arXiv subjects

G. L. Kane

Publications and source records attributed to G. L. Kane.

At least 37 records · Page 2Linked to original sources

arXiv2001

Intermediate Scale Supersymmetric Inflation, Matter and Dark Energy

We consider supersymmetric inflation models in which inflation occurs at an intermediate scale and which provide a solution to the $μ$ problem and the strong CP problem. Such models are particularly attractive since inflation, baryogenesis and the relic abundance of cold dark matter are all related by a set of parameters which also affect particle physics collider phenomena, neutrino masses and the strong CP problem. For such models the natural situation is a universe containing matter composed of baryons, massive neutrinos, lightest superpartner cold dark matter, and axions. The present day relic abundances of these different forms of matter are (in principle) calculable from the supersymmetric inflation model together with a measurement of the CMB temperature and the Hubble constant. From these relic abundances one can deduce the amount of the present day dark energy density.

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arXiv2001

Supersymmetry and the positron excess in cosmic rays

Recently the HEAT balloon experiment has confirmed an excess of high-energy positrons in cosmic rays. They could come from annihilation of dark matter in the galactic halo. We discuss expectations for the positron signal in cosmic rays from the lightest superpartner. The simplest interpretations are incompatible with the size and shape of the excess if the relic LSPs evolved from thermal equilbrium. Non-thermal histories can describe a sufficient positron rate. Reproducing the energy spectrum is more challenging, but perhaps possible. The resulting light superpartner spectrum is compatible with collider physics, the muon anomalous magnetic moment, Z-pole electroweak data, and other dark matter searches.

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arXiv2001

Introduction to "The Supersymmetric World: The Beginnings of The Theory"

This is the foreword to the book we edited on the origins and early development of supersymmetry, which has been just issued by World Scientific. This book presents a view on the discovery of supersymmetry and pioneering investigations before summer 1976, mainly in the words of people who participated. It combines anecdotal descriptions and personal reminiscences with more technical summaries of the trailblazers, covering the birth of the theory and its first years -- origin of the idea, four-dimensional field theory realization, and supergravity. The eyewitnesses convey to us the drama of one of the deepest discoveries in theoretical physics in the 20-th century. Contributors: V. Akulov, R. Di Stefano, P. Fayet, S. Ferrara, G.-L. Gervais, N. Koretz-Golfand, E. Likhtman, M. Marinov, A. Neveu, L. O'Raifeartaigh, P. Ramond, B. Sakita, J. Schwarz, M. Sohnius, V. Soroka, J. Strathdee, D. Volkov, J. Wess, P. West.

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arXiv2000

What Will We Learn If a Higgs Boson is Found?

We examine what can be deduced from the discovery of a Higgs boson, focusing on a possible discovery at LEP. The analysis begins with the most general situation where no further constraints can be deduced, and then specializes to include various assumptions. Assuming naturalness, the relatively large mass suggests that one or more of larger $\tan β$, large phase, or extra singlets is present. We discuss the implications of a Higgs mass discovery for the SUSY spectrum, and in particular gluinos and stops. We show that a lighter gluino produceable at the Tevatron remains a likely possibility, in disagreement with a recent claim.

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arXiv2000

Pursuing the origin of electroweak symmetry breaking: a 'Bayesian Physics' argument for a 600 GeV e+e- collider

High-energy data has been accumulating over the last ten years, and it should not be ignored when making decisions about the future experimental program. In particular, we argue that the electroweak data collected at LEP, SLC and Tevatron indicate a light scalar particle with mass less than 500 GeV. This result is based on considering a wide variety of theories including the Standard Model, supersymmetry, large extra dimensions, and composite models. We argue that a high luminosity, 600 GeV e+e- collider would then be the natural choice to feel confident about finding and studying states connected to electroweak symmetry breaking. We also argue from the data that worrying about resonances at multi-TeV energies as the only signal for electroweak symmetry breaking is not as important a discovery issue for the next generation of colliders. Such concerns should perhaps be replaced with more relevant discovery issues such as a Higgs boson that decays invisibly, and ``new physics'' that could conspire with a heavier Higgs boson to accommodate precision electroweak data. An e+e- collider with energy less than about 600 GeV is ideally suited to cover these possibilities.

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arXiv2000

D Branes and Textures

We examine the flavor structure of the trilinear superpotential couplings which can result from embedding the Standard Model within D brane sectors in Type IIB orientifold models, which are examples within the Type I string framework. We find in general that the allowed flavor structures of the Yukawa coupling matrices to leading order are given by basic variations on the "democratic" texture ansatz. In certain interesting cases, the Yukawa couplings have a novel structure in which a single right-handed fermion couples democratically at leading order to three left-handed fermions. We discuss the viability of such a ``single right-handed democracy'' in detail; remarkably, even though there are large mixing angles in the u,d sectors separately, the CKM mixing angles are small. The analysis demonstrates the ways in which the Type I superstring framework can provide a rich setting for investigating novel resolutions to the flavor puzzle.

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arXiv2000

Implications of Supersymmetry Phases for Higgs Boson Signals and Limits

We study the supersymmetry parameter region excluded if no Higgs is found at LEP, and the region allowed if a Higgs boson is found at LEP. We describe the full seven parameter structure of Higgs sector. When supersymmetry phases are included, $\tan β$ greater than or equal to 2 is always allowed, and the lower limit on lightest Higgs mass if no signal is found is about 20% lower than in the Standard Model and about 10% lower than in the MSSM with phases set to 0, $π$

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arXiv2000

Can Flavor-Independent Supersymmetry Soft Phases Be the Source of All CP Violation?

Recently it has been demonstrated that large phases in softly broken supersymmetric theories are consistent with electric dipole moment constraints, and are motivated in some (Type I) string models. Here we consider whether large flavor-independent soft phases may be the dominant (or only) source of all CP violation. In this framework $ε$ and $ε'/ε$ can be accommodated, and the SUSY contribution to the B system mixing can be large and dominant. An unconventional flavor structure of the squark mass matrices (with enhanced super-CKM mixing) is required for consistency with B and K system observables.

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arXiv1999

Effects of Large CP-violating Soft Phases on Supersymmetric Electroweak Baryogenesis

We revisit the results of recent electroweak baryogenesis calculations and include all allowed large CP-violating supersymmetric phases. If the phases are large, the resulting baryon asymmetry can be considerably larger than the observed value $n_B/s \sim 4 \times 10^{-11}$. Much of the asymmetry must therefore be washed out, and we argue that the upper bound on the light Higgs mass is larger than the value reported in previous work.

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arXiv1999

Fine-Tuning Constraints on Supergravity Models

We discuss fine-tuning constraints on supergravity models. The tightest constraints come from the experimental mass limits on two key particles: the lightest CP even Higgs boson and the gluino. We also include the lightest chargino which is relevant when universal gaugino masses are assumed. For each of these particles we show how fine-tuning increases with the experimental mass limit, for four types of supergravity model: minimal supergravity, no-scale supergravity (relaxing the universal gaugino mass assumption), D-brane models and anomaly mediated supersymmetry breaking models. Among these models, the D-brane model is less fine tuned.The experimental propects for an early discovery of Higgs and supersymmetry at LEP and the Tevatron are discussed in this framework.

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arXiv1999

Measuring Gaugino Soft Phases and the LSP Mass At Fermilab

Once superpartners are discovered at colliders, the next challenge will be to determine the parameters of the supersymmetric Lagrangian. We illustrate how the relative phases of the gluino, SU(2), and U(1) gauginos and the Higgsino mass parameter mu can be measured at a hadron collider without ad hoc assumptions about the underlying physics, focusing on Fermilab. We also discuss how the gluino and LSP masses can be measured.

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arXiv1999

Superstring Theory and CP- Violating Phases: Can They Be Related?

We investigate the possibility of large CP- violating phases in the soft breaking terms derived in superstring models. The bounds on the electric dipole moments (EDM's) of the electron and neutron are satisfied through cancellations occuring because of the structure of the string models. Three general classes of four-dimensional string models are considered: (i) orbifold compactifications of perturbative heterotic string theory, (ii) scenarios based on Hořava-Witten theory, and (iii) Type I string models (Type IIB orientifolds). Nonuniversal phases of the gaugino mass parameters greatly facilitate the necessary cancellations among the various contributions to the EDM's; in the overall modulus limit, the gaugino masses are universal at tree level in both the perturbative heterotic models and the Hořava-Witten scenarios, which severely restricts the allowed regions of parameter space. Nonuniversal gaugino masses do arise at one-loop in the heterotic orbifold models, providing for corners of parameter space with ${\cal O}(1)$ phases consistent with the phenomenological bounds. However, there is a possibility of nonuniversal gaugino masses at tree level in the Type I models, depending on the details of the embedding of the SM into the D- brane sectors. We find that in a minimal model with a particular embedding of the Standard Model gauge group into two D- brane sectors, viable large phase solutions can be obtained over a wide range of parameter space.

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arXiv1999

A Resolution to the Supersymmetric CP Problem with Large Soft Phases via D-branes

We examine the soft supersymmetry breaking parameters that result from various ways of embedding the Standard Model (SM) on D-branes within the Type I string picture, allowing the gaugino masses and $μ$ to have large CP- violating phases. One embedding naturally provides the relations among soft parameters to satisfy the electron and neutron electric dipole moment constraints even with large phases, while with other embeddings large phases are not allowed. The string models provide some motivation for large phases in the soft breaking parameters. The results generally suggest how low energy data might teach us about Planck scale physics.

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arXiv1999

Naturalness Implications of LEP Results

We analyse the fine-tuning constraints arising from absence of superpartners at LEP, without strong universality assumptions. We show that such constraints do not imply that charginos or neutralinos should have been seen at LEP, contrary to the usual arguments. They do however imply relatively light gluinos $(m_{\tilde g} \lsim 350 GeV)$ and/or a relation between the soft-breaking SU(3) gaugino mass and Higgs soft mass $m_{H_U}$. The LEP limit on the Higgs mass is significant, especially at low $\tan β$, and we investigate to what extent this provides evidence for both a lighter gluino and correlations between soft masses.

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arXiv1999

Nearly Degenerate Neutrinos and Broken Flavour Symmetry

Theories with non-Abelian flavour symmetries lead at zeroth order to neutrino degeneracy and massless charged fermions. The flavour symmetry is spontaneously broken sequentially to give hierarchies $Δm_{atm}^2 \gg Δm_{\odot}^2$ and $m_τ\gg m_μ\gg m_e$, and a misalignment of the vacuum between neutrino and charged sectors gives large $θ_{atm}$. Explicit models are given which determine $θ_{atm} = 45^\circ$. A similar construction gives vacuum misalignment for the lighter generations and gives a vanishing $ββ_{0 ν}$ rate, so that there is no laboratory constraint on the amount of neutrino hot dark matter in the universe, and the solar mixing angle is also maximal, $θ_\odot = 45^\circ$.

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arXiv1998

Electric Dipole Moments Do Not Require the CP-violating Phases of Supersymmetry To Be Small

We report the first fully general numerical calculation of the neutron and electron dipole moments, including the seven significant phases. We find that there are major regions in the parameter space where none of the phases are required to be small, contrary to the conventional wisdom. The electric dipole moments (EDM's) do provide useful constraints, allowing other regions of parameter space to be carved away. We keep all superpartner masses light so agreement with experimental limits arises purely from interesting relations among soft breaking parameters.

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arXiv1998

Measuring the Supersymmetry Lagrangian

The parameters of the supersymmetry Lagrangian are the place where experiment and theory will meet. We show that measuring them is harder than has been thought, particularly because of large unavoidable dependences on phases. Measurements are only guaranteed if a lepton collider with a polarized beam and sufficient energy to produce the relevant sparticles is available. Current limits on superpartner masses, WIMPs, and the supersymmetric Higgs are not general, and need re-evaluation. We also tentatively define the MRM (Minimum Reasonable Model), whose parameters may be measurable at LEP, FNAL and LHC.

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arXiv1997

Recognizing Superpartners at LEP

There is a class of supersymmetric models which is well-motivated by hints of evidence for SUSY and consistent with all existing data. It is important to study the predictions of these models. They are characterized by M(N3) > M(C1) > M(snu) > M(N1) (where Ni and Ci are neutralino and chargino mass eigenstates), |mu| ~< M1 ~< M2 ~= M(Z), mu < 0, and tan(beta) near 1. Their LEP signatures are mostly unusual. Most produced superpartners are invisible! A good signature is two photons plus large missing energy. There are also excess events at large recoil mass in the single photon plus nothing channel. We list the main signatures for charginos, stops, etc., which are also likely to be unconventional. This class of models will be definitively tested at LEP194 with 100 pb^{-1} per detector, and almost definitively tested at LEP184.

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