Transcript DsJ and charmed strange baryons at BaBar

* and Charmed
DsJ
Baryons at BABAR
Amir Rahimi
The Ohio State
University
For BABAR Collaboration
Heavy Quarkonium
Workshop
June 27-30, 2006


Outline
Charmed Strange Mesons
*
 DsJ (2317), DsJ(2460), and
DsJ(2860)+
Charmed Baryons
+
++
+
0
 Λc(2940) , Xcc , Xcc , Wc ,
and W-
Charmed Strange Mesons
Charmed Strange Mesons

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
Picture for cs system is still
incomplete
The states DsJ*(2317) and
DsJ(2460) were first
observed by BABAR and
CLEO and confirmed by
Belle (2003)
Masses unexpectedly low
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Amir Rahimi
DsJ*(2317)
DsJ(2460)
Ds*
Narrow widths
Decay pattern consistent
with JP=0+ or JP=1+,
respectively
Possible candidates:

Ds1
Below D*K and DK thresholds
respectively
Only electromagnetic and
isospin-violating strong decays
Kinematically allowed

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Ds2
Ds
cs meson states
Exotic particles such as fourquark states
Heavy Quarkonium 06
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Charmed Strange Mesons
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Comprehensive study of decays to Ds+ plus
BABAR: 232 fb
one or two p, p0, or g’s.
Submitted to PRD
-1
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Decay pattern if JP=0+ or JP=1+, respectively
Ds+p0 only decay
mode observed
for DsJ*(2317)+
Amir Rahimi
Heavy Quarkonium 06
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DsJ*(2317)+  Ds+p0
N=3180±80

(Ds*(2112)+Ds+g) + g
No Indication of neutral
or doubly-charged
partner near 2317 MeV
I=0
reflection
DsJ(2460)+Ds+p0g
reflection
Ds*(2112)
signal
Circles: Ds
sidebands
m  (2319.6  0.2  1.4) MeV/c2
  3.8 MeV @ 95%CL
Amir Rahimi
Heavy Quarkonium 06
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DsJ(2460)+Ds+g / Ds*(2112)+p0
Ds+g
DsJ(2460)+Ds+
g
DsJ(2460)+  Ds*(2112)+p0
Open points:
Ds sidebands
Open points:
Ds sidebands
N=560±40
(DsJ*(2317)+Ds+p0)+g
reflection
(Ds*(2112)+Ds+g) +gg
reflection
N=920±60
B( DsJ (2460) +  Ds+g )
 0.337 0.036 0.038
+
+ 0
B( DsJ (2460)  Ds p g )
Amir Rahimi
Heavy Quarkonium 06
BABAR: 232 fb-1
Submitted to PRD
hep-ex/0604030
6
DsJ(2460)Ds+p+pBABAR: 232 fb-1
N=6±3
DsJ*(2317)
N=123±15
DsJ(2460)
N=193±22

Ds1(2536)

No indication of
DsJ*(2317)+
Also observe Ds1(2535)+
m  (2460.2  0.2  0.8) MeV/c2
  3.5 MeV @ 95%CL
m  (2534.6  0.3  0.7) MeV/c2
  2.5 MeV @ 95%CL
B( DsJ (2460) +  Ds+p +p  )
 0.077 0.013 0.008
+
+ 0
B( DsJ (2460)  Ds p g )
Amir Rahimi
Heavy Quarkonium 06
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DsJ(2460) Absolute Branching Fractions
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BB sample with one B fully reconstructed 
Study decays of BD(*)+,0(Ds(*)-) X
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Observe DsJ(2460) signal in the recoil mass, mx
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Mass and momentum of X inferred from the kinematics of
the two body B-decay
BABAR: 210.5M BB
p
D*
eSubmitted to PRD
hep-ex/0605036
Bsignal
Breco
e+
D*
X
Amir Rahimi
Heavy Quarkonium 06
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DsJ(2460) Absolute Branching Fractions,
cont.
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First measurement of absolute BF’s for
BD(*)+,0DsJ(2460)- decays, e.g.

B(B0 D*+DsJ(2460)-)=(0.88±0.0.2±0.14)%
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BD * DsJ (2460)+, DsJ(2460)+Ds+g / Ds*(2112)+p0/Ds+p+p- to obtain
absolute BFs:
Combine with previously measured, exclusive product
BF’s
( )
Preliminary
B(DsJ(2460)+ D*s(2112)+p0)=0.56±0.13±0.09 (Ds*+ Ds++g)
B(DsJ(2460)+ Ds+g)=0.16±0.04±0.03
B(DsJ(2460)+ Ds+p+p-)=0.04 ± 0.01
Sum of BFs for DsJ(2460)+ decaying to p0/g/p+p  76±20%
B(D+s  fp+)= (4.62±0.36±0.51)%
as determined in this analysis
Amir Rahimi
Heavy Quarkonium 06
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Observation of a New Ds Meson Decaying
to D0K+, D0 K- p+
BABAR: 240 fb-1
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New structure at 2.86GeV/c2
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Not observed in D0 sidebands
Not observed in e+e-ccX MC
Not due to D* reflections
Reflection from Ds1(2536)+
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Dsj (2536)+ reflection
Ds1D*0K+, D*0D0p0/g
Narrow structure at threshold
Ds2(2573)+ signal
Broad structure at around 2.7
GeV/c2
Amir Rahimi
Heavy Quarkonium 06
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Other observations of DsJ(2860)+
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Similar structure were observed in
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D0K+, D0 K- p+p0
D+K0S, D+ K-p+p+
872±139 events
(6.3 s)
Need extra structure around 2.7 GeV/c2
(fits better with a Gaussian).

Activity in this region seen in the D0 sidebands
at very low p*
Mode
Mass(MeV/c2)
(MeV/c2)
DsJ(2860)+
2856.6±1.5±5.0
48±7±10
Ds2(2572)+
2572.2±0.3±1.0
27.1±0.6±5.6
X(2680)+(if fitted
using a Breit Wigner):
2688±4±2
112±7±36
1099±214 events
(5.1 s)
D+ K-p+p+
585±212 events
(2.8 s)
Removing the DsJ(2860)+ from the fit:
Dc2108 for DNDF5
No evidence for DsJ(2860)+ to D*K decays
 implies natrual spin-parity JP = 0+, 1-, 2+, 3Amir Rahimi
Heavy Quarkonium 06
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7-foot Bubble Chamber
Charmed
Baryons
Discovery of the Charmed Baryon (BNL, 1975)
Discovery of W- Particle (BNL, 1964)
New Charmed Baryon: Λc(2940)+
First evidence for “bare
charm” including c and
Sc++ came from BNL
group
+c  c [du]

Observed in cc continuum events in the
decay mode D0p (D0K-p+, K-p+p+p-)
BABAR: 287 fb
New state ( > 7s):
Submitted to PRL
-1

m  (2939.8  1.3  1.0) MeV/c
  (17.5  5.2  5.9) MeV

Preliminary
2
First observation of
Λc(2880)+D0p
Λc(2880)
N=2280±310
(>7 σ)
N=3020
±220
Λc(2940)
m  (2881.9  0.1  0.5) MeV/c2
  (5.8  1.5  1.1) MeV

No structure in D+p
 No doubly-charged
partner for either state

Amir Rahimi
No isospin partners
Heavy Quarkonium 06
D0 sidebands
D0p
13
Doubly Charmed Baryons
In a u,d,s,c SU(4)
scheme, the ground
states occupy the top
level of a 20'-plet.
Double-charm baryons
Six ground states:
three with JP = ½+
three with JP = 3/2+
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Bjorken has estimated several branching fractions.
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Amir Rahimi
B(Ξcc+ → D0 Λ p+) ~ 7.0%
B(Ξcc++ → D0 Λ p+ p+) ~ 5.0%
B(Ξcc++ → Λc+ K- p+ p+) ~ 5.0%
B(Ξcc++ → Ξc0 p+ p+) ~ 4.5%
B(Ξcc+ → Λc+ K- p+) ~ 3.0%
B(Ξcc+ → Ξc0 p+) ~ 1.5%
Many theories predicted masses ~ (3.5-3.8) GeV/c2
M(Ξcc+ - Ξcc++) ~ 1 MeV/c2
Predicted lifetimes: ~ (0.1-1.0) ps
Heavy Quarkonium 06
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Doubly Charmed Baryons

No significant signals
in this analysis for:


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
Xcc++ → c+ K- p+ p+
Xcc++ → Xc0 p+ p+
Xcc+ → c+ K- p+
Xcc+ → Xc0 p+
five double charmed
baryons

Xcc+ → c+ K- p+
Xcc+ → D-pK

Ξc0π+ p*> 2
GeV/c
95% C.L.
SELEX reports signal for


Λc+K–π+ p*>2.3 GeV/c
Λc Sidebands
Λc+K–π+π– p*>2.3 GeV/c
Ξc0π+π+ p*> 2 GeV/c
at m=3519±1 MeV/c2
also sees Xcc++
Null results also reported
by Belle and FOCUS
Λc+→pK–π+
Ξc0→Ξ–π+
232 fb–1
232 fb–1
95% C.L.
95% C.L.
Amir Rahimi
Heavy Quarkonium 06
< 1.3 fb
< 3.4 fb
95% C.L.
95% C.L.
15
Study of Wc0 Production and Decay
hep-ex/0507011
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Properties of Wc0 baryon not well know
(few observations of its production &
decay)
Observation of Wc0 → W- p+ at 5s
level
Large uncertainties in previous
measurements of ratio of B.F.


high lumi  improved measurements
using larger sample
First measurement of this ratio of
Branching Fractions
Ratios of Efficiency Corrected Yields
Wc0 B.R.
BABAR
Line Shape:
Triple Gaussian (same mean)
Linear background function
Yield = 138.5 ± 14.8
HWHM = 7 MeV/c2
225 fb-1
Data
Wp+
Yield = 29.9 ± 13.6
HWHM = 5 MeV/c2
XKp+p+
PDG 2005
Yield = 11.8 ± 7.5
HWHM = 5 MeV/c2
Wp+pp+
Amir Rahimi
Heavy Quarkonium 06
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PRODUCTION OF Wc0 CANDIDATES

Wc0 → W-π+
Clear evidence of
Wc0 production
from B decays is
visible at low p*

All Data
Absent in off peak
data
First significant
evidence for
Wc0 production
from B decay
●
data
▬ e+e- → cc signal MC
(GeV/c)
Off-Peak Data
(GeV/c)
Amir Rahimi
Heavy Quarkonium 06
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2
2
1
2
A1/ 2  1/ 2 D1J/ *2 1/ 2 (f ,q ,0) +  1/ 2 DJ1*/ 2 1/ 2 (f ,q ,0) 




2
2
2
1
2

A1/ 2  1/ 2 d1J/ 2 1/ 2 (q ) +  1/ 2 d J1/ 2 1/ 2 (q ) 




2
2
2
1
2
+
A1/ 2  1/ 2 d1J/ 2 1/ 2 (q ) +  1/ 2 d J1/ 2 1/ 2 (q ) 




2
0
+
2
2

Measure spin of W- from XA
KA and
Wc0W-p+

c 1W

/2
1 / 2
 0 K
  ( 1 / 2   1 / 2 )


WDefine
2
2
A
+
A


10
/2
 1/ 2
 0
0
+
The W- Spin Measurement


Present analysis assume that the Xc , Wc , and 
have spin 1/2
The L angular distribution obtained for spin
hypothesis JW = 1/2, 3/2, and 5/2:
 I  1 +  cosq
Xc0
Wc0
J=1/2
(
W- was discovered
at BNL
(
)) J=3/2
I
1
1 + 3 cos2 q +  cosq 9 cos2 q  5
4
I
1
1  2 cos2 q + 5 cos4 q +  cosq 25 cos4 q  26 cos2 q + 5
4
(
(
)) J=5/2
 maybe non-zero as a consequence of parity violation in charm baryon and W- weak decay
Pseudoscalar
Amir Rahimi
q
Hyperon
Charm
baryon restframe
Hyperon
daughter
Hyperon rest- quantization
frame
axis
Pseudoscalar
Heavy Quarkonium 06
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The W- Spin Measurement

Using Xc0W-K+, W0 K
Background-Subtracted
Efficiency-Corrected
Xc0W-K+,
Data
~ 116 fb-1

Negligible Decay Asymmetry
Parameter for JΩ=3/2


 = 0.04 ± 0.06
Background-subtracted
Efficiency-corrected
W0W- p+
Verify using Wc0W-p+


Fit prob = 0.69
Consistent with result from
Xc0W-K+ result of J(W-) = 3/2
Conclusion: J(W-) = 3/2 [Assuming J(Xc0) = J(Wc0) = 1/2]
Amir Rahimi
Heavy Quarkonium 06
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Summary

Did a comprehensive study of DsJ*(2317) and
DsJ(2460) decays

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Observed new strange meson decaying to DK
system, DsJ(2860)+
Observed new charmed Baryon, Λc(2940)+
Observed Λc(2880)+D0p
Studied Wc0 production and decay mechanism


Masses unexpectedly low
Measured DsJ(2460) absolute branching ratio
First significant evidence for Wc0 production from B
decay
Measured W- spin
Amir Rahimi
Heavy Quarkonium 06
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Backup Slides
Production of hidden and open charm
states


Production in B decays

~380x106 BB events

provides access to
inclusive measurements
of absolute branching fractions
W
B
q
e+e-!cc



b
fragmentation
~455x106 events
spectroscopy of open charm
states with high precision
c
c
charmonium
open charm
s (*)
K
s
q
D(s)(*)
W
c
c
b
B
D(*)
q
q
c
Initial state radiation (ISR) e+e-!gISR(cc)

J/ sample: ~1.1x106 events

resonance production in the
energy range

c
q
q
q
q
cc
only production of JPC=1-- states)
Babar offers excellent options for charm / charmonium spectroscopy
Amir Rahimi
Heavy Quarkonium 06
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Reconstruction
g
p0


Clean
sample
§
§
 well identified K und p candidates
 common vertex required
 Momentum: pCM(Ds)>2.2 GeV/c
 >400.000 reconstructed
Ds!f(K+K-)p+ and
Ds ! K*(K-p+)K+ decays
KK+
g
e-
Ds
p+
e+
Combination of Ds candidates
with further g,p0,p§ of same event
 Momentum: pCM(DsJ)>3.2 GeV/c
Amir Rahimi
Heavy Quarkonium 06
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Reflections in Dsp0
Data
MC
Efficiency /
resolution
Amir Rahimi
Heavy Quarkonium 06
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Reflections in Dsp0g
Upper sideband
Fraction of reflection underlaying signal
estimated from upper and lower
Ds* sidebands
Signal region
Lower sideband
Amir Rahimi
Heavy Quarkonium 06
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Exclusive study of the DK system

Exlusive study of the DK system
in e+e-!cc processes
949k entries
791k entries

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Good kaon / pion identification
Clean KS!p+p- and p0!gg selection
Kinematic fit to common vertex
CMS momentum p*(DK)>3.5 GeV
432k entries
Babar: 240 fb-1
preliminary
Amir Rahimi
Heavy Quarkonium 06
26
Spin measurement of W- from Xc0
→ W- K+, W- → 0 K- decays
Angular Distribution
Parametrizations for JΩ=3/2 hypothesis
Data
~ 116 fb-1
Background-Subtracted
Efficiency-Corrected
Negligible Decay
Asymmetry Parameter
 = 0.04 ± 0.06
7
(
)
No Asymmetry
I
1
1 + 3 cos2 q
4
I
1
1 + 3 cos2 q +  cosq 9 cos2 q  5
4
(
0
(
))
Asymmetry
Fit for  →  = 0.04 ± 0.06
UPPER LIMIT ON RATIO OF BRANCHING
FRACTIONS
For Wc0 → W- p+ p+ p- no significant signal events over bkgr  90% C.L. on ratio
 Toy Monte Carlo inputs for each mode:
▪ measured yields
▪ statistical uncertainties (Gaussian)
▪ systematic uncertainties (Gaussian)
Toy Monte Carlo
90% C.L.
Wc0 B.R.
hep-ex/0507011
Amir Rahimi
Heavy Quarkonium 06
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