11 research outputs found
Search for the K with PHENIX
The PHENIX experiment at RHIC should be sensitive to decays of the the
anti--pentaquark via the K channel. Charged
kaons can be identified using the standard tracking and time of flight up to a
momentum of 1.5 GeV/c. Anti--neutron candidates are detected via their
annihilation signal in the highly segmented electromagnetic calorimeter
(EMCal). In order to assess the quality of the anti--neutron identification we
reconstruct the . As an additional crosscheck the
invariant mass of K is reconstructed where no resonance in the
pentaquark mass range is expected. At the present time no enhancement at the
expected pentaquark mass is observed in dAu collisions at $\sqrt{s_{NN}} = 200
GeV.Comment: 4 pages 5 figures contribution to the proceedings of the 17th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings
(Journal of Physics G
1/N Expansion for Exotic Baryons
The 1/N expansion for exotic baryons is developed, and applied to the masses,
meson couplings and decay widths. Masses and widths of the 27 and 35 pentaquark
states in the same tower as the Theta+ are related by spin-flavor symmetry. The
27 and 35 states can decay within the pentaquark tower, as well as to normal
baryons, and so have larger decay widths than the lightest pentaquark Theta.
The 1/N expansion also is applied to baryon exotics containing a single heavy
antiquark. The decay widths of heavy pentaquarks via pion emission, and to
normal baryons plus heavy D^(*),B^(*) mesons are studied, and relations
following from large-N spin-flavor symmetry and from heavy quark symmetry are
derived.Comment: Major additions: plots of widths and branching ratios, discussion of
strong decays of heavy pentaquarks, including consequences of heavy quark
symmetr
High precision measurement of the associated strangeness production in proton proton interactions
A new high precision measurement of the reaction pp -> pK+Lambda at a beam
momentum of 2.95 GeV/c with more than 200,000 analyzed events allows a detailed
analysis of differential observables and their inter-dependencies. Correlations
of the angular distributions with momenta are examined. The invariant mass
distributions are compared for different regions in the Dalitz plots. The cusp
structure at the N Sigma threshold is described with the Flatt\'e formalism and
its variation in the Dalitz plot is analyzed.Comment: accepted for publication in Eur. Phys. J.
First Model-Independent Measurement of the Spin Triplet Scattering Length from Final State Interaction in the Reaction
The reaction has been measured with the
COSY-TOF detector at a beam momentum of . The polarized
proton beam enables the measurement of the beam analyzing power by the
asymmetry of the produced kaon (). This observable allows the
spin triplet scattering length to be extracted for the first time
model independently from the final-state interaction in the reaction. The
obtained value is . This value is
compatible with theoretical predictions and results from model-dependent
analyses.Comment: Revised version as accepted for publication in PR
Chiral perturbation theory calculation for pn -> dpipi at threshold
We investigate the reaction pn -> dpipi in the framework of Chiral
Perturbation Theory. For the first time a complete calculation of the leading
order contributions is presented. We identify various diagrams that are of
equal importance as compared to those recognized in earlier works. The diagrams
at leading order behave as expected by the power counting. Also for the first
time the nucleon-nucleon interaction in the initial, intermediate and final
state is included consistently and found to be very important. This study
provides a theoretical basis for a controlled evaluation of the non-resonant
contributions in two-pion production reactions in nucleon-nucleon collisions.Comment: 24 pages, 3 figures, 3 table
Determination of the Spin Triplet p\Lambda Scattering Length from the Reaction pp -> pK\Lambda
Measurement of polarization observables of the associated strangeness production in proton proton interactions
The Λ polarization, the analyzing power, and the Λ spin transfer coefficient of the reaction pp→pK+Λ were measured at beam momenta of 2.70GeV/c and 2.95GeV/c corresponding to excess energies of 122MeV and 204MeV. While the analyzing power and the spin transfer coefficient do not change significantly with the excess energy, the Λ polarization varies strongly and changes its sign. As this is the first measurement of polarization observables below an excess energy of 200MeV, the change of the sign of the Λ polarization was not observed before. The high statistics of the data ( ≈ 200 k events for each momentum) enables detailed studies of the dependence of the Λ polarization and the analyzing power on the center-of-mass momentum of the particles. The results of the spin transfer coefficient are in qualitative agreement with the DISTO experiment. The Λ polarization data of 2.95GeV/c are only conform with the DISTO experiment, while both the 2.70GeV/c and 2.95GeV/c data differ strongly from all previous measurements, whether exclusive or inclusive