future perspectives for charm physics at hadron machines

DIF 06 workshop, Frascati 01-03-2006 Sandro De Cecco - FNAL / INFN Roma 1

Future Perspectives for Future Perspectives for Charm PhysicsCharm Physics

at Hadron Machinesat Hadron Machines

Sandro De CeccoSandro De Cecco

FNAL-PPD/CDF and INFN Roma 1FNAL-PPD/CDF and INFN Roma 1


Outline:Outline:

• Introduction on Heavy Flavour physics at hadron colliders

• Charm input to CP violation picture– D0 mixing– Direct CPV in Charm decays– FCNC decays

• The Experimental “Charm” of Hadron Colliders

• Charm production, charm as a probe for QCD– Heavy quarks hadro-production in pp and NN interactions– DD correlations – Charmonium– Excited states, c-barions


Heavy-Quark production in hadron collisionsHeavy-Quark production in hadron collisions

Leading Order and Next to Leading Order

Gluon splitting

Flavor excitation

Flavor creation

g

g

gg

Q

Q

radiative corrections

B/D-Hadrons and/or b/c-jets are the observables rather than b/c-quark

Factorize physical observable into a calculable part and a non-calculable but universal piece

DF

cbpd

cXbqgggqqd

DBpd

DXBppd DBcbpp

TT

//

/

///

/

/

NLO QCD

Observed Proton structure

Fragmentation


Fragmentation functions Fragmentation functions DDb/c b/c B/DB/D

''' dxxxx DDDpertnonpertmeas

Perturbative part: probability to find a hadron with fraction x’ of original parton momentum

Hadronization: non perturbative QCD, need models

Charm will have softer P-spectrum than b.


Charm and beauty at colliderCharm and beauty at collider

• Large cross section • Select triggering on:

– Semileptonic decays

• Trigger , e

– Hadronic decays (CDF-SVT)• One or more displaced tracks

i.e. large impact parameter√s (TeV)

0.001 0.01 0.1 1.0 10 102

1mb

1b

1nb

1pb

SppSTevatron

LHC(pp→X)(-)

(bb)

• Total inelastic x-sec ~100 mb = 103-104 x (cc/bb)

• x-sec is 105-106 larger than at e+e-

• Open spectrum of mesons and barions:•Bu , Bd , Bs , Bc , b , b…•D+, D0, Ds , c , c , c…


Selecting heavy flavour decaysSelecting heavy flavour decaysCLEO

CDF

To select charm and beautyIn hadronic environment:

High resolution tracking detector is mandatory

Only way to access hadronicdecays is to trigger on tracks

Primary Vertex

Secondary Vertex

Impact Parameter ( ~100m)

Lxy ~ 1 mm

B/D decay

Example: the CDF Secondary Vertex Trigger SVT

•Online (L2) selection of displaced tracks

based on Silicon detector hits.

D0 K


Charm program at hadronic machinesCharm program at hadronic machines

Tev

atro

nT

evat

ron

LH

LHCC

• First experiment doing high precision charm physics at collider, collecting huge yields in hadronic D modes• Many results already (in this talk) and more to come

• Nice charm physics program mainly on rare FCNC and LFV rare decays ( see Frank Lenher talk )• Relies on the presence of a muons to trigger charm

• Expect to be able to select clean charm signals thanks to fine tracking and PID• Will measure cc x-sections in pp, pN and NN collisions

• Thinking about having a dedicated D* charm trigger selecting huge and clean samples of hadronic D modes• Will definitely take over what CDF started in the search for CPV and mixing in charm


Open cc ProductionOpen cc Production


Prompt Charm Meson X-SectionPrompt Charm Meson X-SectionWith very early CDF data:With very 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 is 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 CharmSeparating 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 mesons are prompt

Separate prompt and secondary

charm based on their transverse

impact parameter distribution.

Prompt D Secondary D from B

Promptpeak

D impact parameter


Prompt Charm Meson X-Sections 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 Differential Charm Meson X-Section

Calculation from M. Cacciari and P.Nason:

Resummed perturbative QCD (FONLL)

JHEP 0309,006 (2003)

PT d

epen

den

t x-

sec

tio

ns:

Theory prediction:

D0 DsD+D*+

Da

ta/

Th

eory

PRL89:122003,2002

I CDF XBpp

(as reference)

Measured x-section is ~1.5 factor higher: similar to B+


Open cc production future studies:Open cc production future studies:

• Studying cc correlations through angular difference .•Can separate contributions from different production mechanisms:

-Flavour creation-Flavour Excitation-Gluon splitting

• Issues are:- Low efficiency to have opposite charm in the acceptance- Backgrounds at low from BDDX decays.

• CDF already has clean samples of D*-D0, D*-D+ and D*Ds consisting of ~ few 100’s / few 1000’s events depending on the modes.•Expect to have correlation results based on 1 fb-1 of Luminosity

BDD BBbar


D mesons quenching reducedRatio D/hadrons (or D/0) enhanced and sensitive to medium properties

Charm as a probe in Pb-Pb collisionsCharm as a probe in Pb-Pb collisions

•Heavy quarks with momenta < 20–30 GeV/c v << c

• Gluon radiation is suppressed at angles < mQ/E

•“dead-cone” effect–Due to destructive interference (inside cone gluon with v=c would violate causality)

–Contributes to the harder fragmentation of heavy quarks and implies lower energy loss for heavy quarks relative to light quarks

Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202].

A.Dainese nucl-ex/0311004

( from C. Fabjan )


Combine ALICE tracking + secondary vertex finding capabilities (sd0~60mm@1GeV/c pT) + large acceptance PID to detect processes as D0K-+ ~1 in acceptance / central event ~0.001/central event accepted after rec. and all cuts

HadronicHadronic charm selectioncharm selection

S/B+S ~ 37

S/B+S ~ 8for 1<pT<2 GeV/c(~12 if K ID required)

significance vs pT

Results for 107 PbPb ev. (~ 1/2 a run)


DD0 0 Cross section measurementCross section measurement

pp, 14 TeV

mc

scalesPDFs

down ~ 0!down to 1 GeV/c!

Pb-Pb


Charmonium ProductionCharmonium Production


Inclusive J/Inclusive J/ productionproduction

CDF: Lower pT trigger threshold for : pT() ≥ 1.5 GeV J/ acceptance down to pT=0

D0: Larger acceptance for

0<pT<0.25 GeV

CDF: 39.7 pbCDF: 39.7 pb-1-1D0: 4.8 pbD0: 4.8 pb-1-1

bsyststatJyXJpp )()(02.008.4)6.0|)/(|,/( 60.048.0

total J/ production cross section at Tevatron is:


• Run I: b cross-section ~ 3x old NLO QCD

• Theoretical approaches: new physics, Next-to-Leading-log resummations, non perturbative fragmentation function from LEP, new factorization schemes…

• Experimentally: unbinned maximum likelihood fit to the flight path of the J/ in the R- plane to extract the b fraction

Inclusive bInclusive b cross sectioncross section

Run II: Bottom Quark Production cross-section:

Good agreement PRD 71, 032001 (2005)


+ b/c + b/c xx-section-section

• Probes heavy flavor content of the proton and its PDF (also with Z0)• Experimental approach:

• One isolated and High Et (> 25 GeV)• One jet with a secondary vertex (b/c “like” jet)

• Fit on the secondary vertex mass distribution of the tagged jets to separate b, c and light quarks

(b + ) = 40.6 +/- 19.5 (stat.) + 7.4 -7.8 (sys.) pb (c + ) = 486.2 +/- 152.9 (stat.) + 86.5 -90.9 (sys.) pb

+ c + b


Other charm statesOther charm states


excited D** statesexcited D** states

•Plenty of D**: Dj narrow, wide, radial, orbital, resonant, nonresonant…

•Narrow states are the only widely observed objects so far…

•HQET predicts splitting of states vs mQ

•The large statistics of charm at CDF gives access to D**


D** PropertiesD** Properties

D1,2 D*+-

D*+D0+

D0K-+

D2 D+-

D+K+--

•Huge sample of narrow D** resonances

•Competitive in measuring prompt D** properties!

•… and secondary from B’s

Prompt D1,2

Secondary D**


D** resultsD** results

M(D1)=2421.7 0.7 0.6 MeV

(D1)=20.0 1.7 1.3 MeV

M(D2)=2463.3 0.6 0.8 MeV

(D2)= 49.2 ±2.3 ±1.3 MeV

High precision masses and widths from prompt D1,2

Non-leptonic mass in BlXc where Xc is D** mass moments analysis

mean r.m.s

Probe HQET and contraints for CKM element Vcb


……charm et al. …charm et al. …

c-Barions decayingin fully hadronic modesaccessibles with SVT trigger

and … X(3872) J/

fraction from B: (16.0 ±4.9 ±1.0)% M() spectrum


Charm Rare DecaysCharm Rare Decays


Experimental strategy CDF:

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

•To cancel acceptance effects normalize to D0→

Search for FCNC Search for FCNC DD00→→

•SM expectation BR~ 3∙10-13

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

•Enhanced in N.P. (R-Parity Violation Susy: ~3.5*10-6)

BR(D0→)<2.4x10-6 at 90% CL

Result:

Comment: muon fake rate will set limit (~10-6)

Next: use full muon coverage, add statistics, explore electron modes (less coverage but lower fake rate)

also look at D+→D+→KD0→e and Ds

… see Frank Lenher talk in this workshop for details


CP Violation and Mixing in neutral DCP Violation and Mixing in neutral D


•Search for direct CP asymmetries where f is CP eigenstate (ex. K+K-,+-):

…in single Cabibbo suppressed modes (KK)Almost null in Cabibbo allowed (K) Use D0K as normalization mode

• Data collected by the SVT trigger with 123 pb-1 of int. LuminosityRelative branching ratios:

(D0→K+K-) / (D0→K) (D0→+-) / (D0→K)

(D0→) / (D0→)~2.8 (SM)

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

DD00→h→h++hh-- direct direct CP Asymmetries and BR’sCP Asymmetries and BR’s

)(10)()(

)()( 300

00

SMfDfD

fDfDACP

Normalization mode D0→K~180k from D*+/-→ D0


Direct ADirect ACPCP in Cabibbo suppressed D in Cabibbo suppressed D00 decays decays

D0KK16220 200

D07334 97

• Systematic dominated by tracking charge asymmetry, scales with statistics of control sample

• KK channel suffers from partially reconstructed D background , would benefit from PID.

• CDF yields prospects: 2M D* tagged D0K per 1 fb-1

ACP ~ 10-3 is achievable with full Tevatron run (4-9 fb-1) - at SM limit

issue will be if SVT trigger can cope with Lumi increaseissue will be if SVT trigger can cope with Lumi increase.


Mixing in the DMixing in the D00 system system

•D0 mixing receives x and

y contributions

•SM model expectations: x and y : ~ 10-4 - 10-2

(depending on the model)

•Enhancements in x could

be hint of New Physics

• RSM ~ O(10-6)


Search for Search for DD00 mixing through mixing through

Can search for comparing lifetime of CPeigenstate (D0→KK) and CP mixed state (D0→K):

yCP (K)/(KK) - 1

Best measurement at present from BaBar: yCP=0.006

yCP=0.034 0.0140.007

• CDF is currently performing D0 KK, , K lifetime analysis • expect (c) < 2 m (statistical only)

• most of systematics cancel in the ratio, but:• Deconvolve SVT trigger bias at 1 m level is a challenge• Nasty effect from secondary D0 from B’s


Direct Search for MixingDirect Search for Mixing

•Most sensitive method comes from looking for ‘Wrong Sign’ K pairs in D0 decays.

•These occur directly through DCS decays.

•Time dependent analysis can decouple contributions from:

D0 K+ -

D0

• Direct DCS• Interference• Mixing

DCS

Mix

(x’ and y’ because of possible strong phase difference between diagrams)


DD00 Wrong Sign decays Wrong Sign decays (time integrated analysis)(time integrated analysis)

• Almost 0.5 M Right Sign D*D0reconstructed in 350 pb-1 selected by SVT trigger

• No PID so use of kinematics to reduce background from misreconstructed D0

Get the WS D* yield binning in D* mass difference fit the signal

NWS = 2005 ± 104


DD00 Wrong Sign rate results: Wrong Sign rate results:

• Results competitive with B-factories (CDF has x2 data on tape)

• Next step: time dependent analysis and limit in the x’ y’ plane

Time integrated WS/RS ratio:

Which in the limit of no mixing is:

RWS:RS = RD = BR(D0K+-)/BR(D0K-+)


LHC-b prospects for charm CPV and mixingLHC-b prospects for charm CPV and mixing

• Will implement a dedicated D* trigger stream:– Hadron trigger: displaced vertex +high PT tracks (4kHz).

Expected composition b:c ~ 50%:20%

– High level D*(D0hh) selection “offline quality” (250Hz). Expect b:c ~ 36%:24%

• In one year of running (107 s) at nominal luminosity (2·1032 cm-2s-1):– Expect 250 - 500 M D* D0 decays with D0K channel, 102 x CDF !

( from Guy Wilkinson and Frederic Teubert )

•Raw estimates (based on signals statistics only) for sensitivity to charm CPV and mixing are:

– ACP) [D0KK] ~ 10-4 normalizing to K mode

– yCP) ~ 10-4 in the lifetime difference analysis

– x’) ~ 10-5 in mixing search through Wrong Sign' Kp signalsLHC-b will possibly be sensitive in SM range, detailed studies on-going …


SummarySummary

• Charm production (cc and charmonium) is usefull test of QCD calculations to be tuned for precise background estimates in NP searches.

• Already high precision results from Tevatron, to be explored at LHC.

• A wide range of charmed hadrons are accessible at collider experiments, complementarity to e+e-

• CDF demonstrates that is possible to perform high precision searches for charm CPV and mixing in hadronic modes D0hh

• LHC-b will have 2 orders of magnitude more D0hh yields and will be very competitive in this field.

• Huge CDF and D0 legacy of knowledge in doing Charm Physics at hadronic machines is left to next generation experiments.


Backup slidesBackup slides


Tevatron performancesTevatron performances

•CDF II has collected so far ~ 1.26 fb-1 out of 1.57 fb-1 delivered by Tevatron.

•Record peak luminosity is ~ 1.8∙1032 cm-2s-1

•Around 900 pb-1 are available for Charm/Beauty physics (good tracking detector conditions)

•Current analyses use 180 - 350 pb-1 of integrated luminosity


The CDF II detectorThe CDF II detector

CDF Tracking System

Particle ID

•dE/dX in COT

•Time Of Flight detector

Lepton ID

Muons: CMU, CMP, CMX 1.1)Electrons: CEM (EM calorimeter) CPR (pre-shower detector)


SVT: the CDF hadronic SVT: the CDF hadronic h.f.h.f. trigger trigger

≈ 47 m ≈ 35 m + 30 m

SVT resolution Beam spot size

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

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

Impact Parameter distribution

Offline ~ 45 m

d

beam spot

COT track ( 2 parameters) 5 SVX coordinates

Impact Parameter (transverse projection)

Primary Vertex

Secondary Vertex

Impact Parameter ( ~100m)

Lxy ~ 1 mm

B decay


B physics triggers at CDF IIB physics triggers at CDF II

1-Displaced track + lepton (e, )

120 m < I.P.(trk) < 1mm

PT(lepton) > 4 GeV

Semileptonic modes

2-Displaced tracks

PT(trk) > 2 GeV

120 m < I.P.(trk) < 1mm

pT > 5.5 GeV

fully hadronic modes

Di-Muon (J/)

Pt() > 1.5 GeV

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

Conventional at colliders (Run I)

+

With SVT trigger


B production x-section, Run IB 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


Differential Charm Meson X-Section 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:


Calibration signature:

• exclusive D.P.E. production of c

• search for c J/

Esclusive channel: p + p p + H (bb) + p

• Hexcl ~ 3 fb , signal / background ~ 3 @ LHC• then: MH = Mmiss =

Charmonium as probe for diffractive HiggsCharmonium as probe for diffractive Higgs

H:loop-tχ:loop-bχ:loop-cγγ:loop-u

0b

0c

2p1ps


Welcome back to BWelcome back to Bcc

Hep-ex/0505076

080.0032.0045.0245.0

/6

/6

KJBBRGeVP

JBRGeVP

tB

ctBc

106 events46.07.3 events

23.23.42.6275)(c

GeVBm c

• First signal of fully reconstructed Bc

• Mass measurement on ~0.8 fb-1

•Mode that gave the first evidence of the Bc (CDF Run I)

•Large yield, no clean resonance though!

~ 39 signal candidates

future perspectives for charm physics at hadron machines

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