Probing the nature of Y(4260)Y(4260) and Zc(3900)Z_c(3900) in the isospin violating process Y(4260)→J/ψηπ0Y(4260) \to J/\psi \eta \pi^0

The isospin violation process $Y(4260) \to J/\psi \eta \pi^{0}$ is studied assuming that $Y(4260)$ is a $D_{1} \bar{D}+c.c.$ hadronic molecule. In association with the production of the $Z_c(3900)$, which is treated as a $D \bar{D}^{*}+c.c.$ hadronic molecule, this process can help us distinguish their molecular natures from other scenarios, since the incomplete cancellation between the charged and neutral--meson loops, which are prominent in the molecular picture only, produces a peak in the $e^+e^-\to Y(4260)\to J/\psi\eta\pi^0$ cross section at the $D_{1} \bar{D}+c.c.$ threshold and a very prominent peak in the $J/\psi \eta$ invariant mass spectrum in between the $D \bar{D}^{*}+c.c.$ thresholds; the latter being much narrower than the corresponding one in the isospin conserving channel, i.e. $J/\psi \pi^+ \pi^{-}$. The partial width of $Y(4260)\to J/\psi\eta\pi^0$ is about $4 \times 10^{-4}$ of that of $Y(4260)\to J/\psi\pi^+\pi^-$. The cross section of $e^+e^-\to Y(4260)\to J/\psi\eta\pi^0$ at the $D_{1} \bar{D}+c.c.$ threshold is about $0.05 \ \mathrm{pb}$ which is much larger than that produced by the nearby resonances. These features are the direct consequences of the assumed nature of these two states which might be accessible at the high-statistics experiments such as BESIII and LHCb.Comment: 11 pages, 4 figure

Further understanding of the non-DDˉD\bar D decays of ψ(3770)\psi(3770)

We provide details of the study of $\psi(3770)$ non-$D\bar D$ decays into $VP$, where $V$ and $P$ denote light vector meson and pseudoscalar meson, respectively. We find that the electromagnetic (EM) interaction plays little role in these processes, while the strong interaction dominates. The strong interaction can be separated into two parts, i.e. the short-distance part probing the wave function at origin and the long-distance part reflecting the soft gluon exchanged dynamics. The long-distance part is thus described by the intermediate charmed meson loops. We show that the transition of $\psi(3770)\to VP$ can be related to $\psi(3686)\to VP$ such that the parameters in our model can be constrained by comparing the different parts in $\psi(3770)\to VP$ to those in $\psi(3686)\to VP$. Our quantitative results confirm the findings of [Zhang {\it et al.}, Phys. Rev. Lett. 102, 172001 (2009)] that the OZI-rule-evading long-distance strong interaction via the IML plays an important role in $\psi(3770)$ decays, and could be a key towards a full understanding of the mysterious $\psi(3770)$ non-$D\bar{D}$ decay mechanism.Comment: 11 pages, 4 figures, version to appear in Phys. Rev.

Non-Spectator Contributions to Inclusive Charmless BB Decays

The light quarks inside $B$ mesons are usually treated as spectators and do not affect the decay rates which are assumed to be purely due to b quark decays. In this paper we calculate the non-spectator contributions to inclusive charmless $B$ decays due to the spectator effects. We find that the non-spectator contributions to the branching ratio for $\bar B^0$ are small ($<2\times 10^{-4}$), but the contributions to $\Delta S = 0$ and $\Delta S = -1$, $B^-$ decay branching ratios can be as large as $-7.5\times 10^{-4}$ and $2\times 10^{-3}$, respectively. These contributions may play an important role in rare charmless $B$ decays.Comment: 11 pages, Revte

Social Turing Tests: Crowdsourcing Sybil Detection

As popular tools for spreading spam and malware, Sybils (or fake accounts) pose a serious threat to online communities such as Online Social Networks (OSNs). Today, sophisticated attackers are creating realistic Sybils that effectively befriend legitimate users, rendering most automated Sybil detection techniques ineffective. In this paper, we explore the feasibility of a crowdsourced Sybil detection system for OSNs. We conduct a large user study on the ability of humans to detect today's Sybil accounts, using a large corpus of ground-truth Sybil accounts from the Facebook and Renren networks. We analyze detection accuracy by both "experts" and "turkers" under a variety of conditions, and find that while turkers vary significantly in their effectiveness, experts consistently produce near-optimal results. We use these results to drive the design of a multi-tier crowdsourcing Sybil detection system. Using our user study data, we show that this system is scalable, and can be highly effective either as a standalone system or as a complementary technique to current tools