CDF Run II 実験の現状報告 １

電弱相互作用 , 　 B の物理

岡山大学理学部　　中　　野　　逸　　夫

CDF collaboration

2003 年 9 月 10 日日本物理学会

ア　ウ　ト　ラ　イ　ン１．はじめに　１．１． TEVATRON　１．２． CDF２．電弱相互作用　２．１．　２．２．　２．３．３． B の物理　３．１．寿　命　３．２．質　量　３．３．分岐比４．まとめ　　　　　

ZW /ZW /

WW

CDFD0

Tevatron

Main Injector + Recycler

１．はじめに

１．１． Tevatron

Main Injector

反陽子生成率の向上

　ビーム強度の増加

Recycler

　反陽子の再利用

　今後

Run IIa ２００１年３月より稼動 6×6@900GeV 36×36@980GeV⇒ 5.2×1031cm-2 sec-1 2003 年８月１１日（ 4.1×1031cm-2 sec-1 2003 年３月　春の学

会 ) (1.6 ×1031cm-2 sec-1 Run 1b)

300pb-1 Delivered 250pb-1 On Tape 130pb-1 Analysis

1.2. CDF( その 1)CDF Detector Overview

SVX: Acceptance increase |z0| < 30 45 cmL00: Vertex resolutionISL: || < 2.0

New Plug Calorimeter 1.3 < || < 3.5

New Central Tracker (COT) ToF counter for K/ separationPlaced right before the Solenoid

Forward Calorimeter3.5 < || < 5.1

Muon DetectorMore Coverage

TOF

=2

=3

=1

Improved Si coverage|| < 2

8 layers

Central Drift Chamber96 layers

Time of Flight

Expanded coverage

Forward Calorimeter

TriggerCOT tracks at L1

Silicon tracks at L2

1.2. CDF( その 2)

2. 電弱相互作用 2.1. （その 1 ）ZW /

σZ • Br(Z→e+e−) = 267.0 ± 6.3 ± 15.2 ± 16.0 pb stat. syst. 　 lumi.

σZ • Br(Z→μ+μ−) = 246 ± 6 ± 12 ± 15 pb stat. syst. lumi.

σW • Br(W→e) = 2.64 ± 0.01 ± 0.09 ± 0.16 nb stat. syst. lumi.

WW·B(W·B(Wμμ) ) 　　 = 2.64 = 2.64 0.02 0.02 0.12 0.12 0.16 nb 0.16 nb

stat syst lumstat syst lum

2.1. ( その 2)

We have a clear Z0eh signal.Further study of backgrounds is underway.

Not only interesting as an EWK measurement, it is important for Higgs and SUSYsearches.

Look for jet within narrow 10 degree cone

Isolated within wider 30 degree cone

pT() > 25 GeV

ETmiss > 25 GeV

Ncand = 2345

σW • Br(W→ ) = 2.62 ± 0.07 ± 0.21 ± 0.16 nb

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 　　 stat. syst. lumi.

Z0τeτh W→τν

ZW /

2.1. ( その 3)W & Z Cross Sections vs. ECM

Our new measurements

NNLO

ZW /

2.1. 　　　　 ( その 4)Lepton Universality in W Decay

ZW /

= = 0.990.990.020.02statstat0.040.04sysy

ss

gg

ggee

syststat 07.004.0 0.99)BR(

)BR(

eW

W)(

)(

eW

WU

W

ZeW

WeZ

ZeW

ZWe

ZZWeWe

ZeZeWW

AA

AA

BNBN

BNBN

))((

))((

WWN

WB

WAW

= Number of candidates

= Number of

= Acceptance for

= Efficiency for

W

Wbackground events

050.0039.0082.1 =

τ-e μ-e

R=(pp->W)　　(W->ll)(pp->Z)　　(Z->ll)　　(W)

2.2. W/ Z ( その 1)

Require central

ET() > 7 GeV ΔR(l-) = √(Δη2+ΔΦ2) >0.7

47 seen

43 expected

133 seen

141 expected

σ　•　Br　=　17.2　±　2.2　(stat.)　±　2.0　(syst.)　±　1.1(lumi.)　pb　　　　　　　　　　　　　　σ　•　Br　=　5.8　±　1.0　(stat.)　±　0.4　(syst.)　±　0.4　(lumi.)　pb

10aSE 岡山大 谷本

Study of Wγ production with W→μν at CDF in Run II

WγZγ

2.2. W/ Z ( その 2)

Wγ and Zγ couplings

Cross sections and mass spectra are consistent with SM

2.3. W W

isolated lepton pair

opposite-charge, high pT

ETmiss

Z vetoveto events with jets∫L　= 126 pb-1

5 events seen (5 with 1.2 ±0.3 BG events in Run I @ ∫L　= 108 pb-1)

9.2 events expected (2.3 background, 6.9 ± 1.5 W W → l l’’)

Higgs, SUSY Search

3. B の物理

B Physics at Hadron Machines

Enormous cross-section~100 barn total

~3-5 barn “reconstructable”

At 4x1031cm-2s-1 ~150Hz of reconstructable BB!!

All B species producedBu,Bd,Bs,Bc,b,…

Large inelastic backgroundTriggering and reconstruction are challenging

b’s produced by strong interaction, decay by weak interaction

3.1. 寿　命（その 1 ）B Hadron Lifetimes

All lifetimes equal in spectator model.Differences from interference & other

nonspectator effects

Heavy Quark Expansion predicts the lifetimes for different B hadron species

Measurements:B0,B+ lifetimes measured to better than 1%!Bs known to about 4%LEP/CDF (Run I) b lifetime lower than HQE

prediction

Tevatron can contribute to Bs,Bc and b (and other b-baryon) lifetimes.

B hadron Average lifetime (ps)

B0 1.534±0.013 B+ 1.653±0.014 Bs 1.439±0.053 Bc 0.18

0.160.46

b 0.0780.0761.233

Heavy　Flavor　Averaging　Grouphttp://www.slac.stanford.edu/xorg/hfag/index.html

)()()()()( 0cbS BBBB ≫

3.1. 寿　命（その 2 ）B+, B0 Lifetimes in J/ Modes

1.51 0.06(stat.) 0.02 (syst.) ps

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1.63 0.05(stat.) 0.04 (syst.) ps(B+

)

(B0)

xy xy B

T

L L mct

p

Proper　decay　length:

Trigger　on　low　pT dimuons　(1.5-2GeV/)Fully　reconstruct

J/,　(2s)+

B+　J/K+

B0　　J/K*, J/Ks

Bs 　J/ b　J/

Bs→J/ψ Φ with J/ψ→μ+μ- and Φ→K+K- B+→ J/ΨK+, B0 →J/ΨK*0 check technique, systematics

BT

Bxy p

mLct

3.1. 寿　命（その 3 ）Bs Meson Lifetime

Bs lifetime - PDG 1.461 ± 0.057 ps 1.33 ± 0.14(stat) ± 0.02(sys) ps

3.1. 寿　命（その 4 ） b Lifetime

Use fully reconstructed bJ/ with J/+ and p

Previous LEP/CDF measurements used semileptonic bcl

Systematics different

1.25 0.26 . 0.10 . psb stat syst

　469　signal

Lxy

+p

primary

65 pb-1

First lifetime from fully reconstructed Λb decay!

B Hadron MassesMeasure masses using fully reconstructed BJ/X modesHigh statistics J/+ and (2s)J/+ for calibration.Systematic uncertainty from tracking momentum scale

Magnetic fieldMaterial (energy loss)

B+ and B0 consistent with world average.

Bs and b measurements are world’s best.

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CDF result: M(Bs)=5365.50 1.60 MeVWorld average: M(Bs)=5369.60 2.40 MeV

CDF result: M(b)=5620.4 2.0 MeVWorld average: M(b)=5624.4 9.0 MeV

3.2. 質　量

SVT incorporates silicon info in the Level 2 trigger… select events with large impact parameter!

Uses fitted beamlineimpact parameter per trackSystem is deadtimeless:

~25 sec/event for readout + clustering + track fitting

-500　　　　-250　　　　　　　　0　　　　　　　　250　　　　　　500

35m 33mresol　 beam = 48m

　SVT impact parameter (m)

Silicon Vertex Tracker (SVT)

d = impact parameter

Primary Vertex

Secondary Vertex

BLxy

Lxy 450m

PT(B) 5 GeV

3.3. 分岐比（その 1 ）

28026　events　=　5.252(4)　GeV/c2　=　41.0(4.0)　MeVc2

M()

charmless two-body decayslonger term Bs modes help extract unitarity angle

Signal is a combination of:B0+ BR~5x10-6

B0K+ BR~2x10-5

BsK+K BR~5x10-5

Bs+K BR~1x10-5

RequirementsDisplaced track trigger

Good mass resolution

Particle ID (dE/dx)

Bh+h

}(4s),Tevatron}Tevatron

tree

Vub

penguin

+ hypothesis

3.3. 分岐比（その 2 ）

BR(BsK+K)Simulation

BdKBsKK

Bd

BsK

32060　events　=　5.252(2)　GeV/c2　=　41.1(1.9)　MeV/c2

M()

Sep.~1.3

CDF　RunII　Preliminary

(dE/dx　–　dE/dx())/(dE/dx)

D*D0,D0K

kinematics & dE/dx to separate contributions

First observation of BsK+K !!

Result: 2.71 1.15

s

d

BR B K K

BR B K

mode Yield (65 pb-1)

B0K 14817(stat.)17(syst)

B0 3914(stat.)17(syst)

BsKK 9017(stat.) 17(syst)

BsK 311(stat.) 17(syst)

Fitted contributions:

3.3. 分岐比（その 3 ）

3.3. 分岐比（その 4 ） 　 BsDs+

New measurement !Previous limit set by OPAL: BR (Bs Ds ) < 13%

BR(Bs Ds ) = ( 4.8 1.2 1.8 0.8 0.6) 10-3

(Stat) (BR) (sys) (fs/fd)

BR result uses less data than shown in plot.

BsDs with Ds + and KK+

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Golden mode for Bs mixing

3.3. 分岐比（その 5 ） Bs Sensitivity Estimate

Current performance:S=1600 events/fb-1 (i.e. effective for produce+trigger+recon)S/B = 2/1D2 = 4%t = 67fs

2 sensitivity for ms =15ps-1 with ~0.5fb-1 of data surpass the current world average

With “modest” improvementsS=2000 fb (improve trigger, reconstruct more modes)S/B = 2/1 (unchanged)D2 = 5% (kaon tagging)t = 50fs (event-by-event vertex + L00)

5 sensitivity for ms =18ps-1 with ~1.7fb-1 of data

5 sensitivity for ms =24ps-1 with ~3.2fb-1 of data ms=24ps-1 “covers” the expected region based upon indirect fits.

This is a difficult measurement.

hadronic mode only

CDF1 event in Bs and Bd search window

Expected bkg 0.54 0.20 (for Bs) 0.59 0.22 (for Bd)

dsB

dsB

60 104.2)( sBBR

3.3. 分岐比（その6 ）

60 104.2)( sBBR @95% CL

3.3. 分岐比（その 7 ） bc with cpK

Backgrounds: real B decaysReconstruct as p: Bd D+K++

Use　MC　to　parametrize　the　shape.　Data　to　normalize　the　amplitude　Dominant　backgrounds　are　real　heavy　flavor　proton　particle　ID　(dE/dx)　improves　S/B

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Fitted signal:

6796 13( .) .

bN stat syst

BR(b c ) = (6.0 1.0(stat) 0.8(sys) 2.1(BR) ) 10-3

New Result !

0

( )

( )b baryon b c

b d

f BR

f BR B D

Measure:

3.3. 分岐比（その 8 ）

Br(bJ/)

In progress

11pSJ6 岡山大　山下

Study of

s

bb

KJBBrXBpp

JBrXpp000 /

/

4. ま　と　め

最大５．２ × １０３１ cm-2sec-1 を達成した。Tevatron Luminosity は順調に増加している。検出器増強も成果を出している。検出器 /トリガー /シミュレーションの理解も深まりつつある。解析に使用可能な積分 Luminosity が１３０ｐｂ－１

に達し Run I の結果を統計精度を上げながら再現。新しい物理結果が出はじめた。

　断面積、寿命、分岐比等