119635084
Effects of quantum deformation on the spin-1/2 Aharonov–Bohm problem
Abstract In this Letter we study the Aharonov–Bohm problem for a spin-1/2 particle in the quantum deformed framework generated by the κ -Poincare–Hopf algebra. We consider the nonrelativistic limit of the κ -deformed Dirac equation and use the spin-dependent term to impose an upper bound on the magnitude of the deformation parameter e . By using the self-adjoint extension approach, we examine the scattering and bound state scenarios. After obtaining the scattering phase shift and the S -matrix, the bound states energies are obtained by analyzing the pole structure of the latter. Using a recently developed general regularization prescription [Phys. Rev. D. 85 (2012) 041701(R)], the self-adjoint extension parameter is determined in terms of the physics of the problem. For last, we analyze the problem of helicity conservation.
119697349
On the spin- 1/2 Aharonov-Bohm problem in conical space: Bound states, scattering and helicity nonconservation
In this work the bound state and scattering problems for a spin-1/2 particle undergone to an Aharonov-Bohm potential in a conical space in the nonrelativistic limit are consider ed. The presence of a �-function singularity, which comes from the Zeeman spin interaction with the magnetic flux tube, is addressed by the self-adjoint extension method. One of the advantages of the present approach is the determination of the self-adjoint extension parameter in terms of physics of the problem. Expressions for the energy bound states, phase-shift and S matrix are determined in terms of the self-adjoint extension parameter, which is explicitly determined in terms of the parameters of the problem. The relation between the bound state and zero modes and the failure of helicity conservation in the scattering problem and its relation with the gyromagnetic ratio g are discussed. Also, as an application, we consider the spin-1/2 AharonovBohm problem in conical space plus a two-dimensional isotropic harmonic oscillator.
119322655
Finiteness of the noncommutative supersymmetric Maxwell-Chern-Simons theory
Within the superfield approach, we prove the absence of UV/IR mixing in the three-dimensional noncommutative supersymmetric Maxwell-Chern-Simons theory at any loop order and demonstrate its finiteness in one, three, and higher loop orders.
118609457
Relativistic Landau-Aharonov-Casher quantization based on the Lorentz symmetry violation background
Based on the discussions about the Aharonov-Casher effect in the Lorentz symmetry violation background, we show that the analogue of the relativistic Landau quantization in the Aharonov-Casher setup can be achieved in the Lorentz-symmetry violation background.
118670238
He–McKellar–Wilkens effect and scalar Aharonov–Bohm effect for a neutral particle based on the Lorentz symmetry violation
In this contribution, we discuss the He–McKellar–Wilkens effect and the scalar Aharonov–Bohm effect for neutral particles based on the Lorentz symmetry violation background, by showing that the background of the Lorentz symmetry violation yields Abelian quantum phases for a neutral particle. We also study the non-relativistic bound states for a neutral particle interacting with a Coulomb-like potential based on the Lorentz symmetry violation background given by a fixed vector field parallel to the radial direction.
119686840
On Aharonov–Casher scattering in a CPT-odd Lorentz-violating background
The effects of a Lorentz symmetry-violating background vector on Aharonov?Casher scattering in the nonrelativistic limit are considered. Using the self-adjoint extension method, we find that there is additional scattering for any value of the self-adjoint extension parameter and non-zero energy bound states for negative values of this parameter. Expressions for the energy bound states, phase-shift and scattering matrix are explicitly determined in terms of the self-adjoint extension parameter. The expression obtained for the scattering amplitude reveals that the helicity is not conserved in this scenario.
122517251
An updated study of B meson oscillations using dilepton events
This paper reports a study of B meson oscillations using hadronic Z(0) decays with two identified leptons, and updates a previous publication by including data collected in 1994. Decay times are reconstructed for each of the semileptonic B decays by forming vertices which include the lepton and by estimating the B meson momentum. The mass difference, Delta m(d), between the two mass eigenstates in the B-d(0) system is measured to be 0.430 +/- 0.043 (+0.028)(-0.030) ps(-1), where the first error is statistical and the second error is systematic. For the B-s(0) system, a lower limit of Delta m(s) > 2.2 ps(-1) is obtained at 95% C.L.
40056432
A study of four-fermion final states with high multiplicity at LEP
Abstract A search for l + l − q q (l = e, μ) four-fermion final states in high multiplicity events has been performed at s ≈m Z and above the Z peak at s =130 GeV and s =136 GeV. The data taken with OPAL correspond to an integrated luminosity of 132.4 pb−1 and 5.3 pb−1 at s ≈m Z and s =130−136 GeV, respectively. While at the Z resonance the data are in good agreement with the Standard Model predictions, we find more events than expected at s =130−136 GeV, especially in the μ + μ − q q channel, where 5 events remain after all cuts, with only 0.6 predicted by the Monte Carlo simulation. For all center-of-mass energies the observed shapes of the differential distributions are consistent with the predictions.
124636093
Measurement of the average $b$ baryon lifetime and the product branching ratio f ($b \to Lambda_b$ ) x BR (Lambda($b$) $\to \Lambda \ell^-$ anti-neutrino $X^{)}$
121606064
Search for scalar top and scalar bottom quarks using the OPAL detector at LEP
The scalar top quark can be the lightest charged supersymmetric particle and it can be lighter than the top quark itself in supersymmetric extensions of the Standard Model. A search for a scalar top quark has been performed using a total data sample of 15.2 pb−1 at centre-of-mass energies of √s = 130, 136, and 161 GeV collected with the OPAL detector at LEP. No evidence was found above the background level expected from the Standard Model. The 95% C.L. lower limit on the scalar top quark mass is 58.7 GeV, if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is smaller than π4. If the mixing angle is zero, the limit is 65.4 GeV. These limits were obtained on the condition that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. Assuming a relatively light scalar neutrino, we also studied the complementary decay mode of the scalar top quark in which it decays into a bottom quark, a charged lepton, and a scalar neutrino. A mass limit on the light scalar bottom quark was also set in this study.
111345427
The Assembly of the Silicon Tracker of the Beam Test Engineering Model of the GLAST Large Area Telescope
The silicon tracker for the engineering model of the GLAST Large Area Telescope(LAT) to date represents the largest surface of silicon microstrip detectors assembled in a tracker (2.7 m{sup 2}). It demonstrates the feasibility of employing this technology for satellite based experiments, in which large effective areas and high reliability are required. This note gives an overview of the assembly of this silicon tracker and discusses in detail studies performed to track quality assurance: leakage current, mechanical alignment and production yields.