Chromo-polarizability and pipi final state interaction

The chromo-polarizability of a quarkonium state is a measure of the amplitude of the $E1$-$E1$ chromo-electric interaction of the quarkonium with soft gluon fields and can be measured in the heavy quarkonium decays. Based on the chiral unitary approach, formulas with modification caused by the $S$ wave $\pi\pi$ final state interaction (FSI) for measuring the chromo-polarizabilities are given. It is shown that the effect of the $S$ wave $\pi\pi$ FSI is very important in extracting chromo-polarizabilities from the experimental data. The resultant values with the FSI are reduced to about 1/3 of those determined without the FSI. The consequences of the FSI correction in the $J/\psi$-nucleon scattering near the threshold are also discussed. The estimated lower bound of the total cross section is reduced from about 17 mb to 2.9 mb, which agrees with the experimental data point and is compatible with the previously estimated values in the literature. In order to understand the interaction of heavy quarkonia with light hadrons at low energies better and to obtain the chromo-polarizabilities of quarkonia accurately, more data should be accumulated. This can be done in the $J/\psi \to \pi^+\pi^-l^+l^-$ decay at BES-III and CLEO-c and in the $\Upsilon \to \pi^+\pi^-l^+l^-$ decay at B factories.Comment: 5 pages, 3 figures, ReVTeX4. Version accepted for publication in Phys. Rev.

The role of N∗(1535)N^*(1535) in pp→ppϕpp \to pp \phi and π−p→nϕ\pi^- p \to n \phi reactions

The near threshold $\phi$ meson production in proton-proton and $\pi^- p$ collisions is studied with the assumption that the production mechanism is due to the sub-$N\phi$-threshold $N^*(1535)$ resonance. The $\pi^0$, $\eta$ and $\rho^0$-meson exchanges for proton-proton collisions are considered. It is shown that the contribution to the $pp \to pp \phi$ reaction from the t-channel $\pi^0$ meson exchange is dominant. With a significant $N^*(1535)N\phi$ coupling ($g^2_{N^*(1535)N \phi}/4 \pi$ = 0.13), both $pp \to pp \phi$ and $\pi^- p \to n \phi$ data are very well reproduced. The significant coupling of the $N^*(1535)$ resonance to $N \phi$ is compatible with previous indications of a large $s \bar{s}$ component in the quark wave function of the $N^*(1535)$ resonance and may be the real origin of the significant enhancement of the $\phi$ production over the naive OZI-rule predictions.Comment: 15 pages, 6 figure

On the structure of the pi pi invariant mass spectra of the Upsilon(4S)-->Upsilon(1S,2S) pi^+ pi^- decays

We perform a model-independent analysis for recently reported data of the $\pi^+\pi^-$ invariant mass spectra in the $\Upsilon(4S)\to\Upsilon(1S,2S)\pi^+\pi^-$ decays and point out that there does exist a broad peak below 0.6 GeV in the data of the $\Upsilon(4S)\to\Upsilon(1S)\pi^+\pi^-$ decay, which is analogous to that in the $\Upsilon(3S)\to\Upsilon(1S)\pi^+\pi^-$ decay. With the data of $\Upsilon(4S)$ decays, we further test our model developed for studying the puzzle in the $\Upsilon(3S)\to\Upsilon(1S)\pi^+\pi^-$ decay. The result shows that with such a model, all the $\pi^+\pi^-$ invariant mass spectra of $\Upsilon(4S)$ decays can be described. We also predict the $\cos\theta_{\pi}^*$ distributions of $\Upsilon(4S)\to\Upsilon(1S,2S)\pi^+\pi^-$ decays, which can be used to justify our model prediction.Comment: 11 pages, 5 figures. Extended to include new data; title changed. Version accepted for publication in Phys. Lett.

Dynamically generated 0^+ heavy mesons in a heavy chiral unitary approach

In terms of the heavy chiral Lagrangian and the unitarized coupled-channel scattering amplitude, interaction between the heavy meson and the light pseudoscalar meson is studied. By looking for the pole of scattering matrix on an appropriate Riemann sheet, a $DK$ bound state $D_{s0}^*$ with the mass of $2.312\pm0.041$ GeV is found. This state can be associated as the narrow $D_{sJ}^*(2317)$ state found recently. In the same way, a $B{\bar K}$ bound state $B_{s0}^*$ is found, and its mass of $5.725\pm0.039$ GeV is predicted. The spectra of $D_0^*$ and $B_0^*$ with $I=1/2$ are further investigated. One broad and one narrow states are predicted in both charm and bottom sectors. The coupling constants and decay widths of the predicted states are also calculated.Comment: 15 pages, 1 figure. One numerical error in Eq.16 correcte

Fluorescence detection of single nucleotide polymorphisms using a universal molecular beacon

We present a simple and novel assay—employing a universal molecular beacon (MB) in the presence of Hg2+—for the detection of single nucleotide polymorphisms (SNPs) based on Hg2+–DNA complexes inducing a conformational change in the MB. The MB (T7-MB) contains a 19-mer loop and a stem of a pair of seven thymidine (T) bases, a carboxyfluorescein (FAM) unit at the 5′-end, and a 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) unit at the 3′-end. Upon formation of Hg2+–T7-MB complexes through T–Hg2+–T bonding, the conformation of T7-MB changes from a random coil to a folded structure, leading to a decreased distance between the FAM and DABCYL units and, hence, increased efficiency of fluorescence resonance energy transfer (FRET) between the FAM and DABCYL units, resulting in decreased fluorescence intensity of the MB. In the presence of complementary DNA, double-stranded DNA complexes form (instead of the Hg2+–T7-MB complexes), with FRET between the FAM and DABCYL units occurring to a lesser extent than in the folded structure. Under the optimal conditions (20 nM T7-MB, 20 mM NaCl, 1.0 μM Hg2+, 5.0 mM phosphate buffer solution, pH 7.4), the linear plot of the fluorescence intensity against the concentration of perfectly matched DNA was linear over the range 2–30 nM (R2 = 0.991), with a limit of detection of 0.5 nM at a signal-to-noise ratio of 3. This new probe provides higher selectivity toward DNA than that exhibited by conventional MBs

Dynamically generated 1^+ heavy mesons

By using a heavy chiral unitary approach, we study the $S$ wave interactions between heavy vector meson and light pseudoscalar meson. By searching for poles of the unitary scattering amplitudes in the appropriate Riemann sheets, several $1^+$ heavy states are found. In particular, a $D^*K$ bound state with a mass of $2.462\pm0.010$ GeV which should be associated with the recently observed $D_{s1}(2460)$ state is obtained. In the same way, a $B^*{\bar K}$ bound state ($B_{s1}$) with mass of $5.778\pm0.007$ GeV in the bottom sector is predicted. The spectra of the dynamically generated $D_1$ and $B_1$ states in the $I=1/2$ channel are also calculated. One broad state and one narrow state are found in both the charmed and bottom sectors. The coupling constants and decay widths of the predicted states are further investigated.Comment: 17 pages, 3 figures. Version accepted for publication in Phys. Lett.

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data