Searches for Extra Dimensions, Leptoquarks, and Technicolor at the LHC
Rencontres de Moriond La Thuile, Italy March 9th - 16th 2013 Jörg Stelzer Michigan State University on behalf of the ATLAS and CMS collaborations A Breakthrough in Physics
ATLAS and CMS jointly announce discovery of Higgs-like particle
CMS The observed σ/σSM for individual (exp.) local p0 for decay modes. For a SM Higgs as a the combination
function of mH. σ/σSM = 0.87 ± 0.23. (ATLAS) (CMS)
Single channel measurements and EW global fit consistent with SM. But convincing?
Within the Standard Model:! Comparison between the direct
measurements of MW and mt (green) and their indirect determination from a global fit to electroweak precision measurements including the “Higgs” (blue).
Fit p-value = 0.08
3/10/13 J.Stelzer - Exo cs Searches 2 Open Questions
§ Is it the SM Higgs and source of EWSB dynamics? • Detailed measurement of properties needed
§ Still room for other, Higgs-less, theories that break EW symmetry? • Technicolor, composite Higgs, extra-dimensional EWSB
§ Other unsolved problems in SM −16 • Hierarchy problem: mEW/MPl ~10 • Dark matter/energy • Matter-antimatter asymmetry • Origin of generations …
➥ Physics beyond the Standard Model (BSM) well motivated
§ Searches for (non-SUSY) physics BSM scenarios in different signatures
Extra dimensions Mono-jet/photon Leptoquarks Exited fermions Diboson High-mass resonances Technicolor ? 4th genera on Same-sign lepton Black holes Contact interac on Dilepton Sequen al SM Large MET
• CMS and ATLAS with ~65 publications each on exotics searches 3/10/13 J.Stelzer - Exo cs Searches 3 BSM @ LHC – Extra Dimensional Models
Address hierarchy problem, effective Planck scale lowered to O(TeV) Large ED model (ADD) • n extra dimensions of size R. For gravity only à weakens gravitational coupling to SM
Reduced Planck scale in 4+n dimensions assumed at O(TeV): 2+n −n 2 M D ~ R M Pl Signatures: • Direct KK graviton emission plus g/γ g/γ g à missing energy and single jet or photon
• Virtual KK graviton exchange, continuous spectrum G à Dilepton, diphoton final states, broad excess over SM l+ G y=πR Randall-Sundrum (RS1, RS2) l- y=0 • One extra warped dimension RS1: for gravity, RS2 for all SM particles
−kRπ k – curvature Scale on weakbrane Λπ ~ M Ple R – size of ED Signatures: • Virtual KK graviton exchange, narrow separated states à resonant excess over SM prediction
3/10/13 J.Stelzer - Exo cs Searches 4 BSM @ LHC – Technicolor Models, Leptoquarks
Technicolor (TC) • Effective theories with a new strong force dynamics to provide mechanism for EWSB • No Higgs (composite Higgs state for EWSB), no hierarchy problem
• Bound states: technimesons �T, �T, ωT, aT • Explorable at LHC: Low scale TC (LSTC) and Minimal Walking Technicolor (MWT) • Search for narrow resonances e.g. in dilepton or diboson final states
Leptoquarks (LQ) • Color-triplet bosons, couple to leptons and baryons of the same generation • Masses at GUT scale, some TC models predict LQ at TeV scale • At LHC: produced in pairs or with associated lepton
• LQ signature: high pT leptons, ET jets, missing ET
3/10/13 J.Stelzer - Exo cs Searches 5 Resonant Di-Boson Production
Spin disentangles resonances § Many SM extensions predict the existence of heavy resonances decaying to pairs of electroweak gauge bosons • W’ in the Extended Gauge Model (EGM) • Technimesons (LSTC) • RS graviton
Charged (WZ/γ) Neutral (WW/ZZ/γγ) § W’ (spin 1) § RS graviton (spin 2) • Triple gauge coupling W’WZ /γ • Fermionic coupling like W
/γ
§ �T (spin 1), aT (spin 0)
ρT/aT
/γ
3/11/13 J.Stelzer - Exo cs Searches 6 → 7.2 -1 Search for resonant ZZ production in Z llqq (l=e/µ) √s = 8TeV ATLAS Signal selection ATLAS-CONF-2012-150
Leptons: ZZ→µµjj candidate in merged region • Above 25 GeV (20 GeV for subleading) • Fiducial constrains, Lepton ID, isolated from hadronic activity, origin PV
• Invariant mass near MZ Jets: • anti-kt algorithm (R = 0.4)
• pT > 30GeV, contained in tracking volume
Two signal regions to treat jet-jet overlap
• Resolved: pT(ll)>50GeV
• Two leading jets: Δφjj<1.6, 65 < mjj < 115 GeV
• Merged: pT(ll) > 200GeV
• Leading jet: pT(j)>200GeV, mj > 40 GeV Only the green jet is considered mμμj = 2.9 TeV, the red is outside the tracking volume
3/10/13 J.Stelzer - Exo cs Searches 7 Search for resonant ZZ production
§ Backgrounds • Z+jets
• Irreducible non-resonant WW/WZ/ZZ Bkgd MC – data comparison (resolved sel) • ttbar (real leptons, different kinematics)
§ Cross check: data compared with MC simulation, after resolved (merged) signal selection is applied
§ Parameterized background estimate
p1 ! (1 x) #mlljj s (resolved) − x = " f (m; p0,1,2,3 ) = p0 #m s (merged) x p2+p3 ln(x) $ llj
§ Use of BumpHunter algorithm (arxiv: 1101.0390) to test for the presence of a resonant signal and fit with the smooth background hypothesis
3/10/13 J.Stelzer - Exo cs Searches 8 Search for resonant ZZ production – Bulk G* limits
Invariant mass distribution (eejj+µµjj combined) + background fit ➡ No signal feature observed Combination uses resolved (merged) selection below (above) 1TeV, as the expected limits are better in the respective regions.
Upper limits on σ× BR (ppàG*àZZ) Limits on bulk RS G* with κ/mPl = 1.0 Upper limit on σ(pp->G*)× BR(G*-> ZZ)
Lower limit mG*: 850 GeV @ 95% C.L.
3/10/13 J.Stelzer - Exo cs Searches 9 13 -1 Search for resonant WZ production √s = 8TeV ATLAS WZ-> lνll signal selection (l=e,m) ATLAS-CONF-2013-007 Average pileup per bunch for 7/8 TeV § Z:
• 2 leptons pT > 25 GeV • Fiducial, isolation, PV, lepton ID
• |mll − mZ| < 20 GeV
§ W: • Lepton with p > 25GeV T Understanding pileup is crucial for missing ET. miss • ET > 25 GeV • < 100 GeV ETmiss resolution vs Number Primary Vtx miss (suppresses events with poor ET )
§ Non-resonant WZ background suppression • �y(W,Z) < 1.8 and ��(W,Z) > 2.6
§ Understanding pileup is crucial • Track based pileup suppression • Pilueup overlay in MC Pileup suppression based on tracks from vertex. Minimum bias events are added to MC. 3/10/13 J.Stelzer - Exo cs Searches 10 Search for resonant WZ production - Backgrounds
§ Diboson background (ZZ, WZ, Zγ, Wγ) estimated from MC • Corrected with lepton data/MC scale factors, normalized to luminosity
§ Fake leptons from ll+jets processes (Z+jets, ttbar, Wt) estimated from data • Di-jet enriched sample to measure lepton-fake factor f • f = ratio between bad (loose) and good (tight) quality leptons • f is applied to samples with two good and one bad quality lepton
§ Two control regions with modified signal selection • WZ control region: �y(W,Z) > 1.8 and ��(W,Z) < 2.6 miss W • Z+jet control region: ET < 25 GeV, mT < 25 GeV
MC-data comparison in WZ control region MC-data comparison in Z+jet control region Diboson background validation
Fake lepton background validation
3/10/13 J.Stelzer - Exo cs Searches 11 Search for resonant WZ production – Result
⤳ no significant excess observed
Z pT spectrum: MC-data comparison after signal selection MWZ spectrum: MC-data comparison after signal selection
Predicted W’ and �T sample signals for illustration
3/10/13 J.Stelzer - Exo cs Searches 12 Search for resonant WZ production – W’ and �T Limits Upper limits on σ× BR (ppàW’àWZ) § Upper limits on σ × BR
§ W’ in EGM pp → W’ → WZ Lower EGM W’ mass limit Expected 1300 GeV Observed 1180 GeV
Exclusion region in m(� ) vs m(� ) plane § Low scale TC T T
pp → ρT → WZ (assuming W′-like kinematics)
Lower ρT mass limit
maT = 1.1mρT 920 GeV
maT≫mρT 920 GeV
Benchmark parameterization: m m m , sin 1 3 ρT = π T + W χ =
3/10/13 J.Stelzer - Exo cs Searches 13 20.6 -1 Non-resonant dilepton searches – ADD Theory √s = 8TeV CMS CMS-PAS-EXO-12-027 § Broad enhancement at large Mll over the SM prediction CMS-PAS-EXO-12-031
Mee spectrum: data, MC, ADD signal § Dilepton event selection and background estimate follows Z’ analysis • See talk of Sam Harper this morning ee • Good MC-data agreement in
control regions Mll < 1.8TeV
§ Signal LO cross-section • UV cut off imposed at Λ to avoid divergences when summing over KK modes • Two possible parameterizations: Mμμ spectrum: data, MC, ADD signal • GRW: single parameter ΛT
• HLZ: n and Ms(Λ)≃MPl(4+n)
§ ADD signal modeled using templates ΛT ∈[1.6,5.2] TeV
• Integrate over signal region Mll∈[1.8,8] TeV μμ
3/10/13 J.Stelzer - Exo cs Searches 14 Non-resonant dilepton searches – Limits on �×BR and ΛT
§ HLZ parameterization • Assume different ranges of validity, § GRW parameterization no signal contribution beyond Mmax
Upper limits on σ× BR (pp→GKK→µµ) Lower limits on MS vs UV cutoff
μμ μμ
MS [TeV] Limits @ 95% C.L. μμ ee combined Channel n=2 n=3 n=4 n=5 n=6 n=7 Expected limit on �×BR 0.25 0.19 μμ 3.69 4.49 3.77 3.41 3.17 3.00 Observed limit on �×BR 0.25 0.19 ee 3.99 4.77 4.01 3.63 3.37 3.19 combined 4.35 4.94 4.15 3.75 3.49 3.30 Lower limit on ΛT (k=1.3) 3.77 TeV 4.01 TeV 4.15 TeV
3/10/13 J.Stelzer - Exo cs Searches 15 Evolution of MS limits
§ CMS combination of ee and μμ channel compared to previous results
Comparison of current CMS limits with previous results
3/10/13 J.Stelzer - Exo cs Searches 16 10.5 -1 19.5 -1 ADD search – mono-Jet and Missing ET √s = 8TeV √s = 8TeV ATLAS CMS ATLAS-CONF-2012-147 CMS-PAS-EXO-12-048
µµ invariant mass in Z+jet control region § Reconstruction, signal selection (ATLAS) • High momentum central jet
• Missing ET (separated from any second jet) • Lepton veto to suppress EW and top background • Four signal regions SR1, …, SR4:
MET and jet pT > (120,220,350,500) GeV
§ Data driven background estimation Leading jet ET/pT in W+jet control region • Z/W+jets, ttbar, diboson • Simulated distributions bin-by-bin corrected using data-derived control regions (Z+jets, W+jets) • QCD multi-jet estimated from jets-enriched data control samples
3/10/13 J.Stelzer - Exo cs Searches 17 Mono-Jet and Missing ET – Results
Leading jet pT spectrum for Signal Region 3 Comparison of data to the SM backgrounds predictions. ADD signal illustrated
⤳ no significant excess observed
3/10/13 J.Stelzer - Exo cs Searches 18 Mono-Jet and Missing ET – Limits on ADD
Upper limits on �×A×� (pp→jet+G ) ATLAS KK n extra dim. LO 95% CL observed limit on MD [TeV]
+0.32 2 3.88 −0.42
+0.21 3 3.16 −0.29
+0.16 4 2.84 −0.27
+0.16 5 2.65 −0.27
+0.13 6 2.58 −0.23 Evolution of lower limits on MD CMS
n extra dim. LO 95% CL observed limit on MD [TeV]
2 5.10
3 3.94 4 3.44
5 3.10
6 2.94
3/11/13 J.Stelzer - Exo cs Searches 19 20.1 -1 19.5 -1 High-Mass Resonances – RS G* Limits √s = 8TeV √s = 8TeV ATLAS CMS • Dilepton resonance search at ATLAS (Sam Harper’s talk) ATLAS-CONF-2013-017 • Dijet resonance search at CMS (John Paul Chou’s talk) CMS-PAS-EXO-12-059 ⤳ no significant excess observed
→ CMS G* gg/qq: mG* > 1.58 TeV (k/MPl=0.1) ATLAS G*→ll: mG* > 2.47 TeV (k/MPl=0.1) Upper limits on �×A×� (pp → G* → gg/qq) Upper limits on �×A×� (pp → G* →ll)
3/10/13 J.Stelzer - Exo cs Searches 20 New results on 7 TeV data
§ LSTC Limits from W� and Z� from ATLAS with 4.6 fb-1 at √s = 7TeV • m > 494 GeV @ 95% C.L. ωT arxiv: 1302.1283 • maT > 703 GeV @ 95% C.L.
ωT→Z� aT→W�
§ 3rd Generation Scalar Leptoquarks from ATLAS with 4.7 fb-1 at √s = 7TeV • M > 534 GeV @ 95% C.L. LQ arxiv: 1303.0526
3/10/13 J.Stelzer - Exo cs Searches 21 Summary
§ ATLAS and CMS study many signatures to look for physics beyond the SM • Presented searches for signatures ADD and RS ED models, LSTC model, and LQ • No significant excess above SM prediction observed • Set stronger limits on σ x BR and on the masses of new particles
§ First analyses using full 8 TeV data are becoming public • Stay tuned for updates on the large number of searches
CMS (ICHEP ’12) ATLAS (HCP ’12)
3/10/13 J.Stelzer - Exo cs Searches 22 BACKUP
3/10/13 J.Stelzer - Exo cs Searches 23 4.9 -1 Diphoton searches √s = 7TeV ATLAS § Looking for KK gravitons in ppà G* à γγ
3/11/13 J.Stelzer - Exo cs Searches 24 RS G* exclusion limits with ll and gg combined
§ Combination of dilepton channel result with γγ channel for RS G* search.
§ Diphoton channel has twice higher BR
3/10/13 J.Stelzer - Exo cs Searches 25