Search for Heavy Quark Resonances in Two-Photon collisions in the L3 detector Mikhail Levtchenko (INFN Milano)

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Search for Heavy Quark Resonances in Two-Photon
collisions in the L3 detectorMikhail Levtchenko
(INFN Milano)

• Search for ?c meson (status)
• Search for ?b meson (status)
• Outlook

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Two-Photon physicsResonance formation

• Resonance formation

R

• Outgoing e-e are undetected (No TAG) ?
  Quasi-real photons
• Final state ? neutral unflavored meson R ,with
  C1

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?c(z-pole)

• Was studied in z-pole data
• L140pb-1
• Channels
• ??- ??-
• ??-KK-
• Ks0 K???
• KK- ?0
• ??-?
• ??-?
• ??-
• Physics Letters B 461 (1999) 155-166

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?c(z-pole)
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?bTheoretical Prediction
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Previous searches
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ALEPH
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?c/b

• High energy data
• ?L610pb-1
• 4 times bigger statistic

• All decay modes are the same
• PreSelecion is
• 2tracks, 4tracks, 6tracks
• 2tracks 2photons, 4tracks 2photons, 6tracks
  2photons
• Clean signal from ?c
• The most significant decay modes
• ??-?, ????
• KK-??-
• Ks0 K???
• KK-?0

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?c/b Selection

• ??- ??- and ??-KK-
• Four tracks and no photons. Using dE/dx
  measurement ? and K are distinguished with 8 to
  21 misidentification
• Ks0 K???
• Geometrical reconstruction of the secondary
  vertex of
• Ks0? ??-, invariant mass M(??-)M(Ks0) ?30MeV
• KK- ?0
• Two photons reconstructed as ?0 and two tracks
  observed.
• ?c/b ? ??-?0 is forbidden by G parity
  conservation.
• ??-?
• ???? reconstruction, ?? ??-?0 with
• M(??-?0 )-M(?)lt 40MeV
• ??-?, ?? ??-?
• reconstruction with M(??-?0 )-M(?)lt 50MeV,
  ?? ?0?
• ??-
• M(???0 )-M(??)lt 25MeV

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?b Selection
Explored channels

• 2 track events 2 photons
• 4track events
• 1,2 photons
• 6track events
• 2 photons

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?c/b Selection

• a) Effective mass of two photons in KK- ?0
  sample
• b) Effective mass of two photons in ??-? sample
• c) Effective mass of ??- from Ks0? ??-
  secondary vertex
• c) Effective mass of three pions photons in ??-?
  sample

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ee-?ee-KK-?0
?c

• ?0 reconstructed from 2?
• P(KK-)/(P(??-)P(KK-))gt20

Data(fit) M(?c )2.965/-0.017 GeV ?(?c
)0.092/-0.011 GeV
MC(fit) (generated with PDG parameters) M(?c
)2.961/-0.002 GeV ?(?c )0.083 /-0.002
GeV ?3.68/-0.08 Nev30/-15
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ee-?ee-KK-?0
?b

• ?0 reconstructed from 2?
• P(KK-)/(P(??-)P(KK-))gt50

??

• M9.168 /-0.300 GeV
• M9.519 /-0.300 GeV

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ee-?ee-??-????
?c

• ? reconstructed from 2?
• Two tracks required

Data(fit) M(?c )2.953/-0.025 GeV ?(?c
)0.067/-0.017 GeV
MC(fit) (generated with PDG parameters) M(?c
)2.965/-0.003 GeV ?(?c )0.077 /-0.003
GeV ?5.42/-0.15 Nev35/-10
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ee-?ee-??-????
?b

• ? reconstructed from 2?
• Two tracks required

??
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ee-?ee-??-???0?
?c

• ? reconstructed from ?0?
• Four tracks required

Data(fit) M(?c )2.973/-0.045 GeV ?(?c
)0.071/-0.037 GeV
MC(fit) (generated with PDG parameters) M(?c
)2.981/-0.005 GeV ?(?c )0.084 /-0.005
GeV ?0.41 Nev5/-4
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ee-?ee-??-???0?
?c

• ?0 reconstructed from 2?
• ????0?

??

• M9.35 /-0.320GeV

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ee-?ee-KsK?
?c

• Geometrical reconstruction of the
• secondary vertex of Ks0? ??-
• M(??-)M(Ks0)?30MeV
• ?/K separation by dE/dx

Data(fit) M(?c )2.956/-0.022 GeV ?(?c
)0.064/-0.022 GeV
MC(fit) (generated with PDG parameters) M(?c
)2.975/-0.003 GeV ?(?c )0.082 /-0.003
GeV ?2.23/-0.05 Nev35/-12
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ee-?ee-4tracks
?c
4K
2K2?
2K2?
2K2?
2K2?
4K
4K-near threshold 4? - dominated by background So
we are using only 2K2? data
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Data(fit) M(?c )2.989/-0.011 GeV ?(?c
)0.092/-0.019 GeV
KK-??-
MC(fit) (generated with PDG parameters) M(?c
)2.957/-0.002 GeV ?(?c )0.066 /-0.002
GeV ?2.52/-0.05 Nev30/-10
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Low statistics channels
?c

• a) ???R???-?(??-?0)
• Nev4/-3
• b) ???R???-?(??-?)
• Nev1/-1
• c) ???R???-?(?0?)
• Nev5/-4
• d) ???R???-
• Nev8/-5

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?b
Events/330MeV

• M9.89/-0.32 GeV

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?b
Events/330MeV

• M9.36 /- 0.34GeV

• M9.89 /-0.34GeV GeV

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?c - Sum
High energy Data(fit) M(?c )2.965/-0.017
GeV ?(?c )0.084/-0.012 GeV Nev72/-25
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Summary on ?c
Weighted average ?3.680.87(stat)0.8(sys)2.0(BR
) keV (Published6.91.7(stat)0.8(sys)2.0(BR)
keV)
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?b - Sum
Average effective mass M 9.51 0.30 GeV
N(candidates)6, expected BG 2.5 Mass
resolution due to detector effects 300 MeV p/K
misidentification 50 MeV
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Summary on ?b

• The observation is compatible with the background
  CL4

Upper limits on ???(?b)xBR ???(?b)xBR(KK-?0) lt2
.83 keV ???(?b)xBR(4 tracks) lt0.21
keV ???(?b)xBR(4 tracks ?0) lt0.50
keV ???(?b)xBR(6 tracks) lt0.33 keV ???(?b)xBR(6
tracks ?0) lt5.50 keV ???(?b)xBR(??-?) lt3.00
keV At 95 of C.L.
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Conclusion and Outlook

• New ?c results
• Resonance parameters are measured with more
  precision
• Two-photon width is calculated
• New ?b results
• 6 candidates of ?b are well measured and checked
• Upper limit on two-photon width is given
• Both of analysis's are completed