gamma = pi/3 + z/sqrt{3}, which implies alpha = pi/2. Alternatively, assuming that beta is exactly maximal and using the experimental measurement, sin(2beta) = 0.726 +(-) 0.037, the phase gamma is predicted to be gamma = pi/2 - beta = 66.3 +(-) 1.7. The maximality of beta, if confirmed by the near-future experiments, may give us some clues as to the origin of CP violation.

hep-ph

Solving the SUSY CP problem with flavor breaking F-terms

Supersymmetric flavor models for the radiative generation of fermion masses offer an alternative way to solve the SUSY-CP problem. We assume that the supersymmetric theory is flavor and CP conserving. CP violating phases are associated to the vacuum expectation values of flavor violating susy-breaking fields. As a consequence, phases appear at tree level only in the soft supersymmetry breaking matrices. Using a U(2) flavor model as an example we show that it is possible to generate radiatively the first and second generation of quark masses and mixings as well as the CKM CP phase. The one-loop supersymmetric contributions to EDMs are automatically zero since all the relevant parameters in the lagrangian are flavor conserving and as a consequence real. The size of the flavor and CP mixing in the susy breaking sector is mostly determined by the fermion mass ratios and CKM elements. We calculate the contributions to epsilon, epsilon^{prime} and to the CP asymmetries in the B decays to psi Ks, phi Ks, eta^{\prime} Ks and Xs gamma. We analyze a case study with maximal predictivity in the fermion sector. For this worst case scenario the measurements of Delta mK, Delta mB and epsilon constrain the model requiring extremely heavy squark spectra.

hep-ph

QLC relation and neutrino mass hierarchy

Latest measurements have revealed that the deviation from a maximal solar mixing angle is approximately the Cabibbo angle, i.e. QLC relation. We argue that it is not plausible that this deviation from maximality, be it a coincidence or not, comes from the charged lepton mixing. Consequently we have calculated the required corrections to the exactly bimaximal neutrino mass matrix ansatz necessary to account for the solar mass difference and the solar mixing angle. We point out that the relative size of these two corrections depends strongly on the hierarchy case under consideration. We find that the inverted hierarchy case with opposite CP parities, which is known to guarantee the RGE stability of the solar mixing angle, offers the most plausible scenario for a high energy origin of a QLC-corrected bimaximal neutrino mass matrix. This possibility may allow us to explain the QLC relation in connection with the origin of the charged fermion mass matrices.

hep-ph

A prediction for U(e3) from patterns in the charged lepton spectra

It is shown that empirical relations between the charged lepton spectra and the quark spectra together with a bimaximal or near bimaximal neutrino mixing matrix necessarily imply that there is a contribution to U(e3) given by thetaC/3/sqrt(2) ~ sqrt(m_{e}/2m_{mu}) ~ 0.052, where thetaC is the Cabibbo angle. This prediction could be tested in the near future reactor experiments. The charged lepton mixing also generates a less robust prediction for the angle theta(23) and a small contribution to the phase delta.

hep-ph

Empirical formulas for the fermion spectra and Yukawa matrices

We present empirical relations that connect the dimensionless ratios of fermion masses for the charged lepton, up-type quark and down-type quark sectors. Explaining these relations from first principles imposes strong constraints on the search for the theory of flavor. We present a simple set of normalized Yukawa matrices, with only two real parameters and one complex phase, which accounts with precision for these mass relations and for the CKM matrix elements and also suggests a simpler parametrization of the CKM matrix. The proposed Yukawa matrices accommodate the measured CP-violation, giving a particular relation between standard model CP-violating phases, beta=Arg(2 - exp^{-i*gamma}). According to this relation, the measured value of beta is close to the maximum value that can be reached. Finally, the particular mass relations with the charged lepton sector find their simplest explanation in the context of grand unified models through the use of the Georgi-Jarlskog factor.

hep-ph

Supersymmetry breaking as the origin of flavor

We present an effective flavor model for the radiative generation of fermion masses and mixings based on a SU(5)xU(2) symmetry. We assume that the original source of flavor breaking resides in the supersymmetry breaking sector. Flavor violation is transmitted radiatively to the fermion Yukawa couplings at low energy through finite supersymmetric threshold corrections. This model can fit the fermion mass ratios and CKM matrix elements, explain the non-observation of proton decay, and overcome present constraints on flavor changing processes through an approximate radiative alignment between the Yukawa and the soft trilinear sector. The model predicts new relations between dimensionless fermion mass ratios in the three fermion sectors, and the quark mixing angles.

hep-ph

Radiative mass generation and suppression of supersymmetric contributions to flavor changing processes

We explore the possibility that the masses for the first two generations of fermions and the quark flavor violation are generated radiatively in the Minimal Supersymmetric Standard Model. We assume that the source of all flavor violation resides in the the supersymmetry breaking sector and is transmitted radiatively to the Standard Model fermion sector through finite corrections at low energy. The approximate radiative alignment between the Yukawa and soft supersymmetry breaking matrices helps to suppress some of the supersymmetric contributions to flavor changing processes, overcoming current experimental constraints. This mechanism may also explain the non-observation of proton decay, since flavor conservation in the superpotential would imply the suppression of dimension five operators in supersymmetric grand unified theories.

hep-ph

Mass predictions based on a supersymmetric SU(5) fixed point

I examine the possibility that the third generation fermion masses are determined by an exact fixed point of the minimal supersymmetric SU(5) model. When one-loop supersymmetric thresholds are included, this unified fixed point successfully predicts the top quark mass, 175 +(-) 2 GeV, as well as the weak mixing angle. The bottom quark mass prediction is sensitive to the supersymmetric thresholds; it approaches the measured value for mu <0 and very large unified gaugino mass. The experimental measurement of the tau lepton mass determines tan(beta), and the strong gauge coupling and fine structure constant fix the unification scale and the unified gauge coupling.

hep-ph

Are supersymmetric models with large tan(beta) natural ?

We point out that, contrary to general belief, generic supersymmetric models are not technically unnatural in the limit of very large values of the parameter tan(beta) when radiative corrections are properly included. Rather, an upper limit on tan(beta) only arises from the requirement that Yukawa couplings remain perturbative up to some high scale. We quantify the relation between this scale and the maximum value of tan(beta). Whereas tan(beta) is limited to lie below 50-70 in the mSUGRA model, models with a much lower scale of new physics (beyond supersymmetry) may have tan(beta) < 150-200.

hep-ph

Supersymmetric SO(10) GUT Models with Yukawa Unification and a Positive Mu Term

Supersymmetric grand unified models based on SO(10) gauge symmetry have many desireable features, including the unification of Yukawa couplings. Using D-term contributions to scalar masses arising from the breakdown of SO(10), Yukawa coupling unification only to 30% can be achieved in models with a positive superpotential Higgs mass. The superparticle mass spectrum is highly constrained, and yields relatively light top squarks and charginos. Surprisingly, the pattern of GUT scale soft SUSY breaking masses are close to those found in the context of inverted hierarchy models. Our analysis supports the idea that the low energy MSSM parameter space is an approximate SO(10) inspired fixed point.

hep-ph

Impact of Muon Anomalous Magnetic Moment on Supersymmetric Models

The recent measurement of a_μ=\frac{g_μ-2}{2} by the E821 Collaboration at Brookhaven deviates from the quoted Standard Model (SM) central value prediction by 2.6σ. The difference between SM theory and experiment may be easily accounted for in a variety of particle physics models employing weak scale supersymmetry (SUSY). Other supersymmetric models are distinctly disfavored. We evaluate a_μfor various supersymmetric models, including minimal supergravity (mSUGRA), Yukawa unified SO(10) SUSY GUTs, models with inverted mass hierarchies (IMH), models with non-universal gaugino masses, gauge mediated SUSY breaking models (GMSB), anomaly-mediated SUSY breaking models (AMSB) and models with gaugino mediated SUSY breaking (inoMSB). Models with Yukawa coupling unification or multi-TeV first and second generation scalars are disfavored by the a_μmeasurement.

hep-ph

Yukawa Unified Supersymmetric SO(10) Model: Cosmology, Rare Decays and Collider Searches

It has recently been pointed out that viable sparticle mass spectra can be generated in Yukawa unified SO(10) supersymmetric grand unified models consistent with radiative breaking of electroweak symmetry. Model solutions are obtained only if $\tanβ\sim 50$, $μ<0$ and positive $D$-term contributions to scalar masses from SO(10) gauge symmetry breaking are used. In this paper, we attempt to systematize the parameter space regions where solutions are obtained. We go on to calculate the relic density of neutralinos as a function of parameter space. No regions of the parameter space explored were actually cosmologically excluded, and very reasonable relic densities were found in much of parameter space. Direct neutralino detection rates could exceed 1 event/kg/day for a $^{73}$Ge detector, for low values of GUT scale gaugino mass $m_{1/2}$. We also calculate the branching fraction for $b\to s γ$ decays, and find that it is beyond the 95% CL experimental limits in much, but not all, of the parameter space regions explored. However, recent claims have been made that NLO effects can reverse the signs of certain amplitudes in the $b\to sγ$ calculation, leading to agreement between theory and experiment in Yukawa unified SUSY models. For the Fermilab Tevatron collider, significant regions of parameter space can be explored via $b\bar{b}A$ and $b\bar{b}H$ searches. There also exist some limited regions of parameter space where a trilepton signal can be seen at TeV33. Finally, there exist significant regions of parameter space where direct detection of bottom squark pair production can be made, especially for large negative values of the GUT parameter $A_0$.

hep-ph

Sparticle Mass Spectra from SO(10) Grand Unified Models with Yukawa Coupling Unification

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 $M_{GUT}\sim 2\times 10^{16}$ GeV. In this model, unification of Yukawa couplings implies a value of $\tanβ\sim 45-55$. At such high values of $\tanβ$, 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 $SU(3)\times SU(2)\times U(1)$. 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 $p\bar{p}$ and $e^+e^-$ colliders.

hep-ph

Basis independent study of Supersymmetry without R-parity and the tau neutrino mass

In the most general R-parity violating model, including both bilinear and trilinear terms, the sneutrino receives a vacuum expectation value. We investigate the constraints on this vev following a basis independent approach, highlighting the relations between the three most popular basis. We study the prediction for the tau neutrino mass which follows from the minimization of the scalar potential in a SUGRA model with universality of the soft parameters at the GUT scale. Finally we show that the tau neutrino mass controls the R-parity violating effects both in the fermionic and scalar sectors.

hep-ph

Supersymmetry Unification Predictions for M_top V_cb and tan(beta)

We study the predictions for M_top, tan(beta) and V_cb in a popular texture ansatze for the fermion mass matrices. We do this both for the Minimal Supersymmetric Standard Model (MSSM) and for the simplest model (MSSM-BRpV) where a bilinear R-Parity violating term is added to the superpotential. We find that taking the experimental values for M_top and V_cb at 99 % C.L. and the GUT relations h_b=h_tau and (V_cb)^2=h_c/h_t within 5 %, the large tan(beta) solution, characteristic in the MSSM with bottom--tau unification, becomes disallowed. In contrast the corresponding allowed region for the MSSM-BRpV is slightly larger. We also find that important modifications occur if we relax the texture conditions at the GUT scale. For example, if the GUT relations are imposed at 40 %, the large tan(beta) branch in the MSSM becomes fully allowed. In addition, in MSSM-BRpV the whole tan(beta)-M_top plane become allowed, finding unification at any value of tan(beta).

hep-ph

Charged Scalar Phenomenology in the Bilinear R-Parity Breaking Model

We consider the charged scalar boson phenomenology in the bilinear R-parity breaking model which induces a mixing between staus and the charged Higgs boson. The charged Higgs boson mass can be lower than expected in the MSSM, even before including radiative corrections. The R-parity violating decay rates can be comparable or even bigger than the R-parity conserving ones. These features could have implications for charged supersymmetric scalar boson searches at future accelerators.

hep-ph