1. Search for Heavy Quark Resonances in Two-Photon collisions in the L3 detector Mikhail Levtchenko (INFN Milano)
Search for c meson (status)
Search for b meson (status)
Outlook
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

2. Two-Photon physics Resonance formation
Outgoing e-e+ are undetected (“No TAG”)  Quasi-real photons
Final state  neutral unflavored meson R ,with C=+1
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

3. c(z-pole) Was studied in z-pole data L=140pb-1 Channels: +- +-
+-K+K-
Ks0 K
K+K- 0
+-
+-’
+-
Physics Letters B 461 (1999)
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

4. c(z-pole)
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

5. bTheoretical Prediction
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

6. Previous searches
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

7. ALEPH
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

8. c/b High energy data: L=610pb-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:
+-, 
K+K-+-
Ks0 K
K+K-0
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

9. c/b Selection +- +- and +-K+K-
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
K+K- 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()|< 40MeV
+-’, ’ +-
reconstruction with |M(+-0 )-M(’)|< 50MeV, ’ 0
+-
|M(0 )-M()|< 25MeV
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

10. c/b Selection a) Effective mass of two photons in K+K- 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
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

11. e+e-e+e-K+K-0 c Data(fit): M(c )=2.965+/-0.017 GeV
0 reconstructed from 2
P(K+K-)/(P(+-)+P(K+K-))>20%
Data(fit):
M(c )=2.965+/ GeV
(c )=0.092+/ GeV
MC(fit):
(generated with PDG parameters)
M(c )=2.961+/ GeV
(c )= / GeV
=3.68+/-0.08
Nev=30+/-15
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

12. e+e-e+e-K+K-0  b M=9.168 +/-0.300 GeV M=9.519 +/-0.300 GeV
0 reconstructed from 2
P(K+K-)/(P(+-)+P(K+K-))>50% 
M= / GeV
M= / GeV
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

13. e+e-e+e-+- c Data(fit): M(c )=2.953+/-0.025 GeV
 reconstructed from 2
Two tracks required
Data(fit):
M(c )=2.953+/ GeV
(c )=0.067+/ GeV
MC(fit):
(generated with PDG parameters)
M(c )=2.965+/ GeV
(c )= / GeV
=5.42+/-0.15
Nev=35+/-10
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

14. e+e-e+e-+-  b  reconstructed from 2 Two tracks required
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

15. e+e-e+e-+-’0 c Data(fit): M(c )=2.973+/-0.045 GeV
’ reconstructed from 0
Four tracks required
Data(fit):
M(c )=2.973+/ GeV
(c )=0.071+/ GeV
MC(fit):
(generated with PDG parameters)
M(c )=2.981+/ GeV
(c )= / GeV
=0.41
Nev=5+/-4
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

16. e+e-e+e-+-’0  c M=9.35 +/-0.320GeV 0 reconstructed from 2
0 
M=9.35 +/-0.320GeV
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

17. e+e-e+e-KsK c Data(fit): M(c )=2.956+/-0.022 GeV
Geometrical reconstruction of the
secondary vertex of Ks0 +-
M(+-)=M(Ks0)30MeV
/K separation by dE/dx
Data(fit):
M(c )=2.956+/ GeV
(c )=0.064+/ GeV
MC(fit):
(generated with PDG parameters)
M(c )=2.975+/ GeV
(c )= / GeV
=2.23+/-0.05
Nev=35+/-12
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

18. e+e-e+e-4tracks c 4K-near threshold 4 - dominated by background
So we are using only 2K2 data
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

19. K+K-+- Data(fit): M(c )=2.989+/-0.011 GeV (c )=0.092+/-0.019 GeV
MC(fit):
(generated with PDG parameters)
M(c )=2.957+/ GeV
(c )= / GeV
=2.52+/-0.05
Nev=30+/-10
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

20. Low statistics channels
a) R+-(+-0)
Nev=4+/-3
b) R+-’(+-)
Nev=1+/-1
c) R+-’(0)
Nev=5+/-4
d) R+-
Nev=8+/-5
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

21. b M=9.89+/-0.32 GeV Events/330MeV 08/04/2003
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

22. b M=9.36 +/- 0.34GeV M=9.89 +/-0.34GeV GeV Events/330MeV 08/04/2003
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

23. c - Sum High energy Data(fit): M(c )=2.965+/-0.017 GeV
Nev=72+/-25
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

24. Summary on c
Weighted average =3.68±0.87(stat)±0.8(sys)±2.0(BR) keV (Published:6.9±1.7(stat)±0.8(sys)±2.0(BR) keV)
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

25. 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
π/K misidentification ~ 50 MeV
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

26. Summary on b The observation is compatible with the background CL=4%
Upper limits on (b)xBR:
(b)xBR(K+K-0) <2.83 keV
(b)xBR(4 tracks) <0.21 keV
(b)xBR(4 tracks 0) <0.50 keV
(b)xBR(6 tracks) <0.33 keV
(b)xBR(6 tracks 0) <5.50 keV
(b)xBR(+-’) <3.00 keV
At 95% of C.L.
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003

27. 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
M.Levtchenko Search for heavy quark resonances in Two-Photon collisions in L3
08/04/2003