118479937
Comment on `A collider signature of the supersymmetric golden region'
We show that Z polarization measurement is useful for distinguishing the signal decay chain of the `golden region' [1] in the minimal supersymmetric standard model (MSSM) parameter space, which involves the stop decay of 2 → 1+Z, from other decay chains involving the neutralino decay of 20 → 10+Z in different MSSM scenarios. Within a given decay chain, Z polarization can also serve as an indicator of the mass difference of stops or neutralinos.
119291756
Gluino Stransverse Mass
We introduce a new observable, ’gluino stransverse mass’, which is an application of the Cambridge mT2 variable to the process where gluinos are pair produced in proton-proton collision and each gluino subsequently decays into two quarks and one LSP, i.e. g̃g̃ → qqχ̃01 qqχ̃ 0 1. We show that the gluino stransverse mass can be utilized to measure the gluino mass and the lightest neutralino mass separately, and also the 1st and 2nd generation squark masses if squarks are lighter than gluino, thereby providing a good first look at the pattern of sparticle masses experimentally.
119289779
M(T2)-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC
We propose a scheme to assign a 4-momentum to each WIMP in new physics event producing a pair of mother particles each of which decays to an invisible weakly interacting massive particle (WIMP) plus some visible particle(s). The transverse components are given by the value that determines the event variable M{sub T2}, while the longitudinal component is determined by the on-shell condition on the mother particle. Although it does not give the true WIMP momentum in general, this M{sub T2}-assisted on-shell reconstruction of missing momenta provides kinematic variables well correlated to the true WIMP momentum and thus can be useful for an experimental determination of new particle properties. We apply this scheme to some processes to measure the mother particle spin and find that spin determination is possible even without good knowledge of the new particle masses.
18430798
Measuring the top quark mass with m_T2 at the LHC
We investigate the possibility to measure the top quark mass using the collider variable $m_{T2}$ at the LHC experiment. Monte Carlo studies of $m_{T2}$ are performed with the events corresponding to the dilepton decays of $t\bar{t}$ produced at the LHC with 10 $fb^{-1}$ integrated luminosity. Our analysis suggests that the top quark mass can be determined by the $m_{T2}$ variable alone with a good precision at the level of 1 GeV.
119962841
Photoelectron angular distributions from the subshells of high-Z elements
Numerical predictions are obtained, within a relativistic multipole central-field approximation calculation, for the radial matrix elements and resulting angular distributions of photoelectrons ejected from inner through outer subshells of uranium and for photoelectron energies from near threshold (1 eV) to 100 keV. Some data are also presented for outer subshells of mercury. We confirm that for inner shells higher-multipole effects persist to low energies, while we find that for outer shells such effects become small. For uranium inner ns subshells the asymmetry parameter ..beta../sub n/s differs from its nonrelativistic value 2, but not more than 30% (for n .. epsilonp/sub 1/2/ and ns ..-->.. epsilonp/sub 3/2/ transitions for these inner shells are similar). For outer s subshells relativistic spin-orbit splittings cause large deviations from the nonrelativistic predictions which can be understood from the magnitudes, zeros, and splittings of the two radial matrix elements. For U 6p/sub 1/2/ and 6p/sub 3/2/, ..beta../sub 6p/ has the same qualitative features found in nonrelativistic calculations for outer p shells of other high-Z elements, but the angular distributions from the two states do differ in detail. Such differences in angular distributions of themore » photoelectrons from the two j substates of given l become smaller for inner p shells. For outer d and f subshells the asymmetry parameter oscillates with photoelectron energy in a manner similar to that found by Manson in nonrelativistic dipole d-subshell calculations, and no qualitatively important relativistic effects have been identified; this is due to the decrease of the fine-structure-splitting interval with increasing angular momentum.« less
117941616
Lorentz Group derivable from Polarization Optics 1
The Lorentz group is the fundamental language for space-time symmetries of relativistic particles. This group can these days be derived from the symmetries observed in other branches of physics. It is shown that this group can be derived from optical filters. The group O(2,1) is appropriate for attenuation filters, while the O(3) group describes phase-shift filters. The combined operation leads to a two-by-two representation of the six-parameter Lorentz group. It is shown also that the bilinear representation of this group is the natural language for the polarization optics. The Lorentz group serves useful purposes in many branches of physics. In this note, we would like to show that the bilinear representation of the six-parameter Lorentz group [1] is the natural language for polarization of light waves. In studying polarized light propagating along the z direction, the traditional approach is to consider the x and y components of the electric fields. Their amplitude ratio and the phase difference determine the degree of polarization. Thus, we can change the polarization either by adjusting the amplitudes, by changing the relative phase shift, or both. For convenience, we call the optical device which changes amplitudes an “attenuator,” and the device which changes the relative phase a “phase shifter.” Let us write the electric field vector as
17252988
Symmetries of the Poincare sphere and decoherence matrices
The Stokes parameters form a Minkowskian four-vector under various optical transformations. As a consequence, the resulting two-by-two density matrix constitutes a representation of the Lorentz group. The associated Poincare sphere is a geometric representation of the Lorentz group. Since the Lorentz group preserves the determinant of the density matrix, it cannot accommodate the decoherence process through the decaying off-diagonal elements of the density matrix, which yields to an incerese in the value of the determinant. It is noted that the O(3,2) deSitter group contains two Lorentz subgroups. The change in the determinant in one Lorentz group can be compensated by the other. It is thus possible to describe the decoherence process as a symmetry transformation in the O(3,2) space. It is shown also that these two coupled Lorentz groups can serve as a concrete example of Feynman's rest of the universe.
122028207
Covariant harmonic oscillators and excited meson decays
We use the covariant harmonic-oscillator wave functions to formulate the vacuum quark-pair-creation model of three-meson vertices and meson-decay matrix elements. It is pointed out first that the harmonic-oscillator wave functions can be given a covariant probability interpretation. We then use this probability concept to construct the three-meson vertex function. Using a relativistic L-S coupling scheme, we calculate the decay amplitudes for the B $Yields$ $omega$$pi$ and A$sub 1$ $Yields$ rho$pi$ decays. For the B decay, the calculated polarization ratio turns out be in excellent agreement with the experimental value. For the A$sub 1$ decay, the calculated ratio is consistent with the present experimental value. We have also calculated the decay ratio for the well-established rho $Yields$ $pi$$pi$ and A$sub 2$ $Yields$ rho$pi$ decays. It is shown that the harmonic-oscillator wave functions produce a number which is very close to the experimental value. The limitations of the L-S coupling scheme are discussed.
121787679
GAUGE TRANSFORMATIONS AS LORENTZ BOOSTED ROTATIONS
Abstract The E(2)-like little group for massless particle is obtained from the O(3)-like little group for massive particles in the infinite-momentum/zero-mass limit. It is shown therefore that rotations around the axes perpendicular to the direction of the momentum become gauge transformations in this limit. The limiting procedure is shown to be identical to that of group contraction through which O(3) becomes E(2).