Low scale gravity signatures in ATLAS

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Low scale gravity signatures in ATLAS
Müge Karagöz Ünel on behalf of the ATLAS
Collaboration ICPP, Bogazici Univ.,
Istanbul October 27-31, 2008
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A motivation The Unbearable Lightness of Being
Gravity is weak, governed by Planck scale
(MPl1019 GeV) How to unify forces solve the
hierarchy problem (MPl gtgtMEW)?
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Extra Dimensions Not a Flatland

• In 1920s KaluzaKlein unify electromagnetism
  with gravity
• In late 1990s, models built to solve the
  hierarchy problem
• We observe apparent gravity, actual gravity is
  stronger and its scale can be as low as TeV
• Many ED models flat (ADD, TeV-1), warped (RS),
  various particles escaping into bulk while SM
  is confined to our 3-brane

1/r2-law valid for R44 µm _at_ 95 CL
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Gravity in ATLAS

• Analyses being optimised for efficient
  observation of TeV-scale gravity effects in ATLAS
• New particle production depending on the model
• A set of particles have higher order modes
  Kaluza-Klein towers
• Mass seperation between these towers are model
  dependent
• Can be searched for search directly
• Here, 3 signatures in 3 different models with
  increasing signature complexity are presented
  (published only)
• Exclusive resonance searches
• Randal-Sundrum Gravitons in dielectron channel
  (CERN-OPEN-2008-020 )
• TeV-1 gluon in heavy quarks (ATL-PHYS-PUB-2006-002
  )
• Inclusive searches
• ADD Black hole production (CERN-OPEN-2008-020 )

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LHC may easily confirm/refute ED

• Most stringent limits to date from Tevatron on
  RS
• CDF k/MPl 0.1, mG gt 889 GeV (gg ee, 1 fb-1),
  850 GeV (ee, 2.5 fb-1)
• D0 k/MPl 0.1, mG gt 900 GeV (diEM,1 fb-1,
  PRL100/091802/08)

Other limits from Tevatron are in backup
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RS KK Graviton Resonance Search in Dielectrons

• Narrow resonances predicted by the highly-warped
  geometry of RS ED at TeV-scales.
• Graviton production and width depends on the
  ratio of the warp factor (k) to reduced MPl
• ATLAS searched for RS1-type (PRL83/3370/99)
  resonances with no interference with SM bosons.
• Cross-section varies from 200 fb - 20 fb for
  0.5-1.4 TeV Graviton. A k-factor multiplies the
  LO cross-section

• Select 2 back-to-back electrons pT gt 65 GeV, with
  no charge requirement
• loose cuts to increase high pT efficiency Eff
  66-54, 0.5-1.4 TeV
• Main background is irreducible Drell-Yan.
• Effect of systematics on discovery is 10-15
  (model parameter dependent)

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RS KK Graviton Reach in Dielectrons

• Use extended maximum likelihood fitting for
  discovery potential using pseudo-experiments

Graviton with M900 GeV can be discovered for
k/MPl 0.01
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Excited KK Gluon Searches in QQbar

• KK g predicted by models allowing bulk Gauge
  bosons
• TEV-1 EDs (PRD65/076007/08)
• Produced from quarks and decay via quarks
  (canonical dijet signatures studied earlier by
  Balazs et al_at_Les Houches 2003
• Interesting signature at ATLAS via heavy quark
  pairs bb, tt

• Fast simulation used
• Main backgrounds bb and tt (irreducible), for bb
  also reducible jj. Wj also considered.
• High pt b-tag values (0.1 for 1 TeV g) used w/o
  optimization
• A leptonic and a hadronic top reconstruction is
  used for ttbar

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KK Gluon Reach in QQbar

• bbbar can be used as evidence as uncertainties in
  the background calculations are large
• Ttbar can be used as discovery with efficient
  reconstruction in 3 years running

300 fb-1 allows a 5s reach up to 3.3 TeV for ttbar
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Those m-Blackholes

• A beautiful theory that combines thermodynamics,
  QFT and gravity
• Can be roduced when vsgt MPl
• s pRS2 1 TeV-2 10-38 m2 O(100)pb
• MBH v(sx(q1)x(q2))
• Lifetime 10-27 10-25 seconds!
• Decays to all particles via Hawking Radiation
• LHC ? Black Hole Factory!

N. Brett
RS2q 10-50 m
Collide 2 partons (bring their mass together)
with impact parameter lt Schwarzschild radius Rs,
and form a black hole!
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m-Blackhole Production at ATLAS

• Dedicated event generators
• difficult modelling, theory uncertainties
  dominate
• need semi-classical approx., well above Planck
  scale needed and minimum BH mass must be imposed.
• CHARYBDIS (JHEP08/033/03) event generator used
  for publication

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m-Blackhole Detection at ATLAS

• Distinguishing features
• High Multiplicity (gt10 energetic particles in
  event), high total energy of events..
• Background tail can extend to BH signal region.
• Main backgrounds ttbarjets, QCD and Wjets
• Inclusive selection, robust over nED and theory
  uncertainty (nED ??, nPart ??, EPart ?)
• 2 complementary selection methods
• Inclusive
• SpT gt2.5 TeV
• One lepton pT gt 50 GeV
• Signal acceptance
• 0.46-0.17, n2-7
• Exclusive
• 4 particles pT gt 200 GeV
• One lepton pT gt 200 GeV

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Discovery Reach for BH _at_ ATLAS
Method 1
For Sgt10 and S/sqrt(B) gt 5 MBHgt5 TeV with 1
pb-1 data MBHgt8 TeV takes 1 fb-1 data
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Current and Future Directions

• ATLAS has a very rich discovery potential for
  predicted TeV-Scale gravitational effects. Work
  is ongoing on many fronts.
• BH specific news
• String balls, highly excited string states (in
  Charybdis)
• Low-mult, dijet-like BH events viable at LHC
  (Meade and Randall, JHEP05(2008)003) (alas, lower
  cross sections) (In BlackMax)
• ED in heavy and boosted objects
• Exploit the novel techniques to efficiently
  reconstruct heavily-boosted t and b quarks
• RS KK gluons (JHEP 0709074 (2007)
• Already ruled out from Tevatron results up to 800
  GeV/c2 (hep/ph/0703060)
• Cross section calculations and simulation
  productions of 10TeV samples are ongoing in
  preparation for 2009.

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No Blackholes yet Watch this space!
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BACKUP
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Forces of the Universe, Unite!
If we can study particles and interactions at the
beginning of the universe, we may solve the
equation to the laws governing the universe!
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Comparison of Production Rates
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Monopoly Game
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Tencerenin dogurduguna...
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Convincing the public about LHC
I have never won the national lottery, so go for
it! anony, on BH threat!
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The LHC is safe, John Ellis (CERN)
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ATLAS Detector Specifics
A toroidal LHC apparatus

• Inner Tracking (?lt2.5, 2T solenoid)
• Silicon pixels and strips
• Transition Radiation Detector (e/? separation)
• Calorimetry (?lt5)
• EM Pb-LAr, Accordion shape
• HAD Fe/scintillator (central), Cu/W-LAr (fwd)
• Muon Spectrometer (?lt2.7, 4T toroid)
• air-core toroids with muon chambers

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BH at 10 TeV (D. Gingrich)
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Other limits from Tevatron

• Large Extra Dimensions via Single Photon plus
  Missing Energy Final States
• Current Best D0 At 95 C.L., limits on the
  fundamental mass scale MD from 970 GeV to 816 GeV
  for 2-8 ED

• CDF Limits on ttbar resonances (PRD77/051102/08)
• Also limits on massive gluon coupling in 1.9
  invpb data (CDF note 9164)

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Limits from Others (based on G. Landsberg)

• Table top Sub-millimeter gravity measurements
  could probe only n2 case only within the ADD
  model
• U of Washington torsion balance experiment a
  remake of the 1798 Cavendish experiment
• R lt 0.16 mm (MD gt 1.7 TeV)
• Supernova cooling due to graviton emission
• 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)
• 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)
• Astrophysical and cosmological limits are the
  most stringent
• n2 is largely disfavored

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Time Evolution of Black Holes
2. Balding phase Class. emission of gravitional
waves
1. Horizon formation
Kerr BH
3. Evaporation phase Hawking radiation Superradian
ce
4. Planck phase ????? Pick what you like
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Distinguishing BH

• Different characteristics than SUSY or SM