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

CDF collaboration
2003年
年9月月10日日
日本物理学会逸夫

ア ウ ト ラ イ ン
１．はじめに
１．１．TEVATRON
１．１．
１．２．CDF
１．２．
２．電弱相互作用
２．１． W / Z → ll
２．２． W / Zγ
２．３． WW
３．B
３． の物理３．１．寿 命３．２．質 量３．３．分岐比４．まとめ１．はじめに
１．１．Tevatron
CDF
Tevatron
Main Injector + Recycler

Main Injector

D0

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
年８月１１日（4.1××1031cm-2 sec-1 2003年３月年３月 春の学会)
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
New Central Tracker (COT)New Plug Calorimeter1.3 < |η| < 3.5

Forward Calorimeter3.5 < |η| < 5.1

ToF counter for K/π separation
Placed right before the Solenoid

Muon Detector
More Coverage

SVX: Acceptance increase|z0| < 30 ! 45 cm
L00: Vertex resolution
ISL: |η| < 2.0

1.2. CDF(その2)1=η
Improved Si coverage

TOF|η| < 28 layers

η=2Central Drift Chamber

η=3Time of Flight
Expanded µ coverage
Forward Calorimeter
Trigger

96 layers

COT tracks at L1
Silicon tracks at L2

2. 電弱相互作用
2.1. W / Z → ll（その1）σZ • Br(Z→e+e−) = 267.0 ± 6.3 ± 15.2 ± 16.0 pb
stat. syst. lumi.

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

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

σW·B(W→B(W→μν) = 2.64 ± 0.02 ± 0.12 ± 0.16 nb
statsystlum

2.1. W / Z → ll (その2)

W→τνZ0→τeτh!We have a clear Z0→τeτh signal. Look for jet within
narrow 10 degree cone
!Further study of backgrounds is Isolated within wider
underway.
30 degree conepT(τ) > 25 GeV
ETmiss > 25 GeV
Ncand = 2345

Not only interesting as an
EWK measurement, it isimportant for Higgs andSUSYsearches.

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

syst.

lumi.

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

Our new measurements

NNLO

2.1. W / Z → ll (その4)
Lepton Universality in W Decay
τ-eBR(W → τν )= 0.99 ± 0.04stat ± 0.07 syst
BR(W → eν )

Γ (W → µν )U =gτge = 0.99±0.02stat±0.04sys

Γ (W → e ν )=( NWµ − BWµ )( NZe − BZe) AWeAZµ εZµεWe××( NWe − BWe)( NZµ − BZµ ) AWµAZe εWµεZe

NWµBWµAWµεWµ=R=μ-e= Number of W → µν
candidates= Number of W → µν
background events= Acceptance for W → µν
= Efficiency for W → µν

1.082 ± 0.039 ± 0.050
σ(pp->W) Γ(Ζ)

Γ(W->lνl)

σ(pp->Z) Γ(Z->ll) Γ(W)

2.2. W/ Zγ (その1)
10aSE 岡山大 谷本
Study of Wγ production with W→μνat CDF in Run II

Require central γET(γ) > 7 GeV∆R(l-γ) = √(∆η2+∆Φ2) >0.7Zγ

Wγ
133 seen

47 seen141 expected

43 expectedσ • 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

2.2. W/ Zγ (その2)Wγ and Zγ couplings

Cross sections and mass spectra are consistent with SM2.3. W WHiggs, SUSY Searchisolated lepton pair
opposite-charge, high pTETmiss
Z vetoveto events with jets
∫L = 126 pb-1
5 events seen
(5 with 1.2 ±0.3 BG eventsin Run I @ ∫L = 108 pb-1)
9.2 events expected(2.3 background, 6.9 ± 1.5 W W → lν l’ν’)

3. Bの物理
B Physics at Hadron Machines
b’s produced by strong interaction, decay by weak interaction
Enormous cross-section~100 µbarn total~3-5 µbarn “reconstructable”
At 4x1031cm-2s-1 ⇒ ~150Hz ofreconstructable BB!!

All B species produced
Bu,Bd,Bs,Bc,Λb,…

Large inelastic background
Triggering and reconstruction arechallenging

3.1. 寿 命（その1）
B Hadron Lifetimes
All lifetimes equal in spectator model.
●Differences from interference & othernonspectator effects

Heavy Quark Expansion predicts the lifetimes
for different B hadron speciesτ ( B + ) ≥ τ ( B 0 ) ≈ τ ( BS ) > τ (Λ b ) ≫τ ( Bc )Measurements:●B0,B+ lifetimes measured to better than 1%!
●Bs known to about 4%●LEP/CDF (Run I) Λb lifetime lower than HQE
prediction

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

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

B hadron

Average lifetime (ps)

B0B+
Bs
Bc

1.534±0.013
1.653±0.014
1.439±0.053
0.46+−0.18
0.16

Λb1.233+−0.078
0.076

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

τ(B0) 1.51 ± 0.06(stat.) ± 0.02 (syst.) psτ(B+) 1.63 ± 0.05(stat.) ± 0.04 (syst.) ps

dimuons (1.5-2GeV/µ)-1
L ≈ 138 pb ●Fully reconstruct" J/ψ, ψ(2s)→µ+µ−data" B+→ J/ψK+ct (Sig)" B0 → J/ψK*, J/ψKs
ct (BkgS)" Bs → J/ψφct (BkgL)" Λb→ J/ψΛFit prob: 22%

candidates per 50 µ m

CDF Run II Preliminary
1010104●Trigger on low pT

B0 → J/ ψ K *032101-0.1

0.00.10.2

0.3

ct, cmProper decay length:
Lxy LxymB
ct = =βγpT

3.1. 寿 命（その3）
Bs Meson Lifetime
Bs→J/ψ
ψ Φ with J/ψ→μ
ψ→μ+μ- and Φ→K
Φ→ +KB+→ J/Ψ
ΨK+, B0 →J/ΨK*0 check technique, systematics

candidates per 50 µ m

Bs lifetime - PDG 1.461 ± 0.057 ps
1.33 ± 0.14(stat) ± 0.02(sys) ps
103L ≈ 138 pb

CDF Run II Preliminary

Bs → J/ ψ φdatact (Sig)

102ct (BkgS)
ct (BkgL)
Fit prob: 19.7%

101-0.1

0.0

0.1

0.2

0.3

ct, cm-1mB
ct = Lxy BpT

3.1. 寿 命（その4）Λb Lifetime

Use fully reconstructed Λb→J/ψΛwith J/ψ→µ+µ− and Λ→pπ−

Previous LEP/CDF measurements usedsemileptonic Λb→Λclν
Systematics different
103CDF Run II Preliminary

65pb-1

primary

65 pb-1cτ=374±78(stat)±29(syst)µm
signal region fit

Events/40µm

1103

46±9 signal

background fit

1π−p+µUnbinned Likelihood Fit To ΛB Lifetime

102

10Lxyµ−τ ( Λb ) =1.25 ± 0.26( stat.) ± 0.10( syst.) ps

ΛB mass sideband

102First lifetime from fullyreconstructed Λb decay!

101

1-10000J/ψ cτ µm10002000

3.2. 質 量

Events/5 MeV/c 2

B Hadron Masses
Measure masses using fullyreconstructed B→J/ψX modes
High statistics J/ψ→µ+µ− andψ(2s)→J/ψπ+π− for calibration.
Systematic uncertainty fromtracking momentum scale

CDF Run II Preliminary 80 pb-1

25N(Bs)=71.8 ± 8.2

B s → J/ ψ φ201510Magnetic field
Material (energy loss)

50
5.10

5.15

5.20

5.25

5.30

5.35

5.40 5.45 5.50 5.55 5.60
2
B s candidate mass [GeV/c ]-1

2

CDF Run II Preliminary 70 pb

CDF result:M(Bs)=5365.50 ±1.60 MeV
World average: M(Bs)=5369.60 ±2.40 MeV
CDF result:M(ΛΛb)=5620.4 ±2.0 MeV
World average: M(ΛΛb)=5624.4 ±9.0 MeV

Events/6 MeV/c

B+ and B0 consistent with worldaverage.
Bs and Λb measurements areworld’s best.

30

1614N( Λ b)= 38 ± 7

Λ B → J/ ψ Λ

12108
64
20
5.3

5.4

5.5

5.6

5.7

5.8

5.9

Λ b candidate mass [GeV/c ]23.3. 分岐比（その1）
Silicon Vertex Tracker (SVT)SVT incorporates silicon info inthe Level 2 trigger… select
events with large impactparameter!
SecondaryVertex

LxyPrimaryVertex

35µm ⊕ 33µmresol ⊕ beam
⇒ σ = 48µµm

BPT(B) ≥ 5 GeV
Lxy ≥ 450µµm-500

d = impact parameter

Uses fitted beamline
impact parameter per track
System is deadtimeless:~25 µsec/event for readoutclustering + track fitting+-250
0250500
SVT impact parameter (µµm)

3.3. 分岐比（その2）αγB→h+h−treeβV•ubcharmless two-body decays
longer term Bs modes help extract unitarity
angle γSignal is a combination of:
B0→π+π− BR~5x10-6B0→K+π− BR~2x10-5Bs→K+K− BR~5x10-5Bs→π+K− BR~1x10-5} Υ(4s),Tevatron} Tevatron

penguin280±26 eventsµ = 5.252(4) GeV/c2
σ = 41.0(4.0) MeVc2

Requirements
Displaced track trigger
Good mass resolution
Particle ID (dE/dx)

π+π− hypothesisM(ππ)

3.3. 分岐比（その3）
Simulation
π
Bd→Kπ
Bs→KK
Bd→π π
Bs→K π320±60 eventsµ = 5.252(2) GeV/c2
σ = 41.1(1.9) MeV/c2M(ππ)

BR(Bs→K+K−)
Fitted contributions:
mode

Yield (65 pb-1)

B0→Kπ

148±±17(stat.)±±17(syst)

B0→ππ39±±14(stat.)±±17(syst)

Bs→KK

90±±17(stat.) ±17(syst)

Bs→Kπ

3±±11(stat.) ±17(syst)

kinematics & dE/dx to separate contributions

CDF RunII Preliminary

D*#D0π,Sep.~1.3σ

D0#Kπ(dE/dx – dE/dx(π))/σ(dE/dx)

First observation of Bs→K+K− !!
Result:BR ( Bs → K ± K m )BR ( Bd → K π )±m= 2.71 ± 1.15

3.3. 分岐比（その4）Bs→Dsπ+Golden mode for Bs mixing
50-12about 100 B 0s → D -sπ +4030201005.0CDF Run II Monte CarloCandidates per 10 MeV/cEntries per 20 MeV/c2

CDF Run II Preliminary, L = 119 pb

5.580706050-302010D s π + Mass [GeV/c ]Bs→Dsπ− with0402-B s → D s π+0+
Bs → Ds K
0+
Bs → Ds ρ0-* +Bs → Ds π
0- +Bs → Ds l νother0

5.0

5.52Candidate Mass [GeV/c ]Ds →φπ+ and φ→K−K+BR(Bs # Ds π±) = ( 4.8 ± 1.2 ± 1.8 ± 0.8 ± 0.6) ×10-3
New measurement !

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

Previous limit set by OPAL: BR (Bs # Ds π± ) < 13%

BR result uses less data
than shown in plot.

3.3. 分岐比（その5）Bs Sensitivity Estimate
Current performance:

hadronic mode only

S=1600 events/fb-1 (i.e. σeffective for produce+trigger+recon)
S/B = 2/1
εD2 = 4%σt = 67fs
2σ sensitivity for ∆ms =15ps-1 with ~0.5fb-1 of data
surpass the current world averageWith “modest” improvements
S=2000 fb (improve trigger, reconstruct more modes)
S/B = 2/1 (unchanged)
εD2 = 5% (kaon tagging)σt = 50fs (event-by-event vertex + L00)
5σ sensitivity for ∆ms =18ps-1 with ~1.7fb-1 of data
5σ 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.

3.3. 分岐比（その6）Bs (d ) → µ + µ −Bs (d ) → µ + µ −CDF
1 event in Bs and
Bd search window
Expected bkg
0.54 ±0.20 (for Bs)
0.59 ±0.22 (for Bd)
BR( B 0 s → µ + µ − ) < 2.4 × 10 −6BR(B0s → µ+ µ − ) < 2.4×10−6@95% CL

3.3. 分岐比（その7）Λb→Λcπ with Λc→pKπ
CDF Run II Preliminary (Luminosity 65 pb-1)

83 ± 11 Λ b → Λ c π candidates

2

Events / ( 0.02 GeV/c )CDF II Preliminary

Backgrounds: real B decays
Reconstruct π as p: Bd → D−π+→K+π−π−π+! Use MC to parametrize the shape.

(with dEdx cut on proton)

50! Data to normalize the amplitude

Four-prong B reflections! Dominant backgrounds are real

Other B meson decays
Other Λ b decays

40heavy flavor! proton particle ID (dE/dx)
improves S/B

Λ b → Λ cK
Combinatorial background3020

Fitted signal:

N Λb = 96 ± 13( stat.) +−67 ( syst.)

10055.5

66.5

27mass ( Λ cπ ) (GeV/c )Measure:σ b × fbaryon × BR(Λ b → Λ + c π − )σ b × f d × BR( B 0 → D − π + )New Result !
BR(Λb # Λc π±) = (6.0 ±1.0(stat) ± 0.8(sys) ± 2.1(BR) ) 10-3

3.3. 分岐比（その8）Br(Λb→ΛJ/ψ)In progress
11pSJ6 岡山大 山下

Study of(()σ p p → Λb X Br(Λb → J /ψΛ)000
σ p p → B X Br(B → J /ψK s ))4. ま と め
最大５．２×１０３１cm-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