5,457 research outputs found

    Virtual contributions from Dβˆ—(2007)0D^{\ast}(2007)^0 and Dβˆ—(2010)Β±D^{\ast}(2010)^{\pm} in the Bβ†’DΟ€hB\to D\pi h decays

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    We study the quasi-two-body decays Bβ†’Dβˆ—hβ†’DΟ€hB\to D^*h \to D\pi h with h=(Ο€,K)h=(\pi, K) in the perturbative QCD approach and focus on the virtual contributions from the off-shell Dβˆ—(2007)0D^{\ast}(2007)^0 and Dβˆ—(2010)Β±D^{\ast}(2010)^{\pm} in the four measured decays BΛ‰0β†’D0Ο€+Ο€βˆ’\bar B^0 \to D^0\pi^+\pi^-, BΛ‰0β†’D0Ο€+Kβˆ’\bar B^0\to D^0\pi^+K^-, Bβˆ’β†’D+Ο€βˆ’Ο€βˆ’B^- \to D^+\pi^-\pi^- and Bβˆ’β†’D+Ο€βˆ’Kβˆ’B^- \to D^+\pi^-K^-. For the BΛ‰0β†’Dβˆ—+Ο€βˆ’β†’D0Ο€+Ο€βˆ’\bar B^0 \to D^{*+}\pi^-\to D^0\pi^+\pi^- and BΛ‰0β†’Dβˆ—+Kβˆ’β†’D0Ο€+Kβˆ’\bar B^0\to D^{*+}K^-\to D^0\pi^+K^- decays, their branching fractions concentrate in a very small region of mD0Ο€+m_{D^0\pi^+} near Dβˆ—+D^{*+} pole mass, and the virtual contributions from Dβˆ—+D^{*+}, in the region mD0Ο€+>2.1m_{D^0\pi^+}>2.1 GeV, are about 5%5\% of the corresponding quasi-two-body results. We define two ratios RDβˆ—+R_{D^{*+}} and RDβˆ—0R_{D^{*0}}, from which we conclude that the flavor-SU(3)SU(3) symmetry will be maintained for the Bβ†’Dβˆ—hβ†’DΟ€hB\to D^* h\to D\pi h decays with very small breaking at any physical value of the mDΟ€m_{D\pi}. The Bβˆ’β†’Dβˆ—0Ο€βˆ’β†’D0Ο€0Ο€βˆ’B^-\to D^{*0}\pi^-\to D^0\pi^0\pi^- and Bβˆ’β†’Dβˆ—0Kβˆ’β†’D0Ο€0Kβˆ’B^-\to D^{*0}K^-\to D^0\pi^0K^- decays can be employed as a constraint for the Dβˆ—0D^{*0} decay width, with preferred values consistent with previous theoretical predictions for this quantity.Comment: 12 pages, 5 figures. Published versio

    Impact of Edge States on Device Performance of Phosphorene Heterojunction Tunneling Field Effect Transistors

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    Black phosphorus (BP) tunneling transistors (TFETs) using heterojunction (He) are investigated by atomistic quantum transport simulations. It is observed that edge states have a great impact on transport characteristics of BP He-TFETs, which result in the potential pinning effect and deteriorate the gate control. While, on-state current can be effectively enhanced by using hydrogen to saturate the edge dangling bonds in BP He-TFETs, in which edge states are quenched. By extending layered BP with a smaller band gap to the channel region and modulating the BP thickness, device performance of BP He-TFETs can be further optimized and fulfill the requirements of the international technology road-map for semiconductors (ITRS) 2013 for low power applications. In 15 nm 3L-1L and 4L-1L BP He-TFETs along armchair direction on-state current can reach above 103^3 ΞΌ\muA/ΞΌ\mum with the fixed off-state current of 10 pA/ΞΌpA/\mum. It is also found that ambipolar effect can be effectively suppressed in BP He-TFETs.Comment: 12 pages, 5 figure

    Extremely long-lived universal resonant Bose gases

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    Quantum simulations based on near-resonance Bose gases are limited by their short lifetimes due to severe atom losses. In addition to this, the recently predicted thermodynamical instability adds another constraint on accessing the resonant Bose gases. In this Letter, we offer a potential solution by proposing long-lived resonant Bose gases in both two and three dimensions, where the conventional few-body losses are strongly suppressed. We show that the thermodynamical properties as well as the lifetimes of these strongly interacting systems are universal, and independent of short-range physics.Comment: 5 page
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