Search For Extra Dimensions Research Articles

Brane-world extra dimensions in light of GW170817

The search for extra dimensions is a challenging endeavor to probe physics beyond the Standard Model. The joint detection of gravitational waves (GW) and electromagnetic (EM) signals from the merging of a binary system of compact objects like neutron stars (NS), can help constrain the geometry of extra dimensions beyond our 3+1 spacetime ones. A theoretically well-motivated possibility is that our observable Universe is a 3+1-dimensional hypersurface, or brane, embedded in a higher 4+1-dimensional Anti-de Sitter (AdS$_5$) spacetime, in which gravity is the only force which propagates through the infinite bulk space, while other forces are confined to the brane. In these types of brane-world models, GW and EM signals between two points on the brane would, in general, travel different paths. This would result in a time-lag between the detection of GW and EM signals emitted simultaneously from the same source. We consider the recent near-simultaneous detection of the GW event GW170817 from the LIGO/Virgo collaboration, and its EM counterpart, the short gamma-ray burst GRB170817A detected by the Fermi Gamma-ray Burst Monitor and the INTEGRAL Anti-Coincidence Shield spectrometer. Assuming the standard $\Lambda$-Cold Dark Matter ($\Lambda$CDM) scenario and performing a likelihood analysis which takes into account astrophysical uncertainties associated to the measured time-lag, we set an upper limit of $\ell \lesssim 0.535\,$Mpc at $68\%$ confidence level on the AdS$_5$ radius of curvature $\ell$. Although the bound is not competitive with current Solar System constraints, it is the first time that data from a multi-messenger GW-EM measurement is used to constrain extra-dimensional models. Thus, our work provides a proof-of-principle for the possibility of using multi-messenger astronomy for probing the geometry of our space-time.

Gravitons in multiply warped scenarios: At 750 GeV and beyond

The search for extra dimensions has so far yielded no positive results at the LHC. Along with the discovery of a 125 $$\, {\mathrm{GeV}}$$ Higgs boson, this implies a moderate degree of fine-tuning in the parameter space of the Randall–Sundrum model. Within a six-dimensional warped compactification scenario, with its own interesting phenomenological consequences, the parameters associated with the additional spatial direction can be used to eliminate the need for fine-tuning. We examine the constraints on this model due to the 8 $$\, {\mathrm{TeV}}$$ LHC data and survey the parameter space that can be probed at the 14 $$\, {\mathrm{TeV}}$$ run of the LHC. We also identify the region of parameter space that is consistent with the recently reported excess in the diphoton channel in the 13 $$\, {\mathrm{TeV}}$$ data. Finally, as an alternative explanation for the observed excess, we discuss a scenario with brane-localized Einstein–Hilbert terms with Standard Model fields in the bulk.

Searches for extra dimensions with the ATLAS and CMS detectors

Models with extra spatial dimensions have been proposed to explain the large apparent hierarchy between the Electroweak and Planck scales. Such models predict a host of different new phenomena observable at the energy scale in reach with the LHC. Searches for these phenomena with the full 8 TeV LHC dataset taken with the ATLAS and CMS detectors are presented for different topologies. The exchange of gravitons propagating through the extra dimensions can lead to resonant or non-resonant enhancements in high mass tails. Semi-classical and quantum black holes could form and their decays provide for different spectacular signatures.

Searches for extra spatial dimensions with the CMS detector at the LHC

The success of the first three years of operations of the CERN Large Hadron Collider (LHC) at center-of-mass energies of 7 TeV and 8 TeV radically changed the landscape of searches for new physics beyond the Standard Model (BSM) 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 Compact Muon Solenoid (CMS) detector is presented, along with prospects for future searches at the full energy of the LHC, expected to be reached in the next few years.

Search for extra dimensions in diphoton events from proton–proton collisions at TeV in the ATLAS detector at the LHC

The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton–proton collisions at recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb−1. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall–Sundrum model, a lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of . Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower limit on the Randall–Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for .

Search for extra dimensions using diphoton events in 7 TeV proton–proton collisions with the ATLAS detector

Using data recorded in 2011 with the ATLAS detector at the Large Hadron Collider, a search for evidence of extra spatial dimensions has been performed through an analysis of the diphoton final state. The analysis uses data corresponding to an integrated luminosity of 2.12 fb−1 of s=7 TeV proton–proton collisions. The diphoton invariant mass (mγγ) spectrum is observed to be in good agreement with the expected Standard Model background. In the large extra dimension scenario of Arkani-Hamed, Dimopoulos and Dvali, the results provide 95% CL lower limits on the fundamental Planck scale between 2.27 and 3.53 TeV, depending on the number of extra dimensions and the theoretical formalism used. The results also set 95% CL lower limits on the lightest Randall–Sundrum graviton mass of between 0.79 and 1.85 TeV, for values of the dimensionless coupling k/M¯Pl varying from 0.01 to 0.1. Combining with previously published ATLAS results from the dielectron and dimuon final states, the 95% CL lower limit on the Randall–Sundrum graviton mass for k/M¯Pl=0.01 (0.1) is 0.80 (1.95) TeV.

Methods and applications of gravity resonance spectroscopy within the qBounce experiment

We give a short overview of the gravity resonance spectroscopy methods used recently by the qBounce experiment. It has been demonstrated that mechanically induced transitions between bound neutron states in the gravitational field can be observed. Applications of this new method test Newton's gravity law, search for extra dimensions of space-time, and study the neutrality of the neutron.

Search for extra dimensions in the diphoton final state with ATLAS

The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, has been addressed in some models through the existence of extra spatial dimensions. A search for evidence of extra spatial dimensions has been performed, through an analysis of the diphoton final state in data recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. The analysis uses a dataset of 2.12 fb-1 of proton-proton collisions at sqrts=7 TeV. The diphoton invariant mass spectrum is observed to be in good agreement with the expected Standard Model (SM) background. We set 95 CL lower limits on the fundamental Planck scale in the context of the Arkani-Hamed, Dimopoulos, Dvali model (ADD) and on the lightest Kaluza Klein (KK) excitation mass in the context of the Randall-Sundrum model (RS).

Searches for extra dimensions in the CMS experiment at the Large Hadron Collider (LHC)

Predictions of multidimensonal theories are analyzed, and the possibility of detecting signals from extra spatial dimensions in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) is studied.

Search for Extra Dimensions with the CMS Detector

Multidimensional theories at TeV energies, as given in the brane world scenarios with large or compact extra spatial dimensions (ED), are discussed. One interesting feature of recent ED models is the rich low-energy phenomenology that originates from the Kaluza-Klein spectrum of various particles propagating in ED. A series of searches is addressed in the CMS experiment with different signatures.

SEARCHES FOR EXTRA DIMENSIONS AND Z′ BOSONS AT DØ

We present results on the searches for Extra Dimensions and Z′ Bosons conducted at the Tevatron's DØ Detector using dielectron, diphoton, and dimuon final states. The theoretical frameworks of Large Extra Dimensions (LED), Randall-Sundrum Extra Dimensions (RS), TeV-1 Extra Dimensions, and Z′ bosons are explored in the dielectron and diphoton channels, while LED and Z′ bosons are also searched for in the dimuon final state. In the absence of signals we find lower 95% confidence level (CL) limits on the mass of a SM-like Z′ boson of 780 GeV and 680 GeV in the dielectron and dimuon channels, respectively. Furthermore, we find a lower 95% CL limit of 1.12 TeV on the TeV-1 compactification scale ( M C) in the dielectron channel. In the diEM channel and LED framework we set a lower 95% CL limit of 1.43 TeV (GRW) on the fundamental Planck scale ( M S). Using a dimuon final state we find a lower 95% CL limit of 1.1 TeV (GRW) on M S. We also find a lower 95% CL mass limit of 785 GeV on a RS graviton decaying into a dielectron or diphoton final state.

Search for extra dimensions at hadron colliders

To explain the large difference between the Planck scale and the electroweak scale, models in which gravity propagates in more than four dimensions have recently been proposed. In this paper, results from searches for extra dimensions at the Tevatron ppbar collider are presented. Limits are set on the higher dimensional Planck scale, and expectations for the LHC pp collider are given.

Search for extra dimensions in boson and fermion pair production in e +e − interactions at LEP

Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects of these new interactions in boson and fermion pair production are searched for in the data sample collected at centre-of-mass energies above the Z pole by the L3 detector at LEP. In addition, the direct production of a graviton associated with a Z boson is investigated. No statistically significant hints for the existence of these effects are found and lower limits in excess of 1 TeV are derived on the scale of this new theory of gravity.