Cano Ay, Johannes Gutenberg Universität, [email protected] B mixing and flavor oscillations at DØ...

Cano Ay , Johannes Gutenberg Universität , [email protected]

B mixing and flavor oscillations at DØ

Cano Ay University Mainz

for the DØ Collaboration

23 may 2005

Frontiers in Contemporary Physics III

Vanderbilt University Nashville, Tennesse

23 may 2005 FCP III , Cano Ay 2

• Motivation• Mixing and Oscillation• Tevatron and DØ Detector• Flavor tagging• Bd Mixing Limit• Bs Mixing Limit• Prospects and plans• Summary

Outline


Motivation

• The ratio ms/md constrains one side of the unitarity triangle

• also study CP violation in Bs system• studied in Kaon and Bd system

Belle and Babar not sensitiv LHCB not running Tevatron currently only place to study Bs

Mixing


Particle Antiparticle

*tbVtdV

b sd ,tdV*tbV

0B

bsd ,

W W 0B

*tbVtdV

b

tcu ,,

sd ,tdV*tbV

0B

bsd ,

tcu ,,

W

W

0B

tcu ,,

tcu ,,

The transition of a neutralparticle into its antiparticle

iscalled Mixing.

lhds

lhds

dsdshl,

ΓΓ=

mm=Δm

B|q±B|p=B|

,

,

0,

0.

ΔΓ

Mixing

dttm

qqq

q

t

tatBpure

q

s

tmP

2

)cos(1exp )/(

0

),,(0

0

0

:""

:""

s

s

B

B


Standard Model expectation:

Δms= 14 ....28ps-1

Δmd= 0.5ps-1

measurement of Δms/Δmd

Vts/Vtd

constrain unitarity triangle

Unitarity triangle

(0,0) (0,1)

(,)

*ubud

*tbtd

VV

VVarg

*cbcd

*tbtd

VV

VV

*tbtd

*cbcd

VV

VVarg

*cbcd

*ubud

VV

VVarg

*cbcd

*ubud

VV

VV

(0,0) (0,1)

(,)

*ubud

*tbtd

VV

VVarg

*cbcd

*tbtd

VV

VV

*tbtd

*cbcd

VV

VVarg

*cbcd

*ubud

VV

VVarg

*cbcd

*ubud

VV

VV


Measure m asymmetry

high uncertainties f(QCD)

reduce uncertainties by taking ratio

Mixing (2)


• From the CKM fit: ms~ 18 ps-1

• Heavy Flavor Averaging group: combined LEP, SLD, CDF1 results ms > 14.5 ps-1

Mixing (3)

Mixing limit obtained using „Amplitude“ Method Fit data to

Fit for A as a function of ms

o A peaks at 1 for a measuremento Sensitivity given by 1.645A = 1 (95% CL)o Limit given by A<1-1.645A (95% CL)

)cos(12 tmAe st A sm

BSSDN

tsm

eysensitivit

2

22

2

flavor tagging performance resolution selectionWTRT

WTRT

NN

NNDDilution


Tevatron

Big advantage for B physics : Bs meson production

12321017.1

: scm

Achieved

LHCbefore

expected1

1232

84

1035.1:

fb

scmL


Luminosity

460pb-1

200pb-1


D0 Detector

SMT H-disks SMT F-disksSMT barrels

μ+

νμ

π-

K-

K+

BsD-

sBsBd

trigger muon

μ+

νμ

π-

K-

K+

BsD-

sBsBd

trigger muon

Semileptonic decays: • trigger on muon

good muon system• reconstruct tracks and vertex

good tracking system


Silicon Microstrip Tracker (SMT)

• Silicon Microstrip Tracker ~800.000 channels point resolution: 10m Secondary vertex resolution

- 40m (r-)- 80m (r-z) •Trackers

Silicon Tracker: |η|<3Fiber Tracker: |η|<2

•Magnetic field 2T


Muon Sytem

• 2 Tesla toroid magnet between A und BC Layer Muon momentum

propotional drift tubes

pixel scintillators

A minidrift tube with cover partially removed

• Muon system coverage ||<2 and good shielding


B production Fermilab: σ ≈ O(100μb)L1 Trigger acceptance (DØ: Muon) : σ ≈ O(3-5μb)

B production and decay

B0s → D-

s μμ

D-s → (K+K-)-

B0d → D*(2010)-µ+

µ D*(2010)-D0(K+-)-

B+ → D0µ+ µ D0 K-+

Used Decays:


Flavor tagging

1. Soft Lepton Tag (SLT)

2. Opposite Jet charge (Jetq)

3. Same Side Tag (currently only used for Bd)

0 QQOpposite

DDs ,

0,dsB

Opposite

OppositeBsidesamesidesameK ,

Flavor tagging : determine b-flavor at production time!

0)( QQ sidesame 0)( QQ sidesame

oscillated not oscillated

0 QQOpposite

reconstructed sideopposite side

i

iTi

iTiJ ppq )()(Q0 QQJ 0 QQJ


Bd Sample

angle and distance : distance PV D Vertex (xy-plane) D Vertex not before B Vertex Angle between PV B Vertex and PV D Vertex

Charged tracks: pT > 0.65 GeV/c

impact parameter significance:

322 zcadca zcadca

0DB

)2010(0 DBd

Single µ data – 200pb-1


Bd Mixing Limit

)2010(0 DBd

0DB

SSTJetq

SSTJetq SLT

Asy

mm

etr

y

Asy

mm

etr

y

SLT : D0 = (44.85.1)%Jetq+SST: D0 = (14.91.5)%

Jetq+SST: D = 27.9%

md=0.4560.034ps-1(stat) 0.025ps-1(syst)

consistent with md=0.5020.007ps-1 (world average)


Currently only using a single semileptonic decay of the BsBs Ds X (Ds p) ( K K)

Using + SV vertex tag (Opposite side tag, independent of reconstructed side)

The goal was to develop tools and to allow a baseline to build on for the future

Bs Mixing analysis procedure


Eventdisplay : MC BsDs()

Blue Marker recoRed Marker MC true

KK

Ds-VertexBs-Vertex

PV

Eventdisplay : MC BsDs()

Blue Marker recoRed Marker MC true

KK

Ds-VertexBs-Vertex

PV

angle and distance : distance PV D Vertex (xy-plane) D Vertex not before B Vertex Angle between PV B Vertex and PV

D Vertex Angle between PV D Vertex and D

momentum …

Charged tracks: pT > 0.7 GeV/c impact parameter

significance Invariant KK mass

1.006 < M(KK) < 1.30

Bs Sample

13.3K Ds

5K D±

13.3K Ds

5K D±


Inputs to the fitting procedure MC

Sample composition K-factor to take non-reconstructed particles

into account Efficiencies Visible Proper Decay Length (VPDL) resolution

VPDL resolution has been tuned using data Dilution from B0

d and B+u semileptonic

samples

Bs Mixing fitting procedure


Decay Sample composition

Bs→Dsμν 20.6%

Bs→D*sμν 57.2%

Bs→D*0sμν 1.4%

Bs→D*1sμν 2.9%

Bs→DsDsX 11.3%

B0→DsDX 3.2%

B-→DsDX 3.4%cc estimated at ~ 3.5 ± 2.5 %

VPDL (cm)

Efficiency drop at low VPDLdue to impact parameter cuts on tracks from Ds decay

Sample Composition and efficiency


Decay <k>

Bs→Dsμν 0.878

Bs→D*sμν 0.857

Bs→D*0sμν 0.829

Bs→D*1sμν 0.817

Bs→DsDsX 0.738

B0→DsDX 0.681

B-→DsDX 0.687

)(

)(

st

st

BP

DPk

M

B kxcsK K x VPDL

K-factors


VPDL resolution parametrized with three Gaussians

Track by track smearing

dependant on track momentum and polar angle

Tuning results with one scale factor 1.095

VPDL Resolution: MC tuned with data

no smearingafter smearing

VPDLrec – VPDLgen [cm]


0DB

DØ Run II preliminary )2010(0 DBd

DØ Run II preliminary

Dilution

SLT + SV Jetq : D0 = (39.03.2)% D = (47.62.0)%

use mean : Davr=(45.41.7)% for Bs asymmetry


No obvious oscillations in the μDssample

ms > 5.0 ps-1 at 95% CL using “Amplitude” method

Bs Mixing Limit


Scaling of the current sensitivity with luminosity

- if analysis remains unchanged- with expected improvements

Sensitivity vs. LuminositySemileptonic channels


Use both semileptonic and hadronic Bs samples More statistics in semileptonics Better proper decay time resolution in

hadronics (no )

DZero has access to hadronic Bs sample triggering on opposite side muon Muon is used as high purity tag

Detector addition in fall: “Layer 0” Silicon detector

Proposal to increase rate to tape from 50 to 100 Hz in fall sample limited by L3 trigger and offline

CPU – expect large gain in yield thanks to dedicated B-physics bandwidth

Bs Mixing Projections


Summary

measured, which is in agreement with world average

md=0.4560.034ps-1(stat) 0.025ps-1(syst) developed a procedure to measure ms using

semileptonic channel BsDs()

ms > 5.0ps-1 at 95% CL will add more semileptonic channels and hadronic

channels „Layer 0“ Silicon detector and increasing L3 rate

will improve resolution and increase statistics

Cano Ay, Johannes Gutenberg Universität, [email protected] B mixing and flavor oscillations at DØ...

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