charm production cross section and charm physics at the tevatron
DESCRIPTION
Charm production cross section and charm physics at the Tevatron. Sandro De Cecco INFN Roma 1 “Rencontres de physique du Vietnam”, Hanoi 07 aout 2004. Outline. The Tevatron collider CDF detector and triggers. Highlights on hadronic heavy flavours production. - PowerPoint PPT PresentationTRANSCRIPT
"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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 2
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 3
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)
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 4
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
0
1
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 5
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 6
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 7
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 8
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 9
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)
+
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 10
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:
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 11
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:
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 12
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 13
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):
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 14
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:
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 15
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 16
• 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 !!!
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 17
D0 Cabibbo suppressed 2 body decays
D0
D0
KK
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 18
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 19
•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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 20
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 21
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…
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 22
BACKUP slidesBACKUP slides
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 23
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 24
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 25
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)
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 26
CDF data tacking performanceData-Taking Efficiency Integrated Luminosity
Detector efficiency ~85-90%
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 27
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)
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 28
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 29
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
"Rencontres de Physique du Vietnam" 7/8/2004 Sandro De Cecco - INFN Roma 1 30
X(3872) physics: the B fraction