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Charles A. Nelson

Publications and source records attributed to Charles A. Nelson.

32 records · Page 2Linked to original sources
arXiv2000

Testing for New Couplings in Top Quark Decay

Tests of the Lorentz structure of t --> W b decay will be carried out at the Tevatron, and later at the LHC and at a NLC. To quantitatively assay future measurements of competing observables, we consider the (V-A) coupling values of the helicity decay parameters versus "(V-A) + Single Additional Lorentz Structures". Three phase-type ambiguities exist, but measurement of the sign of the large interference between the W boson longitudinal/transverse amplitudes could exclude the two due dynamically to additional (S+P) and (f_M + f_E) couplings. Sizable T-violation signatures can occur for low-effective mass scales, < 320 GeV, but in most cases can be more simply excluded by 10% precision measurement of the probabilities P(W_L) and P(b_L). Signatures for the presence of T-violation associated with the dynamical phase-type ambiguities, CP-violation signatures, and Lambda_b polarimetry are also discussed.

hep-ph↗
arXiv1998

Eigenstates of Paraparticle Creation Operators

Eigenstates of the parabose and parafermi creation operators are constructed. In the Dirac contour representation, the parabose eigenstates correspond to the dual vectors of the parabose coherent states. In order $p=2$, conserved-charge parabose creation operator eigenstates are also constructed. The contour forms of the associated resolutions of unity are obtained.

hep-th↗
arXiv1998

Dirac's Contour Representation for Paraparticles

Dirac's contour representation is extended to parabose and parafermi systems by use of deformed algebra techniques. In this analytic representation the action of the paraparticle annihilation operator is equivalent to a deformed differentiation which encodes the statistics of the paraparticle. In the parafermi case, the derivative's ket-domain is degree $p$ polynomials.

hep-th↗
arXiv1998

Measurement of Helicity Parameters in Top Quark Decay

The standard model(SM) predicts only a $g_{V-A}$ coupling in $t \to W^+ b$ decay. However, if additional Lorentz structures exist, they can manifest themselves in high energy processes such as this via non-SM values of the helicity parameters describing $t \to W^+ b$. Plots and tables of the values of these helicity parameters are obtained for various coupling strengths. Three phase-type ambiguities are uncovered: $g_{V-A} + g_{S+P}$ with effective-mass scale $Λ_{S+P} \sim -35 GeV, g_{V-A} + g_{f_M + f_E}$ with $Λ_{f_M + f_E} \sim 53 GeV$, and an arbitrary sign-flip in the $b_L$ amplitudes $A_{X} (λ_b = - 1/2) = - A_{V-A} (λ_b = - 1/2)$. These ambiguities are analyzed so that they might be partially resolved when experiments resume at the Fermilab Tevatron.

hep-ph↗
arXiv1997

General Tests for t ---> W+ b couplings at Hadron Colliders

The modularity property of the helicity formalism is used to provide amplitude expressions and stage-two spin-correlation functions which can easily be used in direct experimental searches for electro-weak symmetries and dynamics in the decay processes $t \to W^+ b$, $\bar t \to W^- \bar b$. The formalism is used to describe the decay sequences $t\to W^{+}b\to (l^{+}ν)b$, and $t\to W^{+}b\to (j_{\bar d}j_u)b$. Helicity amplitudes for $t \to W^+ b $ are obtained for the most general $J_{\bar b t}$ current. Thereby, the most general Lorentz-invariant decay-density-matrix for $t\to W^{+}b\to (l^{+}ν)b$, or for $t\to W^{+}b\to (j_{\bar d}j_u)b$, is expressed in terms of eight helicity parameters and, equivalently, in terms of the structures of the $J_{\bar b t}$ current. The parameters are physically defined in terms of partial-width-intensities for polarized-final-states in \newline $t\to W^{+}b$ decay. The full angular distribution for the reactions $q \bar q$ and $g g \to t \bar t \to (W^+ b) (W^- \bar b) \to ...$ can be used to measure these parameters. Since this adds on spin-correlation information from the next stage of decays in the decay sequence, such an energy-angular distribution is called a stage-two spin-correlation (S2SC) function.

hep-ph↗
arXiv1997

Importance of Tests for the Complete Lorentz Structure of the t --> W+ b vertex at Hadron Colliders

The most general Lorentz-invariant decay-density-matrix for $t\to W^{+}b\to (l^{+}ν)b$, or for $t\to W^{+}b\to (j_{\bar d}j_u)b$, is expressed in terms of eight helicity parameters. The parameters are physically defined in terms of partial-width-intensities for polarized-final-states in $t\to W^{+}b$ decay. The parameters are the partial width, the $b$ quark's chirality parameter $ξ$, the $W^+$ polarimetry parameter $σ$, a "pre-SSB" test parameter $ζ$, and four $W_{L}$-$W_{T}$ interference parameters $η$, $η^{'}$, $ω$, $ω^{'}$ which test for $\tilde T_{FS}$ violation. They can be used to test for non-CKM-type CP violation, anomalous $Γ_{L,T}$'s, top weak magnetism, weak electricity, and second-class currents. By stage-two spin-correlation techniques, percent level statistical uncertainites are typical for measurements at the Tevatron, and several mill level uncertainites are typical at the LHC.

hep-ph↗
arXiv1996

Testing CP, T and (V-A) Symmetry through Tau Leptons

Model independent tests for symmetry violations in tau decays are important for determining whether the tau lepton is elementary or, instead, macroscopic. Such tests are also significant steps towards resolving the outstanding "e - mu - tau" puzzle. This talk reviews such tests in the context of a general treatment of two-body tau decays which only assumes Lorentz invariance and the tree-like structure of the tau-antitau production-decay sequence. Direct measurement of polarized-partial-widths and of associated ``longitudinal-transverse W-exchange" interference intensities will provide significant probes for distinguishing elementary/macroscopic theories of the Higgs and of the tau, and tau-neutrino. The analogous goals and techniques apply to top quark decays.

hep-ph↗
arXiv1996

Tau Decays Beyond the Standard Model

In a recent paper, 8 semileptonic parameters were defined to specify the most general Lorentz-invariant spin correlation functions for 2-body tau decays. These parameters can be used to search for anomalous longitudinal-versus transverse polarized-partial widths, for non-CKM-type leptonic CP violation, and for leptonic T violation. They can also be used to bound the effective-mass scales ``Lambda" for new physics arising from additional Lorentz structures, e.g. from lepton compositeness, tau weak magnetism, weak electricity, or second-class currents. It is emphasized that (i) for these tests ``different modes have different merits" and that (ii) the parameters can be measured either by using spin-correlation techniques without polarized beams, or with longitudinally polarized beams.

hep-ph↗
arXiv1996

On the Two q-Analogue Logarithmic Functions

There is a simple, multi-sheet Riemann surface associated with e_q(z)'s inverse function ln_q(w) for 0< q < 1. A principal sheet for ln_q(w) can be defined. However, the topology of the Riemann surface for ln_q(w) changes each time "q" increases above the collision point of a pair of the turning points of e_q(x). There is also a power series representation for ln_q(1+w). An infinite-product representation for e_q(z) is used to obtain the ordinary natural logarithm ln{e_q(z)} and the values of sum rules for the zeros "z_i" of e_q(z). For |z|<|z_1|, e_q(z)=exp{b(z)} where b(z) is a simple, explicit power series in terms of values of these sum rules. The values of the sum rules for the q-trigonometric functions, sin_q(z) and cos_q(z), are q-deformations of the usual Bernoulli numbers.

q-alg↗
arXiv1996

Tests at a Tau/Charm Factory with Longitudinally Polarized Beams

In a recent paper, eight semileptonic parameters were defined to specify the most general Lorentz-invariant spin correlation functions for tau semileptonic decays. The parameters were physically defined in terms of tau-decay partial-width intensities for polarized final states. This paper studies how these parameters can be simply measured at a tau/charm factory with longitudinally polarized beams without using spin-correlation techniques. Thereby the parameters can also be used to bound the effective-mass scales $ Λ$ for ``new physics" such as arising from lepton compositeness, leptonic CP violation, leptonic T violation, tau weak magnetism, weak electricity, and/or second-class currents.

hep-ph↗
arXiv1995

A General Treatment of Tau Semi-Leptonic Decays

The most general Lorentz invariant spin-correlation functions for $τ^{-}\rightarrow ρ^{-}ν,a_1^{-}ν,K^{*-}ν, π^{-}ν,K^{-}ν$ are expressed in terms of eight semi-leptonic parameters. They are physically defined in terms of tau-decay partial-width-intensities for polarized-final-states. The parameters are also expressed in terms of a ``$(V-A)\ +\ $additional chiral coupling'' structure in the ${J^{Charged}}_{Lepton}$ current, so as to bound the scales $Λ$\ for ``new physics'' such as arising from leptonic CP violation, tau weak magnetism, weak electricity, and/or second-class currents. The two tests for leptonic CP violation in $τ\rightarrow ρν\ $ decay are generalized to $τ\rightarrow a_1ν\ $ decay and to two additional tests if there are $ν_R\ $ and $\bar ν_L\ $ couplings.

hep-ph↗
arXiv1994

Tests for Tau's Charged-Current Structure

The Lorentz structure of the tau lepton's charged-current can almost be completely determined by use of stage-two spin-correlation functions for the $\{ρ^{-},ρ^{+}\}$ and $\{a_1^{-},a_1^{+}\}$ decay modes It is possible to test for a ``(V-A) + something'' structure in the ${J^{Charged}}_{Lepton}$ current, so as to bound the scales $Λ$ for ``new physics" such as arising from tau weak magnetism, weak electricity, and/or second-class currents.

hep-ph↗
arXiv1994

Tau as a Probe for New Physics

The usage of polarimetry and spin-correlation tests to determine the {\em complete Lorentz structure} of the tau lepton's charged and neutral-current couplings is reviewed. The emphasis is on tests for ``something'' in a $(V-A) + $ ``something'' structure in ${J^{Charged}}_{Lepton}$ current, so as to bound the scales $Λ$ for ``new physics" such as arising from tau weak magnetism, weak electricity, and/or second-class currents. Tests for $T$ and for $CP$ violation are discussed.

hep-ph↗