1. 1 Dejan Stojkovic SUNY at Buffalo Black holes and extra dimensions Workshop on Tests of Gravity and Gravitational Physics May 19-21, 2009 CWRU, Cleveland, Ohio Workshop on Tests of Gravity and Gravitational Physics May 19-21, 2009 CWRU, Cleveland, Ohio

2. Brane world models → large extra dimensions Black holes are the most interesting and intriguing solutions of Einstein's equations Extra dimensions seem to be necessary in an ultimate theory of high energy physics Motivation Higher dim. black holes as classical solutions Black holes in accelerators!

3. Outline Outline Black Max: event generator Black Max: event generator

4. 4

5. 5 Arkani-Hamed, Dimopoulos and Dvali, Phys. Lett. B 429, 263 (1998) Antoniadis, Arkani-Hamed, Dimopoulos and Dvali, Phys. Lett. B 436,257 (1998) Arkani-Hamed, Dimopoulos and Dvali, Phys. Lett. B 429, 263 (1998) Antoniadis, Arkani-Hamed, Dimopoulos and Dvali, Phys. Lett. B 436,257 (1998) Strong gravity: ADD model Our universe consists of: Our universe consists of: 3+n space-like dimensions (bulk) 3+n space-like dimensions (bulk) n dimensions compactified to radius R n dimensions compactified to radius R Our universe consists of: Our universe consists of: 3+n space-like dimensions (bulk) 3+n space-like dimensions (bulk) n dimensions compactified to radius R n dimensions compactified to radius R Only gravitons are allowed to propagate in all dimensions Only gravitons are allowed to propagate in all dimensions SM particles are bound to 3-dim submanifold (brane) SM particles are bound to 3-dim submanifold (brane) Only gravitons are allowed to propagate in all dimensions Only gravitons are allowed to propagate in all dimensions SM particles are bound to 3-dim submanifold (brane) SM particles are bound to 3-dim submanifold (brane)

6. 6 In this framework: Gravity is as strong as the other interactions Gravity is as strong as the other interactions But gravitational force is diluted due to the presence of extra dimensions But gravitational force is diluted due to the presence of extra dimensions Gravity is as strong as the other interactions Gravity is as strong as the other interactions But gravitational force is diluted due to the presence of extra dimensions But gravitational force is diluted due to the presence of extra dimensions Weak gravity is only an illusion for an observer located on the brane

7. 7 Models with low scale quantum gravity Quantum gravity energy scale is usually thought to be very high If this is true it does not make much sense to talk about black holes in accelerators Quantum gravity energy scale is usually thought to be very high If this is true it does not make much sense to talk about black holes in accelerators Recently, proposed models with quantum gravity energy scale Recently, proposed models with quantum gravity energy scale Recently, proposed models with quantum gravity energy scale Recently, proposed models with quantum gravity energy scale HOWEVERHOWEVER

8. 8 If If We can talk about non-perturbative quantum gravity effects in accelerators Mini Black Holes If If We can talk about non-perturbative quantum gravity effects in accelerators Mini Black Holes

9. 9. If an impact parameter b is smaller than 2R H for a given E c Black holes in accelerators Trans-Planckian energies

10. 10 The total black hole production cross section in pp collison is: The total black hole production cross section in pp collison is: The sum runs over all partons in the proton The sum runs over all partons in the proton is the proton-proton COM energy is the proton-proton COM energy are the parton distribution functions are the parton distribution functions is the momentum fraction carried by an i-th parton is the momentum fraction carried by an i-th parton is the momentum transfer is the momentum transfer is the minimal energy needed to form a black hole is the minimal energy needed to form a black hole The total black hole production cross section in pp collison is: The total black hole production cross section in pp collison is: The sum runs over all partons in the proton The sum runs over all partons in the proton is the proton-proton COM energy is the proton-proton COM energy are the parton distribution functions are the parton distribution functions is the momentum fraction carried by an i-th parton is the momentum fraction carried by an i-th parton is the momentum transfer is the momentum transfer is the minimal energy needed to form a black hole is the minimal energy needed to form a black hole

11. 11 Large Hadron Collider → CERN (2008) Numerical estimates : LHC - black hole factory! 10 7 black holes per year if M * =1 TeV LHC: E c =14 TeV

12. 12 BH event may have a distinct signature in accelerators! BH event may have a distinct signature in accelerators! Number of particles emitted equal to black hole entropy: Number of particles emitted equal to black hole entropy: E.g. 5 TeV black hole emits of the order of 30 particles E.g. 5 TeV black hole emits of the order of 30 particles Number of particles emitted equal to black hole entropy: Number of particles emitted equal to black hole entropy: E.g. 5 TeV black hole emits of the order of 30 particles E.g. 5 TeV black hole emits of the order of 30 particles Life-time of a small black hole very short : Life-time of a small black hole very short : TeV black hole lives 10 -27 seconds TeV black hole lives 10 -27 seconds → disappears almost instantaneously → disappears almost instantaneously Life-time of a small black hole very short : Life-time of a small black hole very short : TeV black hole lives 10 -27 seconds TeV black hole lives 10 -27 seconds → disappears almost instantaneously → disappears almost instantaneously

13. 13 Schwarzschild-like solution (non-rotating) Schwarzschild-like solution (non-rotating) Higher dimensional black hole solutions Higher dimensional black hole solutions Kerr-like solution (rotating): 5D Kerr-like solution (rotating): 5D

14. V. Frolov, D. Stojkovic, Phys.Rev.D67:084004,2003; Phys.Rev.D68:064011,2003 Five-dimensional rotating black holes: theory Five-dimensional rotating black holes: theory Timescale: 30 years 30 years Timescale: Timescale: 2 months 2 months Timescale:

15. 15 λ T > R S point radiator λ T > R S point radiator s-mode dominant s-mode dominant radiates equally in all directions λ T > R S point radiator λ T > R S point radiator s-mode dominant s-mode dominant radiates equally in all directions Number of degrees of freedom much larger on the brane ? (60 SM particles vs. 1 graviton) Number of degrees of freedom much larger on the brane ? (60 SM particles vs. 1 graviton) R. Emparan, G. Horowitz, R. Myers, Phys. Rev. Lett. 85 499 (2000) “Black holes radiate mostly on the brane” R. Emparan, G. Horowitz, R. Myers, Phys. Rev. Lett. 85 499 (2000) “Black holes radiate mostly on the brane” Where do black holes mostly radiate? Brane or Bulk?

16. # of degrees of freedom of gravitons in the N+1-dimensional space-time is: # of degrees of freedom of gravitons in the N+1-dimensional space-time is: Objection 1: Objection 1: Objection 2: Objection 2: V. Frolov, D. Stojkovic, Phys. Rev. Lett. 89:151302 (2002) Black holes radiate mostly OFF the brane ! Black holes radiate mostly OFF the brane ! At least as long as they are rotating fast

17. 17 Any particle emitted in the bulk can cause a recoil of the black hole from the brane Any particle emitted in the bulk can cause a recoil of the black hole from the brane V. Frolov, D. Stojkovic, Phys. Rev. Lett. 89:151302 (2002) Recoil due to Hawking radiation can be very significant for small black holes (energy of emitted particles comparable to the mass of the black hole) Recoil due to Hawking radiation can be very significant for small black holes (energy of emitted particles comparable to the mass of the black hole) Consequences: Consequences: i) black hole radiation would be suddenly terminated i) black hole radiation would be suddenly terminated ii) observer located on the brane would register apparent ii) observer located on the brane would register apparent energy non-conservation energy non-conservation Consequences: Consequences: i) black hole radiation would be suddenly terminated i) black hole radiation would be suddenly terminated ii) observer located on the brane would register apparent ii) observer located on the brane would register apparent energy non-conservation energy non-conservation Recoil Effect

18. 18 _ J = 0 _ J = ¼¾ar H cos 2 ® Friction between the black hole and the brane V. Frolov, D. Fursaev, D. Stojkovic, CQG, 21:3483 (2004) D. Stojkovic, Phys. Rev. Lett. 94: 011603 (2005) V. Frolov, D. Fursaev, D. Stojkovic, CQG, 21:3483 (2004) D. Stojkovic, Phys. Rev. Lett. 94: 011603 (2005) Rate of loss of the angular momentum final stationary equilibrium configuration is: Rate of loss of the angular momentum final stationary equilibrium configuration is:

19. 19 ® = ¼ = 2 _ J = 0 _ J = ¼¾ar H cos 2 ® Evaporation of a black hole off of a tense brane D. Dai, N. Kaloper, G. Starkman, D. Stojkovic, Phys.Rev.D75:024043,2007 6D black hole on a co-dimension 2 brane deficit angle horizon radius

20. 20 J. Feng, A. Shapere, Phys. Rev. Lett. 88:021303 (2002 ) Black Holes from Cosmic Rays Black Holes from Cosmic Rays Cosmic rays are Nature's free collider Observed events produce COM energy of 100 TeV If M * ≈1TeV (quantum gravity energy scale), then small black holes can be produced in the atmosphere Proposed mechanism: - neutrino-nucleon scattering deep in the atmosphere Cosmic rays are Nature's free collider Observed events produce COM energy of 100 TeV If M * ≈1TeV (quantum gravity energy scale), then small black holes can be produced in the atmosphere Proposed mechanism: - neutrino-nucleon scattering deep in the atmosphere

21. 21 Cosmic neutrinos Cosmic protons scatter off the cosmic microwave background to create ultra-high energy neutrinos These neutrinos enter Earth's atmosphere They have very weak SM interactions Dominant interaction: Cosmic neutrinos Cosmic protons scatter off the cosmic microwave background to create ultra-high energy neutrinos These neutrinos enter Earth's atmosphere They have very weak SM interactions Dominant interaction:

22. 22 Neither strong nor electromagnetic interactions can degrade the neutrino energy before it interacts quantum-gravitationally Neutrino interaction length is far longer than the thickness of the Earth's atmosphere Neutrinos can produce black holes uniformly at all atmospheric depths Protons and photons interact high in atmosphere and cause vertical showers Neutrinos → Protons → The most promising signal for neutrinos: - quasi-horizontal showers initiated by neutrinos deep in the atmosphere - far above the standard model rate Neither strong nor electromagnetic interactions can degrade the neutrino energy before it interacts quantum-gravitationally Neutrino interaction length is far longer than the thickness of the Earth's atmosphere Neutrinos can produce black holes uniformly at all atmospheric depths Protons and photons interact high in atmosphere and cause vertical showers Neutrinos → Protons → The most promising signal for neutrinos: - quasi-horizontal showers initiated by neutrinos deep in the atmosphere - far above the standard model rate Crucial points:

23. 23 The total black hole production cross section in neutrino-nucleon scattering is:The total black hole production cross section in neutrino-nucleon scattering is: The sum runs over all partons in the nucleon The sum runs over all partons in the nucleon are the parton distribution functions are the parton distribution functions is momentum transfer is momentum transfer The cross section for black hole production is found to be several orders of The cross section for black hole production is found to be several orders of magnitude higher than the SM cross section for magnitude higher than the SM cross section for if M * ≈1-10TeV if M * ≈1-10TeV The total black hole production cross section in neutrino-nucleon scattering is:The total black hole production cross section in neutrino-nucleon scattering is: The sum runs over all partons in the nucleon The sum runs over all partons in the nucleon are the parton distribution functions are the parton distribution functions is momentum transfer is momentum transfer The cross section for black hole production is found to be several orders of The cross section for black hole production is found to be several orders of magnitude higher than the SM cross section for magnitude higher than the SM cross section for if M * ≈1-10TeV if M * ≈1-10TeV

24. 24 Best current setup for cosmic ray studies Located in Argentina (Pampa Amarillas) Best current setup for cosmic ray studies Located in Argentina (Pampa Amarillas) 1600 Water Cerenkov ground arrays 4 air fluorescence telescopes spread over 3000 km 2 1600 Water Cerenkov ground arrays 4 air fluorescence telescopes spread over 3000 km 2 Pierre Auger Auger Observatory Auger Observatory

25. 25 Numerical estimates: Numerical estimates: - Auger can detect ~ 100 black holes in 3 years (i.e. BEFORE the LHC data become available) (i.e. BEFORE the LHC data become available) This could be the first window into extra dimensions This could be the first window into extra dimensions USA Today version: USA Today version: "Dozens of tiny black holes may be forming right over our heads... A new observatory might start spotting signs of the tiny terrors, A new observatory might start spotting signs of the tiny terrors, say physicists Feng and Shapere. They're harmless and pose no say physicists Feng and Shapere. They're harmless and pose no threat to humans." threat to humans." Numerical estimates: Numerical estimates: - Auger can detect ~ 100 black holes in 3 years (i.e. BEFORE the LHC data become available) (i.e. BEFORE the LHC data become available) This could be the first window into extra dimensions This could be the first window into extra dimensions USA Today version: USA Today version: "Dozens of tiny black holes may be forming right over our heads... A new observatory might start spotting signs of the tiny terrors, A new observatory might start spotting signs of the tiny terrors, say physicists Feng and Shapere. They're harmless and pose no say physicists Feng and Shapere. They're harmless and pose no threat to humans." threat to humans."

26. Auger has reported some interesting results but NO black hole events! Auger has reported some interesting results but NO black hole events! 26 Six years after… Are TeV scale gravity models already excluded?

27. 27 "Science may be described as the art of systematic over-simplification.“ Karl Popper, The Observer, August 1982 "Science may be described as the art of systematic over-simplification.“ Karl Popper, The Observer, August 1982

28. 28 Some things have their natural habitat in the "grand desert“ that is destroyed by a low scale gravity Like proton stability, neutrino masses... Low scale quantum gravity implies very fast proton decay! Some things have their natural habitat in the "grand desert“ that is destroyed by a low scale gravity Like proton stability, neutrino masses... Low scale quantum gravity implies very fast proton decay! Model Building Model Building

29. 29 Gauging the baryon number One way out is to gauge the baryon number → promote a U(1) B into a gauge symmetry Problems: Baryogenesis - Before: "We exist → proton must be stable“ - After: "We exist → proton must be unstable“ To avoid a new long range interaction, U(1) B must be broken down to some discrete gauge symmetry Arranging for anomaly cancellation Gauge couplings unification So far, gauging the baryon number has not proved very attractive! Gauging the baryon number One way out is to gauge the baryon number → promote a U(1) B into a gauge symmetry Problems: Baryogenesis - Before: "We exist → proton must be stable“ - After: "We exist → proton must be unstable“ To avoid a new long range interaction, U(1) B must be broken down to some discrete gauge symmetry Arranging for anomaly cancellation Gauge couplings unification So far, gauging the baryon number has not proved very attractive! Saving Proton Saving Proton

30. 30 An alternative: Split Fermions An alternative: Split Fermions N. Arkani-Hamed, M. Schmaltz, Phys. Rev. D 61:033005 (2000) In order to suppress a direct QQQL coupling we must separate quarks form leptons Quarks and leptons are localized at different points on a thick brane Or alternatively, on different branes The model yields exponentially small coupling (wave function overlap) between quarks and leptons Dangerous QQQL interaction is suppressed An alternative: Split Fermions An alternative: Split Fermions N. Arkani-Hamed, M. Schmaltz, Phys. Rev. D 61:033005 (2000) In order to suppress a direct QQQL coupling we must separate quarks form leptons Quarks and leptons are localized at different points on a thick brane Or alternatively, on different branes The model yields exponentially small coupling (wave function overlap) between quarks and leptons Dangerous QQQL interaction is suppressed

31. 31 The propagator between fermions which are separated in extra dimensions (in the high energy and high momentum transfer limit) is d: separation between the quarks and leptons σ: the width of the fermion wave function The propagator has the usual 4-dim form except that the coupling is suppressed by the exponentially small wave function overlap Suppression factor of (which can be achieved for a rather modest hierarchy of ) completely saves the proton! completely saves the proton! The propagator between fermions which are separated in extra dimensions (in the high energy and high momentum transfer limit) is d: separation between the quarks and leptons σ: the width of the fermion wave function The propagator has the usual 4-dim form except that the coupling is suppressed by the exponentially small wave function overlap Suppression factor of (which can be achieved for a rather modest hierarchy of ) completely saves the proton! completely saves the proton!

32. 32 Consequences: the price we to have pay Consequences: the price we to have pay Spatial separation between the quark and lepton wave functions Spatial separation between the quark and lepton wave functions successfully suppresses proton decay successfully suppresses proton decay However, this implies strong consequences for cosmic ray However, this implies strong consequences for cosmic ray neutrino scattering off the atmosphere neutrino scattering off the atmosphere The correct black hole production cross section in collisions of The correct black hole production cross section in collisions of neutrinos with each quark in a nucleon is not neutrinos with each quark in a nucleon is not The correct cross section is multiplied by the large suppression factor of The correct cross section is multiplied by the large suppression factor of Consequences: the price we to have pay Consequences: the price we to have pay Spatial separation between the quark and lepton wave functions Spatial separation between the quark and lepton wave functions successfully suppresses proton decay successfully suppresses proton decay However, this implies strong consequences for cosmic ray However, this implies strong consequences for cosmic ray neutrino scattering off the atmosphere neutrino scattering off the atmosphere The correct black hole production cross section in collisions of The correct black hole production cross section in collisions of neutrinos with each quark in a nucleon is not neutrinos with each quark in a nucleon is not The correct cross section is multiplied by the large suppression factor of The correct cross section is multiplied by the large suppression factor of 10 -52 10 -52

33. 33 Proton contains other partons besides quarks: Proton contains other partons besides quarks: e.g. gluons, other gauge bosons etc. e.g. gluons, other gauge bosons etc. However: However: Once you separate leptons from quarks, higher order processes Once you separate leptons from quarks, higher order processes are also highly suppressed are also highly suppressed by exponential wave function suppression factors by exponential wave function suppression factors by power law volume suppression factors by power law volume suppression factors … Proton contains other partons besides quarks: Proton contains other partons besides quarks: e.g. gluons, other gauge bosons etc. e.g. gluons, other gauge bosons etc. However: However: Once you separate leptons from quarks, higher order processes Once you separate leptons from quarks, higher order processes are also highly suppressed are also highly suppressed by exponential wave function suppression factors by exponential wave function suppression factors by power law volume suppression factors by power law volume suppression factors …

34. 34 Non-observation of BH events at the Auger likely has no implications for the LHC Non-observation of BH events at the Auger likely has no implications for the LHC

35. 35 Black holes might still be produced in NN or γN scatterings Problems: The Earth's atmosphere is not transparent to nucleons or photons as it is to neutrinos SM interactions much stronger One can not expect quasi-horizontal showers deep in the atmosphere No distinct experimental signature of BH production! Black holes might still be produced in NN or γN scatterings Problems: The Earth's atmosphere is not transparent to nucleons or photons as it is to neutrinos SM interactions much stronger One can not expect quasi-horizontal showers deep in the atmosphere No distinct experimental signature of BH production!

36. 36

37. 37 Neutron-antineutron oscillations are described by uddudd operator Limits on oscillations require splitting between u and d quarks Consequences Consequences As the separation between quarks increases, the maximum 3+1-dim impact parameter that results in black hole creation decreases the production cross section goes down the production cross section goes down the bulk component of angular momentum grows the bulk component of angular momentum grows Neutron-antineutron oscillations are described by uddudd operator Limits on oscillations require splitting between u and d quarks Consequences Consequences As the separation between quarks increases, the maximum 3+1-dim impact parameter that results in black hole creation decreases the production cross section goes down the production cross section goes down the bulk component of angular momentum grows the bulk component of angular momentum grows D. Dai, D. Stojkovic, G. Starkman, D. Dai, D. Stojkovic, G. Starkman, Phys.Rev.D73:104037,2006 Implications of split fermions for the LHC

38. 38 Implications of split fermions for the LHC

39. 39 Black Max Black Max “BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension” D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng “BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension” D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng

40. 40 Black Max procedure

41. 41 Black Max output Black Max output BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng

42. 42 BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng Black Max output Black Max output

43. 43 BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng Black Max output Black Max output

44. 44 BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension. D. Dai, G. Starkman, D. Stojkovic, C. Issever, E. Rizvi, J. Tseng Phys.Rev.D77:076007,2008 D. DaiG. StarkmanD. StojkovicC. IsseverE. RizviJ. Tseng Black Max output Black Max output

45. Conclusions Conclusions

47. 47