Searches for hyperbolic extra dimensions at the LHC
Tommy Ohlsson
备注：
3 pages, 4 figures, poster presented at the XXXIVth International Conference on High Energy Physics (ICHEP08), Philadelphia, Pennsylvania, USA, July 30-August 5, 2008
In this poster, we present a model of large extra dimensions where the internal space has the geometry of a hyperbolic disc. Compared with the ADD model, this model provides a more satisfactory solution to the hierarchy problem between the electroweak scale and the Planck scale, and it also avoids constraints from astrophysics. Since there is no known analytic form of the Kaluza-Klein spectrum for our choice of geometry, we obtain a spectrum based on a combination of approximations and numerical computations. We study the possible signatures of our model for hadron colliders, especially the LHC, where the most important processes are the production of a graviton together with a hadronic jet or a photon. We find that for the case of hadronic jet production, it is possible to obtain relatively strong signals, while for the case of photon production, this is much more difficult.
We investigate a model of large extra dimensions where the internal space has the geometry of a hyperbolic disc. Compared with the ADD model, this model provides a more satisfactory solution to the hierarchy problem between the electroweak scale and the Planck scale, and it also avoids constraints from astrophysics. In general, a novel feature of this model is that the physical results depend on the position of the brane in the internal space, and in particular, the signal almost disappears completely if the brane is positioned at the center of the disc. Since there is no known analytic form o…
For the dilepton production at hadron collider in TeV scale gravity models, inclusion of QCD corrections to NLO stabilises the cross section with respect to scale variations. The K-factors for the various distributions for the ADD and RS model at both LHC and Tevatron are presented.
The nature of space-time at high energy is an open question and the link between extra-dimensional theories with the physics of the Standard Model can not be established in a unique way. The compactification path is not unique and supersymmetry breaking can be done in different ways. Compactifications based on hyperbolic orbifolds gather a large number of properties that are useful for this problem, like a Dirac spectrum chiral zero modes, a mass gap with the Kaluza-Klein modes, discrete residual symmetries for the stability of dark matter, and interesting cosmological constructions. This shal…
If the new boson is lying in the narrow mass range between 122 - 127 GeV is confirmed to be a Higgs boson, then stability of the electroweak vacuum in a minimal model with a universal extra dimension (mUED) will require a much lower cutoff for the theory than has been envisaged earlier. We show that this low cutoff would lead to important changes in much of the mUED phenomenology studied till now. In particular, prospects for LHC searches for n = 1 states are rather limited, while resonant n = 2 states may go completely undetected. Prospects for detection at the ILC and CLIC are less affected.
We show the bounds on five- and six-dimensional Universal Extra Dimension models from the result of the Higgs boson searches at the Large Hadron Collider and electroweak precision measurement. The latest data released by the ATLAS and the CMS gives the lower bounds on Kaluza-Klein scale which are from 650 GeV to 1350 GeV depending on models from Higgs to diboson/diphoton decay signal. The Higgs production cross section can be enhanced by factor 1.5 in crude estimation, diphoton decay signal is suppressed about 10%. Electroweak precision measurement also gives the lower bounds as from 700 GeV t…
We present a short review of theories based on warped extra dimensions (motivated by the hierarchy problem of the Standard Model) which can accomodate a Higgs boson in the range suggested by the recent LHC results at 7 TeV. Using the AdS/CFT correspondence the Higgs is composite and can be described in the dual theory by a bound state of the 4D CFT. We have classified the theories in those with a scalar Higgs (5D SM) and those where the Higgs is the fifth component (gauge-Higgs unification) of a bulk gauge field.
Models with universal extra dimensions predict that each Standard Model particle is accompanied by a tower of Kaluza-Klein resonances. Canonical searches for the production and cascade decays of first Kaluza-Klein modes through missing transverse momentum signatures suffer in general from low detection efficiencies because of the rather compressed Kaluza-Klein particle mass spectrum. Here, instead we analyze signatures from the production of second Kaluza-Klein states which can decay into Standard Model particles and thus do not result in any missing transverse momentum. Such signatures provid…
We study constraints on the radion mass and couplings in the Randall-Sundrum model from the recent LHC data on the Standard Model (SM) Higgs boson searches. When the radion is heavy enough so that it can decay into a pair of on-shell Z-bosons, we find that the ZZ channel gives a stringent constraint. For example, if the radion mass m_ϕis 200 GeV, the scale Λ_ϕwhich characterizes the interactions of the radion with the SM fields must be larger than 5 TeV. Even for m_ϕ=1 TeV, we find that the lower bound on Λ_ϕis 2 TeV.
Characteristic features of processes mediated by gauge bosons are discussed in the framework of theories with large extra dimensions. It is shown that if gauge bosons propagate in the bulk, then there arises a destructive interference not only between W and W' (or Z and Z'), but also between W' and Z' and the Kaluza-Klein towers of higher excitations of W and Z bosons respectively. Specific calculations are made and plotted for the LHC with the center of mass energy 14 TeV.
We study direct searches of additional Higgs bosons in multi-top-quarks events at the LHC with the collision energy of 14 TeV as well as the International Linear Collider (ILC) with the collision energy of 1 TeV. As a benchmark model, we consider two Higgs doublet models with a softly-broken discrete $Z_2$ symmetry, where the $t\bar t$ decay mode of additional neutral Higgs bosons can be dominant if their masses are heavy enough. Thus, the multi-top-quarks events become an important probe of the extended Higgs sector at future colliders. We estimate the discovery reach at the LHC and the ILC, …
I give a summary of BSM searches performed by the ATLAS and CMS experiments with an focus on heavy gauge bosons, extra dimensions and quantum black holes. The presented results use data collected during 2012 when the LHC operated at an center of mass energy of $\sqrt{s}$ = 8 TeV.
A leading order (LO) analysis is presented that demonstrates that key top backgrounds to H -> W^+W^- -> l^\pm l^\mp \sla{p}_T decays in weak boson fusion (WBF) and gluon fusion (GF) at the CERN Large Hadron Collider can be extrapolated from experimental data with an accuracy of order 5% to 10%. If LO scale variation is accepted as proxy for the theoretical error, parton level results indicate that the tt~j background to the H -> WW search in WBF can be determined with a theoretical error of about 5%, while the tt~ background to the H -> WW search in GF can be determined with a theoretical erro…
For the purpose of cross-fertilising currently separate experimental approaches, we connect results of LHC analyses attempting to access the properties of additional $W^\prime$ and $Z^\prime$ bosons from Drell-Yan processes. Under theoretical assumptions linking the two new gauge bosons, we take into account that such possible states of nature are wide enough (in relation to the leptonic mass resolution) for the corresponding signals be significantly affected by interference effects with the background from the Standard Model. The shape of the differential cross section may then no longer be a…
In this letter, we present LHC limits on the minimal universal extra dimension (MUED) model from LHC Run 1 data and current limits from searches of the ongoing Run 2. Typical collider signals of the Kaluza-Klein (KK) states mimic generic degenerate supersymmetry (SUSY) missing transverse momentum signatures since the excited KK particles cascade decay to jets, leptons and the lightest KK particle which is stable due to KK parity and thus evades detection. We test the parameter space against a large number of supersymmetry based missing energy searches implemented in the public code CheckMATE. …
We study M-theory solutions involving compact hyperbolic spaces. The combination of a gap `a la Randall-Sundrum and the topology of an internal Riemann surface allows a geometrical solution to the hierarchy problem that does not require light Kaluza--Klein modes. We comment on the consequences of such a compactification for LHC physics.
The success of the first three years of operations of the LHC at center-of-mass energies of 7 and 8 TeV radically changed the landscape of searches for new physics beyond the standard model and our very way of thinking about its possible origin and its hiding place. Among the paradigms of new physics that have been probed quite extensively at the LHC, are various models that predict the existence of extra spatial dimensions. In this review, the current status of searches for extra dimensions with the CMS detector is presented, along with prospects for future searches at the full energy of the …
We present results from several searches for various exotic physics phenomena like large extra dimensions, leptoquarks, and dark matter, in proton-proton collisions at $\sqrt{s}$ = 7 and 8 TeV delivered by the LHC and collected with the CMS detector. Many different final states are analyzed using data collected in 2011 and 2012 corresponding to an integrated luminosity up to 5.0 fb$^{-1}$ and 19.7 fb$^{-1}$. No sign of physics beyond the standard model has been observed so far and the results are used to set new limits on various new physics model parameters.
Searches for extra spatial dimensions remain among the most popular new directions in our quest for physics beyond the Standard Model. High-energy collider experiments of the current decade should be able to find an ultimate answer to the question of their existence in a variety of models. Until the start of the LHC in a few years, the Tevatron will remain the key player in this quest. In this paper, we review the most recent results from the Tevatron on searches for large, 1/TeV-size, and Randall-Sundrum extra spatial dimensions, which have reached a new level of sensitivity and currently pro…
In this paper we present an analysis strategy and a dedicated tool to determine the exclusion confidence level for any scenario involving multiple heavy extra quarks with generic decay channels, as predicted in several extensions of the Standard Model. We have created, validated and used a software package, called XQCAT (eXtra Quark Combined Analysis Tool), which is based on publicly available experimental data from direct searches for top partners and from Supersymmetry inspired searches. By means of this code, we recast the limits from CMS on new heavy extra quarks considering a complete set…
We investigate the impact of recent limits from LHC searches for supersymmetry and from direct and indirect searches for dark matter on global Bayesian inferences of the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM). In particular we apply recent exclusion limits from the CMS α_T analysis of 1.1/fb of integrated luminosity, the current direct detection dark matter limit from XENON100, as well as recent experimental constraints on γ-ray fluxes from dwarf spheroidal satellite galaxies of the Milky Way from the FermiLAT telescope, in addition to updating values …
In scenarios with extra dimensions the gravitational interaction may become strong at TeV energies. This could modify the $ν$$N$ cross section and imply distinct signals at neutrino telescopes. In particular, cosmogenic neutrinos of $E\approx 10^9$ GeV could experience frequent interactions with matter where they lose a very small fraction of their energy. We define a consistent model of strong gravity at the TeV scale with just one extra dimension and a first Kaluza-Klein excitation of the graviton of mass around 1 GeV. We describe the collisions at transplanckian energies (multigraviton exch…
Warped Extra Dimension scenarios are a rich playground for phenomenology of heavy resonances at LHC. The Radion and the KK-graviton are inevitable signatures of this class of models. On face of the latest LHC experimental results on the direct searches for Beyond Standard Model physics we update the phenomenological predictions for production and decay of such resonances in its main production modes. We also highlight the phenomenology results relevant to collider searches in individual channels, and provide tools for interpretation of current and future experimental analyses using two specifi…
We discuss the specificity of searches for hypothetical $W^{\prime}$, $Z^{\prime}$ and $γ^{\prime}$ bosons at hadron colliders in single top quark and $μ^{+}ν_μ$ production and Drell-Yan processes assuming these particles to be the Kaluza-Klein excitations of the gauge bosons of the Standard Model. In this case any process mediated by $W$ is also mediated by the whole KK tower of its excitations, whereas to the processes mediated by $Z$ and $γ$ there is not only a contribution from their KK towers, but also from that of the graviton. The contributions of the towers above $W^{\prime}$, $Z^{\pri…
We consider the performance of the ATLAS and CMS searches for events with missing transverse energy, which were originally motivated by supersymmetry, in constraining extensions of the Standard Model based on extra dimensions, in which the mass differences between recurrences at the same level are generically smaller than the mass hierarchies in typical supersymmetric models. We consider first a toy model with pair-production of a single vector-like quark U1 decaying into a spin-zero stable particle A1 and jet, exploring the sensitivity of the CMS alphaT and ATLAS meff analysis to U1 mass and …
We discuss a possibility that the parameter space of the two Higgs doublet model is significantly narrowed down by considering the synergy between direct searches for additional Higgs bosons at the LHC and its luminosity upgraded operation and precision measurements of the Higgs boson properties at future electron-positron colliders such as the International Linear Collider. We show that, in the case where the coupling constants of the discovered Higgs boson are slightly different from the predicted values in the standard model, most of the parameter space is explored by the direct searches of…
The available data on neutron scattering were analyzed to constrain a hypothetical new short-range interaction. We show that these constraints are several orders of magnitude better than those usually cited in the range between 1 pm and 5 nm. This distance range occupies an intermediate space between collider searches for strongly coupled heavy bosons and searches for new weak macroscopic forces. We emphasise the reliability of the neutron constraints in so far as they provide several independent strategies. We have identified the most promising way to improve them.
We consider radion stabilization in hyperbolic brane-world scenarios. We demonstrate that in the context of Einstein gravity, matter fields which stabilize the extra dimensions must violate the null energy condition. This result is shown to hold even allowing for FRW-like expansion on the brane. In particular, we explicitly demonstrate how one putative source of stabilizing matter fails to work, and how others violate the above condition. We speculate on a number of ways in which we may bypass this result, including the effect of Casimir energy in these spaces. A brief discussion of supersymme…
We present calculations of the magnetic moment contribution to neutrino electron scattering in large extra dimension brane-bulk models (LED) with three bulk neutrinos. We discuss the cases with two and three large extra dimensions of sizes $R$. The calculations are done using reactor flux from Uranium, $^{235}U$ as the neutrino source. We find that if the electron neutrino mass is chosen to be in the range of one eV, the differential cross section for $\barν-e$ scattering for low electron recoil energy can be of the same order as the presently explored values in reactor experiments. Furthermor…
The comparison of the results of direct detection of Dark Matter, obtained with various target nuclei, requires model-dependent, or even arbitrary, assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the spin-independent (SI) interaction has to be neglected. In the light of the null results from supersymmetry searches at the LHC, the squark sector is pushed to high masses. We show that for a squark sector at the TeV scale, the framework used to extract contraints from direct detection searches can be redefined as the number of free parameters is reduced. Moreover, the co…
We outline a toy model in which a unique mechanism may trigger a dynamical chain resulting in key low-energy regularities. The starting points are a negative cosmological term in the bulk and conformally invariant nongravity sector. These elements ensure compactification of the extra dimensional space on a compact hyperbolic manifold (with the negative and constant scalar curvature). The overall geometry is then M_4 x B_n. The negative curvature on B_n triggers the formation of the four-dimensional defect which provides in turn a dynamical localization of ordinary particles. It also leads, sim…
We reconsider theories with low gravitational (or string) scale M_* where Newton's constant is generated via new large-volume spatial dimensions, while Standard Model states are localized to a 3-brane. Utilizing compact hyperbolic manifolds (CHM's) we show that the spectrum of Kaluza-Klein (KK) modes is radically altered. This allows an early universe cosmology with normal evolution up to substantial temperatures, and completely negates the constraints on M_* arising from astrophysics. Furthermore, an exponential hierarchy between the usual Planck scale and the true fundamental scale of physic…
The $τ$ polarization can be easily measured at LHC in the 1-prong hadronic $τ$ decay channel by measuring what fraction of the $τ$-jet momentum is carried by the charged track. A simple cut requiring this fraction to be >0.8 retains most of the polarization of $τ=$+1 $τ$-jet signal while suppressing the polarization of $τ=$-1 $τ$-jet background and practically eliminating the fake $τ$ background. This can be utilized to extract the charged Higgs signal. It can be also utilized to extract the SUSY signal in the stau NLSP region, and in particular the stau co-annihilaton region.
We propose a natural scenario for the cosmological inflation with the non-minimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily accompany with the low Kaluza-Klein scale so that the model allows a single field inflation with a scale around $10^{13}$ GeV. The model fulfills all the observed data and predicts a sizable gravitational perturbation, r~0.003.
Using a Markov chain Monte Carlo approach, we find the allowed parameter space of a MSSM model with seven free parameters. In this model universality conditions at the GUT scale are imposed on the gaugino sector. We require in particular that the relic density of dark matter saturates the value extracted from cosmological measurements assuming a standard cosmological scenario. We characterize the parameter space of the model that satisfies experimental constraints and illustrate the complementarity of the LHC searches, B-physics observables and direct dark matter searches for further probing t…
We obtain contraints on three Universal Extra Dimensional models utilizing limits from the CMS Collaboration on W' production and decay into a single-top-quark final state. We find a weak constraint on the Minimal Universal Extra Dimensions model due to small Kaluza-Klein number violating terms. In contrast, the W' search puts a strong limit on the size of the Dirac mass term of the quarks in Split Universal Extra Dimension models. In Non-minimal Universal Extra Dimension models the W' search constrains the splitting between the boundary localized kinetic terms of the gauge bosons and the quar…
In a truly model-independent approach, we reexamine a minimal extension of the Standard Model (SM) through the introduction of an additional $U(1)$ symmetry leading to a new neutral gauge boson ($Z'$), allowing its kinetic mixing with the hypercharge gauge boson. An SM neutral scalar is used to spontaneously break this extra symmetry leading to the mass of the $Z'$. Except for three right-handed neutrinos no other fermions are added. We use the current LHC Drell-Yan data to put model-independent constraints in the parameter space of three quantities, namely, $M_{Z'}$, the $Z$-$Z'$ mixing angle…
This paper intends to collect available data on searches for scalar resonances at LHC. It is suggested that, in the absence of SUSY, the most compelling picture is the composite framework, with the idea that the lightest particles are composite scalars of the pseudo-Nambu-Goldstone type, emerging from a broken symmetry at a higher scale, the h(125) boson being one of them. Searches in two-photons, Z-photon, ZZ into 4 leptons, top, h and W pairs are reviewed. A recent search based on lepton tagging from a spectator W/Z is also discussed. Aside from the already well-known scalar observed by CMS …
We analyze the data from two recent experiments designed to search for solar axions within the context of multidimensional theories of the Kaluza-Klein type. In these experiments, axions were supposed to be emitted from the solar core, in M1 transitions between the first excited state and the ground state of 57Fe and 7Li. Because of the high multiplicity of axionic Kaluza-Klein states which couple with the strength of ordinary QCD axions, we obtain much more stringent experimental limits on the four-dimensional Peccei-Quinn breaking scale f_{PQ}, compared with the solar QCD axion limit. Specif…
We explore the phenomenology of an extra U(1) gauge boson which primarily couples to standard model gauge bosons. We classify all possible parity-odd couplings up to dimension 6 operators. We then study the prospects for the detection of such a boson at the LHC and show that the electroweak decay channels lead to very clean signals, allowing us to probe couplings well into the TeV scale.
Several constructions, of stringy origins or not, generate abelian gauge extensions of the Standard Model (SM). Even if the particles of the SM are not charged under this extra $U'(1)$, one cannot avoid the presence of a kinetic mixing between $U'(1)$ and the hypercharge $U_Y(1)$. In this work, we constraint drastically this kinetic mixing, taking into account the recent experimental data from accelerator physics, direct detection and indirect detection of dark matter. We show that the region respecting WMAP and experimental constraints is now very narrowed along the pole line where $M_{Z_D}\s…
In the 'fat-brane' realization of Universal Extra Dimension (UED) models, the gravity mediated decays of Kaluza-Klein (KK) excitations of the Standard Model (SM) particles offer interesting collider signals. Colored level-1 KK-particles (quarks $q^1$ and/or gluons $g^{1}$) are pair-produced at the colliders due to conserved KK-parity. These particles, then, cascade decay into lighter level-1 KK-particle in association with one or more SM particles until producing lightest KK particle (LKP). The gravity mediation allows LKP to decay into photon or $Z$-boson plus gravity excitation, hence result…
Large Hadron Collider (LHC) searches for the SM Higgs boson provide a powerful limit on models involving Universal Extra Dimensions (UED) where the Higgs production is enhanced. We have evaluated all one-loop diagrams for Higgs production from gluon fusion and decay to two photons within "minimal" UED (mUED), independently confirming previous results, and we have evaluated enhancement factors for Higgs boson production and decay over the mUED parameter space. Using these we have derived limits on the parameter space, combining data from both ATLAS and CMS collaborations for the most recent 7 T…
