CP Violation in Neutral B Meson System

1

CP Violation in Neutral B Meson System

CP Violation in Neutral B Meson System

Jingsheng Li

Apr 16, 2007

Presentation for Intro. Exp. Part. Course

Jingsheng Li

Apr 16, 2007

Presentation for Intro. Exp. Part. Course

2

Outline

CKM Matrix CP Violation in B Meson Decay Detector Design and Data Selection Event Reconstruction Result Conclusion

3

CKM Matrix

Quark Mixing, SU(2)U(1) repr.

V=V1V2V3

CP Violation due to angle

€

L = U Lγ μ DL = u c t ( )γ μ (1+ γ 5)V

d

s

b

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

€

V =

1 0 0

0 c2 −s2

0 s2 c2

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

c1 s1 0

−s1 c1 0

0 0 e iδ

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

1 0 0

0 c3 s3

0 −s3 c3

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟€

where DL = V

d

s

b

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟L

4

CKM Matrix continued

€

VCKM =

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟=

1− λ2 /2 λ Aλ3(ρ − iη )

−λ 1− λ2 /2 Aλ2

Aλ3(1− ρ − iη ) −Aλ2 1

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

€

VudVub* + VcdVcb

* + VtdVtb* = 0

B decay

5

B Decay

€

B0 → J /ψ +

€

l + l€

2π

3π

€

K 0

€

b → c + W +* → c + c + s

6

CP Violation in B Decay Indirect CP Violation

Direct CP Violation Interference between

channels (to deg ’)

€

BL = B1 + εB2

BS = B1 + εB2

⎧ ⎨ ⎩

€

η00 ≠ 0;η +− ≠ 0

€

η00 ≠ η +− ;φ00 ≠ φ+−

7

B Decay in Belle and BABAR

PEP-IILum: 31033/cm2se+/e-:3.1GeV/9.0GeV=0.56

€

Υ(4S)

€

Btag

€

BCP

€

l±

€

K ±

€

D*

€

π ±

CP Eigenstate€

BR ≈10−4

Low momentum

€

l±

€

π ±

€

π 0

e+ e-

Flavor tagz

z/(c)=t

€

Btagged

8

BaBar Detector

9GeV

3.1GeV

9

Belle Detector

10

Comparison

Belle BaBarBeam Asy. 8.0GeV/3.5GeV

=0.425, 22mrad

9.0GeV/3.1GeV

=0.56, head on

Vetices SVD 3ly SVT 5lyCharged Ptc CDC DCH

Ptc ID CDC, ACC, TOF DIRC

EM shower ECL EMC

, KL RPC IFR

11

CP Violation Parameter Decay modes:

Distribution Asymmetry €

J /ψKS0

€

ψ(2S)KS0

€

χclKS0

€

J /ψKL0

€

J /ψK*0

€

KS0π 0

€

f±(Δt) =e

−|Δt | /τB0

2τB 0 (1+ | λ |2)

×1+ | λ |2

2± Imλ sin(Δm

B 0Δt) m1− | λ |2

2cos(Δm

B 0Δt) ⎡

⎣ ⎢

⎤

⎦ ⎥

€

ACP (Δt) ≡f+(Δt) − f−(Δt)

f+(Δt) + f−(Δt)= −η f sin2β sin(Δm

B 0Δt)

ηf= -1 +1-1 -1 0.650.07

€

λ =η f e−2iβ

€

=arg[−VcdVcb* /VtdVtb

* ]

angular mixing

12

Event Reconstruction Event Selection

Flavor Tagging Total events 32106

Full BCP <1000

Fitting

€

E = Ebeamcm − EB

cm < 3σ ~ 30MeV

€

mES = (Ebeamcm )2 − ( pB

cm )2 > 5.2GeV

€

BCP

€

J /ψ → l+l−

€

2.95 ≤ me +e − ≤ 3.14GeV

€

KS0 → π +π −

€

489 < mπ +π − < 507MeV

€

KS0 → π 0π 0

€

800MeV < m2π

13

14

BABAR Result

Sin2=0.590.14(stat) 0.05(syst)

At 4 level |λ|=0.930.09(stat)

0.03(syst)

15

Belle Result

sin2=0.990.14(stat) 0.06(syst)

At 6 level

16

Conclusion

(Indirect) CP Violation at 4 levelNow sin2=0.6850.032

Direct CP Violation in

Precise Measurement for SMStay Tuned for New Physics

(Indirect) CP Violation at 4 levelNow sin2=0.6850.032

Direct CP Violation in

Precise Measurement for SMStay Tuned for New Physics

€

B → K +π −

€

AK +π − =

A K −π + / A

K +π − −1

A K −π + / A

K +π − +1= −0.115 ± 0.018

(2005)