309 research outputs found
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.
Decays of Pentaquarks in Hadrocharmonium and Molecular Scenarios
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 ψ′ 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
Narrow Nucleon-\u3cem\u3eψ\u3c/em\u3e(2\u3cem\u3eS\u3c/em\u3e) Bound State and LHCb Pentaquarks
We interpret the newly discovered pentaquark Pc(4450) as a bound state of charmonium ψ(2S) and the nucleon. The binding potential is due to the charmonium-nucleon interaction that in the heavy quark approximation is proportional to the product of the charmonium chromoelectric polarizability and the nucleon energy-momentum distribution. We use the large Nc expansion to estimate the quarkonium polarizability and calculate the nucleon properties in the framework of the mean-field picture of light baryons. Two almost degenerate states JP=(1/2)− and JP=(3/2)− are predicted at the position of the Pc(4450) pentaquark. We find that the nucleon-ψ(2S) bound state has a naturally narrow width in the range of tens of MeV. The unitary multiplet partners of the Pc(4450) pentaquark and the generalization to bb¯-nucleon pentaquark bound states are discussed
An improvement of the Berry--Esseen inequality with applications to Poisson and mixed Poisson random sums
By a modification of the method that was applied in (Korolev and Shevtsova,
2009), here the inequalities
and
are proved for the
uniform distance between the standard normal distribution
function and the distribution function of the normalized sum of an
arbitrary number of independent identically distributed random
variables with zero mean, unit variance and finite third absolute moment
. The first of these inequalities sharpens the best known version of
the classical Berry--Esseen inequality since
by virtue of
the condition , and 0.4785 is the best known upper estimate of the
absolute constant in the classical Berry--Esseen inequality. The second
inequality is applied to lowering the upper estimate of the absolute constant
in the analog of the Berry--Esseen inequality for Poisson random sums to 0.3051
which is strictly less than the least possible value of the absolute constant
in the classical Berry--Esseen inequality. As a corollary, the estimates of the
rate of convergence in limit theorems for compound mixed Poisson distributions
are refined.Comment: 33 page
The low energy limit of the non-commutative Wess-Zumino model
The non-commutative Wess-Zumino model is used as a prototype for studying the
low energy behaviour of a renormalizable non-commutative field theory. We start
by deriving the potential mediating the fermion-fermion and boson-boson
interactions in the non-relativistic regime. The quantum counterparts of these
potentials are afflicted by irdering ambiguities but we show that there exists
an ordering prescription which makes them hermitean. For space/space
noncommutativity it turns out that Majorana fermions may be pictured as rods
oriented perpendicularly to the direction of motion showing a lack of
localituy, while bosons remain insensitive to the effects of noncommutativity.
For time/space noncommutativity bosopns and fermions can be regarded as rods
oriented along the direction of motion. For both cases of noncommutativity the
scattering state described scattered waves, with at least one wave having
negative time delay signalizing the underlying nonlocality. The superfield
formulation of the model is used to compute the corresponding effective action
in the one- and two-loop approximations. In the case of time/space
noncommutativity, unitarity is violated in the relativistic regime. However,
this does not preclude the existence of the unitary low energy limit.Comment: 14 pages, 2 figures, minor correction
Application of the Large-N_c limit to a Chiral Lagrangian with Resonances
It is shown that the implementation of the Large-- approximation helps
to get insight into the structure of, in principle, any QCD-like theory. As an
example, we will compute the NLO corrections to in the chiral limit
with a Lagrangian with Resonances.Comment: 9 pages, 1 figure. Talk given at the International School of
Subnuclear Physics (Erice 2002). To be published in the Proceeding
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Brain Genomics Superstruct Project initial data release with structural, functional, and behavioral measures
The goal of the Brain Genomics Superstruct Project (GSP) is to enable large-scale exploration of the links between brain function, behavior, and ultimately genetic variation. To provide the broader scientific community data to probe these associations, a repository of structural and functional magnetic resonance imaging (MRI) scans linked to genetic information was constructed from a sample of healthy individuals. The initial release, detailed in the present manuscript, encompasses quality screened cross-sectional data from 1,570 participants ages 18 to 35 years who were scanned with MRI and completed demographic and health questionnaires. Personality and cognitive measures were obtained on a subset of participants. Each dataset contains a T1-weighted structural MRI scan and either one (n=1,570) or two (n=1,139) resting state functional MRI scans. Test-retest reliability datasets are included from 69 participants scanned within six months of their initial visit. For the majority of participants self-report behavioral and cognitive measures are included (n=926 and n=892 respectively). Analyses of data quality, structure, function, personality, and cognition are presented to demonstrate the dataset’s utility
An upper limit to the photon fraction in cosmic rays above 10^19 eV from the Pierre Auger Observatory
An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies above 10^19 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample, support the conclusion that a photon origin of the observed events is not favoured
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