New Physics (Exotics) Searches at the LHC Andreas Warburton - - PowerPoint PPT Presentation

▶
new physics exotics searches at the lhc
SMART_READER_LITE
LIVE PREVIEW

New Physics (Exotics) Searches at the LHC Andreas Warburton - - PowerPoint PPT Presentation

Dec 08, 2022 361 likes •895 views

New Physics (Exotics) Searches at the LHC Andreas Warburton McGill University Representing the ATLAS & CMS Collaborations 19 th International Conference on Supersymmetry & Unification of Fundamental

slide-1
SLIDE 1
  • Andreas Warburton

McGill University

  • Representing the ATLAS & CMS Collaborations
  • 19th International Conference on Supersymmetry &


Unification of Fundamental Interactions SUSY11

  • Fermilab, USA 2011.08.30
  • New Physics (Exotics) Searches


at the LHC

slide-2
SLIDE 2

Introduction

  • Several Exotics / New Physics searches at the LHC

  • Cannot cover all → emphasis on new 1 fb−1 results

  • ATLAS & CMS only: LHCb (B. Pietrzyk’s talk) and ALICE also seek NP

  • Full repositories of latest results:
  • https://twiki.cern.ch/twiki/bin/view/AtlasPublic
  • https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResults

  • This talk does not cover
  • SUSY: See talks by W. Ehrenfeld, I. Melzer-Pellmann, and others
  • Higgs: Next talk by M. Vazquez Acosta
  • Standard Model anomalies
  • (Powerpoint version of this talk has clickable links to the public notes.)

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 2
slide-3
SLIDE 3

Looking beyond the Standard Model

  • Standard Model (SM):
  • An effective theory → has worked very well at energy scales probed so far
  • Expected to break down at higher energies
  • Several limitations, many involving fine-tuning:
  • Hierarchy Problem / Gravity: Reconciling mW and mZ with mPlanck
  • Electroweak Symmetry Breaking: How does it really work?
  • Dark Matter: What is it?
  • Flavor
  • Strong CP Problem
  • …
  • Raison d'être of the Large Hadron Collider (LHC)

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 3
  • http://map.gsfc.nasa.gov/media/080998/index.html
slide-4
SLIDE 4
  • Bunch spacing 50 ns
  • ~ 6 pp collisions / crossing (avg.)

Large Hadron Collider (LHC)

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 4
  • √s = 7 TeV pp
  • Outstanding 2011 Performance
  • ~ 2.4 × 1033 cm−2s−1 peak lumi
  • ~ 80 pb−1 / day
  • ~ 2.7 fb−1 delivered

http://lpc.web.cern.ch/lpc/lumiplots.htm

slide-5
SLIDE 5

5

  • CMS

Two general-purpose experiments: ATLAS & CMS

FNAL, 2011.08.30

  • A. Warburton (McGill)
slide-6
SLIDE 6

Emphasis on excellent resolution (energy, momentum, mass) of electrons, photons, muons

6

  • Two general-purpose experiments: ATLAS & CMS

FNAL, 2011.08.30

  • A. Warburton (McGill)
slide-7
SLIDE 7

7

  • Two general-purpose experiments: ATLAS & CMS

ATLAS

FNAL, 2011.08.30

  • A. Warburton (McGill)
slide-8
SLIDE 8

8

  • 22 m

46 m 38 countries, 174 institutions, 3000 scientists,
 1000 students

Two general-purpose experiments: ATLAS & CMS

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • Emphasis on excellent jet and missing-ET (MET) resolution,

particle identification, and standalone muon reconstruction

slide-9
SLIDE 9

Acknowledgments

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 9
  • Henri Bachacou

6 × 103 Physicists
 in ATLAS + CMS

slide-10
SLIDE 10

Long List of Models & Signatures Available

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 10
  • Henri Bachacou
slide-11
SLIDE 11

Long List of Models & Signatures Available

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 11
  • Henri Bachacou

For Experimentalists:

  • Complex 2D

problem

  • Signature

approach:

  • Practical
  • Less model-

dependent

  • Important to seek

as many signatures as possible

slide-12
SLIDE 12

Selected Searches

  • Heavy Resonances
  • Heavy gauge bosons
  • Diboson (γγ, WZ )
  • Dijet
  • Doubly charged Higgs

  • Quark Exotica
  • tt resonances
  • tt + MET (missing transverse energy)
  • 4th quark generation

  • Strong Gravity
  • Monojet
  • Monophoton
  • Dimuon/diphoton spectrum
  • Black holes

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 12
  • This talk: results up


to 1.6 fb−1

slide-13
SLIDE 13

Search for Heavy Resonances

  • Predicted by several extensions to the SM

  • GUT-inspired theories, Little Higgs → heavy gauge

boson(s) Z’ (W’)

  • Technicolor → narrow technihadrons
  • Randall-Sundrum ED → Kaluza-Klein graviton
  • Experimental Challenges

  • Very high momenta
  • Need to understand detector resolutions, efficiencies;


→ dearth of data-driven control samples

  • Confidence in alignments, Monte Carlo simulation

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 13
  • Lepton momenta


approaching 1 TeV!

arXiv:1108.1316

slide-14
SLIDE 14

Neutral Heavy Resonance: e+e− & μ+μ− Channels

  • Randall-Sundrum Kaluza-Klein graviton excitation
  • GUT-inspired heavy Z' boson
  • Technihadron

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 14
  • CMS PAS EXO-11-019

arXiv:1108.1582

ee μμ

Drell-Yan Z/γ* bkgnd dominates both channels

slide-15
SLIDE 15

Neutral Heavy Resonance: Dilepton

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 15
  • Randall-Sundrum Kaluza-Klein

graviton excitation

  • GUT-inspired heavy Z' boson
  • Technihadron

Sequential SM (SSM): m(Z') > 1.9 TeV at 95% CL

  • RS KK graviton (k/MPl = 0.1)

m(GKK) > 1.8 TeV at 95% CL

CMS PAS EXO-11-019 arXiv:1108.1582

slide-16
SLIDE 16

Charged Heavy Resonance: W' è (e,μ)ν

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 16
  • Heavy charged gauge boson
  • Technirho, Little Higgs
  • 1 electron or muon & missing ET
  • Seek Jacobian peak in mT distribution

CMS PAS EXO-11-024 arXiv:1108.1316

μν eν

SM W high-mass tail background dominates both channels

slide-17
SLIDE 17

Charged Heavy Resonance: W'

  • Sequential SM W': excluded up to 2.27 TeV at 95% CL

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 17
  • arXiv:1108.1316

CMS PAS EXO-11-024

slide-18
SLIDE 18

Search for Heavy Resonance: WZ

  • W' or ρTC → WZ

All-leptonic channel: W→l±ν and Z→l+l− Reconstruct m(WZ) by
 constraining m(l±ν) to m(W)

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 18
  • →

HT
 cut Pre-selection Final selection

CMS PAS EXO-11-041

SM WZ → 3lν background dominates

slide-19
SLIDE 19

Search for Heavy Resonance: WZ

  • W' or ρTC → WZ

All-leptonic channel: W→l±ν and Z→l+l−

Sequential SM: M(W') > 784 GeV at 95% CL Technicolor: ρTC > 382 GeV at 95% CL

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 19
  • CMS PAS EXO-11-041
slide-20
SLIDE 20

Search for Heavy Resonance: diphoton channel

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 20
  • Randall-Sundrum Kaluza-Klein (KK)


graviton excitation search RS graviton (k/MPl = 0.1): m(GKK) > 1.7 TeV at 95% CL

CMS PAS EXO-11-038

Preferential decay to photons (in lieu of fermions) on spin grounds

slide-21
SLIDE 21

Search for Dijet Resonances

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 21
  • Probing for


quark structure
 beyond 4 TeV

  • Well-suited for early searches at hadron colliders
  • q*, axigluon, colour-octet scalar, string resonance…
  • Seek resonance above phenomenological fit to data

m(jet-jet) = 4000 GeV Missing ET = 100 GeV →

arXiv:1107.4771 ATLAS-CONF-2011-095

Most discrepant region

slide-22
SLIDE 22

Search for Dijet Resonances

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 22
  • Also setting model-independent limits:

arXiv:1107.4771 ATLAS-CONF-2011-095

Generic limits on
 dijet resonances 


  • f specific widths

Easily
 adaptable to other 
 New Physics models

slide-23
SLIDE 23

Inclusive Search: Same-Sign Prompt Dimuon

  • Predicted by many models
  • Very clean signature; little to lose

by being inclusive

  • Inclusive, model-independent

search:

  • Fiducial cross-section limit as

function of m(μ±μ±)

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 23
  • ATLAS-CONF-2011-126

Broad range of
 muon kinematics:

slide-24
SLIDE 24

Heavy Resonance Search: Same-Sign Dilepton

  • Extend inclusive search →

Doubly charged Higgs search

  • Based on same analysis as inclusive search
  • Window 10% around Higgs mass
  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 24
  • Assuming BR(μ+μ−) = 100%:
  • m(HL) > 375 GeV (exp. 342 GeV) at 95% CL
  • m(HR) > 295 GeV (exp. 286 GeV) at 95% CL
  • ATLAS-CONF-2011-127
slide-25
SLIDE 25

Selected Searches

  • Heavy Resonances
  • Heavy gauge bosons
  • Diboson (γγ, WZ )
  • Dijet
  • Doubly charged Higgs

  • Quark Exotica
  • tt resonances
  • tt + MET (missing transverse energy)
  • 4th quark generation

  • Strong Gravity
  • Monojet
  • Monophoton
  • Dimuon/diphoton spectrum
  • Black holes

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 25
slide-26
SLIDE 26

Top-Antitop Pair Searches

  • Topic of great experimental and theoretical interest
  • 3rd generation may play a special role in EWSB
  • Reaching the TeV scale; new experimental techniques demanded
  • Now entering era of boosted top and top-tagging! (à la boosted b-quarks in the 1990s)
  • (See also Clemens Lange talk tomorrow)

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 26
  • CMS PAS EXO-11-006

tt Decay Modes Top
 Jets!

slide-27
SLIDE 27

tt Resonance Searches: Jet “Top”-ology

  • Boosted All-Hadronic Final State

Seek RS Kaluza-Klein gluons

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 27
  • Both W bosons from top


decay hadronically (BR ~ 46%) Model-independent σZ’ limits

  • m(gKK) > 1.5 TeV at 95% CL
  • Particle Flow, Run 166864 Event 457688464

CMS PAS EXO-11-006

→ W subjet candidates

slide-28
SLIDE 28

Top-Antitop Resonance Searches

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 28
  • muon + jets signature

Seek Z' (narrow heavy resonances) Leptophobic Top-Color Z'

  • Sub-picobarn limits
  • m(Z') > 1.35 TeV at 95% CL

CMS PAS EXO-11-055

slide-29
SLIDE 29

Top-Antitop Resonance Searches

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 29
  • lepton (e,μ) + jets signature

Seek Z' or Kaluza-Klein gluons Resonance mass exclusions:

  • Strongly produced, wide:
  • RS Kaluza-Klein gluon ( < 650 GeV)
  • Weakly produced, narrow:
  • Leptophobic Top-Color Z' (no exclusion)

ATLAS-CONF-2011-087

Secondary
 vertex b-tagging

slide-30
SLIDE 30

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 30
slide-31
SLIDE 31

Dilepton Resonance Searches

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 31
  • Dilepton signature (cf. l + jets: lower BR, but lower background)

Potentially sensitive to Kaluza-Klein gluons, graviton excitations, …

  • Benchmark Limit: m(gKK) > 840 GeV at 95% CL

ATLAS-CONF-2011-123

t / t /

− (Scalar Sum of signal objects’ pT )

slide-32
SLIDE 32

Search for a 4th Generation Quark: t' → Wb

  • t' → Wb: top-like signal (l+jets, dilepton), but

heavier

  • Select: single charged lepton,

4 jets (1 b-tagged) with high ET 
 large MET

  • Experimental challenge: large tt background,

sensitive to calibration and modeling

  • Excluded at 95% CL up to 450 GeV

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 32
  • CMS PAS EXO-11-051

Reconstructed fit mass Scalar ET sum

slide-33
SLIDE 33

Search for a 4th Generation Quark: t' → Wb

  • t' → Wb: top-like signal (l+jets, dilepton),

but heavier

  • Experimental challenge: 


large tt background, 10% high-pT b-tagging systematic

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 33
  • Limit: m(t') > 422 GeV at 95% CL

CMS PAS EXO-11-050

slide-34
SLIDE 34

Search for Heavy Bottom-like Quarks: b' →Wt

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 34
  • Signature: trileptons or like-sign dilepton, ≥1 b-jet

Limit: m(b') > 495 GeV at 95% CL

CMS PAS EXO-11-036

b'b' → Wt Wt → WWb WWb (Like tt+WW; Hard to miss!) Dilepton Trilepton

slide-35
SLIDE 35

lepton + jets signature

Top-Antitop + MET

  • Exotic top partner, decaying to


SM top + stable neutral scalar:

T T → t t A0 A0

Predicted by several DM-motivated models

  • A0: Dark Matter candidate
  • Selection:
  • single high pT isolated lepton
  • ≥ 4 jets
  • MET > 100 GeV

Good understanding of MET is important

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 35
  • ATLAS-CONF-2011-(TBA)
slide-36
SLIDE 36

Top-Antitop + MET

  • New heavy particles:

T T → t t A0 A0

  • No signal apparent yet

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 36
  • Exclude at 95% CL: heavy quark-like


states decaying to top plus
 a new neutral particle, e.g.,

  • T with m(T) < 420 GeV decaying


to A0 with m(A0) = 10 GeV

ATLAS-CONF-2011-(TBA)

Theory: Alwall, Feng, Kumar

slide-37
SLIDE 37

Selected Searches

  • Heavy Resonances
  • Heavy gauge bosons
  • Diboson (γγ, WZ )
  • Dijet
  • Doubly charged Higgs

  • Quark Exotica
  • tt resonances
  • tt + MET (missing transverse energy)
  • 4th quark generation

  • Strong Gravity
  • Monojet
  • Monophoton
  • Dimuon/diphoton spectrum
  • Black holes

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 37
slide-38
SLIDE 38

Search for Monojets

  • Large Extra Dimensions (ADD)
  • Graviton escapes detection
  • Seek a jet with ~nothing else
  • Challenges:
  • Instrumentation background
  • Understanding SM Z(→ νν) + jets

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 38
  • CMS PAS EXO-11-059

ATLAS-CONF-2011-096

slide-39
SLIDE 39

Search for Monojets

  • Extra Dimensions (ADD)


now pushed beyond 2 TeV

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 39
  • ATLAS-CONF-2011-096

CMS PAS EXO-11-059

MD > 3.7 TeV at 95% CL

slide-40
SLIDE 40

Search for Monophoton

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 40
  • Large Extra Dimensions (ADD)
  • Graviton escapes detection
  • Like monojet, seek a photon with

~nothing else

  • For n = 2 – 6
  • MD > 1.25 – 1.31 TeV at 95% CL

CMS PAS EXO-11-058

slide-41
SLIDE 41

Nonresonant Dimuon/Diphoton LED Searches

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 41
  • Dimuon

Large Extra-D (ADD): KK graviton tower with ΔM << detector resolution Diphoton: MS lower limits [TeV] at 95% CL Dimuon: (n = 3) MS > 3.22 TeV Seek
 deviation
 in the SM
 spectrum

  • Isolated


muon candidates

CMS PAS EXO-11-039 CMS PAS EXO-11-038

continuum
 feature

DY

slide-42
SLIDE 42

Black Holes: Multi-Object, Multi-Jet, Same-Sign

  • Microscopic black holes decaying

via Hawking radiation


  • Models uncertain due to lack of

knowledge about quantum gravity


  • Semi-classical models:


m(BH) >> m(threshold) = MTH


  • Safe bet: decay is democratic and

isotropic, likely high particle multiplicity → look for many jets and leptons at high mass

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 42
  • ATLAS Simulation:

1µ 2e many jets

CMS data: 10 jets Total Trans. E = 2.5 TeV

CMS PAS EXO-11-071

slide-43
SLIDE 43

Black Holes: Multi-Object, Multi-Jet, Same-Sign

  • Inclusive search: sum energy of all
  • bjects (e, μ, jets)

  • Can also select peculiar events:

e.g., same-sign dilepton with very high track multiplicity

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 43
  • At least 6 objects

Total Transverse Energy

→

→

ATLAS-CONF-2011-065 CMS PAS EXO-11-071

High-pT Track Multiplicity

NTracks ≥ 10

9-object CMS
 event

slide-44
SLIDE 44

CMS Exotics Searches: Summary

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 44
  • (table does not contain latest results)
slide-45
SLIDE 45

ATLAS Exotics Searches: Summary

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 45
slide-46
SLIDE 46

Concluding Remarks

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 46
  • Hats off to the LHC for an outstanding year of 7 TeV pp

collisions: quick provision of quality and quantity


  • ATLAS and CMS all-purpose detectors are already performing

near design specifications


  • Experimental challenges lie ahead (multi-TeV, high lumi):
  • Pileup
  • TeV leptons, boosted object reconstruction
  • New, more complex signatures

  • Experimentally, we’ve now not only opened the door to the

“House of New Physics”, but also stepped inside, to find nothing obviously exotic… in the foyer


  • Still very early days; many rooms remain to be explored!
slide-47
SLIDE 47

Extra Material

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 47
slide-48
SLIDE 48

New Physics Searches: Key Ingredients

  • Maximize signal efficiency
  • Data-driven methods (e.g., tag-&-probe)
  • Can be tricky for very exotic signals

  • Reliable background estimations
  • Understanding of detector
  • Data-driven methods

  • Trade-offs in analysis approaches:
  • Setting strong limits
  • Robust discovery!

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 48
slide-49
SLIDE 49

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 49
  • CMS & ATLAS Detectors: Basic Parameters
slide-50
SLIDE 50

Heavy Neutrinos, LRSM WR

  • LRSM approaches
  • Search for resonance in 2-lepton

+ 2-jet system

  • Majorana neutrino → expect

50% same-sign (clean signature)

FNAL, 2011.08.30

  • A. Warburton (McGill)
  • 50
slide-51
SLIDE 51

Heavy Neutrinos, WR

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 51
slide-52
SLIDE 52

W+2j Production Cross Check

  • FNAL, 2011.08.30
  • A. Warburton (McGill)
  • 52
  • ATLAS-CONF-2011-097