8,173 research outputs found
On quantum model of supergravity compensator
A new superfield model in flat superspace is suggested. This
model describes dynamics of chiral compensator and can be treated as a
low-energy limit of , quantum superfield supergravity.
Renormalization structure of this model is studied and one-loop counterterms
are calculated. It is shown that the theory is infrared free. An effective
action for the model under consideration is investigated in infrared domain.
The lower contributions to the one-loop effective action are computed in
explicit form.Comment: LaTeX, 9 page
Decays of Pentaquarks in Hadrocharmonium and Molecular Pictures
We consider decays of the hidden charm LHCb pentaquarks in the
hadrocharmonium and molecular scenarios. In both pictures the LHCb pentaquarks
are essentially nonrelativistic bound states. We develop a semirelativistic
framework for calculation of the partial decay widths that allows the final
particles to be relativistic. Using this approach we calculate the decay widths
in the hadrocharmonium and molecular pictures. Molecular hidden charm
pentaquarks are constructed as loosely bound states of charmed and anticharmed
hadrons. Calculations show that molecular pentaquarks decay predominantly into
states with open charm. Strong suppression of the molecular pentaquark decays
into states with hidden charm is qualitatively explained by a relatively large
size of the molecular pentaquark. The decay pattern of hadrocharmonium
pentaquarks that are interpreted as loosely bound states of excited charmonium
and nucleons is quite different. This time dominate decays into states
with hidden charm, but suppression of the decays with charm exchange is weaker
than in the respective molecular case. The weaker suppression is explained by a
larger binding energy and respectively smaller size of the hadrocharmonium
pentaquarks. These results combined with the experimental data on partial decay
widths could allow to figure out which of the two theoretical scenarios for
pentaquarks (if either) is chosen by nature.Comment: 33 pages, 14 figures; v2: minor editorial changes, version published
in Phys. Rev.
New LHCb pentaquarks as hadrocharmonium states
New LHCb Collaboration results on pentaquarks with hidden charm [1] are
discussed. These results fit nicely in the hadrocharmonium pentaquark scenario
[2,3]. In the new data the old LHCb pentaquark splits into two
states and . We interpret these two almost degenerate
hadrocharmonium states with and as a result of
hyperfine splitting between hadrocharmonium states predicted in [2]. It arises
due to QCD multipole interaction between color-singlet hadrocharmonium
constituents. We improve the theoretical estimate of hyperfine splitting [2,3]
that is compatible with the experimental data. The new state finds
a natural explanation as a bound state of and a nucleon, with
, and binding energy 42 MeV. As a bound state of a spin-zero
meson and a nucleon, hadrocharmonium pentaquark does not experience
hyperfine splitting. We find a series of hadrocharmonium states in the vicinity
of the wide pentaquark that can explain its apparently large decay
width. We compare the hadrocharmonium and molecular pentaquark scenarios and
discuss their relative advantages and drawbacks.Comment: 10 page
Pentaquarks with hidden charm as hadroquarkonia
We consider hidden charm pentaquarks as hadroquarkonium states in a QCD
inspired approach. Pentaquarks arise naturally as bound states of quarkonia
excitations and ordinary baryons. The LHCb pentaquark is
interpreted as a -nucleon bound state with spin-parity . The
partial decay width MeV is calculated
and turned out to be in agreement with the experimental data for .
The pentaquark is predicted to be a member of one of the two almost
degenerate hidden-charm baryon octets with spin-parities .
The masses and decay widths of the octet pentaquarks are calculated. The widths
are small and comparable with the width of the pentaquark, and the
masses of the octet pentaquarks satisfy the Gell-Mann-Okubo relation.
Interpretation of pentaquarks as loosely bound and
deuteronlike states is also considered. We determine
quantum numbers of these bound states and calculate their masses in the
one-pion exchange scenario. The hadroquarkonium and molecular approaches to
exotic hadrons are compared and the relative advantages and drawbacks of each
approach are discussed.Comment: 33 pages, 2 figures, 3, tables; Minor changes, 2 references added;
Version published in Eur. Phys. J.
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