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: L = 1 excited heavy baryon masses are analyzed by heavy quark and large Nc expansions. In heavy quark limit, mass is parameterized by � and it is expanded further by spin-flavor breaking operators to the zeroth order of 1/Nc. Expanding coefficients will be fixed by more data on the excited baryons in the near future.
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 #3;b → #3;c semileptonic decay is analyzed in the framework of heavy quark effective theory to the order of 1/mc and 1/mb. The QCD sum rule and large Nc predictions to the decay form factors are applied. It argues that the subleading baryonic Isgur-Wise function in the large Nc limit vanishes.The decay rates, distributions and asymmetry parameters are calculated nu-merically. Some of the nonleptonic decay modes are discussed in the end.
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: At the order of 1/m3b , the B meson lifetimes are controlled by the hadronic matrix elements of some four-quark operators. The nonfactorizable magnitudes of these four-quark operator matrix elements are analyzed by QCD sum rules in the framework of heavy quark effective theory. The vacuum saturation for color-singlet four-quark operators is justified at hadronic scale, and the nonfactorizable effect is at a few percent level. However for color-octet four-quark operators, the vacuum saturation is violated sizably that the nonfactorizable effect cannot be neglected for the B meson lifetimes. The implication to the extraction of some of theparameters from B decays is discussed. The B meson lifetime ratio is predicted as τ (B−)/τ (B0) = 1.09 ± 0.02. However, the experimentalresult of the lifetime ratio τ (#3;b)/τ (B0) still cannot be explained.
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 >> 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 embed the flipped SU(5) models into the SO(10) models. After the SO(10) gauge symmetry is broken down to the flipped SU(5)譛(1)X gauge symmetry, we can split the five/one-plets and ten-plets in the spinor 16 and 16 Higgs fields via the stable sliding singlet mechanism. As in the flipped SU(5) models, these ten-plet Higgs fields can break the flipped SU(5) gauge symmetry down to the Standard Model gauge symmetry. The doublet-triplet splitting problem can be solved naturally by the missing partner mechanism, and the Higgsino-exchange mediated proton decay can be suppressed elegantly. Moreover, we show that there exists one pair of the light Higgs doublets for the electroweak gauge symmetry breaking. Because there exist two pairs of additional vector-like particles with similar intermediate-scale masses, the SU(5) and U(1)X gauge couplings can be unified at the GUT scale which is reasonably (about one or two orders) higher than the SU(2)L �SU(3)C unification scale. Furthermore, we briefly discuss the simplest SO(10) model with flipped SU(5) embedding, and point out that it can not work without fine-tuning.