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强子对撞机上的 B 物理研讨会

Hadronic Production of Bc(B*c) Meson Induced by the Heavy Quarks inside the Collision Hadrons. 吴兴刚 ( Xing-Gang Wu ) (ITP). In colarboration with Profs. Z.X. Zhang, C.F. Qiao and J.X. Wang hep-ph/0509040. 强子对撞机上的 B 物理研讨会. Contents. Background. Calculation Technology---GM-VFN Scheme.

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强子对撞机上的 B 物理研讨会

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  1. Hadronic Production of Bc(B*c) Meson Induced by the Heavy Quarks inside the Collision Hadrons 吴兴刚 ( Xing-Gang Wu ) (ITP) In colarboration with Profs. Z.X. Zhang, C.F. Qiao and J.X. Wang hep-ph/0509040 强子对撞机上的B物理研讨会

  2. Contents • Background • Calculation Technology---GM-VFN Scheme • Results Under the GM-VFN and Comparison with the Original FFN results • A Simple Discussion and Summary

  3. 2005 1. Background A) Why we need to study Bc • Bc Meson • Experimental observation (CDF & D0) • Lifetime τ, mass mBc • Decays and Production (hadronic) • Special Interests The decay possibilities for the two heavy flavor comparable Vcb2mb5/Vcs2mc5~O(1) (annihilation~fBc2Vcb2 ) • To study two flavor simultaneously (Vcb, Vcs) • To be a source of precisely tagged Bs mesons, to observe • χc0, χc1, χc2 and hc etc via Bc weak decay etc.

  4. Our main concern is the hadronic production Mechanisms for the hadronic production A)Gluon-gluon fusion ---------------- dominant color-singlet: S-wave: Bc ( 1), Bc*(~2.6); P-wave: Bc*(~ 0.5) color-octet: S-wave: Bc+Bc* (~0.2) B)Quark-antiquark annihilation-----must be light quark color-singlet: S-wave: Bc+Bc* (<0.1) C)Gluon + c-quark (anti-b)-------- intrinsic c or b---GM-VFN scheme color-singlet: S-wave: Bc, Bc* (~1) in small pt regions BCVEGPY

  5. B) Present Status of BCVEGPY BCVEGPY2.0 ( High efficiency ! ) ATLAS (ANTNA?) --- in collaboration with Prof. Z.X. Zhang, Chafik Driouichi and P. Eerola (Lund U.) CMS (SIMUB) --- in collaboration with Prof. Z.X. Zhang, G.M. Chen, S.H. Zhang, A.A. Belkov and S. Shulge (IHEP) D0 --- in collaboration with Prof. Z.X. Zhang, Y.Jiang, N. Han and W.G. Ma (CUST) TEVATRON RUN II --- Generated data used in hep-ex/0505076 (new results of CDF) for analyzing data, with Vaia Papadimitriou

  6. C) Why studying the intrinsic mechanism ? • In most of the present calculations, extended FFN scheme is applied. Including BCVEGPY. • Prof.Qiao has studied the intrinsic charm mechanism to the hadronic production of J/\Psi. • Interesting to study its function to the hadronic production of Bc. Lower order in s and the phase space distribution compensate its higher order in PDF. D) Why GM-VFN scheme and not FFN ? • The mass effects can be consistent treated in both PDF and hard scattering amplitude. • The double counting of gluon-gluon fusion and intrinsic mechanism can be treated well.

  7. 2. Calculation Technology---GM-VFN Scheme

  8. Subtraction method in GM-VFN scheme Intrinsic mechanism

  9. Comparison of evolved PDF and perturbative PDF (SUB)

  10. For hadronic production, we always include a small pt cut, so the fifth term shall be studied here

  11. 3. Results Under the GM-VFN and Comparison with the Original FFN results Subtraction method

  12. Total cross-section for Bc

  13. Total cross-section for Bc*

  14. Pt distributions at LHC

  15. Pt distributions at TEVATRON

  16. Comparison between GM-VFN and FFN at LHC

  17. Comparison between GM-VFN and FFN at TEV

  18. A Rough comparison of GM-VFN and FFN

  19. GM-VFN Strict FFN Extended FFN LHC 1S0 LHC 3S1 TEV 3S1 TEV 1S0

  20. GM-VFN GM-VFN gluon only FFN LHC 3S1 LHC 1S0 TEV 3S1 TEV 1S0

  21. 4. A Simple Discussion and Summary • The old FFN results still are reliable, especially in the large pt regions. • GM-VFN: consistent treat the mass effects and deal well with the double counting problem. • Intrinsic production may give sizable contribution in comparison with the gluon-gluon fusion mechanism. • Intrinsic production is sizable in small pt region (< ~7GeV) and then drops fast. • GM-VFN and FFN results are very close to each other at large pt region. Main difference is in small pt region.

  22. Thanks ! Backup Slides For BCVEGPY

  23. BEGIN BASIC INPUT: NEV,NUMBER,ITMX,VEGASOPEN Y VEGASOPEN IT=0；IT=IT+1 N NUM=0；NUM=NUM+1 IGRADE==1 CALL PHPOINT() CALL AMP2UP() Y Read existed GRADE N Y NUM<=NUMBER N EVNTINIT，PYINIT，UPINIT Y IT<=ITMX N I=0；I=I+1 New GRADE IMPROVE THE MONTE CARLO EFFICIENCY PYEVNT CALL PHPOINT() CALL AMP2UP() USING PYTHIA SUBROUTINES TO GENERATE FULL EVENTS PYFILL() Y I<=NEV N PYDUMP() END The Whole Flowchart for BCVEGPY

  24. Eight Typical States for Gluon-Gluon Light Quark-Antiquark Annihilation CTEQ6L,GRV98MRST2001 Generate More Precise Grade with Existed Grade Color-Octet Mechanism BCVEGPY2.0 designed for all the considered color-singlet/octet S-wave and P-wave states. The flow chart is quite the same as that of the first version BCVEGPY1.0. TWO MORE: IMIX IMIXTYPE

  25. Find out all the independent fermion lines “bases” Decompose the diagram Simplify the fermion lines Expande all the Feynman amplitude over these bases and find out the corresponding coefficients Numerical calculation First Great improvement By Z.Xu etal. Divide the whole amplitude into several gauge invariant groups, and simplify each group with proper gauges. Subtle points：1：how to choose gauge in each group；2：stability of numerical calculation；3：no help for the massive fermion lines. Our improved Helicity approach Derivation of Bc Meson Generator BCVEGPY1.0 S-Wave Production Helicity Amplitude

  26. Schematic Steps For the Improved Helicity Approach Choose proper way to calculate the fermion line find out all the independent fermion lines without taking into account the color factor and the scalar part of the propagator Unit the Same Type Terms As Much As Possible with these independent fermion lines construct all the necessary QED-like Feynman diagrams using basic QED-like Feynman diagrams, with the help of the gluon-gluon and quark-quark symmetry, construct all the QED-feynman diagrams. And decompose all the QCD-like diagrams to be QED-like and also expand over the basic QED-like diagrams. consider the color factors and the scalar part of the proporgator and get the whole helicity amplitude. Arrange all the different helicity amplitudes in a proper order for easy programming.

  27. Derivation of Bc Meson Generator BCVEGPY2.0 Amplitudes for color-Singlet p-wave states The amplitude of the P-wave production involve the derivation over the relative momentum of the constituent quark, so other than taking the helicity approach as has been done in the S-wave case, we take FDC program to do such kind of work for the P-wave production. Amplitudes for color-Octet S-wave states Improved Helicity amplitude approach ! The main difference for color-singlet S-wave is the color flow

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