1. Double Heavy Hadrons at LHC Sino-French Workshop Dec. 11-15, 2006
Chao-Hsi Chang (Zhao-Xi Zhang)
ITP, AS, Beijing
Introduction
General Feature
1. Bc Meson
2. Double Heavy Baryons
3. Susy-Hadrons
Studies at LHC
Dec , 2006
Sino-French Workshop

2. Introduction Heavy Flavors: Double Heavy Hadrons:
Light Quarks: u, d, s, ( m < ChΛ )
Heavy Quarks: c, b, (t) ( m > ChΛ )
The Lightest S-quark:
Double Heavy Hadrons:
Mesons:
Dec , 2006
Sino-French Workshop

3. Introduction Baryons: SUSY-hadrons: Dec. 11-15, 2006
Sino-French Workshop

4. Introduction Theoretical Interests:
QCD binding systems: Non-relativistic nature
Potential model or lattice QCD (spectroscopy; transitions between excited states and the ground state etc).
Heavy flavor physics (weak decays; c, b decays; CKM matrix elements Vcb, Vcs, Vub, Vcd, etc).
Production mechanisms (hadronic production)
etc.
Dec , 2006
Sino-French Workshop

5. Heavy quarkonium production puzzle
Color-octet mechanism is introduced
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Sino-French Workshop

6. The polarization puzzle (J/ψ, R-I)
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Sino-French Workshop

7. The polarization puzzle (J/ψ, R-II)
Dec , 2006
Sino-French Workshop

8. The polarization puzzle (Υ)
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Sino-French Workshop

9. General features
1. Bc Meson: double heavy-flavor mesons (explicit flavored unique in SM)
a). Spectroscopy (PM or BS equation QCD inspired):
Dec , 2006
Sino-French Workshop

10. General features (Bc spectroscopy)
under instantaneous approximation
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Sino-French Workshop

11. General features b). Bc decay (explicit flavored so weak decay only):
Bc lifetime: weak decay only (no strong &EM decay)
According to spectator model and B & D mesons’ lifetime measurements: we may obtain
More careful estimate: with optical theorem estimate the partial width
as follows:
within vertex detector ability
Dec , 2006
Sino-French Workshop

12. General features (Bc decay): : : :
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Sino-French Workshop

13. General features (Bc decay)
The results for various decays
Pure leptonic (radiative) decays : :
The radiative decays escaped from chiral suppression !
Dec , 2006
Sino-French Workshop

14. General features (Bc decay)
Semileptonic decays (S-wave product):
One I-W function
Dec , 2006
Sino-French Workshop

15. General features (Bc decay)
Semileptonic decays (P-wave product or ):
Two I-W functions
Spectrum of charged lepton in the decays:
Recoil one
Normal one
Dec , 2006
Sino-French Workshop

16. General features (Bc decay)
Nonleptonic decays (S-wave product):
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Sino-French Workshop

17. General features (summary of Bc decay)
The lifetime is quite long that the vertices of
production and decay can be detected by vertex
detector experimentally (in the window).
Sizable decay channels are rich.
The branch ratio of the decay to is
quite great.
The branch ratio of decay to or is large.
Radiative pure leptonic decays escape from chiral
suppression.
…….
Dec , 2006
Sino-French Workshop

18. General features (Bc production)
Direct production:Only at very high energy hadronic colliders (Tevatron and LHC) numerous Bc mesons can be produced for experimental studies. Maybe some clue for solving the puzzle for polarization of J/ψ, ψ’ etc.
Gluon-gluon fusion mechanism dominant
36 Feynman diagrams for complete calculations
QCD factorization:
Dec , 2006
Sino-French Workshop

19. General features (Bc production)
The lowest order calculations:
uncertainties from:
Dec , 2006
Sino-French Workshop

20. General features (Bc production)
Uncertainties: quite great; sensitive to Q2, mc
high order calculation can suppress them
but too complicated.
Cross-section at LHC is higher than that at Tevatron by a factor ~101
Dec , 2006
Sino-French Workshop

21. General features (P-wave excited Bc production)
Cross-section at LHC is higher than that at Tevatron by a factor ~101 A: B: C: D:
LHC
TEVATRON
Dec , 2006
Sino-French Workshop

22. General features (Bc production)
Indirect production (feasible in exp. via top-quark decay)
At LHC enormous top and anti-top pair can be produced ~108/year and can reach to much above the threshold of the production.
Indirect production also may via W, Z decay (not repeat here).
Dec , 2006
Sino-French Workshop

23. General features (double heavy baryons)
Two heavy quarks play an essential role of the double baryon’s core, while the light quark plays just as a ‘spectator’:
The double heavy baryons have quite similar features in decays and production as Bc meson, but some difference due to the additional light quark acting as a ‘spectator’. NRQCD also works.
Dec , 2006
Sino-French Workshop

24. General features (double heavy baryons)
Decay (similar to Bc meson, but there is no annihilation, lifetime little longer).
Direct production (similar to Bc meson, but there are two configurations in color anti-triplet and color sixtet)
production:
Dec , 2006
Sino-French Workshop

25. General features (SUSY hadrons)
The possibility has not been ruled out yet.
SUSY-Hadrons
QCD bound states, but in different spin (statistics);
The top-squark pairs may be produced a lot at LHC.
Dec , 2006
Sino-French Workshop

26. General features (SUSY hadrons)
For comparison
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Sino-French Workshop

27. General features (SUSY hadrons)
One can expected to observe such SUSY hadrons at LHC ! Note that the cross section of the SUSY hadrons (top-squark with a light quark) can be greater than the presented ones by a factor ~102—3.
Dec , 2006
Sino-French Workshop

28. Studies at LHC
The experimental studies of the double heavy hadrons only at the preliminary stage.
CDF (D0) at Tevatron has observed Bc.
SELEX seems to have observed
The production cross-sections are bigger than those at Tevatron by a factor 10 and more.
M.C. generators for producing Bc directly at hadronic colliders are ready.
Studies via ‘indirect production’ should be in consideration range
Etc.
Dec , 2006
Sino-French Workshop

29. Studies at LHC (new version of M.C. simulation generator BCVEGPY)
The version BCVEGPY2.0 (PYTHIA):
The amplitudes for the hadronic production of the color-singlet components corresponding to the four P-wave states and
are included;
The amplitudes for P-wave production via the two color-octet components and are included;
The integration efficiency over the momentum fractions are improved.
Version BCVEGPY2.1 (PYTHIA):
Technical improvements are involved.
CPC Lib. & hppt://
The core part of BCVEGPY has been embedded in ATHENA (ATLAS group), Gauss (LHCb group) and SIMUB (CMS group) already.
The generator for will be ready soon.
Dec , 2006
Sino-French Workshop

30. Studies at LHC (indirect production)
I am told that double heavy hadrons via direct production may be investigated for LHCb always, while for CMS (ATLAS) only when the low luminosity runs.
I suspect that the indirect production via top-quark decay for CMS (ATLAS) will become comparatively important when high luminosity runs: more than 108 top pairs per year (L=1034) especially for SLHC a possible upgraded version of LHC.
Dec , 2006
Sino-French Workshop

31. Studies at LHC (via top-quark decay)
The cross-section for top and anti-top quark pair production at LHC:
Most pairs being produced much above the threshold and very large top-quark mass, the decay product or or their excited states of top may have a large transverse momentum. It is a great advantage in comparison with Tevatron.
Therefore more further careful M.C. simulation is needed.
Note: since W and Z boson cannot be produced so enormous at LHC, so they may not be feasible to use as indirect source of double heavy hadrons.
Dec , 2006
Sino-French Workshop

32. Studies at LHC (SUSY hadrons)
A new type hadrons
The hadrons with strange spin:
Half integer spin
Integer spin
Therefore the ‘light’ SUSY hadrons may be ‘easy to be observed’.
Dec , 2006
Sino-French Workshop

33. Thank you !
Dec , 2006
Sino-French Workshop