Charmed Hadron Spectroscopy At

1
Charmed Hadron Spectroscopy At

• Introduction
• D
• DS
• SC , SC
• LC

Robert K. Kutschke Fermilab FCP01 March 7, 2001
2
At Fermilab g BeO charm
g
3
FOCUS The Successor to E687

• Segmented BeO Target interleaved with SMDs.
• Upgraded
• EM Calorimetry.
• Cerenkov system.
• Muon ID capability.
• Data taken in 1996-1997.
• More than 10 times the Luminosity
• 106 reconstructed Golden Mode Decays
  D0?K-p, K-pp-p and D?K-pp.

4
Candidate Driven Vertexing

• Find charm candidate good vertex, good particle
  ID.
• Seed primary vertex finder with the charm
  candidate.
• Require isolated secondary. One measure L/sL
  cut.
• Add tracks from primary to form Lc p combinations.

5
P-wave Charmed Mesons

• L1 between c and light quark ( qu,d,s ).
• jlight Slight L , approximately good Q
  number if mC LQCD Rosner the hydrogen
  atom of QCD
• Idealized picture is a doublet of doublets.
• Strong decays to D()p ( or D()K for DS )

c
D, D
-
c
q
q
p, r, (K, K)
6
Idealized Picture of P-wave Charmed Mesons
Heavy quark symmetry jl3/2 dominant decays are
D-wave jl1/2 dominant decays are S-wave
Reminder D JP 0- D JP 1-
JlightP 1/2-
7
Angular Momentum and Parity Selection Rules
13/2 Decays via D-wave 11/2 Decays via S-wave
All 5 decays in the multiplet are described by 2
parameters, the S wave and D wave
amplitudes (x Wigner 6-j, x phase space)
8
Whats Overly Simplified in the Ideal Picture?

• Doublets may overlap ( which 1 is more
  massive?)
• Is suppression of S wave widths complete?
• Ds1 right at threshold for DK
• Very narrow, G
• Data suggests mostly S-wave!

9
S-Wave Charm States at FOCUS
D0 ? K- p
D
D0
D0 ? K- p p p-
Entries / 5 MeV/c2
D ? K- p p
For S/B 7,
330,000 D candidates
(GeV/c2)
M(Kp or K3p)
M(Kpp)
D ? D0 p
D
30000
K- p
20000
K- p p p
Entries / 0.5 MeV/c2
10000
For S/B 5,
?? 70,000 D candidates
0.140
0.144
0.148
(GeV/c2)
M(D0p)-M(D0)
10
D0p and Dp- Mass Distributions
Feed down from D2, D1 partial reconstruction
Feed down from D2, D1 partial reconstruction
Entries / 10 MeV/c2
Entries / 10 MeV/c2
FOCUS
FOCUS
Wrong sign
Wrong sign
M(D0p)-M(D0)1.8646 (GeV/c2)
M(Dp-)-M(D)1.8693 (GeV/c2)
Shorthand MF(D0p)
MF(Dp-)
11
Get Feed-down Line Shapes from Monte Carlo
MC
MC
12
Beyond Signal Region all Shapes are Exponential
D20 ? D?-
D2 ? Do?
Right sign e-2.35?0.01
Right sign e-2.53?0.01
Entries / 10 MeV/c2
Entries / 10 MeV/c2
Wrong sign e-2.38?0.01
Wrong sign e-2.27?0.01
Side band e-2.67?0.04
Side band e-2.65?0.03
MF(D0p) (GeV/c2)
MF(Dp-) (GeV/c2)
13
Fitting the D0p Mass Distribution (1)
Fit Results
Terms in the Fit
c2 / dof 3.1
Entries / 10 MeV/c2

• Signal D-wave Rel. BW, convoluted with a
  gaussian, s 7 MeV/c2.
• Exponential extrapolated from 2.4 4.5 GeV/c2.
• MC D1 Feed-down.
• MC D2 Feed-down

G72?4 MeV/c2
FOCUS
Get horrible fit!
MF(D0p) (GeV/c2)
( GPDG (D2) 25 ? 8 MeV/c2 )
14
Fitting the D0p Mass Distribution (2)
Fit Results
M2468.2?1.5 MeV/c2
c2 / dof 3.1
G 28.61.3 MeV/c2
Entries / 10 MeV/c2
c2 / dof 1.8
G72?4 MeV/c2
FOCUS
FOCUS
MF(D0p) (GeV/c2)
MF(D0p) (GeV/c2)
Add 5th term to the fit S-wave Rel. BW
15
Reducing BG from Soft p From D Decays
M 2468.5 ? 2.1 MeV/c2 G 30.3 ? 3.6
MeV/c2
Entries / 10 MeV/c2
MC
D2
FOCUS
pp 10 GeV/c
MC
MF(D0p) (GeV/c2)
16
Fitting the Dp- Mass Distribution
c2 / dof 0.9
GPDG ( D20 ) 23 ? 5 MeV/c2
M 2463.5 ? 1.5 MeV/c2
c2 / dof 2
G 30.5 ? 1.9 MeV/c2
Entries / 10 MeV/c2
Entries / 10 MeV/c2
G 55 ? 3 MeV/c2
FOCUS
FOCUS
MF(Dp-) (GeV/c2)
MF(Dp-) (GeV/c2)
Signal Exp D1 D2
S-Wave Rel. BW
17
D2 Mass and Width Systematics
D2 Width
D2 Mass
D2 Mass MeV/c2
D2 Width MeV/c2
FOCUS D2 Results Mass (MeV/c2)
G (MeV/c2) D2 2468.2 ? 1.5 ? 1.4
28.6 ? 1.3 ? 3.8 D20 2463.5 ? 1.5 ? 1.5
30.5 ? 1.9 ? 3.8
Preliminary
PDG 2000 M2459?4, M02458.9?2.0, G25?8,
G023?5 MeV/c2.
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Dp- Mass Distribution
D10 Yield 889 ? 92
D20 Yield 977 ? 101
1200
Entries / 10 MeV/c2
800
Preliminary
600
400
200
Wrong sign
2.7
2.4
2.1
2.7
(GeV/c2)
M((D0p)p-)-M(D0p)2.0100
Shorthand MF(Dp-)
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Observation of the DS2 and DS1
DS2 ? D0 K ? D KS0
DS1 ? D KS0
D ? D0 ?
D0 ? K-?, K- ???-
D ? K-??
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Observation of the Ds2 at Focus
D0K
DKS0
First observation of the DKS0 mode!
FOCUS
Preliminary
There are some real KS0 in the sideband sample.
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Simultaneous Fits to D0K and DKS0 Spectra
Terms in the fit
Preliminary

• DS2 Signal D-wave Rel. BW
• Smooth background shape
• MC DS1 feeddown shape
• MC DS2 feeddown shape. Significance is not
  stable with cut variations!

• Simultaneous M and G same.
• Errors are statistical only

PDG M 2573.5 1.7 MeV/c2 G 15 5 MeV/c2
First observation of DKS0 mode
22
Observation of the DS1 at FOCUS
Terms in the fit
Preliminary

• DS1 Signal Non Rel BW, convoluted with a
  gaussian.
• Smooth background shape.
• DS2 Signal D-wave Rel BW.

• Errors are statistical only

PDG D 525.35 0.34 MeV/c2 G 90 CL.
M(DKs0)-M(D)
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Some Charmed Baryons
cud
JP
3/2-
Lc(2625)
cdd
cuu
JP
cud
Lc(2593)
1/2-
Sc
Sc
Sc0
3/2
Sc0
Sc
1/2
Sc
Lc?Lc p p
Lc?Lc p
Sc() ?Lc p
Lc
P-Wave Baryon
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Selection of Lc for Sc and Sc0 Studies
Yield12410 ? 180
5000

• 7.89?0.11 MeV/c2

Entries / 5 MeV/c2
4000
S/B 1.7
FOCUS
Cut ? 2s
3000
Sidebands
2000
1000
2.4
2.1
2.2
2.3
(GeV/c2)
M(pK-p)
25
Sc and Sc0 Masses
M(Sc0) M(Lc) 167.38 ? 0.21 MeV/c2
Yield 362 ? 36
SC0 ? LC p-
60
40
( CLEO 2.5 ICHEP 2000
20
167.2?0.1?0.2 MeV/c2 )
Entries / 500 KeV/c2
0.17
0.19
0.15
(GeV/c2)
M(Sc) M(Lc) 167.35 ? 0.19 MeV/c2
SC ? LC p
Yield 461 ? 39
60
FOCUS
40
20
( CLEO 2.5 ICHEP 2000
167.4?0.1?0.2 MeV/c2 )
0.15
0.17
0.19
(GeV/c2)
M(LCp) M(LC)
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Systematic Errors
M(Sc0) M(Lc ) 167.38 ? 0.21 ? 0.13 MeV/c2
M(Sc ) M(Lc ) 167.35?? 0.19 ? 0.12 MeV/c2
M(Sc) M(Sc0) -0.03 ? 0.28 ? 0.11
MeV/c2
Phys. Lett. B488, 218-224, 2000.
27
(No Transcript)
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Observation of Sc ? Lc p0
p0 ? gg Reconstructed in EMCAL.
80
200
N / 1 MeV/c2
N / 3 MeV/c2
60
150
40
100

Yield 118 40
s
50
20
FOCUS
3.04?0.84 MeV/c2
0.2
0.4
0.16
0.20
0.3
0.18
0.14
(GeV/c2)
M(Lc p0) M(Lc)
Preliminary


M(Sc) M(Lc) 168.0 1.0 0.3 MeV/c2


M(Sc) M(Sc0) 0.6 1.0 0.3 MeV/c2
( CLEO hep_ex/0007041 M(Sc) M(Lc) 166.4
0.2 0.3 MeV/c2 )


29
Isospin Mass Differences
Preliminary
Theory has canceling contributions quark masses,
strong potential, Coulomb interaction, hyperfine
( EM QCD ).
30
Natural Widths (MeV/c2)
Signal Shape BW convoluted with a gaussian.
FOCUS
80
80
Preliminary
Entries / 0.5 MeV/c2
60
60
40
40
20
20
s0 1.48? 0.01 MeV/c2
s 1.49? 0.02 MeV/c2
0.20
0.18
0.16
0.14
0.16
0.14
0.18
0.20
(GeV/c2)
M(Lc p) M(Lc)
M(Lc p-) M(Lc)
G(Sc0) 2.58 ? 0.79
G(Sc) 2.53 ? 0.77
( CLEO 2.5 ICHEP 2000 G0 2.4?0.2 ?0.4
G 2.5??0.2?0.4 MeV/c2 )
31
G(Sc) and G(Sc0)
0.51
0.51
-0.56
-0.55
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Observation of Sc and Sc0
Preliminary


Yield 1284 225
Yield 593 146
Stat errs only
300
300
FOCUS
Entries / 1.0 MeV/c2
200
200
100
100
G 9.4 ? 3.7 MeV/c2
G 23.6 ? 4.5 MeV/c2
0.30
0.25
0.15
0.20
0.30
0.20
0.25
0.15
(GeV/c2)
M(Lcp-) M(Lc)
M(Lcp) M(Lc)
DM(Sc0) 232.7 ? 1.2 MeV/c2
DM(Sc) 234.2?1.5 MeV/c2
M(Sc0) - M(Sc) -1.5 ? 1.9 MeV/c2
( CLEO II DM0232.6?1.0?0.8 G013.0?3.7?4.0
DM234.5?1.1?0.8 G17.9?3.8?4.0 )
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Observation of Excited Lc States
Lc(2625) DM 341.6 0.3 MeV/c2
250
Entries / 2 MeV/c2
Preliminary
( PDG 2000 341.7 ? 0.6 )
200
Yield 371 32
150
Lc(2593) DM 308.1 0.7 MeV/c2
100
50
FOCUS
( PDG 2000 308.9 ? 0.6 )
Yield 100 20
0.30
0.35
0.40
0.45
Errors are Stat only.
(GeV/c2)
M(Lcpp-) M(Lc)
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Summary and Conclusions

• Preliminary masses and widths in D and DS
  sectors.
• First observation of DS2? DKS0.
• Confronting a new level of systematics in the
  D sector
• We require something like the expected broad
  state to fit the mass difference spectrum
  successfully.
• Measurements of SC and SC0 Masses and Widths
• Published M(Sc) M(Sc0) -0.03 ? 0.28 ?
  0.11 MeV/c2
• Confirm SC, SC, SC0 previously seen only
  by CLEO II.
• A good start on LC

35
References for Theory on Page 30

• M.A. Ivanov et al., Phys. Lett. B442, 435 (1998).
• M.A. Ivanov et al., Phys. Rev. D60, 094002
  (1999).
• S. Tawfig et al., Phys. Rev. D58, 054010 (1998).
• M.-Q. Huang et al., Phys. Rev. D52, 3986 (1995).
• D. Pirol and T.-M. Yan, Phys. Rev D56, 5483
  (1997).
• J.L. Rosner, Phys. Rev. D52, 6461 (1995).