Exotic Hybrid Research Articles

Relativistic many-body approach to exotic and charmed hybrid mesons

A relativistic many-body calculation for an effective QCD Hamiltonians reported for exotic and charmed hybrid mesons. The nonexotic J(PC) = 1(--) charmonium spectrum now resolves the anonymous overpopulation of observed J/psi states. The exotic hybrid states are near but above 2 GeV, in agreement with lattice and flux-tube calculations, indicating the recently observed J(PC) = 1(+-) resonances at 1.4 and 1.6 GeV are not hybrids.

Heavy quarkonia from anisotropic and isotropic lattices

We report on recent results for the spectrum of heavy quarkonia. Using coarse and anisotropic lattices we achieved an unprecedented control over statistical and systematic errors for higher excited states such as exotic hybrid states. In a parallel study on isotropic lattices we also investigate the effect of two dynamical flavours on the spin structure of charmonium and bottomonium for several symmetric lattices.

Hybrid quarkonium masses up to the order of1/mQ

We have calculated the binding energy of the hybrid quarkonium up to the order of ${\cal O}(1/m_Q)$ and found their decay constants scale like $m_Q^{5/4}$ as $m_Q\to \infty$. The $0^{--}$ and $0^{++}$ hybrid quarkonium is exactly degenerate in the limit of $m_Q\to\infty$ while the ${\cal O}(1/m_Q)$ correction renders the $0^{--}$ mass lower than that for $0^{++}$. The $1^{-+}$ and $1^{+-}$ hybrid is nearly degenerate and lies 0.7 GeV lower than $0^{--}$. With $m_b=4.8$GeV the mass of $1^{-+}$ $b\bar b g$ state is $(10.75\pm 0.10)$, which is the lightest exotic hybrid quarkonium.

Moment Analysis of Process J/Ψ → ρηπ and 1-+ Exotic Hybrid

Does an exotic 1-+ hybrid candidate ρ̂ (1405) in the vicinity of a2 (1320) exist? It is worth to confirm this state in the process J/Ψ → ρηπ at the BEPC (Beijing Electron-Positron Collider)/BES (Beijing Spectrameter). Considering ρ̂ (1405), a2 (1320) and a0 (1450) overlap in this mass region, the three-state coupling structure mode is discussed by using the generalized moment analysis method. A series of moments for the mode and a criterion are given for confirming the exotic 1-+ hybrid.

A Study on the Search for 1-+ Exotic Hybrid in J/ψ Decay Process**The project supported by National Natural Science Foundation of China and the Grant LWTZ-1298 of the Chinese Academy of Sciences

The suggestion on the search for 1-+ exotic hybrid in a particular J/ψ decay process has been presented. We give the moment expressions for the cases of the boson resonance X with various spin-parity JP×C produced in this J/ψ decay process in terms of the generalized moment analysis method. The result shows that using these moments we can identify the 1-+ exotic hybrid produced in this kind of J/ψ decay process except for some special cases.

Recent results on light hadron and quark masses

Recent results for the spectrum of light hadrons provide clear evidence for the failure of quenched QCD and encouraging signs that simulations with dynamical sea quarks rectify some of the discrepancies, although string breaking has not yet been observed. The use of perturbation theory to match lattice quark masses to continuum schemes remains questionable, but non-perturbative methods are poised to remove this uncertainty. The inclusion of dynamical sea quarks substantially reduces estimates of the light quark masses. New results for the lightest glueball and the lightest exotic hybrid state provide useful input to phenomenology, but still have limited or no treatment of mixing. The O( a)-improved Wilson quark action is well-established in quenched QCD for β ≥ 5.7, with most parameters obtainable non-pertubatively, in which range scaling violations are small. Progress has also been made with high-order improvement schemes for both Wilson and staggered quarks.

Quantum number exotic hybrid mesons and large Nc QCD

Exotic mesons with quantum numbers of a hybrid (qqg) such as JPC=1−+are shown to exist as narrow resonant states in the large Nc limit of QCD. The width of these states is proportional to 1/Nc. Possible phenomenological implications for the world of Nc=3 are discussed.

Variability for quantitative traits in exotic hybrid germplasm of sugarcane

The foreign hybrid collection of sugarcane germplasm comprising 399 clones representing 10 geographical groups, was evaluated for nine yield and quality characters, in relation to their place of origin. Discriminant function analysis showed that all the nine variables contributed significantly to the discrimination of the groups, the maximum contribution being cane height. The overall percentage of correct classification was only 48%, with a range from 32% to 73% with respect to individual groups. This suggests an underlying genetic similarity among the groups, which stem largely from their common genetic base. The exceptions were the Hawaii and Mauritius groups, which had distinct identities. The Hawaii group was the most productive group, having maximum yield and sucrose potential. The Puerto Rico group was the best source for juice sucrose. Australian varieties bred for high juice quality did not show the expected level of juice sucrose in the present study. The use in breeding programmes of Hawaiian varieties, which have a broader genetic base and high yield and quality potential, might impart better productivity to commercial varieties.

Hybrid mesons in quenched lattice QCD

We have studied exotic hybrid mesons, made from a quark, an antiquark and gluons. Here we summarize a quenched calculation at 6/ g 2 = 5.85 and 6.15. We investigate both the light quark hybrids and the charmonium hybrids. These mesons are found to mix with four-quark states, and this mixing can be used to help in extracting masses from the propagators.

Exotic hybrid mesons with light quarks

Hybrid mesons, made from a quark, an antiquark and gluons, can have quantum numbers inaccessible to conventional quark-antiquark states. Confirmation of such states would give information on the role of “dynamical” color in low energy QCD. We present preliminary results for hybrid meson masses using light Wilson valence quarks.

Structure of Melampsora larici-populina populations on wild and cultivated poplar

Populations of Melampsora larici-populina , causal agent of poplar leaf rust, have been collected during 1992‐1994 in three types of sites: natural stands of Populus nigra in the south-east of France; cultivated poplar stands in the northern half of France, including mainly interspecific and exotic hybrids of poplar; and two overseas populations collected from Northern Ireland and Western USA. The pathotype of each rust isolate was determined by inoculating a differential set of poplar clones. The number of virulences per isolate and the frequency of each virulence in each population were compared, according to the sites and to the clones from which the isolates were collected. Several diversity indices were applied to the populations. The and Simpson indices were retained since they described best the richness and the evenness, respectively, of the populations, and they were the least sensitive to sample size. The complexity of races was lower in the natural stands of P. nigra than in the cultivated poplar stands. Populations of M. larici-populina collected on Populus euramericana ‘Robusta’ and P. nigra ‘italica’ (Lombardy poplar) presented a high richness and evenness, confirming the value of these clones for describing race populations. Populations from Western USA presented a very low diversity, which is in accordance with the recent

Breeding vandaceous orchids for commercial cut-flowers in Singapore: an overview

Extensive artificial hybridisation among members of some 86 genera of vandaceous orchids within the subtribe Sarcanthinae in Singapore over the past five decades has created many thousands of exotic hybrids. A small number of these are selected for commercial cut-flower production, while others are cultivated as pot-plants. Two classes of intergeneric hybrids are of special commercial importance as export cut-flowers, the bigeneric Aranda (Arachnis x Vanda) and the trigeneric Mokara (Arachnis x Vanda x Ascocentrum) hybrids. Cytogenetic studies of these hybrids in recent years have provided information on the significance of ploidy levels and genomic constitutions on the horticultural performance of cut-flower cultivars, and also on the strategy for effective breeding in vandaceous orchids.

Performance of Exotic × Temperate Single‐Cross Maize Hybrids

Maize (Zea mays L.) hybrids were produced by crossing exotic and temperate inbred fines. A total of 12 exotic lines, four from each of three exotic groups (Argentine flint, ETO, and Tuxpeno), were crossed with 16 temperate inbred lines, four from each of four temperate inbred groups (B37, B73, OH43, and MO17). The hybrids were evaluated in 1992 at Leesburg, GA, and Oglethorpe, GA. This study was conducted to identify superior combinations of temperate and exotic heterotic groups. Generally, hybrids with either B73‐derived or Tuxpeno lines had high yield, high grain moisture, high root lodging, and moderate stalk lodging. The B73 × Tuxpeno hybrids had the highest mean yield. Yield of B73 × exotic hybrids was not significantly different from the mean of the checks, whereas the remaining exotic‐temperate combinations had yield significantly less than the checks. Argentine flint lines combined well with B37 and B73 lines, whereas ETO lines produced high yield when crossed with B73 and OH43 lines. Overall, Tuxpeno lines demonstrated higher combining ability with temperate lines than did the Argentine flint or ETO derived lines. Results from this study suggest considerable potential for exploiting exotic germplasm to improve temperate material, especially the MO17 and OH43 derived lines.

Exotic hybrids and their non-exotic counterparts

The mass splittings and strong decays of 0−+, 1−+, 2−+ and 1−−\(q\bar qg\) hybrid mesons are considered under assumption that the state\(\hat \rho \) (1405) may be identified as 1− (1−+) hybrid. With this assumption the isoscalar partner of\(\hat \rho \) (1405) is predicted to be relatively narrow, >/s≈100–200 MeV. The large admixture of 0−+ and 2−+ hybrids may be allowed for π (1300) and π(1670) correspondingly. The data one+e− annihilation into pions around 1.5 GeV may be explained in terms of mixing of\(2^3 S_1 q\bar q\) states with 1−− isovector and isoscalar hybrids.

New limits on Primakoff production of hybrid mesons

I discuss constraints on properties of isoscalarJ PC =1−+ exotic hybrid mesons, assuming their dominant decay mode is ηπ. This work expands on a similar study by the Rochester-Minnesota-Fermilab collaboration, which excluded ϱπ as the dominant decay channel for such hybrids. The experimental limits are based on Primakoff production of such states and on a VDM argument relating their radiative widths to their ϱπ decay modes. Using data on coherent production of ηπ+ systems in π+ collisions with nuclei, I obtain few percent limits on the ϱπ branching ratios for hybrid masses ≲1.5 GeV.

Spin interactions in the flux-tube model and hybrid meson masses.

We present the results of a first exploration of meson spin interactions in the flux-tube model of Isgur and Paton. The model supports the view that long-range spin effects other than kinematical (Thomas) are small. Nonadiabatic effects somewhat enhance the long-range Thomas interaction in quark model mesons, and yield estimates for the spin splittings of the lowest hybrid mesons. We comment on the implications of these spin corrections for previous calculations of exotic hybrid decays.

Experimental constraints onJ PC=1?+,I=1, Hybrid mesons

Using data on coherent production of π+π+π- systems in π+ collisions with nuclei we exclude the existence ofJ PC=1−+,I=1, exotic hybrid mesons with masses below 1.5 GeV and widths greater than 20 MeV, provided that their primary coupling is to πρ systems. Hybrid states with just such properties have recently been predicted from arguments based on QCD sum rules. Our experimental limit is based on Primakoff production of these states, and on an argument using vector dominance to relate their radiative widths to πρ channels. There has been increasing interest of late in the existence of hybrid states, which, in the case of mesons, contain a valence gluon in addition to aq $$\bar q$$ pair in a color-octet state [1–5]. The pursuit of spectroscopic gluon degrees of freedom has been strongly motivated by the general QCD picture of hadrons, as well as by many specific calculations based on QCD sum rules, lattice simulations, and more phenomenological approaches such as QCD-bag models. Although much effort, both thoretical and experimental, has been devoted to the spectroscopy of glueballs, for which several candidates exist [6], it has also been realized that hybrid states may be as amenable to discovery, and perhaps less ambiguous to interpretation.

Gluonic excitations of mesons: Why they are missing and where to find them.

We have studied the decays of the low‐lying gluonic excitations of mesons (hybrids) predicted by a flux tube model for chromodynamics. The probable reason for the absence to data of signals for such states is immediately explained: the lowest lying hybrids decay preferentially to final states with one excited meson (e.g., B(1235)π, A2(1320)π, K*(1420)K, π(1300)π,...) rather than to two ground state mesons (e.g., ππ, ρπ, K*K,...). We make specific predictions of decay channels which will contain JPC exotic hybrid resonance signals and suggest some possibly fruitful production mechanisms.

Exotic Germplasm Use in Grain Sorghum Improvement1

Eight fertility restorer lines developed from African introductions were crossed with four male sterile lines to produce 32 hybrids. Four check hybrids were included and the 36 hybrids were evaluated for yield, seed size, seed density, and various quality characteristics. The data reported indicates that large‐seeded parents produced the highest yielding hybrids, however, all sets of exotic hybrids produced larger seed than the checks. Some exotic hybrids produced 50% more protein than the checks. Considerable variations in starch, fat and fiber showed that a great potential exists for improving the quality of grain sorghum.