Study of WZ production at DØ

Keti KaadzeKansas State University

For DØ collaboration

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 1

MotivationMeasure cross section,

triple gauge couplings

Explore physics beyond the SMThe sequential heavy gauge bosonsSearch for Technicolor resonancesED based Higgsless model, little higgs modelBackground to Higgs searches

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 2

Particles we searched for…

Sequential heave W-like boson, so-called W'

Within low scale TCLight techni-particles have masses < 500 GeVMostly decay with at least one gauge boson

±T/a±

T→W±T; ±T/a±

T→W±Z; T/T→T;

Very distinct signature, narrow resonances

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 3

WW

WWW M

MM '

'' 34)(

D0 detector

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 4

4.1 fb-1 is used in this search

Tracking2T solenoidCalorimetersMuon system

Event selectionFour signatures:

e/ + neutrinoWell identified, isolated,

high energetic leptons − pT >20 GeVInvariant mass constraint on Z boson candidate

80 < Mee < 102 GeV and 70 < M < 110 GeV

R(lZ,lW) = √(2+2) > 1.2Missing transverse energy > 30 GeV

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 5

pW

Z

pl

l

l

BackgroundsProcesses with at least three genuine leptons

WZ and ZZ production − estimated from MC simulation

Instrumental backgrounds due to wrongly identification of a jet, photon from processesZ+jets, Z − estimated using data-driven methodsttbar − estimated from MC simulation and found to

be negligible

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 6

Z+jetsGenuine Z candidate and misidentified jetMeasure the misidentification ratio

in multijet events from data

For each signature Z+”false” lepton sample is selected from datapT spectrum of “false” lepton is folded by fr

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 7

l

jet

l

€

fr =dN dpT (" true")dN dpT (" false")

ZBackground for WZlle

Due to track mismatch or photonconversion

Measure photon to electron misidentification rate in data feUse Z() final state radiation

Photon pT distribution is multiplied by pT dependent e misidentification rate

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 8

FSR

€

NZγ = σ llγ × Ldata × Accep × ε selection × fγ → e

Event yields

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 9

Very good agreement with the SM background prediction

Limits on W'→WZWe exclude sequential W'

188 GeV < M(W') < 520 GeV (obs.)188 GeV < M(W') < 497 GeV (exp.)

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 10

W'WZ coupling

)()()( '2

2'

WMWMSMWWZWZW

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 11

• Variation of coupling affects on (W') and Br(W'→WZ)

W'WZ Obs. (GeV)

Exp. (GeV)

1 (SSM) 520 4974 767 7529 903 88116 988 967

W' width studiesSSM W' is predicted to be a narrow resonance

Stronger W'WZ coupling results in increasing the width of the resonance

We studied and find limits stay within 1s.d. band for for W' resonances with width up to 25% of the mass

WW

WWW M

MM '

'' 34)(

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 12

Width of 500 GeV signal for different coupling strength ()

= 1 (SSM) 2 4 10 20 30Width (GeV)

17 18 22 45 130 271

TechnicolorPrevious searches were done in T/aT→WT→lbq

Allowed only if M(T) < M(T) - M(W)

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 13

Previously excluded region is M(T) < 220 GeV (DØ)

Limits on T→W

We exclude 208 GeV < M(T) < 400 GeV at 95% C.L. (obs.)201 GeV < M(T) < 339 GeV at 95% C.L. (exp.)

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 14

M(T) > M(T) - M(W)

decay to WZ is dominant

ConclusionThe first search for a new resonance in WZ

production is performed at the DØ experimentSSM W' with masses 188-520 GeV is excludedSet limits on W'WZ couplings predicted in

different extensions of the SMExcluded typical TC phase space for heavy

techni-pions

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 15

arXiv:0912.0715v3 [hep-ex]

Published at PRLhttp://prl.aps.org/abstract/PRL/v104/i6/e061801

BACKUP

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 16

W’ Signal cross section & BrSSM(W’->WZ)

February 16, 2010Lake Louise Winter Institute, Keti Kaadze 17