arXiv subjects

Gordon L. Kane

Publications and source records attributed to Gordon L. Kane.

At least 37 records · Page 2Linked to original sources

arXiv2007

LHC String Phenomenology

We argue that it is possible to address the deeper LHC Inverse Problem, to gain insight into the underlying theory from LHC signatures of new physics. We propose a technique which may allow us to distinguish among, and favor or disfavor, various classes of underlying theoretical constructions using (assumed) new physics signals at the LHC. We think that this can be done with limited data $(5-10 fb^{-1})$, and improved with more data. This is because of two reasons -- a) it is possible in many cases to reliably go from (semi)realistic microscopic string construction to the space of experimental observables, say, LHC signatures. b) The patterns of signatures at the LHC are sensitive to the structure of the underlying theoretical constructions. We illustrate our approach by analyzing two promising classes of string compactifications along with six other string-motivated constructions. Even though these constructions are not complete, they illustrate the point we want to emphasize. We think that using this technique effectively over time can eventually help us to meaningfully connect experimental data to microscopic theory.

hep-ph↗

arXiv2006

Connecting (Supersymmetry) LHC Measurements with High Scale Theories

If supersymmetry is discovered at the LHC, the measured spectrum of superpartner masses and couplings will allow us to probe the origins of supersymmetry breaking. However, to connect the collider-scale Lagrangian soft parameters to the more fundamental theory from which they arise, it is usually necessary to evolve them to higher scales. The apparent unification of gauge couplings restricts the possible forms of new physics above the electroweak scale, and suggests that such an extrapolation is possible. Even so, this task is complicated if the low scale spectrum is not measured completely or precisely, or if there is new physics at heavy scales beyond the reach of collider experiments. In this work we study some of these obstacles to running up, and we investigate how to get around them. Our main conclusion is that even though such obstacles can make it very difficult to accurately determine the values of all the soft parameters at the high scale, there exist a number of special combinations of the soft parameters that can avoid these difficulties. We also present a systematic application of our techniques in an explicit example.

hep-ph↗

arXiv2005

Supersymmetry and the LHC Inverse Problem

Given experimental evidence at the LHC for physics beyond the standard model, how can we determine the nature of the underlying theory? We initiate an approach to studying the "inverse map" from the space of LHC signatures to the parameter space of theoretical models within the context of low-energy supersymmetry, using 1808 LHC observables including essentially all those suggested in the literature and a 15 dimensional parametrization of the supersymmetric standard model. We show that the inverse map of a point in signature space consists of a number of isolated islands in parameter space, indicating the existence of "degeneracies"--qualitatively different models with the same LHC signatures. The degeneracies have simple physical characterizations, largely reflecting discrete ambiguities in electroweak-ino spectrum, accompanied by small adjustments for the remaining soft parameters. The number of degeneracies falls in the range 1<d<100, depending on whether or not sleptons are copiously produced in cascade decays. This number is large enough to represent a clear challenge but small enough to encourage looking for new observables that can further break the degeneracies and determine at the LHC most of the SUSY physics we care about. Degeneracies occur because signatures are not independent, and our approach allows testing of any new signature for its independence. Our methods can also be applied to any other theory of physics beyond the standard model, allowing one to study how model footprints differ in signature space and to test ways of distinguishing qualitatively different possibilities for new physics at the LHC.

hep-ph↗

arXiv2005

Is it SUSY?

If a signal for physics beyond the Standard Model is observed at the Tevatron collider or LHC, we will be eager to interpret it. Because only certain observables can be studied at a hadron collider, it will be difficult or impossible to measure masses and spins that could easily establish what physics was being seen. Nevertheless, different underlying physics implies different signatures. We examine the main signatures for supersymmetry, with some emphasis on recognizing supersymmetry in parts of parameter space where generic signatures are reduced or absent. We also consider how to distinguish supersymmetry from alternatives that most closely resemble it, such as Universal Extra Dimensions (UED). Using the robust connection between spins and production cross section, we think it will not be difficult to distinguish UED from supersymmetry. We expect that by considering patterns of signatures it is very likely that it will not be difficult to find a compelling interpretation of any signal of new physics.

hep-ph↗

arXiv2005

The minimal U(1)' extension of the MSSM

Motivated by the apparent need for extending the MSSM and perhaps mitigating naturalness problems associated with the $μ$ parameter and fine-tuning of the soft masses, we augment the MSSM spectrum by a SM gauge singlet chiral superfield, and enlarge the gauge structure by an additional U(1)' invariance, so that the gauge and Higgs sectors are relatively secluded. One crucial aspect of U(1)' models is the existence of anomalies, cancellation of which may require the inclusion of exotic matter which in turn disrupts the unification of the gauge couplings. In this work we pursue the question of canceling the anomalies with a minimal matter spectrum and no exotics. This can indeed be realized provided that U(1)' charges are family-dependent and the soft-breaking sector includes non-holomorphic operators for generating the fermion masses. We provide the most general solutions for U(1)' charges by taking into account all constraints from gauge invariance and anomaly cancellation. We analyze various laboratory and astrophysical bounds ranging from fermion masses to relic density, for an illustrative set of parameters. The U(1)' charges admit patterns of values for which family nonuniversality resides solely in the lepton sector, though this does not generate leptonic FCNCs due to the U(1)' gauge invariance.

hep-ph↗

arXiv2005

Some Phenomenology of Intersecting D-Brane Models

We present some phenomenology of a new class of intersecting D-brane models. Soft SUSY breaking terms for these models are calculated in the u - moduli dominant SUSY breaking approach (in type IIA). In this case, the dependence of the soft terms on the Yukawas and Wilson lines drops out. These soft terms have a different pattern compared to the usual heterotic string models. Phenomenological implications for dark matter are discussed.

hep-ph↗

arXiv2005

Outside the mSUGRA Box

Most studies of the potential for discovery of superpartners at the Fermilab Tevatron or CERN LHC have focused on the so-called mSUGRA (minimal supergravity mediated supersymmetry breaking) model, not because it is well motivated but because it has a minimal number of parameters. If signals are seen that could be superpartners, most analyses will attempt to interpret them in the mSUGRA framework since the needed software and computational tools exist. With only a few signal channels, and initially large statistical and systematic errors, it is very likely that an mSUGRA interpretation will look all right even if it is not. We present an approach to studying any potential signals of new physics in ``inclusive signature space'' that sensitively tests any proposed interpretation, and apply it to the mSUGRA case. The approach also has significant experimental advantages, reducing the sensitivity to jet energy corrections, dependence on beam luminosity, and other systematics. Basically, if one (or more) instances of reported data lies outside certain bounded regions of inclusive signature space characteristic of the physics being tested, that physics is excluded for any parameters. The approach can be used to study supersymmetry breaking and to point to the form of the underlying theory even without detailed measurements of a number of important parameters which will be difficult or impossible to measure at hadron colliders.

hep-ph↗

arXiv2005

What is the Cosmological Significance of a Discovery of Wimps at Colliders or in Direct Experiments?

Although a discovery of wimps either at colliders or in direct experiments would have enormous implications for our understanding of particle physics, it would imply less than one would like about our understanding of the dark matter in the universe or in the galactic halo: it surely is possible that the discovered particles account for only a little of the total dark matter. To establish the cosmological significance of a wimp discovery, their density must be determined. We show that data from neither hadron colliders nor direct detection experiments alone can be sufficient to determine the local or relic density of discovered wimps, even allowing all needed assumptions about cosmology and astrophysics. We provide examples of dark matter models where nearly identical detector or collider signals correspond to very different densities. We show, however, that it may be possible to determine the density of wimps by combining data from both experiments; we present a general method to do this in the case of supersymmetric dark matter, and describe how similar studies could be made for other wimp candidates.

hep-ph↗

arXiv2004

Spontaeneous Symmetry Breaking and Tunneling in de Sitter Space

Motivated by our earlier argument that the apparent large cosmological constant from quantum fluctuations is actually an artifact of not using a full quantum mechanical superposition to determine the ground state in which the universe lives in the de Sitter space at the beginning of inflation, we calculate the tunneling probability for the two-well potential for a scalar field in de Sitter space. We include ocupling of the potential to gravity, and the effective potential from quantum corrections. The results show the eigenstates are the sum and differences of the wavefunctions for the seperate wells, i.e. a full superposition, and the energy levels are split, with tunneling between them determined by the Hawking-Moss instanton and not supressed.

hep-th↗

arXiv2004

High Scale Study of Possible B \to ϕK_S CP Physics

Some rare decay processes are particularly sensitive to physics beyond the Standard Model (SM) because they have no SM tree contributions. We focus on one of these, $B_{d}\to ϕK_{s}$. Our study is in terms of the high scale effective theory, and high scale models for the underlying theory, while previous studies have been focusing on the low scale effective Lagrangian. We examine phenomenologically the high scale parameter space with full calculations, but largely report the results in terms of mass insertion techniques since they are then easily pictured. We also determine the ranges of different mass insertions that could produce large non-SM CP effects. Then we exhibit classes of high scale models that can or cannot provide large non-SM CP effects, thus demonstrating that data on $B_{d}\to ϕK_{s}$ can probe both supersymmetry breaking and the underlying high scale theory and even make relatively direct contact with string-motivated models. We provide a novel and systematic technique to understand the relations between high and low scale parameters from RGE running. We include all constraints from other data, particularly $b\to sγ$ and EDMs.

hep-ph↗

arXiv2004

Perspectives on Issues Beyond the Standard Model

In this opening talk I first describe how we are entering a data-rich era, and what clues we might soon have to physics beyond the SM (on a time scale of several years). Then we turn to a number of the basic issues we hope to explain, and discuss what level of theory may address them, the SM or supersymmetric SM, or string theory, or "other". Next we consider some of the large number of fine-tunings we seem to have, and how they may be clues, focusing on how the fine-tuning of M$_{Z}$ and m$_{h}$ suggest the MSSM needs to be extended as the low scale theory, and on how flavor physics may be a powerful probe of string theory. Finally we examine using benchmark models to study all these issues.

hep-ph↗

arXiv2002

Tasi lectures: weak scale supersymmetry - a top-motivated-bottom-up approach

Introduction, Perspective - since particle physics beyond the SM is presently in an incoherent state, with lots of static, a long introduction is needed, including some history of the supersymmetry revolutions, physics not described by the SM, indirect evidence for low energy supersymmetry and how flavor physics should be approached. Derive the supersymmetric Lagrangian - the superpotential W. Soft supersymmetry breaking - underlying physics - the general soft-breaking Lagrangian - the MSSM. The μopportunity - R-parity conservation. Count of parameters - constraints - measuring the parameters. Connecting the weak and unification scale. Derivation of the Higgs mechanism - in what sense does supersymmetry explain the Higgs physics. The Higgs spectrum - \tanβ, Yukawa couplings, constraints. LEP Higgs physics - Tevatron Higgs physics can confirm the Higgs mechanism and coupling proportional to mass - measurements in the Higgs sector. gluino, Neutralino, Chargino - cannot in general measure \tanβat hadron colliders. Effects of soft phases - all observables, not only CPV ones, g-2, EDMs, gluino phase, LSP CDM, possible connections to stringy physics. Phase structure of simple D-brane models. Tevatron superpartner searches, signatures. Extensions of the MSSM. The importance of low scale supersymmetry is not only that we learn of another profound aspect of our world, but also to provide a window to Planck scale physics, in order to connect string theory and our world.

hep-ph↗

arXiv2002

Supersymmetry and the Cosmic Ray Positron Excess

We explore several supersymmetric alternatives to explain predictions for the cosmic ray positron excess. Light sneutrino or neutralino LSP's, and a fine-tuned model designed to provide a delta-function input, can give adequate statistical descriptions of the reported HEAT data if non-thermal production of the relic cold dark matter density dominates and/or if ``boost factors''(that could originate in uncertainties from propagation or local density fluctuations) to increase the size of the signal are included. All the descriptions can be tested at the Tevatron or LHC, and some in other WIMP detecting experiments.

hep-ph↗

arXiv2001

Implications of Muon g-2 for Supersymmetry and for Discovering Superpartners Directly

We study the implications of interpreting the recent muon g-2 deviation from the Standard Model prediction as evidence for virtual superpartners, with very general calculations that include effects of phases and are consistent with all relevant constraints. The most important result is that there are upper limits on masses: at least one superpartner mass is below about 350 GeV (for the theoretically preferred value of tan(beta)=35) and may be produced at the Fermilab Tevatron in the upcoming run, and there must be chargino, neutralino, and slepton masses below about 600 GeV. In addition, tan(beta) must be larger than about 8.

hep-ph↗

arXiv2001

Proton Decay, Black Holes, and Large Extra Dimensions

We consider proton decay in theories that contain large extra dimensions. If virtual black hole states are allowed by the theory, as is generally the case, then proton decay can proceed via virtual black holes. The experimental limits on the proton lifetime place strong constraints on the quantum gravity scale $\mnew$ (the effective Planck mass). For most theories, our constraint implies a lower bound of $\mnew > 10^{16}$ GeV. The corresponding bound on the size of large extra dimensions is $\ell < 10^{6/n} \times 10^{-30}$ cm, where $n$ is the number of such dimensions. Regrettably, for most theories this limit rules out the possibility of observing large extra dimensions at accelerators or in millimeter scale gravity experiments. Conversely, proton decay could be dominated by virtual black holes, providing an experimental probe to study stringy quantum gravity physics.

hep-ph↗

arXiv2000

The Supersymmetry Soft-breaking Lagrangian - Where Experiment and String Theory Meet

After an introduction recalling that we expect low energy supersymmetry to be part of our description of nature because of considerable indirect evidence and successful predictions, and a discussion of the essential role of data for formulating and testing string theory, these lectures focus on the role of the supersymmetry soft-breaking Lagrangian in connecting experiment and string theory. How to measure tan$β$ and the soft parameters is examined via a number of applications, and the difficulty of measuring tan$β$ at hadron colliders is explained. In each case the important role of soft phases is made explicit, and the true number of parameters is counted. Applications include the chargino and neutralino sectors, the Higgs sector and how its results change when phases are included, measuring the (relative) gluino phase, CP violation in K and B systems and whether all CP violation can be due to soft phases, how to learn if the LSP is the cold dark matter of the universe, and baryogenesis. It is emphasized that the success of supersymmetry in explaining the breaking of electroweak symmetry is probably its most important achievement, and implications of that explanation for superpartner masses are shown. Combining many of these considerations, a further application argues that a lepton collider of total energy 600 GeV with a polarized beam is one we can be confident will do important physics even after LHC. The question of the origins of CP violation, whether the CKM phase can be zero, and the possibility that the soft phases can tell us about compactification and supersymmetry breaking are discussed. Some of the applications and issues are examined in a D-brane based model that can describe the usual collider and dark matter phenomenology, and includes phases and CP violation as well.

hep-ph↗

arXiv2000

Weighing the universe with accelerators and detectors

Suppose the lightest superpartner (LSP) is observed at colliders, and WIMPs are detected in explicit experiments. We point out that one cannot immediately conclude that cold dark matter (CDM) of the universe has been observed, and we determine what measurements are necessary before such a conclusion is meaningful. We discuss the analogous situation for neutrinos and axions; in the axion case we have not found a way to conclude axions are the CDM even if axions are detected.

hep-ph↗

arXiv2000

The Beginning of the End of the Anthropic Principle

We argue that if string theory as an approach to the fundamental laws of physics is correct, then there is almost no room for anthropic arguments in cosmology. The quark and lepton masses and interaction strengths are determined.

astro-ph↗