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Low scale gravity signatures in ATLAS

Low scale gravity signatures in ATLAS. M ü ge Karag ö z Ü nel on behalf of the ATLAS Collaboration ICPP, Bogazici Univ., Istanbul October 27-31, 2008. 25. 1. 10 -41. 0.8. A motivation: The Unbearable Lightness of Being. Gravity is weak, governed by Planck scale (M Pl =10 19 GeV)

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Low scale gravity signatures in ATLAS

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  1. Low scale gravity signatures in ATLAS Müge Karagöz Ünel on behalf of the ATLAS Collaboration ICPP, Bogazici Univ., Istanbul October 27-31,2008

  2. 25 1 10-41 0.8 A motivation: The Unbearable Lightness of Being Gravity is weak, governed by Planck scale (MPl=1019 GeV) How to unify forces & solve the hierarchy problem (MPl >>MEW)?

  3. MPl ~ 1019 GeV, MPl(4+n)~MEW Obtain size of the ED from gravitational potential Extra Dimensions: Not a Flatland • In 1920’s Kaluza&Klein unify electromagnetism with gravity • In late 1990’s, 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 R=44 μm @ 95% CL

  4. 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 )

  5. LHC may easily confirm/refute ED • Most stringent limits to date from Tevatron on RS: • CDF : k/MPl= 0.1, mG > 889 GeV (gg +ee, ~1 fb-1), 850 GeV (ee, 2.5 fb-1) • D0 : k/MPl = 0.1, mG > 900 GeV (diEM,1 fb-1, PRL100/091802/08) Other limits from Tevatron are in backup

  6. 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 > 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) RS KK Graviton Resonance Search in Dielectrons

  7. RS KK Graviton Reach in Dielectrons • Use extended maximum likelihood fitting for discovery potential using pseudo-experiments Graviton with M=900 GeV can be discovered for k/MPl = 0.01

  8. 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@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. W+j 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 Mg* = 1TeV, s= 1100 pb Excited KK Gluon Searches in QQbar

  9. 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 5σ reach up to 3.3 TeV for ttbar

  10. Formation quark Rs quark Those m-Blackholes • A beautiful theory that combines thermodynamics, QFT and gravity • Can be roduced when √s> MPl • σ ~ πRS2 ~ 1 TeV-2 ~ 10-38 m2 ~ O(100)pb • MBH = √(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 < Schwarzschild radius Rs, and form a black hole!

  11. 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 Webber et al, 2005 m-Blackhole Production at ATLAS

  12. m-Blackhole Detection at ATLAS • Distinguishing features • High Multiplicity (>10 energetic particles in event), high total energy of events.. • Background tail can extend to BH signal region. • Main backgrounds: ttbar+jets, QCD and W+jets • Inclusive selection, robust over nED and theory uncertainty (nED , nPart , EPart ) • 2 complementary selection methods • Inclusive • Σ|pT|>2.5 TeV • One lepton pT > 50 GeV • Signal acceptance: 0.46-0.17, n=2-7 • Exclusive • 4 particles pT > 200 GeV • One lepton pT > 200 GeV

  13. Discovery Reach for BH @ ATLAS Method 1 For S>10 and S/sqrt(B) > 5: MBH>5 TeV with 1+ pb-1 data MBH>8 TeV takes 1 fb-1 data

  14. 3-body monojet 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 0709:074 (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.

  15. No Blackholes yet… Watch this space!

  16. BACKUP

  17. Supersymmetry String theory Extra Dimensions 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!

  18. Comparison of Production Rates

  19. Rediscovery background SUSY Higgs Heavy exotics Monopoly Game

  20. “Tencerenin dogurduguna...”

  21. Convincing the public about LHC “I have never won the national lottery, so go for it!” – anony, on BH threat!

  22. “The LHC is safe”, John Ellis (CERN)

  23. 22 m 44 m ATLAS Detector Specifics A toroidal LHC apparatus • Inner Tracking(||<2.5, 2T solenoid) : • Silicon pixels and strips • Transition Radiation Detector (e/ separation) • Calorimetry (||<5) : • EM : Pb-LAr, Accordion shape • HAD: Fe/scintillator (central), Cu/W-LAr (fwd) • Muon Spectrometer (||<2.7, 4T toroid) : • air-core toroids with muon chambers

  24. Split Fermion Brane Extra Dimensionshep-ph/0605085, 0505112, 0606321, 0612018;gr-qc/0604072 BH don’t conserve B or L or flavour • induced proton decay! • n – nbar oscillations! • Flavour changing neutron currents or large neutrino mixing mini bulk gauging B, L, F OR SPLIT leptons quarks extra dimension BH at the LHC will decay mainly into quarks and gluons! 15/10/08 C. Issever, University of Oxford 24

  25. BH at 10 TeV (D. Gingrich)

  26. 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) Other limits from Tevatron

  27. Limits from Others (based on G. Landsberg) • Table top: Sub-millimeter gravity measurements could probe only n=2 case only within the ADD model • U of Washington torsion balance experiment – a “remake” of the 1798 Cavendish experiment • R < 0.16 mm (MD > 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 > 25-30 TeV (n=2) • MD > 2-4 TeV (n=3) • Distortion of the cosmic diffuse gamma radiation (CDG) spectrum due to the GKK gg decays [Hall and Smith, PRD 60, 085008 (1999)]: • MD > 100 TeV (n=2) • MD > 5 TeV (n=3) • Overclosure of the universe, matter dominance in the early universe [Fairbairn, Phys. Lett. B508, 335 (2001); Fairbairn, Griffiths, JHEP 0202, 024 (2002)] • MD > 86 TeV (n=2) • MD > 7.4 TeV (n=3) • Neutron star g-emission from radiative decays of the gravitons trapped during the supernova collapse [Hannestad and Raffelt, PRL 88, 071301 (2002)]: • MD > 1700 TeV (n=2) • MD > 60 TeV (n=3) • Astrophysical and cosmological limits are the most stringent • n=2 is largely disfavored • Many known (and unknown!) uncertainties, bounds are reliable only as an order of magnitude estimate

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

  29. Distinguishing BH • Different characteristics than SUSY or SM

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