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ハドロンコライダーによるエネルギーフロンティアの物理

–LHCの現状とSMの物理–

松下崇

神戸大学

日本物理学会弘前大学2011年9月17日

2011-09-17 JPS LHCの現状と SMの物理松下崇 (神戸大学) 1/25

• LHC

• ATLAS detector and performance

• Standard Model measurements

• Summary

biased to ATLAS results


Large Hadron Collider at CERN

• The largest accelerator with the highest energy• circumference 26.7 km• proton-proton collisions at 7 TeV CMS energy

CMS

ATLAS

ALICE

LHCb


Large Hadron Collider2011 Instantaneous luminosity

L ! nbNbunch1Nbunch2

!!"n

• Physics runs re-establishedwith 75 ns bunch spacingthen switched to 50 ns

• Increased number of bunchesto 1380 by end of June

• Reduced !n from [2.5 - 3.0]µm to 2.0 µm in July -August

• Reduced "! from 1.5 m to1 m in September

Day in 201124/02 27/03 28/04 29/05 29/06 31/07 31/08 02/10

]-1

s-2

cm

33P

eak

Lum

inos

ity p

er F

ill [1

0

0

0.5

1

1.5

2

2.5

3

3.5

4 = 7 TeVs ATLAS Online LuminosityLHC Stable Beams

-1 s-2 cm33 10!Peak Lumi: 3.29


Large Hadron Collider2011 Integrated luminosity

• 1 fb"1 of data recorded by 17 June

• by today ...• 3.09 fb"1 delivered• 2.92 fb"1 recorded by ATLAS

• best in a day: 116.56 pb"1

• best in 7 days: 499.45 pb"1

Day in 201124/02 25/03 23/04 22/05 20/06 19/07 17/08 15/09

]-1

Tota

l Int

egra

ted

Lum

inos

ity [f

b

0

0.5

1

1.5

2

2.5

3

3.5

4

Day in 201124/02 25/03 23/04 22/05 20/06 19/07 17/08 15/09

]-1

Tota

l Int

egra

ted

Lum

inos

ity [f

b

0

0.5

1

1.5

2

2.5

3

3.5

4 = 7 TeVs ATLAS Online LuminosityLHC Delivered

ATLAS Recorded

- 1Total Delivered: 3.09 fb- 1Total Recorded: 2.92 fb

積分ルミノシティ

(積算

)fb

!1

parameter 2011 designbeam energy [TeV] 3.5 7bunch spacing [ns] 50 25number of bunches 1380 2808!n [µm] 2.0 3.75"!

[m] 1.0 0.55bunch intensity [1011] 1.2 1.15peak luminosity [cm!2s!1] 3.29 x 1033 1 x 1034

stored energy [MJ] !100 3622011-09-17 JPS LHCの現状と SMの物理松下崇 (神戸大学) 5/25

Large Hadron Collider2011 Operational problems

• SEU (single event upset)• Radiation induced malfunction of QPS, Cryogenics, Collimators, Power

Converters...• Dependent on total intensity and luminosity• Relocation of electronics and additional shielding planned in Christmas

technical stop. In the meantime - victim of our own success


Large Hadron Collider2011 Schedule

today

Date in 201107/02 07/0304/04 02/05 30/0527/06 25/0722/08 19/09

/wee

k]-1

Inte

grat

ed L

umin

osity

[pb

0

100

200

300

400

500

Date in 201107/02 07/0304/04 02/05 30/0527/06 25/0722/08 19/09

/wee

k]-1

Inte

grat

ed L

umin

osity

[pb

0

100

200

300

400

500 ATLAS Online Luminosity per WeekLHC Delivered

ATLAS Recorded

= 7 TeVs

積分ルミノシティ

(週毎

)fb

!1

• "40 days left for pp runs in 2011

L ! nbNbunch1Nbunch2

!!"n

• Increase bunch intensity up to 1.55 x 1011 (maximum) [L x 1.7]

• Christmas stop

• Chamonix workshop (6-10 Feb.) to decide run plan in 2012


!テラスケールの物理を探るLHC加速器は順調に動いています次はATLAS検出器とその性能について


ATLAS collaboration

• 38 Countries • 174 Institutions • 3000 Scientists (1000 Students)

• " 150 participants from Japan (" 80 students)

Hiroshima IT, KEK, Kobe, Kyoto, Kyoto UE, Nagasaki IAS, Nagoya, Okayama, Osaka,

Shinshu, Tokyo ICEPP, Tokyo MU, Tokyo Tech, Tsukuba, Waseda, (Kyushu)


ATLASDetector: Exploring a new territory with a precision instrument is the key to discovery

• Length: "45 m

• Diameter: "22 m

• Weight: "7,000 tons

• 2 T solenoida and air-core toroids

• Tracker:|#| <2.5 [0.05 x pT # 1%]

• silicon tracker (pixel + strip)• transition radiation tracker

• Calorimeter:|#| <4.9

• EM: lead/LAr [10/$

E#0.7%]

• hadron: Fe/scint., [50/$

E#3%]

copper/LAr

• Muon system:|#| <2.7 [13% at 1 TeV]

• drift tube, cathode strip chamber• thin-gap chamber, resistive plate

chamber

amajor contribution from Japan


Event pile-up in 2011

Mean Number of Interactions per Crossing

0 2 4 6 8 10 12 14

]-1

Rec

orde

d Lu

min

osity

[pb

- 410

- 310

- 210

- 110

1

10

210=7 TeVsATLAS Online 2011, - 1 Ldt=2.39 fb"

> = 6.2µ<

• distribution of < µ > in simulationre-weighted to reproduce data

Z # µµ event with 11 primary vertices

• need to study e!ects on• vertexing, lepton isolation, jet energy scale, Emiss

T , CPU time/event size


Detector performance

• Luminosity measurement

• Object reconstruction• e/µ• jet• neutrino – Emiss

T

e

µ

jet

jet

EmissT


Luminosity measurementATLAS

L = nbfLHCµvis.

#vis.= nbfLHC

N1N2

2$"x"y

• van der Meer scan for #vis.

• N1,2 from• DC Current Transformer (CT):

total current• Fast Beam CT:

fraction of current in each bunch

• "x,y from van der Meer scans

• µvis. by LUCID, BCM, Calorimeter

• 2011 L uncertainty: ± 3.7%• N1,2 measurement: ± 3.0%

nb : number of colliding bunch pairsfLHC: LHC revolution frequency = 11245.5 Hzµvis.: measured from detector rates!vis. = "!inel.

N1, N2: number of protons in bunch!x ,!y : profiles of the colliding beams

Horizontal Beam Separation [mm]

]-2

p)

11 (1

0-1

) [B

C2

n 1/(n

vis

µ0

0.05

0.1

0.15

0.2

0.25ATLAS Preliminary

LHC fill: 1783

Horizontal Beam Separation [mm]- 0.2 - 0.1 0 0.1 0.2

dat

a#da

ta-f

it

- 3- 2- 10123

· · ·Gaussian + constant

!x (mm)0.2-0.2 0

"x !60µm


Lepton performance

• Re-discovery of known resonancesin 2010

• J/$, !, Z

• performance study with Z # ll• %(mZ ) ! 1.8/2.5 GeV for e/µ• e"ciency with high precision:

%(!) ! ± 1%• electron energy scale with

high-precision: 0.3–1.6% in|#| <2.47

• %(pT )/pT = 13% at 1 TeV inbarrel region

[GeV]eem1 2 3 4 5 10 20 30 100 200 1000

Ent

ries

/ GeV

- 110

1

10

210

310

410

510$J/

%Z

ATLAS preliminary=7 TeVsData 2010,

" - 140 pb&tdL

2.5 3 3.5 4

410

510 $J/

(2S)$

[GeV]µµm

70 75 80 85 90 95 100 105 110 115

Num

ber o

f Ent

ries

/ 1 G

eV

0

10000

20000

30000

40000

50000

60000 = 7 TeV)sdata 2011 (

(Alpgen)µµ 'Z

+ single toptt(( 'Z

DibosonsQCD

)µ 'W

ATLAS Preliminary- 1L dt = 1.02 fb"

Statistical errors onlyMC normalized to data

Muon smearing derived from data

Z " µµ

mee

40 pb"1

1020 pb"1


Jet/missing ET performance

• Jets reconstructed by anti-kT algorithm

• Jet Energy Scale uncertainty• ! 3% in |#| < 0.8 (central)

• Additional uncertainty due to pile-up• 20< pjet

T < 50 GeV: 5% in central• 50< pjet

T < 100 GeV: 2% in central

• EmissT resolution with Z # ll ,

QCD di-jets, minimum bias (MB)

• Fit resolution curve with # = k$

ETk(data) k(MC)

Z " ee 0.42 0.42QCD di-jets 0.51 0.50MB 0.45 0.48• MB di#erence: probably due to

imperfect modelling of soft particleactivity

[GeV]jetT

p20 30 40 210 210!2 310

Frac

tiona

l JE

S s

yste

mat

ic u

ncer

tain

ty

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

ATLAS Preliminary

| < 0.8, Data 2010 + Monte Carlo QCD jets* | +=0.6, EM+JES, 0.3 R tAnti- k

ALPGEN + Herwig + Jimmy Noise ThresholdsJES calibration non- closure PYTHIA Perugia2010Single particle (calorimeter) Additional dead materialTotal JES uncertainty

(event) [GeV]T E,0 100 200 300 400 500 600 700

Res

olut

ion

[GeV

]m

iss

y,E

mis

sxE

0

2

4

6

8

10

12

14

16

T E,MinBias: fit 0.45

T E,QCD di- jets: fit 0.51

T E, ee: fit 0.42 'Z

T E,: fit 0.44 µµ 'Z

ATLASData 2010

- 1Ldt=36 pb" = 7 TeVs

36 pb"1

3%


!テラスケールの物理を探るLHC加速器は順調に動いています!検出器も順調に稼働しており、性能評価も進んでいます

次は標準模型の測定について


Physics programme

• 発見 = 測定結果 % 標準模型

• L =1033 cm"2s"1に於いて• Heavy flavours: ! 100 kHz• Jets (pT = 250 GeV): ! 100 Hz• W " l&: ! 10 Hz• tt̄: ! 0.1 Hz

• ex. Higgs 粒子探索には <1/1010

のselection が必要• Background の理解が重要

0.1 1 1010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

108

109

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

107

108

109

!jet(ETjet > "s/4)

LHCTevatron

!t

!Higgs(MH = 500 GeV)

!Z

!jet(ETjet > 100 GeV)

!Higgs(MH = 150 GeV)

!W

!jet(ETjet > "s/20)

!b

!tot

proton - (anti)proton cross sections

! (n

b)

"s (TeV)

even

ts/s

ec f

or L

= 1

033 c

m-2 s-1

B

Jet

W /Z

top

Higgs


Electroweak boson productions

Higgs

• WW /WZ/ZZ production• the last step before Higgs search• study of triple gauge boson couplings (TGC)

• Background to searches: H # WW , H # ZZ


WW ! l!l!

• sensitive to triple gauge boson coupling

• important background to H " WW

event selection / background rejection

Drell-Yan: fake-EmissT

• Z -mass veto

• require large relative-EmissT

W + jets: fake-lepton

• lepton isolation/identification

top: WW with two b-jets

• jet veto

Other diboson: WZ , ZZ

• no third lepton

pl,jT

EmissT ,rel

EmissT

$'l,j

Eve

nts

/ 5G

eV

1

10

210

310

410

510

610

" - 1Ldt = 1.02fb

ATLAS Preliminary

=7TeVs

DataDrell-YantopW+jets/DijetDiboson

)-µ)+µWW->

[GeV]T,RelmissE

0 20 40 60 80 100 120 140 160 180 200

data

/MC

00.5

11.5

2

Eve

nts

100

200

300

400

500

600

700

800

900

" - 1Ldt = 1.02fb

ATLAS Preliminary

=7TeVs

Data)-l)+WW->l

Drell-YantopW+jets/DijetDiboson

Jet multiplicities0 1 2 3 4 5 6 7 8 9 10

data

/MC

00.5

11.5

2

µµ

EmissT ,rel

llJet multiplicities


WW ! l!l!

• kinematic distributions after selections "• reasonable agreement between data and

predictions

eventsSignal (MC) 232.4± 0.9 ± 21.5top (data) 58.6 ± 2.1 ± 22.3

W + jets (data) 50.5 ± 4.8 ± 14.7Drell-Yan (MC/data) 54.0 ± 3.7 ± 4.5other diboson (MC) 6.8 ± 0.4 ± 0.8total background 169.8 ± 6.4 ± 27.1

S/"

B 17.8observed events 414

Eve

nts

/ 10G

eV

20

40

60

80

100

120

140

160

" - 1Ldt = 1.02fb

ATLAS Preliminary

=7TeVs

Data)-l)+WW->l

Drell-YantopDibosonW+jets/Dijet

stat+syst#

(leading lepton)[GeV]TP0 20 40 60 80 100 120 140 160

data

/MC

00.5

11.5

2

leading-plT

• ! = 48.2 ± 4.0 (stat.) ± 6.4 (syst.) ± 1.8 (lumi.) pb

• Systematic uncertainty dominated by data driven background estimation

• NLO prediction: 46 ± 3 pb

• measurement in agreement with prediction


WZ ! l!ll

• Three leptons and EmissT > 25 GeV

• |mll # mZ | < 10 GeV, mT (W ) > 20 GeV

eventsSignal (MC) 49.1± 0.4 ± 3.02

total background 10.5 ± 0.8 +2.9"2.1

S/"

B 15observed events 71

% = 21.1+3.1"2.8 (stat.) ± 1.2 (syst.)+0.9

"0.8 (lumi.) pb

• NLO prediction: 17.2+1.2"0.8 pb


• limits on anomalous TGC have beenderived

• comparable to Tevatron limit with 1 fb"1

"

!#Z

!gZ1


ZZ ! llll

• Four leptons (eeee/eeµµ/µµµµ)

• Two Z with |mll # mZ | < 25 GeV

eventsSignal (MC) 9.1± 0.1 ± 0.3

total background 0.3 +0.9+0.4"0.3"0.3

S/"

B 16observed events 12

% = 8.4+2.7"2.3 (stat.)+0.4

"0.7 (syst.) ± 0.3 (lumi.) pb

• NLO prediction: 6.5+0.3"0.2 pb


• limits on anomalous neutral TGC havebeen derived

• competitive to LEP/Tevatron limits with1 fb"1

Subleading Z Mass [GeV]40 60 80 100 120 140 160 180 200

Lead

ing

Z M

ass

[GeV

]

40

60

80

100

120

140

160

180

200Data 2011

ZZ

Signal Region

= 7 TeVs - 1 L dt = 1.02 fb"Predicted BG in signal region:

(syst)- 0.3+0.4 (stat) - 0.3

+0.90.3

PreliminaryATLAS

- 1.5 - 1 - 0.5 0 0.5 1 1.5

Z4f

Z5f

-4f

-5f

- 1Ldt = 1.02 fb"ATLAS,

.= /= 7 TeV, s

- 1Ldt = 1.02 fb"ATLAS,

= 2 TeV/= 7 TeV, s

- 1Ldt = 700 pb"LEP,

= 130~209 GeVs

- 1Ldt = 1 fb"D0,

= 1.2 TeV/= 1.96 TeV, s

ATLAS Preliminary

ZZ95% C.I.

f!5

f!4

fZ5

fZ4


top

• combined cross-sections measuredin di-lepton and lepton-jetschannels

!: 176 ± 5 (stat.) +13"10 (syst.) ± 7(lumi.) pb

[TeV]s

1 2 3 4 5 6 7 8

[pb]

tt#

1

10

210

ATLAS Preliminary

pb1316 ±Combined 176

23 pb ±l+jets 186 , Prelim.)- 1(35 pb

pb1719 ±Dilepton 171

, Prelim.)- 1(0.70 fb

pb1316 ±Combined 176

23 pb ±l+jets 186 , Prelim.)- 1(35 pb

pb1719 ±Dilepton 171

, Prelim.)- 1(0.70 fb

NLO QCD (pp)

Approx. NNLO (pp)

)pNLO QCD (p

) pApprox. NNLO (p

CDF

D0

6.8 7 7.2120130140150160170180190200210220

• precision of combined results("10%) already close totheoretical one

• mtop determined with template fitusing lepton-jets channel bycombining 2010 and 2011 data

[GeV]topm160 180 2000.8

11

0.0± 0.0 ± 0.0

Tevatron July 2011 0.8± 0.6 ±173.2

Run- II best (CDF l+jets) 1.1± 0.7 ±173.0

Run- I best (D0 l+jets) 3.9± 3.6 ±180.1

2010+2011 data l+jets prel. 2.7± 0.9 ±175.9

+jets prel.µ2011 data 2.7± 1.0 ±175.9

2011 data e+jets prel. 3.1± 1.2 ±173.9

2010 data l+jets prel. 4.9± 4.0 ±169.3

+jets prel.µ2010 data 5.0± 5.0 ±166.7

2010 data e+jets prel. 4.8± 6.7 ±173.8 ATLAS Preliminary ATLAS (Date: August 15, 2011)

• mtop : 175.9 ± 0.9 (stat) ± 2.7 (syst)

• Tevatron: 173.2 ± 0.6 (stat) ± 0.8 (syst)


Standard Model cross-section measurementscurrent status – ATLAS

measured/predicted cross-sections of SM processesin agreement

W Z -W -Z tt t WW WZ ZZ

[pb]

tota

l#

10

210

310

410

510

- 11 fb

- 11 fb

- 11 fb

- 10.7 fb

- 10.7 fb

)- 1Data 2010 (~35 pbData 2011

Theory

ATLAS PreliminaryATLAS PreliminaryATLAS Preliminary- 1 L dt = 0.035 - 1.04 fb"

= 7 TeVs

- 1 L dt = 0.035 - 1.04 fb" = 7 TeVs

- 1 L dt = 0.035 - 1.04 fb" = 7 TeVs

– statistical error

– total uncertainty

”Yesterday’ssignal is today’scontrol sampleand tomorrow’sbackground”

• probing heavy di-boson productions, the last step before Higgs


Summary

• LHC is performing well• peak and integrated luminosity increasing rapidly• delivered 3.09 fb"1, 6 weeks of pp runs left in 2011

• ATLAS detector is performing well• high data taking e"ciency with high operational fraction of detector• recorded 2.92 fb"1

• understanding of detector and reconstruction performance is progressing

• Standard Model processes re-discovered up to di-boson processes(WW /WZ/ZZ )

• the last step before Higgs searches• measurements in agrement with predictions• precision of measurements quickly catching up to Tevatron results

• Necessary and successfull step before discoveries• discovery = measurements – standard model


…n…h…“…ﬁ…r…›…c… †[‡É‡æ‡é …g…l…‰…m†[…t...

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