1
Charm physics in CDF
Sandro De Cecco, INFN Roma1 for the CDF Collaboration
Incontri di Fisica delle Alte EnergieFesta della liberazione, 2003, Lecce
IFAE 25-aprile 2003, Lecce Sandro De Cecco, INFN Roma 1 2
Tevatron Run II
Main Injector(new)
Tevatron
DØCDF
Chicago↓
p source
Booster
Run II: proton-antiproton collisions at √s=1.96 TeV
CDF
IFAE 25-aprile 2003, Lecce Sandro De Cecco, INFN Roma 1 3
Tevatron pp collider
Main Injector: injector optimizes p production
Collision rate: 396 ns crossing time(36x36 bunches) ~ 2M collisions per second
Center of Mass energy: 1.96 TeV
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Current Tevatron statusInitial Luminosity (1030 cm-2 s-1)
Today: record luminosity: 4.3x1031cm-2s-1
4 to 7 pb-1 /week delivered
Goal: inst. luminosity: 5-8 x 1031 cm-2s-1
2 fb-1 in run IIa
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Outline•CDF detector & trigger overview•Charm Physics topics– J/ψ production cross section– Charm production cross section– Mass: Ds and D+
– Cabibbo suppressed D0 decay– CP violation– D0 mixing– Rare Decays, D0 µµ
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Tracking: Si strips + drift chamber (in 1.4T )• 3D-track, 7/8 layers, | η| < 2, 1.6 cm < R < 28 cm
• 100 ns drift , 0.3 m < R < 1.4 m, σ(1/PT) ~ 0.1% GeV-1 , dE/dx info
Muons:
•Central: |η|< 1
•Fwd: 1< |η|< 1.6
Time of flightScintil. PID (p,K,π)
100 ps @ 140 cm
EM + HAD calor.
• Central: scintillat.
• “Plug” :tile-fiber
Trigger2D-silicon tracks
at Level2
SELECT:
b/c events from background reconstructing a decay vertex displaced wrt the point of primary interaction
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Integrated Luminosity
Mar 02
Data used for results :Mar 02 – Jan 03130 pb-1 (delivered)100 pb-1 (to tape)
After: good run, Silicon conditionsB/Charm: ~ 70 pb-1
Jan 03
commissioning
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CDF CLEO
Beauty and Charm physics at pp collider
• Total inelastic x-section (70 mb) ~ 103 - 104 × σ(bb/cc)
x-section bb/cc is O(105)/O(106)larger than e+e- @ ϒ(4S) or @ Z0
Open wide spectrum of B/D hadrons:B±, B0, Bs, Bc, Λb, Ξb ……D±, D0, D*, Ds, Λc, Ξc ……
Strategy is:
to TRIGGER
on displaced trackswith SILICON VERTEX
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The SiliconVertexTrigger
d0
XFT
COT
hits
d0, Φ0, Pt
SVThits
Detector
Raw Data
Level 1
storage
pipeline:
42 clock
cycles
Level 1Trigger
L1Accept
Level 2Trigger
L2Accept
L3 Farm
Level 1•7.6 MHz SynchronousPipeline•5544 ns Latency•50 KHz accept rate
Level 2• Asynchronous 2 Stage Pipeline•20 µs Latency•300 Hz accept rate
7.6 MHz Crossing rate
132 ns clock
20µs !!!
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SVT performances
•Level 2: Silicon Vertex Trigger
– Impact Parameter resolution:~ 50 µm
(35µm beam size + 35µm SVT)
•Increase physics sensitivity of the Run II CDF:– CDF is a “Charm Factory”•> Millions of D’s per 100 pb-1
– Collect Hadronic B/D sample:•No Lepton required in final state•Bs physics (mixing in Dsπ)
Select ON-LINE displaced verticeswith IP parameter cut on tracks
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HF Triggers and data samples
Displaced trk+ lepton (e, µ)IP(trk) > 120µm
Pt(lepton) > 4 GeV
Semileptonic modes
2-Track Trig.Pt(trk) > 2 GeV
IP(trk) > 100 µm
fully hadronic modes
Di-Muon (J/ψ)Pt(µ) > 1.5 GeV
J/ψ modes down to low Pt(J/ψ) (~ 0 GeV)
Larger yield: lower Pt threshold wrt RunI: e (µ): 8 (2.2) 4 (1.5) GeV
Better S/N trigger on long-lived decays (displaced tracks)
-Quarkonia, rare decays
- CP violation
- Masses, lifetimes
- High statistics lifet.
- Sample for tagging studies
-BS mixing
-Hadronic charm & beauty
- CP asymmetries
…{Thanks to SVT trigger}“a Classic”
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Charming Physics analysis
I will show status and prospects ofa few selected on going analysis.
•Studies of QCD– Onium Production (J/ψ)
• Cross section• Polarization
– Charm production• Cross section• D** Production
•Rare Decays– D µµ, …
•Masses and Lifetime– D0, D+, Ds, Λc, …
•CKM studies & New physics–Mixing
• In D0 with lifetime diff. ∆Γ• In D0 time dependent analysis
–Direct CP violation• D0 KK,ππ
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(1) Dimuon J/ψ µµ dataset
• (1) Dimuon dataset:– 2 central muons pT > 1.5 GeV• Run I : > 2 GeV
–Trigger on J/ψ µµ decays• Collect ~ 70 pb-1
– ~ 0.5M J/ψ µµ signals
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(2) Lepton + displaced track dataset
•(2) Lepton + Track– 1 muon/electron pT> 4 GeV– 1 other track with• pT > 2 GeV, SVT IP > 120 µm
–M(l-Track) < 5 GeV•Collect ~70 pb-1 of data– ~ 0.5M B lX signal
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•(3) Two Track Trigger– 2 Tracks with •pT>2GeV•SVT IP > 120 µm
– pT1+pT2 > 5.5 GeV•Collect ~70 pb-1 of Data– ~ 0.5M D0 Kπ signal
(3) Two displaced tracks dataset
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Run I J/ψ Production Cross Section•Run I Measurement:– LO calculation: 1/ 100 x CDF
•Non-relativistic QCD– Include color octet states– Theory doesn’t predict the absolute normalization•Fitting the CDF data
•Prediction– J/ψ production is dominated by the color octet mechanism– J/ψ is polarized at high pT
•Some discrepancy (~ 2σ) between the Run I polarization measurement and NRQCD– waiting Run II measurement
CDF Run I
Tran
sver
sepo
lariz
ed
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J/ψ µµ Cross Section (Run II)•1.5x2 = 3 < M(J/ψ) – 2xM(µ)– Trigger on stopped J/ψ
•We can measure cross section down to pT = 0– σ(pp J/ψ; pT>0; |η|<0.6)
•Dimuon Mass distribution for the lowest pT bin (0-250 MeV)
Background is subtracted
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J/ψ µµ Cross Section (Run II)
σ(pp J/ψ; pT>0; |η|<0.6)XBR = 240 +-1 (stat) +35 -28 (syst) nb
{ RUN I: σ(pp J/ψ; pT>5GeV/c; |η|<0.6)XBR = 17.4 +-0.1 (stat) +2.6 –2.8 (syst) nb }
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Production Cross Section: Charm•Run I Measurement:– D* D0π: D0 µνKX•muon with pT > 8 GeV
–Slightly higher than theory expectation
•Run II– Use SVT sample Pt as low as 5.5 GeV– Early Run II data (~6 pb-1)•enough statistics for counting experiment, D0, D+, D*+, Ds
CDF Run I (unpublished)
20
Production Cross Section: Charm
Major issues:bb fraction of the sampleTrigger acceptance (MC):
•With O(10 pb-1) X-sec D0/D*/D±/Ds/Λc
In the near future ccbar correlationstudies will be possible
-
FIRST TIME at Collider !
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Production Cross Section: Charm•For measuring the Charm cross section, we need to separate direct Dand B D decays– Use Impact parameter of D– D meson from B decay has larger impact parameter
•Direct Charm fraction– D0: 86.6 ± 0.4 ± 3.5 %– D*+: 88.1 ± 1.1 ± 3.9 %– D+: 89.1 ± 0.4 ± 2.8 %– Ds
+: 77.3 ± 3.8 ± 2.1 %
BD
K
π
X
P.V.
B D0: 16.4-23.1%
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Production Cross Section: Charm, results:σi = ½Ni* fD,i / (L * εi * BRi)
(f = prompt frac.;L = lumi.; ε=eff.;) based on 5.7 pb-1 of SVT data (|y|<1):
• σ(D0, pT >= 5.5 GeV) = 13.3±0.2±1.5µb • σ(D*+, pT >= 6.0GeV) = 5.2±0.1±0.8µb • σ(D+, pT >= 6.0 GeV) = 4.3±0.1±0.7µb • σ(Ds, pT >= 8.0 GeV) = 0.75±0.05±0.22µb
Comparison with NLO calculationsfrom M. Cacciari and P. Nason by private communication calculations of the direct D meson cross-section. These calulations have not yet been published, but they follow the same prescription (called FONNL) as what was used for their paper 'IS THERE A SIGNIFICANT EXCESS IN BOTTOM HADROPRODUCTION AT THE TEVATRON?' (Phys.Rev.Lett.89:122003,2002, hep-ph/0204025)
… with more data cc production processes and angular correlations possible
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Mass: ∆ Μ(Ds – D+ )•Ds, D+ φπ ; φ KK– Same final state, almost identical kinematics– 10 pb-1 of two track trigger
•Measure mass difference– Systematics are reduced:
∆M
•Result: M(Ds) – M(D+) =
99.41 + 0.38 + 0.21 MeV/c2
(PDG: 99.2+0.5 MeV/c2)
FIRST CDF RUN II PAPER !
High precision measurementallows stringent test of HQ effective theories
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After correction for relative acceptance of SVT trigger & reconstruction for the 3 decays⇓
Kπ mass KK mass
56320±490 5670±180 2020±110
Γ(D→KK)/Γ(D→Kπ) = 11.17 ± 0.48(stat) ± 0.98 (syst) %Γ(D→π π )/Γ(D→Kπ) = 3.37 ± 0.20(stat) ± 0.16(syst) %
WORLD BEST MEASURES: CLEO2 (PDG 2002)
•Γ(D→KK)/Γ(D→Kπ) = 10.40 ± 0.33 ± 0.27 %•Γ(D→π π )/Γ(D→Kπ) = 3.51 ± 0.16 ± 0.17 %
Already competitive measurements in Charm withThe first statistic collected with the new SVT trigger.
9.6 pb-1 SVTdata
NOW : huge sample of D mesons attempt for D0 mixing & CPV in D decays
ππ mass
Cabibbo Suppressed D0 Decays (@ICHEP 2002)
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D* tagging•Very high purity D0 signal using “D* tag” technique
–D*+ D0π: Q =39 MeV–M(D*)–M(D0):
• σ(MD) ~ 10 MeV• σ(∆M) ~ 0.6 MeV
– 20% of the D0 : D* taggedFrom 0.451M D0 78160 D* tagged D0
•Eliminate the “reflection” background (D0 Kπ and πK)•No PID applied yet•Initial flavor of D0 is known– D*+ D0 + π+ / D*- D0 + π-
– The best place to study D0 mixingand direct CP violation
σ~0.6 MeV W/o D* tag
with D* tag
NOW: 65 pb-1:
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Cabibbo Suppressed D0 Decays
•Summer 2002 (10 pb-1): no D* taggingBr(D0 KK)/Br(D0 Kπ)=(11.17+0.48+0.98)%Br(D0 ππ)/Br(D0 Kπ) = (3.37+0.20+0.16)%– main systematics: background subtraction
•Spring 2003 (65 pb-1): with D* tagging– Repeat the relative BR measurement
with δ(rel.BR) ≈ 1 %(without D*: ≈ 10% for KK)
… direct CP asymmetry in ππ and KK decay
cu u
du
d
W
cu u
u
sW
sVus
Vcd
N = 8320+- 140
N = 3697+- 69
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• Can be observed through an ACP between D f and its CP conjugate
• Need two weak amplitudes to interfere (Cabibbo allowed decays tree amp.only)possible in Single Cabibbo suppressed (tree + penguin)• ACP expected to be <O(10-3) in Cabibbo suppressed modes like KK and ππ
CP violation in D0 decays:
)(2)(2
)()()()(
21*21
22
21
21*21
δδδδ
−++
−=
Γ+ΓΓ−Γ
=cosAReAAA
sinAImAffffACPΓ( D f) ≠ Γ( D f)
_ -A1eiδ1
A2eiδ2 A*2eiδ2
A*1eiδ1
Best single measurement at present comes from CLEO 2:ACP(KK) = (0.0 +- 2.2 +- 0.8)% with ~ 3000 KKACP(ππ)= (1.9 +- 3.2 +- 0.8)% with ~ 1100 ππ
With 65 pb-1 we expect to upgrade soon (summer 2003) previousmeasurements:δACP(KK,ππ)stat < 2% and δACP(KK,ππ)syst < 1%
IFAE 25-aprile 2003, Lecce Sandro De Cecco, INFN Roma 1 29
D0 mixing•D mixing in the SM ~ O(10-3)
•New Physics can enhance it
•For CDF:- High statistics
- excellent S/B (purities ~ 95%) (with D*)
- High mass and proper time resolution
c
ud,s
u
cd,s
W-
W+
Vcd,cs Vud,us
V*ud,us V*cd,cs
D0⟩ D0⟩_ __
Two main way to study it:– lifetime ratio: y = ∆Γ/2Γ = τmix/ τCP - 1where CP mixed final state can be Kπ, and CP eigenstates can be KKand/or ππ
– Measuring wrong sign decays in D0 Kπ and D0 Klν: (x2+y2)time-dependent analysis to deconvolve DCS decays
…News soon from CDF
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Rare Decay Search: D0 µµ•BR (D0 µµ )
– SM expectation : ~ 10-13
– Possible enhancement by new physics• R-parity violating SUSY: ~ 10-6
– Current best limit: < 4.1x10-6 (90% CL) ( E777, Beatrice )
•Analysis–Use D* tagged D0
–Use D0 ππ signal for normalization mode•Almost identical kinematics
–Br(D0 ππ) ~ 1.5x10-3
•300 D0 ππ ~1 D0 µµ signal (Br=4.1x10-6)–Major backgrounds: D0 ππ, and muon fake rate from D0 Κπ
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Rare Decay Search: D0 µµ
Muon detector fiducial
•Expected background after the optimized selection cuts:– 1.7+0.7 events•Fake: 0.22+0.02•Combinatorial: 1.5+0.7
• 0 events in search window
•New best limitBR < 2.4 x 10-6 at 90% CL
{ < 4.1x10-6 (90% CL) ( Beatrice ) }
With much higher integrated luminosity:further background study D0 eµ, ee and D+ µµπ
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Conclusions: a lot of Charm to come from CDF
• Run II CDF collected ~100 pb-1 of data – ~70 pb-1 for B/Charm physics in the SVT trigger
• CDF is an high statistics Charm experiment: O(107)D0 in 2fb-1
•J/Ψ production x-sec from Pt=0•First time D meson production x-sec measured at collider.•World best Ds-D+ Mass difference measurement (first CDF paper is on Charm)•In D0 ACP in Single Cabibbo suppressed modes very promisingand D0 mixing
CDF will in principle, perform competitive measurements before CLEO-C
New limit (x 2 better) on rare D0 µµ decay BR.
And (not included in this talk) other charmed particles studies D**.
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CDF Trigger System Overview• Crossing: 396 ns: 2.5 MHz
• Level 1: hardware– Calorimeter, Muon, Track– 15kHz (reduction ~x200)
• Level 2: hardware + CPU– Cal cluster, Silicon track – 300 Hz (reduction ~x5)
• Level 3: Linux PC farm– ~ Offline quantities– 50 Hz (reduction ~ x6)
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•Statistical uncertainty for tagging efficiency–A typical tagging: ε=0.1,D=0.4,εD2=1.6%–1000 events: εD2 =1.6+0.7% (44%)–100K events: εD2=1.60+0.07% (4.4%)
•We can’t study/optimize the flavor tagging with ~O(1000) events of the B signal events– B J/ψK: ~ 1000 events/100pb-1
– B Dπ: ~ 500 events/100pb-1
•Our solution: Use Semileptonic B decays in the lepton + track dataset– ~200K semileptonic B signal events– High B purity– Lepton Charge = Decay flavor of B
Flavor Tagging
No charm contamination
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Rare Decay Search: D0 µµ•Background (1)–D0 ππ with both π µ fake–Nbg = N(ππ) x prob(fake) 2
– fake prob. Is measured in D0 Kπ signal
•Background (2)–Combinatorial background–Linear extrapolation of the high mass sideband events
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Hadronic B signals•Two track trigger data (65 pb-1)•Reconstruct hadronic B decays– B0 D+π (D+ Kππ): 413+40– B+ J/ψK(J/ψ ll): 311+25
Normalization mode forthe other decays
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Hadronic Bs and Λb Decays•Bs Ds π– Golden mode for Bs mixing
•65 pb-1 of two track trigger data– Bs Dsπ(Ds φπ) : 40+10 events– Bs Ds*π (Ds φπ) : 65+20 events
•More channels to be added– Bs Ds πππ– Ds K*K, K0
sK, πππ•Further optimization of trigger strategy to obtain more signals•Estimate the sensitivity for Bs mixing–Flavor tagging, time resolution…
• Λb Λcπ (Λc pKπ)– ~ 40 events in 65 pb-1
•More channels to be added– Λb Λcπππ, pD0π– Λc Λπππ
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B h+h-
•B h+h- signal in the two track trigger sample – 301+27 signal events– Good S/N ~ 1
•This signal is combination of four decay channels– Tree (Br~5x10-6)•B0 ππ : Bs Kπ
– Penguin (Br ~1.5x10-5)•B0 Kπ : Bs KK
•We can separate these decays– Decay kinematics– COT dE/dx
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B h+h- from 2-Track Trigger
Experimental challenge:
Disentangle 4 channels:
kinematics + dE/dx
Final resolution expected is
σAcp~O(15%)
Bd ππ Bd Kπ
Bs KKBs KπdE/dx [ns]
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B h+h-
•Kinematical Separation– α = (1 – p1/p2) q1
– M(ππ)
•dE/dx Separation
First results expected soon- Br(B0,Bs->KK,Kπ,ππ)- Direct CP asymmetry in B Kπ
~ 15% resolution for Acp
M(ππ) is Lorentz invariantIf it’s really B ππ
M(ππ) is not LorentzInvariant for B Kπ
Simulation
Simulation