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

Precise signatures depend on fermion wavefunction profiles:

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 it’s heavy IR KK d s tR uL,dL

Definitions:

Definitions

Fermion Model:

Fermion Model

Richer Spectrum…But Lower Production Cross Sectionfor the Graviton:

Richer Spectrum… But Lower Production Cross Section for 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

Graviton Interactions:

Graviton Interactions Volume suppressed

Features of interactions:

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

KK Graviton Production:

KK Graviton Production w/Liam Fitzpatrick,Jared Kaplan, Liantao Wang

Final State? Dominant Decay to right-handed tops:

Final State? Dominant Decay to right-handed tops

Determining top jets: delta R: Angle between decay products:

Determining top jets: delta R: Angle between decay products

Angular dependence: spin determination :

Angular dependence: spin determination

Graviton: some reachOther Bulk Modes?:

Graviton: some reach Other Bulk Modes?

Gluon KK Mode:

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

Slide16:

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.

Slide17:

Gluon wave function

Gluon fermion interaction:

Gluon fermion interaction

Dominates over top jet background:

Dominates over top jet background w/Ben Lillie, Liantao Wang

However, signal doesn’t dominate over jet background:

However, signal doesn’t dominate over jet background

Clearly…:

Clearly… Efficient top jet identification required, especially for heavier KK gluons
Usual method: relies on separated decay products
Won’t be true for energetic tops
How to identify energetic tops?:
Top jet mass measurement
Detailed substructure of jets: eg hard lepton

Summary So Far:

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

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

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 M~TeV=>~100 pb cross section
Not suppressed by gauge couplings or phase space factors Original claims:
Prolific Production!
Spectacular fireball final states!

Recent Work:

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
However…all 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

Why Change in Expectations?:

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

Criteria for a Black Hole?:

Criteria for a Black Hole? MBH>M
As advertised, not even convention independent
2p/(M/2)<RS
More stringent version of above
ADD (n=6) MBH>4M—almost at experimental limit
RS MBH>16M—if taken seriously, bhs already out of reach
Additional thermality/entropy constraints support these high mass threshold claims

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

What is true threshold energy?: Inelasticity as function of impact parameter What fraction of com energy goes into black hole
Important since PDFs fall rapidly—effectively increases threshold
Penrose, D’eath 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

w/ and w/o inelasticity; Impact parameter weighted:

w/ and w/o inelasticity; Impact parameter weighted

Upshot:

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
Don’t produce classical thermal black holes
What do we produce?
2 body final states!

Compositeness Searches for Quantum Gravity :

Compositeness Searches for Quantum Gravity Measure differential cross section
Measure angular dependence through Rh (much less systematic error)
Indicator of strong dynamics

Clarification:

Clarification We don’t 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

Eg: Result Model I: Dijet “Black Holes”:

Eg: Result Model I: Dijet “Black Holes”

Lepton cross section might be key:

Lepton cross section might be key Four-fermion operators: large lepton suppression
Pdf, alpha, u/s TeVADD:MD=1

From Black Holes:

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

Summary:

Summary Black holes not as “spectacular” as advertised
BUT
Lots of information about quantum gravity buried in 2->2!
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

Conclusion:

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 we’ll know in a few years!

You do not have the permission to view this presentation. In order to view it, please
contact the author of the presentation.

Send to Blogs and Networks

Processing ....

Premium member

Use HTTPs

HTTPS (Hypertext Transfer Protocol Secure) is a protocol used by Web servers to transfer and display Web content securely. Most web browsers block content or generate a “mixed content” warning when users access web pages via HTTPS that contain embedded content loaded via HTTP. To prevent users from facing this, Use HTTPS option.