Search results for "extra dimension"
showing 10 items of 56 documents
Search for diphoton events with large missing transverse momentum in 7 TeV proton-proton collision data with the ATLAS detector
2012
A search for diphoton events with large missing transverse momentum has been performed using proton–proton collision data at √s = 7 TeV recorded with the ATLAS detector, corresponding to an integrated luminosity of 4.8 fb[superscript −1]. No excess of events was observed above the Standard Model prediction and model-dependent 95% confidence level exclusion limits are set. In the context of a generalised model of gauge-mediated supersymmetry breaking with a bino-like lightest neutralino of mass above 50 GeV, gluinos (squarks) below 1.07 TeV (0.87 TeV) are excluded, while a breaking scale Λ below 196 TeV is excluded for a minimal model of gauge-mediated supersymmetry breaking. For a specific …
Search for Diphoton Events with Large Missing Transverse Energy with 36 pb^-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector
2011
Making use of 36 pb^-1 of proton-proton collision data at sqrt{s} = 7 TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95% Confidence Level (CL) upper limit is set on the cross section for new physics of sigma < 0.38 - 0.65 pb in the context of a generalised model of gauge mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of sigma < 0.18 - 0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95 % CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a low…
Searches for Physics Beyond the Standard Model
2015
Despite its phenomenal success, the Standard Model is not expected to be a complete description of nature all the way up to the Planck scale where quantum gravity comes into play. As the collider at the current energy frontier, the LHC is in a unique position to look for signals of physics beyond the Standard Model. In this chapter, results from the first run of the LHC are surveyed that go beyond the supersymmetric extension of the Standard Model discussed in the previous chapter. At the time of writing, no evidence for new phenomena has been discovered. Instead, the LHC experiments have constrained the parameter space of conceivable models significantly. The most prominent results are on …
Gravity-mediated Scalar Dark Matter in Warped Extra-Dimensions
2020
We revisit the case of scalar dark matter interacting just gravitationally with the Standard Model (SM) particles in an extra-dimensional Randall-Sundrum scenario. We assume that both, the dark matter and the Standard Model, are localized in the TeV brane and only interact via gravitational mediators, namely the graviton Kaluza-Klein modes and the radion. We analyze in detail the dark matter annihilation channel into two on-shell KK-gravitons, and contrary to previous studies which overlooked this process, we find that it is possible to obtain the correct relic abundance for dark matter masses in the range [1, 10] TeV even after taking into account the strong bounds from LHC Run II. We also…
B physics and extra dimensions
2003
We compute the dominant new physics contributions to the processes Z -> b b and B - B in the context of two representative models with extra dimensions. The main thrust of the calculations focuses on how to control the effects of the infinite tower of Kaluza-Klein modes inside the relevant one-loop diagrams. By comparing the results with the existing experimental data, most importantly those for Rb, we show that one may derive interesting lower bounds on the size of the compactification scale Mc.
Neutrinos confronting large extra dimensions
2001
We study neutrino physics in a model with one large extra dimension. We assume the existence of two four-dimensional branes in the five-dimensional space-time, one for the ordinary particles and the other one for mirror particles, and we investigate neutrino masses and mixings in this scheme. Comparison of experimental neutrino data with the predictions of the model leads to various restrictions on the parameters of the model. For instance, the size of the extra dimension, R, turns out to be bounded from below. Cosmological considerations seem to favor a large R. The usual mixing schemes proposed as solutions to the solar and atmospheric neutrino anomalies are compatible with our model.
Power corrections in models with extra dimensions
2004
We critically revisit the issue of power-law running in models with extra dimensions. The general conclusion is that, in the absence of any additional physical principle, the power-corrections tend to depend strongly on the details of the underlying theory.
Dark Energy, Scalar-Tensor Gravity and Large Extra Dimensions
2004
We explore in detail a dilatonic scalar-tensor theory of gravity inspired by large extra dimensions, where a radion field from compact extra dimensions gives rise to quintessence in our 4-dimensional world. We show that the model can give rise to other types of cosmologies as well, some more akin to $k$-essence and possibly variants of phantom dark energy. In our model the field (or radius) stabilization arises from quantum corrections to the effective 4D Ricci scalar. We then show that various constraints nearly determine the model parameters, and give an example of a quintessence-type cosmology consistent with observations. We show that the upcoming SNAP-experiment would easily distinguis…
Search for Large Extra Dimensions in Final States Containing One Photon or Jet and Large Missing Transverse Energy Produced inpp¯Collisions ats=1.96 …
2008
We present the results of searches for large extra dimensions in samples of events with large missing transverse energy E_{T} and either a photon or a jet produced in pp[over ] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II. For gamma+E_{T} and jet+E_{T} candidate samples corresponding to 2.0 and 1.1 fb;{-1} of integrated luminosity, respectively, we observe good agreement with standard model expectations and obtain a combined lower limit on the fundamental parameter of the large extra dimensions model M_{D} as a function of the number of extra dimensions in the model.
Search for diphoton events with large missing transverse momentum in 1 fb−1 of 7 TeV proton–proton collision data with the ATLAS detector
2012
A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics. The limits depend on each model parameter space and vary as follows: sigma < (22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, sigma < (27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8), and sigma < (15-27) fb in t…