Iterative Decoding and Soft Interference Cancellation in Fast Frequency Hopping Multiuser System Using Clipped Combining

Iterative decoding (ID) aided fast frequency hopping (FFH), M-ary frequency shift keying (MFSK) using clipped combining in multiple access (MA) channels is investigated. All users’ data are convolutionally encoded and the encoded bits are interleaved and converted to M-ary symbols, which are transmitted using FFH-MFSK modulation. The soft metrics to be passed from the demodulator to the decoder are derived assuming a Rayleigh fading channel. We also propose a novel multiuser detection (MUD) scheme which employs joint soft decoding as well as successive interference cancellation (SIC), the receiver exploiting the soft information fed back by the decoder to the demodulator in order to cancel the interference imposed by reliable symbols. Our simulation results show that the proposed scheme is capable of combatting multiuser interference and outperforms the conventional ID by about 3dB

Comments on the Quark Content of the Scalar Meson f0(1370)f_0(1370)

Based on the measurements of $(D_s^+,D^+)\to f_0(1370)\pi^+$ we determine, in a model independent way, the allowed $s\bar s$ content in the scalar meson $f_0(1370)$. We find that, on the one hand, if this isoscalar resonance is a pure $n\bar n$ state [ $n\bar n\equiv(u\bar u+d\bar d)/\sqrt{2} ]$, a very large $W$-annihilation term will be needed to accommodate $D_s^+\to f_0(1370)\pi^+$. On the other hand, the $s\bar s$ component of $f_0(1370)$ should be small enough to avoid excessive $D_s^+\to f_0(1370)\pi^+$ induced from the external $W$-emission. Measurement of $f_0(1370)$ production in the decay $D_s^+\to K^+K^-\pi^+$ will be useful to test the above picture. For the decay $D^0\to f_0(1370)\bar K^0$ which is kinematically barely or even not allowed, depending on the mass of $f_0(1370)$, we find that the finite width effect of $f_0(1370)$ plays a crucial role on the resonant three-body decay $D^0\to f_0(1370)\bar K^0\to\pi^+\pi^-\bar K^0$.Comment: 12 pages, 2 figure

Hadronic Charmed Meson Decays Involving Tensor Mesons

Charmed meson decays into a pseudoscalar meson P and a tensor meson T are studied. The charm to tensor meson transition form factors are evaluated in the Isgur-Scora-Grinstein-Wise (ISGW) quark model. It is shown that the Cabibbo-allowed decay $D_s^+\to f_2(1270)\pi^+$ is dominated by the W-annihilation contribution and has the largest branching ratio in $D\to TP$ decays. We argue that the Cabibbo-suppressed mode $D^+\to f_2(1270)\pi^+$ should be suppressed by one order of magnitude relative to $D_s^+\to f_2(1270)\pi^+$. When the finite width effect of the tensor resonances is taken into account, the decay rate of $D\to TP$ is generally enhanced by a factor of $2\sim 3$. Except for $D_s^+\to f_2(1270)\pi^+$, the predicted branching ratios of $D\to TP$ decays are in general too small by one to two orders of magnitude compared to experiment. However, it is very unlikely that the $D\to T$ transition form factors can be enhanced by a factor of $3\sim 5$ within the ISGW quark model to account for the discrepancy between theory and experiment. As many of the current data are still preliminary and lack sufficient statistic significance, more accurate measurements are needed to pin down the issue.Comment: 11 page

Experimental studies on theoretical linguistics

Theoretical and Experimental Linguistic

Hadronic Charmed Meson Decays Involving Axial Vector Mesons

Cabibbo-allowed charmed meson decays into a pseudoscalar meson and an axial-vector meson are studied. The charm to axial-vector meson transition form factors are evaluated in the Isgur-Scora-Grinstein-Wise quark model. The dipole momentum dependence of the $D\to K$ transition form factor and the presence of a sizable long-distance $W$-exchange are the two key ingredients for understanding the data of $D\to \bar Ka_1$. The $K_{1A}-K_{1B}$ mixing angle of the strange axial-vector mesons is found to be $\approx \pm37^\circ$ or $\pm58^\circ$ from $\tau\to K_1\nu_\tau$ decays. The study of $D\to K_1(1270)\pi, K_1(1400)\pi$ decays excludes the positive mixing-angle solutions. It is pointed out that an observation of the decay $D^0\to K_1^-(1400)\pi^+$ at the level of $5\times 10^{-4}$ will rule out $\theta\approx -37^\circ$ and favor the solution $\theta\approx -58^\circ$. Though the decays $D^0\to \bar K_1^0\pi^0$ are color suppressed, they are comparable to and even larger than the color-allowed counterparts: $\bar K_1^0(1270)\pi^0\sim K_1^-(1270)\pi^+$ and $\bar K_1^0(1400)\pi^0> K_1^-(1400)\pi^+$. The finite width effect of the axial-vector resonance is examined. It becomes important for $a_1(1260)$ in particular when its width is near 600 MeV.Comment: 19 page

Nonresonant Three-body Decays of D and B Mesons

Nonresonant three-body decays of D and B mesons are studied. It is pointed out that if heavy meson chiral perturbation theory (HMChPT) is applied to the heavy-light strong and weak vertices and assumed to be valid over the whole kinematic region, then the predicted decay rates for nonresonant charmless 3-body B decays will be too large and especially B^- --> pi^- K^+ K^- greatly exceeds the current experimental limit. This can be understood as chiral symmetry has been applied there twice beyond its region of validity. If HMChPT is applied only to the strong vertex and the weak transition is accounted for by the form factors, the dominant B^* pole contribution to the tree-dominated direct three-body B decays will become small and the branching ratio will be of order 10^{-6}. The decay modes B^- --> (K^- h^+ h^-)_{NR} and bar{B}^0 --> (bar{K}^0 h^+h^-)_{NR} for h = pi, K are penguin dominated. We apply HMChPT in two different cases to study the direct 3-body D decays and compare the results with experiment. Theoretical uncertainties are discussed.Comment: 24 pages, 2 figures. New experimental results of direct 3-body D decays as Reported at ICHEP2002 are included. To appear in Phys. Re

Effects of Adding Unsaturated Fatty Acids on Fatty Acid Composition of Saccharomyces cerevisiae and Major Volatile Compounds in Wine

The synergistic influences of three unsaturated fatty acids (UFAs, namely linoleic acid, oleic acid andlinolenic acid) on the fatty acid composition of Saccharomyces cerevisiae and major volatile compoundswere investigated in synthetic grape juice. The addition of UFAs led to a corresponding increase in UFAsin the cellular lipid, which was accompanied by a reverse reduction in the content of medium-chainsaturated fatty acids (C6:0 to C14:0) and little variation in that of long-chain saturated fatty acids (C16:0to C24:0). The supplementation of UFAs considerably improved yeast growth and fermentation activityand, in particular, increased the concentrations of most volatile compounds in wine, including higheralcohols (2-phenylethanol, 2-methyl-1-propanol and 3-(methylthio)-1-propanol), medium-chain fattyacids (butanoic acid, hexanoic acid and octanoic acid), acetate esters (isoamyl acetate and 2-phenylethylacetate) and all ethyl esters. Remarkable linear relationships were further found between ethyl esters andthe concentration of the added UFAs (R2 from 0.909 to 0.996), which significantly intensified the fruity,flowery and sweet attributes of the final wine, as assessed by calculating the odour activity values. Ourresults suggest that rationally increasing the concentration of UFAs is not only a practical method toimprove yeast fermentation activity, but also a potential approach to manipulating wine aroma

Final-State Phases in B→Dπ,D∗πB \to D \pi, D^* \pi, and DρD \rho Decays

The final-state phases in $\bar{B} \to D \pi, D^* \pi$, and $D \rho$ decays appear to follow a pattern similar to those in $D \to \bar{K} \pi$, $\bar{K}^* \pi$, and $\bar{K} \rho$ decays. Each set of processes is characterized by three charge states but only two independent amplitudes, so the amplitudes form triangles in the complex plane. For the first two sets the triangles appear to have non-zero area, while for the $D \rho$ or $\bar{K} \rho$ decays the areas of the triangles are consistent with zero. Following an earlier discussion of this behavior for $D$ decays, a similar analysis is performed for B decays, and the relative phases and magnitudes of contributing amplitudes are determined. The significance of recent results on \ob \to D^{(*)0} \bar{K}^{(*)0} is noted. Open theoretical and experimental questions are indicated.Comment: 16 pages, LaTeX, 3 figures, to be submitted to Phys. Rev. D. References added; comments on new experimental results and analysi

Top-Quark Pair Production Beyond Next-to-Leading Order

We report on recent calculations of the differential cross section for top-quark pair production at hadron colliders. The results are differential with respect to the top-pair invariant mass and to the partonic scattering angle. In these calculations, which were carried out by employing soft-collinear effective theory techniques, we resummed threshold logarithms up to next-to-next-to-leading logarithmic order. Starting from the differential cross section, it is possible to obtain theoretical predictions for the invariant-mass distribution and the total cross section. We summarize here our results for these observables, and we compare them with the results obtained from different calculational methods.Comment: Talk presented at Loops and Legs in Quantum Field Theory 2010, Woerlitz, Germany, April 25-30, 2010. 6 page