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...
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Transcript of 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 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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Title:cdCreator:ROOT Version 3.02/07Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.
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