Degenerate Doublet Research Articles

The weak sensitivity of acoustic resonance frequencies to temperature gradients

We determined the mass of argon gas contained within an un-thermostatted, commercially-manufactured 300 L pressure vessel (tank) with an uncertainty of 0.16 % at 0.6 MPa by combining measurements of the argon pressure, the frequencies of microwave and acoustic resonances within the tank, and an equation of state for argon. After correction for the thermoacoustic boundary layer and for the tank’s center-of-mass motion, the measured acoustic resonance frequencies f ac determined the average speed of sound, and therefore the average temperature, of the argon in the tank. We show that, consistent with first-order perturbation theory, f ac for the 3 lowest-frequency longitudinal gas modes gave the correct average temperature even when we imposed a 13 K temperature difference ΔT across the tank’s diameter. However for the nearly degenerate doublet modes, we observed a linear dependence on ΔT for f ac, which the theory does not predict. Using the thermal expansion deduced from the microwave measurements, we show that the linear dependence on ΔT was consistent with anisotropic changes in the tank’s shape in response to the applied temperature gradient. We will discuss the predictions from perturbation theory of the changes in f ac due to temperature gradients in cylindrical and spherical cavities. From these results, we argue that resonance frequencies can be used to “weigh” a compressed gas in much larger tanks in un-thermostatted environments and at high pressures.

Generalized tensor interaction and relativistic spin and pseudospin symmetries with the Manning-Rosen potential

We have investigated the Manning-Rosen potential under the framework of spin and pseudospin symmetries with generalized tensor interaction (GTI) using the parametric generalization of Nikiforov-Uvarovmethod. We have obtained the energy eigenvalues and the corresponding eigenfunction. We have also reported some numerical results and figures to show the effect of tensor interaction. The role of GTI is investigated in details. It is seen that the degenerate doublets in spin and pseudospin are changed due to the presence of GTI.

Nonlocal spectroscopy of Andreev bound states

We experimentally investigate Andreev bound states (ABSs) in a carbon nanotube quantum dot (QD) connected to a superconducting Nb lead (S). A weakly coupled normal metal contact acts as a tunnel probe that measures the energy dispersion of the ABSs. Moreover, we study the response of the ABS to nonlocal transport processes, namely, Cooper pair splitting and elastic co-tunnelling, which are enabled by a second QD fabricated on the same nanotube on the opposite side of S. We find an appreciable nonlocal conductance with a rich structure, including a sign reversal at the ground-state transition from the ABS singlet to a degenerate magnetic doublet. We describe our device by a simple rate equation model that captures the key features of our observations and demonstrates that the sign of the nonlocal conductance is a measure for the charge distribution of the ABS, given by the respective Bogoliubov-de Gennes amplitudes $u$ and $v$.

4D, $ \mathcal{N} $ = 1 supergravity genomics

The off-shell representation theory of 4D, $\mathcal{N}=1$ supermultiplets can be categorized in terms of distinct irreducible graphical representations called adinkras as part of a larger effort we call supersymmetry `genomics.' Recent evidence has emerged pointing to the existence of three such fundamental adinkras associated with distinct equivalence classes of a Coxeter group. A partial description of these adinkras is given in terms of two types, termed cis-and trans-adinkras (the latter being a degenerate doublet) in analogy to cis/trans isomers in chemistry. Through a new and simple procedure that uses adinkras, we find the irreducible off-shell adinkra representations of 4D, $\mathcal{N}=1$ supergravity, in the old-minimal, non-minimal, and conformal formulations. This procedure uncovers what appears to be a selection rule useful to reverse engineer adinkras to higher dimensions. We categorize the supergravity representations in terms of the number of cis-($n_c$) and trans-($n_t$) adinkras in the representation and synthesize our new results with our previous supersymmetry genomics results into a group theoretic framework.

Risk of misinterpreting nearly degenerate doublet bands as chiral partners in odd-even103,105,107Ag and odd-odd106Ag

Risk of misinterpreting nearly degenerate doublet bands as chiral partners in odd-even<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mrow><mml:mn>103</mml:mn><mml:mo>,</mml:mo><mml:mn>105</mml:mn><mml:mo>,</mml:mo><mml:mn>107</mml:mn></mml:mrow></mml:msup></mml:math>Ag and odd-odd<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>106</mml:mn></mml:msup></mml:math>Ag

Possible multiple chiral doublet bands in107Ag

Two pairs of nearly degenerate doublet bands in ${}^{107}$Ag are studied via the relativistic mean-field (RMF) theory and the multiparticle plus rotor model (PRM), which suggests these bands as two distinct sets of chiral doublet bands. For the suggested $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}1}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}^{2}$ and $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}1}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}{d}_{5/2}$ configurations, the favorable triaxial deformation $\ensuremath{\gamma}$ for nuclear chirality can be obtained from the configuration-fixed constrained triaxial RMF calculations. Adopting the PRM, the data available are reproduced very well for the two pairs of doublet bands. Chiral geometry is further conformed by analyzing the angular momentum components. We suggest that two pairs of doublet bands in ${}^{107}$Ag would be another example of multiple chiral doublet bands.

Tunneling spectroscopy of a single quantum dot coupled to a superconductor: From Kondo ridge to Andreev bound states

We performed tunneling spectroscopy of a carbon nanotube quantum dot (QD) coupled to a metallic reservoir either in the normal or in the superconducting state. We explore how the Kondo resonance, observed when the QD's occupancy is odd and the reservoir is normal, evolves towards Andreev bound states (ABS) in the superconducting state. Within this regime, the ABS spectrum observed is consistent with a quantum phase transition from a singlet to a degenerate magnetic doublet ground state, in quantitative agreement with a single-level Anderson model with superconducting leads.

Lepton Private Higgs and the discrete group [formula omitted

We use the discrete group Σ(81)≡(Z3×Z3×Z3)⋊Z3 to explore a particular region of parameter space in the Private Higgs model. In doing so we suggest a relation among the off-diagonal entries of the neutrino mass matrix and a possible explanation for the muon magnetic moment anomaly, aμexp−aμSM∼10−9. We predict three new nearly degenerate Higgs doublets with masses of order ∼500 GeV to ∼1 TeV, and three nearly degenerate SM-singlet TeV-scale neutrinos. The largest scale in the model is ∼10 TeV, so there is no severe hierarchy problem. Appendix A is devoted to the group theory of Σ(81).

Approximate relativistic bound states of a particle in Yukawa field with Coulomb tensor interaction

We obtain the approximate relativistic bound state of a spin- particle in the field of the Yukawa potential and a Coulomb-like tensor interaction with arbitrary spin–orbit coupling number κ under the spin and pseudospin (p-spin) symmetries. The asymptotic iteration method is used to obtain energy eigenvalues and the corresponding wave functions in their closed forms. Our numerical results show that the tensor interaction removes degeneracies between the spin and p-spin doublets and creates new degenerate doublets for various strengths of tensor coupling.

Energy of partial A-body problem for 9ΛBe and 10ΛΛBe

The energy of the degenerate doublet (3+/2, 5+/2) of 9ΛBe, treating it as a partial nine-body system in the Λαα cluster model, has been calculated in the variational Monte Carlo framework. A simplified treatment, with the central two-body Urbana type ΛN and the three-body dispersive and two-pion exchange ΛNN forces along with the central two- and three-body correlations, is found to be adequate in explaining the energy of observed γ-ray transition from the excited degenerate doublet to the ground state. This partial nine-body model of 9ΛBe has been extended for the case of partial ten-body problem 10ΛΛBe in the ΛΛ + αα model where nucleonic degrees of freedom of as are taken into consideration ignoring antisymmetrization between two αs. The central two-body ΛN and ΛΛ and the three-body dispersive and two-pion exchange ΛNN forces, constrained by the Λp scattering data and the observed ground state energies of 5ΛHe and 6ΛΛ, are employed. The product type trial wavefunction predicts binding energy for the ground state considerably less than for the event reported by Danysz et al but however, consistent with the value deduced assuming a γ-ray of 3.04 MeV must have escaped undetected in the decay of the product 9ΛBe* → 9ΛBe + γ of the emulsion event 10ΛΛBe → π− + p + 9ΛBe* and for the excited 2+ state closer to the value measured in the Demachi-Yanagi event. The results of the present work are consistent with the earlier three- and four-body cluster model approaches where as are assumed to be structureless entities.

Actual and general Manning–Rosen potentials under spin and pseudospin symmetries of the Dirac equation

The so-called general and actual Manning–Rosen potentials have been investigated under spin and pseudospin symmetries of the Dirac equation in a comparative study. By approximating the centrifugal term, we have reported the analytical solutions to the problem via supersymmetry quantum mechanics. Illustrative figures and tables are included to discuss the problem in detail. The role of a Coulomb tensor interaction is investigated too. We see that the degenerate doublets are the same in both cases.

Superradiance of the system comprised of two parallel resonant thin layers

A cavity-like regime of superradiance for a double-layer medium populated by atoms with the A-scheme of transitions is considered in a semiclassical approximation under the condition that the layers are arranged symmetrically with respect to initial characteristics of the field and atomic system populating the layers. An analytical law for the linear stage of the superradiance process is found that agrees well with numerical solution of the differential equations of the model under consideration for any initial conditions nearly up to the peak of the appropriate characteristic of the field intensity module. For the case of degenerate lower doublet, the resonant character of the dependence of the superradiance pulse time delay on the distance between the layers is studied.

The Higgs boson resonance width from a chiral Higgs–Yukawa model on the lattice

The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for quarks, leptons and the weak gauge bosons. We use a 4-dimensional Euclidean lattice formulation of the Higgs–Yukawa sector of the electroweak model to compute physical quantities in the path integral approach which is evaluated by means of Monte Carlo simulations thus allowing for fully non-perturbative calculations. The chiral symmetry of the model is incorporated by using the Neuberger overlap Dirac operator. The here considered Higgs–Yukawa model does not involve the weak gauge bosons and furthermore, only a degenerate doublet of top- and bottom quarks are incorporated. The goal of this work is to study the resonance properties of the Higgs boson and its sensitivity to the strength of the quartic self-coupling.

Candidate chiral doublet bands in128La

The candidate chiral doublet bands in ${}^{128}$La have been searched for through the ${}^{118}$Sn(${}^{14}$N, 4n)${}^{128}$La reaction at a beam energy of 69 MeV. A positive-parity sideband with the same configuration as that of the yrast band has been identified. The positive-parity and spins of the sideband have been assigned based on the $\ensuremath{\Delta}I=1$ mixed $M1/E2$ and $E2$ characters of the linking transitions between the sideband and the yrast band. The properties of the sideband and the yrast band are discussed. The newly identified sideband and the yrast band are suggested to form the candidate of the near degenerate chiral doublet bands.

Transition between SU(4) and SU(2) Kondo effect

Motivated by experiments in nanoscopic systems, we study a generalized Anderson, which consist of two spin degenerate doublets hybridized to a singlet by the promotion of an electron to two conduction bands, as a function of the energy separation δ between both doublets. For δ=0 or very large, the model is equivalent to a one-level SU(N) Anderson model, with N=4 and 2 respectively. We study the evolution of the spectral density for both doublets (ρ1σ(ω) and ρ2σ(ω)) and their width in the Kondo limit as δ is varied, using the non-crossing approximation (NCA). As δ increases, the peak at the Fermi energy in the spectral density (Kondo peak) splits and the density of the doublet of higher energy ρ2σ(ω) shifts above the Ferrmi energy. The Kondo temperature TK (determined by the half-width at half maximum of the Kondo peak in density of the doublet of lower energy ρ1σ(ω)) decreases dramatically. The variation of TK with δ is reproduced by a simple variational calculation.

Structural change of the unique-parityπh11/2⊗νh11/2configuration in134Cs

A bandlike structure, based on the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configuration, has been identified for the first time in ${}^{134}$Cs in a gamma-ray spectroscopic study using fusion evaporation reactions. The nature of this band in ${}^{134}$Cs has been found to be distinctly different than the nearly degenerate doublet rotational band structures, observed in the lighter Cs isotopes for the same configuration. Both the total Routhian surface and the tilted axis cranking calculations were performed to understand the experimental observations. The present results suggest that the $N=77$ defines the border of the deformed structure in the $A\ensuremath{\sim}130$ region while approaching $N=82$.

Top Quark Asymmetry andWjjExcess at CDF from Gauged Flavor Symmetry

We show that the scalar sector needed for fermion mass generation when the flavor symmetry of the standard model is maximally gauged can consistently explain two anomalies reported recently by the CDF Collaboration-the forward-backward asymmetry in tt pair production and the dijet invariant mass in the Wjj channel. A pair of nearly degenerate scalar doublets with masses in the range 150-200 GeV explain these anomalies, with additional scalars predicted in the mass range 100-400 GeV. Consistency of such low scale flavor physics with flavor-changing processes is shown, and expectations for the LHC are outlined.

Searches for thet′of a fourth family

We study the detection of the ${t}^{\ensuremath{'}}$ of a fourth family during the early running of LHC with 7 TeV collision energy and $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ integrated luminosity. By the use of a neural network we show that it is feasible to search for the ${t}^{\ensuremath{'}}$ even with a mass close to the unitarity upper bound, which is in the 500 to 600 GeV range. We also present results for the Tevatron with $10\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. In both cases the search for a fourth family quark doublet can be significantly enhanced if one incorporates the contribution that the ${b}^{\ensuremath{'}}$ can make to a ${t}^{\ensuremath{'}}$-like signal. Thus, the bound on the mass of a degenerate quark doublet should be stronger than the bounds obtained by treating ${t}^{\ensuremath{'}}$ and ${b}^{\ensuremath{'}}$ in isolation.

Twisted mass chiral perturbation theory for 2 + 1+ 1 quark flavours

We present results for the masses of pseudoscalar mesons in twisted mass lattice QCD with a degenerate doublet of u and d quarks and a non-degenerate doublet of s and c quarks in the framework of next-to-leading order chiral perturbation theory, including lattice effects up to \( \mathcal{O}\left( {{a^2}} \right) \). The masses depend on the two twist angles for the light and heavy sectors. For maximal twist in both sectors, \( \mathcal{O}(a) \)-improvement is explicitly exhibited. The mixing of flavour-neutral mesons is also discussed, and results in the literature for the case of degenerate s and c quarks are corrected.

Tunneling Spectroscopy of Andreev Energy Levels in a Quantum Dot Coupled to a Superconductor

The coupling of a quantum dot with a BCS-type superconducting reservoir results in an intriguing system where low energy physics is governed by the interplay of two distinct phases, singlet and doublet. In this Letter we show that the spectrum of Andreev energy levels, which capture the properties of the two phases, can be detected in transport measurements with a quantum dot strongly coupled to a superconducting lead and weakly coupled to a normal metal lead. We observe phase transitions between BCS singlet and degenerate magnetic doublet states when the quantum dot chemical potential is tuned with an electrostatic gate, in good qualitative agreement with numerical renormalization group calculations.