Baryonic B Meson Decays

Baryonic B Meson DecaysBaryonic B Meson Decays

IntroductionCharmless decaysCharmful decays Summary

Min-Zu Wang (王名儒 )National Taiwan University

2007/1/9 CYCU Seminar

CP violation in Standard ModelCP violation in Standard Model

In 1973, M. Kobayashi and T. Maskawa realized: CP violation third generation of quarks

In SM, CPV can be accommodated via the CKM matrix, which relates quark mass eigenstates to weak eigenstates:

With 3 quark generations, there is 1 phase in the CKM matrix which is physical (can’t be absorbed in redefinition of the fields)

allows possibility of CP violation

b

s

d

VVV

VVV

VVV

b

s

d

tbtstd

cbcscd

ubusud

'

'

'qi

qj

W

Vij


Two B FactoriesTwo B FactoriesSLAC (史丹福大學 )

BaBar

KEK (日本 )

Belle


Integrated LuminosityIntegrated Luminosity

1.7

229M BB


B Meson ProductionB Meson Production

28.0hadr

bb

Electron-Positron collider: e+e- (4s) B0B0

Only 4s resonance can produce B meson pair Low B0 production cross-section: ~1 nb Clean environment, coherent B0B0 production

GeV28.5

GeV58.10)4(

B

S

M

M


udsuds

offoff Data sidebandData sideband

charmcharm

Background SuppressionBackground SuppressionSFW Moment (F)SFW Moment (F)

cosθB distributioncosθB distribution

udsuds


charmcharm

Signal MC

udsuds charmcharm


Likelihood Ratio (LR)Likelihood Ratio (LR)

bs

s

LL

LLR

Optimized by

studybs

s


Signal ExtractionSignal Extraction

PDFs:Background modeling: a line (curve) to represent the ∆E and the following parametrization first suggested by ARGUS group to represent the Mbc.

Signal modeling: a double Gaussian for ∆E and a Gaussian for Mbc.

])/(1(exp[)/(1)( 22beambcbeambcbcbc EMEMMMf

N

iibcibibcis

BS EMBPEMSPeL1

)( )],(),([

1D-binned fit: maximum Likelihood fitBranching fraction are calculated by ∆E fit

Mbc fit for cross-check.

2D-unbinned fit (∆E-Mbc): Extended maximum likelihood fit.

∆E

∆E Mbc

Mbc


First Observation of Charmless Baryonic B Decays B+ ppK+

First Observation of Charmless Baryonic B Decays B+ ppK+

PRL 88, 181803 (2002)

BF(3-body) >> BF(2-body)

With charmonium veto

PRD 65091103(2002)

( )


New type of B Decays:New type of B Decays:

Peak at Low Mass

Possible explanations Baryon form factor? Quasi 2-body Decay? glueball baryonium Fragmentation?

KppB

fJ(2220)?

Phase-space MC


Observation of BObservation of B00→ P→ PΛπΛπ-- MpΛ PlotObservation of BObservation of B00→ P→ PΛπΛπ-- MpΛ Plot

Theoretical PretictionTheoretical PretictionTheoretical PretictionTheoretical Pretiction 78.1fb78.1fb-1 -1 DataData78.1fb78.1fb-1 -1 DataData

Search for BPΣ0π- negtiveSearch for BPΣ0π- negtive

PRL90 201802(2003)


Many rare baryonic decays foundMany rare baryonic decays found

Kpppp Kspp

*Kpp 0*Kpp

PRL92 131801(2004)


Threshold EnhancementThreshold Enhancement

PLB 617, 141-149, 2005

ppK+ ppK0S

p-

Glueball is ruled out


Angular distribution: ppK+

p

p

K+ӨpX

Proton against K- (p against K

+) : flavor dependence!

ppK signal

at pp rest frame


Information from the ppK+Dalitz plot Information from the ppK+Dalitz plot

•The lower bands shown in the plots are J/psi and eta_c.

•Asymmetry near threshold of ppbar indicates flavor dependence

•Anti-proton moves slower in parallel with proton

PRD72 051101 (2005)


dominant decay diagram

Decay diagrams of Decay diagrams of J/ΨJ/Ψ to baryon pair to baryon pair

042.0036.0676.0 Latest BES result :

θαθd

dN 2cos1cos

< λ1 λ2|U|JM> = AJ λ1 λ2 links DJM λ1- λ2 (θ,φ)

Massless

Proton mass + E M

Quark mass

Kada, Marco and Parisi

Quark + scaler diquark


A twist to compare A twist to compare αA twist to compare A twist to compare α

General form of α: (Phys. Rev. D 51, 3487–3500)

11

11

10 1

2

042.0036.0676.0: BES

10

11~ - 0.8

11


Fit cosθ ( J/Fit cosθ ( J/ → p p) → p p)Fit cosθ ( J/Fit cosθ ( J/ → p p) → p p)

Likelihood fit

B= -0.60 ± 0.13 (stat) ± 0.14 (syst)

pp

= 0.43 ± 0.13 (stat) ± 0.14 (syst)

L = e-(Ns+Nb)/N! [NsPs(Mbci , Ei)(cos)P(cos)+NbPb(Mbci , Ei)]

(cos) - normalized efficiency, P(cos) =

(1+cos2)/(2+2/3)

signal

χ2 fit


Pentaquark search in ppKsPentaquark search in ppKs

Θ+(1540) : uuddsΘ+ K+n Θ+ K0 p

B0 Θ+ pB0 ppK0, B ppKsSearch for B signal with a 20 MeV pKs mass window cut at 1540MeV

dduu s

Θ+ K+ n

d du

uud

p

ds

K0

Θ+

uudsd


Pentaquark search in ppKsPentaquark search in ppKs

Fixed background shape from sideband data

Count the events in signal region and compare with background estimation

BF product upper limit < 2.3 x10-7 at 90% C.L.


B+pΛγ (b sγ) B+pΛγ (b sγ)

PRL 95, 061802, 2005Simultaneous fit on BpΛγ and BpΣ0γSignal Yield for BpΛγ with MpΛ<2.4GeV/c2: 34.1

Statistical Significance: 8.6σ

BF(BpΛγ )(2.16 ± 0.20)x10-6

BF(BpΣ0γ):<4.6 x 10-6

140fb-1

pΛγSignal

+7.1- 6.6

+0.58- 0.53

bsγ MC

Not bremstrahlung


Photon energy and Angular distributionPhoton energy and Angular distribution

Fit results in bins of cosθX with MpΛ<4.0GeV/c2

(Assuming XpΛ, calculated in X rest frame.) Λ

γ

p

θx

bsγ MCSignal Yield

qq backgroundSignal Yield

Lab frame X frame


ggb b s s

s s s s B+ΛΛK+B+ΛΛK+

PRL 93,211801, 2004PRL 93,211801, 2004

+6.5- 5.1

+0.90- 0.70

First observation of bs s s baryonic decay

Signal Yield in 2D fit: 19.9Efficiency: 4.0%-6.9%Statistical Significance: 7.4σ

BF:(2.91 ± 0.38) x 10-6

1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !

2.2. Threshold enhancement Threshold enhancement again.again.

3.3. Compliment to BCompliment to BφφKK(*)(*)

(b(bsss penguin)sss penguin)

1.1. First Charmless B decay First Charmless B decay with two with two ΛΛ! !

2.2. Threshold enhancement Threshold enhancement again.again.

3.3. Compliment to BCompliment to BφφKK(*)(*)

(b(bsss penguin)sss penguin)

140fb-1

threshold peaking


Observation of ηηcc Λ Λ Λ Λ Observation of ηηcc Λ Λ Λ Λ

new

Ratio for baryon quark-diquark model check

PRL 97, 162003 (2006)


Result for B+ppπ+Result for B+ppπ+ 414fb-1

• Fit result for exp7-43 with Mpp<2.8GeV/c2

• Signal Yield for B+ppπ+ : 180.9• LR selection: 0.85 • Statistical Significance: 13.5σ• Signal region

+19.1-18.3

Mbc>5.27 GeV/c2 |ΔE|<0.05 GeV

ppK

ppπ


Theoretical PredictionsTheoretical Predictions

Angular distributionPerturbative QCD(PQCD):

(hep-ph/0606141)Final-State Interaction (FSI):

(hep-ph/0609133)

Upper limitBF of B+→pΔ++ was predicted to be

2.9×10-7 (QCD sum rules, Nucl. Phys. B 345, 137 (1990) )

3.2×10-4 (pole model, Phys. Rev. D 43, 1599 (1991); Phys. Lett. B 237, 513

(1990))

1.4×10-6 (pole model, Phys. Rev. D 66, 014020 (2002))

predicted curve

hep-ph/0606141

B+→ppK+

B+→ppπ+

fitting curve


Preliminary

We apply Mpπ<1.4 GeV/c2 for B+→pΔ0 and B+→pΔ++ study. B+→pΔ0 expected background:81.2background uncertainty:2.0%observed event:?upper-limit:? averaged efficiency:4.0±0.1%BF(B+→pΔ0)< ?B+→pΔ++ expected background:72.3background uncertainty:2.1%observed event:?upper-limit:?

averaged efficiency:11.6±0.2%BF(B+→pΔ++)< ?

Current Work: B+→ppπ+

414fb-1

B+→ppπ+

. signal region

. sideband region

B+→pΔ0

B+→pΔ++


Current Work:Current Work:

The studies of intermediate two-body decays:

We apply 2.262<MΛπ<2.310 GeV/c2 for B0Λcp.BF(B0Λc p): ?

BF(B0Λc p): (2.19 ±0.32 ±0.57) x10-5 (PRL 90 121802)

We apply Mpπ<1.40 GeV/c2 for B0ΛΔ0.BF(B0ΛΔ0 ) < ?

We apply 1.30<MΛπ<1.45 GeV/c2 for

B-Σ*0 p.BF(B0Σ*+ p) < ?

+0.56- 0.49

pB


Study of Study of 0 pB

Phase spacep Λπ0 Signal

Signal yield:Signal yield:

Signal Yield for BpΛπ0 with MpΛ<2.8GeV/c2: 56.1Statistical Significance: 10.2σBF(BpΛπ0 ):

Signal Yield

First observation!


Study of helicity selection rules in weak decay Study of helicity selection rules in weak decay

Decay parameter α:Transition rate R is proportional to (1+αcosθ).

θ is defined as the angle between the initial hyperon polarization and the momentum of the final baryon.

αΛ=0.642±0.013 (PDG, Journal of Phys. G33, 1 (2006))

The effective angular asymmetry parameter α :(J. Phys. G: Nucl. Part. Phys. 29(2003) B15-B22)

For the cascade decay BΛXπ-pX :

θpb is defined as the supplementary angle between the

emitted proton momentum and the B momentum in the Λ rest frame.

π-

p

Λ

θω

π-B

θpb

p


Measurement of α inΛdecaysMeasurement of α inΛdecays

Paper J.Phys. G29, 15 (2003) reported that the dΓ/d cosθ is proportion to (1+αcosθ) when the s quark comes from bLsL penguin-type transition.Systematic error

Source PID LR Fitting Results

B-pΛγ 0.01 0.01 0.01

B-pΛπ0 0.01 0.01 0.01

B0pΛπ- 0.01 0.01 0.01


B0 D(*)0 p p 　

D0 K- +

D0 K- + - +

D0 K- +

BB00 D D00pppp BB00 D D0* 0* pppp

Belle: PRL 8989, 151802 (2002) 29.4 fb-1

b b c c u u

d d

33.6evnts

24.2evnts

34.2evnts

8.9

5.6

5.1

total 19.3 evnts 5.6

D*0 D00


B0c+p

Br = ( 2.19 ±0.32±0.57 Br = ( 2.19 ±0.32±0.57 ) x 10) x 10- 5- 5

+0.56+0.56- 0.49- 0.49

Stat. Sys. error of Br (c+)

First observation of baryonic 2-body decay

19.6+5.0- 4.4

Belle : PRL 90, 121802 (2003) 78 fb-1

b b c c dd

u u uuu u

d d d d

BB00 cc

pp

b b c c u u

d d


BB-- CC++ p p --

264±264±20 20 signalsignalss

CC(2455)(2455)00

CC(2520)(2520)00

sidebasidebandnd

32.632.6

12.12.88

+ 6.6+ 6.6 - 5.9- 5.9

+ 5.7+ 5.7 - 5.0- 5.0

Belle 140 fbBelle 140 fb-1 PRL 97, 242001 (2006)-1 PRL 97, 242001 (2006)

B-c+p- 20.1±1.5 ±2.0±5.2

B-c02455 p 3.67 ±0.36

±0.95

B-c02520 p 1.26 ±0.12

±0.33

BF x 10BF x 10-5-5

+0.74+0.74- 0.66- 0.66

+0.56+0.56- 0.49- 0.49

~ 25% of total BF

b b c c u u

d d

Observation of new 2-body decay


BB0 0 ( (cc++p) p) --

M(c+p) structure in 3, 4 body decays

CC++/0++/0 (2455/2520) excluded (2455/2520) excluded

BB- - ( (cc++p) p) --

B Signals byB Signals byE fitE fit

consistent with 4-body consistent with 4-body MC phase space, MC phase space, fine structures ?fine structures ?

MC 4-body phase spaceMC 4-body phase space

Prelim

inar

y

Prelim

inar

y


Observation of B+c+c

-K+ Observation of B+c+c

-K+

Unexpected large rate considering the limited phase sapce

Threshold effect?

PRL 97, 202003 (2006)

c+ pK-π+ signal

BF(B+c+c

-K+ ) = (6.5 ± 1.1 ± 3.4) × 10-4+1.0-0.9


CKM(cc)=VcbVcs* <-> CKM(cp)=VcbVud*

cc 10-3 >> cp 10-5

Observation of B cc

Enhancement for smaller Q ?

Hep-ex/0510074

B+ c0c

+ B0 c-c

+

c π 1%


Observation of J/p Observation of J/p

J/p J/ppPRD72 051105 (2005)


Search for inclusive Λc+ production in

tagged B sample

Search for inclusive Λc+ production in

tagged B sample

N(B+) = 200359± 705

N(B0) = 110735± 424


Determination of BF(B Λc+ X)Determination of BF(B Λc

+ X)

hep-ex/0606026Useful for the understanding ofthe charm counting problem in b decays

BF(B- -> Λc+ X) =(2.8±0.5±0.3 )%

BF(B0 -> Λc+ X) =(5.0±1.0±0.5 )%

BF(B- -> Λc+ X) =(2.1±0.5±0.2 )%

BF(B0 -> Λc+ X) =(1.6±0.9±0.2 )%

+1.0-0.6+1.8-1.0+0.8-0.4+0.6-0.3


SummarySummary

Exclusive baryonic B decays: Well established after few years of B-factory runningBF(2-body) < BF(3-body) BF(2-body) < BF(3-body) Threshold enhancement in the baryon-Threshold enhancement in the baryon-antibaryon systemantibaryon systemSearching ground for exotic statesSearching ground for exotic statesGood crosscheck for baryonic Good crosscheck for baryonic charmonium decayscharmonium decaysLots of local contributions, both Lots of local contributions, both experimental and theoreticalexperimental and theoretical

Documents

Baryonic B Meson Decays