arXiv subjects

Dimitri V. Nanopoulos

Publications and source records attributed to Dimitri V. Nanopoulos.

At least 91 records · Page 5Linked to original sources

arXiv2014

A No-Scale Framework for Sub-Planckian Physics

We propose a minimal model framework for physics below the Planck scale with the following features: (i) it is based on no-scale supergravity, as favoured in many string compactifications, (ii) it incorporates Starobinsky-like inflation, and hence is compatible with constraints from the Planck satellite, (iii) the inflaton may be identified with a singlet field in a see-saw model for neutrino masses, providing an efficient scenario for reheating and leptogenesis, (iv) supersymmetry breaking occurs with an arbitrary scale and a cosmological constant that vanishes before radiative corrections, (v) regions of the model parameter space are compatible with all LHC, Higgs and dark matter constraints.

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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

No-Scale Supergravity Realization of the Starobinsky Model of Inflation

We present a model for cosmological inflation based on a no-scale supergravity sector with an SU(2,1)/U(1) Kahler potential, a single modulus T and an inflaton superfield Phi described by a Wess-Zumino model with superpotential parameters (mu, lambda). This model yields a scalar spectral index n_s and a tensor-to-scalar ratio r that are compatible with the Planck measurements for values of lambda simeq mu/3M_P. For the specific choice lambda = mu/3M_P, the model is a no-scale supergravity realization of the R+R^2 Starobinsky model.

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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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arXiv2013

Starobinsky-like Inflationary Models as Avatars of No-Scale Supergravity

Models of cosmological inflation resembling the Starobinsky R + R^2 model emerge naturally among the effective potentials derived from no-scale SU(N,1)/SU(N) x U(1) supergravity when N > 1. We display several examples in the SU(2,1)/SU(2) x U(1) case, in which the inflaton may be identified with either a modulus field or a matter field. We discuss how the modulus field may be stabilized in models in which a matter field plays the role of the inflaton. We also discuss models that generalize the Starobinsky model but display different relations between the tilt in the spectrum of scalar density perturbations, n_s, the tensor-to-scalar ratio, r, and the number of e-folds, N_*. Finally, we discuss how such models can be probed by present and future CMB experiments.

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arXiv2013

Electroweak Supersymmetry around the Electroweak Scale

Inspired by the phenomenological constraints, LHC supersymmetry and Higgs searches, dark matter search as well as string model building, we propose the electroweak supersymmetry around the electroweak scale: the squarks and/or gluinos are around a few TeV while the sleptons, sneutrinos, bino and winos are within one TeV. The Higgsinos can be either heavy or light. We consider bino as the dominant component of dark matter candidate, and the observed dark matter relic density is achieved via the neutralino-stau coannihilations. Considering the Generalized Minimal Supergravity (GmSUGRA), we show explicitly that the electroweak supersymmetry can be realized, and the gauge coupling unification can be preserved. With two Scenarios, we study the viable parameter spaces that satisfy all the current phenomenological constraints, and we present the concrete benchmark points. Furthermore, we comment on the fine-tuning problem and LHC searches.

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arXiv2012

The Superluminal Neutrinos from Deformed Lorentz Invariance

We study two superluminal neutrino scenarios where δv\equiv (v-c)/c is a constant. To be consistent with the OPERA, Borexino, and ICARUS experiments and with the SN1987a observations, we assume that δv_ν on the Earth is about three order larger than that on the interstellar scale. To explain the theoretical challenges from the Bremsstrahlung effects and pion decays, we consider the deformed Lorentz invariance, and show that the superluminal neutrino dispersion relations can be realized properly while the modifications to the dispersion relations of the other Standard Model particles can be negligible. In addition, we propose the deformed energy and momentum conservation laws for a generic physical process. In Scenario I the momentum conservation law is preserved while the energy conservation law is deformed. In Scenario II the energy conservation law is preserved while the momentum conservation law is deformed. We present the energy and momentum conservation laws in terms of neutrino momentum in Scenario I and in terms of neutrino energy in Scenario II. In such formats, the energy and momentum conservation laws are exactly the same as those in the traditional quantum field theory with Lorentz symmetry. Thus, all the above theoretical challenges can be automatically solved. We show explicitly that the Bremsstrahlung processes are forbidden and there is no problem for pion decays.

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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

Rare B decays in the flip SU(5) Model

In the testable Flipped $SU(5)\times U(1)_X$ model with TeV-scale vector-like particles from F-theory model building dubbed as the flip SU(5) model, we study the vector-like quark contributions to B physics processes, including the quark mass spectra, Feynman rules, new operators and Wilson coefficients, etc. We focus on the implications of the vector-like quark mass scale on B physics. We find that there exists the $\bar{s}bZ$ interaction at tree level, and the Yukawa interactions are changed. Interestingly, different from many previous models, the effects of vector-like quarks on rare B decays such as $B\to X_sγ$ and $B\to X_s\ell^+\ell^-$ do not decouple in some viable parameter space, especially when the vector-like quark masses are comparable to the charged Higgs boson mass. Under the constraints from $B\to X_sγ$ and $\ B\to X_s\ell^+\ell^-$, the latest measurement for $B_s\to μ^+μ^-$ can be explained naturally, and the branching ratio of $B_s\to \ell^+\ell^-γ$ can be up to $(4\sim5)\times10^{-8}$. The non-decouling effects are much more predictable and thus the \fsu5 model may be tested in the near future experiments.

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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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