Was Einstein right or are there extra space-time dimensions?

1. Was Einstein right or are there extra space-time dimensions? Nigel Glover Institute for Particle Physics Phenomenology Durham University

2. Standard Model of Particle Physics 1974 1949 1937 1995 1977 1976

3. Standard Model of Particle Physics 1979 1983 Higgs, H? 1983 Gravity not here! Much too weak – 1040 times weaker than the strong force Only becomes strong at the Planck scale 1019 GeV String theory best candidate for quantum gravity

4. What are they? Why are we asking the question? Why haven’t we found them yet? What are their consequences? How are we going to find evidence for them? Extra Dimensions?

5. Where are the extra dimensions? From a distance, we see only the rope – one dimension From close up, the ant sees two dimensions So far, we only see three space dimensions because we haven’t been able to resolve them

6. One possibility is that we live in a subspace of the extra dimensions All particles and most forces might be confined to our world: photons (electromagnetism), electrons, protons, … Extra Dimensions w, v,… gravity E&M x, y, z But gravity, the weakest of the four forces, might be able to propagate in the extra dimensions

7. Extra dimensions could explain why gravity is so weak! Gravitational flux lines travel into the normal dimensions M Potential falls off as V ~ G3/r and into the extra dimensions for r < L: gravitational potential is increased in proportion Potential falls off as V ~ Gd/rd-2 L

8. EM … Strength gravity r 1/mstrong This changes the force of gravity Gravity could become strong at small distances!

9. Making Black Holes! • Lots of mass/energy in a small volume  black hole • If two particles pass close enough with enough energy, they will form a microscopic black hole • For 3 spatial dimensions, gravity is too weak for this to happen. But with extra dimensions, gravity becomes stronger, micro black holes could be created in particle collisions!

10. S. Harris Micro Black Holes • Where could they be produced? • How will we know if we’ve seen one?

11. g g Black Holes • Classically, light and other particles do not escape; black holes are black. • But quantum mechanically, black holes Hawking radiate; black holes emit light

12. Black Hole Evaporation • “Normal” black holes: Mass: MBH ~ Msun Size: kilometer Temperature: 0.01 K Lifetime: ~ forever • Micro black holes: Mass: MBH ~ 1000 Mproton Size: 10-18 m Temperature: 1016 K Lifetime: 10-27 s They explode!

13. Extra Dimensional Matter • A particle moving in an extra dimension of size L appears to us as a set of particles with masses 0, 1/L, 2/L, 3/L, 4/L, … • Each known particle has a heavy partner at each mass level. • We can search for these particles by looking for their decay into lighter particles … 4/L 3/L 2/L mass 1/L 0

14. The Large Hadron Collider at CERN World’s most powerful particle accelerator Superconducting magnets – 8.3T at 1.9K 2 beams of protons will collide 40 million times a second In construction since 1998 Due to start later this year CMS ALICE ATLAS LHCb

15. aside: LHC vs. circle line LHC Circle line Length 27km 22.5km Depth 100m 15m Diameter 3.8m 3.4m

16. LHC Beam Stored Energy 2808 bunches, 1.1 x 1011 protons/bunch @ 7 TeV 350 MJ stored energy per proton beam Same as colliding 2 x 120 elephants... 120 elephants with 40 km/h 120 elephants with 40 km/h eye of a needle: 0.3 mm diameter proton beams at interaction point are 10x smaller: 0.03 mm diameter The energy of a single 7 TeV proton is equivalent to a flying mosquito (1 µJ)

17. LHC Magnet Installation Lowering through an elliptical shaft Storage on car-parks all over CERN Transport with optically guided vehicle Interconnection welding Last connection made 7 November 2007 Quality Control

18. http://lhc.web.cern.ch/lhc/ Cooldown Status (as of 28th Apr 2008, 5pm) sector 12: warm sector 23: 50-150 K sector 34: 180-280 K sector 45: warm sector 56: 1.9 K sector 67: 30-90 K sector 78: 1.9 K sector 81: 1.9 K total cold mass: 40,000 tons 10,000 tons of liquid nitrogen 120 tons of superfluid Helium (1.9 K) for cooling vacuum: 10-10 Torr = 3 million molecules per cm3

19. ATLAS (AToroidal LHC ApparatuS)‏ Length = 55 m Width = 32 m Height = 35 m Construction from Oct 2003 – Mar 2008

20. 15 m 22 m CMS (Compact Muon Spectrometer)‏ main assembly on surface, then lowering into cavern in 5 big parts by ~2500 t crane 210 m2 silicon detectors 4 T ~12,500 t

21. CMS Lowering of 2000 t Central Part (Feb 2007)

22. Black Hole event at ATLAS simulated by CHARYBDIS

23. Are micro black holes dangerous? • On 21 March, Luis Sancho, from Spain, and Hawaii resident Walter Wagner filed a lawsuit in Hawaii's US District Court against CERN and US contributors to the project demanding that they do not operate the LHC until they prove it is safe. • The lawsuit's claims are "complete nonsense", said James Gillies, a spokesman for CERN. "The LHC will start up this year, and it will produce all sorts of exciting new physics and knowledge about the universe," he said, adding: "A year from now, the world will still be here."

24. Summary • Extra dimensions are well-motivated theoretically (string theory) • May lead to micro black hole production or other phenomena at the LHC • May shed light on longstanding puzzles on the weakness of gravity • LHC startup approaching – later this summer • “discoveries are guaranteed…at least the Higgs boson…likely observe new symmetries of nature, new particles and forces” • Biggest leap in energy since discovery of jets/W/Z/SUSY/top at UA1/UA2 in 1983 STFC delivery plan

25. Are micro black holes dangerous? Q What if the micro black holes produced at the LHC do not decay as rapidly as calculated, or might even not be prone to decay and, if unable to rapidly evaporate, they could start interacting, grow larger and potentially be disastrous to Earth itself? A Collisions at these energies (and higher) have been happening in nature for billions of years apparently without hazardous effects, as ultra high energy cosmic rays impact Earth's atmosphere. Q What if the micro black holes created at LHC have less than the Earth's escape velocity (of 11.2 km/s), and therefore would be captured by the Earth's gravitational field? A If so, its very likely that cosmic rays would destroy dense objects like neutron stars/pulsars

26. ATLAS TRIUMF The Sun

27. 7 TeV 5 LHC 5 450 GeV 4 SPS 4 26 GeV 3 PS 2 1.4 GeV 2 BOOSTER 3 50 MeV 1 1 LINAC2 start here PROTONS CERN Accelerator Complex

28. I’ll try to keep it simple…but please ask