1,126 research outputs found
Indication for scattering in collisions at 200 GeV
A mass shift of about -40 MeV/ was measured in
collisions at 200 GeV at RHIC. Previous mass shifts have
been observed at CERN-LEBC-EHS and CERN-LEP. We will show that phase space does
not account for the mass shift measured at RHIC, CERN-LEBC-EHS
and CERN-LEP and conclude that there are significant scattering interactions in
collisions.Comment: 11 pages and 7 figure
Production in Au+Au and pp Collisions at = 200GeV at STAR
Mid-rapidity and are
measured in Au+Au and pp collisions at =200GeV using the STAR
detector at RHIC. The mass is systematically shifted at small
transverse momentum for both Au+Au and pp collisions. The
transverse mass spectra are measured in Au+Au collisions at different
centralities and in pp collisions. The mean transverse momentum
as a function of the collision centrality is compared to those of identified
, and . The and ratios are
compared to measurements in A+A, , , collisions at
various colliding energies. The physics implications of these measurements are
also discussed.Comment: 6 pages, 4 figures, proceedings of Strange Quarks in Matter
(SQM2003), Atlantic Beach, USA, to be published in J. Phys.
On Deusons or Deuteronlike Meson-Meson Bound States
The systematics of deuteronlike two-meson bound states, {\it deusons}, is
discussed. Previous arguments that many of the present non- states are
such states are elaborated including, in particular, the tensor potential. For
pseudoscalar states the important observation is made that the centrifugal
barrier from the P-wave can be overcome by the and terms of the
tensor potential. In the heavy meson sector one-pion exchange alone is strong
enough to form at least deuteron-like and composites
bound by approximately 50 MeV, while and states are
expected near the threshold.Comment: Invited talk at the Hadron93 International Conf. on Hadron
Spectroscopy, Como, Italy 22.-25.6. 1993. 5 pages in LATEX HU-SEFT R 1993-13
Observing Spontaneous Strong Parity Violation in Heavy-Ion Collisions
We discuss the problem of observing spontaneous parity and CP violation in
collision systems. We discuss and propose observables which may be used in
heavy-ion collisions to observe such violations, as well as event-by-event
methods to analyze the data. Finally, we discuss simple monte-carlo models of
these CP violating effects which we have used to develop our techniques and
from which we derive rough estimates of sensitivities to signals which may be
seen at RHIC
, K and f Production in Au-Au and pp Collisions at = 200 GeV
Preliminary results on , KK and production using the mixed-event
technique are presented. The measurements are performed at mid-rapidity by the
STAR detector in = 200 GeV Au-Au and pp interactions at RHIC.
The results are compared to different measurements at various energies.Comment: 4 pages, 6 figures. Talk presented at Quark Matter 2002, Nantes,
France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A
Neutron Star Constraints on the H Dibaryon
We study the influence of a possible H dibaryon condensate on the equation of
state and the overall properties of neutron stars whose population otherwise
contains nucleons and hyperons. In particular, we are interested in the
question of whether neutron stars and their masses can be used to say anything
about the existence and properties of the H dibaryon. We find that the equation
of state is softened by the appearance of a dibaryon condensate and can result
in a mass plateau for neutron stars. If the limiting neutron star mass is about
that of the Hulse-Taylor pulsar a condensate of H dibaryons of vacuum mass 2.2
GeV and a moderately attractive potential in the medium could not be ruled out.
On the other hand, if the medium potential were even moderately repulsive, the
H, would not likely exist in neutron stars. If neutron stars of about 1.6 solar
mass were known to exist, attractive medium effects for the H could be ruled
out. Certain ranges of dibaryon mass and potential can be excluded by the mass
of the Hulse-Taylor pulsar which we illustrate graphically.Comment: Revised by the addition of a figure showing the region of dibaryon
mass and potential excluded by the Hulse-Taylor pulsar. 18 pages, 11 figures,
latex (submitted to Phys. Rev. C
The moral journey of learning a pedagogy: a qualitative exploration of student–teachers’ formal and informal writing of dialogic pedagogy
YesStudents of education encounter a range of pedagogies yet how future teachers’ appropriate moral principles are little understood. We conducted an investigation into this process with 10 international students of education attending an intensive course on ‘dialogic pedagogy’ in a university in Finland. The data comprising student learning journals and essays were coded for the level of questioning, acceptance and irreverence. In the findings, reverential acceptance was more frequent than questioning and irreverence; however, our qualitative analysis also found a large number of micro-transitions between questioning, acceptance and irreverence suggesting a dynamic interplay. Recognising this vacillation as part of a moral journey may support better understanding of what it means to engage with a different pedagogy
Can Doubly Strange Dibaryon Resonances be Discovered at RHIC?
The baryon-baryon continuum invariant mass spectrum generated from
relativistic nucleus + nucleus collision data may reveal the existence of
doubly-strange dibaryons not stable against strong decay if they lie within a
few MeV of threshold. Furthermore, since the dominant component of these states
is a superposition of two color-octet clusters which can be produced
intermediately in a color-deconfined quark-gluon plasma (QGP), an enhanced
production of dibaryon resonances could be a signal of QGP formation. A total
of eight, doubly-strange dibaryon states are considered for experimental search
using the STAR detector (Solenoidal Tracker at RHIC) at the new Relativistic
Heavy Ion Collider (RHIC). These states may decay to Lambda-Lambda and/or
proton-Cascade-minus, depending on the resonance energy. STAR's large
acceptance, precision tracking and vertex reconstruction capabilities, and
large data volume capacity, make it an ideal instrument to use for such a
search. Detector performance and analysis sensitivity are studied as a function
of resonance production rate and width for one particular dibaryon which can
directly strong decay to proton-Cascade-minus but not Lambda-Lambda. Results
indicate that such resonances may be discovered using STAR if the resonance
production rates are comparable to coalescence model predictions for dibaryon
bound states.Comment: 28 pages, 5 figures, revised versio
e^+e^- Pair Production from A Reactions
We present a calculation of e^+e^- production in reactions at MAMI
and TJNAF energies within a semi-classical BUU transport model. Dilepton
invariant mass spectra for C, Ca and Pb are calculated
at 0.8, 1.5 and 2.2 GeV. We focus on observable effects of medium modifications
of the and mesons. The in-medium widths of these mesons are
taken into account in a dynamical, consistent way. We discuss the transport
theoretical treatment of broad resonances.Comment: 42 pages including 16 figure
Strangeness Enhancement in and Interactions at SPS Energies
The systematics of strangeness enhancement is calculated using the HIJING and
VENUS models and compared to recent data on , and
collisions at CERN/SPS energies (). The HIJING model is used to
perform a {\em linear} extrapolation from to . VENUS is used to
estimate the effects of final state cascading and possible non-conventional
production mechanisms. This comparison shows that the large enhancement of
strangeness observed in collisions, interpreted previously as possible
evidence for quark-gluon plasma formation, has its origins in non-equilibrium
dynamics of few nucleon systems. % Strangeness enhancement %is therefore traced
back to the change in the production dynamics %from to minimum bias
and central collisions. A factor of two enhancement of at
mid-rapidity is indicated by recent data, where on the average {\em one}
projectile nucleon interacts with only {\em two} target nucleons. There appears
to be another factor of two enhancement in the light ion reaction relative
to , when on the average only two projectile nucleons interact with two
target ones.Comment: 29 pages, 8 figures in uuencoded postscript fil
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