Cano Ay , Johannes Gutenberg Universität , ayc@uni-mainz.de

Selected B-physics at DØ for the DØ Collaboration

09 nov 2005 Flavour in the era of the LHCCERN

• Tevatron and DØ• Results and Prospects

s/s

Bs Mixing Bs

• Summary

09 nov 2005 Flavour in the era of the LHC , Cano Ay 2

Tevatron

Highest Luminosity at DØ:1.6ּ1032 cm-2s-1

Recorded Luminosity:1.04 fb-1

Delivered Luminosity:1.24 fb-1

Integrated Luminosity per Experiment: ~2 fb-1 until 2006 ~8 fb-1 until 2009

09 nov 2005 Flavour in the era of the LHC , Cano Ay 3

DØ Detector

SMT H-disks SMT F-disks SMT barrels

Muon system:Coverage: ||<2Good shielding2T Toroid Field

Tracking system:Coverage: ||<3.22T Solenoid Field

1m

09 nov 2005 Flavour in the era of the LHC , Cano Ay 4

• single inclusive muons, ||<2.0, pT>3,4,5 GeV

Muon + track match at Level 1 and a muon at Level 2 Unbiased; prescaled or turned off depending on inst. Lumi. At Level 3 also invariant mass track selections (imply impact parameter bias)

• Dimuons

Muon triggers

09 nov 2005 Flavour in the era of the LHC , Cano Ay 5

Motivation

Bd Mixing Bd & Bs Mixing

• ms/md constrain unitarity triangle2

tdd V~mΔ

larger uncertainties!

smaller uncertainties!

2

td

2

ts2

BB

2BB

B

B

d

s

V

V

B

B

m

m

mm

d0d

s0s

0d

0s

f

f2

td

2

ts

V

V

12

12

12HLq

12LHq

00

21

L

00

21

H Marg

cos2=

M2mm=m

)B|B|(=B|

)B|B|(=B|

Δ

Δ

• SM predicts a ms0 and s0

Tevatron currently only place to study Bs Meson

09 nov 2005 Flavour in the era of the LHC , Cano Ay 6

Motivation

• Expectation for lifetime difference s/s (with experimental input)

• Discrepancies to SM Expectation new physics

• decay Bs : example indirect search for New physics

FCNC process highly suppressed in SM Observing the decay would indicate new physics (SUSY, MSSM, etc)

0412007/phyLenzhep.A05.012.0ss

09 nov 2005 Flavour in the era of the LHC , Cano Ay 7

• Reconstruction of b in semileptonic Decays • Reconstruction of BsDsX decays• Reconstruction of B Hadron Signals at D0• Evidence of BsDs(2536)X• Observation of the Bc Meson and study of ist properties• Study of exited B Mesons (B**)• A high statistics measurement of the Bs

0 lifetime• Observation of Bs(2s) and a measurement of B(Bs(2s) ))/B( Bs(2s) )• Search for Bs rare decays• FCNC charm decays and Observation of Ds • Bs mixing with Bs DsX, Ds and opposite-side flavor tagging• Bs mixing with Bs DsX, DsK*K and opposite-side flavor tagging• Flavor oscillations in Bd Mesons with 3 combined Taggers• Measurement of upsilon differential cross section• Measurement of the ratio B+ and B0 meson lifetimes• Measurement of the b lifetime in the decay J decays• Measurement of the Bs lifetime in the exclusive decay channel BsJ/ • Measurement of the lifetime difference in the Bs system• Measurement of the semileptonic branching fractions of B mesons to narrow D** states• Observation and Properties of the X(3872) Decayoing to J/+-

B-physics program at DØ

09 nov 2005 Flavour in the era of the LHC , Cano Ay 8

s/s Bs Mixing Bs

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• Reconstruct

• the polarisation state of the vector mesons in the final states are different for CP eigenstates • Simultaneous fit to

/JBs KK

ss Analysis

09 nov 2005 Flavour in the era of the LHC , Cano Ay 10

ss Results

DØ : 450pb-1

09 nov 2005 Flavour in the era of the LHC , Cano Ay 11

• Analysis improvement Fit all 3 angles in transversity, not only 1 angle update silicon Layer 0 extrapolate forwards to higher luminositiy

Prospects s/s

09 nov 2005 Flavour in the era of the LHC , Cano Ay 12

ss

Bs Mixing Bs

09 nov 2005 Flavour in the era of the LHC , Cano Ay 13

sB

sD

)(

)(

reconstructedside

oppositeside

hadronb

Semileptonic decays:(trigger on )

Bs Mixing: Analysis

sB

sD

)()(

Signal selection:

Candidatesk34

K)K(KD

)KK(D*

s

s

1.

Proper decay time:

hadronb Flavor at time of production(Flavor tagging): • lepton charge • secondary vertex Jet chargeD²=(1.940.140.09)%

3.

)B(P

Lmc

T

xyB

sB)(

L

)(

sD2.

K)D(P)B(P TT fs150

09 nov 2005 Flavour in the era of the LHC , Cano Ay 14

DØ Bs Mixing Limit

Limit for both channels • very large semileptonically decaying sample (~34k) in 610pb-1• after flavour tagging (~4.2k)

09 nov 2005 Flavour in the era of the LHC , Cano Ay 15

Prospects ms

• more data

• General Analysis improvements

hadronic channel, other semileptonic channels Event-by-event fit, not binned likelihood improved flavour tagging

• Upgrades layer 0 silicon, improved vertex resolution L3 bandwidth 50Hz to 100Hz

ms sensitivity

09 nov 2005 Flavour in the era of the LHC , Cano Ay 16

Bs Mixing ss

Bs

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Search for rare decays

• ‘blind’ analysis with 300 pb-1

• Signal selection was optimized with random grid search

Signalbackground

09 nov 2005 Flavour in the era of the LHC , Cano Ay 18

Search for rare decays

• Calculate BR Limit using the B+J/K+ as normalisation channel

• After selection 4.31.2 background events were expected and 4 events were found in the signal region

09 nov 2005 Flavour in the era of the LHC , Cano Ay 19

Prospects Bs

• Based on DØ results at ~300pb-1

• Scale to higher luminositiy

• Bands indicate 10% variation of events

09 nov 2005 Flavour in the era of the LHC , Cano Ay 20

• Currently Tevatron is the best place to study Bs Meson• Presented three preliminary results (only fraction of B-physics program at DØ )

• Lifetime difference s/s

• Mass difference ms (only semileptonic)

• rare decay Bs

%)95CL(ps3.7m 1s

28.038.0

s

s 24.0

CL%)90%(95at

)100.3(107.3)B(B 77s

with more statistics error will be reduced by a factor ~10

With improved analysis, upgrades and more data push sensitivity above the SM expectation

Not sensitiv for SM Prediction, but maybe for new physics

Summary

09 nov 2005 Flavour in the era of the LHC , Cano Ay 21

Backup

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Transversity

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Combined Likelihood

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Proper decay length

09 nov 2005 Flavour in the era of the LHC , Cano Ay 25

untagged tagged

K*K data sample

09 nov 2005 Flavour in the era of the LHC , Cano Ay 26

Limits , K*K

Limit only for

)KK(Ds

K)K(KD *s

09 nov 2005 Flavour in the era of the LHC , Cano Ay 27

Disciminating variables Bs