Oscillazioni del mesone D 0
description
Transcript of Oscillazioni del mesone D 0
Gianluca Cavoto 1
Oscillazioni del mesone D0
Gianluca CavotoINFN Roma La Sapienza
Commissione Scientifica Nazionale IRoma, 3 aprile 2007
Gianluca Cavoto 2
Outline
• Neutral mesons flavor oscillation
• Charm meson mixing
• Evidence from B-factories– D0+
– D0 l l, D0s+-, D0+-+-
• Outlook
Gianluca Cavoto 3
Neutral Mesons systems– Two-level system (M0,M0)
• Weak interactions remove degeneracy, make them unstable
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”)
Gianluca Cavoto 5
Some visual examples
Lifetime units
Probability to find a M0(M0) after a given time
Gianluca Cavoto 6
How to generate this ??
No tree level Flavor Changing Neutral Currents (FCNC) in SM
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)
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
Gianluca Cavoto 9
The missing tile
Gianluca Cavoto 10
Charm Meson Mixing
Gianluca Cavoto 11
Short and Long distance• Prediction x and y
Sum of intermediate REAL states
y
x VIRTUAL states
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
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
Gianluca Cavoto 14
Experimental Searches
Gianluca Cavoto 15
Charm physics with B-factory
• Run1-5, more than 500M cc events
Run1-5
Gianluca Cavoto 16
The technique
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
Gianluca Cavoto 18
Double-Cabibbo Suppressed Decays
V*cd
Vus
Vcs
V*ud
Gianluca Cavoto 19
Time evolution
is the (relative) strong phase
WS (relative to RS) time-dep. rate(small x and small y limit)
RM
Gianluca Cavoto 20
Event Selection
Gianluca Cavoto 21
RS and WS data set
Gianluca Cavoto 22
Decay time analysis
• Resolution function from RS sample
Selectioncriteria
Gianluca Cavoto 23
Background components
Discrimination power from m() and m
Gianluca Cavoto 24
Signal extraction384 fb-1
Gianluca Cavoto 25
RS decay time analysis
D0 lifetime and time resolution function from RS sample
Gianluca Cavoto 26
WS decay time with mixing
384 fb-1
Gianluca Cavoto 27
Evidence for D0 mixing!
3.9
Best fit solution
Gianluca Cavoto 28
Validation: m() and m fit in t bins
Relative rate of WS events clearly increases with time
Gianluca Cavoto 29
Validation: fit RS for mixing
Gianluca Cavoto 30
Systematics uncertainty
Gianluca Cavoto 31
Systematics on Decay time
Gianluca Cavoto 32
Allowing for CP violation
CP asymmetry in DCSD !
Gianluca Cavoto 33
analysis from Belle
Gianluca Cavoto 34
More evidence…!
Gianluca Cavoto 35
Belle evidence on yCP“Apparent” lifetime difference between D0 -+ and +-, +-
D= mixing phase
Gianluca Cavoto 36
Results on yCP
• Plot di combinazioni
Belle hep-ex/0703036
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-
Gianluca Cavoto 38
D0
Effective phase
Select special region of Dalitz plot
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!
Gianluca Cavoto 40
D0 KS Dalitz model
Gianluca Cavoto 41
Belle D0 KS results
Gianluca Cavoto 42
D-mixing with Semileptonic decay
No DCS sl. !
D0 l l
Gianluca Cavoto 43
Summary and Outlook
Gianluca Cavoto 44
Summary
» BaBar updating multibody decays analysis, yCP measurements
» BaBar KS on-going
y
Gianluca Cavoto 45
Interpreting the results Ciuchini et al. hep-ph/0703294
D0 and D0
95%
68%
HFAGPRELIMINARY
Gianluca Cavoto 46
Measuring To beat down the model systematics measure phases directly
Gianluca Cavoto 47
Double tag at (3770) [CLEO-c]
Need to run
On
threshold
DCP±
neutral D CP eigenstate
(3770) decayconserves CP
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
Gianluca Cavoto 49
Back up slides
Gianluca Cavoto 50
Fit signal MC events
Gianluca Cavoto 51
Coverage test