Trend in Charm Spectroscopy

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Trend in Charm Spectroscopy
byUsha Mallik (The University of Iowa)

• A Recap of particles
• An Intro
• DsJ Spectroscopy
• X,Y,Z states
• Charmed baryons
• Measurement of Spins
• D0-D0 Mixing
• Summary and Conclusion

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3 generations of quarks, leptons
Quarks, leptons ? spin 1/2
ee- qq , ll-
These quarks immediately Dress-up as Hadrons by
strong interactions (QCD)
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Continuum and Resonance Production

• ? cc
• Hidden charm

R
? ? bb
4
What happens at BABAR
e- beam energy 9.1 GeV, e beam energy 3 GeV,
E(cm) 10.58 GeV
(5279MeV)
time
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OZI Suppression in Decays
b
q
X
q
?(1S) (9460) MeV
q
X
q
b
time
Since ?(1S) is below B meson pair production
threshold, the original b quarks can not be
present in the final state causing the decay
rate slower, ie, the lifetime of ?(1S) longer,
and the resonance narrow.
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The Periodic Table of Hadrons
Gell-Manns Eight-fold Way
Originally in the 1960s with only u, d, s
quarks meson ? qq q ? u, d, s q ? u, d, s
3 ? 3 1 ? 8
J ½ ½ 0
J ½ ½ 1
JP 0- , Pseudoscalar nonet with ?'
JP 1- , Vector nonet
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With u, d, s, c quarks, the picture gets richer
JP 0- , Pseudoscalar nonet and ?c
JP 1- , Vector nonet and J/?
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The BABAR Detector at PEP-II and the Dataset
Ecm 10.58 GeV
And Much More
Peak luminosity gt 1.2 x 1034 cm-2 s-1 Delivered
luminosity gt 425 fb-1
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Charm-strange mesons (cs) Ds, DsJ
With 400 fb-1 data, over 1 billion charmed
hadrons produced
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Expected spectroscopy
3P0
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Observed States
DSJ(2317) and DSJ(2460) observed in
Spin-Parity Established
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(fits better with a Gaussian, rather than BW)
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Yield 182 ? 30 Mass ( MeV/c2) 2715
11-14 Width (MeV/c2) 115?2036-32
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Preliminary (New)
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NEXT The New Charmonia ! The Alphabet Soup !
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The Charmonium(-like) States
Below DD threshold states well understood. The
X,Y,Z states are all above the threshold
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Confirmed by BABAR, CDF, D0
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Properties of X(3872)
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Preliminary (New)
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While searching for
BABAR finds new state Y(4260)
Not seen in DD
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NEXT The Status of Charmed Baryons
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Baryons
3?3?3 1?8?8?10
baryon ? qqq, anti-baryon ? qqq
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Baryons with 4 flavors (u,d,s,c)
4?4?4 4 ?20?20?20
1/2
3/2
Ground states

u,d,s, octet
Anti-symmetric
Ground state
1/2-
u,d,s, decuplet
All 9 ground states with JP ½ observed
5 ground states with JP 3/2 observed only ?c
was missing
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About charmed baryons
Anti-symm under the interchange of the two light
quarks (u,d,s)
symm. under the interchange of the two light
quarks (u,d,s)
Example Decays
? ?
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Charm Baryon production
Charm baryon or anti charm baryon X
Charm baryon lifetimes are small, even though
weak decays
b ? c, and c ? s are weak decays, 10-13 s
lifetime
Weak Decays of ?-, ?- and ?0 take 1,000 times
longer
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Observation of ?c(2880) and ?c(2940) decaying
to D0p
BaBar PRL 98012001(2007)
?c(2940)
New Decay mode ?c(2880) ? D0p First observation
of charm baryon ? charm meson
?c(2880)
Nsig2280?310
Belle confirms in ?c ? (?c??)
Belle Hep-ex/0608043
?c(2765)
Wrong sign D0P
?c(2880)
?c(2940)
D0p invariant mass GeV/c2
D0 mass sidebands
M(?C ? ?-) GeV/c2
Excellent agreement in mass and width
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?c0 Production and Decay
?c0 Decay
PDG values
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?c0 Production in B decays
hep-ex/0703030, submitted to PRL
From B decays
Continnum production
p distribution, momentum in the ee- rest frame
Off-peak data Below B-pair thres-hold, no peak
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BaBar PRL 231 fb-1 97232001(2006)
Discovery of the ?C

Data from all four ?c0 decay modes are combined
and fit yields 105 ? 21 ? 6 5.2?
signal significance
No signal found in the ?c0 mass Sidebands
(hatched area)
?m ( m?c - m?c0) (70.8 ? 1.0 ? 1.1) MeV/c2
Theory range ?m 50 94 MeV/c2
1.01? 0.23? 0.11
Combined
For XP gt 0.5, most/all the ?c0 may results from
?c production, but uncertainty is large.
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Also observed the charged partner ?c
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Study of b ? ccs decay
BABAR, PRL. 95 142003, 2005
Inconsistency in the MC and data p distribution
MC only has b ? cud
Search B decays into charm-baryon-anti-charm-baryo
n pair
B ? ?c?c and B ? ?c ?c K
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B decays to ?c?c and ?c ?cK
An example
?E energy difference between reconstructed B
and Ecm mES beam momentum substituted
reconstructed B mass ee- BB
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B decays to ?c?c
PRD 74 (2006) 111105
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B decays to ?c ?cK
PRL 97 (2006) 202003
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NEXT Spin Measurements
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• Examine implications of W- spin hypotheses
• for angular distribution of L from W- decay

?(L) 1/2
q
quantization axis
?(K) 0
J 1/2 m 1/2 m - 1/2
?(K) 0
?
l(W) 1/2 l(W) - 1/2
W- inherits the spin projections of the Xc0
since, no orbital angular momentum projection
w.r.t. quantization axis in ?c0 decay
? diagonal density matrix element for W- spin
projection li l(W) is rl
i

• Initial helicity, ?i ? (W) 1/2
• Final state helicity, ?f ? (L) -
  ?(pseudoscalar) 1/2
• Decay amplitude for O- ? ? K-

Transition matrix element does not depend on
li Wigner-Eckart theorem
?Total Intensity
density matrix element for W- spin projection
li density matrix element for charm
baryon parent
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Spin measurement of W- from Xc0 ? W- K, W- ?
L K- decays
Data 116 fb-1
Background-Subtracted Efficiency-Corrected
PRL 97 (2006) 112001
Similar conclusion from Wc0 ? W-p, W- ? LK-
decays
ConclusionJ(W-) 3/2 assumingJ(Xc0) 1/2
JW 1/2
? Fit Prob 10 -17
JW 3/2
? Fit Prob 0.64
? Fit Prob 10 -7
JW 5/2
JW 7/2 also excluded angular distribution
increases more steeply near cosq 1
and has (2 JW
-2) turning points.
8
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NEXT D0 D0 Mixing
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Example Mixing
One of the main HEP discoveries in 2006 Bs
Oscillations
x24.8 y0.1?
Bs0 oscillate very rapidly
Rate first measured in 2006 by CDF and D0
Toy MC
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Time-Evolution of D0 ? K p-
D0 can reach the K ?- final state in two
ways 1) Doubly-Cabibbo-Suppressed decay 2)
Mixing to D0bar, followed by Cabibbo-Favoured
decay ... and interference between them.
Q How can we distinguish these? A By the time
evolution.
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Fit Results
Evidence for D0-D0 mixing!
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Many validation tests done
Most powerful is performing a time-independent
fit of the Wrong-Sign and Right-Sign yields in
slices of proper lifetime
Consistent with prediction from full likelihood
fit ?21.5
(stat. only)
Inconsistent with no-mixing hypothesis ?224
Ratio of WS/RS events clearly increase with time.
Mixing signal!
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Summary

• A new landscape in many areas including
  spectroscopy has opened up with high luminosity
  and precision
• New DsJ Spectroscopy
• X, Y, Z States
• Charmed Baryon Spectroscopy
• Spin Measurements (necessary to identify levels,
  complex analysis for multi-body states ?c
  (1530), ?c (1690), in Charmed Baryon decays )
• D0-D0 Mixing Observed

Expecting three/four times more data than shown
in analyses A race to find Beyond Standard Model
Physics
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Legendre Polynomial Moments in Spin Determination

For W- spin J, the previous angular distributions
can be written
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Illustration of the Use of Legendre Polynomial
Moments in Spin Determination

(will prove
useful later)
wj v10 P2(cosq) from Xc0 signal region

• - ?
• signal

W- ? signal
? efficiency-corrected , mass-sideband-subtract
ed unweighted m(L K-) distribution in data
efficiency-corrected v10 P2 (cosq) weighted
efficiency-corrected (7/ v2) P4 (cosq) weighted
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Observation of b ? ccs
? cw- (W- ? cs)
Charm baryon pair production in B Decays
W-
W-
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List of Decay Modes (pair production)
Reconstruct the B meson Use energy momentum
conservation between ee- cm and BB in cm
Look for signal events in the mes, ?E 2D
distribution
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Fit to Signal
B- ? ?c ?c K-
Analysis ongoing
pK-?
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Study of ?c0 (css)

• Production Process and Ratio of Branching
  Fractions of ?C0 (css)
• cc or B ? ?C0 X
  ?C0 ? ?- ?
• 
  ? ?- ? ?- ?
• 
  
  ??-K- ? ?

Preliminary results shown at 2005 summer
conferences Improved analysis using likelihood
selection in progress
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Inclusive ?c0 Studies
BABAR
Branching Fractions and Production Mechanism from
p Spectrum
Decay Modes of ?C0 Studied ? ?-?, ?-??-
?, and ?-K- ? ?
Results
225 fb -1
?C0??-? P gt 2.8 GeV/c
SLAC-PUB-11323, hep-ex/0507011
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Helicity Formalism, Spin Determination

• Suited to two-body (successive) decays
• Can be extended to intermediate resonances
• (ie, quasi-twobody decays using Dalitz plots)

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Helicity angle of ? Angle made by p(?) in ?-
rest frame with p(?-) in ?c0 rest frame
?
?c0
?-
K
K-
Xc0 ? K W- ? L0 K-
?K 0
J 1/2 m 1/2 m - 1/2
?f 1/2
?K 0
?i 1/2 ?i - 1/2

• J(?c0) 1/2 ? in ?c0 rest-frame m 1/2
  along z (quantization) axis
• no angular momentum projection w.r.t.
  quantization axis ? O- helicity, ?i 1/2
• final state helicity ?f ?f (?0) - ?f
  (pseudoscalar) 1/2
• Decay amplitude for O- ? ?0 K-
• ?Total Intensity

Does not depend on li Wigner-Eckart theorem
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Spin measurement of W-
Background-Subtracted Efficiency-Corrected
? Fit Prob 10 -17
JW 1/2
JW 3/2
? Fit Prob 0.64
? Fit Prob 10 -7
JW 5/2
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Spin measurement of W- from Xc0 ? W- K, W- ?
L0 K- decays
Angular Distribution Parametrizations for JO3/2
hypothesis
Background-Subtracted Efficiency-Corrected
Negligible Decay Asymmetry Parameter
b 0.04 0.06
No Asymmetry
b 0
Asymmetry
Fit for b ? b 0.04 0.06
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Spin measurement of Wc0 from Wc0 ? W- p, W- ?
L0 K- decays
Fit parametrization a(1 3 cos2?) for JO 3/2
hypothesis ? Fit Prob 0.69 J(W-) 3/2,
consistent with
results from Xc0 ? W- p
PRL version ready for review comm
Conclusion J(W-) 3/2 Assuming J(Xc0) ,
J(Wc0) lt5/2
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Extending the Spin Formalism to 3-body Decays
Study of X (1530)0 and X (1690)0

• The X (1530)0 Spin from Lc ? (X- p) K
  ? also mass, width info. ?
  amplitude analysis (in progress)? The X (1690)0
  Spin from Lc ? (L0KS0) K
  ? also mass, width info. ? amplitude analysis
  (to be done) ? (X-p)/(LK0) Branching Ratio
  Limit (to be done)

nothing of significance on X resonances has
been added since our 1988 edition. PDG(2004),
p 967
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Reconstructed Lc ? X- p K, X- ? L0 p-
Events
m(X- p) ? Lc mass-signal region ? m(X-
p) ? Lc mass-sideband region .



. m(X- p) ? (Lc)
mass-sideband-subtracted
Data 230 fb-1
Uncorrected
(Lc)Mass-sideband-subtracted
Uncorrected
? Lc ? X- p K
? X(1530)0 ? X- p
PDG mass
13
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Resonant Structures in Lc ? X- p K, X- ? L0
p- Events
Only obvious structure X (1530)0 ? X- p
Lc signal region
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Spin measurement of X0(1530) from Lc ?
X0(1530) K, X0(1530) ? X- p decays
a(1 3 cos2?) for J3/2 hypothesis
Uncorrected cos?X Spectrum
Clear 13cos2? structure
X0(1530) Signal Region Not mass-sideband-subtrat
ed
X0(1530) Mass-Sideband Regions

• Skewed distribution due to
• Efficiency loss at small angles ? Not big
  effect
• (X- p) system decay asymmetry ? S-P wave
  interference (next slides)

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Using the angular structure of X(1530)0 ? X- p
candidates to project
away
background events
Lc ? X- p K Signal Region Uncorrected
sidebands
? Legendre polynomials orthogonality condition
? Weight N x P2(cosq)
For pure spin 3/2 dN/dcosq a(1 3 cos2q)
Use of angular structure to project away the
bkgr.
Lc Signal Region
Projects mass distribution having cos2q component
Lc Low Mass-Sideband Region
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• No cos2q component
• in sideband distributions

Lc High Mass-Sideband Region
100
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Evidence of S-P wave interference in the (X- p)
system produced in the

decay Lc ? X- p K
m(X- p) distribution weighted by P1(cosq)
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S-P wave description of the (X-p) system
produced in the decay Lc ? X- p K
K
Amplitudes describing the (X- p) system
? Total Intensity
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Helicity Formalism (3)
Assume 0 to extract cosq
S-P interference
0 (Assume r1/2 r-1/2)
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towards a measurement of the mass width of
X0(1530)
L 2, 1
p
X0(1530) J3/2
q
K
X0(1530)
l 1 () parity
p
X-
Fit with relativistic Breit-Wigner Function with
L2 l 1 incorporating a Blatt-Weisskopf
barrier factor (R 5 (GeV)-1) and resolution
smearing
p
q
p
q
Fit Params M 1531.6 0.1 (stat.) G 11.9
0.2 MeV
PDG M 1531.80 0.32 G 9.1 0.5 MeV
Uncorrected
P2(cosq) weighted
(Very preliminary)
In progress
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Reconstructed Lc ? L0 KS0 K Events
(Lc)Mass-sideband-subtracted
? X(1690)0 ? L0 KS0
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towards a measurement of the mass width of X
(1690)0 ? L0 KS0
Only obvious structure X (1690)0 ? L0 KS0
S-Wave Breit-Wigner Function ( Linear
bkgr.) with resolution smearing
Uncorrected
Fit Params M 1684.7 - 0.9 (stat.) G 12.0 -
0.2 MeV
Background-subtracted Uncorrected
(Very preliminary)
Stop fit at 1.76
23
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Spin measurement of X(1690)0 from Lc ? X(1690)0
K, X0(1690) ? L0KS0 decays
Uncorrected Background-Subtracted
cos?L Spectrum
Direct Method - Extract signal cosqL
distribution - Requires large sideband
subtraction
Flat ? consistent with J1/2 hypothesis
a(1 3 cos2?) for J3/2 hypothesis
prob 0.2
a(1) for J1/2 hypothesis
prob 0.9
Inconclusive
Spin 1/2 favored ?
Indirect Method
Lc signal region
Uncorrected
Uncorrected
m(L KS) distribution weighted by P2(cosq) ?
Lc signal events
? No cos2q component anywhere ? Spin 1/2
? Spin hypothesis Weight signal events by
P2(cosq)
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towards an U.L. on BR(X (1690)0 ? X- p )/BR(X
(1690)0 ? L0 KS0 )
Uncorrected (L0 KS0) invariant mass Lc ? L0
KS0 K Clear signal for X (1690)0 ? L0 KS0
Lc ? L0 KS0 K
Background-subtracted
Lc ? X- p K
Background-subtracted
Uncorrected (X- p) invariant mass Lc ? X- p
K No signal for X (1690)0 ? X- p
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X0 Production in Lc Xc0, Decays
cancel
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Investigation of Xc,0 Decaysto 3-body Final
States

• Xc ? X- p p ? Xc ? L0 KS0 p ? Xc0 ? L0
  K- p

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Reconstructing Xc ? L0 KS0 p Events
Data 200 fb-1
? DS 0
? DS -1
Cabbibo-suppressed Lc ? L0 K0 p
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Lc ? L0 K0 p Dalitz Plot Analysis
Obvious resonant structures
Mass-sideband-subtracted
K(892)? KS0p?
Large K(892) contrib.
Uncorrected
S(1385)
Mass-sideband-subtracted
Uncorrected
K(892) Yield/ 10 MeV/c2
? S(1385) ? L0 p
Evidence for the decay Lc ? L0 K(892)
? Previously observed C.S. mode Lc ? S
K(892)0
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Excited Charm Baryons
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Excited Xc States
L0 straightforward
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X(3872) BELLE Finds Data Disfavors 0 and 2,
Leaving 1
cc ? 1 is ?c1
Solid lines Experiment Left NR model, Barnes,
Godfrey, Swanson Right Relativized model,
Godfrey, Isgur (Spin) Singlets dotted, Triplets
dashed
X(3872) is too light
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BABAR
230 fb -1
e
e-
Detector Tomography with pKS0 vertices
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