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Signatures of Spherical Compactifications at the LHC

Description: TeV-scale extra dimensions may play an important role in electroweak or supersymmetry breaking. We examine the phenomenology of such dimensions, compactified on a sphere S{sup n}, n {ge} 2, and show that they possess distinct features and signatures. For example, unlike flat toroidal manifolds, spheres do not trivially allow fermion massless modes. Acceptable phenomenology then generically leads to ''non-universal'' extra dimensions with ''pole-localized'' 4-d fermions; the bosonic fields can be in the bulk. Due to spherical symmetry, some Kaluza-Klein (KK) modes of bulk gauge fields are either stable or extremely long-lived, depending on the graviton KK spectrum. Using precision electroweak data, we constrain the lightest gauge field KK modes to lie above {approx_equal} 4 TeV. We show that some of these KK resonances are within the reach of the LHC in several different production channels. The models we study can be uniquely identified by their collider signatures.
Date: February 12, 2007
Creator: Davoudiasl, Hooman & Rizzo, Thomas G.
Partner: UNT Libraries Government Documents Department

The New Minimal Standard Model

Description: We construct the New Minimal Standard Model that incorporates the new discoveries of physics beyond the Minimal Standard Model (MSM): Dark Energy, non-baryonic Dark Matter, neutrino masses, as well as baryon asymmetry and cosmic inflation, adopting the principle of minimal particle content and the most general renormalizable Lagrangian. We base the model purely on empirical facts rather than aesthetics. We need only six new degrees of freedom beyond the MSM. It is free from excessive flavor-changing effects, CP violation, too-rapid proton decay, problems with electroweak precision data, and unwanted cosmological relics. Any model of physics beyond the MSM should be measured against the phenomenological success of this model.
Date: January 13, 2005
Creator: Davoudiasl, Hooman; Kitano, Ryuichiro; Li, Tianjun & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

New Dimensions for Randall-Sundrum Phenomenology

Description: We consider a 6D extension of the Randall-Sundrum (RS) model, RS6, where the Standard Model (SM) gauge fields are allowed to propagate in an additional dimension, compactified on S{sup 1} or S{sup 1}/Z{sub 2}. In a minimal scenario, fermions propagate in the 5D RS subspace and their localization provides a model of flavor. New Kaluza-Klein (KK) states, corresponding to excitations of the gauge fields along the 6th dimension, appear near the TeV scale. The new gauge KK modes behave differently from those in the 5D warped models. These RS6 states have couplings with strong dependence on 5D field localization and, within the SM, only interact with heavy fermions and the Higgs sector, to a very good approximation. Thus, the collider phenomenology of the new gauge KK states sensitively depends on the 5D fermion geography. We briefly discuss inclusion of SM fermions in all 6 dimensions, as well as the possibility of going beyond 6D.
Date: September 30, 2008
Creator: Davoudiasl, Hooman & Rizzo, Thomas G.
Partner: UNT Libraries Government Documents Department

{gamma}{gamma} {r_arrow} {gamma}{gamma} as a Test of Weak Scale Quantum Gravity at the NLC

Description: Recently, it has been proposed that the fundamental scale of quantum gravity can be close to the weak scale if there are large extra dimensions . This proposal has important phenomenological implications for processes at the TeV scale. We study the process {gamma}{gamma} {r_arrow} {gamma}{gamma}, assuming an ultraviolet cutoff M{sub S} {approximately} 1 TeV for the effective gravity theory. We find that, at center of mass energies {radical}s {approximately} 1 TeV, the contribution of gravitationally mediated scattering to the cross section is comparable to that coming from the one-loop Feynman diagrams of the Standard Model. We thus conclude that the effects of weak scale quantum gravity can be studied at the Next Linear Collider (NLC), in the photon collider mode. Our results suggest that, for typical proposed NLC energies and luminosities, the range 1 TeV {le} M{sub S} {le} 10 TeV can be probed.
Date: April 23, 1999
Creator: Davoudiasl, Hooman
Partner: UNT Libraries Government Documents Department

Compton Scattering at the NLC and Large Extra Dimensions

Description: We study Compton scattering, {gamma}e {yields} {gamma}e, in the context of the recent proposal for Weak Scale Quantum Gravity (WSQG) with large extra dimensions. It is shown that, with an ultraviolet cutoff M{sub S} {approx} 1 TeV for the effective gravity theory, the cross section for this process at the Next Linear Collider (NLC) deviates from the prediction of the Standard Model significantly. Our results suggest that, for typical proposed NLC energies and luminosities, WSQG can be tested in the range 4 TeV {approx}< M{sub S} {approx}< 16 TeV, making {gamma}e {yields} {gamma}e an important test channel.
Date: July 20, 1999
Creator: Davoudiasl, Hooman
Partner: UNT Libraries Government Documents Department

On Direct Verification of Warped Hierarchy-and-FlavorModels

Description: We consider direct experimental verification of warped models, based on the Randall-Sundrum (RS) scenario, that explain gauge and flavor hierarchies, assuming that the gauge fields and fermions of the Standard Model (SM) propagate in the 5D bulk. Most studies have focused on the bosonic Kaluza Klein (KK) signatures and indicate that discovering gauge KK modes is likely possible, yet challenging, while graviton KK modes are unlikely to be accessible at the LHC, even with a luminosity upgrade. We show that direct evidence for bulk SM fermions, i.e. their KK modes, is likely also beyond the reach of a luminosity-upgraded LHC. Thus, neither the spin-2 KK graviton, the most distinct RS signal, nor the KK SM fermions, direct evidence for bulk flavor, seem to be within the reach of the LHC. We then consider hadron colliders with vs. = 21, 28, and 60 TeV. We find that discovering the first KK modes of SM fermions and the graviton typically requires the Next Hadron Collider (NHC) with {radical}s {approx} 60 TeV and O(1) ab-1 of integrated luminosity. If the LHC yields hints of these warped models, establishing that Nature is described by them, or their 4D CFT duals, requires an NHC-class machine in the post-LHC experimental program.
Date: October 15, 2007
Creator: Davoudiasl, Hooman; /Brookhaven; Rizzo, Thomas G.; /SLAC; Soni, Amarjit & /Brookhaven
Partner: UNT Libraries Government Documents Department

Testing the OPERA Superluminal Neutrino Anomaly at the LHC

Description: The OPERA collaboration has reported the observation of superluminal muon neutrinos, whose speed v{sub {nu}} exceeds that of light c, with (v{sub {nu}}-c)/c {approx_equal} 2.5 x 10{sup -5}. In a recent work, Cohen and Glashow (CG) have refuted this claim by noting that such neutrinos will lose energy, by pair-emission of particles, at unacceptable rates. Following the CG arguments, we point out that pair-emissions consistent with the OPERA anomaly can lead to detectable signals for neutrinos originating from decays of highly boosted top quarks at the LHC, allowing an independent test of the superluminal neutrino hypothesis.
Date: March 15, 2012
Creator: Davoudiasl, Hooman; /Brookhaven; Rizzo, Thomas G. & /SLAC
Partner: UNT Libraries Government Documents Department

Off-the-Wall Higgs in the Universal Randall-Sundrum Model

Description: We outline a consistent Randall-Sundrum (RS) framework in which a fundamental 5-dimensional Higgs doublet induces electroweak symmetry breaking (EWSB). In this framework of a warped Universal Extra Dimension, the lightest Kaluza-Klein (KK) mode of the bulk Higgs is tachyonic leading to a vacuum expectation value (vev) at the TeV scale. The consistency of this picture imposes a set of constraints on the parameters in the Higgs sector. A novel feature of our scenario is the emergence of an adjustable bulk profile for the Higgs vev. We also find a tower of nontachyonic Higgs KK modes at the weak scale. We consider an interesting implementation of this ''Off-the-Wall Higgs'' mechanism where the 5-dimensional curvature-scalar coupling alone generates the tachyonic mode responsible for EWSB. In this case, additional relations among the parameters of the Higgs and gravitational sectors are established. We discuss the experimental signatures of the bulk Higgs in general, and those of the ''Gravity-Induced'' EWSB in particular.
Date: September 9, 2005
Creator: Davoudiasl, Hooman; /Wisconsin U., Madison; Lillie, Ben; Rizzo, Thomas G. & /SLAC
Partner: UNT Libraries Government Documents Department