Direct CP violation in Direct CP violation in decays at Belle decays at Belle

Yuuj ｉ UnnoHanyang university

(For the Belle Collaboration)

June 16th-21st, SUSY2008 @ Seoul, Korea

17 June, 2008 Y.Unno 2

Introduction (Direct CP violation)Introduction (Direct CP violation)Decay amplitudes:

CP violating asymmetry (ACP) is defined as:

A non-zero ACP requires the following 3 conditions: more than 2 amplitudes non-zero strong phase difference : I - j = ≠ 0 non-zero weak phase difference : Ái - Áj = Á ≠ 0

DCPV measurement plays important roles:Test KM modelHelp to understand B decay mechanismSearch for new physics beyond SMIn ratios of BFs, systematic uncertainties cancel

17 June, 2008 Y.Unno 3

DCPV through interference of T & P

3 through bu transition (but theoretically challenging…)

Naïve expectation Acp() ~ Acp()ACP()≠ ACP() might indicate new physics

Introduction (Introduction ()) (T+P)(T+P)

(T+P)(T+P)

New physics ? Á3

17 June, 2008 Y.Unno 4

Introduction (Introduction ())(P)(P) (P)(P)

ACP~0 in SM ACP~0 in SM S~sin21() in SM (S~O(0.1)) help to test S puzzle:

sin21 from bsqq differs from J/

(T)(T) ACP~0 in SM No P due to Isospin symmetry

(P)(P) bd Penguin Br ~0.05 x Br( ) Sizable ACP in SM

(J.-M. Gerard, W.-S. Hou, PLB253,478)

17 June, 2008 Y.Unno 5

Inte

grat

ed lu

min

osity

(/fb

)

8.0 GeV e–

KEKB & Belle detector

Two separate rings for e+ and e–

Energy in CM is 10.58GeV (4S)

Ring circumference is ~3Km

Two separate rings for e+ and e–

Energy in CM is 10.58GeV (4S)

Ring circumference is ~3Km

Total ∫L dt = 842/fb

Peak L = 17.1 /nb/sec

Results are based on

449 or 535 MBB pairs

3.5 GeV e+

17 June, 2008 Y.Unno 6

Kinematic reconstruction S

B reconstruction

Main background e+e– qq(q=u,d,s,c) event topology

/ K separation PID

Signal extraction

Unbinned ML fit to E, mbc for B & B

Analysis Overview

Jet-likeSpherical

17 June, 2008 Y.Unno 7

ACP() w/ 535MBB

Signalreflectioncontinuum

charmless B

# of signal, continuum, charmless B bkg are floated yields are fixed to the expectation using BFs and KID eff./fake small KID charge asymmetry is corrected

Nature 452, 332-335(2008)

N() = 1856±52 N() = 2241±57

Observation of DCPV in

ACP() = –0.094±0.018±0.008 with 4.8 Consistent with BABAR :

0.0070.004

-CP 0.0180.107A

)(

17 June, 2008 Y.Unno 8

ACP() & ACP() w/ 535MBB

simultaneous fit to 0 and

ACP() = + 0.07±0.03±0.01 ACP() = +0.07±0.06±0.01

: (T) : (T & P)

Nature 452, 332-335(2008)

Both and are (T & P) dominant modes Naïve expectation is ACP() ~ ACP() ACP puzzle is established with 4.4 significance

ACP = ACP() - ACP() = +0.164±0.037

ACP() = – 0.094±0.018±0.008

≠

17 June, 2008 Y.Unno 9

ACP() & ACP() w/ 449MBBPRL 98, 181804(2007)simultaneous fit to + and

ACP() = +0.03±0.03±0.01

No significant asymmetry in either mode

: (bs P)

0.020.13)(A 0.230.24

0CP

± feed across

: (bd P)

17 June, 2008 Y.Unno 10

ACP() w/ 535MBB PRD 76, 091103(2007)

ACP() = –0.05±0.14±0.05 “sin21” = +0.33±0.35±0.08

consistent with HFAG Ave: sin21 = +0.668±0.026

ACP() and S() with time-dependent CP analysis b flavor tagging efficiency =~30% vertex from S trajectory and IP : efficiency =~ 30%

17 June, 2008 Y.Unno 11

ACP = ACP() – ACP() = +0.164±0.037 @ 4.4

A CP puzzl

e

Published in

Nature

Discussion on ΔACP puzzle

What is happening with ACP() and ACP() ?

17 June, 2008 Y.Unno 12

Discussion on ΔACP puzzleACP~ 0 is expected if C and PEW are neglectedACP~ 0 is expected if C and PEW are neglected

Enhancement of C ?

C＞ T is needed (C/T = 0.3–0.6 in SM)

breakdown of theoretical understanding

Enhancement of PEW ?

Would indicate new physics.

Due to poor understanding of strong interactions?

　 C.-W.Chaing, et al., PRD 70, 034020

　 Y.-Y.Charng, et al., PRD 71, 014036

　 W.-S.Hou, et al., PRL 95, 141601

　 S.Baek, et al., PRD 71, 057502

　 S.Baek, et al., PLB 653, 249

　 H.-n.Li,et al., PRD 72, 114005

etc…

　 C.-W.Chaing, et al., PRD 70, 034020

　 Y.-Y.Charng, et al., PRD 71, 014036

　 W.-S.Hou, et al., PRL 95, 141601

　 S.Baek, et al., PRD 71, 057502

　 S.Baek, et al., PLB 653, 249

　 H.-n.Li,et al., PRD 72, 114005

etc…

17 June, 2008 Y.Unno 13

Isospin sum rule among CP asymmetries(M. Gronau, PLB 672, 82-88)

A violation of the sum rule would be an unambiguous evidence of new physics

Discussion on ΔACP puzzle

The sum rule predicts ACP() = –0.15±0.06

–15% DCPV in ???

ACP() is still too large to claim a discrepancy.

Have to examine this with larger statistics

17 June, 2008 Y.Unno 14

ACP = ACP() – ACP() = +0.164±0.037 @ 4.4

A CP puzzl

e

Published in

Nature

Discussion on ΔACP puzzle

What is happening with ACP() and ACP() ?

17 June, 2008 Y.Unno 15

Summary

ACP measurements in all decays

DCPV observation in decay ACP puzzle is established w/ 4.4

ΔACP = ACP() – ACP() = +0.164±0.037 Published in Nature 452, 332-335(2008)

No significant ACP in

To test “isospin sum rule” more statistics are needed

Stay tuned for update results in summer !

17 June, 2008 Y.Unno 16

Systematics of ACP

detector bias of 　 from qq bkg in (E, mbc)

detector bias of 　 from D*+D0()

17 June, 2008 Y.Unno 17

Systematic Errors

S A Vertexing 0.011 0.020 Flavor tagging 0.008 0.005Resolution 0.066 0.010Physics 0.007 0.001Possible Fit bias 0.009 0.004BG fraction 0.009 0.001BG dt shape 0.046 0.019Tag-side interference 0.001 0.043--------------------------------------------------Total 0.082 0.053

17 June, 2008 Y.Unno 18

NIM A 533, 516 (2004)

Flavor taggingFlavor taggingb flavor information is needed for non-flavor-specific B0 modes

Judge tag side b flavor with flavor specific processes:

sign of lepton / Kaon / slow-pion.

Tagging efficiency is 30 %

17 June, 2008 Y.Unno 19

Analysis Analysis (Kπ separationKπ separation)

Cherenkov light yield

Ionization energy loss

Charged particle emit cherenkov light (transition radiation)

if velocity is faster than that of light in material

17 June, 2008 Y.Unno 20

Analysis Analysis (Kπ separationKπ separation)

Efficiency Fake rate

K ~90% ~7%

π ~89% ~12%

ex) BK+π- selection

Before cut

After cut

17 June, 2008 Y.Unno 21

Analysis Analysis (KID correction: ex. B0K)

trueCPmeas

+π-Kmeas

-π+K

meas+π-K

meas-π+Kmeas

CP A N + N

N - N A ≠≡

trueCP

trueCPmeas

CP A)f+f-ε+ε-(+)f+f+ε+ε+(

A )f-f-ε+ε+(+)f-f+ε+ε-(=A

Belle KID has high performance BUT NOT PERFECT

　 Existence of KID charge asymmetry smears true Acp

　 Finite KID fake dilutes true Acp : K ＋ K

To obtain true Acp, introduce KID correction

B0K : 1% correction is applied

+π

-K

-π

+K ff=f ff=f

+π

-K

-π

+K εε=ε εε=ε

17 June, 2008 Y.Unno 22

3.5 GeV e＋

8.0 GeV e —

Introduction (Belle detector)Introduction (Belle detector)

Aerogel Cherenkov Counter

Kπ separation

Central Drift Chamber

Charged track momentumKπ separation

KLMuon Detector

KL, μ detection

Silicon Vertex Detector

B vertex

TOF Counter

Kπ separation

Electromagnetic Calorimeter

γ, π0 reconstruction e ＋－ , KL identification

17 June, 2008 Y.Unno 23

14 countries 55 institutes

~400 collaborators

IHEP, ViennaITEPKanagawa U.KEKKorea U.Krakow Inst. of Nucl. Phys.Kyoto U. Kyungpook Nat’l U. EPF Lausanne Jozef Stefan Inst. / U. of Ljubljana / U. of MariborU. of Melbourne

BINPChiba U.U. of CincinnatiEwha Womans U.Fu-Jen Catholic U.U. of GiessenGyeongsang Nat’l U.Hanyang U.U. of HawaiiHiroshima Tech.IHEP, BeijingIHEP, Moscow

Nagoya U.Nara Women’s U.National Central U.National Taiwan U.National United U.Nihon Dental CollegeNiigata U.Nova GoricaOsaka U.Osaka City U.Panjab U.Peking U.Princeton U.RikenSaga U.USTC

Seoul National U.Shinshu U.Sungkyunkwan U.U. of SydneyTata InstituteToho U.Tohoku U.Tohuku Gakuin U.U. of TokyoTokyo Inst. of Tech.Tokyo Metropolitan U.Tokyo U. of Agri. and Tech.INFN TorinoToyama Nat’l CollegeVPIYonsei U.

Introduction (Belle Collaboration)Introduction (Belle Collaboration)

17 June, 2008 Y.Unno 24

Introduction (Introduction ())

17 June, 2008 Y.Unno 25

ΔACP puzzle

Belle

ACP(-) = –0.094±0.018±0.008

ACP() = +0.07±0.03±0.01 　

ACP = ACP() – ACP() = +0.164±0.037 (4.4)

Probability for no difference is ＜ 9.3x10-6

BABAR

ACP() = –0.107±0.018+0.007-0.004 　 (PLR99,021603(2007))

ACP() = +0.030±0.039±0.010 (PRD76,091102(2007))

ACP = +0.137+0.045-0.044 　 (3.0)

Belle + BABAR

ACP = +0.152±0.029 　 5.2

Belle

ACP(-) = –0.094±0.018±0.008

ACP() = +0.07±0.03±0.01 　

ACP = ACP() – ACP() = +0.164±0.037 (4.4)

Probability for no difference is ＜ 9.3x10-6

BABAR

ACP() = –0.107±0.018+0.007-0.004 　 (PLR99,021603(2007))

ACP() = +0.030±0.039±0.010 (PRD76,091102(2007))

ACP = +0.137+0.045-0.044 　 (3.0)

Belle + BABAR

ACP = +0.152±0.029 　 5.2