arXiv subjects

Joel W. Walker

Publications and source records attributed to Joel W. Walker.

At least 37 records · Page 2Linked to original sources

arXiv2014

Testing No-Scale Supergravity with the Fermi Space Telescope LAT

We describe a methodology for testing No-Scale Supergravity by the LAT instrument onboard the Fermi Space Telescope via observation of gamma ray emissions from lightest supersymmetric (SUSY) neutralino annihilations. For our test vehicle we engage the framework of the supersymmetric grand unified model No-Scale Flipped $SU(5)$ with extra vector-like flippon multiplets derived from F-Theory, known as $\cal{F}$-$SU(5)$. We show that through compression of the light stau and light bino neutralino mass difference, where internal bremsstrahlung (IB) photons give a dominant contribution, the photon yield from annihilation of SUSY dark matter can be elevated to a number of events potentially observable by the Fermi-LAT in the coming years. Likewise, the increased yield in No-Scale $\cal{F}$-$SU(5)$ may also have rendered the existing observation of a 133 GeV monochromatic gamma ray line visible, if additional data should exclude systematic or statistical explanations. The question of intensity aside, No-Scale $\cal{F}$-$SU(5)$ can indeed provide a natural weakly interacting massive particle (WIMP) candidate with a mass in the correct range to yield $γγ$ and $γZ$ emission lines at $m_χ \sim 133$ GeV and $m_χ \sim 145$ GeV, respectively. Additionally, we elucidate the emerging empirical connection between recent Planck satellite data and No-Scale Supergravity cosmological models which mimic the Starobinsky model of inflation. Together, these experiments furnish rich alternate avenues for testing No-Scale $\cal{F}$-$SU(5)$, and similarly structured models, the results of which may lend independent credence to observations made at the LHC.

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arXiv2013

No-Scale Supergravity in the Light of LHC and Planck

We review the No-Scale F-SU(5) model with extra TeV-scale vector-like flippon multiplets and associated collider phenomenology relating to the search for supersymmetry at the LHC. The model framework possesses the rather unique capacity to provide a light CP-even Higgs boson mass in the favored 124-126 GeV window while simultaneously retaining a testably light Supersymmetry (SUSY) spectrum. We further elucidate the emerging empirical connection between recent Planck satellite data and No-Scale Supergravity cosmological models that mimic the Starobinsky model of inflation, drawing upon work conducted by the conference presenter (DVN) with John Ellis (King's College London/CERN) and Keith Olive (Minnesota).

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arXiv2013

Constricted SUSY from No-Scale F-SU(5): A "Blind Spot" for LHC Top Quark Reconstruction?

We describe a region of the No-Scale F-SU(5) supersymmetric model with TeV-scale vector-like matter multiplets that is potentially opaque to LHC observations based upon top quark reconstruction. Possessing a 100% on-shell branching fraction for gluino to light stop decays, the gluino-light stop mass splitting in F-SU(5) lies very close to the top quark rest mass in the region 810 (650) <~ M(gluino) (M(light stop)) <~ 1170 (975) GeV. For unboosted gluino pair-production, this could render two soft top quarks in the dominant 4-top signature, greatly reducing the likelihood for discrimination from the combinatoric background. We therefore suggest that caution is warranted when gluino exclusion bounds on models possessing a similar spectral character (gluino heavier than the light stop but lighter than all other squarks) using multijet SUSY search tactics. Alternate search methods are highlighted, including those based upon same sign dileptons and multiple heavy flavor tags, which are more sensitive to this delicate kinematic "blind spot" crease.

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arXiv2013

No-Scale F-SU(5) in the Light of LHC, Planck and XENON

We take stock of the No-Scale F-SU(5) model's experimental status and prospects in the light of results from LHC, Planck, and XENON100. Given that no conclusive evidence for light Supersymmetry (SUSY) has emerged from the 7, 8 TeV collider searches, the present work is focused on exploring and clarifying the precise nature of the high-mass cutoff enforced on this model at the point where the stau and neutralino mass degeneracy becomes so tight that cold dark matter relic density observations cannot be satisfied. This hard upper boundary on the model's mass scale constitutes a top-down theoretical mandate for a comparatively light (and testable) SUSY spectrum which does not excessively stress natural resolution of the gauge hierarchy problem. The overlap between the resulting model boundaries and the expected sensitivities of the future 14 TeV LHC and XENON 1-Ton direct detection SUSY / dark matter experiments is described.

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arXiv2013

Correlated Event Excesses in LHC SUSY Searches at 7 & 8 TeV: New Physics or Conspiring Noise?

We examine the ATLAS and CMS 7 & 8 TeV multijet supersymmetry (SUSY) searches requiring the incidence of a single lepton in the framework of the supersymmetric grand unified model No-Scale Flipped SU(5) with extra vector-like flippon multiplets derived from F-Theory, or F-SU(5) for short. Investigated are five multijet+lepton SUSY searches: 4.7/fb ATLAS 7 TeV gluino and light stop searches, as well as 13/fb ATLAS and 9.7/fb CMS 8 TeV light stop searches. Most significantly, all five leptonic SUSY searches represent statistically independent data samples. Findings show that all five orthogonal sets of leptonic LHC observations give a lower bound to the gaugino mass scale at M_{1/2} >= 680 GeV, with all the current best fits correlating within a narrow region. Furthermore, eight statistically independent LHC SUSY search regions (leptonic + all-hadronic) accessible to the No-Scale F-SU(5) model space intersect with all the currently operating beyond the Standard Model experiments within the range of M_{1/2} = 680-850 GeV, with the upper bound established by the lower experimental limit of the anomalous magnetic moment (g_{mu}-2)/2 of the muon. We emphasize that this region of the F-SU(5) model space may not be fully probed by leptonic SUSY searches at the LHC until the 13 TeV LHC energizes in 2015. Additionally, we describe an efficient technique for the effective statistical disentanglement of searches sensitive to mutually overlapping event spaces.

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arXiv2012

The Race for Supersymmetric Dark Matter at XENON100 and the LHC: Stringy Correlations from No-Scale F-SU(5)

The discovery of supersymmetry (SUSY) via action of the cold dark matter candidate is being led on the indirect collider production front by the LHC, and correspondingly by the XENON100 collaboration on the direct detection front. We undertake a dual case study of the specific SUSY signatures which the No-Scale flipped SU(5) x U(1)_X grand unified theory with TeV-scale vector-like particles (No-Scale F-SU(5)) would exhibit at each of these experiments. We demonstrate a correlation between the near-term prospects of these two distinct approaches. We feature a dark matter candidate which is over 99% bino due to a comparatively large Higgs bilinear mass μ-term around the electroweak scale, and thus automatically satisfy the current constraints from the XENON100 and CDMS/EDELWEISS experiments. We do however expect that the ongoing extension of the XENON100 run may effectively probe our model. Likewise, our model is also currently being probed by the LHC via a search for events with ultra-high multiplicity hadronic jets, which are a characteristic feature of the distinctive No-Scale F-SU(5) mass hierarchy.

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arXiv2012

A 125.5 GeV Higgs Boson in F-SU(5): Imminently Observable Proton Decay, A 130 GeV Gamma-ray Line, and SUSY Multijets & Light Stops at the LHC8

We establish that the light Higgs boson mass in the context of the No-Scale Flipped SU(5) GUT with TeV scale vector-like matter multiplets (flippons) is consistent with m_h = 125.5+-0.5 GeV in the region of the best supersymmetry (SUSY) spectrum fit to low statistics data excesses observed by ATLAS in multijet and light stop 5/fb SUSY searches at the LHC7. Simultaneous satisfaction of these disparate goals is achieved by employing a minor decrease in the SU(5) partial unification scale M_{32} to lower the flippon mass, inducing a larger Higgs boson mass shift from the flippon loops. The reduction in M_{32}, which is facilitated by a phenomenologically favorable reduction of the low-energy strong coupling constant, moreover suggests an imminently observable (e|mu)^+ pi^0 proton decay with a central value time scale of 1.7x10^34 years. At the same point in the model space, we find a lightest neutralino mass of m_χ = 145 GeV, which is suitable for the production of 130 GeV monochromatic gamma-rays through annihilations yielding associated Z-bosons; a signal with this energy signature has been identified within observations of the galactic center by the FERMI-LAT Space Telescope. In conjunction with direct correlations to the fate of the ATLAS multijet and light stop production channels presently being tested at the LHC8, we suggest that the reality of a 125.5 GeV Higgs boson affords a particularly rich company of specific and imminently testable associated observables.

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arXiv2012

One-Parameter Model for the Superworld

We review the No-Scale F-SU(5) model with extra TeV-scale vector-like flippon multiplets and its associated collider phenomenology in the search for supersymmetry at the LHC. The model framework possesses the rather unique capacity to provide a light CP-even Higgs boson mass in the favored 124-126 GeV window while simultaneously retaining a testably light SUSY spectrum that is consistent with emerging low-statistics excesses beyond the Standard Model expectation in the ATLAS and CMS multijet data.

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arXiv2012

Primordial Synthesis: F-SU(5) SUSY Multijets, 145-150 GeV LSP, Proton & Rare Decays, 125 GeV Higgs Boson, and WMAP7

We examine the first ATLAS Collaboration 8 TeV 5.8/fb supersymmetry (SUSY) multijet data observations in the context of No-Scale Flipped SU(5) with extra TeV-Scale vector-like flippon multiplets, dubbed F-SU(5), finding that the recent 8 TeV collider data is statistically consistent with our prior 7 TeV results. Furthermore, we synthesize all currently ongoing experiments searching for beyond the Standard Model (BSM) physics with this fit to the 8 TeV data, establishing a suggestive global coherence within a No-Scale F-SU(5) high-energy framework. The SUSY mass scale consistent with all BSM data consists of the region of the F-SU(5) model space within 660 ~< M_{1/2} ~< 760 GeV, which corresponds to sparticle masses of 133 ~< M(chi_1^0) ~< 160 GeV, 725 ~< M(t_1) ~< 845 GeV, and 890 ~< M(g) ~< 1025 GeV. We suggest that the tight non-trivial correspondence between the SUSY multijets, direct and indirect searches for dark matter, proton decay, rare-decay processes, the observed Higgs boson mass, and the measured dark matter relic density, is strongly indicative of a deeper fundamental relationship. We additionally suggest a simple mechanism for enhancing the capture efficiency of F-SU(5) SUSY multijets, which results in a 93% suppression in ATLAS reported background events, but only a 27% decrease in Monte Carlo simulated F-SU(5) multijet events.

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arXiv2012

Correlating LHCb B_s^0 to μ^+ μ^- Results with the ATLAS-CMS Multijet Supersymmetry Search

We show that the No-Scale Flipped SU(5) construction is transparently consistent with recent LHCb results for B_s^0 to μ^+ μ^- decays, due primarily to suppression from the rather small value of tanβ~ 20 that is globally enforced across the model space. This fact should be interpreted in conjunction with the demonstrated evasion of mass limits from the ATLAS and CMS SUSY searches and the more important potential explanation of small observed excesses in the multijet data. The No-Scale Flipped SU(5) benchmark model that best fits these excesses has a gaugino mass scale of M_{1/2} = 708 GeV, which drives masses for the bino-dominated LSP m_χ_1^0 = 143.4 GeV, light stop m_t1 = 786 GeV, gluino m_g = 952 GeV, and heavy squark m_uL = 1490 GeV. The corresponding total prediction for the rare B-decay of Br(B_s^0 to μ^+ μ^-) = 3.5 x 10^-9 suggests that the SUSY contribution may indeed be much smaller than that expected from the Standard Model in this framework, fitting quite comfortably within the very tightly constrained region remaining viable after the most recent LHCb measurements.

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arXiv2012

Testing No-Scale F-SU(5): A 125 GeV Higgs Boson and SUSY at the 8 TeV LHC

We celebrate the recent Higgs discovery announcement with our experimental colleagues at the LHC and look forward to the implications that this success will bring to bear upon the continuing search for supersymmetry (SUSY). The model framework named No-Scale F-SU(5) possesses the rather unique capacity to provide a light CP-even Higgs boson mass in the favored 124-126 GeV window while simultaneously retaining a testably light SUSY spectrum that is consistent with emerging low-statistics excesses beyond the Standard Model expectation in the ATLAS and CMS multijet data. In this letter we review the distinctive F-SU(5) mechanism that forges the physical 125 GeV Higgs boson and make a specific assessment of the ATLAS multijet SUSY search observables that may be expected for a 15/fb delivery of 8 TeV data in this model context. Based on our Monte Carlo study, we anticipate that the enticing hints of a SUSY signal observed in the 7 TeV data could be amplified in the 8 TeV results. Moreover, if the existing signal is indeed legitimate, we project that the rendered gains in significance will be sufficient to conclusively rule out an alternative attribution to statistical fluctuation at that juncture.

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arXiv2012

Supersymmetric Dark Matter at XENON100 and the LHC: No-Scale F-SU(5) Stringy Correlations

We complete an investigation of the observable signatures of No-Scale flipped SU(5) x U(1)_X grand unified theory with TeV-scale vector-like particles (No-Scale F-SU(5)) at the LHC and dark matter direct detection experiments. We feature a dark matter candidate which is over 99% bino due to a comparatively large Higgs bilinear mass mu term around the electroweak scale, and hence automatically satisfy the present constraints from the XENON100 and CDMS/EDELWEISS experiments. We do however expect that the continued XENON100 run and extension to 1-ton may begin to probe our model. Similarly, our model is also currently under probe by the LHC through a search for events with ultra-high multiplicity hadronic jets, which are a characteristic feature of the distinctive No-Scale F-SU(5) mass hierarchy.

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arXiv2012

CutLHCO: A Consumer-Level Tool for Implementing Generic Collider Data Selection Cuts in the Search for New Physics

A new computer program named CutLHCO is introduced, whose function is the implementation of generic data selection cuts on collider event specification files in the standardized .lhco format. This software is intended to fill an open market niche for a lightweight yet flexible "consumer-level" alternative to the ROOT data analysis framework. The primary envisioned application is as a filter on output produced by the PGS4 and DELPHES detector simulations, which are themselves lightweight alternatives to the GEANT4 based solutions favored by the large LHC experiments. All process control instructions are provided via a compact and powerful card file input syntax that efficiently facilitates the reasonable approximation of most event selection strategies and specialized discovery statistics commonly employed by the CMS and ATLAS collaborations. The structure, function, invocation and usage of the most recent CutLHCO 2.0 program version are documented thoroughly, including a detailed deconstruction of several example card file specifications. The associated software is simultaneously being made available for free public download.

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arXiv2012

Non-trivial Supersymmetry Correlations between ATLAS and CMS Observations

We present definite correlations between the CMS 5 \fb all-hadronic search employing the stransverse mass variable $M_{T2}$ and the ATLAS 5 \fb all-hadronic and multijet supersymmetry (SUSY) searches, suggesting the possibility that both the ATLAS and CMS experiments are already registering a faint but legitimate SUSY signal at the LHC. We isolate this prospective mutual productivity beyond the Standard Model in the framework of the supersymmetric No-Scale Flipped $SU$(5) grand unified theory, supplemented with extra vector-like matter (flippons). Evident overproduction is observed in three CMS \mt2 and four ATLAS hadronic and multijet signal regions, where a \x2 fitting procedure of the CMS 5 \fb \mt2 search establishes a best fit SUSY mass in sharp agreement with corresponding ATLAS searches of equivalently heightened signal significance. We believe this correlated behavior across two distinct experiments at precisely the same SUSY mass scale to be highly non-trivial, and potentially indicative of an existing 5 \fb LHC reach into a pervasive physical supersymmetry framework.

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arXiv2012

Chanel No5 (fb^-1): The Sweet Fragrance of SUSY

We present compounding evidence of supersymmetry (SUSY) production at the LHC, in the form of correlations between the nominal 5\fb ATLAS and CMS results for the 7 TeV 2011 run and detailed Monte Carlo collider-detector simulation of a concrete supersymmetric model named No-Scale F-SU(5). Restricting analysis to those event selections which yield a signal significance S/sqrt(B+1) greater than 2, we find by application of the χ^2 statistic that strong correlations exist among the individual search strategies and also between the current best fit to the SUSY mass scale and that achieved using historical 1\fb data sets. Coupled with an appropriately large increase in the "depth" of the χ^2 well with increasing luminosity, we suggest that these features indicate the presence of a non-random structure to the data - a light fragrance perhaps evocative of some fuller coming fruition. Those searches having signal significances below 2 are assembled into a lower exclusion bound on the gaugino mass, which is shown to be consistent with the prior best fit. Assuming the forthcoming delivery of an additional tranche of integrated luminosity at 8 TeV during 2012 that measures on the order 15\fb, we project a sufficiency of actionable data to conclusively judge the merits of our proposal.

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arXiv2012

Unification of Dynamical Determination and Bare Minimal Phenomenological Constraints in No-Scale F-SU(5)

We revisit the construction of the viable parameter space of No-Scale F-SU(5), a model built on the F-lipped SU(5)xU(1)_X gauge group, supplemented by a pair of F-theory derived vector-like multiplets at the TeV scale, and the dynamically established boundary conditions of No-Scale Supergravity. Employing an updated numerical algorithm and a substantially upgraded computational engine, we significantly enhance the scope, detail and accuracy of our prior study. We sequentially apply a set of "bare-minimal" phenomenological constraints, consisting of i) the dynamically established boundary conditions of No-Scale Supergravity, ii) consistent radiative electroweak symmetry breaking, iii) precision LEP constraints on the light supersymmetric mass content, iv) the world average top-quark mass, and v) a light neutralino satisfying the 7-year WMAP cold dark matter relic density measurement. The overlap of the viable parameter space with key rare-process limits on the branching ratio for b to s gamma and the muon anomalous magnetic moment is identified as the "golden strip" of F-SU(5). A cross check for top-down theoretical consistency is provided by application of the "Super No-Scale" condition, which dynamically selects a pair of undetermined model parameters in a manner that is virtually identical to the corresponding phenomenological (driven primarily by the relic density) selection. The predicted vector-like particles are candidates for production at the future LHC, which is furthermore sensitive to a distinctive signal of ultra-high multiplicity hadronic jets. The lightest CP-even Higgs boson mass is predicted to be 120+3.5-1 GeV, with an additional 3-4 GeV upward shift possible from radiative loops in the vector-like multiplets. The predominantly bino flavored lightest neutralino is suitable for direct detection by the Xenon collaboration.

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arXiv2012

A Two-Tiered Correlation of Dark Matter with Missing Transverse Energy: Reconstructing the Lightest Supersymmetric Particle Mass at the LHC

We suggest that non-trivial correlations between the dark matter particle mass and collider based probes of missing transverse energy H_T^miss may facilitate a two tiered approach to the initial discovery of supersymmetry and the subsequent reconstruction of the LSP mass at the LHC. These correlations are demonstrated via extensive Monte Carlo simulation of seventeen benchmark models, each sampled at five distinct LHC center-of-mass beam energies, spanning the parameter space of No-Scale F-SU(5).This construction is defined in turn by the union of the Flipped SU(5) Grand Unified Theory, two pairs of hypothetical TeV scale vector-like supersymmetric multiplets with origins in F-theory, and the dynamically established boundary conditions of No-Scale Supergravity. In addition, we consider a control sample comprised of a standard minimal Supergravity benchmark point. Led by a striking similarity between the H_T^miss distribution and the familiar power spectrum of a black body radiator at various temperatures, we implement a broad empirical fit of our simulation against a Poisson distribution ansatz. We advance the resulting fit as a theoretical blueprint for deducing the mass of the LSP, utilizing only the missing transverse energy in a statistical sampling of >= 9 jet events. Cumulative uncertainties central to the method subsist at a satisfactory 12-15% level. The fact that supersymmetric particle spectrum of No-Scale F-SU(5) has thrived the withering onslaught of early LHC data that is steadily decimating the Constrained Minimal Supersymmetric Standard Model and minimal Supergravity parameter spaces is a prime motivation for augmenting more conventional LSP search methodologies with the presently proposed alternative.

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arXiv2012

A Higgs Mass Shift to 125 GeV and A Multi-Jet Supersymmetry Signal: Miracle of the Flippons at the \sqrt{s} = 7 TeV LHC

We describe a model named No-Scale F-SU(5) which is simultaneously capable of explaining the dual signals emerging at the LHC of i) a 124-126 GeV Higgs boson mass m_h, and ii) tantalizing low-statistics excesses in the multi-jet data which may attributable to supersymmetry. These targets tend to be mutually exclusive in more conventional approaches. The unified mechanism responsible for both effects is the introduction of a rather unique set of vector-like multiplets at the TeV scale, dubbed flippons, which i) can elevate m_h by around 3-4 GeV via radiative loop corrections, and ii) flatten the running of the strong coupling and color-charged gaugino, resulting in a prominent collider signal from production of light gluino pairs. This well motivated theoretical framework maintains consistency with all key phenomenological constraints, and all residual parameterization freedom may in principle be fixed by a combination of the two experiments described. We project that the already collected luminosity of 5 fb^-1 may be sufficient to definitively establish the status of this model, given appropriate data selection cuts.

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