4,426 research outputs found
Muon Energy Loss Upsteam of the Muon Spectrometer
A method for the estimation of the muon energy loss downstream of the Muons Spectrometer is presented. The method provides an improved and updated parametrization of the muon energy loss in ATLAS, along with an estimation based on the actual energy deposition in the calorimeters. The latter aims to account, on an event-by-event basis, for the statistical fluctuations of the energy loss. The final implementation of the presented method combines both the energy loss parametrization and the calorimeter information. This hybrid method provides on average a 5% improvement on the muon stand-alone momentum resolution, reaching 10% for , and reduces the non-gaussian tails. The method is implemented inside the ATHENA framework, in the MuidCaloEnergyTools package
The ATLAS Student Event Challenge
The ASEC (ATLAS Student Event Challenge) is an educational project which allows the students to learn about the elementary particles by studying "events", the products of beam collisions at the LHC. The events are collected by the ATLAS detector and displayed graphically using the ATLANTIS package. The students are given the means to select and analyse the events on-line, and subsequently present the results and draw conclusions
The ATLAS Muon Spectrometer and the hunt for the Higgs Boson(s)
The Muon Spectrometer is an essential part of the ATLAS Experiment at the LHC. It is used both for triggering and for momentum measurements of the muons. The four different technologies used for the Muon chambers as well as their expected performance will be described. Furthermore, the ATLAS sensitivity for the SM and the MSSM Higgs bosons decaying into muons will be reviewed. Emphasis will be given in the expected discovery potentials from the first year of running
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
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
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
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
J/Psi Suppression in Heavy Ion Collisions at the CERN SPS
We reexamine the production of J/Psi and other charmonium states for a
variety of target-projectile choices at the SPS. For this study we use a newly
constructed cascade code LUCIFER II, which yields acceptable descriptions of
both hard and soft processes, specifically Drell-Yan and hidden charm
production, and soft energy loss and meson production, at the SPS. Glauber
calculations of other authors are redone, and compared directly to the cascade
results. The modeling of the charmonium states differs from that of earlier
workers in its unified treatment of the hidden charm meson spectrum, which is
introduced from the outset as a set of coupled states. The result is a
description of the NA38 and NA50 data in terms of a conventional hadronic
picture. The apparently anomalous suppression found in the most massive Pb+Pb
system arises from three sources: destruction in the initial nucleon-nucleon
cascade, use of coupled channels to exploit the larger breakup in the less
bound Chi and Psi' states, and comover interaction in the final low energy
phase.Comment: 36 pages (15 figures
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
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