Warped Passages

1
Warped Geometry
More
Consequences and Signatures
Lisa Randall, Harvard University
2
Phenomenology?

• Bulk gauge bosons
• Means KK modes of
• Weak bosons
• Gluons
• Fermions
• As well as gravitons

3
Precise signatures depend on fermion wavefunction
profiles

• Nontrivial profiles help solve flavor problem
• Masses depend on overlap with Higgs
• Expect light fermions localized near
  Planck/Gravity brane
• Top near Weakbrane since its heavy

KK
d
s
Higgs Boson
IR
uL,dL
tR
4
Definitions
5
Fermion Model
6
Richer SpectrumBut Lower Production Cross
Sectionfor the Graviton

• Light quarks are localized away from Higgs
• Hence away from TeV brane
• No Drell-Yan production from quarks
• Gluons are spread throughout the bulk
• Hence coupling to graviton down

7
Graviton Interactions
Volume suppressed
8
Features of interactions

• The suppression by M4L is a factor of 1/N from
  the dual gauge theory perspective
• 1/mTeV is local cutoff
• p k rc because gluon has flat wave function
  volume factor
• Fermion behavior

9
KK Graviton Production
w/Liam Fitzpatrick,Jared Kaplan, Liantao Wang
10
Final State? Dominant Decay to right-handed tops
11
Determining top jets delta R Angle between
decay products
12
(No Transcript)
13
Angular dependence spin determination
14
Graviton some reachOther Bulk Modes?
15
Gluon KK Mode

• Gluon KK mode coupling to light quarks is less
  suppressed than graviton
• Gluon KK mode wave function relatively flat in
  bulk
• Benefit from light quark coupling
• not as for gluon
• No 1/ML,
• Gluon KK mode lighter by factor 1.5
• Larger reach for gluon KK mode

16
Understand from dual point of view in terms of
gluon KK mixing-vector meson dominance
Note only gluon production from quarks. At tree
level, gluon coupling vanishes.
17
Gluon wave function
18
Gluon fermion interaction
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(No Transcript)
20
Dominates over top jet background
w/Ben Lillie, Liantao Wang
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However, signal doesnt dominate over jet
background
22
Clearly

• Efficient top jet identification required,
  especially for heavier KK gluons
• Usual method relies on separated decay products
• Wont be true for energetic tops
• How to identify energetic tops?
• Top jet mass measurement
• Detailed substructure of jets eg hard lepton

23
Summary So Far

• If RS1 solves the hierarchy problem, we should be
  able to tell
• Clean KK graviton signal if SM on brane
• Best signature spin-2 resonance and mass gap
• In bulk, gluon KK mode will be important
• Decays into tops critical
• Challenge is to maximize energy reach
• Critical for many possibilities for electroweak
  sector
• Models give insights into what to look for
• End of Part II

24
Part III Quantum Gravity at the LHC Other
Exotics? Black Holes?

• Estimate black hole production cross section
  claim just need 2 energetic beams within RS

MTeVgt100 pb cross section Not suppressed by
gauge couplings or phase space factors
Original claims Prolific Production! Spectacular
fireball final states!
25
Recent Work

• How much could we really hope to learn from black
  holes?
• Do we even produce them?
• We will see
• LHC unlikely to make classical black holes states
  that decay with high multiplicity via Hawking
  radiation
• Howeverall is not lost
• Potentially much more prolifically produced 2
  body final states
• Uncalculable, but we will see distinctive
  experimental signatures that will distinguish
  among modes
• Might teach us about quantum gravity

26
Why Change in Expectations?

• Estimate was always optimistic
• Understanding uncertainties and making
  refinements essential
• PDFs drop rapidly and
• We are necessarily near black hole production
  threshold
• Every term in original estimate must be
  considered carefully
• M quantum gravity scale
• MBH black hole mass relative to center of mass
  energy

27
Criteria for a Black Hole?

• MBHgtM
• As advertised, not even convention independent
• 2p/(M/2)ltRS
• More stringent version of above
• ADD (n6) MBHgt4Malmost at experimental limit
• RS MBHgt16Mif taken seriously, bhs already out of
  reach
• Additional thermality/entropy constraints support
  these high mass threshold claims

28
What is true threshold energy? Inelasticity as
function of impact parameter

• What fraction of com energy goes into black hole
• Important since PDFs fall rapidlyeffectively
  increases threshold
• Penrose, Death and Payne, Eardley and Giddings,
  Yoshino and Rychkov
• Parameterize two Aichelberg-Sexl shock waves (two
  highly boosted particles) intersecting
• What fraction of energy gets trapped behind
  horizon?
• Of course applies in classical regime but we use
  to estimate

29
w/ and w/o inelasticity Impact parameter
weighted
30
Upshot

• Black hole production threshold (MBH) higher
  than originally thought
• Means
• Lower production cross section
• Lower reach in black hole mass
• Translates into lower entropy reach as well
• Dont produce classical thermal black holes
• What do we produce?
• 2 body final states!

31
Compositeness Searches for Quantum Gravity

• Measure differential cross section
• Measure angular dependence through Rh (much less
  systematic error)
• Indicator of strong dynamics

32
Clarification

• We dont really think we can make precise
  predictions
• We use models for quantum gravity
• To see what to look for
• Take advantage of potentially rich data
• Ask what are distinguishing features that
• Experimentally probe quantum gravity
• Also note we forbid global quantum number
  violating transitions so we focus on B-conserving
  jets and lepton-number conserving processes

33
Eg Result Model I Dijet Black Holes
34
Lepton cross section might be key

• Four-fermion operators large lepton suppression
• Pdf, alpha, u/s

TeVADDMD1
35
From Black Holes
Much higher cross section since large fraction
with larger pdfs Even just losing u/s, alpha
36
Summary

• Black holes not as spectacular as advertised
• BUT
• Lots of information about quantum gravity buried
  in 2-gt2!
• Initial increase in rate for more central
  processes always occurs
• Could be related to fundamental partons in black
  holes?
• R behavior bh, string resonances, different
  forms for string, Z all distinctive
• Threshold behavior where interference matters
• Hadron vs. Lepton cross section

37
Conclusion

• Physics at a few TeV could be spectacular
• Might be relatively low end
• But need to modify strategies to have best
  capacity for high energy
• Tops, compositeness searches can be key
• We could be lucky-low energy clean signals
• But in any case there should be something there
• Hopefully well know in a few years!