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Stefan Pokorski

Publications and source records attributed to Stefan Pokorski.

At least 73 records · Page 4Linked to original sources
arXiv2007

Modelling strong interactions and longitudinally polarized vector boson scattering

We study scattering of the electroweak gauge bosons in 5D warped models. Within two different models we determine the precise manner in which the Higgs boson and the vector resonances ensure the unitarity of longitudinal vector boson scattering. We identify three separate scales that determine the dynamics of the scattering process in all cases. For a quite general background geometry of 5D, these scales can be linked to a simple functional of the warp factor. The models smoothly interpolate between a `composite' Higgs limit and a Higgsless limit. By holographic arguments, these models provide an effective description of vector boson scattering in 4D models with a strongly coupled electroweak breaking sector.

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arXiv2006

Moduli stabilization and uplifting with dynamically generated F-terms

We use the F-term dynamical supersymmetry breaking models with metastable vacua in order to uplift the vacuum energy in the KKLT moduli stabilization scenario. The main advantage compared to earlier proposals is the manifest supersymmetric treatment and the natural coexistence of a TeV gravitino mass with a zero cosmological constant. We argue that it is generically difficult to avoid anti de-Sitter supersymmetric minima, however the tunneling rate from the metastable vacuum with zero vacuum energy towards them can be very suppressed. We briefly comment on the properties of the induced soft terms in the observable sector.

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arXiv2006

Tools for Deconstructing Gauge Theories in AdS5

We employ analytical methods to study deconstruction of 5D gauge theories in the AdS5 background. We demonstrate that using the so-called q-Bessel functions allows a quantitative analysis of the deconstructed setup. Our study clarifies the relation of deconstruction with 5D warped theories.

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arXiv2006

Twin SUSY

We construct an extension of the MSSM in which superpartners can naturally be heavier than the electroweak scale. This ``little hierarchy'' of scales is stable because the Higgs arises as a pseudo-Nambu-Goldstone boson in the breaking of an accidental SU(4) symmetry of the Higgs sector. Supersymmetry and the global symmetry combine to forbid logarithmically divergent one-loop contributions to the Higgs mass. The accidental symmetry follows from a simple ``twin'' parity which exchanges the SU(2) sectors in the SU(3)_C x SU(2)_L x SU(2)_R x U(1)_X gauge group.

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arXiv2005

Double protection of the Higgs potential

A mechanism of double protection of the Higgs potential, by supersymmetry and by a global symmetry, is investigated in a class of supersymmetric models with the SU(3)xSU(3)xU(1) gauge symmetry. In such models the electroweak symmetry can be broken with no fine-tuning at all.

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arXiv2005

Flavour violation in general supergravity

We reappraise the flavour changing neutral currents (FCNC) problem in string--derived supergravity models. We overview and classify possible sources of flavour violation and find that the problem often does not arise in classes of models which generate hierarchical Yukawa matrices. In such models, constraints from the K- and D-meson systems leave room for substantial flavour non-universality of the soft terms. The current B-physics experiments only begin to probe its natural range. Correlations among different observables can allow one to read off the chirality structure of flavour violating sources. We briefly discuss the lepton sector where the problem of FCNC is indeed serious and perhaps points at an additional symmetry or flavour universality.

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arXiv2004

Electroweak symmetry breaking in supersymmetric models with heavy scalar superpartners

We propose a novel mechanism of electroweak symmetry breaking in supersymmetric models, as the one recently discussed by Birkedal, Chacko and Gaillard, in which the Standard Model Higgs doublet is a pseudo-Goldstone boson of some global symmetry. The Higgs mass parameter is generated at one loop level by two different, moderately fine-tuned sources of the global symmetry breaking. The mechanism works for scalar superpartner masses of order 10 TeV, but gauginos can be light. The scale at which supersymmetry breaking is mediated to the visible sector has to be low, of order 100 TeV. Fine-tuning in the scalar potential is at least two orders of magnitude smaller than in the MSSM with similar soft scalar masses. The physical Higgs boson mass is (for $\tanβ\gg1$) in the range 120-135 GeV.

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arXiv2004

Patterns of Lepton-Flavour Violation Motivated by Decoupling and Sneutrino Inflation

We present predictions for flavour-violating charged-lepton decays induced by the seesaw mechanism implemented within the constrained minimal supersymmetric standard model (CMSSM) with universal input soft supersymmetry breaking terms. We assume that one heavy singlet neutrino almost decouples from the see-saw mechanism, as suggested by the pattern of light neutrino masses and mixing angles. This is suggested independently by sneutrino inflation with a low reheating temperature, T(RH)<10^7 GeV, so as to avoid overproducing gravitinos. This requirement further fixes the mass of the weakly-coupled sneutrino, whose decays may lead to leptogenesis. We find that BR(mu->e gamma)>10^(-13) but BR(tau->mu gamma)<10^(-9) in the bulk of the acceptable parameter space, apart from a few isolated points. The ratio BR(mu->e gamma)/BR(tau->mu gamma) depends on only one complex parameter, and is particularly interesting to compare with experiment.

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arXiv2003

Deconstructing 5D supersymmetric U(1) gauge theories on orbifolds

We investigate deconstruction of five dimensional supersymmetric abelian gauge theories compactified on $S_1/Z_2$, with various sets of bulk and matter multiplets. The problem of anomalies, chirality and stability in the deconstructed theories is discussed. We find that for most of the 5d brane/bulk matter assignments there exists the deconstructed version. There are, however, some exceptions.

hep-th↗
arXiv2003

Deconstructed U(1) and Supersymmetry Breaking

We discuss supersymmetry breaking induced by simultaneous presence of a Wilson-line type superpotential and boundary-localized Fayet-Iliopoulos terms in a four dimensional theory based on deconstruction of five-dimensional abelian gauge theories on orbifolds. Large hierarchy between the scale of supersymmetry breaking and the fundamental scale can be generated dynamically. The model has several potentially interesting phenomenological applications. We also discuss the conditions that are necessary for interpreting our $U(1)^N$ model as an ultra-violet completion of some 5d theory. In particular, the corresponding 5d theory contains Chern-Simons couplings.

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arXiv2002

Custodial supersymmetry in non-supersymmetric quiver theories

We consider non-supersymmetric quiver theories obtained by orbifolding the N=4 supersymmetric U(K) gauge theory by a discrete Z_Γgroup embedded in the SU(4) R-symmetry group. We explicitly find that in such theories there are no one-loop quadratic divergences in the effective potential. Moreover, when the gauge group U(n)^Γof the quiver theory is spontaneously broken down to the diagonal U(n), we identify a custodial supersymmetry which is responsible for the fermion-boson degeneracy of the mass spectrum.

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arXiv2001

Unification in models with replicated gauge groups

We examine unification of gauge couplings in four dimensional renormalizable gauge theories inspired by the latticized (deconstructed) SM or MSSM in five dimensions. The models are based on replicated gauge groups, spontaneously broken to the diagonal subgroup. The analysis is performed at one-loop level, with the contribution from the heavy vector bosons included, and compared with the analogous results in the SM or MSSM. Unification at or above the diagonal breaking scale is discussed. We find that in the considered class of extensions of the SM(MSSM) unification is possible for a wide range of unification scales and with the similar accuracy as in the SM(MSSM). Unification above the diagonal breaking scale is particularly attractive: it is a consequence of the SM(MSSM) unification, but with the unification scale depending on the number of replications of the gauge group.

hep-ph↗
arXiv2001

The Standard Model in the Latticized Bulk

We construct the manifestly gauge invariant effective Lagrangian in 3+1 dimensions describing the Standard Model in 4+1 dimensions, following the transverse lattice technique. We incorporate split generation fermions and we explore naturalness for two Higgs configurations: a universal Higgs VEV, common to each transverse brane, and a local Higgs VEV centered on a single brane with discrete exponential attenuation to other branes, emulating the split-generation model. Extra dimensions, with explicit Higgs, do not ameliorate the naturalness problem.

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arXiv2001

Gauge Invariant Effective Lagrangian for Kaluza-Klein Modes

We construct a manifestly gauge invariant Lagrangian in 3+1 dimensions for N Kaluza-Klein modes of an SU(m) gauge theory in the bulk. For example, if the bulk is 4+1, the effective theory is Π_{i=1}^{N+1} SU(m)_i with N chiral (\bar{m},m) fields connecting the groups sequentially. This can be viewed as a Wilson action for a transverse lattice in x^5, and is shown explicitly to match the continuum 4+1 compactifed Lagrangian truncated in momentum space. Scale dependence of the gauge couplings is described by the standard renormalization group technique with threshold matching, leading to effective power law running. We also discuss the unitarity constraints, and chiral fermions.

hep-th↗
arXiv2001

Four-Dimensional Supergravities from Five-Dimensional Brane Worlds

We give the explicit form of the four dimensional effective supergravity action, which describes low energy physics of the Randall-Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. The relation between 5d and 4d physics is explicit: the low energy action is derived from the compactification of a locally supersymmetric model in five dimension. The presence of odd $Z_2$ parity scalars in the bulk gives rise to effective potential for the radion in four dimensions. We describe the mechanism of supersymmetry breaking mediation, which relies on non-trivial configuration of these $Z_2$-odd bulk fields. Broken supersymmetry leads to stabilization of the interbrane distance.

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arXiv2000

Five-Dimensional Gauged Supergravities with Universal Hypermultiplet and Warped Brane Worlds

We present five dimensional gauged supergravity with universal hypermultiplet on M_4 \times S^1 / Z_2 coupled supersymmetrically to three-branes located at the fixed points. The construction is extended to the smooth picture with auxiliary singlet and four-form fields. The model admits the Randall-Sundrum solution as a BPS vacuum with vanishing energy. We give the form of all KK-tower modes for fields present in the model.

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arXiv2000

Supersymmetrizing Branes with Bulk in Five-Dimensional Supergravity

We supersymmetrize a class of moduli dependent potentials living on branes with the help of additional bulk terms in 5d N=2 supergravity. The space of Poincare invariant vacuum solutions includes the Randall-Sundrum solution and the $M$-theoretical solution. After adding gauge sectors to the branes we discuss breakdown of low energy supersymmetry in this setup and hierarchy of physical scales. In the limit of large warp factors we find decoupling between effects stemming from different branes in the compactified theory.

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