A channel Brownian pump powered by an unbiased external force

A Brownian pump of particles in an asymmetric finite tube is investigated in the presence of an unbiased external force. The pumping system is bounded by two particle reservoirs. It is found that the particles can be pumped through the tube from a reservoir at low concentration to one at the same or higher concentration. There exists an optimized value of temperature (or the amplitude of the external force) at which the pumping capacity takes its maximum value. The pumping capacity decreases with increasing the radius at the bottleneck of the tube.Comment: 14 pages, 9 figure

The Importance of Proper Renormalization Scale-Setting for Testing QCD at Colliders

A primary problem for perturbative QCD analyses is how to set the renormalization scale of the QCD running coupling in order to achieve maximally precise fixed-order predictions for physical observables. The Principle of Maximum Conformality (PMC) eliminates the ambiguities associated with the conventional renormalization scale-setting procedure, giving predictions which are independent of the choice of renormalization scheme. The scales of the QCD couplings and the effective number of quark flavors are set order by order in the pQCD series. The PMC has a solid theoretical foundation, satisfying the standard renormalization group invariance and all of the the self-consistency conditions derived from the renormalization group......In this brief report, we summarize the results of our recent PMC applications for a number of collider processes, emphasizing their generality and applicability....... These results demonstrate that the application of the PMC systematically eliminates a major theoretical uncertainty for pQCD predictions, thus increasing the sensitivity of the colliders to possible new physics beyond the Standard Model.Comment: 10 pages, 4 figures. The title has been changed. This review, submitted to Frontiers of Physics, is based on a contribution by S.J.B. at the Conference {\it Workshop on Physics at a Future High Intensity Collider @ 2-7 GeV in China} Hefei, China January 14-16, 201

A precise determination of the top-quark pole mass

The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate the renormalization scheme and renormalization scale uncertainties for high-energy processes. We have observed that by applying PMC scale-setting, one obtains comprehensive and self-consistent pQCD predictions for the top-quark pair total cross-section and the top-quark pair forward-backward asymmetry in agreement with the measurements at the Tevatron and LHC. As a step forward, in the present paper, we determine the top-quark pole mass via a detailed comparison of the top-quark pair cross-section with the measurements at the Tevatron and LHC. The results for the top-quark pole mass are $m_t=174.6^{+3.1}_{-3.2}$ GeV for the Tevatron with $\sqrt{S}=1.96$ TeV, $m_t=173.7\pm1.5$ GeV and $174.2\pm1.7$ GeV for the LHC with $\sqrt{S} = 7$ TeV and $8$ TeV, respectively. Those predictions agree with the average, $173.34\pm0.76$ GeV, obtained from various collaborations via direct measurements. The consistency of the pQCD predictions using the PMC with all of the collider measurements at different energies provides an important verification of QCD.Comment: 10 pages, 6 figures. Revised version to be published in Eur.Phys.J.