Charm results overview 1 Charm ...the issues • Lifetime • Rare decays • Mixing • Semileptonic sector • Hadronic decays (Dalitz plot) • Leptonic decays • Multi-body channels (4,5,6 bodies!) • Charm Baryons • D* spectroscopy
Dec 19, 2015
Charm results overview 1
Charm ...the issues
• Lifetime • Rare decays• Mixing• Semileptonic sector• Hadronic decays (Dalitz plot)• Leptonic decays• Multi-body channels (4,5,6 bodies!) • Charm Baryons• D* spectroscopy
Charm results overview 2
A brief review of the measurements
for each topic:
• summary of the present experimental situation
• a comment about the next future reach
to be done
• a more precise picture of the experimental status within 5 and 10 years
– BaBar, Belle, Cleo-c, CDF, BEPC, LHC-b, BTeV
Charm results overview 3
Charm lifetimes
0
( )2.538 0.023
( )
D
D
Motivation: investigation of non-spectator processes
• FOCUS (*) produced new lifetimes results with precision better than the previous world average (○), PDG 2002.•Already at the level of comparison with theory.•Systematics will dominate
Charm results overview 4
Rare decays
( ,
,
)sD D h
h K
FOCUS improved results by a factor of 1.7 –14: approaching theoretical predictions for some of the modes but still far for the majority
CDF and D0 can trigger on dimuons promising
Motivation: lepton number violation studyinvestigation of long range effects and SM extention
CDF Br(D0+-)<2.4 x10-6 @ 90% C.L.is the best limit for this mode (65 pb-1 data)
Charm results overview 5
MixingMotivation: suppressed in the charm sector in the SM. If “measured”, would suggest SM extention
Future is @ Babar & Belle
;2
Mx y
Charm results overview 7
The semileptonic sector
FOCUS number is 1.59standard deviation below CLEO and 2.1 standard deviation above E691
All values consistent with their average value with a CL of 19%
Motivation: semileptonic decays are the easiest way to determine CKM elements
0*D K Branching ratio
Charm results overview 8
...and form factors
The vector and axial form factors are generally parametrized by a pole dominance form
22 2
(0)( )
1i
iA
AA q
q M
2
2 2
(0)( )
1 V
VV q
q M
2.5
2.1A
V
M
M
2/GeV c2/GeV c
Nominal spectroscopicpole masses
v 1(0) (0)r V A 2 2 1(0) (0)r A A
3 3 1(0) (0)r A A
D+
d
d
uu
s
Charm results overview 9
form factors
v 2
1.45 0.23 0.07 1.00 0.15 0.03
791( ) 1.90 0.11 0.09 0.71 0.08 0.09
791( ) 1.84 0.11 0.09 0.75 0.08 0.09
687 1.74 0.27 0.28 0.78 0.18 0.11
653 2.0
1.504 0.057 0.039 0.875 0.049 0.06
0 0 3
4
. 3
Group r rFOCUS
BEATRICE
E e
E
E
E
0.16 0.82 0.22 0.11
691 2.0 0.6 0.3 0.0 0.5 0.2E
FOCUS analysis is the first to include the effects on the acceptance due to changes in the angular distribution brought about the s-wave interference
Form Factor lattice calculations available!
0*D K
Charm results overview 10
Group electron muon
FOCUS 0.540.0330.048
CLEO2 0.540.050.04
E687 0.580.170.07
ARGUS 0.570.150.15
CLEO 0.490.100.12
Br(Ds / Ds
sD
Charm results overview 11
v 2
791 2.27 0.35 0.22 1.570 0.250 0.190
0.9 0.6 0.3 1.400 0.500 0.300
653 2.3 1.0 0.4 2.
1.549 0.250 0.145 0.713 0.202 0
100 0.550 0.
.26
0
6
2 0
Group r r
E
CLE
FOC
O
US
E
form factors
1. Most precise measurement to date2. very consistent with D+K03. very consistent with th. expectation
Cleo-c expects experimental error in most of the measurements in the sl sector in the range
1 to a few %
sD
Charm results overview 12
Hadronic decay investigation
A few slides follow about Dalitz plot analysis
Charm results overview 13
“Future” of hadronic decays
•Full observation of the decay (for three-body channels)•Learn about strong effects (but also a complicationfor the analysis!)•CP investigation (see example of D±K K±±)•Interplay between charm (and beauty) decays and light meson spectroscopy (very clean samples!)
Motivation: Investigation of decay dynamics via Dalitz plot analysis
The analysis is difficult, need an analysis strategy to keep under control the strong effects accompanying the weak decays of Heavy Flavours!
Charm results overview 14
An instructive example from FOCUS
Milano group
D
analogy with operatively:
complete Dalitz plot analysis (time-dependent) to deal withall interference with other () intermediate channels
B
crucial for determination of the angle of the SM unitarity triangle
Charm results overview 15
FOCUS D s +
++- analysis
Observe:
•f0(980)
•f2(1270)
•f0(1500) Sideband
Signal
Yield Ds+ = 1475 50
S/N Ds+ = 3.41
f0(980) signal is clean!
Charm results overview 16
First fits to charm Dalitz plots in the K-matrix approach!
C.L fit 3 %
sD
Low mass projection High mass projection
+
+20 +
(S - wave)π 87.04 ± 5.60 ± 4.17 0(fixed)
f (1275)π 9.74 4.49 2.63 168.0 18.7 2.5
ρ (1450)π 6.56 ± 3.43 ± 3.31 234.9 ±19.5 ±13.3
decay channel phase (deg)fit fractions (%)
r
j
2iδ 2 2r r 12 13
r 2iδ 2 2j j 12 13j
a e A dm dmf =
a e A dm dm
Projections of the f0(980) signal
Charm results overview 17
sD
•No significant direct three-body-decay component
•No significant (770) contribution
sD
Marginal role of annihilation in charm hadronic decays A reliable measurements of the annihilation processes in the hadronic sector is still missing.... need more data!
Charm results overview 18
Yield DYield D++ = 1527 = 1527 5151
S/N DS/N D++ = 3.64 = 3.64
FOCUS D+ ++- analysis
Sideband Signal
Charm results overview 19
2lowm
2highm
D
C.L fit 7.7 %
K-matrix fit results
Low mass projection High mass projection
18 11.7
+
+2
0 +
(S - wave)π 56.00 ± 3.24 ± 2.08 0(fixed)
f (1275)π 11.74 1.90 0.23 -47.5 .7
ρ (770)π 30.82 ± 3.14 ± 2.29 -139.4 ±16.5 ± 9.9
decay channel phase (deg)fit fractions (%)
Good channel to investigatethe nature of the meson(aka the puzzle).No new ingredient (resonance)
required not present in the scattering!
Charm results overview 20
With
Without
C.L. ~ 7.5%
Isobar analysis of D+ ++would instead require a new scalar meson:
C.L. ~ 10-6
m = 442.6± 27.0 MeV/c = 340.4 ± 65.5 MeV/c preliminary
Charm results overview 21
Another interesting example from FOCUS D+, Ds KK
Ds+ K+ K+ D+ K+ K+
D sD
2Km
2KKm 2
KKm
2Km
KKm
Charm results overview 22
+ -2
K Km
- +2
K πm
K+ Kprojection K projection
Yield D+ = 7106 92
S/N D+ = 8.62
Decay Fraction and phases
K*(892) = 20.7 1.0 % (0 fixed)
(1020) = 27.8 0.7 % (243.1 5.2)°
K*(1410) = 10.7 1.9 % (-47.4 4.9)°
K* (1430) = 66.5 6.0 % (61.8 3.8)°
f0(1370) = 7.0 1.1 % (60.0 5.3) °
a0(980) = 27.0 4.8 % (145.6 4.3)°
f2(1270) = 0.8 0.2 % (11.6 7.0) °
(1680) = 1.6 0.4 % (-74.3 7.5) °
Preliminary
Possible investigation of a0(980) & the f0 series
Charm results overview 23
CP violationFor a two amplitude decay
ii = strong phase
CP asymmetry:
2 different amplitudes strong phase-shift
AAtottot = g1M1ei1 + g2M2ei2
CP conjugate
AAtottot = g1M1ei1 + g2M2ei2** **
aaCPCP==2Im(2Im(gg2 2 gg11**) sin() sin(11--22)M)M11MM22
|g|g11||22MM1122+|g+|g22||22MM22
22+2Re(+2Re(gg2 2 gg11**)cos()cos(11--22)M)M11MM22
|Atot|2- |Atot|2
|Atot|2+ |Atot|2==
Charm results overview 24
Dalitz plot = FULL OBSERVATION FULL OBSERVATION of the decay
COEFFICIENTS and PHASES for each amplitude
Measured phase: =+CP conserving CP violating
CP conjugate =
=-=-
E831
aCP=0.006±0.011±0.005Measure of direct CP violation:asymmetrys in decay rates of DDKKK K
CP violation via D+ K-K++ Dalitz analysis
Charm results overview 25
phi(1020) K*(1430) a0(980) K1(1410) f2(1270) f0(1370) phi(1680)
K*(1430)phi(1020) a0(980) K1(1410) f2(1270) f0(1370) phi(1680)
Coefficients: D±,, DD++,, DD--
Phases: DD±±,, DD++,, DD--
Preliminary!
No evidence of CPV
Charm results overview 26
Other Dalitz plot analyses
• 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.
15,753 events 23 fb-1
Scale to the full sample!
BaBar & Belle have the statistics to make it! The problem is the formalism!
In Cleo-c there is a dedicated working group consisting of experimentalists and theoreticians
BaBar
Charm results overview 28
for the future...
• Multi-body charm decays• Charmed baryon spectroscopy• D* spectroscopy
– Statistics is still limited: some results from BaBar, Belle, FOCUS
– More data necessary: CDF, Cleo-c, B-factory, LHC-B, BTeV
Charm results overview 29
Some slides of general interest
• Why charm at a B factory
• How is Tevatron working
• Cleo-c run plan
• Comparison among experiments
• BEPC future
Charm results overview 30
Charm at B Factory?
• Cross section is large
Present BaBar sample of 91 fb-1 contains
• Compare with earlier charm experiments:– E791 - 35,400 1
– FOCUS - 120,000 2
– CDF - 56,320 (new number available soon)