Charm physics in CDF - INFN Lecce web · Charm physics in CDF Sandro De Cecco, INFN Roma1 for the...

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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


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


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


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


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


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


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


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 !!!


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


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”


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


(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


(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


•(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


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


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


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 }


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 !


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%


Production Cross Section: Charm


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


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


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)


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:


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


• 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%


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


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


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


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**.


…Backup slides


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)


•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


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


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


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


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


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]


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

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