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Signatures of L arge e X tra D imensions

Signatures of L arge e X tra D imensions. LXD-Group ITP Frankfurt Marcus Bleicher, Sabine Hossenfelder (Tucson), Stefan Hofmann (Stockholm), Lars Gerland (TelAviv), Kerstin Paech, Jörg Ruppert, Christoph Rahmede, Sascha Vogel, Horst Stöcker, Benjamin Koch. Outline.

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Signatures of L arge e X tra D imensions

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  1. Signatures of Large eXtra Dimensions • LXD-Group ITP Frankfurt Marcus Bleicher, Sabine Hossenfelder (Tucson), Stefan Hofmann (Stockholm), Lars Gerland (TelAviv), Kerstin Paech, Jörg Ruppert, Christoph Rahmede, Sascha Vogel, Horst Stöcker, Benjamin Koch

  2. Outline • Motivation: why eXtra dimensions • Models with eXtra dimensions ADD & RS • Observable signatures for eXtra dimensions • Summary

  3. The Standard Model (SM) Very successfull effective quantum-field-theory of electroweak and strong interactions • Problems: • Gravitation missing • why is gravitation so weak (hierarchy problem) • quantisation of gravity • Too many parameters to be really fundamental • Why Higgs so light (finetuning problem) • ... LXDs

  4. Large eXtra Dimensions • Models with extra dimensions: • Arkani-Hamed, Dimopoulos & Dvali (ADD) • Randall & Sundrum (RS) • Universal Extra Dimensions (UXD) All contain one or more eXtra dimensions that are compactified on a radius that is so small that it could not be observed up to now. * Large means large compared to Planck length: ...

  5. The ADD - model • 3+d spacelike dimensions • d dimensions on d-torus with radii R • all standard model fields live only in 4-dim. spacetime (brane) • only gravity propagates in all dimensions (bulk) This leads to a modification of Newton´s law:

  6. Gravitons in accelerator experiments • excitations of gravitons look on the brane like massive • particles: • From phase space one finds with that the cross section • for graviton production for example in • behaves like: • Measurement via energy loss:

  7. Black holes in accelerator experiments • Modification of Newton´s law at distances smaller than R • leads to increase of the Schwarzschild radius • Particles that get closer than RH form a horizon. • up to black holes • might be produced at LHC • per year.

  8. LXDs in Astrophysics • Strongest constraints on size of eXtra dimensions from supernova and neutron star observations: • Observed neutrino flux from SN1987a • Non observed flux of decay products of massive • gravitons from SN and neutron stars Hannestad & Raffelt 2002

  9. Minimal length • Higher dimensional space-time and the existence of • a minimal length scale are intrinsic features of string theory and quantum gravity • Minimal length can be modeled by setting • with minimal possible compton wavelength • this changes basic quantum mechanics

  10. Observation of minimal length • Modification of SM cross sections at high energies • Modification of the gyromagnetic moment of electrons • and myons. independent of number of eXtra dimensions Harbach et al. 2004

  11. Summary • Soon we might be able to look behind the SM • Simple models like LXD + minimal length don´t claim • to a TOE... • ...but provide useful basis to probe general features of • spacetime like • - value of new scale • - number and size of eXtra dimensions • - existence of minimal length • Model yields predictions for astro- & collider-physics • May help to learn about • - structure of quantum gravity • - mechanism of unification

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