We suggest that the J/ψϕ structures observed by LHCb can be fitted in two tetraquak multiplets, the S-wave ground state and the first radial excitation, with composition csc¯s¯. When compared to the ...previously identified cqc¯q¯ multiplet, the observed masses agree with that expected for a multiplet with q→s. We propose the X(4274), fitted by LHCb with a single 1++ resonance, to correspond rather to two, almost degenerate, unresolved lines with JPC=0++,2++. Masses of missing particles in the 1S and 2S multiplets are predicted.
Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of ...two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.
New look at scalar mesons MAIANI, L; PICCININI, F; POLOSA, A. D ...
Physical review letters,
11/2004, Letnik:
93, Številka:
21
Journal Article
Recenzirano
Odprti dostop
Light scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulas which respect, to a good extent, the Okubo-Zweig-Iizuka (OZI) rule. OZI ...allowed strong decays are reasonably reproduced by a single amplitude describing the switch of a qq pair, which transforms the state into two colorless pseudoscalar mesons. Predicted heavy states with one or more quarks replaced by charm or beauty are briefly described; they should give rise to narrow states with exotic quantum numbers.
A
bstract
Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate ...states in non-planar diagrams of the 1
/N
expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained.
Pentaquark baryons are a natural expectation of an extended picture of hadrons where quarks and diquarks are the fundamental units. The parity/mass pattern observed, when compared to that of exotic ...mesons, appears as the footprint of a compact five-quark structure. What has been learned from the X, Y, Z phenomenology informs about the newly found pentaquark structure and suggests further experimental tests and directions to be explored.
We update our analysis of the Higgs sector masses in minimal supersymmetry and in the Two Higgs Doublet Model to the final ATLAS and CMS data from the 2011–2012 LHC run.
Hybridized tetraquarks Esposito, A.; Pilloni, A.; Polosa, A.D.
Physics letters. B,
07/2016, Letnik:
758, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We propose a new interpretation of the neutral and charged X,Z exotic hadron resonances. Hybridized-tetraquarks are neither purely compact tetraquark states nor bound or loosely bound molecules but ...rather a manifestation of the interplay between the two. While meson molecules need a negative or zero binding energy, its counterpart for h-tetraquarks is required to be positive. The formation mechanism of this new class of hadrons is inspired by that of Feshbach metastable states in atomic physics. The recent claim of an exotic resonance in the Bs0π± channel by the D0 Collaboration and the negative result presented subsequently by the LHCb Collaboration are understood in this scheme, together with a considerable portion of available data on X,Z particles. Considerations on a state with the same quantum numbers as the X(5568) are also made.
Directional detection of Dark Matter particles (DM) in the MeV mass range could be accomplished by studying electron recoils in large arrays of parallel carbon nanotubes. In a scattering process with ...a lattice electron, a DM particle might transfer sufficient energy to eject it from the nanotube surface. An external electric field is added to drive the electron from the open ends of the array to the detection region. The anisotropic response of this detection scheme, as a function of the orientation of the target with respect to the DM wind, is calculated, and it is concluded that no direct measurement of the electron ejection angle is needed to explore significant regions of the light DM exclusion plot. A compact sensor, in which the cathode element is substituted with a dense array of parallel carbon nanotubes, could serve as the basic detection unit.
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a ...WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (
≈
11
GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.
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