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Road to Discovery: Lecture 2

Road to Discovery: Lecture 2. Sarah Eno U. Maryland. New Physics. Many models for new physics Many predict similar signatures Let’s do a quick survey of fashionable new models and then talk about the challenges that come from different signatures Higgs? SUSY? Extra dimensions?

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Road to Discovery: Lecture 2

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  1. Road to Discovery: Lecture 2 Sarah Eno U. Maryland eno, Road to Discovery, L2

  2. New Physics • Many models for new physics • Many predict similar signatures • Let’s do a quick survey of fashionable new models and then talk about the challenges that come from different signatures • Higgs? • SUSY? • Extra dimensions? • Little higgs? • New strong dynamics? • Compositeness? eno, Road to Discovery, L2

  3. General Observations • only SM Higgs has a well-defined signal (like top, single top, etc) • Want big cross section and clean signature (final state with high pT leptons or other dramatic signature) • The earliest results may come from something that couples to gluons eno, Road to Discovery, L2

  4. WHAT IS IT? • EXCESS IN LEPTON+MET+JETS • understanding of top production properties needs work? • understanding of W plus jets properties needs work? • susy? • beta.ne.1 LQ? • b’? • Need the whole view of the elephant to disentangle Nature.com While challenging, will try to emphasize signatures as much as possible. It would be depressing to put a large amount of effort excluding SUSY LM1 when there is a beta=0.5 LQ in the data. Nevertheless, it is useful to study specific models. Kind of like the silly but necessary “problems” you solve while you are still doing course work. eno, Road to Discovery, L2

  5. Higgs in 1 slide • standard model requires a scalar particle with mass in the terascaleregion that couples to mass -> diboson final states • (almost) guaranteed to be there (caveat: see, for example, technicolor) • doesn’t couple directly to gluons and take a hit in boson branching fractions to leptons. Tough luck! Signature: Mostly di-boson events (for more signatures, lecture 3) eno, Road to Discovery, L2

  6. SUSY in 1 Slide What spin is a saraheno? Signature: X+MET (X usually has jets) • a boson for every fermion, a fermion for every boson • we don’t know the mechanism that breaks susy -> creative theorists can produce almost any signature from SUSY. • rare decay searches (proton decays, b->sgamma, fcnc, lepton family number violation, precision EWK, etc) do give us some hard constraints • easiest way around is r-parity and degenerate masses for the 1st and 2nd generation sfermions. R-parity conveniently also gives a dark matter candidate. Degeneracy gives boost to cross section. • with these, still have a wide variety of signatures(strongly depends on mass hierarchy and splittings) but generally contain MET • squarks/gluinos couple to gluon, so could be an early discovery? eno, Road to Discovery, L2

  7. Extra Dimensions in a few slides Original motivation: Solve the problem of why the planck scale and the electroweak scale are so different. We know the Planck scale comes from looking at Newton’s Law If there were more than 3 spatial dimension), especially some rolled up ones too small for us to see (and only gravity operated in the extra ones) , this would become “ADD” “large extra dimensions” Adjust R and n so that M* can be the EWK scale (1 TeV) 1mm n=2 eno, Road to Discovery, L2

  8. ADD Particles in the wrapped-up extra dimensions act like particle in box from undergrad QM. Massless ground state is the standard 4d graviton : tower of (massive) states. Sum of the tower of gravitons with effective coupling (1/M*2) give reasonable bremsstrahlung cross section. Signature: mono-X (X=jets, photons, etc), blackholes eno, Road to Discovery, L2

  9. TeV sized extra dimensions TeV-1 size ED. (1 TeV=2x10-19m) Allow other particles to propagate in these (small) extra dimensions. Get KK tower of states. Dimension of nis number of extra dimensions (d). From precision EWK, for d=5, Rc-1>4TeV Signature: high mass copies of SM gauge bosons, like Zprimes. If all particles can propagate in the extra dimensions (requires k-parity), get UED. If other SM particles propogate in the ED, can get HSCP eno, Road to Discovery, L2

  10. Extra dimensions in 3 slides Signature: towers of spin 2 resonance that decays to di-fermions and di-bosons (zprime-like, but also γγ decay) mass splittings of O(TeV) and variable width eno, Road to Discovery, L2

  11. Compositeness in 1 slide Discovery that proton is a composite object Phys. Rev. Lett 23,930 (1969) eno, Road to Discovery, L2

  12. Potpourri in 1 slide • Many other well-motivated theories • left-right symmetric models (neutrino mass) -> Wprimes, Zprimes, massive neutrinos • Hidden Valley • unification eno, Road to Discovery, L2

  13. Discovery 300 pb at 14 TeV • What can we discover? • if it has no background and 100% e*A, need at least 5 events: 15 fbxsct • typical 10-80% acceptance 20-150 fb • above Tevatron reach -> gg initial state with M>100 or qq state with M>600 GeV • Examples of things with “no” backgrounds • heavy stable charged particles (HSCP) • blackholes • Zprime to ee, mumu eno, Road to Discovery, L2

  14. Bumps Discovery of the Z Bump hunting is one of the easiest kinds of searches to do. Low background bump hunting is even easier. They provide fool-proof discovery Or do they? pentaquark eno, Road to Discovery, L2

  15. Heavy Bosons to ee, μμ Predicted in many theories: TeV-1 ED, RS ED, little higgs, L-R symmetric, etc. Main background is DY production. Smoothly and quickly falling with mass. eno, Road to Discovery, L2

  16. Heavy Boson • To get the best result, take a little care • resolution, bias for tracks (muons) sensitive to alignments • high energy muonsbrem • hard to check efficiencies/resolutions/scale from data at high energy • calorimeter could saturate at the highest energy • calorimeter isolation, had/em cut could lose efficiency at high energy • Might not cause you to miss signal, but might not get as high a significance as you like (would be bad if the experiment across the ring got a higher significance) eno, Road to Discovery, L2

  17. Cross sections M=1000 GeV sigma=.23 pb acc*eff=0.67 N=46 M=1250 GeV sigma= 0.083 pb acc*eff=0.68 N=17 M = 1500 GeV sigma = 0.033 pb acc*eff=0.69 N=7 10 TeV eno, Road to Discovery, L2

  18. Alignment Alignment effect (startup conditions 100 pb-1)‏ Mass resolution: 7-8 (10) % at 1 (2) TeV Statistical significance related to sharpness of peak related to resolution Loss of signal efficiency due to charge mis-ID: Ideal: 0.98 300 mm: 0.97 1000 mm: 0.88 3 eno, Road to Discovery, L2

  19. Mee (GeV) electron Pt (GeV) A specific Analysis ATLAS Phys TDR CMS PAS EXO-08-004 Example: selection for Z’ ee: - 2 electrons in |η| < 2.5, pt> 30 GeV - electron ID (cluster-track matching)‏ - e isolated in tracker/ECAL/HCAL CMS PAS EXO-08-001 CMS BSM 07-002 CMS: after selection High pt electron reconstruction Efficiencies relative to acceptance: Main backgrounds: Drell-Yan (irreducible)‏ ttbar, W+jets, QCD (reducible)‏ Tevatron limit is: 700-1000 GeV

  20. Z’ ee CMS: Data Driven methods for ttbar background estimation b-tagging method: Ntt can be extracted from N(1b tag)or N(2b tag) + e(b) From n2/n1 + geom acceptance for one or two b-quarkscan extract e(b) (0.20± 0.09)‏ e-m method: Usee-mevents from the 2 W decays ttbare-m = 2* ttbaree For 100 pb-1: expect 16.1 ttbarbg determined by expected sample of 42.5 e-mevents

  21. Mee(GeV) L (pb-1) Z’ ee and Z’ mm Discovery potential for Z’ mm Discovery potential for Z’ ee CMS Z' (Y)‏ Z' (Y)‏ Z' (SSM)‏ Z' (SSM)‏

  22. L (fb-1) M(G) (GeV) G coupling M(rT and wT) (GeV) M(G) (GeV) Gravitons and Technicolor mesons Discovery potential for RS Gravitons: Discovery potential for Strawman model Technicolor mesons: c=0.01 c=0.1 Stat +syst Stat only CMS G mm

  23. Other high mass, low background resonances Can also look for other kinds of high mass resonances, some more, some less motivated. eq, eν, eγ, eμ, … (etc etc etc) eno, Road to Discovery, L2

  24. wprime Very similar to Zprime search. Backgrounds continuum W production and W’s from ttbar production. eno, Road to Discovery, L2

  25. lepton and jet CMS PAS EXO-08-006 ATLAS Phys TDR Look for topologies with 2 same flavour leptons and at least 2 jets, and no missing Et Two models investigated: 1) Leptoquark pair production 2) Heavy WR and heavy neutrino production M(jl) = M(LQ) MN=M(j1j2 l2), M(WR)=m(j1j2l1l2) 2 resonance structure Main background: Drell-Yan and ttbar production

  26. ST(GeV) M(LQ) (GeV) M(lj) (GeV) M(lj) (GeV) Leptoquark pair production search ATLAS Phys TDR Oppositely charged leptons of same flavour and at least two jets Example: selection for the first generation LQ: - e1,e2 with |η| < 2.5, Pt<20 GeV, electron ID, - two jets (DR=0.4 cone algo), |η| <4.5, Pt<20 GeV - DR(e-j)< 0.1 All plots for L=100 pb-1 Mjl=M(LQ) choose combination such M1 closest to M2 + M(ee)>120 GeV + S > 490 GeV

  27. Dijet searches • All though cross section is strong, can still be challenging due to • large SM background • poor jet energy resolution (compared to e,mu resolutions) and eta-dependent JES that can further degrade resolution until it is understood and removed. • tails on resolution due to FSR • How can we make this more robust and do it with early data? eno, Road to Discovery, L2

  28. Dijet Mass Resolution Example: CMS • Resolution for corrected CaloJets • 9% at 0.7 TeV • 4.5% at 5 TeV • Tails due to FSR (gluon) 2 TeV Z’ |η| < 1.3 Resolution Corrected CaloJets GenJets Natural Width eno, Road to Discovery, L2

  29. Dijet Resonances in Rate vs. Dijet Mass • Measure rate vs. corrected dijet mass and look for resonances. • Use a smooth parameterized fit or QCD prediction to model background • Strongly produced resonances can be seen • Convincing signal for a 2 TeV excited quark in 100 pb-1 • Tevatron excluded up to 0.78 TeV. Spectrum falling quickly enough that will not really see bump (remember Z to bbbar) QCD Backgound Resonances with 100 pb-1 eno, Road to Discovery, L2

  30. Dijet Resonances with Dijet Ratio • All resonances have a more isotropic decay angular distribution than QCD • Spin ½ (q*), spin 1 (Z’), and spin 2 (RS Graviton) all flatter than QCD in dN / dcosq*. • Dijet ratio is larger for resonances than for QCD. • Because numerator mainly low cos q*, denominator mainly high cos q* Dijet Angular Distributions Dijet Ratio vs Mass QCD eno, Road to Discovery, L2

  31. Dijet Resonances with Dijet Ratio • Dijet ratio from signal + QCD compared to statistical errors for QCD alone • Resonances normalized with q* cross section for |h|<1.3 to see effect of spin. • Convincing signal for 2 TeV strong resonance in 100 pb-1 regardless of spin. • Promising technique for discovery, confirmation, and eventually spin measurement. Dijet Ratio for Spin ½, 1, 2 Dijet Ratio for q* eno, Road to Discovery, L2

  32. Contact Interaction eno, Road to Discovery, L2

  33. Inclusive Jet PT and Contact Interactions • Contact interactions create large rate at high PT and immediate discovery possible • Error dominated by jet energy scale (~10%) in early running (10 pb-1) • DE~ 10% not as big an effect as L+= 3 TeV for PT>1 TeV. • PDF “errors” and statistical errors (10 pb-1) smaller than E scale error • With 10 pb-1 we can see new physics beyond Tevatron exclusion of L+ < 2.7 TeV. Rate of QCD and Contact Interactions Sensitivity with 10 pb-1 Sys Err. PDF Err. eno, Road to Discovery, L2

  34. Way out on the tails Once Voyager got out there, that Neptune had rings was very clear.

  35. Heavy stable charged particles eno, Road to Discovery, L2

  36. Small beta Thesis: Andrea Rizzi Beta =1 : arrive at CMS muon chambers at t=13 ns Beta = 0.3: arrives at CMS muon chambers at t=38 ns (25 ns later) eno, Road to Discovery, L2

  37. HSCP CMS eno, Road to Discovery, L2

  38. HSCP eno, Road to Discovery, L2

  39. HSCP eno, Road to Discovery, L2

  40. Stopped r-hadrons Stopped muons from the ICARUS T600 module (http://arxiv.org/abs/hep-ex/0309023) Muon ranges out in calorimeter, then decays to an electron (plus neutrinos) Hadronizedgluino ranged out and then decays to Jet(s) (+MET) eno, Road to Discovery, L2

  41. Long-lived neutrinos to jet(s)(+MET) Look for odd shaped jets when there is no beam in the detector eno, Road to Discovery, L2

  42. eno, Road to Discovery, L2

  43. Long-lived gluinos eno, Road to Discovery, L2

  44. Sensitivity 300 GeVgluino and 100 GeVneutralino eno, Road to Discovery, L2

  45. Black holes From background-free due to simplicity to background free due to complexity.

  46. Extra Dimensions and Black Holes The Planck scale is the one at which gravitation interactions become large. If gravity becomes strong at the TeV scale, the results could be quite exciting. If there are extra dimensions, the formula for the Schwarzschild radius becomes Cross section could be large at current limits on M*, n (see 0809.2571, 0709.1107,0802.2218), 1 -1800 fb. Quickly evaporate by emitting all types of particles democratically. 0802.2218 15 fb for background-free eno, Road to Discovery, L2

  47. The big Picture:Heisenberg-‘t Hooft Stolen from: Seong Chan Park (SNU) Planck domain E~Mp -Quantum Gravity -String theory -no concrete prediction , yet distance UV-IR duality Classical Gravity energy Sub-Planckian domain E<<Mp -gauge interaction -(broken)SUSY -GUT Trans-Planckian Domain E>>Mp -gravity dominance -new windows of bh production open -Classical gravity!! Quantum Gravity SUSY08, Seong Chan Park

  48. Time ? Black Hole’s Life made simple Stolen from: Seong Chan Park (SNU) Balding Phase (Production of BHs. Study “Dynamics” required.) Spin Down Phase (Losing energy and angular momentum :60-80% Energy lost For D>4, to mostly gluons, anisotropic) Schwarzschild Phase (Losing Mass: 20-40% energy, spherical, to every fields) Planck Phase (Remnant ???, Stringy study required ) Stolen from: Seong Chan Park (SNU) SUSY08, Seong Chan Park

  49. Black holes 4 dim. : Rs<< 10-35 m 4+n dim. : Rs~ 10-19 m RS = schwartzschild radius ~ Spherical events: Many high energy jets leptons, photons etc. Ecological comment: BH’s will decay within ~ 10-27secs Detectors, electronics (and rest of the world) are safe!! Simulation of a black hole event with MBH ~ 8 TeV in CMS eno, Road to Discovery, L2

  50. Search for Black Holes Signal MC: Charybdis, Mpl= 1 TeV d=2,4,7 and MBH= from 5 to 14 TeV ATLAS Phys TDR Selection: Object = e,m,g or jet Pt>15 GeV + ID+isolation (lepton/g) Pt>20 GeV (jet)‏ Robust discovery reach potential for BH is difficult because of the semi-classical assumption used, only valid well above MPlMBH > 5 TeV

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