di-boson physics @ the tevatron
DESCRIPTION
Di-Boson Physics @ the Tevatron. Liang HAN. University of Science & Technology of China (USTC). On behalf of the & Collaborations. P-Pbar @ 1.96 TeV, 2x10 32 cm -2 s -1 Vector Boson factory. CDF. DØ. ~ 0.7 million W ~ 0.15 million Z - PowerPoint PPT PresentationTRANSCRIPT
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