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Topcolor-A ssisted Supersym m etry

Chun LiuSubjects: Physics >> The Physics of Elementary Particles and Fields

Ithasbeen known thatthe supersym m etric avor changing neutralcurrent problem can beavoided ifthesquarkstakethefollowing m asspattern,nam ely the #12;rsttwo generations with the sam e chirality are degenerate with m asses around the weak scale,while the third generation is very heavy. W e realize thisscenario through the supersym m etricextension ofa topcolorm odelwith gauge m ediated supersym m etry breaking. |

Λb → Σ (?) c πlν? in the heavy quark, chiral, and large Nc limits

Jong-Phil Lee; Chun Liu; H. S. SongSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The decay of Λb → Σ(?)c πlν? processes are calculated in the framework of heavy baryon chiral perturbation theory with help of the 1/Nc expansion. The decay rate distributions over v · v′ where v and v′ are the 4-vector velocities of Λb and Σ(?)c respectively, and over the pion and lepton energies are given. The decay branching ratios amount to about 1.21(0.971)% for Λb → Σcπlν?and 0.798(0.640)% for Λb → Σ?cπlν? by using the baryonic Isgur-Wise function predicted by QCD sum rule (large Nc QCD). |

Reanalysis of the Four-Quark Operators Relevant to #3;b Lifetime from QCD Sum Rule

Chao-Shang Huang; Chun Liu; Shi-Lin ZhuSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Λb matrix element of four-quark operator relevant to its lifetime is reanalyzed by QCD sum rule. The new ingredients introduced are that (1) more vacuum condensates are considered; (2) different quark-hadron duality is adopted; and (3) the possible deviation from the vacuum saturation assumption for the four quark condensates is considered. With κ1 = 4 the related hadronic parameter r is calculated to be (3.6 ± 0.9), and the lifetime ratio τ (Λb)/τ (B0) = (0.83 ± 0.04), which is consistent with the experimental data. |

Electroweak Symmetry Breaking due to Confinement

Chun LiuSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Within the framework of gauge mediated supersymmetry breaking, we con-sider an electroweak symmetry breaking pattern in which there is no con-ventional μ term. The pattern is made appealing through realizing it as low energy effective description of a supersymmetric Yang-Mills theory which is of confinement. Phenomenological implications are discussed. |

Four Light Neutrinos in Singular Seesaw Mechanism with Abelian Flavor Symmetry

Chun Liu; Jeonghyeon SongSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The four light neutrino scenario, which explains the atmosphere, solar and LSND neutrino experiments, is studied in the framework of the seesaw mech-anism. By taking both the Dirac and Majorana mass matrix of neutrinos to be singular, the four neutrino mass spectrum consisting of two almost degen-erate pairs separated by a mass gap ? 1 eV is naturally generated. Moreover the right-handed neutrino Majorana mass can be at ? 1014 GeV scale unlike in the usual singular seesaw mechanism. Abelian flavor symmetry is used to produce the required neutrino mass pattern. A specific example of the flavor charge assignment is provided to show that maximal mixings between the #23;μ ? #23;#28; and #23;e ? #23;s are respectively attributed to the atmosphere and solar neutrino anomalies while small mixing between two pairs to the LSND results. The implication in the other fermion masses is also discussed.PACS numbers: 11.30Hv, 14.60Pq, 14.60.St. |

MeV Tau Neutrino in Gauge Mediated Supersymmetry Breaking Model

Chun Liu; H.S. SongSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

A supersymmetric model which naturally accommodates MeV tau neutrino within the framework of gauge mediated supersymmetry breaking is described. The lepton number violation is originally introduced in the messenger sector of the theory. A large slepton-Higgs mixing mass and asmall lepton-higgsino mixing mass are generated at one-loop. Scalar tau neutrino has non-vanishing vacuum expectation value. These results in a non-zero #23;#28; mass which is in the range of (1 ? 10) MeV. |

EXCITED HEAVY MESONS FROM QCD SUM RULES

Chun LiuSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Orbitally excited L = 1 charm mesons are studied by QCD sum rules in the framework of heavy quark effective theory. The meson masses and the strong decay widths are obtained. This talk is based on our works of refs. 1 and 2 collaborated with Y.B. Dai, C.S. Huang, M.Q. Huang and H.Y. Jin. |

1/Nc Expansion of the Heavy Baryon Isgur-Wise Functions

Chun LiuSubjects: Physics >> The Physics of Elementary Particles and Fields

The 1/Nc expansion of the heavy baryon Isgur-Wise functions is discussed.Because of the contracted SU(2Nf ) light quark spin-flavor symmetry, the universality relations among the Isgur-Wise functions of b ! #3;c and #6;(?) b ! #6;(?)c are valid up to the order of 1/N2 c . |

Some Remarks on the Baryon-Meson Couplings in the 1/Nc Expansion

Chun LiuSubjects: Physics >> The Physics of Elementary Particles and Fields

The original results for the baryon-pion couplings in the large Nc QCD can be understood in a simpler way in the Hartree-Fock picture. The large Nc relation and its 1/Nc correction between the heavy baryon- meson coupling and the light baryon-meson coupling are emphasized.Application to the baryon-ρ meson interactions is straightforward. The implications of recent experimental result for the strong coupling con-stants of the heavy baryon chiral lagrangian are discussed. |

Decay Widths of Excited Heavy Mesons From QCD Sum Rules at the Leading Order of HQET

Yuan-Ben Dai; Chao-Shang Huang; Ming-Qiu Huang; Hong-Ying Jin; Chun LiuSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The widths for pionic decays of lowest two excited doublets (0+, 1+) and(1+, 2+) of heavy mesons are studied with QCD sum rules in the leading order of heavy quark effective theory. The ambiguity due to presence of two distinct 1+ states are solved. The soft pion approximation is not used. |