highlights of the belle experiment

Andrzej Bożek nz11 Highlights of the Belle Experiment SAB Review 2007 1

Selection of the most important Belle results since last SAB review (2005):

B0 'K0 : first observationof time dependent CPV

in rare B decays; B- - : evidence for purely leptonic decay (decay with missing energy); New particles with charm; First results from Bs ((5S) run).

B0 (db)

B- (ub)

Bs (sb)0

Highlights of the Belle Experiment

Precision tests of the Standard Model and New Physics searches at the B-Factory

e+e-(4S) B0 B0 / B- B+

Precision tests of the Standard Model and New Physics searches at the B-Factory

e+e-(4S) B0 B0 / B- B+

A.BożekNZ11


Rare B decays:

b s: B- f0(980)K- , B0 f0(980)K*0

B decays with missing energy: b c -: B0 D*- +

New particle searches :

-Dsj(2700) in B- D0D0K- analysis -Charmed baryons study

Physics analyses in Kraków

Krakow’s Belle group

•5 PhD physicists

•3 electronics eng.

•3 PhD students

•1 diploma student


B Factory Physics Program

W±qi

qjVij

Cabibbo-Kobayashi-Maskawa (CKM) matrix

1()

Unitarity Trianglebeing overconstrainedat B factories

d s b

u

c

t

CKMV ud us ub

cd cs cb

td ts tb

V V V

V V V

V V V

0*** tbtdcbcdubud VVVVVV

*ubudVV

*tbtdVV

*cbcdVV

• Studies of rare B, D and decays with potential sensitivity to new physics;

• Precise tests of the most stringent Standard Model (SM) predictions,

e.g. unitarity relations between elements of the quark mixing matrix.

2()

3()


~710x106 BB pairs

13 countries, 57 institutes, ~400 collaborators

More than milion BB pairs per day

Asymmetric ee collider

8GeV (e-) 3.5GeV (e+)


Time-dependent CP violation (tCPV)“double-slit experiment” with particles and antiparticles

a flagship measurement at B-factories

b c

d

csd

J/KS

b

d cJ/KS

B0

bcsddt

t

+

Quantum interference between two diagrams

tree diagram box diagram + tree diagram

You need to “wait” ( t0) to have the box diagram contribution.You need to “wait” ( t0) to have the box diagram contribution.

B0B0


B0 J/ K0

sin21= 0.642 ±0.031 (stat) ±0.017 (syst)sin21= 0.642 ±0.031 (stat) ±0.017 (syst)

B0 tag_B

0 tag

535 M BB pairs_

hep-ex/0608039hep-ex/0608039

1()

Obtained precision is 1.3oObtained precision is 1.3o

+sin21

tCPVtCPV


d

b_ _

sssd

_gtB0

K0

, ’...w

d

b_ _

sssd

_gB0

K0

, ’...g

b s

penguinb sqq

B decays with b s transition one of the best new physics probes

SUSY as an example

d

b_ c

c

sd

_wB0J/

K0

treeb ccs

Extra CPV phase from New Physics

=?)(2sin 1 cb )(2sin 1 sb SM


tCPV in B0 'K0

sin21(b→s) = 0.64 0.10(stat) 0.04(syst) sin21(b→s) = 0.64 0.10(stat) 0.04(syst)

_535M BB

First observation of tCPV (5.6in a single b s mode

First observation of tCPV (5.6in a single b s mode

t distribution and asymmetry

PRL 98, 031802 (2007)PRL 98, 031802 (2007)


Smaller than bccs in all of 9 modesSmaller than bccs in all of 9 modes

1 from b s transition

Theory tends to predict positive shifts

Naïve average of all modessin21(b→s) = 0.52 ± 0.05

2.6 deviation

Naïve average of all modessin21(b→s) = 0.52 ± 0.05

2.6 deviation

We need more statistics and more bs modesWe need more statistics and more bs modes

B0 J/ K0…


B0 f0(980)K*0

Motivation:

• Not observed yet, expected BF ~10-6

• Expected to be dominated by b s transitions -mode with simple final state

• In addition nature of f0(980) can be studied (candidate for four quark state or other exotic combinations).

Results should be published this year

Started as a diploma work; can lead to an important physics output in hot field.

Ver

y Pre

limin

ary


B decays with missing energy

• Fully reconstruct one of the B’s to :

- tag BB events– determine other B flavor/charge & momentum

Υ(4S)

e (8GeV)

e+(3.5GeV)

B

B

fully reconstructedsecond B i.e. BD

Decays of interests BXu l , BK BD,

Powerful tools to study B decays with neutrinos

Method

sensitive to new physics

sensitive to new physics


B++

BB++ D D0 0 ++

KK++ - - ++ --

BB-- --

ee--ee

BB++ D D0 0 ++

KK++ - - ++ --

BB-- --

ee--ee

Missing momentum


Observation based on the residual energy in the electromagnetic

calorimeter not used in both B reconstruction.

The First B Evidence

Signal +

background

BackgroundB

Signal

17.2 events in the signal region. 17.2 events in the signal region.

+5.3 - 4.7

+0.56 +0.46 -4-0.49 -0.51Br B 1.79 ×10

Measured branching fraction:

PRL 97,251802 (2006) PRL 97,251802 (2006)

Another „multi-neutrino” mode: B0 D*- + experimentally more difficultanalysis is carried on in Kraków, results are expected this year.


Dsb

c

c

cq

cs

q

b c

q

csq

e

e

e

e

BaBarat slac B-factory

Belle

2003 2004 2005

DsJ(2317)

DsJ(2458)

X(3872)Y(3940)

Y(4260)

Z(3930)

New charmed mesons : new unresolved questions about charm spectroscopy

Picture: R. Faccini, DOE review 2005

New particles, charm spectroscopy B factories are an abundant source of other particles:

charmed mesons and baryons : e+e- cc, B decays, …

lepton „factory” : e+e- +- ~700 M events

D,c , X

K

„cs” type

Charmonium type


efficiencysideband

New DsJ in B+→D0D0K+

N=399 40

DsJ(2700)new state

Dalitz plot M(D0D0) vs M(D0K) differs from 3-body phase space

Interpretation still open

hep-ex/0608031hep-ex/0608031

1J

)20115(

/)112715(

30182

P

3632

21114

MeV

cMeVM

N

KDDB 00 of Signal


We are in high statistics era at B factories ( 1ab-1 ~109 BB)

- many interesting & unexpected results

38 papers in Phys.Rev.Lett. (with discovery status) during 2005/2006

- powerful tool to study rare and experimentally difficult B decays

that are not accessible in other environments

Good prospects for next generation experiment at Super B-Factory

SuperKEKB (50 ab-1 ~5*1010 BB) New physics searches in rare B & decays, that are not accessible on hadron machines e.g: BK , BD,BD*, BXs/Xu

→→e…

solve the b s & other ~2.5 puzzles

Conclusions and prospects


Future plansFuture plans

~1010 BB/year !!& similar

number of +-

Lpeak = 1.71034cm-2s-1

Ltot = 710 fb-1 (Dec. 2006)

1.7x1034

700 fb-1

5x1034

~1 ab-1

8x1035

~10 ab-1

Lpeak (cm-2s-1)Lint

Major upgrade ofKEKB & Belle detector(>1yr shutdown)

world records !

We are here


e+ e- -> Y(5S) -> BB, B*B, B*B*, BB, BB, BsBs, Bs*Bs, Bs*Bs*

1985: CESR (CLEO,CUSB) ~116 pb-1 at Y(5S)

2003: CESR (CLEO III) ~0.42 fb-1 at Y(5S)

2005: Belle, KEKB ~ 1.86 fb-1 at Y(5S)

CLEO

PRL 54, 381 (1985)

(5S)

2006, June 9-31: Belle, KEKB ~21.7 fb-1 at Y(5S)

(5S) test runs

Bs -> Ds+ -

9 events in Bs* Bs*

5.408< MBC<5.429 GeV/c2

Bs* Bs*Nev=20.0 ± 4.8

6.7

BsBs , Bs*Bs , Bs*Bs*

MCsum of all Bs decay modes


Hunting Rare Decays

Observation of BK l+ l-

CPV in B decay

Beginning of B->K0 saga

Direct CPV in B0K+

FB asymmetry in BK* l+l-

Evidence of B

Observation of bd

• High luminosity • Good detector (PID, vertex…)• Analysis techniques

– qq background suppression– Fully reconstructed tag

Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !

Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !


Major Achievements Expected at SuperKEKB

Discovery of B K

Discovery of B DDiscovery of B

CKM Angle Measurements with 1 degree precision

Discovery of CP Violation in Charged B Decays

Discovery of Direct CP Violation in B0 K Decays (2005)

Discovery of CP Violation in Neutral B Meson System (2001)

|Vub| with 5% Precision

Search for New CP-Violating Phase in b s with 1 degree precision

“Discovery” withsignificance > 5

Discovery of New Subatomic Particles

sin2W with O(10-4) precision

Observations with (5S), (3S) etc.

Case 2: New Physics with Extended Flavor StructureCase 2: New Physics with Extended Flavor Structure

# SUSY GUT withgluino mass = 600GeV,tan = 30

Discovery of Lepton Flavor Violation in Decays#

Discovery of Lepton Flavor Violation in Decays#

Discovery of New Right-Handed Current in b s Transitions #

Discovery of New Right-Handed Current in b s Transitions #

Discovery of New CP Violation

in B K0 Decays#

Discovery of New CP Violation

in B K0 Decays#


= 0.425 (Belle) 0.56 (BaBar)

Principle of tCPV measurement

t z c

CP-side

Flavor tag and vertex reconstructi

on

Flavor tag and vertex reconstructi

on

1. Fully reconstruct one B-meson which decays to CP eigenstate2. Tag-side determines its flavor (effective efficiency = 30%)3. Proper time (t) is measured from decay-vertex difference (z)

electron

positron

(4S)resonance B1

B2

+-

K+

-0

D

+

-

KS/L

J/

z ~ 200m(Belle)

B0

B0_


tCPV in B0 decays

Mixing-induced CPVMixing-induced CPV Direct CPVDirect CPV

e.g. for J/ KsS = CPsin21 = +sin21 A = 0to a good approximation(CP : CP eigenvalue)

e.g. for J/ KsS = CPsin21 = +sin21 A = 0to a good approximation(CP : CP eigenvalue)

+

Vtd

Vtd


K.UlmerUpdate after ICHEP2006 !


Belle 2006: tCPV in B0 K0

“sin21” = 0.50 0.21(stat) 0.06(syst) A = 0.07 0.15(stat) 0.05(syst)

“sin21” = 0.50 0.21(stat) 0.06(syst) A = 0.07 0.15(stat) 0.05(syst)

KS and KL combined background subtracted good tags t –t for KL

t distribution and asymmetry

_535M BB

Consistent with the SM (~1lower) The most precise measurement

now

Consistent with the SM (~1lower) The most precise measurement

now

unbinned fitSM

hep-ex/0608039hep-ex/0608039


B0 D*- + search

Experimentally very difficult:•At least 2 in decay chain•Low effective Br: Effective Br for decay chain ~ 10-4 – 10-5

Motivations: • BD(*)not observed yet • Decays with heavy fermions enhancement of effects beyond SM• Many avaiable observables from decays transverse or longitudinal polarisation• Semileptonic heavy quark decay – clear theoretical situation: good description of b quark in HQET• BG for BDdecay

need for more effective reconstruction of Btag

or/and higher statistics

Results should be presented this year


New New DDsJsJ in B in B++→→DD00DD00KK++

N=399 40

hep-ex/0608031hep-ex/0608031

efficiency

sideband

Dalitz plot M(D0D0) vs M(D0K) differs from 3-body phase space

DsJ(2700)new state JP = 1-

ψ(4160) reflection

highlights of the belle experiment

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