charm production cross section and charm physics at the tevatron

"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 1

Sandro De Cecco

INFN Roma 1

“Rencontres de physique du Vietnam”, Hanoi 07 aout 2004

Charm production cross section and charm physics at the Tevatron


Outline

• The Tevatron collider

• CDF detector and triggers.

• Highlights on hadronic heavy flavours production.

• Measurement of prompt charm production cross section.

• Search for direct ACP in D0 Cabibbo suppressed decays.

• Search for FCNC decay D0.

• Conclusions and perspectives

! Disclaimer: results come from CDF only; D0 is going to publish charm physics results soon


The Tevatron pp colliderSuperconducting proton-synchrotron: 36p36p bunches, crossing each 396 ns

at √s = 1.96 TeV

Luminosity……………………………..: record peak L = 1 1032 cm-2s-1 (as of July 04)

# interactions / bunch-crossing……...: < N > = 1.5 (@ 5 x 1031 cm-2s-1)

Luminous region size………………...: 30 cm (beam axis) x 30 m (transverse)


Tevatron plans• RECYCLER had a first successful test• Plans beyond FY 05 depends on

Recycler ring and electron cooling performances

• Will see after aug./nov.04 shutdown

Year Base plan luminosity/yr (fb-1)

Design plan

Luminosity/yr (fb-1)

FY02 0.08 0.08

FY03 0.20 0.22

FY04 0.31 0.38

FY05 0.39 0.67

FY06 0.50 0.89

FY07 0.63 1.53

FY08 1.14 2.37

FY09 1.16 2.42

Total 4.41 8.56

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2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9 10

End FY

fb-1

Base plan

Design plan


Tevatron FY04 performance

• Tevatron is working very well this year (Design plan):

• Initial luminosity (may 04) = 7.2 X 1031 sec-1 cm-2 (now 1.x1032)

• Weekly Integrated luminosity ~ 10 pb-1/w • ~350 pb-1 on tape, 100-200 pb-1 used for analysis so far

0

50

100

150

200

250

300

0 30 60 90 120 150 180 210 240 270 300 330 360

Days Since October 1

Inte

grat

ed L

umin

osity

(pb

-1)

FY04

FY03

FY02

FY04 Design

FY04 Base

1st May 2004

1st Jan. 2004

L (

pb

-1)

2003

2002

FY04 D

esig

n

FY04 Base


The upgraded detectors

•New tracking: silicon and fibers in magnetic field•Upgraded muon system•Upgraded DAQ/trigger (displaced track soon)

•New silicon detector new drift chamber•Upgraded calorimeter, •Upgraded DAQ/trigger, displaced-track trigger•New TOF PID system


HF Physics at pp collider

• Huge cross-section: 50-100 b

• All B/D species produced:

Bu,Bd,Bs,Bc,B*,b, b…

D0,D,D*,Ds,D**,c, c…

BUT: (bb,cc) << (pp) (~65 mb) HF events have to be selected with specific triggersTrigger requirements: large bandwidth, background suppression, small dead-time

Flavor Creation (annihilation)

q b

q b

Flavor Creation (gluon fusion)

bg

g b

Flavor Excitationq q

b

g

b

Gluon Splitting

bg

g g

b

bb/cc production mechanics in hadron collider:

LONLO


B production x-section, Run I

B cross section measured from Run Iat Tevatron is consistently higher than NLO QCD

Theoretical development still ongoing.

Ex: fragmentation effect …….

Experimental Approaches:Experimental Approaches:

More cross section measurement

-- energy at 1.96TeV

-- lower pT(B)

Study bb correlation

Measure CHARM production cross section


Heavy Flavours triggers at CDF II

Displaced track + lepton (e, )I.P.(trk) > 120m

Pt(lepton) > 4 GeV

Semileptonic modes

2-Displaced tracks

PT(trk) > 2 GeV

pT > 5.5 GeV

I.P.(trk) > 120(100) m

fully hadronic modes

Di-Muon (J/)

Pt() > 1.5 GeV

J/ modes down to low Pt(J/)~0 (Run II)

Rare decays

With the New Silicon Vertex Trigger

primary vertexsecondary vertex

Impact Parameter ( ~100m)

~ 1 mm

b,c decays

Conventional at colliders (Run I)

+


SiliconVertexTracker: the hadronic B trigger

≈ 47 um ≈ 35 um + 30 um

SVT resolution Beam spot size

Online Impact parameterAvailable at Level 2 trigger (20µs latency)Trigger decision

convolution of transverse size of the beam spot with the impact parameter resolution of the SVT:

Impact parameter distribution

( Compare to offline ~ 46 m )

d

beam spot

COT track ( 2 parameters) 5 SVX coordinates

Impact Parameter (transverse projection)

Collect large amount of fullyreconstructed B,D hadrons:


Prompt Charm Meson X-SectionWith early CDF data:With early CDF data: 5.8 5.80.3pb0.3pb-1-1

• Measure prompt charm meson

production cross section

• Data collected by SVT trigger

from 2/2002-3/2002

• Measurement not statistics limited

Large and clean signals:


Need to separate direct D and BD decay

• Prompt D point back to collision point

I.P.= 0

• Secondary D does not point back to PV

I.P. 0

Separating prompt from secondary Charm

Direct Charm Meson Fractions:Direct Charm Meson Fractions:

DD00: f: fDD=86.4±0.4±3.5=86.4±0.4±3.5%%

D*D*++: : ffDD=88.1±1.1±3.9%=88.1±1.1±3.9%

DD++: f: fDD=89.1±0.4±2.8%=89.1±0.4±2.8%

DD++ss: f: fDD=77.3±3.8±2.1%=77.3±3.8±2.1%

BD tail

Detector I.P. resolution shape measured

from data in K0s sample.

Most of reconstructed charm mesons are direct

Separate prompt and secondary

charm based on their transverse

impact parameter distribution.

Prompt D Secondary D from B

Promptpeak


Prompt Charm Meson X-Sections

Integrated cross sections:Integrated cross sections:

bpD

bpD

bpD

bpD

Ts

T

T

T

22.005.075.0)1|Y|GeV,8,(

7.01.03.4)1|Y|GeV,6,(

8.01.02.5)1|Y|GeV,6,*(

5.12.03.13)1|Y|5.5GeV,,( 0

bpB T 6.06.3)1|Y|6GeV,,(

Determine trigger and reconstruction efficiency from data and MC

Measure charm meson pT spectrum

CDF prompt charm cross section result published in PRL hep-ex/0307080

As a comparison the beauty meson x-sec (CDF Run I):


Differential Charm Meson X-Section

Calculation from M. Cacciari and P. Nason:

Resummed perturbative QCD (FONLL)

JHEP 0309,006 (2003)

CTEQ6M PDF

Mc=1.5GeV,

Fragmentation: ALEPH measurement

Renorm. and fact. Scale: mT=(mc2+pT

2)1/2

Theory uncertainty: scale factor 0.5-2.0

PT dependent x-sections:

Theory prediction:


Comparison with Theory

Ratio of measured to predicted cross sections:

• Measured cross section is

~1.5 factor higher: similar to B

I CDF XBpp PRL89:122003,2002

• NLO calculations compatible within errors

• pT shape is consistent for D mesons


• The huge amount data collected by the Two Track Trigger have been used for this analysis

Relative branching ratios:(D0→K+K-) / (D0→K) (D0→+-) / (D0→K)

(D0→) / (D0→)~2.8 (SM)

Direct CP asymmetries wheref is CP eigenstate (ex. K+K-,+-):

• Candidates selected as: D →D0 unbiased tag of the D0 flavor)

D0→h+h- direct CP Asymmetries and Decay Rate ratios

)(0)()(

)()(00

00

SMfDfD

fDfDACP

Normalization mode D0→K~180000 D*+/-→ D0 !!!


D0 Cabibbo suppressed 2 body decays

D0

D0

KK


CP Asymmetries and Decay Rate ratios

Very important to understand the asymmetry of the CDF detectorat per mille level !!!

Results are computed after correction for:•intrinsic charge asymmetry•relative acceptance between the D0 modes

Relative BR’s CDF FOCUS

(D0→KK) / (D0→K) (9.92 0.11 0.12)% (9.93 0.14 0.14)%

(D0→) / (D0→K) (3.594 0.054 0.040)% (3.53 0.12 0.06)%

(D0→KK) / (D0→) (2.760 0.040 0.034)% (2.81 0.10 0.06)%

Direct CP asymmetries CDF CLEO II

ACP (D0→KK) (2.0 1.2 (stat.) 0.6 (syst.))% (0.0 2.2 (stat.) 0.8 (syst.))%

ACP(D0→) (1.0 1.3 (stat.) 0.6 (syst.))% (1.9 3.2 (stat.) 0.8 (syst.))%

Submitted to PRL august 04


•SM expectation BR~ 3∙10-13

•Best limit: <4.1∙10-6 (90% CL) (Beatrice/WA92, E771)

•BR significantly enhanced with New Physics (e.g. R-Parity Violation Susy: ~3.5*10-6)

Experimental strategy:

•Events from two-track trigger using first 69pb-1 of data

•To cancel acceptance effects normalize to D0→

•Only relative efficiency needed

Search for FCNC D0→

)()(

)(

)(

)()( %900

%90

BR

N

NDBR

upperCL

CL


FCNC D0→: Results

BR(D0→)<2.4x10-6 (@90% CL)

Factor 2 improvement over best limit

M with D* tag and 2 muons

1.7 expected events

0 events observed

Next: use full muon coverage and 2-3 times more data (~1year) also look at D+→D+→KD0→e, Ds

Combinatorial:1.5+-0.7 eventsFakes: 0.22+-0.02 events


Conclusions

• Prompt charm cross-section has been measured for the first time at collider useful input to QCD calculations for HF production and hadronization models.

•Hadronic D0 decays relative BR’s measured with high accuracy

•Search for direct CP asymmetries in Cabibbo suppressed D0 decays is world best single measurement.

• CDF will soon be sensitive to beyond SM theories with rare D decays

•Charm yields are competitive to B-factories and physics program complementary to CLEO-C.

The charming side of the Tevatron…


BACKUP slidesBACKUP slides


CDF II tracking system

LAYER 00: 1 layer of radiation-hard silicon at very small radius (1.5 cm) (achievable: 45 fs proper time resolution in Bs Ds )

COTCOT: large radius (1.4 m) Drift chamber

• 96 layers, ~100ns drift time • Precise PT above 400 MeV/c

• Precise 3D tracking in ||<1

(1/PT) ~ 0.1%GeV –1; (hit)~150m

• dE/dx info provides >1 sigma K/ separation above 2 GeV

SVX-II + ISL: 6 (7) layers of double-side silicon (3cm < R < 30cm)• Standalone 3D tracking up to ||= 2• Very good I.P. resolution: ~30m (~20 m with Layer00)

TOF: 100ps resolution, 2 sigma K/ separation for tracks below 1.6 GeV/c (significant improvement of Bs flavor tag effectiveness) - charge)

TIME OF FLIGHT

CDF Roma


CDF II particle ID handles

TOF PID

dE/dx PID

•Specific Ionization of charged particles (dE/dx) measurement in the COT gas chamber.

•Time of flight measurement with the new scintillator bars detector (TOF) at R=1.4m with a TOF = 100 ps

p

Total K/ separation power of at least 2 for momentum up to 1.6 GeV/c with TOF

And at least 1 for momentum up to 4-5 GeV/c with TOF + dE/dx


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)


CDF data tacking performanceData-Taking Efficiency Integrated Luminosity

Detector efficiency ~85-90%


Charge Asymmetry in the CDF Detector

Study asymmetry using unbiased tracks and correct

NN

NNpA tQ )(

)()(

)()(0

0

fDfD

fDfDAcorr

Residual asymmetry syst.error

Q

Q

A

A

1

1

(Expect no CP asymmetry)

(same track quality cutsgeneric track sample)


Normalization Mode: D0→

Search window: 1.84<m<1.884 GeV

Selection: intersect D0 with soft 0.144<m(D*)-m(D0)<0.147Optimized cuts: Lxy<0.45 cm, |dxy|<0.015cm, Angle cut between track and muon stub, Track quality cuts

N() = 137153

Relative efficiency from Monte Carlo: ( muon reconstructionand decay in flight efficiency)

04.014.1)(

)(

K


D0→ Background

Fakes from misidentification:N(D0→) in mass window times (misid probability)2:

Estimate combinatoricsfrom high mass sidebandwhere both tracks are muons

Fakes: 0.220.02 eventsCombinatorics:1.50.7 events

From D* taggedD0→

misid probability


X(3872) physics: the B fraction

charm production cross section and charm physics at the tevatron

Documents

cecco infn roma 1chart10

ceccoinfn roma

cross section measurement

cc b production xsection

ib cross section

hadronic b triggers

run iat tevatron

tevatron plansrecycler