119042719
A supersymmetry model of leptons
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 tau-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 similar to 10(13) 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. (C) 2005 Published by Elsevier B.V.
118790054
Phenomenological aspects of R-parity violating supersymmetry with a vectorlike extra generation
Phenomenological analysis to the R-parity violating supersymmetry with a vectorlike extra generation is performed in detail. It is found that, via the trilinear couplings, the correct neutrino spectrum can be obtained. The Higgs mass rises to 125 GeV by new up-type Yukawa couplings of vectorlike quarks with no need of very heavy superpartners. Phenomena of new heavy fermions at LHC are predicted. DOI: 10.1103/PhysRevD.87.075012
14586429
QCD sum rule analysis for the Lambda(b)->Lambda(c) semileptonic decay
Abstract The 1 m c and 1 m b corrections to the Λ b → Λ c semileptonic decay are analyzed by QCD sum rules. Within the framework of heavy quark effective theory, the subleading baryonic Isgur-Wise function of Λ b → Λ c has been calculated. It is shown that the corrections due to the 1 m Lagrangian insertion are negligibly small. The sizable 1 m Q effect to the decay lies only in the weak current. The decay spectrum and the branching ratio are given.
119384069
Supersymmetry for Fermion Masses
It is proposed that supersymmetry (SUSY) maybe used to understand fermion mass hierarchies. A family symmetry Z_{3L} is introduced, which is the cyclic symmetry among the three generation SU(2) doublets. SUSY breaks at a high energy scale ~ 10^{11} 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 about (10^0-10^{-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 tau 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 Z_{3L} and SUSY breaking. The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. |V_{e3}| which is for nu_e-nu_{tau} 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 m_c/m_s, m_s/m_e, m_d>m_u and so on. Other aspects of the model are discussed.
117463737
A Supersymmetric model with the gauge symmetry SU(3)(1) x SU(2)(1) x U(1)(1) x SU(3)(2) x SU(2)(2) x U(1)(2)
A supersymmetric model with two copies of the Standard Model gauge groups is constructed in the gauge mediated supersymmetry breaking scenario. The supersymmetry breaking messengers axe in a simple form. The Standard Model is obtained after first step gauge symmetry breaking. In the case of one copy of the gauge interactions being strong, a scenario of electroweak symmetry breaking is discussed, and the gauginos are generally predicted to be heavier than the sfermions.
119216988
LHCb $\bigtriangleup A_{CP}$ of $D$ Meson and R-Parity Violation
LHCb collaboration has recently announced a measurement of the difference of time-integrated CP asymmetries between $D\rightarrow K^+K^-$ and $D \rightarrow \pi^+\pi^-$. This result provides the evidence of large direct CP violation in $D$ meson and reveals some important implications on underlying new physics. It is shown that the direct CP violation in $D$ meson can be enhanced by R-parity violating supersymmetry, while CP violations in $K$ and $B$ mesons are suppressed by this new physics, which is in consistence with previous experiments. Constraints on the model parameters and some consequences are also discussed.
121293716
Symmetry Breaking in Finite Volume
Spontaneous symmetry breaking is a cooperative phenomenon for systems with infinitely many degrees of freedom and it plays an essential role in quantum field theories. Lattice O(N) model is studied within the Hamiltonian approach using an adiabatic approximation. It is shown that the low-lying spectrum of the system in the broken phase can be understood by using the adiabatic, or Born-Oppenheimer approximation, which turns out to become an expansion in the inverse power of volume. In the infinite volume limit, the symmetry is broken while in the finite volume the slow rotation of the zero-momentum mode restores the symmetry and gives rise to the rotator spectrum, which has been observed in realistic Monte Carlo simulations.
123899809
Recent results from lattice QCD
Recent lattice QCD results are reviewed with an emphasis on spectroscopic results concerning the charm quark. It is demonstrated that, with accurate computations from lattice QCD in recent years that can be compared with the existing or upcoming experiments, stringent test of the Standard Model can be performed which will greatly sharpen our knowledge on the strong interaction.
118639447
Pure gauge glueballs at finite temperature
Pure gauge glueballs at finite temperature are investigated in a large temperature range from 0:3Tc to 1:9Tc on anisotropic lattices. Optimized glueball operators are used to obtain better signals. It is found in all 20 symmetry channels that the pole masses MG of glueballs remain almost constants when the temperature approaches the critical temperature Tc from below, and start to reduce gradually with the temperature going above Tc. The glueball correlators in 0 ++ , 0 i+ , and 2 ++ channels, are also analyzed based on the Breit-Wigner ansatz by assuming a thermal width Γ to the pole mass ω0. While ω0's are insensitive to T in the whole temperature range, Γ's exhibit distinct behavior below and above Tc: They are only few percents of ω0 when T Tc and reach values of roughly Γ » ω0=2 at T … 1:9Tc.
119253117
SPACETIME NONCOMMUTATIVE EFFECT ON BLACK HOLE AS PARTICLE ACCELERATORS
We study the spacetime noncommutative effect on black hole as particle accelerators and, find that the particles falling from infinity with zero velocity cannot collide with unbound energy, either near the horizon or on the prograde ISCO when the noncommutative Kerr black hole is exactly extremal. Our results also show that the bigger of the spinning black hole's mass is the higher of center of mass energy that the particles obtain. For small and medium noncommutative Schwarzschild black hole, the collision energy depends on the black hole's mass.
118586717
Generalized Lüscher formula in multichannel baryon-meson scattering
L\"uscher's formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center of mass frame. In this paper, we consider the case for the scattering of a spin 1/2 particle with a spinless particle in multi-channel scattering. A generalized relation between the energy of two particle system and the scattering matrix elements is established. We first obtain this relation using quantum-mechanics in both center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory using methods outlined in Ref. \cite{Hansen:2012tf}. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size.