Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://nuclphys.sinp.msu.ru/conf/epp10/Price.pdf Äàòà èçìåíåíèÿ: Sat Sep 7 17:29:45 2013 Äàòà èíäåêñèðîâàíèÿ: Fri Feb 28 02:17:35 2014 Êîäèðîâêà: IBM-866 Ïîèñêîâûå ñëîâà: jet

Higgs searches with ATLAS
Joe Price on b ehalf of the ATLAS exp eriment

27th Aug 2013 Lomonosov Conference


Introduction
ATLAS results from H , H ZZ () llll and H WW presented in earlier talk by Richard St. Denis.


channels already

Focus on more challenging SM Higgs decays and BR limits on inv. decay of Higgs boson.
LHC HIGGS XS WG 2012

102 (pp H+X) [pb] s= 8 TeV
pp H (NNLO+NNLL QCD + NLO EW)

SM x-sec (pb) for mH = 125.5 GeV ggF VBF WH ZH ttH 19 1.6 0.7 0.41 0.13
Higgs BR + Total Uncert [%]
WW bb gg ZZ
LHC HIGGS XS WG 2013

10

1

1

10-1

pp qqH (NNLO QCD + NLO EW) pp WH (NNLO pp ZH (NNLO QCD + NLO EW) QCD +NLO pp EW) ttH (NLO QCD)

10-1

cc

10-2 Z

10-2 80

10-3

100

120

140

160

180 200 MH [GeV]
10-4 80

²² 100 120 140 160 180 200

BR(%) for mH = 125.5 GeV bb WW ZZ 57 22 6.2 2.8 0.23
Joe Price

Z 0.16

²² 0.02
Lomonosov

MH [GeV]

2/21


Bibliography used in this talk
ATLAS Higgs results : https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPublicResults LHC Higgs cross section working group : https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections Channel ï VH Vb b H V H V WW H Z t ïH t ï t t H ²² ï Z H l ï + i nv l AT AT AT AT AT AT AT LA LA LA LA LA LA LA Reference S S S S S S S -CO -CO -CO -CO -CO -CO -CO NF NF NF NF NF NF NF -2013-079 -2012-160 -2013-075 -2013-009 -2013-080 -2013-010 -2013-011 Luminosity (fb -1 ) s = 7 TeV s = 8 TeV 4.7 20.3 4.6 13.0 4.7 20.7 4.6 20.7 20.3 20.7 4.7 13.0

Joe Price

Lomonosov

3/21


ï VH Vb b
Each channel is further divided up into 2/3 jets 5pT bi ns W /Z (pT ) = [< 90], [90 - 120], [120 - 160], [160 - 200], [> 200] GeV. Flavour comp osition of main backgrounds is determined from data. Associated (W /Z )H production, with W l , Z ll and Z , and with H bb .
W /Z

0 lepton (ZH bb ) 1 lepton (WH l bb )
Events Events 80 70 60 50 40 30 20 20 10 Data/MC Data/MC 1.5 1 0.5 50 100 150 200 250 mbb [GeV] 50 100 150 200 250 10 Events ATLAS Preliminary
s = 7 TeV Ldt = 4.7 fb
-1 -1

2 lepton (ZH llbb )
18 16 14 12 10 8 6 4 2 ATLAS Preliminary
s = 7 TeV Ldt = 4.7 fb
-1 -1

s = 8 TeV Ldt = 20.3 fb
V T

0 lep., 2 jets, 2 tags, p >200 GeV

Data VH(bb) (best fit) VZ tt W+bb W+cc W+cl Z+bb Z+bl Z+cc Z+cl Uncertainty Pre-fit background VH(bb) (²=1.0)

ATLAS Preliminary 60 50 40 30
s = 8 TeV Ldt = 20.3 fb
V T

s = 7 TeV Ldt = 4.7 fb

-1 -1

1 lep., 2 jets, 2 tags, p >200 GeV

Data VH(bb) (best fit) VZ Multijet tt t, s+t chan Wt W+bb W+bl W+cc W+cl W+l Uncertainty Pre-fit background VH(bb) (²=1.0)

s = 8 TeV Ldt = 20.3 fb
V T

2 lep., 2 jets, 2 tags, p >200 GeV

Data VH(bb) (best fit) VZ Z+bb Z+bl Z+cc Z+cl Uncertainty Pre-fit background VH(bb) (²=1.0)

1.5 1 0.5

Data/MC

50

100

150

200

250

1.5 1 0.5

50

100

150

200

250

50

100

150

200 250 mbb [GeV]

50

100

150

200 250 mbb [GeV]

Joe Price

Lomonosov

4/21


ï VH Vb b Results
Weighted events after subtraction
ATLAS Preliminary

1 0.8 0.6 0.4 0.2 0

s = 8 TeV Ldt = 20.3 fb 0+1+2 lep., 2+3 jets, 2 tags Weighted by Higgs S/B
-1

s = 7 TeV Ldt = 4.7 fb

-1

Data VH(bb) (best fit) VZ Uncertainty VH(bb) ( ² =1.0)

Background subtracted mbb distribution, combining all regions with S/B weighting
ATLAS Prelim.
mH = 125 GeV
VH(bb), 7 TeV
VH, 0 lepton VH, 1 lepton VH, 2 leptons ² = -2.1+1.4
-1.4 +2.2 -1.9 +2.0 -1.9 +4.0

² = -2.7 ² = -2.5

‘1.1 ‘0.9 ‘0.2 ‘1.8 ‘1.6 ‘0.5 ‘0.4 <0.1 ‘0.8

(stat) (sys) (theo)

Total uncertainty ‘ 1 on ²

² = 0.6-3.6 ‘3.1 ² = 0.6 ² = 0.9
+0.7 -0.7 +1.0 -0.9

50

100

150

200

250

VH(bb), 8 TeV
VH, 0 lepton VH, 1 lepton VH, 2 leptons

mbb [GeV]

² = 0.7+1.1 ‘0.8 -1.1 ² = -0.3-1.3 ‘1.2 ‘0.5 +0.7 ‘0.4 ² = 0.2-0.6 <0.1 +0.9 ² = 0.5 ‘0.8 -0.9
+1.5

²=

0.2+0.7 -0.6

for mH = 125 GeV

Comb. VH(bb)
VH, 0 lepton VH, 1 lepton VH, 2 leptons

² = 0.1 ² = -0.4

+1.0 -1.0 +1.5 -1.4

‘0.8 ‘1.2

s = 7 TeV Ldt = 4.7 fb

-1 -1

-4

-2

0

2

4
5/21

s = 8 TeV Ldt = 20.3 fb

Signal strength [²]

Joe Price

Lomonosov


VH VWW , H WW l l

Complementary to the H WW channel with ggF and VBF production. Search only for leptonic decays of W and Z b osons. Two separate channels: WH WWW l l l and Z H Z WW l l l l .

7.2 (3.2 exp ected) ½ SM prediction for mH = 125 GeV at 95% CL 4 (3.8 exp.) excess when combined with H WW analysis.
Joe Price Lomonosov 6/21


H Z , Z lï l
W Z H

H Z proceeds via electro-weak loops. Much smaller BR than H but can constrain BSM physics indep endently.
Events/4 GeV

Z W H W f H f f W Z

EVENT SELECTION At least 2 isolated high p muons. At least 1 high p R ( , l ) > 0.3.
l T T

1200 1000 800 600 400 200 0 0 20 40 60

ATLAS Preliminary
H Z , Z ee

electrons or



Ldt = 20.7 fb Z+ Z+jets

-1

tt + WZ bkg uncertainty s = 8 TeV Data

isolated photon.
Events/4 GeV

80 100 120 140 160 180 200 220 m [GeV]

ml

Use m = mll - mll as the discriminating variable.

> (mZ - 10) GeV.

1600 1400 1200 1000 800 600 400 200 0 0 20 40 60

ATLAS Preliminary
H Z , Z ²²



Ldt = 20.7 fb Z+ Z+jets

-1

tt + WZ bkg uncertainty s = 8 TeV Data

80 100 120 140 160 180 200 220 m [GeV]

Joe Price

Lomonosov

7/21


H Z , Z lï l
Events/1 GeV

Background determined from data driven method. More statistics required b efore this channel b ecomes sensitive to SM Higgs b oson.
45 40 35 30 25 20 15 10 5 0 120
Joe Price

300 250 200 150 100 50 0 25 30 35

ATLAS Preliminary
Data 2012 HZ (m =125 GeV,
H SM

½20)

s = 8 TeV, Ldt = 20.7 fb-1, Zee 7195 events 40 45 50 55 60 m [GeV]



95% CL limit on (HZ )/SM(HZ )



Ldt = 4.6 fb , s = 7 TeV Ldt = 20.7 fb , s = 8 TeV
-1

-1

Observed Expected ‘ 1 ‘ 2

ATLAS Preliminary

18.2 (13.5 exp ected) ½ SM prediction for mH = 125 GeV at 95% CL

125

130

135

140

145 150 mH [GeV]
Lomonosov 8/21


t ïH t ï t t

Search includes di-lepton, single lepton and fully hadronic t ï decays. t 2 isolated photons, 1 with pT > 40 GeV, the other with pT > 30 GeV. Leptonic:
At least one electron or muon. At least one b-tagged jet. m ET iss > 20 GeV.
Events / 5 GeV 6 5 4 3 2 1
100 2000 110 120 Control region 130

Data ATLAS preliminary SR+CR background fit SM signal (mH = 126.8 GeV) SR-only background fit

Events / 5 GeV

7

Signal region

Leptonic channel

Hadronic:
6 jets, at least 2 b-tagged. Lepton veto.
tH 95% CL limit on ttH/ tSM

10 9 8 7 6 5 4 3 2 1
100 40 20

Data ATLAS preliminary SR+CR background fit SM signal (mH = 126.8 GeV) SR-only background fit

Signal region

Hadronic channel

1000 100 110 120

s = 8 TeV Ldt = 20.3 fb-1
140 150

160

110 120 Control region

130

s = 8 TeV Ldt = 20.3 fb-1
140 150

160

130

140

150 160 m [GeV]

100

110

120

130

140

150 160 m [GeV]

40 35 30 25 20 15 10 5 0

Observed CLs limit H Expected CLs limit ttH channels comb. ATLAS preliminary ‘1 ‘ 2 Data 2012 s = 8 TeV Ldt = 20.3 fb-1



5.3 (6.4 exp ected) ½ SM prediction at mH = 126.8 GeV at 95% CL

120

122

124

126

128

130 mH [GeV]

Joe Price

Lomonosov

9/21


H ²²
Only channel where coupling to second generation can b e measured. Large dataset required.
2 oppositely charged muons, one with pT > 25 GeV another with pT > 15 GeV. Divided into 2 categories, |(²1 , ²2 )| < 1 and 1 < |(²1 , ²2 )| < 2.5 to take advantage of narrower signal width in central region. Background modelled by sum of Breit-Wigner and exp.

9.8 (8.2 exp ected) ½ SM prediction for mH = 125 GeV at 95% CL

Joe Price

Lomonosov

10/21


ZH ll + inv

SM Higgs decay to invisible particles via H Search for enhancements in the inv. decay candidate at mH = 125 GeV and for additi Assume SM production rate and 100% BR

2 OS leptons (pT > 20 GeV) with |mZ - mll | < 15 GeV. Third lepton veto (pT > 7 GeV).
m ET i ss

> 90 GeV.

(l , l ) < 1.7.
m (Z , ET iss ) > 2.6. Z Z m |ET iss - pT |/pT < 0.2.

Events / 30 GeV



m (ET iss

,

m pT iss

< 0.2).

Jet veto (jets with pT > 20 GeV and || < 2.5).

m ET iss distribution after all cuts is used as final discriminator.

á
q ï Z h Z q
+

ZZ () ïï fraction due to BSM onal Higgs decaying i to invisible particles

is very small. physics from SM Higgs nvisibly. for additional Higgs.
Data

Events / 5 GeV


Data / MC

107 106 105 104 103 102 10 1

ATLAS Preliminary s = 8 TeV ZH ll+invisible

Z Multijet W Top WW WZ ZZ (*) (*) SM H ZZ , H WW Signal (SM ZH, m = 125 GeV)
H



L dt = 13.0 fb

-1



-

1.40 1.2 1 0.8 0.6

50

100

150

200

250

300

0

50

100

150

200

250

300

Emiss [GeV] T
50
ATLAS Preliminary s=8 TeV Data Z Top ZZ



L = 13.0 fb WZ WW Other BG

-1

40 30 20 10 0 0

Signal (SM ZH, mH=125 GeV)

50

100

150

200

250

300

350 400 450 miss ET [GeV]

Joe Price

Lomonosov

11/21


ZH ll + inv
95% CL limit: ZH½BR(ZHll inv) [fb] 70 60 50 40 30 20 10 120 140 160 180 200 220 240 260 280 300 mH [GeV]

No excess in search for additional Higgs b osons. Set limits on ½ BR in range 115 < mH < 300 GeV.
1-CL

ATLAS Preliminary ZHll(inv) s=7TeV, Ldt=4.7fb-1 s=8TeV, Ldt=13.0fb-1



ZH,SM

½BR(ZHll inv)

Observed Expected ‘1 ‘2

1

Observed Expected

10-1
ATLAS Preliminary ZHll(inv) s=7TeV, Ldt=4.7fb-1 s=8TeV, Ldt=13.0fb-1

Limit on invisible BR of SM Higgs candidate at mH = 125 GeV. Red lines indicate 68% and 95% CL.

10-2 0

0.2

0.4

0.6

0.8

1

BR(Hinv)
Joe Price Lomonosov

BR (H inv ) < 65% (84% exp ected) for mH = 125 GeV at 95% CL

12/21


H
Analysis yet to b e up dated to full 2012 statistics. Search includes di-lepton (lep hadronic (had had ) channels.
lep lep lep

), single lepton (

lep had

) a nd f ul l y



lep had



had had

2-jet VBF, Boosted, 2-jet VH, 1-jet and 0-jet
Events / 20 GeV Events / 20 GeV 30 25 20 15 10 5 0 0
ee + e² + ²² H +2-jet VBF

VBF, Boosted, 1-jet and 0-jet
Events / 16 GeV 1200 1000 800 600 400 200 0 50 100 150 200 MMC mass m [GeV]
²
had

VBF, Boosted

+ e

had

Boosted

30 25 20 15 10 5 0 0 50



hadhad

H +2-jets VBF



Data 2 x H (125) Z Z ee,²² t t +single-top WW/WZ/ZZ Fake leptons Bkg. uncert.
L d t = 13. 0 f b
-1



Data 5 x H (125) Z (OS-SS) Others (OS-SS) Same Sign Data Bkg. uncert. L dt = 13.0 fb-1

Data 5 x H (125) Z Multi-jet Others Bkg. uncert.



L dt = 13.0 fb-1 s = 8 TeV

s = 8 TeV ATLAS Preliminary

ATLAS Preliminary

s = 8 TeV ATLAS Preliminary

50 100 150 200 250 300 350 400 MMC m [GeV]

100 150 200 250 MMC mass m [GeV]

Joe Price

Lomonosov

13/21


H
Combined 2011 + 2012 data has 1.1 excess ab ove SM background only exp ectation. The observed upp er limit on ½ BR at 95% CL on the H decay is 1.9 ½ SM prediction, 1.2 exp ected. b est fit ² = 0.7 ‘ 0.7 using 8 ATLAS Preliminary H mH = 125 GeV
7 6 5 4 3 2 1 0 100 110 120 130 140 150
Observed CLs Expected CLs ‘ 2 ‘ 1

95% CL Limit on /SM

½ B/BSM

L dt = 4.6 fb-1, s = 7 TeV L dt = 13.0 fb-1, s = 8 TeV

5 4 3 2 1 0 -1 -2 -3

ATLAS Preliminary

VBF+VH



L = 4.6 fb , s = 7 TeV L = 13.0 fb , s = 8 TeV
-1

-1

best fit best fit ( ² >0) 95% Contour 68% Contour SM prediction Background only mH = 125 GeV

²

-2

0

2

4 ²
ggF

6

8

mH [GeV]
Joe Price Lomonosov

½ B/BSM
14/21


Reminder of BSM Higgs analyses
2011 analyses on BSM Higgs searches using 4.7 fb-1 at 7 TeV. MSSM: Charged Higgs:
H and H ²² - JHEP02 2013 095 H + - JHEP 2013 076 H + c ï - Eur.Phys.J C 73 (2013) 2465 s H l ‘l
tan 60 50 40 30 20 10
ATLAS
MSSM combination, 95% CL limit

Doubly charged Higgs:
‘

- Eur.Phys.J. C72 (2012) 2244

(pp H++ H )½ BR(H‘ ‘ l‘ l'‘ ) [fb]

tan

MSSM H

Ldt = 4.7 - 4.8 fb
-1

H
60 50 40 30 20 10 0 90

+

ATLAS mmax s=7 TeV h Data 2011



H l ‘l
10

‘
++ L ++ R

(pp H (pp H

HL ), BR(H‘ ‘ l‘ l'‘ )=1 HR ), BR(H‘ ‘ l‘ l'‘ )=1 Observed Expected Observed Expected Observed Expected limit: limit: limit: limit: limit: limit: e‘ e‘ e‘ e‘ ²‘ ²‘ ²‘ ²‘ e‘ ²‘ e‘ ²‘
--

--

s = 7 TeV mmax, ²>0 h



Ldt = 4.6 fb

-1

Observed exclusion 95% CL Observed +1 theory Observed -1 theory
Observed CLs Expected CLs ‘ 1 ‘ 2 LEP

--

Median expected exclusion

1

ATLAS



Ldt = 4.7 fb-1

s = 7 TeV

100

200

300

400

500

600

m(H‘ ‘ ) [GeV]

100 150 200 250 300 350 400 450 500 mA [GeV]

100

110

120 130 140 150 160 mH+ [GeV]

Joe Price

Lomonosov

15/21


Conclusions and Outlook
Searches for SM Higgs in ATLAS in low-rate final states has b een presented. VH Vbb and H starting to b ecome sensitive to SM Higgs.

Still compatible with both background only and signal plus background expectations.

VH VWW channel gives additional sensitivity to H WW a na l y s i s . H Z + , t ïH and H ²² not yet sensitive to SM Higgs signal. t ï ZH ll + inv sets limit on p ossible BSM physics in the Higgs sector. H and ZH lï + inv still to b e up dated with full 2012 dataset. l
m No excess seen in final ET iss distribution. Direct(indirect) limit of BR (H inv ) at < 0.65(0.6) at 95%CL.

Joe Price

Lomonosov

16/21


Leptonic t ïH t ï candidate event t t

Joe Price

Lomonosov

17/21


Backups

backups...

Joe Price

Lomonosov

18/21


WH WWW l l l
One lepton must have pT > 25 GeV

Exactly 3 isolated leptons, with pT > 15 GeV and total charge ‘1

Split into Z -enriched (one SFOS lepton pair) and Z -depleted (no such pair) Cut Jet multiplicity b-veto m ss ET ,iRel Dilepton mass cut Angular cut overlap Z-depleted Njet 1 Nb-tag = 0 m ss m ss ET ,iRel > 40 GeV ET ,iRel > 25 GeV |mll - mZ | < 25 GeV and mll > 12 GeV mll > 12 GeV l0 l1 < 2.0 Remove events selected by H WW Z-enriched

Joe Price

Lomonosov

19/21


ZH ZWW lïl l l
Cut
m ET i l pT ss m ET iss > 30 GeV highest pT lepton: pT > 25 GeV second highest pT lepton: pT > 20 GeV third highest pT lepton: pT > 15 GeV fourth highest pT lepton: pT > 10 GeV Njet 1 Nb-tag = 0 |ml2 l3 - mZ | < 10 GeV 10 < |ml0 l1 | < 65 GeV 01 < 2.5 2SFOS 1SFOS pT 4l > 30 GeV m4l > 130 GeV Remove events selected by H WW

Jet multiplicity b-veto Mass cuts Angular cut Channel separation pT 4l m4l overlap

Joe Price

Lomonosov

20/21


VH Vbb selection
Object Leptons Jets

0-lepton 0 loose lept

1-lepton 1 tight + 0 loose lept 2 b - tagged jets je pT t1 > 45 GeV je pT t2 > 20 GeV 2 b - tagged jets 1 extra jets
m ET i ss

2-lepton 1 med. + 1 loose lept

m ET i

ss

Vector boson

m ET iss > 120 GeV m pT iss > 30 GeV m m (ET iss , pT iss ) < /2 m min[(ET iss , jet )] > 1.5 m (ET iss , bb) > 2.8 -

> 25 GeV

m ET i

ss

< 60 GeV

W mT < 120 GeV

83 < mll < 99 GeV

Joe Price

Lomonosov

21/21