Hot Topics from BaBar Fabrizio Bianchi INFN, Torino (on behalf of the BaBar Collaboration)

Hot Topics from BaBarFabrizio Bianchi

INFN, Torino

(on behalf of the BaBar Collaboration)

Direct CP Violation in

(hep-ex/0407057)

Observation of and search for (ICHEP

08/917)

Search for the D*sJ(2632)+ observed by SELEX (ICHEP

11/916)

π K B0

000 K KB KK B

00

08/17/2004 F. Bianchi - ICHEP04 2

Direct CP Violation in π K B 0

Background-subtracted distribution for K+- (blue) and K-+ (red) decays

0

0

9

696

10

n B K

n B K

ππ

ππ

KK

KKCP nn

nnA

See Jinwei Wu talk in the CP session

009.0030.0133.0

/2s - E ΔE *B

Direct CP Violation @ 4.2

08/17/2004 F. Bianchi - ICHEP04 3

Study of KKB,KKB0000

KKB000 KKB

00

0Kb

tcu ,,

d d

dss

0K

b

u

dtcu ,, s

su

0K

K

R. Fleischer and S. Recksiegel, hep-ph/0408016

Pure b d penguin.

Can be correlated with B system.

08/17/2004 F. Bianchi - ICHEP04 4

Data sample and B reconstruction

• Data Sample: • 227 million B pairs collected at the Y(4S)

energy • 16 fb-1 of data recorded 40 MeV below the

Y(4S)

• B candidates are reconstructed combining a Ks candidate and a charged track or two Ks candidates

• well reconstructed tracks within the DIRC acceptance

• Ks candidates are reconstructed in the mode Ks

• |mKscand – mPDGKs| < 11.2 MeV (3.5 )

• Decay time significance > 5

08/17/2004 F. Bianchi - ICHEP04 5

Signal and sideband regions

•Two variables characterize a B candidate:

•We require:

•5.20 < mES < 5.29 GeV/c2

•|E| < 0.100 GeV ( )

•-0.115 < E < 0.075 GeV ( )

/2s - E ΔE *B *2

B*2BeamES pEm

000 KKB KKB

00

B background

signal

mES

(GeV/c2)

E

(GeV

)

08/17/2004 F. Bianchi - ICHEP04 6

Continuum Background Suppression

ContinuumBackground

Signal MCcut

Cosine of the angle between the sphericity axes of the B and of the rest of the event|cos(s)| < 0.8

Fisher Discriminant

i i

2*i

*i

*i )cos(θp1.27p0.600.53F

Signal MCContinuumBackground

Background from B decays is negligible

08/17/2004 F. Bianchi - ICHEP04 7

Likelihood Fit

PDF parameters determined from data and MC. Some free in the fit.

nsig and ACP from an Unbinned Likelihood with:

mES

E Fisher

c residual To separate K (only for Ks K+)

To discriminate against background

Cherenkov-anglemeasured by the DIRC

20441 Ks h+ candidates

1939 Ks Ks candidates

p(GeV/c)

c(r

ad

)

08/17/2004 F. Bianchi - ICHEP04 8

: results

@90%CL10 2.35

100.11)(1.46BR

31441n

6-

6-

sig

0.530.46

KKB,KKB0000

000 KKB

KKB00

σ 4.5:ceSignifican

100.13)(1.19BR

2.023n60.40

0.35

7.76.7sig

First observation of this mode

08/17/2004 F. Bianchi - ICHEP04 9

Search for D*sJ(2632)+

KD0

KD0

ηDs

Even

ts/1

0

MeV

/c2

Even

ts/5

M

eV

/c2

SELEX reported the discovery of a heavy state decaying to D+s and D0K+ in 9.9 x

10-9 - interactions on a set of thin foil targets of Cu or diamond collected at the 600 GeV hyperons beam at FNAL. (hep-ex/0406045, submitted to PRL)

m = M(K+K-)– M(K+K-+) MeV/c2 m = M(K-K+)– M(K-+) MeV/c2

08/17/2004 F. Bianchi - ICHEP04 10

The Ds sample

BaBar: ~196,000 Ds in 125 fb-1 SELEX: ~550 Ds

m(K+K-+) GeV/c2

even

ts/1

.3 M

eV

/c2

m(K+K-+) GeV/c2

08/17/2004 F. Bianchi - ICHEP04 11

The sample ~3900 in Ds

+ sample at BaBar total inclusive at SELEX635087

even

ts/5

MeV

/c2

mGeV/c2 mMeV/c2

even

ts/4

MeV

/c2

08/17/2004 F. Bianchi - ICHEP04 12

Correlated production of Ds+

and

• There is production in events with Ds

• To check if they are

correlated, we look for an

excess in the overlap

region.

• Excess after 2D sideband

subtraction: 75 1102 η) N(Ds

mGeV/c2m

GeV

/c2

m(K+K-+) GeV/c2

m(K+K-+) GeV/c2even

ts/2

.6 M

eV

/c2

even

ts/1

0 M

eV

/c2

08/17/2004 F. Bianchi - ICHEP04 13

Ds+mass spectrum

BaBar sees no D*sJ (2632)+ in 125 fb-1

Correlated Ds+

spectrum

after background

subtraction

ηDs

SELEX

2s GeV/c η)m(D

Even

ts/1

0

MeV

/c2

Even

ts/1

0

MeV

/c2

m = M(K+K-)– M(K+K-+) MeV/c2

08/17/2004 F. Bianchi - ICHEP04 14

D0K+ mass spectra

BaBar sees DsJ(2573)+ and

no DsJ(2632)+ in 125 fb-1

DsJ(2573)+

DsJ(2632)+

p* > 4.0 GeV/c

M(D0K+) GeV/c2

Even

ts/5

M

eV

/c2 Even

ts/5

M

eV

/c2

SELEX

m = M(K-K+)– M(K-+) MeV/c2

08/17/2004 F. Bianchi - ICHEP04 15

D*+Ks mass spectrum

BABAR sees Ds1 (2536)+ and

no DsJ (2632)+ in 125 fb-1

p* > 4.0 GeV/cDs1

(2536)+

DsJ

(2632)+

D*+Ks) – m(D*+) GeV/c2

Even

ts/2

.5

MeV

/c2

08/17/2004 F. Bianchi - ICHEP04 16

Summary

CL%90@10 2.35)KK BR(B -60

100.13)(1.19)KKBR(B 60.400.35

000

No evidence of D*sJ(2632)+ in Ds

+, D0K+, D*+Ks

009.0030.0133.0π KA Direct CP Violation in @ 4.2

First Observation @ 4.5

π K B 0

Backup Slides

08/17/2004 F. Bianchi - ICHEP04 18

PID at BaBar

• At BaBar p of particles from 2-body B decays is between 1.5 and 4.5 GeV/c

• PID uses Cherenkov-angle cmeasured by the DIRC

• K- separation measured from D*+ D0 (D0 K- +)

08/17/2004 F. Bianchi - ICHEP04 19

PDF Parameterization

Variable Signal PDF Background PDF

mES Gaussian Argus

E Double Gaussian Poly2

Fisher Bifurcated Gaussian Double Gaussian

c residual Double Gaussian Double Gaussian