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: 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: 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 >> 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 >> 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 >> 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 >> 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: A supersymmetric model with gauge symmetry G1 × G2, where Gi = SU(3)i × SU(2)i × U(1)i, is constructed within the framework of gauge me-diated supersymmetry breaking. At the energy scale ∼ (10−100) TeV wherem the gauge symmetry breaks down to the Standard Model (SM), G1 is strong and G2 is weak. The observed gauge coupling constant unification of the SM is attributed to that of G2. The messenger fields and Higgs fields just sat-isfy the condition that makes G2 a realization of strong unification. The SMgauginos are predicted to be generally heavier than the sleptons and squarks.
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: If the tau neutrino is as heavy as 10 MeV which may have certain astrophysical implications, the neutrino mass pattern is studied so as to accommodate the new oscillation observations. It predicts that the electron neutrino has Marjorana mass around 0.05 eV. A supersymmetric model is described to realize the above scenario.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: An understanding of the lepton masses within the framework of SUSY is presented.A family symmetry is introduced. Sneutrino VEV breaks this symmetry. The tau mass is due to the Higgs VEV, and muon mass purely from the sneutrino VEV. A viable model is constructed, which predicts (1 − 10) MeV #23;#28; .
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: Within the framework of supersymmetry, the particle content is extended in a way that eachHiggs doublet is in a full generation. Namely in addition to ordinary three generations, there is an extra vector-like generation, and it is the extra slepton SU(2)L doublets that are taken to be the two Higgs doublets. R-parity violating interactions contain ordinary Yukawa interactions.Breaking of supersymmetry and gauge symmetry are analyzed. Fermion and boson spectra arecalculated. Phenomenological constraints and relevant new physics at Large Hadron Collider arediscussed.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-09-17
摘要: From the large-Nc QCD point of view, baryonia, tetra-quark states, hybrids, and glueballs arestudied. The existence of these states is argued for. They are constructed from baryons. In Nf = 1,large Nc QCD, a baryonium is always identical to a glueball with Nc valence gluons. The groundstate 0−+ glueball has a mass about 2450 MeV. f0(1710) is identified as the lowest 0++ glueball.The lowest four-quark nonet should be f0(1370), a0(1450), K∗0 (1430) and f0(1500). Combiningwith the heavy quark effective theory, spectra of heavy baryonia and heavy tetra-quark states arepredicted. 1/Nc corrections 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: The three active light neutrinos are used to explain the neutrino oscillations.The inherently bi-large mixing neutrino mass matrix and the Fritzsch type,bi-small mixing charged lepton mass matrix are assumed. By requiring the maximal #23;μ −#23;#28; mixing for the atmospheric neutrino problem and the mass-squared difference approperiate for the almost maximal mixing solution to the solar neutrino problem, the following quantities are predicted: the #23;e−#23;μ mixing, Ve3, CP violation in neutrino oscillations, and the effective electron-neutrino mass relevant to neutrinoless double beta decays.
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 muon- and tau-neutrinos with the mass in the keV range, which are allowed in a low reheating temperature cosmology, can compose the warm dark matter of the universe. A model of four light neutrinos including the keV scale #23;μ and #23;#28; is studied, which combines the seesaw mechanism and the Abelian flavor symmetry. The atmospheric neutrino anomaly is due to the #23;μ − oscillation. The solar neutrino problem is answered by the oscillation into the light sterile neutrino, where the SMA, LMA, and LOW-QVO solutions can be accommodated in our scenario.
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: Three light sterile neutrinos (#23;se , #23;sμ and #23;s) are introduced to accommodate all the available neutrino data: the atmospheric neutrino anomaly is explained by #23;μ − #23;sμ oscillation with maximal mixing; the solar one is due to #23;e − #23;se oscillation of small angle Mikheyev-Smirnov-Wolfenstein type; the Liquid Scintillation Neutrino Detector data is from #23;e − #23;μ oscillations, so that the neutrinos can be the hot component of the dark matter. The big bang nucleosynthesis constraint is satisfied by taking the tau neutrino to be 10 MeV heavy. The #23;#28; decay is discussed in a model of gauge mediated supersymmetry breaking. The decay mode #23;#28; → ˜G with ˜G being the gravitino is proposed. The #23;#28; has a rather long lifetime ∼ 103 − 1013 sec. Its implication to the Gamma-ray Burst is discussed.