exotica: overview of the searches for new vector boson high mass states

Exotica: Overview of the Searches for New Vector Boson High Mass States

Cory Fantasia

PY898

03/30/09

The Exotic:

Z′ W′ RS Graviton

3 Particles

Z′ W′ RS Graviton

Z′ Models

Sequential Standard Model (SSM) Same Coupling Strength as SM Z Simplest extension of SM Basis for this talk

Littlest Higgs E6 and SO(10) Grand Unifying Theories Kaluza-Klein Excitation of SM Z

Z′ - Tevatron

Dilepton channel Z′ → ee Z′ → μμ Z′ → ττ Z′ → t tbar

With 450 pb-1 CDF limits SSM Z′ to 825 GeV Dielectron / dimuon channels most powerful Other models are less strict on mass

Search Z′ → μμ

Channel will offer first glimpse of signal

Using first data assumptions Misalignment Larger uncertainties

Decay Modes - Z′

Z′ → ee Z′ → μμ Z′ → WW

Harder to utilize

Background Z′

Photons Require track

QCD Jets Require isolation Require > 90% of energy to be in ECAL Require hits in muon system

Require oppositely charged leptons Drell-Yan (irreducible) – find mass peaks

Discovery

Z′ →WW

Peak resolution more difficult

Clearest channel WW → eν jj Allows for discrimination

between two W’s Aids in background

suppression Background

W + jets

Discovery - Z′ → WW

Using Cuts |η| < 2 for jets ET of W > M(Z′)/3 Reconstructed W’s good

mass values (|diff| < 15) Assumes coupling falls

off like 1/m(Z′)2

300 fb-1

3 Particles

Z′ W′ RS Graviton

W′

Sequential Standard Model Same couplings as W

Makes signal more difficult to extract MET is now a factor

W′ - Tevatron Results

Using W′ → eν or W′ → t bbar Minimum mass set to 788 GeV using 205 inv

pb-1

Set with leptonic decays

W′ → μ ν

Require single muon Isolation >13 hits along track Largest source of

background is SM W Must use reconstructed

mass peak

Discovery

Discovery potential with 1 fb-1 up to 3.5 TeV

W′ → e ν

Largest source of background comes from SM W decays Use similar cuts to

resolve mass peak Isolated, tracked

W′ → WZ → 3l + ν

Resolution (with no cuts) decreases with increasing mass

W′ still visible past 2 TeV with 300 fb-1

W ′ → WZ → 3l + ν Opposite signed leptons

form Z Leaves lepton + MET to

form W

Background

WZ → 3l + ν Mass peak distinction

ZZ → 4l 1 lepton missed (shows up as MET)

tt → Wb Wb b quark yields a lepton plus 2 from W’s b lepton won’t be isolated

W′→ WZ Discovery

300 fb-1

Using worst case model to obtain 5 sigma assuming coupling falls off like 1/m(W′)2

W′ (Higgsless)

W′ Z → WZZ → jj4l Remove

reconstructed Z mass (oppositely charged leptons)

Remaining WZ mass shows peak

Cuts - W′ Z → WZZ → jj4l

Require large (>4) η separation between jets Reduces gluon jet

background

Ej > 300 GeV

pTj > 30 GeV

pTl > 10 GeV

Discovery - Higgless

Larger cross section of WZjj offers chance of quicker discovery as the mass of the W′ increases

3 Particles

Z′ W′ RS Graviton

RS Graviton

Motivation? Explain Weakness of Gravity

Difference between Planck mass and TeV Scale Unify Gravity with other forces

Theory

Lisa Randall and Raman Sundrum 15 Orders of Magnitude between Mplanck and

TeV scale Expand Universe to 5th Dimension

Scales ~ e-kπR

kR ~ 11 k ≡ curvature of new dimension R ≡ is the size of the dimension

Theory

TeV Brane → Planck Brane SM interactions exist on TeV Brane

Can propagate in 5-D SM particles fixed between these branes Since Higgs is on TeV Brane, the closer a SM

particle lies to TeV Brane the larger its mass “Naturally” form mass hierarchy

Production

c ≡ k/Mplanck

Dominate factor is graviton interactions

Discrimination – RS

Spin 2 particle Different angular distribution Use θ*

Angle between quark and lepton

G → ee High energy electron jets

End Caps are Critical for Discrimination

Signal over Background

E > 100 GeV Isolated 2 Hit Track > 90% of energy in

ECAL

Discovery CMS

c = 0.01 (green) c = 0.02 (blue) c = 0.05 (pink) c = 0.1 (red) With similar cuts

Isolated High Energy

Discovery CMS

Depending on the coupling parameter discovery could come with 1 fb-1

Conclusions

Z′ muonic decay offers best hope seeing signal early Subsequent use of electron decay for

confirmation and refinement of signal W′ searches will require more work

MET in the final state RS Graviton offers exciting answers but will

need a more careful analysis