OutofthisWorld Physics: From Particles to Black Holes

1
Out-of-this-World Physics From Particles to
Black Holes

• Greg Landsberg
• L.G.Landsberg SymposiumDecember 19, 2005

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Outline

• A Word on Hierarchies
• Standard Model Beauty and the Beast
• How to Make Gravity Strong?
• Looking for Extra Dimensions
• Production of Black Holes at Colliders

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N.B. Large Hierarchies Tend to Collapse...
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Hierarchy of the Standard Model

• Extra dimensions might get rid of the beast while
  preserving the beauty!

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But Keep in Mind

• Fine tuning (required to keep a large hierarchy
  stable) exists in Nature
• Solar eclipse angular size of the sun is the
  same as the angular size of the moon within 2.5
  (pure coincidence!)
• Politics Florida recount, 2,913,321/2,913,144
• 1.000061
• Numerology 987654321/123456789
• 
  8.000000073
• (HW Assignment is it really numerology?)
• But beware the anthropic principle
• Properties of the universe are special because we
  exist in it
• Dont give up science for philosophy so far we
  have been able to explain how the universe works
  entirely by science

6
Math Meets Physics

• Math physics some dimensionalities are quite
  special
• Example Laplace equation in two dimensions has a
  logarithmic solution for any higher number of
  dimensions it obeys the power law
• Some of these peculiarities exhibit themselves in
  condensed matter physics, e.g. diffusion equation
  solution allows for long-range correlations in
  2D-systems (cf. flocking)
• Modern view in topology one dimension is
  trivial two and three spatial dimensions are
  special (properties are defined by the topology)
  any higher number is not
• Do we live in a special space, or only believe
  that we are special?

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The ADD Model

• SM fields are localized on the (31)-brane
  gravity is the only force that feels the bulk
  space
• What about Newtons law?
• Ruled out for infinite extra dimensions, but does
  not apply for sufficiently small compact ones

• Gravity is fundamentally strong force, bit we do
  not feel that as it is diluted by the volume of
  the bulk
• GN 1/MD2 MD ? 1 TeV
• More precisely, from Gausss law
• Amazing as it is, but no one has tested Newtons
  law to distances less than ? 1mm (as of 1998)
• Thus, the fundamental Planck scale could be as
  low as 1 TeV for n gt 1

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Longitudinal ED

• Simultaneously, another idea has appeared
• Explore modification of the RGE in
  (4n)-dimensions to achieve low-energy
  unification of the gauge forces Dienes, Dudas,
  Gherghetta, PL B436, 55 (1998)
• To achieve that, allow gauge bosons (g, g, W, and
  Z) to propagate in an extra dimension, which is
  longitudinal to the SM brane and compactified
  on a natural EW scale R 1 TeV-1

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Randall-Sundrum Scenario

• Randall-Sundrum (RS) scenario PRL 83, 3370
  (1999) PRL 83, 4690 (1999)
• brane no low energy effects
• branes TeV Kaluza-Klein modes of graviton
• Low energy effects on SM brane are given by Lp
  for krc 10, Lp 1 TeV and the hierarchy
  problem is solved naturally

G
AdS
Planck brane
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Differences Between the Models

• TeV-1 Scenario
• Pro Lowers GUT scale by changing running of the
  couplings
• Only gauge bosons (g/g/W/Z) live in EDs
• Size of EDs 1 TeV-1 or 10-19 m
• Con Gravity is not in the picture

• RS Model
• Pro A rigorous solution to the hierarchy problem
  via localization of gravity
• Gravitons (and possibly other particles)
  propagate in a single ED, w/ special metric
• Con Size of ED as small as 1/MPl or 10-35 m

• ADD Model
• Pro Eliminates the hierarchy problem by
  stating that physics ends at a TeV scale
• Only gravity lives in the bulk space
• Size of EDs (n2-7) between 100 mm and 1 fm
• Black holes at the LHC and in the interactions of
  UHE cosmic rays
• Con Doesnt explain why ED are so large

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Kaluza-Klein Spectrum

• TeV-1 Scenario
• Winding modes with nearly equal energy spacing
  1/r, i.e. TeV
• Can excite individual modes at colliders or look
  for indirect effects

• ADD Model
• Winding modes with energy spacing 1/r, i.e. 1
  meV 100 MeV
• Cant resolve these modes they appear as
  continuous spectrum

• RS Model
• Particle in a box with a special metric
• Energy eigenvalues are given by zeroes of Bessel
  function J1
• Light modes might be accessible at colliders

Gravitational couplingper mode many modes
E
E
E
MGUT
MPl
1 TeV
GN for zero-mode 1/Lp for others

ge

Mi
Mi
M1
M0
M0
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Using the ED Paradigm

• EWSB from extra dimensions
• Hall, Kolda PL B459, 213 (1999) (lifted Higgs
  mass constraints)
• Antoniadis, Benakli, Quiros NP B583, 35 (2000)
  (EWSB from strings in ED)
• Cheng, Dobrescu, Hill NP B589, 249 (2000)
  (strong dynamics from ED)
• Mirabelli, Schmaltz PR D61, 113011 (2000)
  (Yukawa couplings from split left- and
  right-handed fermions in ED)
• Barbieri, Hall, Namura hep-ph/0011311
  (radiative EWSB via t-quark in the bulk)
• Flavor/CP physics from ED
• Arkani-Hamed, Hall, Smith, Weiner PRD 61, 116003
  (2000) (flavor/CP breaking fields on distant
  branes in ED)
• Huang, Li, Wei, Yan hep-ph/0101002
  (CP-violating phases from moduli fields in ED)

• Neutrino masses and oscillations from ED
• Arkani-Hamed, Dimopoulos, Dvali, March-Russell
  hep-ph/9811448 (light Dirac neutrinos from
  right-handed neutrinos in the bulk or light
  Majorana neutrinos from lepton number breaking on
  distant branes)
• Dienes, Dudas, Gherghetta NP B557, 25 (1999)
  (light neutrinos from right-handed neutrinos in
  ED or ED see-saw mechanism)
• Dienes, Sarcevic PL B500, 133 (2001) (neutrino
  oscillations w/o mixing via couplings to bulk
  fields)
• Many other topics from Higgs to dark matter

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ED and Flavor Physics

• ED models offer a powerful paradigm for
  explaining flavor sector and CP-violation
• New amplitudes and phases could be transmitted to
  our world via gravity (or other bulk fields),
  thus naturally introducing small parameters
  needed for description of CP-violation, flavor
  physics, etc.
• Some realizations of this class of models give
  realistic CKM matrix (e.g., Arkani-Hamed, Hall,
  Smith, Weiner PRD 61, 116003 (2000))
• The idea of shining mentioned in the original
  ADD papers could explain why these effects were
  stronger in early universe

shining
bulk
CP-brane
SM
big bang
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Flavor Physics from Geometry

• Arkani-Hamed/Schmaltz Phys. Rev. D61, 033005
  (2000) split fermions embedded in a fat
  brane
• Wave-functions of different families of quarks
  and leptons are spatially offset, thus the
  overlap areas are reduced exponentially
• A fruitful paradigm to build models of flavor and
  mixing with automatically suppressed FCNC and
  stable proton
• Possible to construct realistic CKM matrices via
  geometry of extra brane
• Similar attempts in Randall-Sundrum class of
  models
• In some of these models LFV decays of kaons are
  predicted and could be sought

Huber NP 666, 269 (2003)
Branco/de Gouvea/Rebelo Phys. Lett. B506, 115
(2001)
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Tabletop Gravity Experiments

• Sub-millimeter gravity measurements could probe
  only n2 case only within the ADD model
• The best sensitivity so far have been achieved in
  the U of Washington torsion balance experiment
  a high-tech remake of the 1798 Cavendish
  experiment
• R lt 0.16 mm (MD gt 1.7 TeV)
• Sensitivity vanishes quickly with the distance
  cant push limits further down significantly
• Started restricting ADD with 2 extra dimensions
  cant probe any higher number
• Ultimately push the sensitivity by a factor of
  two in terms of the distance
• No sensitivity to the TeV-1 and RS models

J. Long, J. Price, hep-ph/0303057
E.Adelberger et al.
PRL 86, 1418 (2001)


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Astrophysical and Cosmological Constraints

• Overclosure of the universe, matter dominance in
  the early universe Fairbairn, Phys. Lett. B508,
  335 (2001) Fairbairn, Griffiths, JHEP 0202, 024
  (2002)
• MD gt 86 TeV (n2)
• MD gt 7.4 TeV (n3)
• Neutron star g-emission from radiative decays of
  the gravitons trapped during the supernova
  collapse Hannestad and Raffelt, PRL 88, 071301
  (2002)
• MD gt 1700 TeV (n2)
• MD gt 60 TeV (n3)
• Caveat there are many known (and unknown!)
  uncertainties, so the cosmological bounds are
  reliable only as an order of magnitude estimate
• Still, n2 is largely disfavored

• Supernova cooling due to graviton emission an
  alternative cooling mechanism that would decrease
  the dominant cooling via neutrino emission
• Tightest limits on any additional cooling sources
  come from the measurement of the SN1987A neutrino
  flux by the Kamiokande and IMB
• Application to the ADD scenario Cullen and
  Perelstein, PRL 83, 268 (1999) Hanhart,
  Phillips, Reddy, and Savage, Nucl. Phys. B595,
  335 (2001)
• MD gt 25-30 TeV (n2)
• MD gt 2-4 TeV (n3)
• Distortion of the cosmic diffuse gamma radiation
  (CDG) spectrum due to the GKK ? gg decays Hall
  and Smith, PRD 60, 085008 (1999)
• MD gt 100 TeV (n2)
• MD gt 5 TeV (n3)

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Collider Signatures for Large ED

• Kaluza-Klein gravitons couple to the
  energy-momentum tensor, and therefore contribute
  to most of the SM processes
• For Feynman rules for GKK see
• Han, Lykken, Zhang, PRD 59, 105006 (1999)
• Giudice, Rattazzi, Wells, NP B544, 3 (1999)
• Since graviton can propagate in the bulk, energy
  and momentum are not conserved in the GKK
  emission from the point of view of our 31
  space-time
• Depending on whether the GKK leaves our world or
  remains virtual, the collider signatures include
  single photons/Z/jets with missing ET or
  fermion/vector boson pair production
• Graviton emission direct sensitivity to the
  fundamental Planck scale MD
• Virtual effects sensitive to the ultraviolet
  cutoff MS, expected to be MD (and likely lt MD)
• The two processes are complementary

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LEPilogue (Large ED)
Virtual Graviton Exchange
All limits are in TeV
LEP Combined 1.2/1.1 TeV
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Colliders Graviton Emission

• ee ? g GKK at LEP
• g MET final state
• MP gt 1.4-0.5 TeV (ADLO), for n27
• qq/gg ? q/g GKK at the Tevatron
• jets MET final state
• Z(nn)jets is irreducible background
• Challenging signature due to large instrumental
  backgrounds from jet mismeasurement, cosmics,
  etc.
• DØ pioneered this search and set limits PRL, 90
  251802 (2003) MP gt 1.0-0.6 TeV for n27
• Later, CDF achieved slightly better limits
• Expected reach for Run II/LHC

Theory Giudice, Rattazzi, Wells, Nucl. Phys.
B544, 3 (1999) and corrected version,
hep-ph/9811291 Mirabelli, Perelstein, Peskin,
PRL 82, 2236 (1999)
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Tevatron Virtual Graviton Effects

• Expect an interference with the SM fermion or
  boson pair production
• High-mass, low cosq tail is a characteristic
  signature of LED Cheung, GL, PRD 62 076003
  (2000)
• Best limits on the effective Planck scale come
  from new DØ Run II data
• MPl gt 1.1-1.6 TeV (n2-7)
• Combined with the Run I DØ result
• MPl gt 1.1-1.7 TeV tightest to date
• Sensitivity in Run II and at the LHC

Run II, 200 pb-1
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Interesting Candidate Events

• While the DØ data are consistent with the SM, the
  two highest-mass candidates have anomalously low
  value of cosq typical of ED signal

Event Callas Mee 475 GeV, cosh 0.01
Event Farrar Mgg 436 GeV, cosh 0.03
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TeV-1 Extra Dimensions

• Intermediate-size extra dimensions with ?TeV-1
  radius
• Introduced by Antoniadis PL B246, 377 (1990) in
  the string theory context used by Dienes, Dudas,
  Gherghetta PL B436, 55 (1998) to allow for
  low-energy unification
• Expect ZKK, WKK, gKK resonances at the LHC
  energies
• At lower energies, can study effects of virtual
  exchange of the Kaluza-Klein modes of vector
  bosons
• Current indirect constraints come from precision
  EW measurements 1/r 6 TeV
• No dedicated experimental searches at colliders
  to date

Antoniadis, Benaklis, Quiros PL B460, 176 (1999)
ZKK
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First Dedicated Search for TeV-1 Extra Dimensions

• While the Tevatron sensitivity is inferior to
  indirect limits, it explores the effects of
  virtual KK modes at higher energies, i.e.
  complementary to those in the EW data
• DØ has performed the first dedicated search of
  this kind in the dielectron channel based on 200
  pb-1 of Run II data (ZKK, gKK ? ee-)
• The 2D-technique similar to the search for ADD
  effects in the virtual exchange yields the best
  sensitivity in the DY production Cheung, GL, PRD
  65, 076003 (2002)
• Data agree with the SM predictions, which
  resulted in the following limit
• 1/R gt 1.12 TeV _at_ 95 CL
• R lt 1.75 x 10-19 m

200 pb-1, ee-
Event Callas
Interference effect
1/R 0.8 TeV
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Randall-Sundrum Model Observables

• Need only two parameters to define the model k
  and rc
• Equivalent set of parameters
• The mass of the first KK mode, M1
• Dimensionless coupling

• To avoid fine-tuning and non-perturbative regime,
  coupling cant be too large or too small
• 0.01 0.10 is the expected range
• Gravitons are narrow

Expected Run II sensitivity in DY
Drell-Yan at the LHC
M1
Davoudiasl, Hewett, Rizzo PRD 63, 075004 (2001)
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First Search for RS Gravitons
Already better limits than sensitivity for Run
II, as predicted by phenomenologists!
PRL 95, 091801 (2005)
Assume fixed K-factor of 1.3 for the signal
The tightest limits on RS gravitons to date
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Black Holes on Demand
NYT, 9/11/01
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Theoretical Framework

• Geometrical cross section approximation was
  argued in early follow-up work by Voloshin PL
  B518, 137 (2001) and PL B524, 376 (2002)
• More detailed studies showed that the criticism
  does not hold
• Dimopoulos/Emparan string theory calculations
  PL B526, 393 (2002)
• Eardley/Giddings full GR calculations for
  high-energy collisions with an impact parameter
  PRD 66, 044011 (2002) extends earlier dEath
  and Payne work
• Yoshino/Nambu - further generalization of the
  above work PRD 66, 065004 (2002) PRD 67, 024009
  (2003)
• Hsu path integral approach w/ quantum
  corrections PL B555, 29 (2003)
• Jevicki/Thaler Gibbons-Hawking action used in
  Voloshins paper is incorrect, as the black hole
  is not formed yet! Correct Hamiltonian was
  derived H p(r2 M) ? p(r2 H), which leads
  to a logarithmic, and not a power-law divergence
  in the action integral. Hence, there is no
  exponential suppression PRD 66, 024041 (2002)

• Based on the work done with Dimopoulos a few
  years ago PRL 87, 161602 (2001) and a related
  study by Giddings/Thomas PRD 65, 056010 (2002)
• Extends previous theoretical studies by
  Argyres/Dimopoulos/March-Russell PL B441, 96
  (1998), Banks/Fischler JHEP, 9906, 014 (1999),
  Emparan/Horowitz/Myers PRL 85, 499 (2000) to
  collider phenomenology
• Big surprise BH production is not an exotic
  remote possibility, but the dominant effect!
• Main idea when the c.o.m. energy reaches the
  fundamental Planck scale, a BH is formed cross
  section is given by the black disk approximation

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Assumptions and Approximation

• Fundamental limitation our lack of knowledge of
  quantum gravity effects close to the Planck scale
• Consequently, no attempts for partial improvement
  of the results, e.g.
• Grey body factors
• BH spin, charge, color hair
• Relativistic effects and time-dependence
• The underlying assumptions rely on two simple
  qualitative properties
• The absence of small couplings
• The democratic nature of BH decays
• We expect these features to survive for light BH
• Use semi-classical approach strictly valid only
  for MBH MP only consider MBH gt MP
• Clearly, these are important limitations, but
  there is no way around them without the knowledge
  of QG

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Black Hole Production

• Schwarzschild radius is given by Argyres et al.,
  hep-th/9808138 after Myers/Perry, Ann. Phys. 172
  (1986) 304 it leads to
• Hadron colliders use parton luminosity w/ MRSD-
  PDF (valid up to the VLHC energies)
• Note at c.o.m. energies 1 TeV the dominant
  contribution is from qq interactions

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Black Hole Decay

• Hawking temperature RSTH (n1)/4p (in natural
  units ? c k 1)
• BH radiates mainly on the brane
  Emparan/Horowitz/Myers, hep-th/0003118
• l 2p/TH gt RS hence, the BH is a point
  radiator, producing s-waves, which depends only
  on the radial component
• The decay into a particle on the brane and in the
  bulk is thus the same
• Since there are much more particles on the brane,
  than in the bulk, decay into gravitons is largely
  suppressed
• Democratic couplings to 120 SM d.o.f. yield
  probability of Hawking evaporation into g, l,
  and n 2, 10, and 5 respectively
• Averaging over the BB spectrum gives average
  multiplicity of decay products

• Stefans law t 10-26 s

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Black Hole Factory
Dimopoulos, GL, PRL 87, 161602 (2001)
Black-Hole Factory
n2
n7
gX
Drell-Yan
Spectrum of BH produced at the LHC with
subsequent decay into final states tagged with an
electron or a photon
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Shape of Gravity at the LHC
Dimopoulos, GL, PRL 87, 161602 (2001)

• Relationship between logTH and logMBH allows to
  find the number of ED,
• This result is independent of their shape!
• This approach drastically differs from analyzing
  other collider signatures and would constitute a
  smoking cannon signature for a TeV Planck scale

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Black Hole Events

• First studies already initiated by ATLAS and CMS
• ATLAS CHARYBDIS HERWIG-based generator with more
  elaborated decay model Harris/Richardson/Webber
• CMS TRUENOIR GL

Simulated black hole event in the CMS detector
A. de Roeck S. Wynhoff
Simulated black hole event in the ATLAS detector
from ATLAS-Japan Group
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Conclusions

• Stay tuned next generation of collider
  experiments has a good chance to solve the
  mystery of large extra dimensions!
• If large extra dimensions are realized in nature,
  black hole production at future colliders is
  likely to be the first signature for quantum
  gravity at a TeV
• Many other exciting consequences from effects on
  precision measurements to detailed studies of
  quantum gravity
• If any of these new ideas is correct, we might
  see a true Grand Unification that of particle
  physics, astrophysics and cosmology in just a
  few years from now!