Charmed%20mesons%20spectroscopy%20from%20Focus

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Charmed mesons spectroscopy from Focus
F.L. Fabbri Laboratori Nazionali di Frascati INFN
-Italy ICHEP2000, Osaka July 2000
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The searcher for charm
Over 1 million charm particles reconstructed into
D?K? , K2? , K3?
Successor to E687. Includes groups from USA,
Italy, Brazil, Mexico, Korea Designed to study
charm particles produced by 200 GeV photons
using a fixed target spectrometer with upgraded
Vertex, Cerenkov, EM Calorimetry, and Muon id
capabilities.
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Charmed mesons spectroscopy chart (HQS)
In the heavy-quark limit the heavy-quark spin SQ
and the total angular momentum of the
light-quark jqLSq are conserved
F.L. Fabbri
ICHEP2000,
Osaka July 2000
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Event selection for D-wave decays of L1 D
D20
Dp-
K- 2p
D
40K
K
?
?
Entries/5 MeV/c2
?
20K
D
D
?
K
D0
?
?
D
M(D0p ) M(D0)
F.L. Fabbri

ICHEP2000, Osaka July 2000
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The Dp mass spectrum
Dp-
D0 p
(D20 )
(D 2 )
Wrong sign
Wrong sign
PDG -gt D20 Mass 2458.9 - 2.0MeV/c2
PDG -gt D 2 Mass 2459 - 4MeV/c2
The Dp mass spectrum
Dp-
( D10 ,
D20 )
Wrong sign
PDG -gt D10 Mass 2422.2 - 1.8 MeV/c2 D20
Mass 2458.9 - 2.0MeV/c2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Disentangling the D1 e D2 signals in Dp
D Helicity angle distribution for different D
Spin-Parity
F.L. Fabbri

ICHEP2000, Osaka July 2000
Do1 Mass 2419.9 1.5 MeV/c2 (PDG 2422.2
1.8 MeV/c2)
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When Anti-D flag for Do fails
FOCUS PRELIMINARY (stat errors only) Yield
744?99
Mass 2568.1 1.6 MeV/c2 rms 10 1 MeV/c2
D0 K
PDG -gt DsJ Mass 2573.5 - 1.7MeV/c2
Width155-4 MeV/c2
Wrong sign
FOCUS PRELIMINARY (stat errors only)
Yield 41 ? 6
D Ks
Mass 2535.2 0.4 MeV/c2 rms 1.3 ? 0.1 MeV/c2
PDG -gt Ds1 Mass 2535.35-0.34MeV/c2
Width lt 2.3MeV/c2
No phase space for DK
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Modeling the background in Dp spectrum
McFOCUS simulation code
-
Mass spectrum from cc production with No D
generated
D0?
exponential behavior in the range 2.5-4.5
GeV/c2 confirmed by the wrong sign and by the
side band spectra
D0? ( )
D2
D?- ( )
D2 0
Wrong sign
Wrong sign e-2.35?0.01 e-2.38?0.01
Right sign e-2.53?0.01
e-2.28?0.01 e-2.27?0.01
Right sign e-2.35?0.01
Side band e-2.69?0.04 e-2.67?0.04
Side band e-2.64?0.05 e-2.65?0.05
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Excess of mass once the background is subtracted
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Feed-down contribution for Dp spectrum
Feed- down from MCFocus simulation (PDG masses
and widths assumed)
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Feed-down from D2 D1 via D to Dp final channel
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Fitting the mass excess in the D0 p spectrum
Exponential backg. D1 and D2 Feed-down a
D-wave BW convoluted with 7 MeV/c 2
experimental resolution
c2/ndf 3.1
G72?4MeV/c2
0
D2
GPDG ( )258-7 MeV/c2
Exponential backg. D1 and D2 Feed-down a
D-wave BW a S-wave BW convoluted with 7 MeV/c
2 experimental resolution
Feed-down peaks from D2 and D1
c2/ndf 1.8
G29?1MeV/c2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Fitting the mass excess in the D p- spectrum
Exponential backg. D1 D2 Feed-down a D-wave
BW convoluted with 7 MeV/c 2 experimental
resolution
c2/ndf2
G55?3MeV/c2
GPDG ( )23?5 MeV/c2
Exponential backg. D1 and D2 Feed-down a
D-wave BW a S-wave BW convoluted with 7 MeV/c 2
experimental resolution
Feed-down peaks from D2 and D1
c2/ndf0.9
G30?2MeV/c2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Soft pion contribution to the combinatorial
backg.
Shoulder probably due to soft pions from missed
D
D2 M 2468.2?1.5MeV/c2 G
28.6?1.3MeV/c2
McFOCUS simulation code
D ? D0 p
Sostituire
If Pp gt 10 GeV

D2 ? D0?
D2 M 2468.5?2.1 MeV/c2 G30.3?3.6 MeV/c2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Mass and width systematic studies
D2
D2
D2 FOCUS new measurements PRELIMINARY
Mass Width D2
2468.2?1.5?1.4 MeV/c2 28.6?1.3?3.8 MeV/c2 D20
2463.5?1.5?1.5 MeV/c2 30.5?1.9?3.8 MeV/c2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Conclusions

• Focus has collected about
• 106 charm meson states
• 0.5 104 excited charm decays
• The study of Dp mass spectrum gives new
  preliminary
• values of the masses and widths for the D2 meson
  
• Mass
  Width
• D2
• FOCUS 2468.2?1.5?1.4 MeV/c2
  28.6?1.3?3.8 MeV/c2
• PDG 2459?4 MeV/c2
  258-7 MeV/c2
• D20
• FOCUS 2463.5?1.5?1.5 MeV/c2
  30.5?1.9?3.8 MeV/c2
• PDG 2458.9?2.0 MeV/c2 23?5
  MeV/c2

F.L. Fabbri

ICHEP2000, Osaka July 2000
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QUESTION AND UTILITY SLIDES
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F.L. Fabbri

ICHEP2000, Osaka July 2000
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Dsj ? D0 K

Conclusion Getting confident on MCs capability
to reproduce feed down shapes
Data
McFocus
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Fitting the mass excess in the D0 p spectrum
Dpic_exp_2
Dpic_exp_bws_2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Fitting the mass excess in the D p- spectrum
Dpin_exp_2
Dpin_exp_bws_2
F.L. Fabbri

ICHEP2000, Osaka July 2000
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Feed-down contribution for Dp spectrum
Feed- down from D1 MCFocus simulation (PDG masses
and widths assumed)
F.L. Fabbri

ICHEP2000, Osaka July 2000