Recent results from B factories

Recent results from B factories

A. Oyanguren IFIC, UV-CSIC

III Jornadas CPAN, Barcelona2nd – 4th Nov. 2011

III Jornadas CPAN, Barcelona A. Oyanguren 2

Outline

B factories (Belle & BaBar)

Leptonic decays: B, Ds

Semileptonic decays: BD*, Vub, charm

CPV (B, c and decays)

Rare decays: Bs, BK, B, B, D, Xch

Plans at Super Flavour Factories (Belle II & SuperB)

B factories

Υ(4s)e+ e-

BaBar p(e-)=9 GeV p(e+)=3.1 GeV =0.56Belle p(e-)=8 GeV p(e+)=3.5 GeV =0.42

BB

z ~ c B ~ 200m

√s=10.58 GeV

Υ(4s)

KEKB


B factories

Fantastic performance far beyond design values!

In addition to (4S) also large samples of other (nS) decays!

# of

pro

duce

d (

nS)


Leptonic decays Weak annihilation processes (helicity suppressed) sensitive to New Physics effects

B : a charged Higgs could enhance the SM branching fraction:

From Lattice QCD calculations:

[Lenz et al., PRD 83, 036004 (2011)]

by:From semileptonic decays:|Vub|=(3.89 ± 0.44) x 10-3

fB = 191 ± 3 ± 13 MeV

[PDG 2010]

0 = radiativecorrection ~1%)

Motivation:


Leptonic decays Reconstruct one B meson in hadronicB D(*)X or B J/X decays (tag ~1%)

Look for signal in the recoil:

using kinematical and event shape information

Look for extra energy Eextra = sum of neutral clusters in the ECM calorimeter

Study Extra using double tag events to control the bkg.

Extract B from unbinned max. likelihhod fit To Eextra:

426 fb-1

3.3 significanceBaBar combined:

Belle:

Experimental method:


Leptonic decaysFinal measurement of sin2sin2 from CP measurements in B0 → cc K0

Belle, preliminary, 710 fb-1

Tension between B(B→ ) and sin2(~2.5) remains


Leptonic decays Ds can also be enhanced by a charged Higgs or leptoquarks:

At BaBar Ds e, , measured from fully reconstructed events using the recoil mass and the Eextra

521fb-1

fDs calculated by LQCD with small error

fDs = (248.6 ± 2.5) MeV

[PRD RC 82, 091103 (2010)]

BaBar


Agreement with theory

Semileptonic: B D(*)

Sensitive to charged-Higgs effects

Involve form factors which can be measured in BD(*)e/ decays

Observables: R(D) and R(D*) ratios

SM predictions:R(D) = 0.31 0.02R(D*) = 0.25 0.02

[Nierste, Trine, WesthoffPRD78 (08) 015066]

- can be enhanced by the charged-Higgs (tan/mH )- several syst. and theo. uncertainties cancel out

Motivation:



(Improved efficiencies (lepton and Btag)) BaBar: Btag fully reconstructed into hadrons

Bsig: D(*) and lepton (, e)

2D unbinned ML fit mmiss2-p* (3x4 par.)

Yields for:

mmiss2 = (pe+e- -pBtag-pD(*)-p)2

B (D0, D+, D*0, D*+) B (D0, D+, D*0, D*+) B (D0, D+, D*0, D*+)0

- 4 signal samples: (D0, D+, D*0, D*+)

(to extract BD(*))

- 4 control samples: (D0, D+, D*0, D*+)0 (to derive D** bkg)

ee

R(D) and R(D*)


426 fb-1

Large signal significance (>5) for all channels


Semileptonic: B D(*)Results (preliminary):

R(D) = 0.456 0.053 0.056R(D*)= 0.325 0.023 0.027

1.8 larger than SM prediction favors large tan

Comparison with previous results:(w/o 2011) (w/o 2011)

SM predictions:R(D) = 0.31 0.02R(D*) = 0.25 0.02

SM


Semileptonic: Vub

Charmless semileptonic decays allow us to measure Vub (upper UT vertex)

Two different experimental methods:

- Inclusive: high stat. but much bkg: use kinematic cuts: Theory: Shape function from QCD - Exclusive: final meson (,,…): low stat. but better bkg rejection. Theory: Form factors from QCD

BX = BXc + BXu (50 : 1) Challenge: suppress charm background

BX BXu


El, q2, MX and P+ = EX -|pX|

Motivation:

Vub extraction: BNLP: [Bosch et al. , PRD 72 (05) 073006]

DGE: [Andersen et al. , JHEP 0601 (06) 097]

GGOU: [Gambino et al., JHEP 0710 (07) 058]

ADFR: [Aglietti et al., EPJ. C 59 (09) 831]

BXc bkg and BXu signal yields

|Vub|= (4.31 0.25exp 0.16theo )10-3

Average:

[to be submitted to PRD]


426 fb-1

B(BXu)= 1.80 (13) (15) x 10-4

+-

D0

-K+

lepton

Xu

B0B0

(4S)

Signal side

Tag side At BaBar, Btag fully reconstructed hadronically ( ~0.3-0.5%) + or e from the Bsig

estimated from missing E and p Bkg supression:

Several PS regions, 2D fit for B(BXu)/B(BX ) in q2-Mx for p* > 1GeV

Xu from all remaining tracks and neutral clusters

Semileptonic: B XuExperimental Method:

- Combinatorial subtracted from mES

- Charm: B D* partial reconstructed kaon veto, only 1 lepton p* > 1 GeV

BaBar

= , h, h’, ,

The exclusive B semileptonic decay rate is described as function of form factors:

QCD calculations:

Lattice data


Semileptonic: B

Semileptonic: B

|Vub| = (3.19 ± 0.14 ± 0.27) x10-3

(V. Luth, J. Dingfelder)

BaBar, untagged analyses Loose reconstruction from full event

Fit using E = (PBPbeams-– s /2)/2 , mES = [(s/2 + pBpbeams- )2 /E2

beams - p2B] and

q2 = (p + p)2 = (pB- p)2

(in 12 or 6 bins)

PRD 83 (2011) 052011PRD 83 (2011) 032007

Fit to BaBar + Belle + LQCD

B (Be) = 1.49 (4) (7) x 10-4

B (Be) =1.41 (5) (7) x 10-4

B(Be)= 1.42 (5) (7) x 10-4


BaBar:

Belle:[arXiv:1012:0090]

Background suppression by cuts or Neural Net

Exclusive: |Vub| = (3.19 ± 0.14 ± 0.27) x 10-3 (V. Luth, J. Dingfelder)

Inclusive: |Vub| = (4.34 ± 0.13 ± 0.15) x 10-3 (V. Luth, [NS61CH06-Luth])

III Jornadas CPAN, Barcelona A. Oyanguren

Inclusive |Vub| Exclusive |Vub|

>2 difference since many years ago

New Physics contribution? (RH currents modification)

and Vub from B larger than for B

Semileptonic: Vub

Semileptonic: charm Charm semileptonic decays allow to measure form factors in the charm sector,

validating LQCD methods increase theory precision involving B decays trust LQCD calculations ensuring possible New Physics signs

Several charm semileptonic channels have been studied at BaBar from e+e- cc using a partial reconstruction technique:

DKe , DsKKe, D+Ke publishedDe (soon) can be related to Be access to Vub

Kronfeld plot, N. Simone: FERMILAB-CONF-10-594-T

Example: the leptonic constant fDs:

fDs puzzle: exp theo contribution from a charged Higgs?

>3 !?!


Quite precise form factor measurements from BaBar need LQCD improvements

Dse Dse D0K-e+

D+K*e+ D+K*e+ D+K*e+

214 fb-1

75 fb-1

348 fb-1

BaBar

BaBar BaBar

BaBarBaBar

BaBar

r2=A2(0)/A1(0) rv=V(0)/A1(0)

Exp

erim

ents


fK+(q2)

[PRD 76, 052005 (2007)]

A1(q2), A2(q2), V(q2)

[PRD 78, 051101(R) (2008)]

[PRD 83, 072001 (2011)]

Semileptonic: charm

A. Oyanguren 19

CP ViolationMotivation:

• CP violation discovered ~50 years agoobserving the decay KL → π+π-

• In the SM CPV arises from the not vanishingphase of the CKM matrix

• New Physics can induce additional FCNC and CP-violating phases

• Many observations of CPV processes in thelast decade in the beauty and strange sectors Global consistency with SM predictions

• No observation yet of CPV effects in thecharm sector

• No observation yet of CPV effects in thelepton sector

The CKM matrix

III Jornadas CPAN, Barcelona

A. Oyanguren 20

CP Violation in D decays


Motivation:

Direct CP violation in D decays arises through interference between:

In the SM is CKM suppressed O(10-3) or less: Vcs

New Physics can increase or reduce the effect:- e.g. additional CP phase from charged Higgs boson

Current experimental sensitivity O(10-3)

SCS decays are more likely to show the effect if present

[PRD 75, 036008 (2007)]

[PRD 51, 003478 (1995)][hep-ph/0104008 (2001)]

A. Oyanguren 21



Experimental method: Due to CPV in mixing in the kaon sector, the direct CP asymmetry for D+Ks+

At BaBar: signal yields from likelihood fit to m(+K0s), with selection based on a Boosted

Decision Tree with 7 variables: 807K D± signal events Measure

0 0

0 0

( ) ( )( ) ( )

s s

sC

sP

D K D KD K D K

A

=

2 2| | | | ( 0.332 0.006)%SMCPA p q= =

D DC FB

DP

D

N NA A A

N NA

= =

Forward-Backward asymmetryDetector charge asymmetry

Data-driven method to correct for A o Use tracks from e+e-(4S)BB

decays (isotropic in rest frame) to map the ratio of +/- detection efficiencies

o Offset on ACP +0.05%

[hep-ph/0104008 (2001)]is expected to be

A. Oyanguren 22



Use data-driven method to extract AFB, and ACP in bins of polar angle

( 0.44 0.13 0.10)%CPA =

Consistent with SM (-0.332±0.006)%

[PRD 83, 071103(R) (2011)]

At Belle D0 KS 0 , tag D flavour with the D* decay

[PRL106, 211801 (2011)]

D+Ks+

ACP = -0.28 0.19 0.10

A. Oyanguren 23

CP Violation in Ks


A deviation of the measured ACP from ACPSM would be a hint of New Physics

o e.g. an additional CP violating phase from an exotic charged Higgs boson

Can consider --Ks(>=00) since 0s are not expected to change the asymmetry

0 0

0 0

( ) ( )( ) ( )

s sCP

s s

K KAK K

=

2 2| | | | (0.332 0.006)%SMCPA p q= = [Bigi and Sanda, PLB 625, 47 (2005)]

[PLB 398, 407 (1997)]

Tree

uW

d

s d

K0

Search for direct CP violation in tau decays: --Ks

Motivation:

within the SM, due to the Ks presence, the asymmetry:

CP violation not yet observed in the lepton sector

is expected to be(same argument than for DKs decays)

A. Oyanguren 24

CP Violation in Ks



Reconstruct from continuum --Ks(>=00)

(up to 30s)

Reconstructed hadronic mass < 1.8 GeV (rejects qq bkg)

Electron and muon tags with p* > 4 GeV

(reduce bkg from non--pairs)

Invariant mass of the hadronic final state (00s)

Remaining background further reduced using information of: qq events: visible energy, number of neutral clusters, thrust, total transverse momentum Fake K0

s: displaced vertex, invariant mass, momentum and polar angle of the K0

s candidate

340k events

A. Oyanguren 25

CP Violation in Ks



Measured raw ACP value (after subtraction of qq background and non-K0s decays) has

to be corrected by:o Different nuclear reaction cross-section of K0 and K0 with material detector

o (0.14±0.03)% for e-tag, (0.14±0.02)% for -tago Errors include uncertainties from kaon-nucleon cross-sections and isospin

o Dilution from background modes including K0s

Result: ( 0.45 0.24 0.11)%CPA =

3 from the SM prediction

Source Fraction e-tag (%) Fraction -tag (%) SM expected ACP

--K0S(00) 78.4 ± 4.0 77.4 ± 4.0 (0.33±0.01)%

-K-K0S(00) 4.2 ± 0.3 4.0 ± 0.3 (0.33±0.01)%

--K0K0(00) 15.6 ± 3.7 15.7 ± 3.7 0

[Preliminary, submitted to PRD-RCarXiv:1109.1527] Systematic uncertainties

A. Oyanguren 26

CP Violation in Bc decays


Many such decays are dominated by bs penguinso Tree amplitudes subdominant in SMo Time-dependence and FSI (intermediate states)

allow to measure the CKM angles New Physics can change CP asymmetries, BRs and polarizations in BVV decays

Use kinematic constraints from beam energies

Event shape variables combined into a linear (Fisher) or non linear (NN) combination. Tagging (other “B”) information often used

Tree

Penguin

2*2/ 2ES Bsm p=

* / 2B sE E =

Apply selection to reject continuumas variable in ML fit

Motivation:


A. Oyanguren 27

CP Violation in Bc decaysAK= ACP(K0) - ACP (K)

Update the 2008 result with the full data set and improved reconstruction - ~2x more data

preliminary

AK = +0.112 ± 0.028 @4

Belle preliminary:

Direct CP violation difference in B K+- and K+0 at Belle

772 M BB


A. Oyanguren 28

CP Violation in Bc decays Direct CP violation difference in B0

K+-0 and B+ K+00 at BaBar


Perform ML fit with mES and NN, and for K+-0 only, also E and Dalitz plot For B0K+-0

o BF(B0K+-0) = (38.5 ± 1.0 ± 3.9)10-6

o ACP(K*+-) = -0.29 ± 0.11 ± 0.02o When combined with B0Ks+- :

For B+K+00

o First inclusive measuremento Measure resonances in a two-body fashiono 10 significance

Decay Nsignal BF(10-6) ACP

B+K+00 7427±518 16.2±1.2±1.5 0.06±0.06±0.04B+K*+0 1078±197 8.2±1.5±1.1 0.06±0.24±0.04B+f0(00)K+ 1186±241 2.8±0.6±0.5 0.18±0.18±0.04

B+cc0K+ 245±105 182±78±32±8 0.96±0.37±0.04

[PRD 83, 112010 (2011)]454x106 BB pairs

471x106 BB pairs

3.1 evidence for direct CPV

ACP(K*+-) = -0.24 ± 0.07 ± 0.02

ACP(K*+0) = -0.06 ± 0.24 ± 0.04

Preliminary

A. Oyanguren 29

Rare decays


Most of LFV and LNV Xchll BF ULs down by 1 order of magnitude (10-6)

B: Belle: fully reco tag + nothing in the signal side

BK: BaBar: semileptonic tag + K and 2 in the signal side [PRD 82, 112002 (2010)]

B(s+d): BaBar: semileptonic tag + 1 in the signal side: ACP = 0.056 ± 0.060 ± 0.018 (SM)

B: BaBar: upper limit (UL) lowered by a factor 2: BR< 3.2 x 10-7 @ 90% CL

D: BaBar: BR< 2.4 x 10-6 @ 90% CL

BR< 1.3 x 10-4 @ 90% CL (BaBar: BR< 2.2 x 10-4 )

Rare processes are quite sensitive to New Physics effects

x10-5

B: D

A. Oyanguren 30

Future: SuperB, Belle-II


Physics: Sensitivity B() ~ 10-9 , B()~10-10 , B(h)~10-10

Charm Physics: Precision CP parameters: (K) (~10-5), sensitivity FCNC: D(h) (~10-8)

B Physics: Precision BK (~20%), B (~ 4%), B (~ 5%), BD (~ 2%), ACP(bs) (~ 0.002), Vub (~ 2%)

SuperB, Frascati (Italy) Belle-II, Tsukuba (Japan) Two new facilities aiming to an integrated luminosity of 50-75ab-1 around 2020

Approved, major upgrade at KEK in 2010-14 SuperKEKB+Belle II, construction started

Approved, build a new tunnel, upgrade PEP-II and BaBar, quickly ramping up

A. Oyanguren 31

Summary


Summary B D(*)

Vub

Charm Semileptonic form factors

Improved measurements at BaBar

Despite the experimental and theoretical efforts the discrepancy between exclusive and inclusive measurements remains: what does it means? what don’t we understand?

Quite precise results from BaBar for DKe, Ds e, D K*e, form factors allow to check QCD methods: need LQCD improvements

BD0 and BD+ more than 5 significance R(D(*)) exceed by 1.8 the SM valuesfavors large tan

|Vub| excl. = (3.19 ± 0.14 ± 0.27) x 10-3

|Vub| incl. = (4.34 ± 0.13 ± 0.15) x 10-3


Introduction

VCKM =Vud Vus VubVcd Vcs VcbVtd Vts Vtb

B and charm semileptonic decays are tree level processes

New Physics contributions can only be seen: in semileptonic decays involving leptons:

by comparing CKM matrix elements in leptonic and semileptonic decays

coupling ~ mbm tan2

Note: Must control (by measuring) QCD effects (form factors)

involving CKM matrix elements:

B D()

Vub: Inclusive B Xu , exclusive B

Charm semileptonic decays

0.0406(13)

0.00389(44)

1.023(36)0.230(11)

PDG10


Charm sl decaysAnalysis procedure:

Partial reconstruction method; e+e- cc; only electrons

D* tag in case of DKe, no tag for Ds or D+ decays

Compute the D(s) direction from all tracks signal tracks

q2 and angular distributions: kinematic fit with signal tracks momenta and missing energy information

Background suppression using event shape and topological variables

Background control, test of the analysis technique and the normalization are obtained from hadronic data samples (ex: DK, D K)



(isospin)

(isospin)

Fit results (preliminary):

large signal significance (> 5) for all channels

Systematics (preliminary): - Selection cuts: ~6%(D*),~9%(D) - D** fitted in D(*)0 samples: ~4%(D*), ~5%(D)


Summary of Vub measurements:B Xu

Exclusive: (V. Luth, J. Dingfelder)

Inclusive:

|Vub| = (3.19 ± 0.14 ± 0.27) x10-3

|Vub| = (4.34 ± 0.13 ± 0.15) x 10-3(V. Luth, [NS61CH06-Luth])



Leptonic decays


Vub exclusive: BaBar combined

(fits from J.Dingfelder and V. Luth)

BaBar combined result:

BaBar Fit to BGL

BaBar fit to BGL including Lattice data points

(B : LCSR q2 < 12GeV2, LQCD q2 > 16GeV2)

LCSR Lattice

Small event overlap of B0- (<1%) Uncorrelated statistical uncertainties Highly correlated systematics

Vub exclusive: B

BaBar data samples: 423 fb-1 , 349 fb-1

Analyses procedure:

Untagged analyses (high stat., more bkg.), e +

Loose reconstruction from full event (p = pbeams - pi)

2D or 3D fit E = (PBPbeams-– s /2)/2 , mES = [(s/2 + pBpbeams- )2 /E2

beams - p2B]½

q2 = (p + p)2 = (pB- p)2

q2 in 12 or 6 bins

PRD 83 (2011) 052011

to extract the signal yield

PRD 83 (2011) 032007

Background suppression by cuts or NN


Charm sl decaysAnalysis procedure:

Partial reconstruction method; e+e- cc; only electrons

D* tag in case of DKe, no tag for Ds or D+ decays

Compute the D(s) direction from all tracks signal tracks

q2 and angular distributions: kinematic fit with signal tracks momenta and missing energy information

Background suppression using event shape and topological variables

Background control, test of the analysis technique and the normalization are obtained from hadronic data samples (ex: DK, D K)


Fit results:

Vub extraction:

BNLP: [Bosch et al. , PRD 72 (05) 073006]

DGE: [Andersen et al. , JHEP 0601 (06) 097]

GGOU: [Gambino et al., JHEP 0710 (07) 058]

ADFR: [Aglietti et al., EPJ. C 59 (09) 831]

Most precise result : 2D fit q2-Mx

for p* > 1 GeV Fit for BXc bkg and BXu signal yields

B Xu1441 102

dataXuXc

|Vub|= (4.31 0.25exp 0.16theo )10-3

Average:

B Xu B Xu

[to be submitted to PRD]


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