52 research outputs found
Heavier Higgs Particles: Indications from Minimal Supersymmetry
We use the most recent data on the Higgs-like resonance h observed at 125 GeV
to derive information about the mass of the heavier Higgs particles predicted
by Minimal Supersymmetry. We treat as independent parameters the couplings of h
to top quark, beauty and massive vector bosons and, in this three dimensional
space, we locate the point realizing the best fit to data and compare it to the
position of the Standard Model point and to the region of coupling values
accommodating heavier Higgs particles in Minimal Supersymmetry. We conclude
that mass values 320< M_H< 360 GeV are compatible at 2sigma with the best fit
of couplings to present data, larger values being compatible at the 1sigma
level. Values of 1< tan(beta)< 6 are compatible with data.Comment: 5 pages, 5 figures. Clarifications and new references adde
The New Pentaquarks in the Diquark Model
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.Comment: 4 pages, 1 figure, to appear in PL
A Theory of X and Z Multiquark Resonances
We introduce the hypothesis that diquarks and antidiquarks in tetraquarks are
separated by a potential barrier. We show that this notion can answer
satisfactorily long standing questions challenging the diquark-antidiquark
model of exotic resonances. The tetraquark description of X and Z resonances is
shown to be compatible with present limits on the non-observation of charged
partners X^+-, of the X(3872) and the absence of a hyperfine splitting between
two different neutral states. In the same picture, Z_c and Z_b particles are
expected to form complete isospin triplets plus singlets. It is also explained
why the decay rate into final states including quarkonia are suppressed with
respect to those having open charm/beauty states.Comment: 6 pages, 2 figures, some points clarified. To appear in PL
Neutron Production Rates by Inverse-Beta Decay in Fully Ionized Plasmas
Recently we showed that the nuclear transmutation rates are largely
overestimated in the Widom-Larsen theory of the so called `Low Energy Nuclear
Reactions'. Here we show that unbound plasma electrons are even less likely to
initiate nuclear transmutations.Comment: 9 pages, 1 Figure, minor revisions and clarifications, results
unchanged. To appear in EPJ
The Hydrogen Bond of QCD
Using the Born-Oppenheimer approximation, we show that exotic resonances, X
and Z, may emerge as QCD molecular objects made of colored two-quark lumps,
states with heavy-light diquarks spatially separated from antidiquarks. With
the same method we confirm that doubly heavy tetraquarks are stable against
strong decays. Tetraquarks described here provide a new picture of exotic
hadrons, as formed by the QCD analog of the hydrogen bond of molecular physics.Comment: 5 pages, 3 figures, comments and references added. Table 1 extende
Indications of a Four-Quark Structure for the X(3872) and X(3876) Particles from Recent Belle and BABAR Data
Recent results by BELLE and BaBar point to the existence of a second X
particle decaying in D^0 D^0bar pi^0, a few MeV above the X(3872). We identify
the two X states with the neutral particles predicted by the 4-quark model and
show that production and decays are consistent with this assignement. We
consider the yet-to-be-observed charged partners and give new hints on how to
look for them.Comment: 5 pages, some revision of the text, results unchanged. To appear in
Phys. Rev. Let
From Pentaquarks to Dibaryons in Lambda_b(5620) decays
Pentaquarks and dibaryons are natural possibilities if diquarks are used as
the building blocks to assemble hadrons. In this short note, motivated by the
very recent discovery of two pentaquark states, we highlight some possible
channels to search for dibaryons in Lambda_b(5620) decays.Comment: 2 pages, references added, minor modifications, to appear in Phys.
Lett.
Hidden-Beauty Charged Tetraquarks and Heavy Quark Spin Conservation
Assuming the dominance of the spin-spin interaction in a diquark, we point
out that the mass difference in the beauty sector M(Z_b^prime) - M(Z_b) scales
with quark masses as expected in QCD, with respect to the corresponding mass
difference M(Z_c^prime) - M(Z_c). Notably, we show that the decays
Upsilon(10890) --> Upsilon(nS) pi pi and Upsilon(10890) --> (h_b(1P), h_b(2P))
pi pi are compatible with heavy-quark spin conservation if the contributions of
Z_b,Z_b^prime intermediate states are taken into account, Upsilon(10890) being
either a Upsilon(5S) or the beauty analog of Y_c(4260). Belle results on these
decays support the quark spin wave-function of the Z states as tetraquarks. We
also consider the role of light quark spin non-conservaton in Z_b,Z_b^prime
decays into B B^* and B^* B^*. Indications of possible signatures of the still
missing X_b resonance are proposed.Comment: 5 pages, comments added, to appear in Phys Rev
The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
Following the recent confirmation of the Z+(4430) resonance with
J^{PG}=1^{++}, we have re-examined the model of S- and P-wave tetraquarks. We
propose a `type-II' diquark-antidiquark model which shows to be very effective
at producing a simple and comprehensive picture of the J^{PG}=1^{++} and 1^{--}
sectors of the recently discovered charged tetraquarks and of the observed Y
resonances. The model is still faced with the unresolved difficulty of
explaining why some states seem to have incomplete isospin multiplets.Comment: 17 pages, 1 figure, comments added, typos corrected, to appear in
Phys Rev
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