|A foremost task in understanding the nature of the X(3872) involves the discrimination of the two-quark and multiquark configurations. In this work, we propose a method to probe the short-distance component of the X(3872) by measuring the ratio between the Bc semileptonic and nonleptonic decays into the X(3872). We demonstrate that if the X(3872) production mechanism is through the c¯c component, the ratios would be universal and could be reliably predicted in theory. Measurements of these ratios at LHC and the next-generation electron-positron colliders are capable of validating/invalidating this production mechanism and providing deeper insights into the nature of the X(3872).|
|We demonstrate that the recently observed X,Y,Z states cannot be purely from kinematic effect. Especially the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix which are qualified as states. We propose a way to distinguish cusp effects from genuine states and demonstrate that (not all of) the recently observed X,Y,Z states cannot be purely from kinematic effects. Especially, we show that the narrow near-threshold structures in elastic channels call for nearby poles of the S-matrix, since the normal kinematic cusp effect cannot produce that narrow structures in the elastic channels in contrast to genuine S-matrix poles. In addition, it is also discussed how spectra can be used to distinguish different scenarios proposed for the structure of those poles, such as hadro-quarkonia, tetraquarks and hadronic molecules. The basic tool employed is heavy quark spin symmetry.|
|We propose to study the pentaquark candidates of P+c(4380) and P+c(4450) in J/ψ photoproduction and look for further experimental evidence for their nature. Since the photoproduction process does not satisfy the so-called "anomalous triangle singularity" condition their presence in J/ψ photoproduction would conclude that they should be genuine states and provide further evidence for their existence.|
|We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates P+c(4380) and P+c(4450) via the anomalous triangle singularity (ATS) transitions in the specific kinematics of Λb→J/ψK−p. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the Σ(∗)c can be produced at leading order in Λb decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states.|
|We investigate the anomalous triangle singularity (ATS) and its possible manifestations in various processes. We show that the ATS should have important impact on our understanding of the nature of some newly observed threshold states. Discussions on how to distinguish the ATS phenomena from genuine dynamic pole structures are presented.|
|In order to test different models proposed for some states discovered recently in the charmonium mass range that do not fit into the pattern predicted by the conventional quark model, we derive predictions for the spectrum within the hadro-charmonium picture, the tetraquark picture as well as the hadronic molecular approach. We exploit heavy quark spin symmetry for the hadro-charmonium and hadronic molecule scenarios. The patterns that emerge from the different models turn out to be quite distinct. For example, only within the hadro-charmonium picture a pseudoscalar state emerges that is lighter than the Y(4260). Possible discovery channels of these additional states are discussed.|
|We investigate the Y(4260) production in e+e− annihilations and probe its structure as the D¯D1+c.c. hadronic molecule state. By introducing a compact cc¯ component into the wavefunction in addition to the long-ranged molecular one, we show that the compositeness relation can still provide a reasonable constraint on the wavefunction renormalization parameter. This study confirms the earlier work that the Y(4260) contains predominantly a D¯D1+c.c. molecular component, and its decays into the D¯D∗π+c.c. channel should have a nontrivial lineshape. It provides a natural explanation for the production of Y(4260) in e+e− annihilations in the same framework. It also allows us to predict the Y(4260) leptonic decay width of which the upper limit is about 500 eV.|
Fe deficiency is a widespread nutritional disorder in plants. The basic helix-loop-helix (bHLH) transcription factors (TFs), especially Ib subgroup bHLH TFs which are involved in iron uptake, have been identified. In this study, an IVc subgroup bHLH TF MdbHLH104 was identified and characterized as a key component in the response to Fe deficiency in apple. The overexpression of the MdbHLH104 gene noticeably increased the H+-ATPase activity under iron limitation conditions and the tolerance to Fe deficiency in transgenic apple plants and calli. Further investigation showed that MdbHLH104 proteins bonded directly to the promoter of the MdAHA8 gene, thereby positively regulating its expression, the plasma membrane (PM) H+-ATPase activity and Fe uptake. Similarly, MdbHLH104 directly modulated the expression of three Fe-responsive bHLH genes, MdbHLH38, MdbHLH39 and MdPYE. In addition, MdbHLH104 interacted with 5 other IVc subgroup bHLH proteins to coregulate the expression of the MdAHA8 gene, the activity of PM H+-ATPase and the content of Fe in apple calli. Therefore, MdbHLH104 acts together with other apple bHLH TFs to regulate Fe uptake by modulating the expression of the MdAHA8 gene and the activity of PM H+-ATPase in apple.