Searcharxiv⌕ Search

arXiv subjects

Joel W. Walker

Publications and source records attributed to Joel W. Walker.

54 records · Page 3Linked to original sources
arXiv2012

A Multi-Axis Best Fit to the Collider Supersymmetry Search: The Aroma of Stops and Gluinos at the \sqrt{s} = 7 TeV LHC

In Profumo di SUSY, we presented evidence that CMS&ATLAS may have already registered a handful of deftly camouflaged supersymmetry events at the LHC in the multijet channels. Here, we explore the prospect for corroboration of this suggestion from 5 additional CMS&ATLAS search strategies targeting the production of light stops & gluinos at lower jet counts, which variously depend on heavy flavor tagging and the inclusion or exclusion of associated leptons. The current operating phase of the 7TeV LHC is highly conducive to the production of gluinos & light stops, given the supersymmetric particle mass hierarchy M_t_1<M_g<M_q that naturally evolves from the dynamics of the model named No-Scale FSU5 that we presently study. Moreover, some tension persists against the SM data-driven and MC generated background predictions in certain LHC searches of this variety. We demonstrate that the 1-sigma overlap of the allowed supersymmetric event production for these seven search methodologies roundly envelops the most favorable phenomenological subspace of FSU5, while handily generating a 125GeV Higgs boson mass. In order to test the statistical significance of any correlations across the simulated FSU5 collider response in these seven search strategies, we implement a multi-axis chi^2 fitting procedure, yielding a best overall match in the vicinity of M1/2=610GeV, corresponding to light stop & gluino masses of approximately 665GeV and 830GeV. Consequently, we suggest that FSU5 is a better global fit to the studied LHC data than the SM alone, and moreover that its predictions appear to be meaningfully correlated with observed low-statistics excesses across a wide variety of specialized search strategies. We suspect the already collected 5/fb will be sufficient to either condense or disperse the delicate aroma of stops and gluinos that suffuses the early search.

hep-ph↗
arXiv2012

Prospects for Discovery of Supersymmetric No-Scale F-SU(5) at The Once and Future LHC

We present the reach of the Large Hadron Collider (LHC) into the parameter space of No-Scale F-SU(5), starting our analysis with the current operating energy of \sqrt{s} = 7 TeV, and extending it on through the bright future of a 14 TeV beam. No-Scale F-SU(5) is a model defined by the confluence of the F-lipped 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. When searching for a five standard deviation signal, we find that the CMS experiment at the \sqrt{s} = 7 TeV LHC began to penetrate the phenomenologically viable parameter space of this model at just under 1/fb of integrated luminosity, and that the majority of this space remains intact, subsequent to analyses of the first 1.1/fb of CMS data. On the contrary, the ATLAS experiment had not reached the F-SU(5) parameter space in its first 1.34/fb of luminosity. Since the CMS and ATLAS detectors have now each amassed a milestone of 5/fb of collected luminosity, the current LHC is presently effectively probing No-Scale F-SU(5). Upon the crossing of the 5/fb threshold, the 7 TeV LHC will have achieved five standard deviation discoverability for a unified gaugino mass of up to about 532 GeV, a light stop of 577 GeV, a gluino of 728 GeV, and heavy squarks of just over 1 TeV. Extending the analysis to include a future LHC center-of-mass beam energy of \sqrt{s} = 14 TeV, the full model space of No-Scale F-SU(5) should be visible to CMS at about 30/fb of integrated luminosity. We stress that the F-SU(5) discoverability thresholds discussed here are contingent upon retaining only those events with nine jets or more for the CMS experiment and seven jets or more for the ATLAS experiment.

hep-ph↗
arXiv2012

Natural Predictions for the Higgs Boson Mass and Supersymmetric Contributions to Rare Processes

In the context of No-Scale F-SU(5), a model defined by the convergence of the F-lipped 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, we predict that the lightest CP-even Higgs boson mass lies within the range of 119.0 GeV to 123.5 GeV, exclusive of the vector-like particle contribution to the mass. With reports by the CMS, ATLAS, CDF, and D0 Collaborations detailing enticing statistical excesses in the vicinity of 120 GeV in searches for the Standard Model Higgs boson, all signs point to an imminent discovery. While basic supersymmetric constructions such as mSUGRA and the CMSSM have already suffered overwhelming reductions in viable parameterization during the LHC's initial year of operation, about 80% of the original No-Scale F-SU(5) model space remains viable after analysis of the first 1.1 fb^{-1} of integrated luminosity. This model is moreover capable of handily explaining the small excesses recently reported in the CMS multijet supersymmetry search, and also features a highly favorable "golden" subspace which may simultaneously account for the key rare process limits on the muon anomalous magnetic moment (g - 2) and the branching ratio of the flavor-changing neutral current decay b to sγ. In addition, the isolated mass parameter responsible for the global particle mass normalization, the gaugino boundary mass M_{1/2}, is dynamically determined at a secondary local minimization of the minimum of the Higgs potential V_{min}, in a manner which is deeply consistent with all precision measurements at the physical electroweak scale.

hep-ph↗
arXiv2012

Blueprints of the No-Scale Multiverse at the LHC

We present a contemporary perspective on the String Landscape and the Multiverse of plausible string, M- and F-theory vacua. In contrast to traditional statistical classifications and capitulation to the anthropic principle, we seek only to demonstrate the existence of a non-zero probability for a universe matching our own observed physics within the solution ensemble. We argue for the importance of No-Scale Supergravity as an essential common underpinning for the spontaneous emergence of a cosmologically flat universe from the quantum "nothingness". Concretely, we continue to probe the phenomenology of a specific model which is testable at the LHC and Tevatron. Dubbed No-Scale F-SU(5), it represents the intersection of the Flipped SU(5) Grand Unified Theory (GUT) with extra TeV-Scale vector-like multiplets derived out of F-theory, and the dynamics of No-Scale Supergravity, which in turn imply a very restricted set of high energy boundary conditions. By secondarily minimizing the minimum of the scalar Higgs potential, we dynamically determine the ratio tan β\simeq 15-20 of up- to down-type Higgs vacuum expectation values (VEVs), the universal gaugino boundary mass M_{1/2} \simeq 450 GeV, and consequently also the total magnitude of the GUT-scale Higgs VEVs, while constraining the low energy Standard Model gauge couplings. In particular, this local minimum minimorum lies within the previously described "golden strip", satisfying all current experimental constraints. We emphasize, however, that the overarching goal is not to establish why our own particular universe possesses any number of specific characteristics, but rather to tease out what generic principles might govern the superset of all possible universes.

hep-ph↗
arXiv2011

Profumo di SUSY: Suggestive Correlations in the ATLAS and CMS High Jet Multiplicity Data

We present persistently amassing evidence that the CMS and ATLAS Collaborations may indeed be already registering supersymmetry events at the Large Hadron Collider (LHC). Our analysis is performed in the context of a highly phenomenologically favorable model named No-Scale F-SU(5), which represents the unification of the F-lipped SU(5) Grand Unified Theory (GUT), two pairs of hypothetical TeV-scale vector-like supersymmetric multiplets derived out of F-Theory, and the dynamically established boundary conditions of No-Scale supergravity. We document highly suggestive correlations between the first inverse femtobarn of observations by CMS and ATLAS, where seductive excesses in multijet events, particularly those with nine or more jets, are unambiguously accounted for by a precision Monte-Carlo simulation of the F-SU(5) model space. This intimate correspondence is optimized by a unified gaugino mass in the neighborhood of M_{1/2}=518 GeV. We supplement this analysis by extrapolating for the expected data profile to be realized with five inverse femtobarns of integrated luminosity, as expected to be observed at the LHC by the conclusion of 2011. Significantly, we find that this luminosity may be sufficient to constitute a SUSY discovery for the favored benchmark spectrum. Indeed, the winds wafting our way from Geneva may already be heavy with the delicate perfume of Supersymmetry.

hep-ph↗
arXiv2011

The F-Landscape: Dynamically Determining the Multiverse

We evolve our Multiverse Blueprints to characterize our local neighborhood of the String Landscape and the Multiverse of plausible string, M- and F-theory vacua. Building upon the tripodal foundations of i) the Flipped SU(5) Grand Unified Theory (GUT), ii) extra TeV-Scale vector-like multiplets derived out of F-theory, and iii) the dynamics of No-Scale Supergravity, together dubbed No-Scale F-SU(5), we demonstrate the existence of a continuous family of solutions which might adeptly describe the dynamics of distinctive universes. This Multiverse landscape of F-SU(5) solutions, which we shall refer to as the F-Landscape, accommodates a subset of universes compatible with the presently known experimental uncertainties of our own universe. We show that by secondarily minimizing the minimum of the scalar Higgs potential of each solution within the F-Landscape, a continuous hypervolume of distinct minimum minimorum can be engineered which comprise a regional dominion of universes, with our own universe cast as the bellwether. We conjecture that an experimental signal at the LHC of the No-Scale F-SU(5) framework's applicability to our own universe might sensibly be extrapolated as corroborating evidence for the role of string, M- and F-theory as a master theory of the Multiverse, with No-Scale supergravity as a crucial and pervasive reinforcing structure.

hep-ph↗
arXiv2011

Super No-Scale F-SU(5): A Dynamic Determination of M_{1/2} and tan beta

We study the Higgs potential in No-Scale F-SU(5), a model built on the tripodal foundations of the Flipped SU(5) x U(1)_X Grand Unified Theory, extra F-theory derived TeV scale vector-like particle multiplets, and the high scale boundary conditions of No-Scale Supergravity. V_min, the minimum of the potential following radiative electroweak symmetry breaking, is a function at fixed Z-Boson mass of the universal gaugino boundary mass M_{1/2} and tanβ, the ratio of Higgs vacuum expectation values. The No-Scale nullification of the bilinear Higgs soft term B_mu at the boundary reduces V_min(M_{1/2}) to a one dimensional dependency, which may be secondarily minimized. This "Super No-Scale" condition dynamically fixes tan beta and M_{1/2} at the local minimum minimorum of V_min. Fantastically, the walls of this theoretically established secondary potential coalesce in descent to a striking concurrency with the previously phenomenologically favored "golden point" and "golden strip".

hep-ph↗
arXiv2011

Has SUSY Gone Undetected in 9-jet Events? A Ten-Fold Enhancement in the LHC Signal Efficiency

On the heels of the first analysis of LHC data eclipsing the inverse femtobarn integrated luminosity milestone, we undertake a detailed comparison of the most recent experimental results with Monte Carlo simulation of the full "bare-minimally constrained" parameter space of the class of supersymmetric models which go by the name of No-Scale FSU5. We establish the first sparticle exclusion boundaries on these models, finding that the LSP mass should be at least about 92 GeV, with a corresponding boundary gaugino mass M_1/2 above about 485 GeV. In contrast to the higher mass constraints established for the CMSSM, we find the minimum exclusion boundary on the FSU5 gluino and heavy squark masses resides in the range of 658-674 GeV and 854-1088 GeV, respectively, with a minimum light stop squark mass of about 520 GeV. Moreover, we show that elements of the surviving parameter space not only escape the onslaught of LHC data which is currently decimating the standard mSUGRA/CMSSM benchmarks, but are further able to efficiently explain certain tantalizing production excesses over the SM background which have been reported by the CMS collaboration. We also extend this study comparatively to five distinct collider energies and four specific cut methodologies, including a proposed set of selection cuts designed to reveal the natural ultra-high jet multiplicity signal associated with the stable mass hierarchy m_t < m_g < m_q of the FSU5 models. By so doing, we demonstrate that a rather stable enhancement in model visibility, conservatively of order ten, may be attained by adoption of these cuts, which is sufficient for an immediate and definitive testing of a majority of the model space using only the existing LHC data set. We stress the point that habits established in lower jet multiplicity searches do not necessarily carry over into the ultra-high jet multiplicity search regime.

hep-ph↗
arXiv2011

The No-Scale Multiverse at the LHC

We present a contemporary perspective on the String Landscape and the Multiverse of plausible string, M- and F-theory vacua, seeking to demonstrate a non-zero probability for the existence of a universe matching our own observed physics within the solution ensemble, arguing for the importance of No-Scale Supergravity as an essential common underpinning. Our context is a highly detailed phenomenological probe of No-Scale F-SU(5), a model representing the intersection of the F-lipped SU(5) X U(1)_X Grand Unified Theory (GUT) with extra TeV-Scale vector-like multiplets derived out of F-theory, and the dynamics of No-Scale Supergravity. We present a highly constrained "Golden" region with tan(beta) \sim 15, m_t = 173.0 - 174.4 GeV, M_1/2 = 455 - 481 GeV, and M_V = 691 - 1020 GeV, which simultaneously satisfies all known experimental constraints. We supplement this bottom-up phenomenological perspective with a top-down theoretical analysis of the one-loop effective Higgs potential, achieving a striking consonance via the dynamic determination of tan(beta) and M_1/2 at the local secondary minimization of the spontaneously broken electroweak Higgs vacuum V_min. We present the distinctive signatures of No-Scale F-SU(5) at the LHC, where a light stop and gluino are expected to generate a surplus of ultra-high multiplicity (>= 9) hadronic jet events. We propose modest alterations to the canonical background selection cut strategy which would enhance resolution of these events, while readily suppressing the contribution of all Standard Model processes, and allowing a clear differentiation from competing models of new physics. Detection by the LHC of the ultra-high jet signal would constitute a suggestive evocation of the intimately linked stringy origins of F-SU(5), and could provide a glimpse into the fundamental string moduli, and possibly even the workings of the No-Scale Multiverse.

hep-ph↗
arXiv2011

Elements of F-ast Proton Decay

Gauge coupling unification in the Minimal Supersymmetric Standard Model (MSSM) strongly suggests the existence of a Grand Unified Theory (GUT), which could be probed by the observation of proton decay. Proton lifetime in the p \to (e+|mu+) pi0 dimension six mode is proportional in the fourth power to the GUT mass scale, and inversely proportional in the fourth power to the GUT coupling. We provide an updated dictionary of solutions for the relevant unification parameters with generic beta-function coefficients, significantly upgrading the level of detail with which second order effects are treated, and correcting subtle published errors. F-lipped SU(5) with strict MSSM field content is known to survive existing null detection limits for proton decay approaching 10^34 years, and indeed, the lifetime predicted by prior studies can be so long that successful detection is not currently plausible. Recently studied classes of F-theory derived GUT models postulate additional vector-like multiplets at the TeV scale which modify the renormalization group to yield a substantial increase in the SU(3)_C X SU(2)_L unified coupling. We find the conjunction of these models with the F-resh analysis employed to be comparatively F-ast proton decay, only narrowly evading existing detection limits, and likely falling within the observable range of proposed next generation detectors such as DUSEL and Hyper-Kamiokande. The TeV-scale vector multiplets are themselves suitable for cross correlation by the Large Hadron Collider. Their presence moreover magnifies the gap between the dual mass scales of Flipped SU(5), allowing for an elongated second stage renormalization, pushing grand unification to the doorstep of the reduced Planck mass.

hep-ph↗
arXiv2011

The Golden Strip of Correlated Top Quark, Gaugino, and Vectorlike Mass In No-Scale, No-Parameter F-SU(5)

We systematically establish the hyper-surface within the tan(beta), top quark mass m_t, universal gaugino mass M_1/2, and vectorlike mass M_V parameter volume which is compatible with the application of the No-Scale Supergravity boundary conditions, particularly the vanishing of the Higgs bilinear soft term B_mu, near to the Planck mass at the point M_F of ultimate F-lipped SU(5) unification. M_F is elevated from the penultimate partial unification near the traditional GUT scale at a mass M_32 by the inclusion of extra F-theory derived heavy vectorlike multiplets. We demonstrate that simultaneous adherence to all current experimental constraints, most importantly contributions to the muon anomalous magnetic moment (g-2)_mu, the branching ratio limit on (b \to s gamma), and the 7-year WMAP relic density measurement, dramatically reduces the allowed solutions to a highly non-trivial "golden strip" with tan(beta) \sim 15, m_t = 173.0-174.4 GeV, M_1/2 = 455-481 GeV, and M_V = 691-1020 GeV, effectively eliminating all extraneously tunable model parameters. We emphasize that the consonance of the theoretically viable m_t range with the experimentally established value is an independently correlated "postdiction". The predicted range of M_V is testable at the Large Hadron Collider (LHC). The partial lifetime for proton decay in the leading (e+|mu+) pi0 channels falls around 4.6 X 10^34 Y, testable at the future DUSEL and Hyper-Kamiokande facilities.

hep-ph↗
arXiv2011

The Ultra-High Jet Multiplicity Signal of Stringy No-Scale F-SU(5) at the \sqrt{s} = 7 TeV LHC

We present the distinctive collider signatures of No-Scale F-SU(5), a highly efficient and phenomenologically favored model built on the tripodal foundations of the F-lipped SU(5) X U(1)_X Grand Unified Theory, extra F-theory derived TeV scale vector-like particle multiplets, and the dynamic high scale boundary conditions of No-Scale Supergravity. The identifying features of the supersymmetric spectrum are a light stop and gluino, with both sparticles much lighter than all the additional squarks. This unique mass hierarchy leads to the enhanced production of events with an ultra-high multiplicity of hadronic jets which should be clearly visible to the \sqrt{s} = 7 TeV LHC at only 1 inverse fb of integrated luminosity. We suggest a modest alternative event cutting procedure based around a reduced minimal transverse momentum per jet (p_T > 20 GeV), and an increased minimal multiplicity (>= 9) of distinct jets per subscribed event. These criteria optimize the F-SU(5) signal to background ratio, while readily suppressing the contribution of all Standard Model processes, allowing moreover a clear differentiation from competing models of new physics, most notably minimal supergravity. The characteristic No-Scale signature is quite stable across the viable parameter space, modulo an overall rescaling of the mass spectrum; Detection by the LHC of the ultra-high jet signal would constitute a suggestive evocation of the intimately linked stringy origins of F-SU(5), and could possibly provide a glimpse into the underlying structure of the fundamental string moduli.

hep-ph↗
arXiv2011

Ultra High Jet Signals from Stringy No-Scale Supergravity

We present distinctive signatures of flipped F-Theory models with TeV-scale vector-like particles, a \sqrt{s} = 7 TeV 1 fb^{-1} test at LHC of a class of models well-motivated from string theory. The characteristic feature is a light stop and gluino, both sparticles lighter than all other squarks. This unique aspect of the supersymmetry spectrum generates an ultra-high multiplicity of hadronic jets. We find the optimal signal to background ratio is realized for 9 or more jets. Exclusion of the essential cuts presented here could leave the ultra-high jet signal severely attenuated and concealed.

hep-ph↗
arXiv2011

The Golden Point of No-Scale and No-Parameter ${\cal F}$-SU(5)

The ${\cal F}$-lipped $SU(5)\times U(1)_X$ Grand Unified Theory (GUT) supplemented by TeV-scale vector-like particles from ${\cal F}$-theory, together dubbed ${\cal F}$-SU(5), offers a natural multi-phase unification process which suggests an elegant implementation of the No-Scale Supergravity boundary conditions at the unification scale $M_{\cal F} \simeq 7 \times 10^{17}$ GeV. Enforcing the No-Scale boundary conditions, including $B_μ(M_{\cal F})=0$ on the Higgs bilinear soft term, with the precision 7-year WMAP value on the dark matter relic density isolates a highly constrained "golden point" located near $M_{1/2} = 455$ GeV and $\tan β= 15$ in the $\tanβ-M_{1/2}$ plane, which simultaneously satisfies all known experiments, and moreover corresponds to an imminently observable proton decay rate. Because the universal gaugino mass is actually determined from established low energy data via Renormalization Group Equation (RGE) running, there are no surviving arbitrary scale parameters in the present model.

hep-ph↗
arXiv2011

Dark Matter, Proton Decay and Other Phenomenological Constraints in ${\cal F}$-SU(5)

We study gravity mediated supersymmetry breaking in ${\cal F}$-SU(5) and its low-energy supersymmetric phenomenology. The gaugino masses are not unified at the traditional grand unification scale, but we nonetheless have the same one-loop gaugino mass relation at the electroweak scale as minimal supergravity (mSUGRA). We introduce parameters testable at the colliders to measure the small second loop deviation from the mSUGRA gaugino mass relation at the electroweak scale. In the minimal SU(5) model with gravity mediated supersymmetry breaking, we show that the deviations from the mSUGRA gaugino mass relations are within 5%. However, in ${\cal F}$-SU(5), we predict the deviations from the mSUGRA gaugino mass relations to be larger due to the presence of vector-like particles, which can be tested at the colliders. We determine the viable parameter space that satisfies all the latest experimental constraints and find it is consistent with the CDMS II experiment. Further, we compute the cross-sections of neutralino annihilations into gamma-rays and compare to the first published Fermi-LAT measurement. Finally, the corresponding range of proton lifetime predictions is calculated and found to be within reach of the future Hyper-Kamiokande and DUSEL experiments.

hep-ph↗
arXiv2010

Fast Proton Decay

We consider proton decay in the testable flipped SU(5) X U(1)_X models with TeV-scale vector-like particles which can be realized in free fermionic string constructions and F-theory model building. We significantly improve upon the determination of light threshold effects from prior studies, and perform a fresh calculation of the second loop for the process p \to e^+ π^0 from the heavy gauge boson exchange. The cumulative result is comparatively fast proton decay, with a majority of the most plausible parameter space within reach of the future Hyper-Kamiokande and DUSEL experiments. Because the TeV-scale vector-like particles can be produced at the LHC, we predict a strong correlation between the most exciting particle physics experiments of the coming decade.

hep-ph↗
arXiv2000

Non-Abelian Flat Directions in a Minimal Superstring Standard Model

Recently, by studying exact flat directions of non-Abelian singlet fields, we demonstrated the existence of free fermionic heterotic-string models in which the SU(3)_C x SU(2)_L x U(1)_Y-charged matter spectrum, just below the string scale, consists solely of the MSSM spectrum. In this paper we generalize the analysis to include VEVs of non-Abelian fields. We find several, MSSM-producing, exact non-Abelian flat directions, which are the first such examples in the literature. We examine the possibility that hidden sector condensates lift the flat directions.

hep-ph↗