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B mixing and flavor oscillations at D Ø. Cano Ay University Mainz for the D Ø Collaboration 23 may 2005 Frontiers in Contemporary Physics III Vanderbilt University Nashville, Tennesse. Cano Ay , Johannes Gutenberg Universität , [email protected]. Outline. Motivation - PowerPoint PPT Presentation
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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
23 may 2005 FCP III , Cano Ay 3
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
23 may 2005 FCP III , Cano Ay 4
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
23 may 2005 FCP III , Cano Ay 5
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
23 may 2005 FCP III , Cano Ay 6
Measure m asymmetry
high uncertainties f(QCD)
reduce uncertainties by taking ratio
Mixing (2)
23 may 2005 FCP III , Cano Ay 7
• 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
23 may 2005 FCP III , Cano Ay 8
Tevatron
Big advantage for B physics : Bs meson production
12321017.1
: scm
Achieved
LHCbefore
expected1
1232
84
1035.1:
fb
scmL
23 may 2005 FCP III , Cano Ay 9
Luminosity
460pb-1
200pb-1
23 may 2005 FCP III , Cano Ay 10
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
23 may 2005 FCP III , Cano Ay 11
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
23 may 2005 FCP III , Cano Ay 12
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
23 may 2005 FCP III , Cano Ay 13
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:
23 may 2005 FCP III , Cano Ay 14
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
23 may 2005 FCP III , Cano Ay 15
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
23 may 2005 FCP III , Cano Ay 16
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)
23 may 2005 FCP III , Cano Ay 17
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
23 may 2005 FCP III , Cano Ay 18
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±
23 may 2005 FCP III , Cano Ay 19
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
23 may 2005 FCP III , Cano Ay 20
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
23 may 2005 FCP III , Cano Ay 21
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
23 may 2005 FCP III , Cano Ay 22
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]
23 may 2005 FCP III , Cano Ay 23
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
23 may 2005 FCP III , Cano Ay 24
No obvious oscillations in the μDssample
ms > 5.0 ps-1 at 95% CL using “Amplitude” method
Bs Mixing Limit
23 may 2005 FCP III , Cano Ay 25
Scaling of the current sensitivity with luminosity
- if analysis remains unchanged- with expected improvements
Sensitivity vs. LuminositySemileptonic channels
23 may 2005 FCP III , Cano Ay 26
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
23 may 2005 FCP III , Cano Ay 27
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