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Probing the Geometry of Warped String Compactifications at the LHC

Description: Warped string compactifications, characterized by the nonsingular behavior of the metric in the infrared (IR), feature departures from the usual anti?de Sitter warped extra dimensions. We study the implications of the smooth IR cutoff for Randall-Sundrum- (RS-)type models. We find that the phenomenology of the Kaluza-Klein gravitons (including their masses and couplings) depends sensitively on the precise shape of the warp factor in the IR. In particular, we analyze the warped deformed conifold, find that the spectrum differs significantly from that of RS, and present a simple prescription (a mass-gap ansatz) that can be used to study the phenomenology of IR modifications to 5D warped extra dimensions.
Date: May 28, 2007
Creator: Walker, Devin; Shiu, Gary; Underwood, Bret; Zurek, Kathryn M. & Walker, Devin G. E.
Partner: UNT Libraries Government Documents Department

Massive gravity on a brane

Description: At present no theory of a massive graviton is known that is consistent with experiments at both long and short distances. The problem is that consistency with long distance experiments requires the graviton mass to be very small. Such a small graviton mass however implies an ultraviolet cutoff for the theory at length scales far larger than the millimeter scale at which gravity has already been measured. In this paper we attempt to construct a model which avoids this problem. We consider a brane world setup in warped AdS spacetime and we investigate the consequences of writing a mass term for the graviton on a the infrared brane where the local cutoff is of order a large (galactic) distance scale. The advantage of this setup is that the low cutoff for physics on the infrared brane does not significantly affect the predictivity of the theory for observers localized on the ultraviolet brane. For such observers the predictions of this theory agree with general relativity at distances smaller than the infrared scale but go over to those of a theory of massive gravity at longer distances. A careful analysis of the graviton two-point function, however, reveals the presence of a ghost in the low energy spectrum. A mode decomposition of the higher dimensional theory reveals that the ghost corresponds to the radion field. We also investigate the theory with a brane localized mass for the graviton on the ultraviolet brane, and show that the physics of this case is similar to that of a conventional four dimensional theory with a massive graviton, but with one important difference: when the infrared brane decouples and the would-be massive graviton gets heavier than the regular Kaluza-Klein modes, it becomes unstable and it has a finite width to decay off the brane into the continuum ...
Date: December 11, 2003
Creator: Chacko, Z.; Graesser, M.L.; Grojean, C. & Pilo, L.
Partner: UNT Libraries Government Documents Department

Self-accelerating Warped Braneworlds

Description: Braneworld models with induced gravity have the potential to replace dark energy as the explanation for the current accelerating expansion of the Universe. The original model of Dvali, Gabadadze and Porrati (DGP) demonstrated the existence of a ''self-accelerating'' branch of background solutions, but suffered from the presence of ghosts. We present a new large class of braneworld models which generalize the DGP model. Our models have negative curvature in the bulk, allow a second brane, and have general brane tensions and localized curvature terms. We exhibit three different kinds of ghosts, associated to the graviton zero mode, the radion, and the longitudinal components of massive graviton modes. The latter two species occur in the DGP model, for negative and positive brane tension respectively. In our models, we find that the two kinds of DGP ghosts are tightly correlated with each other, but are not always linked to the feature of self-acceleration. Our models are a promising laboratory for understanding the origins and physical meaning of braneworld ghosts, and perhaps for eliminating them altogether.
Date: November 1, 2006
Creator: Carena, Marcela; Lykken, Joseph; /Fermilab; Park, Minjoon; /UC, Davis; Santiago, Jose et al.
Partner: UNT Libraries Government Documents Department

Search for Large Extra Dimensions via Single Photons Plus Missing Energy Final States at s^(1/2) = 1.96 TeV

Description: This dissertation presents a search for large extra dimensions in the single photon plus missing transverse energy final states. We use a data sample of approximately 2.7 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV (recorded with the D{sup -} detector) to investigate direct Kaluza Klein graviton production and set limits, at the 95% C.L., on the fundamental mass scale M{sub D} from 970 GeV to 816 GeV for two to eight extra dimensions.
Date: December 1, 2008
Creator: Carrera, Edgar Fernando & U., /Florida State
Partner: UNT Libraries Government Documents Department

Search for large extra dimensions in the mono-photon final state at s**(1/2) = 1.96-TeV

Description: The authors report on a search for large extra dimensions in a data sample of approximately 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV. They investigate Kaluza-Klein graviton production with a photon and missing transverse energy in the final state. At the 95% C.L. they set limits on the fundamental mass scale M{sub D} from 884 GeV to 778 GeV for 2 to 8 extra dimensions.
Date: March 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for signatures of extra dimensions in the diphoton mass spectrum at the Large Hadron Collider

Description: A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at {radical}s = 7 TeV corresponding to an integrated luminosity of 2.2 fb{sup -1}. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.
Date: December 1, 2011
Creator: Chatrchyan, Serguei; Khachatryan, Vardan; Sirunyan, Albert M.; Tumasyan, Armen; Adam, Wolfgang; Bergauer, Thomas et al.
Partner: UNT Libraries Government Documents Department

Search for Randall-Sundrum gravitons in the dielectron and diphoton final states with 5.4fb$^{-1}$ of data from $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

Description: Using 5.4 fb{sup -1} of integrated luminosity from p{bar p} collisions at {radical}s = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider, we search for decays of the lightest Kaluza-Klein mode of the graviton in the Randall-Sundrum model to ee and {gamma}{gamma}. We set 95% C.L. lower limits on the mass of the lightest graviton between 560 GeV and 1050 GeV for values of the coupling k/{bar M}{sub Pl} between 0.01 and 0.1.
Date: April 1, 2010
Creator: Abazov, Victor Mukhamedovich; /Dubna, JINR; Abbott, Braden Keim; U., /Oklahoma; Abolins, Maris A.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Massless versus Kaluza-Klein gravitons at the LHC

Description: We show that the LHC will be able to differentiate between a four-dimensional model with quantum gravity at {approx} 1 TeV where the (massless) graviton becomes strongly coupled to standard model particles at 1 TeV and brane world type models with a large extra-dimensional volume and massive Kaluza-Klein gravitons. We estimate that the 14 TeV LHC could put a limit of the order of {approx} 5 TeV on the four dimensional Planck mass in a model independent way.
Date: August 26, 2010
Creator: Calmet, Xavier; U., /Sussex; de Aquino, Priscila; /Louvain U., CP3 /Leuven U.; Rizzo, Thomas G. & /SLAC
Partner: UNT Libraries Government Documents Department

SN1987A Constraints on Large Compact Dimensions

Description: Recently there has been a lot of interest in models in which gravity becomes strong at the TeV scale. The observed weakness of gravitational interactions is then explained by the existence of extra compact dimensions of space, which are accessible to gravity but not to Standard Model particles. In this letter we consider graviton emission into these extra dimensions from a hot supernova core. The phenomenology of SN1987A places strong constraints on this energy loss mechanism, allowing us to derive a bound on the fundamental Planck scale. For the case of two extra dimensions we obtain a very strong bound of M {ge} 50 TeV, which corresponds to a radius R {le} 0.3 {micro}m. While there are a lot of sources of uncertainty associated with this bound, we find that pushing it down to the few-TeV range, which could in principle be probed by ground-based experiments, is disfavored. For three or more extra dimensions the SN1987A constraints do not exclude a TeV gravitational scale.
Date: March 23, 1999
Creator: Perelstein, Maxim
Partner: UNT Libraries Government Documents Department

One loop graviton self-energy in a locally de Sitter background

Description: The graviton tadpole has recently been computed at two loops in a locally de Sitter background. We apply intermediate results of this work to exhibit the graviton self-energy at one loop. This quantity is interesting both to check the accuracy of the first calculation and to understand the relaxation effect it reveals. In the former context we show that the self-energy obeys the appropriate Ward identity. We also show that its flat space limit agrees with the flat space result obtained by Capper in what should be the same gauge. 15 refs., 4 figs., 10 tabs.
Date: February 1996
Creator: Tsamis, N. C. & Woodard, R.P.
Partner: UNT Libraries Government Documents Department

Early Inflation and Cosmology in Theories with Sub-Millimeter Dimensions

Description: We discuss early cosmology in theories where the fundamental Planck mass is close to the TeV scale. In such theories the standard model fields are localized to a (3 + 1)-dimensional wall with n new transverse sub-millimeter sized spatial dimensions. The topics touched upon include: early inflation that occurs while the size of the new dimensions are still small, the spectrum and magnitude of density perturbations, the post-inflation era of contraction of our world while the internal dimensions evolve to their final ''large'' radius, and the production of gravitons in the bulk during these two eras. The radion moduli problem is also discussed.
Date: March 15, 1999
Creator: Arkani-Hamed, Nima
Partner: UNT Libraries Government Documents Department

Rapid asymmetric inflation and early cosmology in theories with sub-millimeter dimensions

Description: It was recently pointed out that the fundamental Planck mass could be close to the TeV scale with the observed weakness of gravity at long distances being due the existence of new sub-millimeter spatial dimensions. In this picture the standard model fields are localized to a (3+1)-dimensional wall or ''3-brane''. We show that in such theories there exist attractive models of inflation that occur while the size of the new dimensions are still small. We show that it is easy to produce the required number of efoldings, and further that the density perturbations {delta}{rho}/{rho} as measured by COBE can be easily reproduced, both in overall magnitude and in their approximately scale-invariant spectrum. In the minimal approach, the inflaton field is just the moduli describing the size of the internal dimensions, the role of the inflationary potential being played by the stabilizing potential of the internal space. We show that under quite general conditions, the inflationary era is followed by an epoch of contraction of our world on the brane, while the internal dimensions slowly expand to their stabilization radius. We find a set of exact solutions which describe this behavior, generalizing the well-known Kasner solutions. During this phase, the production of bulk gravitons remains suppressed. The period of contraction is terminated by the blue-shifting of Hawking radiation left on our wall at the end of the inflationary de Sitter phase. The temperature to which this is reheated is consistent with the normalcy bounds. We give a precise definition of the radion moduli problem.
Date: March 15, 1999
Creator: Arkani-Hamed, Nima
Partner: UNT Libraries Government Documents Department

Search for New Dielectron Resonances and Randall-Sundrum Gravitons at the Collider Detector at Fermilab

Description: A search for the new dielectron mass resonances using data recorded by the CDF II detector and corresponding to an integrated luminosity of 5.7 fb{sup -1} is presented. No significant excess over the expected standard model prediction is observed. In this dataset, an event with the highest dielectron mass ever observed (960 GeV/c{sup 2}) was recorded. The results are interpreted in the Randall-Sundrum (RS) model. Combined with the 5.4 fb{sup -1} diphoton analysis, the RS-graviton mass limit for the coupling k/{bar M}{sub Pl} = 0.1 is 1058 GeV/c{sup 2}, making it the strongest limit to date.
Date: March 1, 2011
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S.; /INFN, Padua et al.
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

Minimal Direct Gauge Mediation

Description: We propose a simple model of gauge mediation with a small gravitino mass, m{sub 3/2} < O(10) eV, where supersymmetry is broken by a strong dynamics at O(10) TeV.
Date: November 7, 2007
Creator: Ibe, Masahiro & Kitano, Ryuichiro
Partner: UNT Libraries Government Documents Department

Search for New Heavy Particles Decaying to Z0 Z0 ---> eeee in p - anti-p Collisions at s**(1/2) = 1.96-TeV

Description: We report the results of a search for the anomalous production of a massive particle decaying to four electrons via two Z{sup 0} bosons in 1.1 fb{sup -1} of p{bar p} collisions at {radical}s =1.96 TeV collected by the CDF II detector at Fermilab. We employ optimized electron identification criteria to maximize acceptance and efficiency. We estimate the backgrounds in the invariant mass range 500-1000 GeV/c{sup 2} to be 0.028 {+-} 0.009 (stat) {+-} 0.011 (syst) events. We observe zero events in this search region. Assuming a Randall-Sundrum graviton production model, we set 95% CL limits on {sigma} x BF(G {yields} Z{sup 0}Z{sup 0}) < 4-6 pb, depending on the graviton mass.
Date: January 1, 2008
Creator: Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M.G.; Alvarez Gonzalez, B.; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

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

Higher Curvature Gravity in TeV-Scale Extra Dimensions

Description: We begin a general exploration of the phenomenology of TeV-scale extra-dimensional models with gravitational actions that contain higher curvature terms. In particular, we examine how the classic collider signatures of the models of Arkani-Hamed, Dimopoulos and Dvali (missing energy and new dimension-8 contact interactions) and of Randall and Sundrum (TeV-scale graviton Kaluza-Klein resonances) are altered by these modifications to the usual Einstein-Hilbert action. We find that not only are the detailed signatures for these gravitationally induced processes altered but new contributions are found to arise due to the existence of additional scalar Kaluza-Klein states in the spectrum.
Date: March 31, 2006
Creator: Rizzo, Thomas G.
Partner: UNT Libraries Government Documents Department

Search for new physics in high mass electron-positron events in p anti-p collisions at s**(1/2) = 1.96-TeV

Description: We report the results of a search for a narrow resonance in electron-positron events in the invariant mass range of 150-950 GeV/c{sup 2} using 1.3 fb{sup -1} of p{bar p} collision data at {radical}s=1.96 TeV collected by the CDF II detector at Fermilab. No significant evidence of such a resonance is observed and we interpret the results to exclude the standard model-like Z{prime} with a mass below 923 GeV/c{sup 2} and the Randall-Sundrum graviton with a mass below 807 GeV/c{sup 2} for k/{bar M}{sub pl} = 0.1, both at the 95% confidence level. Combining with di-photon data excludes the Randall-Sundrum graviton for masses below 889 GeV/c{sup 2} for k/{bar M}{sub pl} = 0.1
Date: July 1, 2007
Creator: Aaltonen, T.; Abulencia, A.; Adelman, J.; Affolder, Anthony Allen; Akimoto, T.; Albrow, Michael G. et al.
Partner: UNT Libraries Government Documents Department

Revamped braneworld gravity

Description: Gravity in five-dimensional braneworld backgrounds often exhibits problematic features, including kinetic ghosts, strong coupling, and the vDVZ discontinuity. These problems are an obstacle to producing and analyzing braneworld models with interesting and potentially observable modifications of 4d gravity. We examine these problems in a general AdS{sub 5}/AdS{sub 4} setup with two branes and localized curvature from arbitrary brane kinetic terms. We use the interval approach and an explicit ''straight'' gauge-fixing. We compute the complete quadratic gauge-fixed effective 4d action, as well as the leading cubic order corrections. We compute the exact Green's function for gravity as seen on the brane. In the full parameter space, we exhibit the regions which avoid kinetic ghosts and tachyons. We give a general formula for the strong coupling scale, i.e. the energy scale at which the linearized treatment of gravity breaks down, for relevant regions of the parameter space. We show how the vDVZ discontinuity can be naturally but nontrivially avoided by ultralight graviton modes. We present a direct comparison of warping versus localized curvature in terms of their effects on graviton mode couplings. We exhibit the first example of DGP-like crossover behavior in a general warped setup.
Date: November 1, 2005
Creator: Bao, Ruoyu; /Chicago U., EFI /Chicago U.; Carena, Marcela; /Fermilab; Lykken, Joseph; /Chicago U., EFI /Chicago U. /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Searching for new physics at CDF

Description: We present recent results on searches for physics beyond the Standard Model obtained from the analysis of 1 fb{sup -1} of data collected at the Tevatron Collider by the CDF Collaboration. We report on model-independent studies for anomalous production of {ell}{gamma} + X, {ell}{gamma}bE{sub T} and {gamma}{gamma} + E{sub T}, Standard Model t{bar t}{gamma} production. We also present results for the Randall-Sundrum Gravitons, the same-sign dileptons and the trileptons searches. No significant excess of data over the predicted background is observed.
Date: November 1, 2006
Creator: Shreyber, Irina & /Moscow, ITEP
Partner: UNT Libraries Government Documents Department

Search for high mass resonances in dilepton, dijet and diboson final states at the Tevatron

Description: At hadron colliders, new massive particles can be searched for by the observation of high transverse momentum objects forming high-mass resonances. Searches for additional massive vector bosons (W{prime},Z{prime}), Randall-Sundrum gravitons and sneutrinos in R-parity violating scenarios are performed in dilepton, dijets and diboson final states. The most recent results from the CDF and D0 experiments at the Tevatron are presented corresponding to integrated luminosities between 1 and 4 fb{sup -1}.
Date: September 1, 2009
Creator: Jaffre, Michel & /Orsay, LAL
Partner: UNT Libraries Government Documents Department

N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops

Description: We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.
Date: February 15, 2012
Creator: Boucher-Veronneau, C. & Dixon, L. J.
Partner: UNT Libraries Government Documents Department