Effects Of Large Extra Dimensions Research Articles

Higgs vacuum decay in a braneworld

We examine the effect of large extra dimensions on vacuum decay in the Randall–Sundrum (RS) braneworld paradigm. We assume the scalar field is confined to the brane, and compute the probability for forming an “anti-de Sitter” (AdS) bubble inside a critical flat RS brane. We present the first full numerical solutions for the brane instanton considering two test potentials for the scalar field. We explore the geometrical impact of thin and thick bubble walls, and compute the instanton action in a range of cases. We conclude by commenting on a more physically realistic potential relevant for the Standard Model Higgs. For bubbles with large backreaction, the extra dimension has a dramatic effect on the tunnelling rate, however, for the weakly backreacting bubbles more relevant for realistic Standard Model potentials, the extra dimension has little impact.

Higgs vacuum decay from particle collisions?

We examine the effect of large extra dimensions on black hole seeded vacuum decay using the Randall-Sundrum model as a prototype for warped extra dimensions. We model the braneworld black hole by a tidal solution, and solve the Higgs equations of motion for the instanton on the brane. Remarkably, the action of the static instanton can be shown to be the difference in the bulk areas of the seed and remnant black holes, and we estimate these areas assuming the black holes are small compared to the bulk AdS radius. Comparing to the Hawking evaporation rate shows that small black hole seeds preferentially catalyse vacuum decay, thus extending our previous results to higher dimensional braneworld scenarios. The parameter ranges do not allow for Standard Model Higgs decay from collider black holes, but they can be relevant for cosmic ray collisions.

Double Higgs boson production with a jet substructure analysis to probe extra dimensions

In this paper, we perform a comprehensive study to probe the effects of large extra dimensions through double Higgs production in proton-proton collisions at the center-of-mass energies of 14, 33, 100 TeV. We concentrate on the channel in which both Higgs bosons decay into $b\bar{b}$ pair and take into account the main background contributions through realistic Monte-Carlo simulations. In order to achieve an efficient event reconstruction and a good background rejection, jet substructure techniques are used to efficiently capture the boosted Higgs bosons in the final state. The expected limits on the model parameters are obtained based on the invariant mass and the angular properties of the final state objects. Depending on the number of extra dimensions, bounds up to 6.1, 12.5, 28.1 TeV are set on the model parameter at proton-proton collisions with the center-of-mass energies of 14, 33, and 100 TeV, respectively.

Large extra dimension effects through light-by-light scattering at the CERN LHC

Observing light-by-light scattering at the large hadron collider (LHC) has received quite some attention and it is believed to be a clean and sensitive channel to possible new physics. In this paper, we study the diphoton production at the LHC via the process \({{pp}}\rightarrow {{p}}\gamma \gamma {{p}}\rightarrow {{p}}\gamma \gamma {{p}}\) through graviton exchange in the large extra dimension (LED) model. Typically, when we do the background analysis, we also study the double Pomeron exchange of \(\gamma \gamma \) production. We compare its production in the quark–quark collision mode to the gluon–gluon collision mode and find that contributions from the gluon–gluon collision mode are comparable to the quark–quark one. Our result shows, for extra dimension \(\delta =4\), with an integrated luminosity \(\mathcal{L} = 200\,\mathrm{fb}^{-1}\) at the 14 TeV LHC, that diphoton production through graviton exchange can probe the LED effects up to the scale \({M}_{S}=5.06 (4.51, 5.11)\,\mathrm{TeV}\) for the forward detector acceptance \(\xi _1 (\xi _2, \xi _3)\), respectively, where \(0.0015<\xi _1<0.5\), \(0.1<\xi _2<0.5\), and \(0.0015<\xi _3<0.15\).

Effects of large extra dimensions on cosmogenic neutrino fluxes

We study the consequences of theories with extra dimensions and a gravity scale of a few TeVs on the cosmogenic flux of neutrinos. Taking into account the most recent upper limits for the onset of the gravity effects given by the LHC, and the updated predictions for the cosmogenic neutrino flux consistent with Fermi-LAT data, we compute the expected number of shower events to be detected with new generation acoustic detectors such as ARA.

Revisiting the large extra dimension effects onW-pair production at the LHC in next-to-leading order QCD

In the framework of the large extra dimensions (LED) model, we investigate the effects induced by the Kaluza-Klein (KK) gravitons up to the QCD next-to-leading order (NLO) on the $W$-pair production followed by a subsequential $W$-decay at the CERN LHC. We depict the regions in the $\mathcal{L}-M_{S}$ parameter space where the LED effect can and cannot be observed from the analyses of the $pp \to W^+W^- + X$ and $pp \to W^+W^- \to W^{\pm}l^{\mp}\stackrel{(-)}{\nu} + X$ processes. We find that the ability of probing the LED effects can be improved by taking the cutoffs for the invariant mass of $W$-pair and the transverse momentum of the final lepton. Our results demonstrate that the NLO QCD corrections to observables are significant, and do not show any improvement for the renormalization/factorization scale uncertainty on the QCD NLO corrected cross section, because the LO result underestimates the scale dependence.

Associated production oftt¯Hin the large extra dimension model at CERN LHC

The large extra dimension model is a promising way to solve the hierarchy problem of the standard model. In this paper we investigate the associated production of $t\overline{t}H$ at the LHC within the large extra dimension model. We present the dependence of the cross section on the fundamental scale ${\mathrm{M}}_{\mathrm{S}}$, and also give the ${p}_{T}$ distribution of the final state particles. The large extra dimension effects enhance the cross section significantly. We also give the discovery limits of ${\mathrm{M}}_{\mathrm{S}}$ on the process $pp\ensuremath{\rightarrow}t\overline{t}H$, which are 14.295, 9.595, 6.93, and 1.235 TeV when the extra dimensions are 3, 4, 5, and 6, respectively.

Classical and non-classical ADD-phenomenology with high-E⊥jet observables at collider experiments

We use the results from a recent investigation of hard parton-parton gravitational scattering in the ADD scenario to make semi-quantitative predictions for a few standard high-ET jet observables at the LHC. By implementing these gravitational scattering results in the Pythia event generator and combining it with the Charybdis generator for black holes, we investigate the effects of large extra dimensions and find that, depending on the width of the brane, the relative importance of gravitational scattering and black hole production may change significantly. For the cases where gravitational scatterings are important we discuss how to distinguish gravitational scattering from standard QCD partonic scatterings. In particular we point out that the universal colorlessness of elastic gravitational scattering implies fewer particles between the hard jets, and that this can be used in order to distinguish an increased jet activity induced by gravitational scattering from an increased jet activity induced by eg. super-symmetric extensions where the interaction is colorful.

Effects of large extra dimensions on associatedtt¯h0production at linear colliders

In the framework of the large extra-dimensions (LED) model, the effects of LED on the processes $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}t\overline{t}{h}^{0}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}{h}^{0}$ at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}t\overline{t}{h}^{0}$ with $\sqrt{s}=3.5\text{ }\mathrm{TeV}$ allows the effective scale ${\ensuremath{\Lambda}}_{T}$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and ${P}_{\ensuremath{\gamma}}=0.9$, $J=2$ polarized $\ensuremath{\gamma}\ensuremath{\gamma}$ collision modes, respectively. For the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}{h}^{0}$ process with $\sqrt{s}=3.5\text{ }\mathrm{TeV}$, the upper limits of ${\ensuremath{\Lambda}}_{T}$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and ${P}_{{e}^{+}}=0.6$, ${P}_{{e}^{\ensuremath{-}}}=0.8$, $\ensuremath{-}+$ polarized ${e}^{+}{e}^{\ensuremath{-}}$ collision modes, respectively. We find the $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}t\overline{t}{h}^{0}$ channel in $J=2$ polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.

Large extra dimension effects in Higgs boson production at linear colliders and Higgs factories

In the framework of quantum gravity propagating in large extra dimensions, the effects of virtual Kaluza-Klein graviton and graviscalar interference with Higgs boson production amplitudes are computed at linear colliders and Higgs factories. The interference of the almost-continuous spectrum of the KK gravitons with the standard model resonant amplitude is finite and predictable in terms of the fundamental D-dimensional Plank scale M_D and the number of extra dimensions \delta. We find that, for M_D ~ 1 TeV and \delta=2, effects of the order of a few percent could be detected for heavy Higgs bosons (m_H>500 GeV) in Higgs production both via WW fusion in e^+e^- colliders and at \mu^+\mu^- Higgs-boson factories.

Stellar evolution and large extra dimensions

We discuss in detail the information on large extra dimensions which can be derived in the framework of stellar evolution theory and observation. The main effect of large extra dimensions arises from the production of the Kaluza-Klein (KK) excitations of the graviton. The KK-graviton and matter interactions are of gravitational strength, so the KK states never become thermalized and always freely escape. In this paper we first pay attention to the sun. Production of KK gravitons is incompatible with helioseismic constraints unless the 4+ n dimensional Planck mass M s exceeds 300 GeV/ c 2. Next we show that stellar structures in their advanced phase of H burning evolution put much more severe constraints, M s >3–4 TeV/ c 2, improving on current laboratory lower limits.

Spin configuration of top quark pair production with large extra dimensions at photon-photon colliders

Top quark pair production at photon-photon colliders is studied in low scale quantum gravity scenario. From the dependence of the cross sections on the spin configuration of the top quark and anti-quark, we introduce a new observable, top spin asymmetry. It is shown that there exists a special top spin basis where with the polarized parent electron beams the top spin asymmetry vanishes in the standard model but retains substantial values with the large extra dimension effects. We also present lower bounds of the quantum gravity scale $M_S$ from total cross sections with various combinations of the laser, electron beam, and top quark pair polarizations. The measurements of the top spin state $(t_\uparrow\bar{t}_\downarrow)$ with unpolarized initial beams are shown to be most effective, enhancing by about 5% the $M_S$ bounds with respect to totally unpolarized case.

Large extra dimension effects on the spin configuration of the top quark pair ate+e−colliders

Large extra dimension effects on the spin configuration of the top quark pair at the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}$ process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from standard model (SM) predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin states of the top quark pair, which vanish in the SM; they weaken the pure dominance of the processes, the up-down (down-up) spin states for the left-handed (right-handed) beam. In addition it is shown that the angular cut $\ensuremath{-}0.5&lt;\mathrm{cos}\ensuremath{\theta}&lt;0$ is very effective to determine the sign of the quantum gravity corrections.

Polarization effects on the e +e −→ W+W− process with large extra dimensions

We study large extra dimension effects on the polarizations of the W pair and electron beam at the e +e −→ W + W − process. It is shown that the measurements of the cross section for transversely polarized W pair with the right-handed electron beam remarkably enhance the possibilities to see the low scale quantum gravity effects. Higher Linear Collider bounds on the string scale in this model can be obtained by using the left-handed electron beam.