Di-Boson Physics @ the Tevatron

On behalf of the & Collaborations

Liang HANUniversity of Science & Technology of China (USTC)

Precise test of non-Abelian SU(2)L×U(1)Y

-- complementary to LEP : higher c.m. energy, new couplings of charged currents

Probe TGC (trilinear gauge couplings) -- sensitive to “low” energy remnants of new physics @ high scale

Background to hunting Higgs, top and SUSY

Topology : ≥2 isolated high pT(>15 GeV) lepton(l=e,)/, MET(>20 GeV) for W

P-Pbar @1.96 TeV, 2x1032 cm-2s-1

Vector Boson factory ~ 0.7 million W ~ 0.15 million Z ~ 400 WW, ~ 120 WZ, ~50 ZZ

at L~ 30 pb-1/week

2008/3/2 2L.Han(USTC) "Tevatron diBoson" @Moriond 2008

Main Injector & Recycler

TevatronBooster

p p

DØ

p source

CDF

WZ production @ Tevatron

SM NLO : 3.68 0 b.25p

Unique measurement on WWZ TGC

-- non-SM anomalous as with form factor as Z Z1 1 Z Zg g 1, κ κ 1, λZ

-- Enhancement on production + excess at W/Z high pT spectrum

WZlll search channel :

-- high pT isolated lepton + MET + di-lepton invariant mass around Z

-- eee, ee, e and combined, Br~1.5%

02 2

ˆ( )ˆ(1 / )

aa s

s

2008/3/2 3L.Han(USTC) "Tevatron diBoson" @Moriond 2008

[ PRD 60, 113006 (1999) ]

Evidence of WZ3l @ DØ 1fb-1

13 candidates with 4.5 background ~ 3 significance

( @1.96TeV )PP WZ 1.71.32 pb.7

Anomalous WWZ TGC

(HWZ generator)

=1.5 TeV =2.0 TeV a -0.18<Z<0.22 -0.17<Z<0.21 -0.15<g1

Z<0.35 -0.14<g1Z<0.34

-0.14<Z =g1Z

<0.31 -0.12<Z =g1Z

<0.29

2008/3/2 4L.Han(USTC) "Tevatron diBoson" @Moriond 2008

[ PRD 76, 111104(R) (2007) ]

Observation of WZ3l @ CDF 2fb-1

Cross-section measurement: 25 candidates

(stat) 0.41.31.0

(syst4. umi)pb3 l

Constraint on anomalous WWZ

=1.5 TeV =2.0 TeV a -0.14<Z<0.16 -0.13<Z<0.14 -0.17<g1

Z<0.27 -0.15<g1Z<0.24

-0.86<Z<1.36 -0.82<Z<1.27

2008/3/2 5L.Han(USTC) "Tevatron diBoson" @Moriond 2008

[ PRL 98, 161801 ]

2008/3/2 L.Han(USTC) "Tevatron diBoson" @Moriond 2008 6

WW/WZljj @ CDF 1.2fb-1

First measurement of (l+MET+2jets) @Tevatron :

more statistic sensitive to TGC similar to WHlbb huge background from W+jets, ~300pb

Analysis strategy :

1) NN to increase S/B significance

S/B<1% 3%

2) likelihood fit signal fraction

xBr < 2.88 pb@95%C.L.

(WW+WZ)×Br = 2.09±0.14 pb

Radiation-Amplitude Zero in W

2008/3/2 7L.Han(USTC) "Tevatron diBoson" @Moriond 2008

SM : RAZ (Radiation Amplitude Zero)*cos(θ ) 1

3• Predicted at • Measured as Charge-Sign photon-lepton Rapidity Difference Q[() - (l)]

dip

Study of W(l)RAZ @ DØ 0.7fb-1

2008/3/2 8L.Han(USTC) "Tevatron diBoson" @Moriond 2008

First indication of RAZ :

Photon pT spectrum anomalous WW TGC

ET()>7GeV, R(l)>0.7, l)>90GeV

Full covariance matrix dof17.0/12

2-Bin Statistical analysis :

unimodal hypothesis ruled out @ 2.6 Dip

B

inSm

all

Ma

x B

in

2008/3/2 L.Han(USTC) "Tevatron diBoson" @Moriond 2008 9

Precise Z(ll)measurement @ DØ 1fb-1

ISR : M(ll) ≥ MZ

FSR : M(ll) ≤ MZ

Event selections: ET()>7GeV, R(l)>0.9, M(ll)>30GeV

FSR

ISR

SM NLO : 4.74 ± 0.22 pb. [ PRD 57, 2823 (1998) ]

( Zll) = 4.96 ±0.30(stat+syst)±0.30(lumi) pb.

2008/3/2 L.Han(USTC) "Tevatron diBoson" @Moriond 2008 10

Photon ET spectrum of selected events :

Anomalous ZZ ZTGC@ DØ 1fb-1

[ PLB 653, 378 (2007) ]

First measurement of ZZ @ CDF 2fb-1

Charged 4l channel:

3 events with 0.1 background 4.2 significance

2008/3/2 11L.Han(USTC) "Tevatron diBoson" @Moriond 2008

2008/3/2 12L.Han(USTC) "Tevatron diBoson" @Moriond 2008

Adding the ll channel:

leading order Elemental Matrix likelihood ration (ZZ)

LR(ZZ) (WW)

P

P P

Combined 4l + ll result : 4.4 significance

(ZZ@Tevatro 0.7n) pb0.6

1.4

SM NLO :1.4 ± 0.1 pb. [ PRD 60, 113006 (1999) ]

Search for ZZ @ DØ

SM NLO :

--1.6 0.1pb [ PRD 62, 113011; PRD 60, 072002 ]

-- t-channel only, no tri-linear TGC

Charged 4l channel @1 fb-1 : M(ll) > 30 GeV for eeee, ee, 1 event observed with 0.13 0.03 background expected

Cross section (ZZ/Z*) < 4.4 pb @95%C.L.

The first bounds on ZZZ/ZZ anomalous couplings from Tevatron

2008/3/2 13L.Han(USTC) "Tevatron diBoson" @Moriond 2008

[ hep-ex/0712.0599 ]

2008/3/2 14L.Han(USTC) "Tevatron diBoson" @Moriond 2008

Combined e and channel of ll@ 2.2 fb-1 :

electron channel

Recoil of Z+X discriminating variable Physics background likelihood

Statistic test : 1.77 σ significance predicted → 2.4 σ significance observed

Cross section measurement :

( ZZ) ( ) ( )1.1 0 4 pb. pp stat. sys.2.1

electron channel

muon channel

muon channel

Di-Boson Physics @ Tevatron

2008/3/2 15L.Han(USTC) "Tevatron diBoson" @Moriond 2008

(1) (2)

(3)

(4) (5)

(1) First evidence of W RAZ(2) Z cross-section measurement(3) WW/WZljj semi-leptonic (4) WWZ TGC (5) First evidence of ZZ

Precise measurement from O(102)pb down to O(1)pb @ up to 2fb-1, precise agreement to SM is observed

CDF results http://www-cdf.fnal.gov/physics/ewk/

D0 results http://www-d0.fnal.gov/Run2Physics/ WWW/results/ew.htm

More data coming, and digging hard for Higgs

2008/3/2 L.Han(USTC) "Tevatron diBoson" @Moriond 2008 16

Backup Slides

2008/3/2 L.Han(USTC) "Tevatron diBoson" @Moriond 2008 17

To reduce the contribution of fake MET, no direct cut on MET → build a variable sensitive to “true MET”

decompose di-lepton pT in 2 components with respect to thrust axis:

al: sensible to p

T mis-measurement

at: sensible to recoil activity mis-measurment

build a variable which gives more weight to at

(add in quadrature with different weights) →

balance against activity in the opposite hemisphere

and correct using the corresponding uncertainties

Result:

by construction all uncertainties and

mis-reconstruction can ONLY reduce the value

of

al

at

di-lepton pT

pT1

pT2

thrust axis