L lista infn sezione di napoli
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L.Lista INFN Sezione di Napoli. Results of B A B AR experiment on CP violation and B physics. Outline. Experimental set-up CP asymmetries sin2 b sin2  eff B Mixing and lifetime Rare B decays Conclusions (Many topics will be skipped). (4S).

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L lista infn sezione di napoli

L.ListaINFN Sezionedi Napoli

Results of BABAR experiment on CP violation and B physics

Luca Lista


Outline

Outline

  • Experimental set-up

  • CP asymmetries

    • sin2b

    • sin2eff

  • B Mixing and lifetime

  • Rare B decays

  • Conclusions

    (Many topics will be skipped)

(4S)

Luca Lista


The pep ii b factory

center of mass energy  MU(4S) =10.58 GeV/c2

bg= 0.56

PEP-II at SLAC

Low Energy Ring

[e+, 3.1GeV]

BaBar

High Energy Ring

[e-, 9.0GeV]

The PEP-II B-Factory

Luca Lista


Integrated luminosity

Integrated Luminosity

32 Million Y(4S) decays recorded

  • BaBar recorded:

    • 37.7fb-1

    • 4.05 fb-1 off peak

  • Top luminosity:

    • 3.4x1033 cm-2s-1

    • Design:

      • 3x1033 cm-2s-1

Luca Lista


The babar detector

Electromagnetic

Calorimeter

6580 CsI(Tl) crystals

1.5T solenoid

e+

DIRC (PID)

144 quartz bars

11000 PMTs

Drift Chamber

40 axial stereo

layers

e-

Instrumented Flux Return

19 iron / 18-19 RPC layers

Silicon Vertex Tracker

5 layers, 2-sided Si strips

The BaBar detector

Luca Lista


The unitarity triangle

A=(,)

B=(1,0)

C=(0,0)

The Unitarity Triangle

  • Unitarity relations on matrix elements lead to a triangle in the complex plane

  • Quark mixing is described by the CKM matrix

1

Luca Lista


Cp violation at asymmetric b factory

B0

fCP

B0

t

d

b

B0

B0

W

W

t

b

d

@Dt=0

B0

B0

F-

F+

Dt(ps)

CP violation at asymmetric B factory

CP violation via mixing interference

fCP eigenvalue

 e-2ib

For “golden” bccs modes:

Luca Lista


Sin2 b improvements w r t run i

sin2b: Improvements w.r.t. run I

  • More data!

  • Added new modes

    • c1KS, J/K*0

  • Improved reconstruction efficiency

    • Improved tracking

    • ~ +30% KS reconstruction eff.

  • Improved vertex resolution

    • New alignments

    • More elaborated vertex algorithm

  • Optimized KL selection taking into account the background CP asymmetry

    • Maximize (S+AB/ASB)2/(S+B), not S2/(S+B)

Luca Lista


All sin2 b cp modes

All sin2b CP modes

hCP = +1

IFR

KL momentum not measured

DE determined from B mass

and beam energy constraints

B0J/K0L

N=129

(65% pur.)

hCP = -1

B0J/K0S

B0(2S)K0S

B0cK0S

N=724

EMC

N=128

(56% pur.)

Golden modes: ~30% higher efficiency than run 1: KS efficiency improved

Luca Lista


Fully reconstructed b flavor modes

Fully reconstructed B flavor modes

  • Cabibbo favored decays:

    • B0D(*)-p+/r+/a1+

    • B+ D(*)0 + , J/K+, (2S)K+

Luca Lista


Mixing and cp asymmetry of b 0 b 0

B01 partially reconstructed

flavor tagged

B02 fully reconstructed

D*+  - or J/K0S

e-e+

B1 = B0

B1 = B0

unmixedB0 B0

Dz

Mixing and CP asymmetry of B0/B0

CP modes:FCP(Dt)  e-|Dt|/tB ( 1 hCPsin2b. sin Dmd Dt )

Flavour specific modes:

Fflav(Dt)  e-|Dt|/tB ( 1 cosDmdDt )

mixedB0B0 or B0B0

Luca Lista


Imperfect tagging and resolution

Imperfect tagging and resolution

D = 1-2w = dilution, w = wrong tag fraction

R(Dt)= resolution function

Imperfect

tagging

Imperfect

resolution

B0

B0

e-|Dt|/tB (1hCP sin2b

 sin Dmd Dt)

e-|Dt|/tB (1hCP Dsin2b

sin Dmd Dt)

e-|Dt|/tB (1hCP Dsin2b

 sin Dmd Dt)  R(Dt)

unmixed

mixed

e-|Dt|/tB (1cos DmdDt)

e-|Dt|/tB (1 Dcos Dmd Dt)

e-|Dt|/tB (1Dcos DmdDt)

 R(Dt)

Luca Lista


Fitting procedure

Fitting Procedure

  • Unbinned maximum likelihood fit

  • Mistag and resolution: empirical distribution

    • fitted from data

  • fixed in the fit:

    md = 0.472 ps-1 (was extracted from the same fit in Run-I analysis)

    tB = 1.548 ps

Separate for Run I & II

Largest correlation

With sin2b: 13%

Luca Lista


Flavor misid measurement

Flavor misid. measurement

e

w

D=1-2w

Q=e(1-w)2

s(sin2b) 1/(Q)

Neural network mainly to

recover unidentified leptons

and use soft pions from D*

Luca Lista


Sin2 b result

sin2b result

sin2b = 0.59 ± 0.14stat ± 0.05syst

Luca Lista


Comparison of different samples

Comparison of different samples

Submitted to

Phys. Rev. Lett.

On July 5 2001

Luca Lista


Unitarity triangle

1s

2s

Unitarity triangle

sin2b =

0.59 ± 0.14stat ± 0.05syst

Luca Lista


Search for direct cp violation

Search for direct CP violation

  • Assuming more than one amplitude dominate the decay:

    || may be 1

  • Only CP = -1 used

    • High purity, no assumption needed on CP of the background

    • No evidence found (none expected from SM)

||=0.93 ± 0.09 ± 0.03

Luca Lista


L lista infn sezione di napoli

Systematic errors

  • 0.03 from vertexing

  • 0.03 from tagging

  • 0.02 from background

  • Total 0.05

Luca Lista


D m d measurement

Dmdmeasurement

preliminary

Dmd=

0.519 ±0.020stat±0.016syst ps-1

Run I only

Luca Lista


Lifetime results

Lifetime results

B

B0/B0

background

Dt (ps)

Dt (ps)

t0 = 1.546  0.032(stat)  0.022(syst) ps

t  = 1.673  0.032(stat)  0.022(syst) ps

t0 /t = 1.082  0.026(stat)  0.011(syst)

common resolution

Luca Lista


Charmless hadronic decays

u

u

d

d

d

d

Charmless Hadronic Decays

  • Physics motivations

  • Significant penguin contribution

  • Direct CP violation studies

  • Measurement of  from time-dependent asymmetry + isospin analysis

  • Possible field for new physics…

}p-(K-)

Vud(s)

d(s)

W-

Vub

{

b

}p+

u

B0

Cabibbo suppressed tree diagram

}p-(K-)

Vtd(s)

W-

d(s)

Vtb

}p+

{

b

u

t

B0

Penguin diagram

Luca Lista


Two body branching fractions

Two body Branching fractions

control sample:

D*+D0, D0K-+

> 3 sigma

Run I only

p (GeV/c)

Luca Lista


Cp violation in b 0 sin2 a eff

CP violation in B0+-: sin2aeff

  • Neglecting penguin pollution:

    •  = f e-2i() = f e2i  C=0, S= sin2

  • Considering penguin diagrams:

    • ||  1

    • C  0, S= sin2eff = sin2  f (Penguin / Tree)

    • Extraction of sin2 requires the study of B000 and B000

      • Fitted simultaneously with branching fractions

      • Dilutions and time resolutions taken from sin2b fit

Run I + II

expected ~0.3

preliminary

ACP(K+p-) = -0.07  0.08  0.02

S =0.03 +0.53-0.56  0.11

C  =0.25 +0.45-0.47  0.14

Luca Lista


Radiative penguin b k

Radiative Penguin: B  K*

  • Sensitive to top quark couplings

    • CKM matrix elements Vtd,Vts

  • Sensitive to New Physics

    • SUSY, Charged Higgs

  • No CP asymmetry in the Standard Model (< 1%)

    • Possible sources beyond SM

Signal:

B0  K*0, K*0  K+-

Backgrounds:

e+e-  qq 

e+e-  qq  X 0

Luca Lista


B 0 k 0 yield and branching ratio

B0 K*0: yield and branching ratio

  • Nsignal = 139.2  13.1 events

  • Br(B0 K*0)= (43.9  4.1  2.7)  10-6

  • Br(B Kl+l-) < 0.6  10-6 (90% C.L.)

  • Br(B K*l+l-) < 25.7  10-6 (90% C.L.)

B0  K*0 K*0  K+p-

Luca Lista


B k b k

BK, BK*

  • Penguin dominated

Max Lik. Fit projections

  • B+K+=(7.7 +1.6-1.4  0.8)  10-6

  • B+p+<1.4  10-6(90% C.L.)

  • B+K*+ =(9.7 +4.2-3.4  1.7)  10-6

  • Possible measure of sin2b:

  • B0K*0 =(8.6 +2.8-2.4  1.1)  10-6

  • B0 K0 =(8.1 +3.1-2.5  0.8)  10-6

Luca Lista


Quasi 2 body and 3 body decays

Quasi 2-body and 3-body decays

B+p+ = ( 6.6+2.1-1.80.7 )  10-6

B0K0< 12 10-6

B+K+ = ( 70 85 )  10-6

B0K0=( 42+13-114 )  10-6

B+K*+ = ( 22.1+11.1-9.2 3.3 )  10-6

B0K*0= ( 19.8+6.5-5.61.7 )  10-6

B0K*0 p+< 28  10-6

B+0K+< 39  10-6

B+0p+< 39  10-6

B+K+p+p- < 54  10-6

B+p+p+p-< 22  10-6

B0p=( 49  13 +6-5 )  10-6

B0a0(980)p

Br(a0 p) = ( 6.7 +3.2-2.71.3 )  10-6

Potential for sin2a

First

Observation

Luca Lista


Search for direct cp violation1

Search for direct CP violation

Luca Lista


B d d k

B  D*D(*)K

  • Study of the bccs transition

  • Experimental inclusive estimate from from BDSX, (cc)X, CX, CX (ALEPH, CLEO)

    • Br(bccs) ~ 15.82.8 %

  • Theoretical calculation can’t determine this low value together with inclusive s.l. branching ratio (bcW)

    • Three-body B  DDK can contribute

  • Study of color suppressed modes (B+ D*+D*-K+)

Color suppressed

Color allowed

Luca Lista


B d d k1

B  D*D(*)K

  • Reconstructed decays:

    • D*+ D0p+

    • D*0 D0p0

    • D*0 D0g

    • D0 K-p+

    • D0 K-p+p0

    • D0 K-p+p-p+

    • D+ K-p+p+

  • Br(B0 D*+D0K+) = (0.280.070.05)10-2

  • Br(B0 D*+D*0K+) = (0.680.170.17)10-2

  • Br(B+ D*+D*-K+) = (0.340.160.11)10-2

    • First observation of color suppressed mode other than B  (charmonium)X

B0 (all modes)

NS = 18021

B+ (all modes)NS = 11715

B+ D*+D*-K+

NS = 8.23.5

Luca Lista


Conclusions

Conclusions

  • sin2 extracted from 37.7 millions of BB events

    sin2b= 0.59 ± 0.14stat ± 0.05syst

  • CP violation established at 4.1 level

  • First measurement of CP violation in B0

  • High precision measurements of mixing parameter and lifetimes

  • High precision measurements of B decays branching fractions

    • Many newly observed decays

  • Most of the results are still statistically limited

Luca Lista


Backup slides

Backup slides

Luca Lista


J k angular analysis

J/ K* angular analysis

J/ rest frame

K* decay plane

Channels withoutp0

f (costr, cosK*, tr) =

f1|A0|2 + f2|A|||2 + f3|A|2

+f4Im(A||* A) + f5Re (A0* A||)

+ f6Im (A0* A)

Channels withp0

  • L=0,1,2 waves

    • Both CP even and odd amplitudes are present

  • Measurement of sin2b is possible from angular analysis

Time dependent CP asymmetry dilution factor:

D =1 – 2|A|2 = 0.680.10

Luca Lista


B 0 d d

B0 D*+D*-

  • Cabibbo suppressed decay

  • A measurement in bccd of CP violating time-dependent asymmetry can be performed from angular analysis

    • Possible penguin contamination

  • Measurement of sin2b independent from B0J/K0S

    • Significant deviations from B0J/K0S measurement of sin2b may be indication of new physics

Tree diagram

Penguin contribution

  • Branching ration measurement of B  D(*)+D(*)-:

Luca Lista


B 0 d d1

Signal box

(38 events)

Background sample

(6.240.49 expected in signal box)

B0 D*+D*-

Br(B0D*+D*-) = (8.0  1.6  1.2)10-4

Luca Lista


Inclusive charmonium decays

J/ +-

J/ e+e-

p*J/ < 2 GeV/c

Inclusive Charmonium decays

c

J/, (2S), c

b

c

  • Inclusive J/branching ratio:

    Br(BJ/X) = (1.0440.013 0.028)10-2

    Br(BJ/X dir.) = (0.7890.010 0.034)10-2

  • Inclusive (2S)branching ratio:

    Br(B (2S) X) =(0.2750.020 0.029) 10-2

    • (2S)l+l-branching ratio:

      (2S)  e+e-(7.8  0.9  0.8)10-3

      (2S)  +-(6.7 0.8  0.7)10-3

  • Inclusive cbranching ratios:

    Br(B c1 X) = ( 0.378  0.034  0.026 )  10-2

    Br(B c1 X dir.)= ( 0.353  0.034  0.024 )  10-2

    Br(B c2 X) < 0.2110-2 @ 90% C.L.= ( 0.137  0.058  0.012 )  10-2

W-

B0, B-

s, d

X

d,

u

Br((2S)  J/p+p-)assumed from PDG

Luca Lista


Exclusive b decays

Exclusive B decays

  • Main motivation:

    • Channels are used for CP violation measurements

  • Kinematics selection:

    • Energy substituted mass

      • Independent on particle mass hypotheses

    • Energy difference in the center of mass

B0J/ 0

First observation:

B0c1 K*0

Luca Lista


J production in continuum

J/ production in continuum

  • First observation of J/ production in continuum

    • (4S) events with p*J/>2 GeV/c

    • Off-resonance events

Angular distribution1+A cos2q*

  • A (all E*) = 0.250.19

  • A (p*>3.5 GeV) l= 0.620.39

  • Color singles prediction:   0.8 pb A  –0.8,

  • NRQCD (c.o.) prediction:   2.8 pb 0.6<A<1.0

Luca Lista


Branching ratios results

Branching ratios results

RUN 1:

22.7 MBB

Luca Lista


D m d measurement the di lepton analysis

l+or l-

e-e+

l+or l-

N+–, –+ – N++, ––

Asymmetry

A(Dz)=

N+ –, –+ + N++, ––

Dz

Dmdmeasurement: the di-lepton analysis

Dmd= 0.499 ± 0.010 ± 0.012 ps-1

Luca Lista


Semileptonic b decays

Semileptonic B decays

  • Determine the sign of the B from a sample of ~14000 fully reconstructed B

    B0D(*)-+, D(*)-+, D(*)-a1+, J/K*0

    B- D(*)0+, J/K+, (2S)K+

  • Lepton identified in the decay of the other B

B+

B0

Mixing corrected

Luca Lista


B s b 0

bs, B0

mES for 0.6 <mhad < 2.0 GeV

  • Semi-exclusive study

    • Sum of exclusive modesK+np (n=1,2,3)

Branching ratio measurementcoming soon…

B0  

  • Theoretical exp.: ~ 10-8

  • Br(B0) < 1.7 x 10-6 90% C.L.

  • PDG: Br(B0 ) < 3.9 x 10-5 90% C.L. (L3)

Luca Lista


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