2,587 research outputs found
Photoproduction of Z(4430) through mesonic Regge trajectories exchange
The recently discovered Z(4430) mesonic resonance is believed to be a strong
tetraquark candidate. The photoproduction in the channel has been proposed as the most
effective way to confirm the Z(4430) presence and to measure its quantum
numbers. In this work we present a model for high energy and forward angle
Z(4430) photoproduction in a effective Lagrangian approach. This model is based
on the use of Regge trajectories exchange, thus a Regge propagator replaces the
usual Feynman propagator. The differential and total cross sections and the
asymmetries have been calculated for the quantum numbers ,
, and in the hypotheses that Z(4430) has isospin I=1
Higher order QED in high mass e+ e- pairs production at RHIC
Lowest order and higher order QED calculations have been carried out for the
RHIC high mass e+ e- pairs observed by PHENIX with single ZDC triggers. The
lowest order QED results for the experimental acceptance are about two standard
deviations larger than the PHENIX data. Corresponding higher order QED
calculations are within one standard deviation of the data.Comment: 2 page
Impact of forestry practices on fitness correlates and population productivity in an open-nesting bird species
In the boreal forests of Fennoscandia, over 99% of the forest area has been altered by forestry practices, which has created forests of differing age structures and stand characteristics than primary forest stands. Although many researchers have investigated how forestry affects species abundance, few have assessed how forestry affects fitness correlates of species living in altered habitats, and this has negatively affected management efforts. We experimentally addressed the effect of standard forestry practices on fitness correlates of an open-nesting, long-lived bird species typical to boreal forests of Eurasia, the Siberian Jay (Perisoreus infaustus L.). Using a before-after comparison of reproductive data on the level of territories, we found that standard forestry practices had a strong negative effect on the breeding success of jays. Both partial thinning of territories and partial clearcutting of territories reduced future breeding success by a factor of 0.35. Forestry practices reduced territory occupancy. Thus, over the 15 years of the study the productivity of the affected population declined over 50% as a result of territory abandonment and reduced breeding success. Results of previous studies on Siberian Jays suggest that the strong effect of forest thinning on fitness is explained by the fact that most common predators of nests and adults are visually oriented, and thinning makes prey and nests more visible to predators. The consequences of thinning we observed are likely to apply to a wide range of species that rely on understory to provide visual protection from predators. Thus, our results are important for the development of effective conservation management protocols and for the refinement of thinning practices
Aspects of Coulomb Dissociation and Interference in Peripheral Nucleus-Nucleus Collisions
Coherent vector meson production in peripheral nucleus-nucleus collisions is
discussed. These interactions may occur for impact parameters much larger than
the sum of the nuclear radii. Since the vector meson production is always
localized to one of the nuclei, the system acts as a two-source interferometer
in the transverse plane. By tagging the outgoing nuclei for Coulomb
dissociation it is possible to obtain a measure of the impact parameter and
thus the source separation in the interferometer. This is of particular
interest since the life-time of the vector mesons are generally much shorter
than the impact parameters of the collisions.Comment: 10 pages, 4 figures, Presented at the Workshop on Electromagnetic
Probes of Fundamental Physics, Erice, Italy, 16-21 October, 200
Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions
Highly charged relativistic heavy ions have high cross-sections for
two-photon interactions. The photon flux is high enough that two-photon
interactions may be accompanied by additional photonuclear interactions. Except
for the shared impact parameter, these interactions are independent. Additional
interactions like mutual Coulomb excitation are of experimental interest, since
the neutrons from the nuclear dissociation provide a simple, relatively
unbiased trigger.
We calculate the cross sections, rapidity, mass and transverse momentum
( distributions for exclusive production of mesons and
lepton pairs, and for reactions accompanied by mutual Coulomb
dissociation. The cross-sections for interactions accompanied by
multiple neutron emission () and single neutron emission () are
about 1/10 and 1/100 of that for the unaccompanied interactions.
We discuss the accuracy with which these cross-sections may be calculated. The
typical of final states is several times smaller than for
comparable coherent photonuclear interactions, so may be an effective
tool for separating the two classes of interactions.Comment: 17 pages, 12 figure
Interference in Exclusive Vector Meson Production in Heavy Ion Collisions
Photons emitted from the electromagnetic fields of relativistic heavy ions
can fluctuate into quark anti-quark pairs and scatter from a target nucleus,
emerging as vector mesons. These coherent interactions are identifiable by
final states consisting of the two nuclei and a vector meson with a small
transverse momentum. The emitters and targets can switch roles, and the two
possibilities are indistinguishable, so interference may occur. Vector mesons
are negative parity so the amplitudes have opposite signs. When the meson
transverse wavelength is larger than the impact parameter, the interference is
large and destructive.
The short-lived vector mesons decay before amplitudes from the two sources
can overlap, and so cannot interfere directly. However, the decay products are
emitted in an entangled state, and the interference depends on observing the
complete final state. The non-local wave function is an example of the
Einstein-Podolsky-Rosen paradox.Comment: 13 pages with 3 figures; submitted to Physical Review Letter
Photoproduction of Quarkonium in Proton-Proton and Nucleus-Nucleus Collisions
We discuss the photoproduction of and at high energy
, and heavy ion colliders. We predict large rates in
interactions at the Fermilab Tevatron %and in heavy-ion interactions at the
CERN LHC. These reactions can be and in and heavy-ion interactions at the
CERN LHC. The is also produced copiously at RHIC. These reactions can
be used to study the gluon distribution in protons and heavy nuclei. We also
show that the different CP symmetries of the initial states lead to large
differences in the transverse momentum spectra of mesonsComment: 4 pgs. with 3 figure
PHENIX measurement of jet properties and their modification in heavy-ion collisions
The properties of jets produced in p+p, d+Au and Au+Au collisions at
sqrt{s_NN}=200 GeV are studied using the method of two particle correlations.
The trigger particle is assumed to be a leading particle from a high p_T jet
while the associated particle is assumed to come from either the same jet or
the away jet. From the angular width and yield of the same and away side
correlation peaks, the parameters characterizing the jet properties are
extracted.Comment: 4 pages, 3 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
Traces of Thermalization from Transverse Momentum Fluctuations in Nuclear Collisions
Scattering of particles produced in Au+Au collisions at RHIC can wrestle the
system into a state near local thermal equilibrium. I illustrate how
measurements of the centrality dependence of the mean transverse momentum and
its fluctuations can exhibit this thermalization.Comment: 4 pages, 2 eps figures, final version to appear in PR
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