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1. chinaXiv:201609.01010 [pdf]

The nature of near-threshold XYZ states

Martin Cleven; Feng-Kun Guo; Christoph Hanhart; Qian Wang; Qiang Zhao
Subjects: Physics >> Nuclear Physics

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.

submitted time 2016-09-14 Hits1329Downloads779 Comment 0

2. chinaXiv:201609.00979 [pdf]

Photoproduction of hidden charm pentaquark states $P_c^+(4380)$ and $P_c^+(4450)$

Qian Wang; Xiao-Hai Liu; Qiang Zhao
Subjects: Physics >> Nuclear Physics

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.

submitted time 2016-09-14 Hits1268Downloads761 Comment 0

3. chinaXiv:201609.00974 [pdf]

Understanding the newly observed heavy pentaquark candidates

Xiao-Hai Liu; Qian Wang; Qiang Zhao
Subjects: Physics >> Nuclear Physics

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.

submitted time 2016-09-14 Hits1451Downloads895 Comment 0

4. chinaXiv:201609.00927 [pdf]

Employing spin symmetry to disentangle different models for the XYZ states

Martin Cleven; Feng-Kun Guo; Christoph Hanhart; Qian Wang; Qiang Zhao
Subjects: Physics >> Nuclear Physics

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.

submitted time 2016-09-13 Hits1498Downloads893 Comment 0

5. chinaXiv:201605.00462 [pdf]

Metabolic engineering of terpene biosynthesis in plants using a trichome‐specific transcription factor MsYABBY5 from spearmint (Mentha spicata)

Qian Wang; Vaishnavi Amarr Reddy; Deepa Panicker; Hui-Zhu Mao; Nadimuthu Kumar; Chakravarthy Rajan; Prasanna Nori Venkatesh; Nam-Hai Chua; Rajani Sarojam
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics

In many aromatic plants including spearmint (Mentha spicata), the sites of secondary metabolite production are tiny specialized structures called peltate glandular trichomes (PGT). Having high commercial values, these secondary metabolites are exploited largely as flavours, fragrances and pharmaceuticals. But, knowledge about transcription factors (TFs) that regulate secondary metabolism in PGT remains elusive. Understanding the role of TFs in secondary metabolism pathway will aid in metabolic engineering for increased yield of secondary metabolites and also the development of new production techniques for valuable metabolites. Here, we isolated and functionally characterized a novel MsYABBY5 gene that is preferentially expressed in PGT of spearmint. We generated transgenic plants in which MsYABBY5 was either overexpressed or silenced using RNA interference (RNAi). Analysis of the transgenic lines showed that the reduced expression of MsYABBY5 led to increased levels of terpenes and that overexpression decreased terpene levels. Additionally, ectopic expression of MsYABBY5 in Ocimum basilicum and Nicotiana sylvestris decreased secondary metabolite production in them, suggesting that the encoded transcription factor is probably a repressor of secondary metabolism.

submitted time 2016-05-04 Hits2526Downloads1476 Comment 0

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