flavor mixing in the bb system motivation of studying b b system measuring the b b flavor...
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Flavor mixing in the BB system
Motivation of studying B B system Measuring the B B flavor oscillation BaBar experiment
Production of B B B B tagging Particle detection B B mixing Results of mB measurement
Motivation of studying B B system
What is the CKM matrixMagnitude of the CKM matrix elementsAdvantage of studying BBVij magnitude for KK and BB
What is the CKM matrix“weak eigenstates” “flavor eigenstates”
Vud can be studied in decay
Vus can be studied in K decayd
uduud
n p
W e-
e
Vij can be studied by selecting appropriate decay
s
K
W u
ll
Vu
d
Vu
s
Magnitude of the CKM matrix elements
“weak eigenstates” “flavor eigenstates”
Close to Cabibo angle sin=0.22
b
B
W u/
ll
b
B
W c
D*
ll
~7% ~0.04%
Diagrams with Vub and Vtd are difficult to measure but they contain the imaginary part of the CKM
sin2
1
Vbc
Vub
Motivation of BB studying
Unitarily of CKM matrix implies:
Areas of triangles are equal but lengths of the sides are not
+
Motivation of BB studyingKK (dsds) BB (dbdb)
For KK and BB the interaction differs strongly
d sW W
s d
K0 K0
W W
s d
K0 K0
W Ws dK0 K0
u
u
c
c
t
t
u
u
c
c
t
t
W W
d
d b
b
B0B0
W W
d
d b
b
B0B0
W W
d
d b
b
B0B0
d s
2
2
6
6
4
6
d s
Consequence of the small Vij for KK and BB systems
5 GeV~0.5 GeV
+’
’ << =3eV =320eV
flavor eigenstate
CP eigenstate
(CPT) mass eigenstate
flavor eigenstate
KK third family contribution is very small small CP violation
(CPT) mass eigenstate
BB all 3 contribution are similar large CP violation
In BB CP violation is more pronounced than in KK
K1
KLK2
KS
BL
B
H
K0
_K0
B0
_B0
Measuring the B B flavor oscillation
Time evolution of BB Schrödinger-like equation Probability for flavor oscillation
Time evolution of BBIn case of CP violation
mass eigenstates of BB are:
Time evolution of the mass eigenstates
mass eigenstates propagate not the flavor eigenstates
=
Schrödinger-like equationThe time evolution of flavored B (B)
obey Schrödinger-like equation
M is the mass matrix is the decay matrix
Solving eigenvalue equation:
mB=Re(+ - -) and B= -2Im(+ - -)
+ = H and - = L
Flavor oscillation
can be used for flavor propagation in time
The time-dependent probabilities proportional to:
~1
B
Flavor oscillation depends on mB:
Measure by BB as function of time
BaBar experiment Production of B B B B tagging in BaBar Typical decay modes for B B Particle detection B B mixing Results of mB measurement
Production of B B in experiment
3.1 Gev e+ + on 9 GeV e- cms boost <>=0.55
e- + e+ Y(4S) (bb resonance) 96% of B B
B B tagging
3 essential measurements
Production of B B in experiment
Typical decay modes for B B
0
1(*)
(*)
(*)0
K
aD
D
DB KKJB 0*0 /
B0
W
b
d d
c
u
d
D*-
Tagging channel
Flavor eigenstate
0*K
Typical decay modes for B B
l
l
l
l
l
l
lD
lDB
(*)
0
W
b
d d
c
l
l
0BD
Leptonic decay mode for tagging
Particle detection in BaBar
the particle collision rate 50 times more than the original facility
Particle detection in BaBar
BaBar detector for photons, leptons & hadrons
• The maximum possible acceptance in c.m.s.
•Excellent vertex resolution
•Tracking over range ~0.6 GeV<pc<~4 GeV...
Experimental observation of B B mixing
)cos1(4
),(Pr
tme
BBBBorBBBBob
Bt
tmBcos
Take into account the finite resolution of the measurement
Pro
babili
ty
Results of mB measurement
Measured mB is in agreement with other measurements
Mix
ing a
sym
metr
y
=3.388 10-4 eV
Conclusions The importance of B B
measurement Flavor mixing Principles of BaBar Results on mB
CP violation will be discussed in coming talk by Moslem
Literature
• Selected Theoretical Issues in B Meson Physics: CKM matrix and Semileptonic Decays I.M.Narodetskii hep-ph/0309229
•The BaBar Physics Book http://www.slac.stanford.edu/BFROOT/www/doc/PhysBook/physBook.html
•A study of time dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the (4S) hep-ex/0201020
-1/3
b t2/3
-1/3
s c2/3
-1/3
d u2/3
sdK
sdK
suK
suK
0
0
ucD
ucD
dcD
dcD
0
0)(
2
10 dduu
du
du