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, Volume:
93, Issue:
21
Journal Article
Peer reviewed
Open access
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, Volume:
758, Issue:
C
Journal Article
Peer reviewed
Open access
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.
A model of pentaquarks Germani, D.; Niliani, F.; Polosa, A. D.
The European physical journal. C, Particles and fields,
29/7, Volume:
84, Issue:
7
Journal Article
Peer reviewed
Open access
We describe pentaquarks as ‘baryo-charmonia’ with a color octet
c
c
¯
core bonded to a color octet three-quark system. Fermi statistics of the light quark cloud allows to describe two pentaquark ...triplets: a lower one, well supported by experiment, and a higher one with strangeness. For the time being, the lowest line of the strange triplet has been experimentally identified in a
3
σ
peak. Data also suggest two different production mechanisms for pentaquarks. We show how this can be described in the proposed scheme.
A note on polarized light from magnetars Capparelli, L. M.; Damiano, A.; Maiani, L. ...
European physical journal. C, Particles and fields,
11/2017, Volume:
77, Issue:
11
Journal Article
Peer reviewed
Open access
In a recent paper it is claimed that vacuum birefringence has been experimentally observed for the first time by measuring the degree of polarization of visible light from a magnetar candidate, a ...neutron star with a magnetic field presumably as large as
B
∼
10
13
G
. The role of such a strong magnetic field is twofold. First, the surface of the star emits, at each point, polarized light with linear polarization correlated with the orientation of the magnetic field. Depending on the relative orientation of the magnetic axis of the star with the direction to the distant observer, a certain degree of polarization should be visible. Second, the strong magnetic field in the vacuum surrounding the star could enhance the effective degree of polarization observed: vacuum birefringence. We compare experimental data and theoretical expectations concluding that the conditions to support a claim of
strong
evidence of vacuum birefringence effects are not met.
PDF
