Transcript Document

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9月10日
日本物理学会
逸
夫
ア ウ ト ラ イ ン
１．はじめに
１．１．TEVATRON
１．２．CDF
２．電弱相互作用
２．１． W / Z  
２．２． W / Z 
２．３． WW
３．B 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
Main Injector
CDF
Tevatron
Main Injector + Recycler
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
（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
New Central Tracker (COT)
New Plug Calorimeter
1.3 < |h| < 3.5
Forward Calorimeter
3.5 < |h| < 5.1
ToF counter for K/p separation
Placed right before the Solenoid
Muon Detector
More Coverage
SVX: Acceptance increase
|z0| < 30 g 45 cm
L00: Vertex resolution
ISL: |h| < 2.0
1.2. CDF(その2)
Improved Si coverage
TOF
|h| < 2
8 layers
h=2
Central Drift Chamber
h=3
Time of Flight
Expanded  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   （その1）
σZ • Br(Z→e+e−) = 267.0 ± 6.3 ± 15.2 ± 16.0 pb
stat. syst. lumi.
σW • Br(W→e) = 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.
W·B(Wμ) = 2.64  0.02  0.12  0.16 nb
stat
syst
lum
2.1. W / Z   (その2)
Z0τeτh
We have a clear Z0teth signal.
Further study of backgrounds is
underway.
Not only interesting as an
EWK measurement, it is
important for Higgs and
SUSYsearches.
W→τν
Look for jet within
narrow 10 degree cone
Isolated within wider
30 degree cone
pT(t) > 25 GeV
ETmiss > 25 GeV
Ncand = 2345
σW • Br(W→ t) = 2.62 ± 0.07 ± 0.21 ± 0.16 nb
stat.
syst.
lumi.
2.1. W / Z   (その3)
W & Z Cross Sections vs. ECM
Our new measurements
NNLO
2.1. W / Z   (その4)
Lepton Universality in W Decay
τ-e
BR(W  t )
BR(W  e )
 0.99  0.04stat  0.07 syst
U 
gt
ge = 0.990.02stat0.04sys

 (W   )
μ-e
 (W  e  )
( N W   B W  )( N Ze  B Ze )
( N W e  B W e )( N Z   B Z  )
N W
B W
A W

A WeA Z

A W  A Ze
 W   Ze
= Number of W  
candidates
= Number of W  
background events
= Acceptance for W  
 W  = Efficiency for W  
= 1.082  0.039  0.050
R=
 Z W e
(pp->W) (Z)
(W->ll)
(pp->Z) (Z->ll) (W)
2.2. W/ Z (その1)
10aSE 岡山大 谷本
Study of Wγ production with W→μν
at CDF in Run II
Require central 
ET() > 7 GeV
ΔR(l-) = √(Δη2+ΔΦ2) >0.7
Zγ
Wγ
133 seen
47 seen
141 expected
43 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
2.2. W/ Z (その2)
Wγ and Zγ couplings
Cross sections and mass spectra are consistent with SM
2.3. W W
Higgs, SUSY Search
isolated lepton pair
opposite-charge, high pT
ETmiss
Z veto
veto 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’’)
3. Bの物理
B Physics at Hadron Machines
b’s produced by strong interaction, decay by weak interaction
Enormous cross-section
~100 barn total
~3-5 barn “reconstructable”
At 4x1031cm-2s-1  ~150Hz of
reconstructable BB!!
All B species produced
Bu,Bd,Bs,Bc,b,…
Large inelastic background
Triggering and reconstruction are
challenging
3.1. 寿 命（その1）
B Hadron Lifetimes
Heavy Flavor Averaging Group
All lifetimes equal in spectator model.
Differences from interference & other
nonspectator effects
Heavy Quark Expansion predicts the lifetimes
for different B hadron species

t ( B )  t ( B )  t ( BS )  t ( b ) ≫ t ( Bc )
0
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.
http://www.slac.stanford.edu/xorg/hfag/index.html
B hadron
Average lifetime (ps)
B0
B+
Bs
Bc
1 .5 3 4 ± 0 .0 1 3
1 .6 5 3 ± 0 .0 1 4
1 .4 3 9 ± 0 .0 5 3
b
 0.18
0 .4 6  0.16
 0 .0 7 8
1 .2 3 3  0 .0 7 6
3.1. 寿 命（その2）
B+, B0 Lifetimes in J/ Modes
t(B0)
t(B+)
1.51  0.06(stat.)  0.02 (syst.) ps
1.63  0.05(stat.)  0.04 (syst.) ps
Title:
eps/bd-ct- fit- pr oj- sinead.eps
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Trigger
on low pT
dimuons (1.5-2GeV/)
Fully reconstruct
 J/, (2s)+
 B+ J/K+
 B0  J/K*, J/Ks
 Bs  J/
 b J/
Proper decay length:
ct 
L xy


L xy m B
pT
3.1. 寿 命（その3）
Bs Meson Lifetime
Bs→J/ψ Φ with J/ψ→μ+μ- and Φ→K+KB+→ J/ΨK+, B0 →J/ΨK*0 check technique, systematics
Bs lifetime - PDG 1.461 ± 0.057 ps
1.33 ± 0.14(stat) ± 0.02(sys) ps
ct  L xy
mB
B
pT
3.1. 寿 命（その4）
b Lifetime
Use fully reconstructed bJ/
with J/+ and pp
Previous LEP/CDF measurements used
semileptonic bcl
Systematics different
primary
65 pb-1
Lxy

p
p
+

469 signal
t (  b )  1.25  0.26 ( stat . )  0.10 ( syst . ) ps
First lifetime from fully
reconstructed Λb decay!
3.2. 質 量
B Hadron Masses
Measure masses using fully
reconstructed BJ/X modes
High statistics J/+ and
(2s)J/p+p for calibration.
Systematic uncertainty from
tracking momentum scale
Title:
cd
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Magnetic field
Material (energy loss)
B+ and B0 consistent with world
average.
Bs and b measurements are
world’s best.
Title:
cd
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CDF result:
M(Bs)=5365.50 1.60 MeV
World average: M(Bs)=5369.60 2.40 MeV
CDF result:
M(b)=5620.4 2.0 MeV
World average: M(b)=5624.4 9.0 MeV
3.3. 分岐比（その1）
Silicon Vertex Tracker (SVT)
SVT incorporates silicon info in
the Level 2 trigger… select
events with large impact
parameter!
Secondary
Vertex
Lxy
Primary
Vertex
35m  33m
resol  beam
  = 48m
B
PT(B)  5 GeV
-500
d = impact parameter
Uses fitted beamline
impact parameter per track
System is deadtimeless:
~25 sec/event for readout
clustering + track fitting
+
-250
0
250
500
SVT impact parameter (m)
3.3. 分岐比（その2）
a

Bh+h
tree

Vub
charmless two-body decays
longer term Bs modes help extract unitarity
angle 
Signal is a combination of:
B0p+p
B0K+p
BsK+K
Bsp+K
BR~5x10-6
BR~2x10-5
BR~5x10-5
BR~1x10-5
} (4s),Tevatron
} Tevatron
pengui
n
28026 events
 = 5.252(4) GeV/c2
 = 41.0(4.0) MeVc2
Requirements
Displaced track trigger
Good mass resolution
Particle ID (dE/dx)
p+p hypothesis
M(pp)
3.3. 分岐比（その3）
Simulation
BdKp
BsKK
Bdp p
BsK p
32060 events
 = 5.252(2) GeV/c2
 = 41.1(1.9) MeV/c2
M(pp)
BR(BsK+K)
Fitted contributions:
Yield (65 pb-1)
mode
B0Kp
14817(stat.)17(syst)
B0pp
3914(stat.)17(syst)
BsKK
9017(stat.) 17(syst)
BsKp
311(stat.) 17(syst)
kinematics & dE/dx to separate contributions
CDF RunII Preliminary
D*D0p,
Sep.~1.3
D0Kp
(dE/dx – dE/dx(p))/(dE/dx)
First observation of BsK+K !!
Result:
BR ( B s  K K

BR ( B d  K p

)
 2.71  1.15
)
3.3. 分岐比（その4）
BsDsp+
Golden mode for Bs mixing
Title:
bgroup- pr/BsDsPi-PrFit.epsplot display
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BsDsp with
Title:
BsRef lMain.epsdisplay
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Ds p+ and KK+
BR(Bs  Ds p) = ( 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 p ) < 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. effective for produce+trigger+recon)
S/B = 2/1
D2 = 4%
t = 67fs
2 sensitivity for ms =15ps-1 with ~0.5fb-1 of data
surpass the current world average
With “modest” improvements
S=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.
3.3. 分岐比（その6）

B s (d )   

B s (d )   


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

   )  2 . 4  10
BR ( B
6

0
s

   )  2 . 4  10
6
@95% CL
3.3. 分岐比（その7）
bcp with cpKp
Backgrounds: real B decays
Reconstruct p as p: Bd  Dp+K+ppp+
Title:
c1
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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

Fitted signal:
N  b  9 6  1 3( sta t .)  7 ( syst . )
6

Measure:

 b  f baryon  B R (  b   c p )


 b  fd  BR (B  D p )
0
New Result !
BR(b  c p) = (6.0 1.0(stat)  0.8(sys)  2.1(BR) ) 10-3
3.3. 分岐比（その8）
Br(bJ/)
In progress
11pSJ6 岡山大 山下
Study of
(
)
 p p   b X Br (  b  J /   )
(
)
 p p  B X Br (B  J /  K
0
0
0
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