Rare Charm and B decays at CDF

Julia Thom

FNAL

EPS 7/18/2003

•Tevatron/CDF Experiment

•Decay Rate Ratios and CP Asymmetries

of Cabibbo suppressed D0 decays

•Search for D0→

•Search for B0s,d →

The Tevatron

Main Injector(new)

TevatronDØCDF

Chicago

p source

Booster

Tevatron Upgrade: Higher Bunch Crossing Rate: 396 ns 5-10 higher target lumi than RunI Higher C.o.M Energy RunI:1.8 TeV RunII:1.96 TeV

Tevatron Performance•Record lumi.: 4.5 1031 cm-2s-1

(~factor 2 better than RunI)•Improving slowly•4-7 pb-1 per week

For CDF:Current:~200 pb-1 to tape

For this talk:~65pb-1 w/all importantSystems on (Feb.2002-Feb2003)

delivered

To tape

Delivered

To tape

The CDF Run II Detector

• New DAQTrack based trigger at L1 (XFT)Impact parameter trigger at L2 (SVT)(by far most important upgrade for B and charm)

• New Silicon system– 7-8 layer silicon detector (up to ||~2)Improved b-tagging Extended muon systems (to ||~1.5)

• Time of flight detector(particle ID)• New central drift chamber

–Detector upgrades give new charm and bottom physics program–Charm Results already competitive with world’s best

Silicon Vertex Trigger

Includes~33mbeamspot

=47m

Online IP resolution from SVTLevel 1 track trigger: high pt

Level 2 track trigger: large d0

Improves RunI sensitivity by4-5 orders of magnitude CDF as “Charm Factory” ~million D0’s per 100 pb-1

Triggers used in this talk:•Two track trigger 2 tracks pt>2GeV, d0>120mm, pt>5.5 GeV•Rare B trigger 2 muons with momentum/vertexing requirements

Decay Rate Ratios ofCabibbo Suppressed D0 Decays

)(

)(0

0

0

0

0

0

)())((

KKD

KD

KD

KKD

N

N

KDKKD

TH: R(KK/)<1.4 Ex: ~2.5 (world average)

(difference prob. due to FSI)

•Many systematics (trigger, reconstruction..) cancel in ratio

•Relative acceptance estimated from MC + realistic simulation

•Use triggered track pairs

•Combine D0 with soft for D*

•No particle ID

D*/D0 Signal Extraction

Selection cuts:•D0 Impact Parameter<100m, pt>5.5 GeV•D0 Lxy>350 m•m(D*)-m(D0) 3 around expexted value

Extract number of signal&bkg events from fits:

93560 D*→D0 →[K

8320 D*→D0 →[K

3697 D*→D0 →[

Monte Carlo InputRelative Acceptance Corrections from MC

Different efficiencies due to:

• Nuclear Interactions of K/, K+/K-

• ,K decay length• trigger bias (due to different opening angle)

Using realistic detector simulation:

Decay Ratios: Results

(D0KK)/(D0 K = 9.38 0.18(stat) 0.10(syst) %

(D0)/(D0 K = 3.686 0.076(stat) 0.036(syst) %

Competitive with FOCUS 2003:

(D0KK)/(D0 K = 9.93 0.14 0.14 %(D0)/(D0 K = 3.53 0.12 0.06 %

CP asymmetries of Cabibbo Suppressed D0 decays

0

0

0

0

0

0

0

0

)()(

)()(

D

KKD

D

KKD

D

KKD

D

KKD

CP NN

NN

A

TH: O(10-310-2)

NP can enhance the CP-violation rate

Soft charge tags D0 flavor: q(soft)>0: D0 q(soft)<0:D0bar

•Need to correct observed asymmetries for intrinsic charge asymmetry of CDF detector (soft tracks)

•Study charge asymmetry as a function of soft pt

Charge Asymmetry in the CDF DetectorStudy asymmetry using unbiased tracks and correct

NNNNpA tQ )(

)()()()(

0

0

fDfDfDfDAcorr

Residual asymmetry syst.error

Q

Q

AA

11

(Expect no CP asymmetry)

(same track quality cutsgeneric track sample)

CPV: Results

CP(D0KK) = 2.0 1.7 (stat) 0.6 (syst) %

ACP(D0) = 3.0 1.9 (stat) 0.6 (syst) %

CLEO results: %8.02.39.1)(

%8.02.20)(0

0

DA

KKDA

cp

cp

Plan: redo analysis for 8-10 times statistics

Search for FCNC D0→•SM expectation BR~ 3*10-13

•Best limit: <4.1x10-6 (90% CL) (Beatrice/WA92, E771)

•BR significantly enhanced with New Physics

(e.g. R-Parity Violation Susy: ~3.5*10-6)

• Events from two-track trigger use first 63pb-1 of data

•Normalize to D0→to cancel acceptance and trigger effects •Only relative efficiency needed

)()()(

)()(

)( %900%90

BRN

NDBR

upperCL

CL

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

BackgroundFakes 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

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 observed events: Ncl=2.3

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

Search for FCNC Bs,d →

•BR(Bs0→)~10E-9 in SM

•Best published limit:2.6 10E-6 at 90% C.L.(CDF)•Can be enhanced by >2 orders of magnitude in SUSY scenarios•Particular interest: hand in hand with deviations of (g-2)hep-ph

Relevant part predicts 10-7:10-8

Observable in Run II

If true, m(h)~120 GeV

Lots of theoretical interest

Bs → search method

LdtN

BBRBs

obsCL

s

%90)(

•Acceptance estimated from MC (|y(B)|<1.0 and pt(b)>6 GeV), •Trigger and reconstruction efficiency from data•Analysis cut efficiency from MC (x-check with B+ →J/Psi data)•Bs cross-section: assume Bd:Bs 3:1

Discriminating variables:•Dimuon Inv.mass (m around PDG•Lifetime (cm•Pointing angle (phirad•Isolation of Bs candidate (iso>0.65)

Background

Estimate background from sideband(Heavy flavor contr. <10-9)

If correlations between cut variables smallFactorize background estimate

)()(),|()( mRisocsbNbkgN

Background: 0.57 +- 0.22 events

Bs → Sensitivity

Current estimated sensitivityoptimized cuts and 65 pb-1 of data:

BR(Bs → ) < 2.4 10-6

RunI limit:2.6 10-6

BR(Bd →

not opened the box yet, will include 2-3 times the data and full muon coverage soon

Conclusions First Results on Rare Charm (and B) decays at CDF

Decay ratios and CPV of Cabibbo suppressed D0 decays already competitive/best sensitivity

FCNC searches: best limits

D0 → factor 2 improvement over best publ. limit

Bs → expect to improve RunI limits soon!