oscillazioni del mesone d 0
DESCRIPTION
Oscillazioni del mesone D 0. Gianluca Cavoto INFN Roma La Sapienza Commissione Scientifica Nazionale I Roma, 3 aprile 2007. Outline. Neutral mesons flavor oscillation Charm meson mixing Evidence from B-factories D 0 + D 0 l l , D 0 s + - , D 0 + - + - - PowerPoint PPT PresentationTRANSCRIPT
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Gianluca Cavoto 1
Oscillazioni del mesone D0
Gianluca CavotoINFN Roma La Sapienza
Commissione Scientifica Nazionale IRoma, 3 aprile 2007
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Gianluca Cavoto 2
Outline
• Neutral mesons flavor oscillation
• Charm meson mixing
• Evidence from B-factories– D0+
– D0 l l, D0s+-, D0+-+-
• Outlook
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Gianluca Cavoto 3
Neutral Mesons systems– Two-level system (M0,M0)
• Weak interactions remove degeneracy, make them unstable
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Gianluca Cavoto 4
Neutral mesons oscillations
Time evolution for meson of known flavor at t=0
An opposite flavor component appears after a while!
M0 “oscillates” into M0!(also dubbed “mixing”)
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Gianluca Cavoto 5
Some visual examples
Lifetime units
Probability to find a M0(M0) after a given time
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Gianluca Cavoto 6
How to generate this ??
No tree level Flavor Changing Neutral Currents (FCNC) in SM
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Gianluca Cavoto 7
Can you see New Physics ?
And the top was discovered 8 years after!
B0 mixing was argued by UA1 and directly observed by ARGUS in 1987
Large mixing frequence implied t quark was heavy (mt > 50 GeV/c2)
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Gianluca Cavoto 8
Even more ambitious today!Bd,s (K) mixing on the punch line for virtual effects from NP
Not only x and y but also phases in the mixing CP violation
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Gianluca Cavoto 9
The missing tile
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Gianluca Cavoto 10
Charm Meson Mixing
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Gianluca Cavoto 11
Short and Long distance• Prediction x and y
Sum of intermediate REAL states
y
x VIRTUAL states
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Gianluca Cavoto 12
SM prediction for charm mixing
Always hard to evaluate SU(3) breaking !!! (HQET, propagation of common hadronic states,…)
SU(3) breaking effect more important for y
bottom quark
ruled out by VCKM Box diagram contribution
Naively
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Gianluca Cavoto 13
New Physics in Charm ?
Hard to see a clear cutPushing the limit down
excludes models
Try to separate x and y!Try to separate x and y!
2006 limit
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Gianluca Cavoto 14
Experimental Searches
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Gianluca Cavoto 15
Charm physics with B-factory
• Run1-5, more than 500M cc events
Run1-5
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Gianluca Cavoto 16
The technique
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Gianluca Cavoto 17
Flavor tagging
• Same flavour: Wrong-Sign (WS)mixing may have occured
• Opposite flavour: Right-Sign (RS)unmixed events
Flavor at production
Flavor at decay
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Gianluca Cavoto 18
Double-Cabibbo Suppressed Decays
V*cd
Vus
Vcs
V*ud
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Time evolution
is the (relative) strong phase
WS (relative to RS) time-dep. rate(small x and small y limit)
RM
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Gianluca Cavoto 20
Event Selection
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Gianluca Cavoto 21
RS and WS data set
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Decay time analysis
• Resolution function from RS sample
Selectioncriteria
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Gianluca Cavoto 23
Background components
Discrimination power from m() and m
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Gianluca Cavoto 24
Signal extraction384 fb-1
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RS decay time analysis
D0 lifetime and time resolution function from RS sample
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Gianluca Cavoto 26
WS decay time with mixing
384 fb-1
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Gianluca Cavoto 27
Evidence for D0 mixing!
3.9
Best fit solution
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Validation: m() and m fit in t bins
Relative rate of WS events clearly increases with time
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Gianluca Cavoto 29
Validation: fit RS for mixing
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Gianluca Cavoto 30
Systematics uncertainty
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Gianluca Cavoto 31
Systematics on Decay time
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Gianluca Cavoto 32
Allowing for CP violation
CP asymmetry in DCSD !
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Gianluca Cavoto 33
analysis from Belle
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Gianluca Cavoto 34
More evidence…!
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Gianluca Cavoto 35
Belle evidence on yCP“Apparent” lifetime difference between D0 -+ and +-, +-
D= mixing phase
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Results on yCP
• Plot di combinazioni
Belle hep-ex/0703036
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Gianluca Cavoto 37
Separating x and y only cannot separate x and y
Need info on strong phases– Multibody decays:Dalitz models
DCS decays proceed primarily through K*+- while CF through K-+
CF DCS
D0 K-
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D0
Effective phase
Select special region of Dalitz plot
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Gianluca Cavoto 39
D0 KS
Both flavor (K*-+/K*+-) final states in the same Dalitz plot!
CP-eigenstate (KS) and flavor states (K*-+) in the same Dalitz plot!
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Gianluca Cavoto 40
D0 KS Dalitz model
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Gianluca Cavoto 41
Belle D0 KS results
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Gianluca Cavoto 42
D-mixing with Semileptonic decay
No DCS sl. !
D0 l l
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Gianluca Cavoto 43
Summary and Outlook
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Summary
» BaBar updating multibody decays analysis, yCP measurements
» BaBar KS on-going
y
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Gianluca Cavoto 45
Interpreting the results Ciuchini et al. hep-ph/0703294
D0 and D0
95%
68%
HFAGPRELIMINARY
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Measuring To beat down the model systematics measure phases directly
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Gianluca Cavoto 47
Double tag at (3770) [CLEO-c]
Need to run
On
threshold
DCP±
neutral D CP eigenstate
(3770) decayconserves CP
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Gianluca Cavoto 48
And CP violation?
In general NP weakly constrained if SM not known
Nevertheless SUSY coupling can be constrainedhints on squark and gluino masses!
Neutral meson mixing always a window into unknown (virtual) states!
Ciuchini et al. hep-ph/0703294
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Gianluca Cavoto 49
Back up slides
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Gianluca Cavoto 50
Fit signal MC events
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Gianluca Cavoto 51
Coverage test