Recent results from the babar experiment
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Recent Results from the BaBar Experiment. Brian Meadows University of Cincinnati. Outline. The BaBar Experiment CP Violation B 0 – B 0 Mixing, Lifetime and sin 2  Measurements Charm at B A B AR A New Particle D 0 – D 0 Mixing : Summary. The BaBar Detector at SLAC (PEP2).

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Recent results from the babar experiment

Recent Results from the BaBar Experiment.

Brian Meadows

University of Cincinnati

Brian Meadows, U. Cincinnati.


Outline

Outline

  • The BaBar Experiment

  • CP Violation

  • B0 – B0 Mixing, Lifetime and sin 2 Measurements

  • Charm at BABAR

    A New Particle

    D0 – D0 Mixing:

  • Summary

Brian Meadows, U. Cincinnati


The babar detector at slac pep2

The BaBar Detector at SLAC (PEP2)

  • Asymmetric e+e- collisions at (4S).

  •  = 0.56 (3.1 GeV e+, 9.0 GeV e-)

1.5 T superconducting field.

Instrumented Flux Return (IFR)

Resistive Plate Chambers (RPC’s):

Barrel: 19 layers in 65 cm steel

Endcap: 18 “ “ 60 cm “

Brian Meadows, U. Cincinnati


Silicon vertex tracker svt

Silicon Vertex Tracker (SVT)

  • 5 Layers double sided AC-coupled Silicon

  • Rad-hard readout IC (2 MRad – replace ~2005)

  • Low mass design

  • Stand alone tracking for slow particles

  • Point resolution z » 20 m

  • Radius 32-140 mm

Brian Meadows, U. Cincinnati


Drift chamber

Drift Chamber

40 layer small cell design

7104 cells

He-Isobutane for low multiple scattering

dE/dx

Resolution

»7.5%

Mean position

Resolution

125 m

Brian Meadows, U. Cincinnati


Particle id dirc

Particle ID - DIRC

Detector of

Internally

Reflected

Cherenkov light

  • Measures Cherenkov angle in quartz

    • Photons transported by internal refl.

    • Detected at end by » 10,000 PMT’s

144 quartz bars

Brian Meadows, U. Cincinnati


Particle id dirc1

Particle ID - DIRC

It Works Beautifully!

Provides excellent K/ separation

over the whole kinematic range

Brian Meadows, U. Cincinnati


Particle id dirc2

Particle ID - DIRC

D0

D0

Brian Meadows, U. Cincinnati


Electromagnetic calorimeter

Electromagnetic Calorimeter

  • CsI (doped with Tl) crystals

    • Arranged in 48()£120()

    • » 2.5% gaps in .

  • Forward endcap with 8 more  rings (820 crystals).

Brian Meadows, U. Cincinnati


Pep ii performances

  • Off

  • On

PEP-II performances

Peak Luminosity 4.9 £ 1033 cm-2¢ s-1

  • 24 fb-1 in run 1

  • 70 fb-1 in run2

  • 10 fb-1 so far in run3

run3

Most analyses use ~88M BB decays (runs 1+2)

run2

(~12% off peak)

run1

Brian Meadows, U. Cincinnati


Cp violation

CP Violation

  • CP violation is manifest when a process involving particles occurs at a different rate to that with anti particles:

    (B ! f)  (B ! f)

  • Under CP transformation, amplitudes A have weak phases  that reverse sign but strong ones  that do not

    A = a exp{i(+ )} ! A = a e{i(- )}

  • If two amplitudes A1 and A2 contribute to a process, the rates are:

     = |A1+ A2|2 = a12+ a22+ 2a1a2 cos( + )

     = |A1+ A2|2 = a12+ a22+ 2a1a2 cos( - )

  •  (CP Violation)when

     (´2-1)  0 and (´2-1) 0.

CP

CP violation is maximum when a1 = a2 !

Brian Meadows, U. Cincinnati


Cp violation in the standard model

J=Vqq’ q’  (1+5) q

q’

q

W

CP Violation in the Standard Model

  • The phase in the CKM quark mixing matrix can give rise to CP Violation.

    • CKM imparts a phase to weak currents

      that cannot be removed by re phasing

      the quark fields.

  • Interference between a tree and a penguin process can give direct CP Violation

    but information on strong phases is required to interpret it.

  • Decays of B0 to CP eigenstates f accessible also to B0 can occur directly or through mixing.

Allows interpretation without knowing strong phases

Brian Meadows, U. Cincinnati


Mixing induced cp violation

f

B0

Mixing

B0

Mixing Induced CP Violation

  • If final state f is accessible for both B0 and B0 decay then mixing will interfere with direct decays

  • If f is a CP eigenstate, the decay

    amplitudes <f|T|B0> and <f|T|B0> have:

    • identicalstrong phases

    • identical weak phases, but with opposite signs

    • the same magnitudes.

  • So the CP violation is maximized.

  • CP violation has a time structure emanating from B0 mixing

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

dN/dt/ e - |t|/£ [1 §Ccos(mt) ¨S sin(mt)]

C = (1 - |f|2) / (1 + |f|2)

S = Im{ f }/ (1 + |f|2)

  • In the SM for b!ccs decays:

    • f = exp{2i}

    • AND no Penguin contributes

Mixing

Decay

Interference between two direct decay modes such as P and T

Interference between mixing and decay.

 is one of the angles in a unitarity triangle !

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

d s b

u

c

t

The Unitarity Triangles

(K system)

d•s* = 0

(Bs system)

s•b* = 0

(Bd system)

d•b* = 0

These three triangles (and the three triangles corresponding to the rows) all have the same area. A nonzero area is a measure of CP violation and is an invariant of the CKM matrix.

apply unitarity constraint to pairs of columns

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

d s b

u

c

t

The Usual Unitarity Triangle

Vtb*Vtd

Vub*Vud

Vcb*Vcd

Orientation of triangle has no physical significance. Only relative angle between sides is significant.

apply unitarity constraint to these two columns

Brian Meadows, U. Cincinnati


The usual unitarity triangle

d s b

u

c

t

(, )

Vtb*Vtd

Vcb*Vcd

Vub*Vud

Vcb*Vcd

(1, 0)

(0, 0)

The Usual Unitarity Triangle

apply unitarity constraint to these two columns

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

p+

B0 / B0

e+

e-

—

B0 / B0

e ±, m ±, K± tag

Dz =c t

Dz ~ 255 mm for PEP-II: 9.0 GeV on 3.1 GeV

~ 200 mm for KEKB: 8.0 GeV on 3.5 GeV

The Asymmetric-Energy B Factories

(4S)

Brian Meadows, U. Cincinnati


D t distributions with no experimental effects

Dt distributions with NO experimental effects

Flavor states sorted by mixing status

CP states sorted by B tag flavor

B0B0 or B0 B0

Btag= B0

Btag= B0

B0B0 or B0 B0

B Mixing

dN exp(–|Dt|/tB) ( 1 ± cos(DmDt) )

CP violation

dN exp(–|Dt|/tB) ( 1 ± sin2b sin(DmDt) )

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

unmixed – mixed

unmixed + mixed

Asymmetry =

~ (1 – 2w)

 (1 – 2w) cos(DmdDt)

~ p / Dmd

Perfect flavor tagging and time resolution

Realistic mis-tag and finite time resolution

- unmixed

- unmixed

- mixed

- mixed

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

B0 – B0 Mixing

md , B andsin 2

Measurements

Brian Meadows, U. Cincinnati


Increase in precision of b lifetimes and mixing frequency

Increase in precision of B lifetimes and mixing frequency

B0 Lifetime (ps)

1.548  0.032

1.542  0.016

Ratio of B+ to B0 Lifetime

1.060  0.029

1.083  0.017

B0 Mixing Frequency ( x 1012 s-1)

0.472  0.017

0.489  0.009

PDG2000

18 measurements

12 measurements

10 measurements

PDG2002

New measurements:

3 B Factory 2 LEP

2 B Factory 1 LEP

3 B Factory 1 LEP

  • Uncertainties limited by:

    • knowledge of t resolution function

    • B (for mixing).

  • BABARMeasured both together using the copious B0!D*lmode.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

hep-ex/0207071 (ICHEP)

Dmd=0.492±0.018±0.013ps-1

+0.024-0.023

B0=1.523±0.022ps

correlation coefficient (m, B0) = -0.22

  • In a few years we might:

  • anticipate < 1% uncertainty in B0 mixing

  • possibly measure 

  • (test CPT limits directly).

Brian Meadows, U. Cincinnati


Sin 2

Sin 2

Primary result comes from

charmonium decay modes.

Simultaneously fit flavour specific modes to determine flavour tagging quality and  resolution.

Additional information from modes which include penguin (P) in addition to tree (T) modes.

Vtb*Vtd

Vcb*Vcd

Brian Meadows, U. Cincinnati


Charmonium modes for sin 2

Charmonium Modes for sin 2

b

c

, c, c

One dominant decay amplitude !theoretically clean.

(Penguin has same phase!)

c

B0

s

KS , L

d

d

Both BABAR and Belle use six charmonium modes:

BJ/Ks0, Ks0p+p-, p0p0

BJ/KL0

B(2S) Ks0

Bc1Ks0

BJ/K*0, K*0 Ks0

BcKs0

Simultaneously measure self tagging modes to determine  and (t).

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Sin2b Data Samples in BABAR

Bflav

Mixing sample

ccKs modes

B0D(*)-p+/ r+/ a1+

Ntagged= 23618

Purity= 84%

  • Data

  • Data

Signal

J/y KL

J/y Bkg

Fake J/y Bkg

(MeV)

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

hep-ex/ 0207042 (PRL)

Ks modes

KL modes

81 fb-1 (88 M BB)

2641 tagged events with Dt measured (78% purity; 66% tagging e)

sin2b = 0.741  0.067  0.034 || = 0.948  0.051  0.030

effective tagging eff: e=(28.1  0.7)%

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Golden modes with a lepton tag

The best of the best!

Ntagged = 220

Purity = 98%

Mis-tag fraction 3.3%

sDt 20% better than other tag categories

background

sin2b = 0.79  0.11

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

sin2b measurement history

  • “Osaka 2000” measurement

  • (hep-ex/0008048)

    • Only J/y Ks and y(2s) Ks.

  • 1st Paper (PRL 86 2515, 2001)

    • Added J/y KL.

    • Simultaneous sin2b and mixing fit.

  • 2nd Paper (PRL 87 201803, 2001)

    • Added J/y K*0 and c Ks.

    • Better vertex reconstruction.

    • Better SVT alignment and higher Ks efficiency for new data.

  • Winter 2002 (hep-ex/0203007)

    • Improved event selection.

    • Reprocessed 1st 20 fb-1.

  • e) Current measurement (hep- ex/0207042, PRL)

    • Improved flavor tagging.

    • One more CP mode: hcKs.

(compiled by Owen Long)

d

e

c

b

a

Brian Meadows, U. Cincinnati


Decrease in statistical uncertainty

Decrease in Statistical Uncertainty

  • Curves represent 1/sLdt.

  • Improvements in statistical uncertainty due to

  • adding new B decay modes,

  • improved vertex reconstruction,

  • improved SVT alignment,

  • improved tagging performance.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

hep-ex/0208025, sub to PRD RC

Belle

78 fb-1 (85 M BB) 2958 events (81% purity)

effective tagging efficiency: e=(28.8  0.6)%

sin2b = 0.719  0.074  0.035|| = 0.950  0.049  0.025

Brian Meadows, U. Cincinnati


Constraints on upper vertex of unitarity triangle from all measurements except sin2 b

Constraints on upper vertex of Unitarity Triangle from all measurements EXCEPT sin2b

b

Regions of >5% CL

A. Höcker, H. Lacker, S. Laplace, F. Le Diberder, Eur. Phys. Jour. C21 (2001) 225, [hep-ph/0104062]

Brian Meadows, U. Cincinnati


World average sin2 b 0 78 0 08

World Average sin2b = 0.78  0.08

The Standard Model (and the CKM paradigm, in particular) wins again … at least at the current level of experimental precision, in this decay mode.

Brian Meadows, U. Cincinnati


B 0 k s

s

s

s

t

t

d

Other studies of sin2

B0Ks

b

s

s

b

s

B0

s

B0

K0

K0

d

d

d

  • Pure penguin !

  • time-dependent asymmetry in B0Ks measures sin2.

  • direct charge asymmetry in B+K+ sensitive to new physics.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

B0Ks samples

51 signal events

hep-ex/0207070 (ICHEP2002)

+0.52

- 0.50

sin2b = -0.19  0.90

  • c.f. world average: sin2 = 0.73 ± 0.06

  • >2 difference.

  • (over) stimulating theoretical interest.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Charm Physics

Brian Meadows, U. Cincinnati


Charm at the b a b ar b factory

Charm at the BABARB Factory?

  • Cross section is large

    Present sample of 91 fb-1 sample contains

  • Compare with earlier charm experiments:

    • E791 - 35,400 1

    • FOCUS - 120,000 2

    • CDF - 56,320

  • Approximately 1.12 £ 106 untagged

    D0!K-+ events

1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) 32.

2. Focus Collaboration, Phys.Lett. B485 (2000) 62.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

A New Ds State .. or?

Brian Meadows, U. Cincinnati


A new narrow resonance

A New Narrow Resonance

  • A striking signal observed in the Ds+0 system.

    • Signal clearly associated with both Ds+ and 0

    • Is not a reflection of any other known state (MC)

D §

Ds§

0

Brian Meadows, U. Cincinnati


A new narrow resonance1

There are over 1500 events in the signal.

The resonance has width comparable with the mass resolution in this system.

It is evident in two different topologies

a)D§s!K§ K¨ §

b) D§s!K§ K¨ §0

Within a) it is seen in both K*K and § channels consistently.

Generic MC test shows it is not a reflection of any known state.

A New Narrow Resonance

“Ds(2317)”

Ds1(2112)

p* > 3.5 GeV/c

p* > 3.5 GeV/c

Ds1(2112)

Brian Meadows, U. Cincinnati


A new narrow resonance2

A New Narrow Resonance

Ds1+(2112)

  • There is no significant decay of the Ds (2317) resonance to Ds+ at the present level of statistics.

  • Nor to Ds1+(2112) .

  • A kinematic enhancement at 2460 MeV/c2 results from overlap if Ds(2317) and Ds(2112).

    (However, Ds(2317) is not a kinematic reflection from effect at 2460 MeV/c2).

Ds+

Ds+ 

Ds1(2112)

Ds+ 0

Ds1(2112)0

Suggests a JP = 0+ assignment

Brian Meadows, U. Cincinnati


So what is it

… so what is it?

  • Both the Godfrey-Isgur-Kokoski and Di Pierro-Eichten* models predict a JP = 0+Ds level at a mass of ~2.48 GeV, having width in the range 270 to 990 MeV and prominent decay to D 0K.

  • Since the state observed is below DK threshold, it decays in an I spin violating mode.

  • These and other theoretical models have made mass predictions correct to ~ 10 MeV/c2 in all other cases for B as well as D mesons.

  • Perhaps this is the charm analogue of the a0(980) instead !!

*PRD 64, 114004 (2001)

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

D0 – D0 Mixing

Brian Meadows, U. Cincinnati


D 0 mixing with cp violation

D0 Mixing with CP Violation

  • Parameters used to describe mixing are

    x=(m1-m1)/ ; y=(1-2)/2 where  = (1+2)/2

    m1,2 and 1,2 are mass and width of mass eigenstates.

  • Mass eigenstates D1,2 are related to flavour eigenstates

  • For decay D (D) !f (f) as in B decays:

    |f|  1implies CP violation in mixing;

    Imf0implies CP violation in interference between mixing & decay

Brian Meadows, U. Cincinnati


D 0 mixing with cp violation1

D0 Mixing with CP Violation

  • Most standard model estimates for x and y are . 10-3.

  • So mixing rate RM = (x2+y2)/2» 10-6

    • Beyond experimental observation

    • Observation of mixing, especially |x|>|y|, could be evidence for new physics

  • CP violation in mixing would be sure sign of new physics.

  • New particles could

  • increase mixing

  • introduce phase in

  • decays.

Brian Meadows, U. Cincinnati


Mixing parameters from ratio of lifetimes

Mixing Parameters from Ratio of Lifetimes

  • D0 decays are ~ exponential. Lifetimes () depend on CP of final state.

    Previous analyses have measured:

    .

  • If CP violation occurs !

    Different lifetimes for D0 (+) and D0 (-) decays to CP even states.

  • We define and measure two NEW quantities (Y and Y):

    Y´0/<> - 1 Y´ A0 / <>

    [ <> = (+ + -) / 2 A = (+ - -) / (+ + -) ]

    If direct CP violation absent in decays, KK or  modes can be averaged.

for D0! CPmixed(K-+)

Useful if

|f|=1

and Im f=0

for D0! CPeven(K-K+ or -+ )

Brian Meadows, U. Cincinnati


Fit results

Fit Results

  • The fit uses all the data -

    Events within 15 MeV/c2 of D0 mass shown here.

  • Background estimated from mass and lifetime fits.

  • Statistical uncertainty small, e.g. for K-+ it is »0.9 fsec (»0.5% in y).

Brian Meadows, U. Cincinnati


Comparison with earlier results

Comparison with Earlier Results

Published (23.4 fb-1)

Moriond 2002

This Analysis

Also Y = - (8 § 6 stat. § 2 syst.) £ 10-3

Brian Meadows, U. Cincinnati


D 0 mixing from wrong sign decays

D0 Mixing from Wrong Sign Decays

  • Wrong sign (WS) decays D0! K+- can occur directly DCS or through mixing followed by the right sign (RS) CF decay:

  • WS decays are not exponential:

  • To search for CP violation, this distribution is measured for D0 and D0 separately to determine all the three terms.

DCS

CF

Mixing

Mixing

DCS

Interference

units of 0

Brian Meadows, U. Cincinnati


Fits with mixing

Fits with Mixing

  • Fit allowed x’ 2<0. Central values for D0, D0 and joint sample fits gave x’ 2<0.

  • 95% contours are determined using toy MC samples at each point on the contour (frequentist approach).

  • (x’ 2§, y’§) points on separate D0 and D0 contours are combined in pairs to determine (x’ 2, y’) on 95% CPV contour.

  • Systematic uncertainties are added in quadrature to distance from best fit to data.

Best fit

(x’ 2=0)

Best fit

(x’ 2 free)

no CPV

Brian Meadows, U. Cincinnati


Limits on d 0 mixing and cp violation

Limits on D0 Mixing and CP Violation

Comparison of RWS values:

BaBar

Brian Meadows, U. Cincinnati


Three body decays of d mesons

Three Body Decays of D Mesons

  • Three body modes are also to be studied.

  • The Ks0+- channel could contribute to mixing studies

    • D0 is tagged from D* so CF decay makes K0 . DCS or mixing make K0 .

    • These interfere and it may be possible to determine + from Dalitz plot.

  • In any case, it contains much physics - a real challenge to fit well.

K*(890) ! K0+

15,753 events

23 fb-1

K*(890) ! K0- ?

Brian Meadows, U. Cincinnati


Summary of b a b ar results shown

Summary of BABAR Results Shown

  • Measurements of sin 2 in charmonium channels agree well with the SM.

  • A challenge to the SM could yet come from other channels.

  • A new strange-charm state has been found. It’s mass is ~170 MeV/c2 below current expectations of the quark model.

    ! It could be an exotic state.

  • No signal for mixing in the D0 system at » 5 £ the rate predicted by the SM is yet observed.

  • In this range, searches should to be sensitive to CP violation effects expected from new physics.

  • BaBar’s measurement is not systematically limited. With 500 fb-1 integrated luminosity expected by 2006, the standard model predicted rate may be observable.

  • In the meantime, new physics could show up.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Back up Slides

Brian Meadows, U. Cincinnati


B 0 k s1

hep-ex/0207033, PLB

B0 ’ KS

Belle (45M B pairs)

  • Penguin mediated.

  • Sensitive to new physics.

+0.07 -0.08

sin2b = 0.28  0.55

Many other studies of B (’)K (*) are being aggressively pursued.

Challenge to theoretical models to explain relative rates.

*

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

B0

B0

88M BB

Measurement of “sin2b” in bccd decays: D*D*+ and D*D+

c

b

t

d

D(*)-

D(*)-

c

d

b

c

c

D(*)+

D(*)+

d

d

d

d

  • Weak phase for tree decay is same as for bccs but watch out for penguins!

  • D*D* is vector-vector decay (L=0,1,2) so mix of CP=+1 and –1.

D*D*

signal yield = 126±13 evts

D*D*

Im(l) = 0.31 0.43  0.13

|l | = 0.98  0.25  0.09

  • If penguins are negligible, Im(l)=-sin2b and |l |=1.

  • 2.7 s change in lnL.

  hep-ex/0207072 (ICHEP2002)

CP asymmetries in D* D+ have also been studied in BABAR.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

(bccd) mode B0J/yp0

Nfit= 40±7

hf = + 1

Tree: ~ O(l3)

same weak phase as bccs

~49 eventsA = -0.25  0.35  0.06-S = 0.93  0.49 0.08

Penguin: ~ O(l3)

adds additional weak phase

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

“sin2a”

Vtb*Vtd

Vub*Vud

a

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

B0

B0

CP Violation in B0 p+p-

u

b

t

d

p-

p-

u

d

b

u

u

p+

d

d

p+

d

d

|P/T| and relative strong phase d are unknown but can, in principle, be determined from an isospin analysis that requires measuring BF for B0p+p-, B0p+p-, B±p±p0, B0p0p0, and B0p0p0.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

A2

A2

A0

Isospin Analysis

  • The 3 B0, B+pp amplitudes proceed via 2 isospin amplitudes: A0,A2

  • CP-conjugated decays B0, B- proceed via A0, A2

  • Measurements of 5 time-averaged rates fix lengths of each side but not relative orientation, which comes from time-dep analysis.

A(B0p0p0)

A2

A0

A(B+p+p0)

2aeff from time-dependent p+p- analysis

A2

A(B0p+p-)/2

A(B0p+p-)/2

A2

2a

A(B0p0p0)

A2

A(B-p-p0)

A(B+p+p0) is pure tree.

  Gronau and London (1990)

(slide from David Kirkby)

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Expectations/Prejudices…

  • Measure coefficients for both sinDmDt and cosDmDt terms (Spp and Cpp ).

  • Spp and Cpp are determined by a, b, |P/T|, and d. Assume

  Gronau and Rosner, PRD65, 093012 (2002)

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

mes and DE for B0 p + p -

Kp

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

~44M BB pairs

~88M BB pairs

BABAR

B0 tags

qq and Kp background

B0 tags

B0 tags

hep-ex/0207055 (ICHEP/PRL)

Sππ= 0.02 ± 0.34 ± 0.05Cππ= -0.30 ± 0.25 ± 0.04

Belle

B0 tags

bkgdsubtracted

hep-ex/0204002, PRL

+0.38 +0.16 -0.27 -0.13

Sππ= -1.21Cππ= -Aππ=-0.94 ± 0.09

+0.25 -0.31

Brian Meadows, U. Cincinnati


Interpretation

Belle

Interpretation

BABAR

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

B0 p  p 

88M B pairs

+10 -9

N( p  p ) =23 events

2.5 s significance

hep-ex/ 0207063 (ICHEP2002)

B(p  p ) = < 3.6 x 10-6

B(p  p )

< 0.61 

B(p  p )

|aeff - a|< 51° @ 90% CL

rp

  Grossman, Quinn

hep-ex/ 0207090 (sub to PRD)

cut on likelihood ratio with 20% signal efficiency

B(p  p ) = < 6.4 x 10-6

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

hep-ex/0207068 (ICHEP2002)

Arπ= -0.22 ± 0.08 ± 0.07AKπ= +0.19 ± 0.14 ± 0.11

B0 “rp ”

Clear B0signal observed in rp region of p+p-p0 Dalitz plot.

From counting # of “rh+” and “rh-” events…

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

hep-ex/0207068 (ICHEP2002)

Srπ= +0.16 ± 0.25 ± 0.07Crπ= +0.45 ± 0.19 ± 0.09

From time-dependence of “rp” events…

continuum background

B background

Interpretation in terms of angles of unitarity triangle difficult!

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

sin2

Vub*Vud

g

Vcb*Vcd

Brian Meadows, U. Cincinnati


Charmless two body decays

Charmless Two-Body Decays

In decays such as B  K p, interference between the Tree and Penguin amplitudes can lead to CP asymmetries that depend on g AND the strong phase difference. Also, ratios of BF for various p p and K p decay modes are sensitive to the angle g.

Goal: Measure CP asymmetries AND branching fractions for all charmless two-body final states.

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Charmless 2-Body B Decays

Preliminary

~88MB pairs

~60MB pairs

Brian Meadows, U. Cincinnati


Cp asymmetries in charmless modes

CP asymmetries in charmless modes

New

ACP sensitivity for BK+p- = ± 0.05

red  dominant penguin

blue  dominant tree

  • Details in hep-ex/0207065, 0206053, 0207055,

  • 0207087, PRL88 101805, PRD65 091101, PRD65 051101

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Charmless Three-Body B Decays: why are they interesting?

Sensitive to same weak phases as charmless 2-body decays.

Dalitz plot analyses of 3-body decays can (eventually) be used to help disentangle relative strong phases.

Already being done in charm decays.

A long way to go in B physics, but we’re starting…

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

All B+K+h+h-, B0Ksh+h- and BKsKsh modes being studied by Belle

>4s signals in six of eleven 3-body modes being studied.

Studying resonance substructure.

Belle B+K+p+p-

237±23 events

K*(892)0p+ and f0(980) K+ observed.

  hep-ex/0201007, PRD

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

Potential for measuring g with B  D(CP=±)K decays

unknown strong phases d1 and d2

u

b

u

D0

K+

c

s

B+

b

c

s

B+

K+

D0

u

u

u

u

color suppressed

= CP eigenstates

Determine g through amplitude relationships (up to discrete ambiguities): Gronau & Wiler; Dunietz (1991).

Brian Meadows, U. Cincinnati


Recent results from the babar experiment

CP charge asymmetries in B  D(CP)K from Belle and BABAR:

B-Dp

B-DK

  •  BABAR: hep-ex/0207087 (ICHEP2002)

  • Belle: hep-ex/0207012 (sub to PRL)

Dfl

ACP+ = + 0.29 ± 0.26 ± 0.05

DCP+

ACP+ = + 0.17 ± 0.23

+0.09 -0.07

ACP- = - 0.22 ± 0.24 ± 0.04

DCP-

See hep-ph/0209194 for ideas on using 3-body modes such as DKp to avoid color suppression and resolve ambiguities through Dalitz plot.

DE (GeV)

Brian Meadows, U. Cincinnati


Summary on cp measurements

Summary on CP Measurements

With the rapidly increasing data samples from the B Factories, many new decay modes are becoming available for

time-dependent CP asymmetry measurements (sensitive to band a);

direct CP asymmetry measurements (mostly sensitive to a and g);

branching fraction and resonant substructure measurements that are crucial for the interpretation of many of the CP asymmetries.

b is in agreement with SM predictions and indirect measurements.

Too early to interpret results on a.

Some slightly statistically significant discrepancies are appearing:

e.g., time-dependent asymmetries in fKs and D+*D-*.

More data is on its way…

Brian Meadows, U. Cincinnati


Charm physics at babar

Charm Physics at BaBar

  • D0 mixing results:

    • Wrong sign hadronic decays

    • Measurements of lifetime ratios

    • Semi-leptonic decays in progress

    • Other hadronic modes

  • Many 3 body decays of D and Ds mesons under study:

    • Preliminary D0!K0sh+h- results

    • Light quark studies

  • Other Meson studies:

    • Spectroscopy of D and Ds meson sector.

    • Direct CP violation

    • Rare decay searches planned

  • Baryon studies underway

    • Cabbibo suppressed and semi-leptonic modes

    • Spectroscopy

  • ISR measurements:

    • Absolute branching fractions, leptonic decays

New - Moriond QCD

Brian Meadows, U. Cincinnati


D 0 lifetime samples

D0 Lifetime Samples

  • All BaBar data from 2000-2002 runs - 91 fb-1 were used.

  • Four independent samples were isolated, three of which were tagged as D0 or

  • A is Cabbibo Favoured (CF) and B-D are Singly Cabbibo Suppressed (SCS).

Brian Meadows, U. Cincinnati


D 0 lifetime samples1

A

B

A

B

C

D

C

MeV/c2

GeV/c2

D0 Lifetime Samples

Unbinned likelihood fit to (m, t, t) ! (<> , 0, A)

m(D0) Fits

m = mD+- mD

Brian Meadows, U. Cincinnati


Summary of lifetime ratio results

Summary of Lifetime Ratio Results

Systematic uncertainties summarized:

Y and Y:

Brian Meadows, U. Cincinnati


D 0 mixing from wrong sign decays1

D0 Mixing from Wrong Sign Decays

  • Time integrated rate for WS decay is

  • CP violation makes the terms for D0 (+) differ from those for D0 (-):

    x’§ = rm§ 1 [xcos( § ) + ysin( § )]

    y’§ = rm§ 1 [-xsin( § ) + ycos( § )]

  • Measurable CP violation parameters are:

= RM

Strong phase between

CF and DCS decays.

Mixing phase

Brian Meadows, U. Cincinnati


D 0 mixing from wrong sign decays2

D0 Mixing from Wrong Sign Decays

  • D0’s (D0’s) are tagged at production by charge of the slow pion (§s) from D*‘s recognized by peak in m = mD - mD distribution.

  • At decay they are labeled as WS if the K has the same charge as s and RS if opposite.

  • Four samples distinguished in likelihood fit:

  • WS and RS samples fit simultaneously to {m, m, t, t}. Physics parameters {RWS, x’2, y’} from WS. Resolutions, etc. from RS. (Backgrounds from both RS and WS).

Brian Meadows, U. Cincinnati


Mass projections with fit for ws sample

Mass Projections with Fit for WS Sample

Signal Region

Sideband

Data:Dots

Fit:

signal

wrong s

double mis-ID

combinatorial

Wrong Sign

Sample

BaBar - 57.1 fb-1 sample.

Brian Meadows, U. Cincinnati


Fit results1

Fit results

WStimefit.

Signalregion

Sideband

region

Fits with and without CP violation or mixing were made with x’2<0 allowed.

Central fit values have x’2<0

Brian Meadows, U. Cincinnati


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