(from focus and babar) · 2003. 4. 24. · d0→k-π+ events brian meadows: moriond 2003 1. e791...
TRANSCRIPT
Sandra Malvezzi - Charm Results from Focus and BaBar
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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.
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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
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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+ + + + −→
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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
* Crystal BarrelCrystal Barrel
* Crystal BarrelCrystal Barrel
* 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
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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→
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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