In this paper, we studied the semileptonic decays B → D ( * ) l −ν l by using the "pQCD+Lattice QCD" method. We made the extrapolation for the six relevant form factors by using the input values obtained from the pQCD factorization approach in the low q 2 region of 0 ≤ q 2 ≤ m 2 τ , and the Lattice QCD input at the end-point q 2 = q 2 max . We then calculated the ratios R(D) and R(D * ) of the branching ratios B(B → D ( * ) l −ν l ), and found numerically that (1) the "pQCD+Lattice QCD" predictions for the branching ratios B(B → D ( * ) l −ν l ) agree well with the measured values within one standard deviation; and (2)

In the framework of the top-color-assisted technicolor ͑TC2͒ model, we study a neutral top-pion production process e Ϫ ␥→e Ϫ ⌸ t 0 in this paper. Our results show that the production cross section of e Ϫ ␥→e Ϫ ⌸ t 0 can reach the level of several tens of femtobarns, and over 10 3 neutral top-pion events can be produced in the planned e ϩ e Ϫ linear colliders each year. Therefore, such a top-pion production process provides us a unique chance to detect top-pion events and test the TC2 model. On the other hand, the cross section of e Ϫ ␥ →e Ϫ ⌸ t 0 is about one order of magnitude larger than those of some similar processes in the standard model ͑SM͒ and the minimally supersymmetric standard model ͑MSSM͒ ͓i.e., e Ϫ ␥→e Ϫ H in the SM and e Ϫ ␥ →e Ϫ H 0 (A 0 ,h 0 ) in the MSSM͔. So we can easily distinguish the neutral top-pion from other neutral Higgs bosons in the SM and MSSM.

Recently, the CDF and DØ collaborations have claimed that the CP violating phase in B 0 s −B 0 s mixing is large, which is contrary to the expectations in the Standard Model. Such a large phase suggests New Physics contributions to B 0 s −B 0 s mixing. Motivated by this, we reevaluate the constraints on R-parity violating contributions, including baryon number violating couplings not considered before, to the mixing mass matrix element M s 12 from the recent measurements of B 0 s −B 0 s mixing. We show that present data allow us to put quite strong constraints on both the magnitudes and the weak phases of the R-parity violating parameters. Some of these bounds are better than the existing ones, and some bounds are obtained for the first time. Near future experiments at the Tevatron, the LHC and B-factories can shrink or reveal the relevant parameter spaces of the R-parity violating couplings.

In the littlest Higgs model with T-parity (LHT), the mirror quarks have flavor structures and will contribute to the top quark flavor changing neutral current. In this work, we perform an extensive investigation of the top quark rare three-body decays t ! cVV, (V ¼ , Z, g) and t ! cf "f, (f ¼ b, , , e) at one-loop level. Our results show that the branching ratios of t ! cgg and t ! cb " b could reach Oð10 À3 Þ in the favorite parameter space of the littlest Higgs model with T-parity, which implies that these decays may be detectable at the LHC or ILC, while for the other decays, their rates are too small to be observable at the present or future colliders.

No abstract

No abstract

The electrical transport properties of CoSi2 and Co(SixGe1−x)2 thin films formed by solid state interaction and co-evaporation in the range of 4–300 K were studied. The Hall effect data indicate a hole carrier conduction in all samples. The rapid thermal annealed CoSi2 exhibits a typical metallic conduction with a residual resistivity of 3.3-μΩ-cm and room-temperature (RT) resistivity of 15 μΩ cm. The co-evaporated CoSi2 and Co(Si0.9Ge0.1)2 films after low temperature annealing up to 250 °C show a low resistivity of 70–80 μΩ cm at RT and change little down to 4 K. The hole carrier density of all the samples studied has values close to 2–3×1022 cm−3, while the carrier Hall mobility has large differences.

We have studied a neutral toppion production process γγ → f f Π 0 t (f = t, b) in the topcolor-assisted technicolor(TC2) model. We find that the cross section of γγ → ttΠ 0 t is much larger than that of γγ → bbΠ 0 t . On the other hand, the cross section can be obviously enhanced with the increasing of c.m.energy. With √ s = 1600 GeV, the cross section of ttΠ 0 t production can reach the level of a few fb. The results show that γγ → ttΠ 0 t → tt(tc) is the most ideal channel to detect neutral toppion due to the clean SM background. With such sufficient signals and clean background, neutral toppion could be detected at TESLA with high c.m.energy.