Upload
abel-taylor
View
221
Download
0
Embed Size (px)
DESCRIPTION
Julia Thom, FNALEPS 2003 Aachen Tevatron Performance Record lumi.: cm -2 s -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 important Systems on (Feb.2002-Feb2003) delivered To tape Delivered To tape
Citation preview
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!