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## Electroweak precision constraints on the Lee-Wick standard model

ALVAREZ, Ezequiel; SCHAT, Carlos; ROLD, Leandro Da; SZYNKMAN, Alejandro
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
75.72%
We perform an analysis of the electroweak precision observables in the Lee-Wick Standard Model. The most stringent restrictions come from the S and T parameters that receive important tree level and one loop contributions. In general the model predicts a large positive S and a negative T. To reproduce the electroweak data, if all the Lee-Wick masses are of the same order, the Lee-Wick scale is of order 5 TeV. We show that it is possible to find some regions in the parameter space with a fermionic state as light as 2.4-3.5 TeV, at the price of rising all the other masses to be larger than 5-8 TeV. To obtain a light Higgs with such heavy resonances a fine-tuning of order a few per cent, at least, is needed. We also propose a simple extension of the model including a fourth generation of Standard Model fermions with their Lee-Wick partners. We show that in this case it is possible to pass the electroweak constraints with Lee-Wick fermionic masses of order 0.4-1.5 TeV and Lee-Wick gauge masses of order 3 TeV.

## Linking natural supersymmetry to flavour physics

Dudas, Emilian; von Gersdorff, Gero; Pokorski, Stefan; Ziegler, Robert
Tipo: Artigo de Revista Científica Formato: 34
ENG
Relevância na Pesquisa
75.71%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); With the aim of linking natural supersymmetry to flavour physics, a model is proposed based on a family symmetry G x U(1), where G is a discrete nonabelian subgroup of SU(2), with both F-term and (abelian) D-term supersymmetry breaking. A good fit to the fermion masses and mixing is obtained with the same U(1) charges for the left- and right- handed quarks of the first two families and the right-handed bottom quark, and with zero charge for the left-handed top-bottom doublet and the the right handed top. The model shows an interesting indirect correlation between the correct prediction for the V-ub/V-cb ratio and large right-handed rotations in the (s, b) sector, required to diagonalise the Yukawa matrix. For the squarks, one obtains almost degenerate first two generations. The main source of the FCNC and CP violation effects is the splitting between the first two families and the right-handed sbottom determined by the relative size of F-term and D-term supersymmetry breaking. The presence of the large right-handed rotation implies that the bounds on the masses of the first two families of squarks and the right handed sbottom are in a few to a few tens TeV range. The picture that emerges is light stops and left handed sbottom and much heavier other squarks.

## Linking natural supersymmetry to flavour physics

Dudas, Emilian; von Gersdorff, Gero; Pokorski, Stefan; Ziegler, Robert
Tipo: Artigo de Revista Científica Formato: 34
ENG
Relevância na Pesquisa
75.71%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); With the aim of linking natural supersymmetry to flavour physics, a model is proposed based on a family symmetry G xU(1), where G is a discrete nonabelian subgroup of SU(2), with both F-term and (abelian) D-term supersymmetry breaking. A good fit to the fermion masses and mixing is obtained with the same U(1) charges for the left- and right-handed quarks of the first two families and the right-handed bottom quark, and with zero charge for the left- handed top-bottom doublet and the the right handed top. The model shows an interesting indirect correlation between the correct prediction for the V-ub/V-cb ratio and large right-handed rotations in the (s,b) sector, required to diagonalise the Yukawa matrix. For the squarks, one obtains almost degenerate first two generations. The main source of the FCNC and CP violation effects is the splitting between the first two families and the right-handed sbottom determined by the relative size of F-term and D-term supersymmetry breaking. The presence of the large right-handed rotation implies that the bounds on the masses of the first two families of squarks and the right handed sbottom are in a few to a few tens TeV range. The picture that emerges is light stops and left handed sbottom and much heavier other squarks.

## Sequestering CP Violation and GIM-Violation with Warped Extra Dimensions

Cheung, Clifford; Randall, Lisa; Fitzpatrick, Andrew Liam
Fonte: Institute of Physics Publicador: Institute of Physics
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
75.57%
We propose a model of spontaneous CP violation to address the strong CP problem in warped extra dimensions that relies on sequestering flavor and CP violation. We assume that brane-localized Higgs Yukawa interactions respect a (U(3)) flavor symmetry that is broken only by bulk fermion mass and Yukawa terms. All CP violation arises from the vev of a CP-odd scalar field localized in the bulk. To suppress radiative corrections to (ar{ heta}), the doublet quarks in this model are localized on the IR brane. We calculate constraints from flavor-changing neutral currents (FCNCs), precision electroweak measurements, CKM unitarity, and the electric dipole moments in this model and predict (ar{ heta}) to be at least about (10^{−12}).; Physics

## The kaon semileptonic form factor with near physical domain wall quarks

Boyle, P.; Flynn, J.; Garron, N.; Juttner, A.; Sachrajda, C.; Sivalingam, K.; Zanotti, J.
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.57%
RBC/UKQCD collaboration, P.A. Boyle, J.M. Flynn, N. Garron, A. Jüttner, C.T. Sachrajda, K. Sivalingam, and J.M. Zanotti

## Constraining a class of B-L extended models from vacuum stability and perturbativity

Chakrabortty, Joydeep; Konar, Partha; Mondal, Tanmoy
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.61%
The precise knowledge of the Standard Model Higgs boson and top quark masses and couplings are crucial to understand the physics beyond it. SM like Higgs boson having mass in the range of 123-127 GeV squeezes the parameters for beyond standard model. In recent LHC era many TeV scale neutrino mass models have earned much attention as they pose many interesting phenomenological aspects. We have contemplated B-L extended models which are theoretically well motivated and phenomenologically interesting, and successfully explain neutrino mass generation. In this article we have analysed the detailed structures of the scalar potentials for such models. We have computed the criteria which guarantee that vacuum is bounded from below in all directions. Along with that triviality and perturbativity bounds are also necessitated. Incorporating all such effects we constrain the parameters of such models by performing their renormalization group evolutions.; Comment: References added, version to appear in PRD

## On the two-loop decoupling corrections to tau-lepton and b-quark running masses in the MSSM

Bednyakov, A. V.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.91%
Masses of heavy Standard Model fermions (top-quark, bottom-quark, and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and tau-lepton have the same quantum numbers with respect to SU(2) groupand in the MSSM acquire their masses due to interactions with the same Higgs doublet. As a consequence, for large values of tan beta parameter corresponding Yukawa couplings also become large and together with tan beta can significantly enhance radiative corrections. In the case of b-quark two-loop O(alpha_s^2) contribution to the relation between running bottom-quark mass in QCD and MSSM is known in literature. This paper is devoted to calculation of the NNLO corrections proportional to Yukawa couplings. For the tau-lepton obtained contribution can be considered as a good approximation to the full two-loop result. For the b-quark numerical analysis given in the paper shows that only the sum of strong and Yukawa corrections can play such a role.; Comment: 21 pages...

## Fermion Masses and Anti-grand Unification

Froggatt, C. D.; Nielsen, H. B.; Smith, D. J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.76%
We present an extension of the Standard Model (SM) without supersymmetry, which we use to calculate order of magnitude values for the elements of the mass matrices in the SM. In our model we can fit the 9 quark and lepton masses and 3 mixing angles using only 3 free parameters, with the overall mass scale set by the electroweak interaction. The specific model described here has the anti-grand unified gauge group SMG^3 x U(1)_f at high energies where SMG = SU(3) x SU(2) x U(1) is the SM gauge group. The SM fermions are placed in representations of the full gauge group so that they do not produce any anomalies.It is pointed out that the same results can be obtained in an anomaly free SMG x U(1)^3 model.; Comment: 15 page LaTeX file, uses FEYNMAN.tex; to be published in Physics Letters B

## Grand Unified Yukawa Matrix Ansatz: The Standard Model Fermion Mass, Quark Mixing and CP Violation Parameters

Zhang, Yong-Chao; Zhang, De-Hai
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.85%
We propose a new mass matrix ansatz: At the grand unified (GU) scale, the standard model (SM) Yukawa coupling matrix elements are integer powers of the square root of the GU gauge coupling constant \varepsilon \equiv \sqrt{\alpha_{\text{GU}}}, multiplied by order unity random complex numbers. It relates the hierarchy of the SM ermion masses and quark mixings to the gauge coupling constants, greatly reducing the SM parameters, and can give good fitting results of the SM fermion mass, quark mixing and CP violation parameters. This is a neat but very effective ansatz.; Comment: 4 pages (two columns), by REVTeX 4, 2 tables, no figures, version for publication in CPL

## An Indirect Handle on the Down-Quark Yukawa Coupling

Goertz, Florian
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.7%
To measure the Yukawa couplings of the up and down quarks, Y_{u,d}, seems to be far beyond the capabilities of current and (near) future experiments in particle physics. By performing a general analysis of the potential misalignment between quark masses and Yukawa couplings, we derive predictions for the magnitude of induced flavor-changing neutral currents (FCNCs), depending on the shift in the physical Yukawa coupling of first-generation quarks. We find that a shift of -100% in the down-quark Yukawa Y_d would generically result in ds transitions in conflict with Kaon physics. This could already be seen as evidence for a non-vanishing direct coupling of the down quark to the newly discovered Higgs boson. The non-observation of certain, already well-constrained, processes is thus turned into a powerful indirect measure of physical parameters of the effective Standard-Model, which are so far basically unconstrained from experiment and extremely challenging to access with other methods. In particular, we can already deduce that Y_d should vary at most by ~50% from its Standard Model value, barring an alignment of new physics effects with the SM Yukawa couplings. Such an (orthogonal) alignment scenario is however in general much easier to test at the LHC. Similarly...

## A Microscopic Approach to Quark and Lepton Masses and Mixings

Lampe, Bodo
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.81%
In recent papers a microscopic model for the SM Higgs mechanism has been proposed, and an idea how to determine the 24 quark and lepton masses of all 3 generations has emerged in that framework. This idea is worked out in detail here by accommodating the fermion masses and mixings to microscopic parameters. The top quark mass can be given in terms of the Fermi scale and of certain exchange couplings of isospin vectors obeying a tetrahedral symmetry. The observed hierarchy in the family spectrum is attributed to a natural hierarchy in the microscopic couplings. The neutrinos will be shown to vibrate within the potential valleys of the system, thus retaining very tiny masses. This is related to a Goldstone effect inside the internal dynamics. A discussion of the quark and lepton mixing matrices is also included. The mixing angles of the PMNS matrix are calculated for an example set of parameters, and a value for the CP violating phase is given.; Comment: 37 pages, 4 figures, 2 tables

## The New Minimal Supersymmetric GUT : Spectra, RG analysis and Fermion Fits

Aulakh, Charanjit S.; Garg, Sumit K.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.69%
The supersymmetric SO(10) GUT based on the ${\bf{210\oplus 10\oplus 120\oplus 126\oplus {\bar {126}}}}$ Higgs system provides a minimal framework for the emergence of the R-parity exact MSSM at low energies and a viable supersymmetric seesaw explanation for the observed neutrino masses and mixing angles. We present formulae for MSSM decomposition of the superpotential invariants, tree level light charged fermion effective Yukawa couplings, Weinberg neutrino mass generation operator, and the $d=5,\Delta B=\Delta L \neq 0$ effective superpotential in terms of GUT parameters. We use them to determine fits of the 18 available fermion mass-mixing data in terms of the superpotential parameters of the NMSGUT and SUGRY(NUHM) type soft supersymmetry breaking parameters ($\{m_{\tilde f},m_{1/2},A_0,M^2_{H,\bar H}\}$) specified at the MSSM one loop unification scale $M_X^0=10^{16.33}$ GeV. Our fits are compatible with electroweak symmetry breaking and Unification constraints and yield right-handed neutrino masses in the leptogenesis relevant range : $10^8-10^{13}$ GeV. Matching the SM data requires lowering the strange and down quark Yukawas in the MSSM via large $\tan\beta$ driven threshold corrections and characteristic soft Susy breaking spectra. The Susy spectra have light pure Bino LSP...

## Hierarchical Radiative Quark Mass Matrices with an $U(1)_X$ Horizontal Symmetry Model

García, E.; Hernández-Galeana, A.; Jaramillo, D.; Ponce, W. A.; Zepeda, A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.85%
In a model with a gauge group $G_{SM}\otimes U(1)_X$, where $G_{SM} \equiv SU(3)_C \otimes SU(2)_L \otimes U(1)_Y$ is the standard model gauge group and $U(1)_X$ is a horizontal local gauge symmetry, we propose a radiative generation of the spectrum of quark masses and mixing angles. The assignment of horizontal charges is such that at tree level only the third family is massive. Using these tree level masses and introducing exotic scalars, the light families of quarks acquire hierarchical masses through radiative corrections. The rank three quark mass matrices obtained are written in terms of a minimal set of free parameters of the model, whose values are estimated performing a numerical fit. The resulting quark masses and CKM mixing angles turn out to be in good agreement with the experimental values.; Comment: 10 pages, 5 tables and 3 figures Some comments added to clarify as suggested to publish. Some typing mistakes corrected. Update of Mass and CKM matrix values

## The Dualized Standard Model and its Applications

Chan, HM; Bordes, J; Tsou, ST
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.63%
The Dualized Standard Model offers a natural explanation for Higgs fields and 3 generations of fermions plus a perturbative method for calculating SM parameters. By adjusting only 3 parameters, 14 quark and lepton masses and mixing parameters (including $\nu$ oscillations) are calculated with general good success. Further predictions are obtained in post-GZK air showers and FCNC decays.; Comment: Talk given at ICHEP98, Vancouver, 5 pages, Latex, 3 figures using eps, uses ICHEP98 style file included

## A Predictive SO(10) Scheme for Fermion Masses and Mixings

Babu, K. S.; Shafi, Q.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.71%
We present a predictive scheme for fermion masses and mixings inspired by supersymmetric SO(10) in which the gauge hierarchy problem is resolved without fine tuning the parameters. There are six predictions in the flavor sector, all consistent with the present data. The scheme reproduces the familiar asymptotic relations $m_b=m_\tau$ and $m_dm_sm_b=m_e m_\mu m_\tau$. A new expression for $V_{cb}$ is obtained in terms of the quark masses. The remaining predictions involve the quark mixing angles $V_{us}$ and $V_{ub}$, as well as the parameter tan$\beta$ which turns out to be close to $m_t/m_b$.; Comment: 16 pages, plain LaTeX, 2 figures available on request

## Exact One-Loop Evolution Invariants in the Standard Model

Harrison, P. F.; Krishnan, R.; Scott, W. G.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.76%
Guided by considerations of flavour symmetry, we construct a set of exact Standard Model (SM) renormalisation group evolution invariants which link quark masses and mixing parameters. We examine their phenomenological implications and infer a simple combination of Yukawa coupling matrices which plays a unique role in the SM, suggesting a possible new insight into the observed spectrum of quark masses. Our evolution invariants are readily generalised to the leptons in the case of Dirac neutrinos, but do not appear to be relevant for either quarks or leptons in the MSSM.; Comment: 11 pages, 1 figure

## Particle-Antiparticle Mixing, CP Violation and Rare K and B Decays in a Minimal Theory of Fermion Masses

Buras, Andrzej J.; Girrbach, Jennifer; Ziegler, Robert
Tipo: Artigo de Revista Científica