Mixing Amplitude Research Articles

Isospin mode splitting and mixing in asymmetric nuclear matter

We estimate exclusive density and asymmetry parameter dependent dispersion relations of various charged states of pions in asymmetric nuclear matter. The possibility of matter induced mixing of {pi}{sup 0} with {eta} is clearly exposed with the further mass modification of {pi}{sup 0} meson due to mixing. Asymmetry driven mass splitting and mixing amplitude are of the same order as the corresponding values in vacuum. Closed form analytic results for the mass shifts and dispersion relations with and without mixing are presented. Furthermore, we discuss the sensitivity of our results on the scalar mean field within the framework of quantum hadrodynamics.

$D^0 \bar{D}^0$ Quantum Correlations, Mixing, and Strong Phases

Because of the quantum correlation between the pair-produced D0 and [Formula: see text] from the decay of the ψ(3770), the time-integrated single and double tag decay rates depend on charm mixing amplitudes, doubly-Cabibbo-suppressed amplitudes, and the relative strong phase δ between D0 and [Formula: see text] decays to identical final states. Using 281 pb-1 collected with the CLEO-c detector on the ψ(3770) resonance, we measure the absolute branching fractions of D0 decays to hadronic flavored states, CP eigenstates, and semileptonic final states to determine the relative strong phase cos δ and to limit the mixing amplitude y.

The unitarity triangle fit in the standard model and hadronic parameters from lattice QCD: a reappraisal after the measurements of ΔmsandBR(B→τντ)

The recent measurements of the B_s meson mixing amplitude by CDF and of the leptonic branching fraction BR(B to tau nu) by Belle call for an upgraded analysis of the Unitarity Triangle in the Standard Model. Besides improving the previous constraints on the parameters of the CKM matrix, these new measurements, combined with the recent determinations of the angles alpha, beta and gamma from non-leptonic decays, allow, in the Standard Model, a quite accurate extraction of the values of the hadronic matrix elements relevant for K-Kbar and B_{s,d}-B_{s,d}bar mixing and of the leptonic decay constant f_B. These values, obtained ``experimentally'', can then be compared with the theoretical predictions, mainly from lattice QCD. In this paper we upgrade the UT fit, we determine from the data the kaon B-parameter B_Khat, the B^0 mixing amplitude parameters f_Bs B^{1/2}_Bs and xi, the decay constant f_B, and make a comparison of the obtained values with lattice predictions. We also discuss the different determinations of V_ub and show that current data do not favour the value measured in inclusive decays.

Constraining the Phase ofBs−B¯sMixing

New physics contributions to B_s-\bar{B}_s mixing can be parametrized by the size (r_s^2) and the phase (2\theta_s) of the total mixing amplitude relative to the Standard Model amplitude. The phase has so far been unconstrained. We first use the D0 measurement of the semileptonic CP asymmetry A_SL to obtain the first constraint on the semileptonic CP asymmetry in B_s decays, A_SL^s=-0.008 \pm 0.011. Then we combine recent measurements by the CDF and D0 collaborations - the mass difference (\Delta M_s), the width difference (\Delta\Gamma_s) and A_SL^s - to constrain 2\theta_s. The errors on \Delta\Gamma_s and A_SL^s should still be reduced to have a sensitive probe of the phase, yet the central values are such that the regions around 2\theta_s ~ 3\pi/2 and, in particular, 2\theta_s ~ \pi/2, are disfavored.

Coherent nonlinear optical response of excitons and biexcitons in quantum dots coupled to phonons

AbstractFour wave mixing signals from single dots and dot ensembles involving excitonic and biexcitonic transitions are discussed. The results have been obtained analytically from a four level dot model coupled to longitudinal acoustic phonons. Time integrated four wave mixing amplitudes for quantum dot ensembles exhibit polarization dependent quantum beats that have already been found in experimental data. In four wave mixing signals of single quantum dots we find that the ground state to exciton transition has two contributions. One is identical to the known solution of the two level quantum dot model and leads to symmetric spectra for longer delay times, while the other comprises phase information from the biexciton and results in asymmetric spectra. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Time- and spectrally-resolved four-wave mixing in singleCdTe∕ZnTequantum dots

We present transient four-wave mixing experiments on individual excitonic transitions in self-assembled $\mathrm{Cd}\mathrm{Te}∕\mathrm{Zn}\mathrm{Te}$ quantum dots. Using a two-dimensional femtosecond spectroscopy and heterodyne detection of the nonlinear signal we study the dephasing and mutual coherent coupling of single quantum dot states. For the homogeneous linewidth of the zero-phonon line (ZPL) values of $0.06--0.1\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ $({T}_{2}=13--20\phantom{\rule{0.3em}{0ex}}\mathrm{ps})$ are measured, and a ZPL weight in the total line shape of $Z=0.9$ at $T=7\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is estimated. We observe two linearly polarized fine-structure split exciton transitions with transition dipole moment ratios of 1.0--1.1 deduced from the four-wave mixing (FWM) amplitude, and splitting energies of $0.2--0.35\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ deduced from the FWM spectral response or quantum beat period. Coherent coupling between excitonic states is identified by off-diagonal signals in the two-dimensional spectrally-resolved FWM. The presence of an inhomogeneous broadening caused by spectral diffusion in the time ensemble is evidenced by the formation of a photon echo in the time-resolved FWM from a single transition.

Decay out of the highly deformed band inNd133

The mean lifetimes of the ${25/2}^{+}$, ${21/2}^{+}$, and ${17/2}^{+}$ states in the highly deformed (HD) band of $^{133}\mathrm{Nd}$, excited via the reaction $^{104}\mathrm{Pd}$($^{32}\mathrm{S}$,2$\mathit{pn}$)$^{133}\mathrm{Nd}$, have been measured using a recoil distance Doppler-shift method. The decay out of the HD band occurs as a result of an admixture of normally deformed (ND) components into the HD states' wave function. The consistency in the mixing amplitude was assessed from the measured lifetimes, branching ratios, and quadrupole moments of the HD and the ND bands. This analysis unequivocally confirms the earlier approach to explain the decay-out mechanism.

The 2004 UTfit collaboration report on the status of the unitarity triangle in the standard model

Using the latest determinations of several theoretical and experimental parameters, we update the Unitarity Triangle analysis in the Standard Model. The basic experimental constraints come from the measurements of |V_ub/V_cb|, Delta M_d, the lower limit on Delta M_s, epsilon_k, and the measurement of the phase of the B_d - anti B_d mixing amplitude through the time-dependent CP asymmetry in B^0 to J/psi K^0 decays. In addition, we consider the direct determination of alpha, gamma, 2 beta + gamma and cos(2 beta) from the measurements of new CP-violating quantities, recently performed at the B factories. We also discuss the opportunities offered by improving the precision of the various physical quantities entering in the determination of the Unitarity Triangle parameters. The results and the plots presented in this paper can also be found at http://www.utfit.org, where they are continuously updated with the newest experimental and theoretical results.

Alternative interpretation of E0 strengths in transitional regions

A strong rise of E0 transition strengths between the first excited 0+ state and the ground state is predicted in shape transitional regions within the Interacting Boson Model (IBM). This rise matches well existing data and is not connected to a large mixing amplitude between both states. Moreover, a coherence of amplitudes in the wave functions causes the strong transition, without a requirement of explicit mixing of normal and intruder configurations. a Conference presenter;

RDDS lifetime measurement with JUROGAM + RITU

Lifetimes in 188Pb were measured using the Koln plunger in combination with the RITU sepa-rator and JUROGAM. Four lifetimes were measured, from which the deformation of the prolate band was experimentally determined for the first time. The squared prolate mixing amplitude of the 2 1 + state was deduced from the measured B(E2) values.

Test of Hyperelasticity in Highly Nonlinear Solids: Sedimentary Rocks

We report measurements of three-wave mixing amplitudes on systems whose third order elastic constants have also been measured by means of the elastoacoustic effect. Because attenuation and diffraction are an important aspect of our measurement technique we analyze our results using a modified Khoklhov-Zabolotskaya-Kuznetsov equation in the frequency domain. We find that the value of beta so deduced for polymethyl methacrylate agrees quite well with that predicted from the stress dependent sound speed measurements, establishing that polymethyl methacrylate may be considered as a hyperelastic solid. The beta values of sedimentary rocks, though they are typically 2 orders of magnitude larger than, e.g., polymethyl methacrylates, are still a factor 3-10 less than those predicted from the elastoacoustic effect.

Constraints onR-parity violating supersymmetry from neutral meson mixing

Upper bounds at the weak scale are put on all ${\ensuremath{\lambda}}_{ijk}^{\ensuremath{'}}{\ensuremath{\lambda}}_{imn}^{\ensuremath{'}}$-type products of $R$-parity violating supersymmetry that may affect ${K}^{0}\ensuremath{-}{\overline{K}}^{0}$ and ${B}^{0}\ensuremath{-}{\overline{B}}^{0}$ mixing. We constrain all possible products, including some not considered before, using next-to-leading order QCD corrections to the mixing amplitudes. Constraints are obtained for both real and imaginary parts of the couplings. We also discuss briefly some correlated decay channels which should be investigated in future experiments.

Exploring flavor structure of supersymmetry breaking from rareBdecays and the unitarity triangle

We study effects of supersymmetric particles in various rare B decay processes as well as in the unitarity triangle analysis. We consider three different supersymmetric models, the minimal supergravity, $\mathrm{SU}(5)$ SUSY GUT with right-handed neutrinos, and the minimal supersymmetric standard model with $U(2)$ flavor symmetry. In the $\mathrm{SU}(5)$ SUSY GUT with right-handed neutrinos, we consider two cases of the mass matrix of the right-handed neutrinos. We calculate direct and mixing-induced CP asymmetries in the $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma}$ decay and CP asymmetry in ${B}_{d}\ensuremath{\rightarrow}\ensuremath{\varphi}{K}_{S}$ as well as the ${B}_{s}--{B}_{s}$ mixing amplitude for the unitarity triangle analysis in these models. We show that large deviations are possible for the $\mathrm{SU}(5)$ SUSY GUT and the $U(2)$ model. The patterns and correlations of deviations from the standard model will be useful to discriminate the different SUSY models in future B experiments.

A 0 0 (980)-ƒ 0(980) mixing and spin asymmetry in the π− p→ηπ 0 n reaction

The mass difference between the K+ and K0 mesons induces mixing of the a 0 0 (980) and f0(980) resonances. The mixing amplitude is large, on the order of \(m(m_{K^0 }^2 - m_{K^ + }^2 )^{1/2} \approx \sqrt \alpha m_K^2 \) near the \(K\bar K\) thresholds, and its phase changes sharply by 90°. A high-energy experiment on the π−p→η π 0n reaction in a polarized target is proposed. In this experiment, the presence of a 0 0 (980)−f0(980) mixing can be unambiguously and simply identified by the presence of a large jump in the azimuthal asymmetry of the cross section for production of the ηπ0 system in the S wave near the \(K\bar K\) thresholds. Our estimates of the magnitude of the polarization effect, which is expected to be observed in the experiment, are almost model-independent.

Ultraviolet sensitivity of rare decays in nonuniversal extra dimensional models

We consider a nonuniversal five dimensional model in which fermions are localised on a four dimensional brane, while gauge bosons and a scalar doublet can travel in the bulk. As a result of KK number non-conservation at the brane-bulk intersection, the ultraviolet divergence does not cancel out in some physical observables. For example, the $B_d \to l^+l^-$ decay amplitude is linearly divergent, while $B$--$\bar{B}$ mixing amplitude is log divergent. We attempt to identify the exact source of this nonrenormalizability. We compare and contrast our results with those obtained in the universal five dimensional model where all particles travel in the extra dimension.

Cosmic Acceleration versus Axion‐Photon Mixing

Axion-photon mixing has been proposed as an alternative to acceleration as the explanation for supernovae dimming. We point out that the loss of photons due to this mixing will induce a strong asymmetry between the luminosity, dL(z), and angular diameter distance, dA(z), since the latter is unaffected by mixing. In a first search for such an asymmetry, we introduce a dimensionless mixing amplitude λ such that λ = 0 if no photons are lost and λ ≈ 1 if axion-photon mixing occurs. The best fit to Type Ia supernovae and radio galaxy data is λ = -0.3 (95% confidence level), corresponding to an unphysical, negative mixing length. This same argument limits the attenuation of light from supernovae due to dust. We show that future dL and dA data from the Supernova/Acceleration Probe and galaxy surveys such as DEEP2 and KAOS will detect or rule out mixing at more than 5 σ almost independently of the dark energy dynamics. Finally, we discuss the constraints from the near-maximal polarization of the gamma-ray burst (GRB) GRB 021206. Since mixing reduces the polarization of distant sources, future observations of high-redshift GRBs will provide orthogonal constraints on axion-photon mixing and related scenarios.

Aspects of a 0 0-f 0 mixing in the reaction $pn \to dX$

Possibilities to study the a 0 0 -f 0 mixing amplitude in meson production reactions in nucleon-nucleon collisions are discussed. It is argued that, even without knowing the production operator, it is possible to gain valuable insights from these reactions.

Quarkonia-Glueball Structure of the Ground Pseudoscalar Mesons

Considering corrections due to SU(3) flavor symmetry breaking, non-ideal ω - ϕ mixing, double OZI and electromagnetic amplitudes of J/ψ decays into a vector and a pseudo-scalar meson, and three-gluon-annihilation amplitudes of radiative decays of J/ψ into a pseudoscalar meson, we investigate two-photon decays of pseudoscalar mesons, radiative decays between pseudoscalar and vector mesons, decays of J/ψ into a vector and a pseudoscalar meson, and radiative decays of J/ψ into a pseudoscalar meson. The quarkonia-glueball structure of η, η′ and η(1440) is phenomenologically deduced from the fit to the updated world average data concerning the above mentioned decays. We find that η (η′) contains about 48.7%, 47.6%, 3.7% (32.9%, 48.8%, 18.3%) non-strange quarkonium, strange quarkonium and glueball components, respectively, and that η(1410) is mainly a glueball state (about 78% glueball component), mixed with 18.5% non-strange quarkonium and 3.5% strange quarkonium. We predict that Br (J/ψ→γη) : Br (J/ψ→γη′) : Br (J/ψ→γη(1410)) = 1.0:5.2:8.0, which can be tested at BEPC/BES with 50 million J/ψ events.

Tracing the string: BMN correspondence at finiteJ2/N

Employing the string bit formalism of hep-th/0209215, we identify the basis transformation that relates BMN operators in N=4 gauge theory to string states in the dual string field theory at finite g_2=J^2/N. In this basis, the supercharge truncates at linear order in g_2, and the mixing amplitude between 1 and 2-string states precisely matches with the (corrected) answer of hep-th/0206073 for the 3-string amplitude in light-cone string field theory. Supersymmetry then predicts the order g_2^2 contact term in the string bit Hamiltonian. The resulting leading order mass renormalization of string states agrees with the recently computed shift in conformal dimension of BMN operators in the gauge theory.

The quarkonia-glueball structure of $\eta$ , $\eta^{'}$ and $\eta(1410)$ revisited

The quarkonia-glueball structure of $\eta$ , $\eta^{'}$ and $\eta(1440)$ is phenomenologically deduced from the updated world average data including two-photon decays of pseudoscalar mesons, radiative decays between pseudoscalar and vector mesons, decays of $J/\psi$ into a vector and a pseudoscalar meson, and radiative decays of $J/\psi$ . Corrections due to SU(3) flavor symmetry breaking, non-ideal $\omega$ - $\phi$ mixing, double OZI and electromagnetic amplitudes of $J/\psi$ decays into a vector and a pseudoscalar meson, and three-gluon-annihilation amplitudes of radiative decays of $J/\psi$ are included in our analysis. Some predictions on the decays involving $\eta(1410)$ are presented, which can be tested at Beijing Electron Positron Collider/Beijing Spectrometer (BEPC/BES) with 50 million $J/\psi$ events.