Physics 222 UCSD/225b UCSB

Physics 222 UCSD/225b UCSB

Lecture 7

Mixing & CP violation (3 of 3)

Today, we focus on how to measure things, and what the present knowledge is from the combination of theory and experiment.

Take 2 sources as references:David MacFarlane at SSI 2002Soeren Prell at Lepton-Photon 2009

CKM Matrix Element Magnitudes

Lepton Photon 2009 Expt. Status of the CKM Matrix (S.Prell) 2

Vud

Bd

Bd

Bs B

s

t

W

D DK

π πBKn

p

eee

ννν

νν

Vus

Vub

Vcd

π

eV

cs

e

Bd D

νe

Vcb

Vtd V

tsV

tb

b

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are needed to see this picture.













Why does this matter?

Heavy Quark Symmetry predicts that the B -> D* transitionin B -> D* l nu has trivial form factor for the part of phase space when the D* is at rest in the B restframe.

However, this also leads to minimal pT for the slow pion in the D* -> D pi decay.

|Vcb| is theoretically most accurately extracted from experimental data where it is experimentally most difficult.





Luminosity accumulated by Belle reached 1000/fbon November 29th 2009.



















β from b →(cc) s decays


Theor. clean measurement of |S| = sin2β with B → J/ψ K0, J/ψ K*, ψ(2S)KS, ηcKS, & χc1KS by BaBar and Belle

BaBar, PRD 79,072009 (2009)

0.672 0.0230.004 0.019

WA

WA

SC

= ±= ±

0.687 0.028 0.0120.024 0.020 0.016

SC

= ± ±= ± ± (21.1 0.9)β = ± o

statistically limited

s

γ

β β

⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠





γ = ±(75 12)oUTFit

Lepton-photon 2009 Dalitz analysis now clearly dominates the precision.

Poluektov @ EPS’09

0: SB D K π π− + −→ 0: SB D K π π+ + −→

Basic idea:b -> u transition with c-bar quark from virtual W interferes with b -> c transition,IFF one chooses a decay of the D meson that is common for D and anti-D meson.

The resonance structure then provides the CP conserving “phase analyzer” to measure gamma from the interference.





Global CKM Fit• Consistency of angles

• Consistency of angles and sides from global fit

– Overall good fit (CKMFitter: global p-value 45%)

– ~2σ tension between sin2β and εK / Vub

• correction to εK will make it worse (Buras, Guadagnoli, PRD78, 033005 (2008))

( )( )( )

4.44.289.0

21.1 0.9

75 12

o

o

o

α

β

γ

+−=

= ±

= ±

( )185 13o

α β γ+ + = ±


CKM angles Other constraints All constraints

0.0250.027

0.0160.015

UTFit: 0.154 0.022 CKMFitter: 0.139

0.342 0.014 0.341

ρ ρ

η η

+−

+−

= ± =

= ± =

Future directions• Ever more precise measurement of:

– sin2β from J/ Ks

γ from Dalitz analysis

• Measurements of processes that only occur at 2nd order weak interaction in standard model– B -> s l+ l-– B -> s nu nubar

• Measurements of helicity suppressed decays– B to mu+mu-

• CP violation in the Bs system

βs from Bs → J/ψ Ф decays


New physics in BsBs mixing

CDF/PHYS/BOTTOM/CDFR/9787, DØ Note 5928-CONF

s

γ

β β

⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

D0 and CDF measure βs with angular dependent fit to decay time distributions of Bs → J/ψ Ф

– Simultaneous fit for ΔΓs and βs

• SM predicts βs very small (~0.02)

– sensitive to new physics in Bs mixing

• Prospects

– D0 and CDF working on updates with 2x samples

– LHCb sensitivity with 0.5 fb-1: σ(βs) = 0.02



Physics 222 UCSD/225b UCSB

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ckm matrix s

transitionin b d

b cc s decayslepton

cdf measure s

clean measurement of

standard modelb s

d note

b j k0