Masses of Scalar and Axial-Vector B Mesons Revisited

The SU(3) quark model encounters a great challenge in describing even-parity mesons. Specifically, the $q\bar q$ quark model has difficulties in understanding the light scalar mesons below 1 GeV, scalar and axial-vector charmed mesons and $1^+$ charmonium-like state $X(3872)$. A common wisdom for the resolution of these difficulties lies on the coupled channel effects which will distort the quark model calculations. In this work, we focus on the near mass degeneracy of scalar charmed mesons, $D_{s0}^*$ and $D_0^{*0}$, and its implications. Within the framework of heavy meson chiral perturbation theory, we show that near degeneracy can be qualitatively understood as a consequence of self-energy effects due to strong coupled channels. Quantitatively, the closeness of $D_{s0}^*$ and $D_0^{*0}$ masses can be implemented by adjusting two relevant strong couplings and the renormalization scale appearing in the loop diagram. Then this in turn implies the mass similarity of $B_{s0}^*$ and $B_0^{*0}$ mesons. The $P_0^* P'_1$ interaction with the Goldstone boson is crucial for understanding the phenomenon of near degeneracy. Based on heavy quark symmetry in conjunction with corrections from QCD and $1/m_Q$ effects, we obtain the masses of $B^*_{(s)0}$ and $B'_{(s)1}$ mesons, for example, $M_{B_{s0}^*}= (5715\pm1)\,{\rm MeV}+\delta\Delta_S$, $M_{B'_{s1}}=(5763\pm1)\,{\rm MeV}+\delta\Delta_S$ with $\delta\Delta_S$ being $1/m_Q$ corrections. We find that the predicted mass difference of 48 MeV between $B'_{s1}$ and $B_{s0}^*$ is larger than that of $20\sim 30$ MeV inferred from the relativistic quark models, whereas the difference of 15 MeV between the central values of $M_{B'_{s1}}$ and $M_{B'_1}$ is much smaller than the quark model expectation of $60-100$ MeV.Comment: 21 pages, 1 figure, to appear in Eur. Phys. J. (2017). arXiv admin note: text overlap with arXiv:1404.377

Dithiolopyrrolone Natural Products : Isolation, Synthesis and Biosynthesis

Peer reviewedPublisher PD

Preparation and characterization of hydrogenated amorphous germanium and hydrogenated amorphous germanium carbide thin films

Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge[subscript] 1-xC[subscript] x:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum ~4 x 10[superscript]-7 Torr at various rf power 50 ≤ P ≤ 600 W (0.27-3.3 W/cm[superscript]2), target-substrate distance 1 ≤ d ≤ 7[superscript]\u27\u27, varying partial pressures of Ar, H[subscript]2, and C[subscript]3H[subscript]8, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity [sigma][subscript] ph, in particular, was carefully monitored as a function of the deposition conditions to optimize it;The concentration of Ge-H bonds and the optical gap (E[subscript] g), generally decrease as P is increased. E[subscript] g of the a-Ge[subscript] 1-xC[subscript] x:H films range from 0.85-2.3 eV. The ESR results range from 2 x 10[superscript]17 to 2 x 10[superscript]19 spins/cm[superscript]3. Results of annealing showed the enhanced segregation effect of Ge-C bonds ≥300°C. The evolution of bonded hydrogen with temperature is studied;Deposition rates (R[subscript] d) of a-Ge:H films are estimated and compared. The thermalization curve for a Ge target is constructed. R[subscript] d was found to decrease exponentially with increasing d, to decrease with increasing partial pressures of H[subscript]2 and C[subscript]3H[subscript]8 and increasing flow rates. R[subscript] d is maximal at some P[subscript] Ar and is relatively insensitive to the substrate temperature T[subscript] s, and rises linearly with the rf power;Hydrogen incorporation markedly increased [sigma][subscript] ph. The dark conductivity [sigma][subscript] d and [sigma][subscript] ph increase with increasing d, up to an optimal value at d ~ 6[superscript]\u27\u27, increase at f \u3c 1 sccm, and increase with P and T[subscript] s. Incorporation of significant amounts of carbon sharply reduces [sigma][subscript] ph. However, a small amount has little effect on [sigma][subscript] ph. Although all increases in [sigma][subscript] ph are significant relative to those of previously reported rf sputtered a-Ge:H, the results in this work are still much lower than those of glow discharged films, which are lower than those of rf magnetron sputtered films grown in high vacuum (\u3c5 x 10[superscript]-9 Torr). The parallel behavior of [sigma][subscript] d and [sigma][subscript] ph, the relatively long lifetimes of the carriers [tau] ~ 0.8 ms but rather low mobility [mu] ~ 5 x 10[superscript]7 cm[superscript]2/V-sec and low subgap absorption suggest that the transport is dominated by defects near the mobility edge. The failure in identifying the effect of electron bombardment of the growing film by using biased screen suggests that the high values of [sigma][subscript] ph reported from rf magnetron sputtering are probably partially due to the high background vacuum. ftn*DOE Report IS-T-1377. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

Renormalization group improved predictions for ttˉW±t\bar{t}W^\pm production at hadron colliders

We study the factorization and resummation of the $t\bar{t}W^\pm$ production at hadron colliders. The cross section in the threshold limit can be factorized into a convolution of hard and soft functions and parton distribution functions with the soft-collinear effective theory. We calculate the next-to-leading order soft function for the associated production of the heavy quark pair and colorless particle, and we perform the resummation calculation with the next-to-next-to-leading logarithms accuracy. Our results show that the resummation effects reduce the dependence of the cross section on the scales significantly and increase the total cross section by $7-13\%$ compared with NLO QCD results.Comment: 23 pages, 7 figures and 2 tables; final version in PR