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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
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


Outline
Outline

  • Motivation: why eXtra dimensions

  • Models with eXtra dimensions ADD & RS

  • Observable signatures for eXtra dimensions

  • Summary


The standard model sm
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


L arge e x tra d imensions
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: ...


The add model
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:


Gravitons in accelerator experiments
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:


Black holes in accelerator experiments
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.


Lxd s in astrophysics
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


Minimal length
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


Observation of minimal length
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


Summary
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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