4,292 research outputs found
Interpenetrated networks from a novel nanometer-sized pseudopeptidic ligand, bridging water, and transition metal ions with CdSO4 topology.
The combination of a new pseudopeptidic ligand, transition
metal ions, and bridging water molecules results in the
formation of [M(m-TBG)(m-H2O)(H2O)2]?2H2O (M: Cu, Co
and H2TBG: terephthaloylbisglycine); both compounds show
rare two-fold interpenetrated three-dimensional cds-nets and
reversible loss of coordinated and lattice water molecule
Color Octet Contribution to High p_T J/\Psi Production in pp Collisions at \sqrt s = 500 and 200 GeV at RHIC
We compute \frac{d\sigma}{dp_T} of the J/\psi production in pp collisions at
RHIC at \sqrt s = 500 and 200 GeV by using both the color octet and singlet
models in the framework of non-relativistic QCD. The J/\psi we compute here
includes the direct J/\psi from the partonic fusion processes and the J/\psi
coming from the radiative decays of \chi_J's both in the color octet and
singlet channel. The high p_T J/\psi production cross section is computed
within the PHENIX detector acceptance ranges: -0.35 < \eta < 0.35 and 1.2 <
\|\eta| < 2.4, the central electron and forward muon arms. It is found that the
color octet contribution to J/\psi production is dominant at RHIC energy in
comparison to the color singlet contributions. We compare our results with the
recent preliminary data obtained by PHENIX detector for the high p_T J/\psi
measurements. While the color singlet model fails to explain the data
completely the color octet model is in agreement with the single data point
above 2 GeV transverse momentum. A measurement of J/\psi production at RHIC in
the next run with better statistics will allow us to determine the validity of
the color octet model of J/\psi production at RHIC energies. This is very
important because it is necessary to know the exact mechanism for J/\psi
production in pp collisions at RHIC if one is to make predictions of J/\psi
suppression as a signature of quark-gluon plasma. These mechanisms also play an
important role in determining the polarized spin structure function of the
proton at RHIC.Comment: 16 pages latex, 6 figure
The position of the mental foramen in dentate and edentulous mandibles: clinical and surgical relevance
Background: The knowledge of the exact location of the mental foramen (MF) in dentate and edentulous mandibles is clinically important when constructing complete dentures, performing anaesthetic block of the lower-anterior teeth area and intervening in the MF nearby area. In edentulous mandibles, the bone resorption after teeth loss makes the mental nerve (MN) prone to damage due to the extreme location of the MF very close to the alveolar crest (AC). Chronic compression on the MN may result in pain in the area of MN distribution (ipsilateral face and cheek area) and numbness at the lower lip. The purpose of the current study is to evaluate the exact position of the MF, calculating the distances MF-superior border of the AC and MF-inferior border of the mandible (IBM) in dentate and edentulous mandibles.
Materials and methods: One hundred and two (36 edentulous and 66 dentate) adult dry Greek mandibles were studied.
Results: In 9 out of 36 edentulous mandibles (25%), the MF was found nearby the AC, while in 27 edentulous mandibles (75%), the MF was located at an average distance 6.4 mm from the AC and 12.6 mm from the IBM. In 38 out of 66 dentate mandibles (57.6%), the MF was located at an average distance 13.6 mm from the AC and 15.2 mm from the IBM. The dental status significantly affected (p = 0.001) the distances MF-AC and MF-IBM. Side symmetry was observed for both dentate and edentulous mandibles (p = 0.39 and p = 0.45).
Conclusions: The MF is an important landmark and its location needs to be considered prior to dental implants placement in order to avoid the MN injury and related complications. The position of MF is altered in edentulous mandibles compared with the dentate ones. The MF is a symmetric structure in Greeks
A QCD space-time analysis of quarkonium formation and evolution in hadronic collisions
The production of heavy quarkonium as QQbar bound-states in hadron-hadron
collisions is considered within the framework of a space-time description,
combining parton-cascade evolution with a coalescence model for bound-state
formation. The `hard' production of the initial QQbar, directly or via gluon
fragmentation and including both color-singlet and color-octet contributions,
is calculated from the PQCD cross-sections. The subsequent development of the
QQbar system is described within a space-time generalization of the DGLAP
parton-evolution formalism in position- and momentum-space. The actual
formation of the bound-states is accomplished through overlap of the QQbar pair
and a spectrum of quarkonium wave-functions. This coalescence can only occur
after sufficent gluon radiation reduces the QQbar relative velocity to a value
commensurate with the non-relativistic kinematics of these bound systems. The
presence of gluon participants in the cascade then is both necessary and leads
to the natural inclusion of both color-singlet and color-octet mechanisms. The
application of this approach to pp (ppbar) collisions from sqrt(s)= 30 GeV - 14
TeV reveals very decent agreement with available data from ISR and Tevatron -
without the necessity of introducing fit parameters. Moreover, production
probabilities are calculated for a complete spectrum of charmonium and
bottonium states, with the relative significance compared to open charm
(bottom) production. An analysis of the space-time development is carried
through which sheds light on the relevance of gluon radiation and
color-structure, suggesting a correponding experimental investigation.Comment: 37 pages including 16 postscript figure
Examination of direct-photon and pion production in proton-nucleon collisions
We present a study of inclusive direct-photon and pion production in hadronic
interactions, focusing on a comparison of the ratio of gamma/pi0 yields with
expectations from next-to-leading order perturbative QCD (NLO pQCD). We also
examine the impact of a phenomenological model involving k_T smearing (which
approximates effects of additional soft-gluon emission) on absolute predictions
for photon and pion production and their ratio.Comment: 20 pages, 12 figures. Minor changes in wording and in figure
Hadroproduction and Polarization of Charmonium
In the limit of heavy quark mass, the production cross section and
polarization of quarkonia can be calculated in perturbative QCD. We study the
-averaged production of charmonium states in collisions at
fixed target energies. The data on the relative production rates of \jp and
is found to disagree with leading twist QCD. The polarization of the
\jp indicates that the discrepancy is not due to poorly known parton
distributions nor to the size of higher order effects (-factors). Rather,
the disagreement suggests important higher twist corrections, as has been
surmised earlier from the nuclear target -dependence of the production cross
section.Comment: 19 page
System Test of the ATLAS Muon Spectrometer in the H8 Beam at the CERN SPS
An extensive system test of the ATLAS muon spectrometer has been performed in
the H8 beam line at the CERN SPS during the last four years. This spectrometer
will use pressurized Monitored Drift Tube (MDT) chambers and Cathode Strip
Chambers (CSC) for precision tracking, Resistive Plate Chambers (RPCs) for
triggering in the barrel and Thin Gap Chambers (TGCs) for triggering in the
end-cap region. The test set-up emulates one projective tower of the barrel
(six MDT chambers and six RPCs) and one end-cap octant (six MDT chambers, A CSC
and three TGCs). The barrel and end-cap stands have also been equipped with
optical alignment systems, aiming at a relative positioning of the precision
chambers in each tower to 30-40 micrometers. In addition to the performance of
the detectors and the alignment scheme, many other systems aspects of the ATLAS
muon spectrometer have been tested and validated with this setup, such as the
mechanical detector integration and installation, the detector control system,
the data acquisition, high level trigger software and off-line event
reconstruction. Measurements with muon energies ranging from 20 to 300 GeV have
allowed measuring the trigger and tracking performance of this set-up, in a
configuration very similar to the final spectrometer. A special bunched muon
beam with 25 ns bunch spacing, emulating the LHC bunch structure, has been used
to study the timing resolution and bunch identification performance of the
trigger chambers. The ATLAS first-level trigger chain has been operated with
muon trigger signals for the first time
High-p_T pion and kaon production in relativistic nuclear collisions
High-p_T pion and kaon production is studied in relativistic proton-proton,
proton-nucleus, and nucleus-nucleus collisions in a wide energy range. Cross
sections are calculated based on perturbative QCD, augmented by a
phenomenological transverse momentum distribution of partons (``intrinsic
k_T''). An energy dependent width of the transverse momentum distribution is
extracted from pion and charged hadron production data in
proton-proton/proton-antiproton collisions. Effects of multiscattering and
shadowing in the strongly interacting medium are taken into account.
Enhancement of the transverse momentum width is introduced and parameterized to
explain the Cronin effect. In collisions between heavy nuclei, the model
over-predicts central pion production cross sections (more significantly at
higher energies), hinting at the presence of jet quenching. Predictions are
made for proton-nucleus and nucleus-nucleus collisions at RHIC energies.Comment: 26 pages in Latex, 19 EPS figure
Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
We discuss three different cases of hard inclusive spectra in proton-proton
collisions: high single hadron production at 20 GeV and
at = 62.4 GeV, and direct photon production at = 200 GeV;
with regard to their relevance for the search of Quark Gluon Plasma signals in
A+A collisions at SPS and RHIC energies.Comment: Proceeds. Hot Quarks 2004 Int. Workshop on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions. 26 pages. 26 figs. [minor
corrs., refs. added
Bottomonium and Drell-Yan production in p-A collisions at 450 GeV
The NA50 Collaboration has measured heavy-quarkonium production in p-A
collisions at 450 GeV incident energy (sqrt(s) = 29.1 GeV). We report here
results on the production of the Upsilon states and of high-mass Drell-Yan muon
pairs (m > 6 GeV). The cross-section at midrapidity and the A-dependence of the
measured yields are determined and compared with the results of other
fixed-target experiments and with the available theoretical estimates. Finally,
we also address some issues concerning the transverse momentum distributions of
the measured dimuons.Comment: 18 pages, 9 figures, to be published in Phys. Lett.
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