(from FOCUS and BaBar) · 2003. 4. 24. · D0→K-π+ events Brian Meadows: Moriond 2003 1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) ... by fitting the angular distributions

Sandra Malvezzi - Charm Results from Focus and BaBar

1

Sandra MalvezziI.N.F.N. Milano

Charm Review(from FOCUS and BaBar)

IFAE 2003 Lecce


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A new charm-physics eraThe high statistics and excellent quality of data allow for unprecedented sensitivity & sophisticated studies

Lifetime measurements @ better than 1%non-spectator processes

Mixingpossible window on physics beyond SM

Investigation of decay dynamics both in the hadronic and semileptonic sector

Phases and Quantum Mechanics interferenceFSI role & CP studies

a lesson for the b physics!!!


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PWC

Over 1 million reconstructed!

Vertexing

Cerenkov

spectrometer

Muon id

Successor to E687. Designed to study charm particles produced by ~200 GeV photons using a fixed target spectrometer with updated Vertexing, Cerenkov, EM Calorimeters, and Muon id capabilities. Member groups from USA, Italy, Brazil, Mexico, Korea.


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Charm at BaBar B 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 x 106 untaggedD0→K-π+ events

Brian Meadows: Moriond 2003

1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) 32.2. Focus Collaboration, Phys.Lett. B485 (2000) 62.


5

Observation of a Narrow Meson decaying to at a Mass of 2.32 GeV/c in BaBar

hep-ex/0304021

0sD π

2

Isospin-Violating Decay

2

mass=2316.8 ± 0.4 MeV/cyield=1267 ± 53 evts


6

Meson lifetime

(Bigi Uraltsev):1.00-1.07 (no WA/WX) ;0.8-1.27(different process

interference)


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Baryon lifetime

01 1 ;15 3c cD

τ τ τ+ +Ω Λ≈ ≈ need boost and precise vertexing

In the baryon sector the expected hierarchy: 0 0( ) ( ) ( ) ( )c c c c+ +Γ Ξ < Γ Λ < Γ Ξ Γ Ω∼


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Charm Mixing;

2Mx y∆ ∆Γ

= =Γ Γ

Mixing parameters:

Direct comparison of CP final state lifetime finds CPy

02( )D K K CP+ −→ + → Γ

0

1 2

1 1( & )2 2

1( ) ( )2

D K CP CP

K

π

π

− +

− +

→ + −

→ Γ ≈ Γ + Γ

0

0

( ) 1( )CPD KyD KK

τ πτ

→= −

→


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2 22 2' '( )

2'( )t

WS DCS DCSxR t e R R t tyy−Γ +

Γ= + +Γ

' cos sin' cos sin

x x yy y x

δ δδ δ

≡ +≡ −

δ is the relative strong phase

Alsolook for mixing in wrong sign semileptonic or hadronic decays

•Doubly Cabibbo Suppressed decays complicate hadronic decays

•With CP conservation, the wrong-sign to right-sign decay rate is

The three terms come from DCS decays, interference and mixing.In semileptonic decays only the mixing term appears


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FOCUS

CLEOII.V

E791

95% CL

BELLE

+−+−→ ππ/0 KKD

−+→ πKD0

+−+−→ ππ/0 KKD

+−+−→ ππ/0 KKD

E791 ν−+→ KD0

FOCUS

FOCUS K+ µ-ν

FOCUS K+ π−

D0 -D0 MIXING STATUS 2002

%

%

BaBar 0 /D K K π π+ − + −→

FOCUS (2000) PLB485:62-70,2000

yCP = 3.42 ± 1.39 ± 0.74%

BELLE (2002)

yCP = -0.5 ± 1.0+0.7-0.8%

BABAR (2002)

yCP = 1.4 ± 1.0± +0.6-0.7 %


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Published (23.4 fb-1)

Moriond 2002

Moriond 2003

FOCUS, CLEO, BaBar, and Belle are all investigating mixing using semileptonics and various hadronic modes

BaBar: 0D K π+ −→ “No mixing No CP violation”hep-ex 0304007


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New results on D Kπµν+ →

Our Kπ spectrum lookslike 100% K*(892)

This has been known for about20 years

...but a funny thing happened when we tried to measure the form factor ratios by fitting the angular distributions


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An unexpected asymmetry in the K* decay

forward-backwardasymmetry incos below the K*pole but almost noneabove the pole

Vθ

Vdd θα 2cos1+∝ΩΓ

Sounds like QM interference


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Simplest approach — Try an interfering spin-0 amplitude

B

B

B

M

2

2 2

0

(1 cos ) sin2 2(1 cos ) sin

( )2 2

sin(cos )

2

il V

l iV

lV

i

e

Ae

H

t m e H

Hδ

χ

χµ

θ θ

θ θ

θθ

+

−−

+

− −∝ − +

−+ +

We simply add a new constant amplitude : A exp(iδ) in the place where the K* couples to an m=0 W+ with amplitude H0. This assumes the q2 dependence of the anomaly s-wave coupling is the same as the K* (could be challenged)

2 20 0

B where omm m im

Γ≡

− + Γ

+ muonmass terms

A exp(iδ) will produce3 interference terms

A 4-body decay requires 5 kinematic variables:

• MKπ• MW

2 ≡ q2 ≡ t

Focus Semileptonic 15

Studies of the acoplanarity-averaged interference

( )*2 208 cos sin Re i

V l KA e B Hδθ θ −+

Efficiency correction is small

Extract this interference term by weighting data by cosθV,

Since all other χ-averaged terms in the decay intensity are constant or cos2θv.

We begin with the mass dependence: ( )*Re i

Ke Bδ−

090δ =

00δ =

045δ =

..looks just like the calculation..

0m −Γ 0m + Γ0m

Our weighted mass distribution..

A=0

0.36 exp(iπ/4)

A constant 450

phase works great...

…other options also possible (next slide).


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-6000

-4000

-2000

0

2000

4000

0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96 0.98 1

FOCUS fitLASS Scaled fitKappaKappa

..but other options would work as well.Asymmetry expected directly from LASS s-wave K π phase shift analysis.

And Kappa with no fsi phaseshift and with a 100 degree phase shift.

cos

θ Vte

rm

Km π

cos θv weighted M(Kπ), GeV/c2


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Will there be similar effects (interference) in other charm semileptonic or beauty semileptonic channels?Good question.


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E691

E653

E791

FOC

US

BE

AT

E687

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

E687E7

91

FOC

US

BEA

T

E691

E653

0.0

0.5

1.0

1.5

2.0

2.5

3.0Form Factor Measurements

1.66 0.060±

0.827 0.055±

The experimental RV value is getting smaller with the passing years. The new Focus value is 2.9 σ below E791. We were consistent before charm background correction.

Apart from E691 the R2 values have been pretty consistent.

Latest form factor calculation Damir Becirevic (ICHEP02)RV = 1.55 ± 0.11which is remarkably close toRV = 1.504 ± 0.087(FOCUS)

time

RV

R2

New WA

New WA

New FOCUS Results:

RV = 1.504 ± 0.057 ± 0.039 R2 = 0.875 ± 0.049 ± 0.064 FOCUS, PLB 544 (2002) 89


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• Dynamics of hadronic decays• substructures in the Dalitz plots• interference & branching ratios

Over the last decade charm Dalitz-plot analysishas emerged as an excellent tool to study

• Role of non-spectator diagrams in charm decayse.g.

sD π π π± ± ±→ ∓

• FSI effects in three-body decays• phase shifts between different resonant amplitudes• extension of the isospin analysis from the two-body system

The high statistics now available demands proper parametrization

Three -body hadronic decay dynamics


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to face the problem of the light mesons • certainly a complication for the interpretation of charm decay dynamics

• more difficult Dalitz plot analysis

Why the charm community had

to be educated in the general s-wave formalism• two-body unitarity • Breit-Wigner approx. limits, K-matrix approach etc...

and how it started

...a warning for beauty!


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For a well-defined wave with specific isospin and spin (IJ)characterized by narrow and well-isolated resonances, we knowhow.• the propagator is of the simple Breit-Wigner type and the amplitude is

How can we formulate the problem?

rD r→| 1 2

3

The problem is to write the propagator for the resonance r

r3

1

2

1 3 13 2 2

1(cos )J J r

D r Jr r r

A F F p p Pm m im

ϑ= × ×− − Γ


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when the specific IJ–wave is characterized by large and heavily overlapping resonances (just as the scalars!), the problem is not that simple.

1( )I iK ρ −− ⋅

where K is the matrix for the scattering of particles 1 and 2.

In this case, it can be demonstrated on very general grounds that the propagator may be written in the context of the K-matrix approach as

Indeed, it is very easy to realize that the propagation is no longer dominated by a single resonance but is the result of complicatedinterplay among resonances.

i.e., to write down the propagator we need the scattering matrix

In contrast


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21 0

2 20 0 0

1 2( )( )(1 )

jK Ak kj j

A A

g s s s mF I iK fm m s s s s s

αα π

α α

βρ −

− − = − ⋅ + × − − − − ∑

We may summarize by saying that:

The decay amplitude may be written, in general, as a coherent sumof BW terms for waves with well-isolated resonances plus K-matrix terms for waves with overlapping resonances.

00

1 1( ) i i

m ni i iBW K

i i i ii i m

A D a e a e F a e Fδ δ δ

= = +

= + +∑ ∑Where the general form of for scalars is K

iF


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In the light of this

But now the question arises:

Is this a meaningful description of the underlying physics or just a mirage?

if we try to fit a generic Dalitz plot with the simple isobar model, we have to let the masses and widths of overlapping resonances in the same waves float freely, in order to get a decent fit.

We shall see this problem in the FOCUS channels

,sD D π π π+ + + + −→


25

FOCUS D s + → π +π +π - analysis

Sideband

Yield Ds+ = 1475 ±50

S/N Ds+ = 3.41

Observe:

•f0(980)

•f2(1270)

•f0 (1500)

Dominated by weirdresonances with simultaneous

KK and ππ couplingsH

igh

mas

s

low mass


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f2(1270)f0(980)

f0(980)

f2(1270)S0(1475)

r

j

2 2 2r r 1 2 1 3

r 22 2

j j 1 2 1 3j

A d m d mf

A d m d m

i

i

a e

a e

δ

δ= ∫

∑∫ 150%rr

f =∑

Preliminary

m = 1475 ± 10 MeVΓ = 112 ± 24 MeV

m = 975 ± 10 MeV= 90 ± 30 MeV= 36 ± 15 MeV

Isobar approach Coupled-channel BW

ππΓKKΓ


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S0(1475) (Focus)m = 1475 ± 10 MeVΓ = 112 ± 24 MeV

PreliminaryPDG Value for f0(1500)m = 1507 ± 5 MeVΓ = 109 ± 7 MeV


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Yield DYield D++ = 1527 = 1527 ±±5151

S/N DS/N D++ = 3.64= 3.64

FOCUS D+→ π +π +π -

high

mas

slow mass


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Single BW for f0(400)

m = 443 ± 27 MeVΓ = 443 ± 80 MeV

E791 Results :24234240

478 17

324 21

m MeV

MeV

+−

+−

= ±

Γ = ±

f0 (400)ρ0 (770)

f0(980)

ρ0 (770)

f0(980)S0(1475)f2(1275)

Preliminary

Isobar approach


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Without f0(400)

With f0(400)

2lowm

2highm

2highm

C.L. 10-8

C.L. 0.8%

FOCUS D+→ π +π +π -

2lowm


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22 2

( ) ( )( )

( )ai aj

ij ija a

g m g mK c m

m m= +

−∑

Resonances in K-matrix formalism

2 2

( ) ( )( )ai aj

ija a

g m g mK

m m=

−∑where

)()(2 mmmg aiaai Γ=

Unitarity ...

1( )T I iK Kρ −= − ⋅

S.U. Chung et al.Ann.Physik 4(1995) 404


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... from scattering to production:the P-vector approach

2 2

( )( )

ii

g mPm m

α α

α α

β=

−∑β (complex) carries the production information

i i iP P d= +

1( )F I i K Pρ −= − ⋅

I.J.R. AitchisonNucl.Phys. A189 (1972) 514

known from scattering data


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“K-matrix analysis of the 00++-wave in the mass regionbelow 1900 MeV’’

V.V Anisovich and A.V.Sarantsev Eur.Phys.J.A16 (2003) 229

We need a description of the scattering ...

* pp→p0p0n, hhn e hh’n, |t|<0.2 (GeV/c2)GAMSGAMS

* pp→p0p0n, 0.30<|t|<1.0 (GeV/c2)GAMSGAMS

* BNLBNL

*pp- → KKn

CERNCERN--MunichMunich

::

p+p- → p+p-

* Crystal BarrelCrystal Barrel




pp → p0p0p0, p0p0h

pp → p0p0p0, p0p0h , p0hh

pp → p+p-p0, K+K-p0, KsKsp0, K+Ksp-

np → p0p0p-, p-p-p+, KsK-p0, KsKsp-

p-p→p0p0n, 0<|t|<1.5 (GeV/c2)E852E852*


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( ) ( ) 200 0

20 0 0

1 2( )( )(1 )

scatti j scatt A

ij ij scattA A

g g s s s mK s fm s s s s s s

α απ

α α

− −= + − − − −

∑

( )ig α is the coupling constant of the bare state α to the meson channel

scattijf

0s describe a smooth part of the K-matrix elements2

0 0( 2 ) ( )(1 )A A As s m s s sπ− − −suppresses the false kinematical singularity at s = 0 near the ππ threshold

and

is a 5x5 matrix (i,j=1,2,3,4,5)

ηη 'ηη

IJijK

K K1=ππ, 2= 3=4π 4= 5=

A&S


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A&S K-matrix poles, couplings etc.

4 '

0.65100 0.24844 0.52523 0 0.38878 0.363971.20720 0.91779 0.55427 0 0.38705 0.294481.56122 0.37024 0.23591 0.62605 0.18409 0.189231.21257 0.34501 0.39642 0.97644 0.19746 0.003571.81746 0.15770 0.179

KKPoles g g g g gππ π ηη ηη

− − −

−

0 11 12 13 14 15

0

15 0.90100 0.00931 0.20689

3.30564 0.26681 0.16583 0.19840 0.32808 0.31193

1.0 0.2

scatt scatt scatt scatt scatt scatt

A A

s f f f f f

s s

− −

− −

−


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4 '13.1 96.5 80.9 98.6 102.1

116.8 100.2 61.9 140

( , /2)(1.019, 0.038) 0.415 0.580 0.1482 0.484 0.401(1.306, 0.167) 0.406 0.105 0.8912 0.142

KKi i i i i

i i i i

m g g g g ge e e e ee e e e

ππ π ηη ηη

−

Γ .0 133.0

97.8 97.4 91.1 115.5 152.4

151.5 149.6 123.3 170.6

0.225(1.470, 0.960) 0.758 0.844 1.681 0.431 0.175(1.489, 0.058) 0.246 0.134 0.4867 0.100 0

i

i i i i i

i i i i

ee e e e ee e e e

− −

133.9

.6 126.7 101.1

.115(1.749, 0.165) 0.536 0.072 0.160 0.313

i

i i i i i

ee e e e e

−

101.6 134.2 − 123

0.7334

A&S T-matrix poles and couplings

A&S fit does not need the σ


37

First fits to charm Dalitz plots in the K-matrix approach!preliminary

sD πππ→

fit fractions phases

105%rr

f∑ ∼


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low proj high proj

2lowm

2highm

fit fractions phases

preliminaryD πππ+ →

99%rr

f∑ ∼

...parametrization of two-body resonances coming from light-quark experiments works for charm decays too. Not obvious!


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BaBar Three Body Decays of D Mesons

• Three body modes are also studied.• The Ks

0π+π- 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 φ+δ from Dalitz plot.

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

15,753 events23 fb-1

B.M Moriond 2003

ππ & Kπ interactions!

0sD K ππ→

0sD K KK→


40

Can we get a pure Κs φ CP odd from D0→ Ks K+K- ?Κs φ is a CP odd state: Ks and φ are CP even

Κs φ is in a relative p-wave with parity -1

Κs f0(980) is a CP even state: Ks and f0 are CP even

Κs f0(980) is relative s-wave with parity +1

Two states interfere in same region in Dalitz plot:

Is there a pure CP odd eigenstate near the φ ?

No. A CP even eigenstate will be present with a non-negligible fraction.

Tagged sample

K+K-

Ks K

asymmetry in φ lobesindicates interference

Fraction of events in the φ region due to φKs is: *

62 3%tota

region

regiol to al

nt

A A

A Aφ

φ

φ φ

= ±∫

∫0 62% CP odd and 3" " 8% CP even is sD Kφ→


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• At 30 years from the discovery of the c quark the physics of the first heavy quark has reached a complete maturity • With the high statistics now available in the charm sector,we start seeing strange effects which make the interpretationof the decay processes more complicate• Interplay between light hadrons and charm requires a more proper formalism for Dalitz plot analysis (σ and κ puzzle)

• Lessons for the b sector?•Many b particles decay to charm so branching ratios, lifetimes etc needed for accurate b results

•Experimental techniques, such as Dalitz plot, can be performed and tested in charm.

Conclusions

Documents

(from FOCUS and BaBar) · 2003. 4. 24. · D0→K-π+ events Brian Meadows: Moriond 2003 1. E791 Collaboration, Phys.Rev.Lett. 83 (1999) ... by fitting the angular distributions