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

James A. Maxin, Tianjun Li+2 more|arXiv (Cornell University)|Mar 21, 2011

Particle physics theoretical and experimental studies4 citations

TL;DR

This paper proposes a distinctive collider signature for the No-Scale $φ$-SU(5) supersymmetric model, which predicts an ultra-high jet multiplicity signal due to a unique mass hierarchy with a light stop and gluino. At $√s = 7$ TeV LHC, this signal can be detected with only $1~{\rm fb}^{-1}$ luminosity using modified cuts ($p_{\rm T} > 20$ GeV, $\geq 9$ jets), offering a clear distinction from Standard Model backgrounds and competing models like minimal supergravity.

ABSTRACT

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.

Motivation & Objective

• To identify a phenomenologically viable and string-theoretically motivated SUSY model that can be tested at the early LHC.
• To address the challenge of distinguishing highly compressed or exotic SUSY signals from Standard Model backgrounds in early LHC data.
• To propose a modified event selection strategy that enhances signal-to-background ratio for a specific class of SUSY models.
• To demonstrate that the No-Scale $φ$-SU(5) model produces a stable, distinctive ultra-high jet multiplicity signature across its viable parameter space.

Proposed method

• The model is based on F-theory-derived $SU(5)\times U(1)_X$ Grand Unified Theory with vector-like multiplets and No-Scale Supergravity boundary conditions.
• The supersymmetric spectrum features a light stop and gluino, with all other squarks significantly heavier, creating a unique mass hierarchy.
• Theoretical predictions are derived using renormalization group equations (RGEs) and the Super No-Scale mechanism to dynamically determine $M_{1/2}$ and $\tan\beta$.
• A modified event selection criterion is proposed: $p_{\rm T} > 20$ GeV per jet and a minimum of 9 distinct jets per event to suppress SM backgrounds.
• The signal-to-background ratio is optimized by reducing minimal transverse momentum and increasing minimum jet multiplicity.
• The model's stability across parameter space is confirmed via RGE running and vacuum minimization under No-Scale boundary conditions.

Experimental results

Research questions

• RQ1 Can a string-theoretically motivated SUSY model with a unique mass hierarchy produce a detectable ultra-high jet multiplicity signal at the 7 TeV LHC?
• RQ2 How can event selection cuts be modified to enhance the signal-to-background ratio for exotic SUSY signatures like those in No-Scale $\phi$-SU(5)?
• RQ3 Does the No-Scale $\phi$-SU(5) model maintain its distinctive collider signature across its entire viable parameter space?
• RQ4 Can the Super No-Scale mechanism dynamically determine $M_{1/2}$ and $\tan\beta$ in a way consistent with both top-down string theory and bottom-up phenomenology?
• RQ5 How does the No-Scale $\phi$-SU(5) model differ from minimal supergravity in its collider phenomenology, particularly in jet multiplicity?

Key findings

• The No-Scale $\phi$-SU(5) model predicts an ultra-high jet multiplicity signal with $\geq 9$ jets per event, detectable at $\sqrt{s} = 7$ TeV LHC with only $1~{\rm fb}^{-1}$ luminosity.
• The signal arises from a unique mass hierarchy: light stop and gluino, with all other squarks significantly heavier, leading to cascading decays producing many jets.
• The modified event selection cuts ($p_{\rm T} > 20$ GeV, $\geq 9$ jets) significantly suppress Standard Model backgrounds while preserving the signal.
• The characteristic signal remains stable across the viable parameter space, with only an overall rescaling of the mass spectrum.
• The model's signature is clearly distinguishable from minimal supergravity and other competing new physics models due to its high jet multiplicity.
• Detection of such a signal would provide indirect evidence for the stringy origins of the model and insight into the moduli stabilization of fundamental string theory.