arXiv subjects

Ilja Dorsner

Publications and source records attributed to Ilja Dorsner.

34 records · Page 2Linked to original sources

arXiv2007

Upper Bound on the Mass of the Type III Seesaw Triplet in an SU(5) Model

We investigate correlation between gauge coupling unification, fermion mass spectrum, proton decay, perturbativity and ultraviolet cutoff within an SU(5) grand unified theory with minimal scalar content and an extra adjoint representation of fermions. We find strong correlation between the upper bound on the mass of both the bosonic and fermionic SU(2) triplets and the cutoff. The upper bound on the mass of fermionic triplet responsible for Type III seesaw mechanism is 10^{2.1} GeV for the Planck scale cutoff. In that case both the idea of grand unification and nature of seesaw mechanism could be tested at future collider experiments through the production of those particles. Moreover, the prediction for the proton decay lifetime is at most an order of magnitude away from the present experimental limits. If the cutoff is lowered these predictions change significantly. In the most general scenario, if one does (not) neglect a freedom in the quark and lepton mixing angles, the upper bound on the fermionic triplet mass is at 10^{5.4} GeV (10^{10} GeV). Since the predictions of the model critically depend on the presence of the higher-dimensional operators and corresponding cutoff we address the issue of their possible origin and also propose alternative scenarios that implement the hybrid seesaw framework of the original proposal.

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arXiv2007

Fermion Masses and the UV Cutoff of the Minimal Realistic SU(5)

We investigate the predictions for fermion masses in the minimal realistic non-supersymmetric SU(5) model with the Standard Model matter content. The possibility to achieve b-τunification is studied taking into account all relevant effects. In addition, we show how to establish an upper bound on the ultraviolet cutoff Λof the theory which is compatible with the Yukawa couplings at the grand unified scale and proton decay. We find Λ\simeq 10^{17} GeV, to be considered a conservative upper bound on the cutoff. We also provide up-to-date values of all the fermions masses at the electroweak scale.

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arXiv2007

On Unification and Nucleon Decay in Supersymmetric Grand Unified Theories Based on SU(5)

We investigate the unification constraints in the minimal sypersymmetric grand unified theories based on SU(5) gauge symmetry. The most general constraints on the spectrum of minimal supersymmetric SU(5) and flipped SU(5) are shown. The upper bound on the mass of the colored Higgs mediating proton decay is discussed in detail in the context of the minimal supersymmetric SU(5). In the case of the minimal SUSY SU(5) we show that if we stick to the strongest bound on the colored triplet mass coming from dimension five proton decay contributions there is no hope to test this model at future nucleon decay experiments through the dimension six operators. We find a lower bound on the partial proton decay lifetime for all relevant channels in the context of flipped SUSY SU(5). We conclude that flipped SUSY SU(5) might be in trouble if proton decay is found at the next generation of experiments with a lifetime below 10^{37} years.

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arXiv2006

Unification versus proton decay in SU(5)

We investigate unification constraints in the simplest renormalizable non-supersymmetric SU(5) framework. We show that in the scenario where the Higgs sector is composed of the 5, 24, and 45 dimensional representations the proton could be practically stable. We accordingly demonstrate that of all the SU(5) scenarios only the non-renormalizable one with the 5, 24, and 15 dimensional Higgs multiplets can be verify if low-energy supersymmetry is not realized in Nature.

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arXiv2006

Minimal Realistic SU(5) Scenario

We present phenomenological aspects of the simplest realistic SU(5) grand unified theory--the theory with the 5, 15, and 24 dimensional representations in the Higgs sector. We show that a successful gauge coupling unification sets experimentally accessible upper bound on the total proton decay lifetime. It also relates proton decay lifetime to scalar leptoquark mass in an experimentally testable manner. We also discuss an addition of gauge singlets--both fermions and bosons--to the simplest scenario and comment on relevant phenomenological consequences of such modifications.

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arXiv2005

Phenomenological and Cosmological Aspects of a Minimal GUT Scenario

Several phenomenological and cosmological aspects of a minimal extension of the Georgi-Glashow model, where the Higgs sector is composed by 5_H, 15_H, and 24_H, are studied. It is shown that the constraints coming from the unification of gauge interactions up to two-loop level predict light scalar leptoquarks. In this GUT scenario, the upper bound on the total proton decay lifetime is tau_p < 1.4 x 10^36 years. The possibility to explain the matter-antimatter asymmetry in the universe through the decays of SU(2)_L scalar triplets is also studied. We find that a successful triplet seesaw leptogenesis implies an upper bound on the scalar leptoquark mass, M_Phib < 10^{6-7} GeV. We conclude that this GUT scenario can be tested at the next generation of proton decay experiments and future colliders through the production of scalar leptoquarks.

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arXiv2005

A Prediction from the Type III See-saw Mechanism

A simple ansatz that is well-motivated by group-theoretical considerations is proposed in the context of the type III neutrino see-saw mechanism. It results in predictions for m_s/m_b and m_b/m_tau that relate these quantities to the masses and mixings of neutrinos.

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arXiv2005

How Long Could We Live?

We investigate model independent upper bounds on total proton lifetime in the context of Grand Unified Theories with the Standard Model matter content. We find them to be $τ_p \leq 1.5^{+0.5}_{-0.3} \times 10^{39} \ \frac{(M_X/10^{16} \textrm{GeV})^4}{α_{GUT}^2} (0.003 \textrm{GeV}^3 / α)^2 \textrm{years}$ and $τ_p \leq 7.1^{+0.0}_{-0.0} \times 10^{36} \ \frac{(M_X/10^{16} \textrm{GeV})^4}{α_{GUT}^2} (0.003 \textrm{GeV}^3 / α)^2 \textrm{years}$ in the Majorana and Dirac neutrino case, respectively. These bounds, in conjunction with experimental limits, put lower limit on the mass $M_X$ of gauge bosons responsible for the proton and bound-neutron decay processes. For central values of relevant input parameters we obtain $M_X \geq 4.3 \times 10^{14} \sqrt{α_{GUT}} \textrm{GeV}$. Our result implies that a large class of non-supersymmetric Grand Unified models, with typical values $α_{GUT} \sim 1/39$, still satisfies experimental constraints on proton lifetime. Our result is independent on any CP violating phase and the only significant source of uncertainty is associated with imprecise knowledge of $α$--the nucleon decay matrix element.

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arXiv2005

Unification without supersymmetry: neutrino mass, proton decay and light leptoquarks

We investigate predictions of a minimal realistic non-supersymmetric SU(5) grand unified theory. To accomplish unification and generate neutrino mass we introduce one extra Higgs representation--a 15 of SU(5)--to the particle content of the minimal Georgi-Glashow scenario. Generic prediction of this setup is a set of rather light scalar leptoquarks. In the case of the most natural implementation of the type II see-saw mechanism their mass is in the phenomenologically interesting region (O(10^2--10^3) GeV). As such, our scenario has a potential to be tested at the next generation of collider experiments, particularly at the Large Hadron Collider (LHC) at CERN. The presence of the 15 generates additional contributions to proton decay which, for light scalar leptoquarks, can be more important than the usual gauge d=6 ones. We exhaustively study both and show that the scenario is not excluded by current experimental bounds on nucleon lifetimes.

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arXiv2004

Could we rotate proton decay away?

In this work we investigate the possibility to completely rotate away proton decay. We show that by choosing specific mass matrices for fermions it is possible to accomplish this in flipped SU(5).

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arXiv2004

Distinguishing between SU(5) and flipped SU(5)

We study in detail the d=6 operators for proton decay in the two possible matter unification scenarios based on SU(5) gauge symmetry. We investigate the way to distinguish between these two scenarios. The dependence of the branching ratios for the two body decays on the fermion mixing is presented in both cases. We point out the possibility to make a clear test of flipped SU(5) through the decay channel p \to π^+ \barν, and the ratio τ(p \to K^0 e^+_α) / τ(p \to π^0 e^+_α).

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arXiv2002

Unifying flipped SU(5) in five dimensions

It is shown that embedding a four-dimensional flipped SU(5) model in a five-dimensional SO(10) model, preserves the best features of both flipped SU(5) and SO(10). The missing partner mechanism, which naturally achieves both doublet-triplet splitting and suppression of d=5 proton decay operators, is realized as in flipped SU(5), while the gauge couplings are unified as in SO(10). The masses of down quarks and charged leptons, which are independent in flipped SU(5), are related by the SO(10). Distinctive patterns of quark and lepton masses can result. The gaugino mass M_1 is independent of M_3 and M_2, which are predicted to be equal.

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arXiv2002

Flavon exchange effects in models with abelian flavor symmetry

In models with abelian flavor symmetry the small mixing angles and mass ratios of quarks and leptons are typically given by powers of small parameters characterizing the spontaneous breaking of flavor symmetry by "flavon" fields. If the scale of the breaking of flavor symmetry is near the weak scale, flavon exchange can lead to interesting flavor-violating and CP violating effects. These are studied. It is found that d_e, mu -> e + gamma, and mu-e conversion on nuclei can be near present limits. For significant range of parameters mu-e conversion can be the most sensitive way to look for such effects.

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arXiv2001

Obtaining the large angle MSW solution to the solar neutrino problem in models

The large mixing angle (LMA) MSW solution to the solar neutrino problem seems favored by the data at the moment over the small mixing angle (SMA) MSW solution and the vacuum (VAC) solution. In this paper the various main types of models of neutrino masses and mixings are studied from the point of view of how naturally they can give the LMA solution. Special attention is given to a very simple type of "lopsided" SU(5) model.

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arXiv2001

A General Classification of Three-Neutrino Models and U_e3

A classification of models with three light neutrinos is given. This classification includes virtually all of the three-neutrino models proposed in the last few years, of which there are approximately one hundred. The essential ideas, attractive features, and characteristic problems of the different classes of model are discussed. The classification is based principally on how the large ν_μ - ν_τ mixing is obtained. A general discussion of the mixing parameter U_{e3} is then given, showing what values are to be expected for it in each type of model.

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arXiv2000

The scaling of lepton dipole moments with lepton mass

The dipole moments of the leptons and quarks are matrices in flavor space, which can potentially reveal as much about the flavor structure of the theory as do the mass matrices. The off-diagonal elements of the dipole matrices lead to flavor-changing decays such as μ-> e γ, while the imaginary parts of the diagonal elements give rise to electric dipole moments. We analyze the scaling of the leptonic dipole moments with the lepton masses in theories beyond the standard model. While in many models the dipole moments scale roughly as lepton mass, it is shown that simple models exist in which the dipoles scale as the cube of the mass or in other ways. An explicit example with cubic scaling is presented, which is motivated on independent grounds from large angle neutrino oscillation data. Our results have great significance for the observability of the electric dipole moments of e, μand τ, and the rare decays μ-> e γ, and τ-> μγand will be tested in several forthcoming experiments.

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