分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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).
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: 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 .
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: 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.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: We argue that in the large Nc HQET, the masses of the s-wave lowspin heavy baryons equal to the heavy quark mass plus proton mass approximately. To the subleading order, the heavy baryon mass 1/Nc expansion not only has the same form, but also has the same coefficients as that of the light baryon. Based on this, numerical analysis is made.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: The m asses of excited heavy m esons are studied with sum rules in the heavy quark e#11;ective theory.A setofinterpolating currentscreating (annihilating) excited heavy m esonswith arbitrary spin and parity are proposed and their propertiesarediscussed.Num ericalresultsattheleading orderofthe O (1=m Q ) expansion are obtained for the lowest doublets (0+ ;1+ ) and(1+ ;2+ ).
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: Some phenomenological aspects of a supersymmetric model for fermion mass hierarchy proposed previously are discussed. It is required that the lepton universality violation is near to its current experimental bound. The lepton number violation decay modes τ → 2eμ and 3μ maybe observable in the near future. The Majorana mass of electron-neutrino is predicted to be about 0.1 eV. The fine-tuning problem is discussed.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: The 1/mc and 1/mb corrections to the #3;b → #3;c semileptonic decay are analyzed by QCD sum rules. Within the framework of heavy quark effective theory, the subleading baryonic Isgur-Wise function of #3;b → #3;c has been calculated. It is shown that the corrections due to the 1/m Lagrangian insertion are negligibly small. The sizable 1/mQ effect to the decay lies only in the weak current. The decay spectrum and the branching ratio are given.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: The 1/m corrections to heavy baryon masses are calculated from the QCD sum rules within the framework of the heavy quark effective theory.Numerical results for the heavy baryons are obtained. The implications of the results are discussed.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: A pattern of quark mass hierarchy and CP violation within the framework of low energy supersymmetry is described. By assuming some discrete symmetry among the three families, the quarks of the third family obtain masses at tree level. The second family obtains masses radiatively at one-loop level due to the soft breaking of the family symmetry. At this level, the first family remains massless by some degeneracy conditions of the squarks. As a result of R-parity violation, the sneutrino vacuum expectation values are nonvanishing. CP violation occurs through the superweak sneutrino exchange. This picture is consistent with the experiments on the flavor changing neutral current.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: It is proposed that supersymmetry (SUSY) maybe used to understand fermion mass hierarchies.A family symmetry Z3L is introduced, which is the cyclic symmetry among the three generationSU(2) doublets. SUSY breaks at a high energy scale ∼ 1011 GeV. The electroweak energy scale∼ 100 GeV is unnaturally small. No additional global symmetry, like the R-parity, is imposed.The Yukawa couplings and R-parity violating couplings all take their natural values which are O(100 − 10−2). Under the family symmetry, only the third generation charged fermions get their masses. This family symmetry is broken in the soft SUSY breaking terms which result in a hierarchical pattern of the fermion masses. It turns out that for the charged leptons, the #28; mass is from the Higgs vacuum expectation value (VEV) and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs, and the electron gains its mass due to both Z3L and SUSY breaking.The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. |Ve3| which is for #23;e − #23;#28; mixing is expected to be about 0.1. For the quarks, the third generation masses are from the Higgs VEVs, the second generation masses are from quantum corrections, and the down quark mass due to the sneutrino VEVs. It explains mc/ms, ms/me,md > mu and so on. Other aspects of the model are discussed.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: Using the framework of the Heavy Quark Effective Theory we have re-analyzed the Isgur-Wise function describing semileptonic #3;b → #3;c decays in the QCD sum rule approach.The slope parameter of the Isgur-Wise function is found to be ρ2 = 1.35 ± 0.12, which isconsistent with an experimental measurement and a lattice calculation. To O(1/mb, 1/mc)of the heavy quark expansion the integrated #3;b decay width is used to extract the CKM matrix element Vcb for which we obtain a value of |Vcb| = 0.041±0.004 in excellent agreementwith the value of |Vcb| determined from semileptonic B → D∗ decays.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: If supersymmetry (SUSY) is not for stabilizing the electroweak energy scale, what is it used for in particle physics? We propose that it is for flavor problems. A cyclic family symmetry is introduced. Under the family symmetry, only the #28; -lepton is massive due to the vacuum expectation value (VEV) of the Higgs field. This symmetry is broken by a sneutrino VEV which results in the muon mass. The comparatively large sneutrino VEV does not result in a large neutrino mass due to requiring heavy gauginos. SUSY breaks at a high scale ∼ 1013 GeV. The electroweak energy scale is unnaturally small. No additional global symmetry, like the R-parity, is imposed. Other aspects of the model are discussed.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-17
摘要: We analyze various possible interpretations of the narrow state D+sJ (2632) observed by SELEX Collaboration recently, which lies above threshold and has abnormal decay pattern. These interpretations include: (1) several versions of tetraquarks; (2) conventional cs¯ meson such as the first radial excitation of Ds(2112) with abnormally large SU(3) symmetry breaking; (3) conventional cs¯ meson with abnormally large η1 coupling; (4) heavy hybrid meson. We discuss the physical implications of each interpretation. For example, if the existence of D +sJ (2632) is confirmed as the first radial excitation of Ds(2112) by other experiments, it will be helpful to look for (1) its SU(3) flavor partners D 0,+J(2530); (2) its B-meson analogues B0,+J(5840), B+sJ (5940); (3) S-wave two pion decaymodes.