6,127 research outputs found
Study of Multi-muon Events from EAS with the L3 Detector at Shallow Depth Underground
We present first preliminary data from the L3+Cosmics experiment and results
from Monte Carlo simulations of multi-muon events as observed 30 m underground.Comment: 3 pages, 2 figures; presented at the 6th International Workshop on
Topics in Astroparticle and Underground Physics, TAUP99, September 6-10,
1999, Paris, Franc
Two-fermion and Two-photon Final States at LEP2 and Search for Extra Dimensions
For the first time the experiments ALEPH, DELPHI, L3 and OPAL have presented
preliminary results for fermion-pair and photon-pair production in e+e-
collisions on the full LEP2 data set. The details of the experimental
measurements and results from their LEP-wide combination are presented. No
statistically significant deviations from the Standard Model expectations are
observed and lower limits, some obtained in dedicated analyses, for new physics
phenomena at 95 % confidence level are derived. The scales of contact
interactions are constrained to lie above 10-20 TeV, depending on the helicity
structure. The Standard Model has thus been tested at LEP2 down to distances
10^{-19} - 10^{-20} m. This has many implications, one example being the
interpretation of the new result on the anomalous magnetic moment of the muon
as coming from muon substructure. For gamma-gamma final states the QED cut-offs
are Lambda_+ > 0.44 TeV and Lambda_- > 0.37 TeV. In a combined analysis, using
e+e- and gamma-gamma final states, the most stringent lower limits to date,
M_s^+ > 1.13 TeV (lambda = +1) and M_s^- > 1.39 TeV (lambda = -1), on the low
gravity effective Planck scale are set. Constrains on the scales of string
models like TeV strings and D-branes are derived. In the last case the lower
limit is 1.5 - 4 TeV, depending on the coupling strength.Comment: 20 pages, 12 figures, 7 tables; Invited LEP2 review talk, Les
Rencontres de Physique de la Vallee d'Aoste, La Thuile, Aosta Valley, Italy,
4-10 March 2001; v2 - minor typo correcte
Hint for axial-vector contact interactions in the data on e+e- -> e+e-(gamma) at centre-of-mass energies 192-208 GeV
For the first time the experiments ALEPH, DELPHI, L3 and OPAL have presented
preliminary results for fermion-pair production in e+e- collisions on the full
data set above the Z pole. A combined analysis of the Bhabha scattering
measurements is performed to search for effects of contact interactions. In the
case of two axial-vector (AA) currents the best fit to the data is 2.6 standard
deviations away from the Standard Model expectation, corresponding to an energy
scale TeV for contact interactions. For other
models no statistically significant deviations are observed, and the data are
used to set lower limits at 95 % confidence level on the contact interaction
scales ranging from 8.2 to 21.3 TeV, depending on the helicity structure.Comment: 6 pages, 1 table, 3 figure
LHAPDF : PDF Use from the Tevatron to the LHC
Parton Density Functions (PDFs) and their uncertainties are extremely important topics for both the Tevatron and the LHC. Experiments at the Tevatron can enhance this knowledge not only by constraining the PDF fits, but also by developing and refining the available PDF tools through feed-back from the experiments that are currently analyzing the highest energy hadron collider data available. It is important that the community has standardized tools and methods at its disposal. In this note we summarize briefly the most recent developments of the The Les Houches Accord PDF (LHAPDF), which is the modern replacement for PDFLIB. We also outline and compare the methods of quantifying the impact of PDF uncertainties on physical observables. The PDF weighting method for propagating errors from PDFs to event generator observables is outlined in detail, and example code for using this method with PYTHIA is also included
Virtual Data in CMS Analysis
The use of virtual data for enhancing the collaboration between large groups
of scientists is explored in several ways:
- by defining ``virtual'' parameter spaces which can be searched and shared
in an organized way by a collaboration of scientists in the course of their
analysis;
- by providing a mechanism to log the provenance of results and the ability
to trace them back to the various stages in the analysis of real or simulated
data;
- by creating ``check points'' in the course of an analysis to permit
collaborators to explore their own analysis branches by refining selections,
improving the signal to background ratio, varying the estimation of parameters,
etc.;
- by facilitating the audit of an analysis and the reproduction of its
results by a different group, or in a peer review context.
We describe a prototype for the analysis of data from the CMS experiment
based on the virtual data system Chimera and the object-oriented data analysis
framework ROOT. The Chimera system is used to chain together several steps in
the analysis process including the Monte Carlo generation of data, the
simulation of detector response, the reconstruction of physics objects and
their subsequent analysis, histogramming and visualization using the ROOT
framework.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 9 pages, LaTeX, 7 eps figures. PSN
TUAT010. V2 - references adde
Search for TeV Strings and New Phenomena in Bhabha Scattering at LEP2
A combined analysis of the data on Bhabha scattering at centre-of-mass
energies 183 and 189 GeV from the LEP experiments ALEPH, L3 and OPAL is
performed to search for effects of TeV strings in quantum gravity models with
large extra dimensions. No statistically significant deviations from the
Standard Model expectations are observed and lower limit on the string scale
M_S = 0.631 TeV at 95 % confidence level is derived. The data are used to set
lower limits on the scale of contact interactions ranging from 4.2 to 16.2 TeV
depending on the model. In a complementary analysis we derive an upper limit on
the electron size of 2.8 x 10^{-19} m at 95 % confidence level.Comment: 10 pages, 1 table, 3 figure
Utilizing Lustre filesystem with dCache for CMS analysis
This paper presents our new experimentations to utilize Lustre filesystem for CMS analysis with direct POSIX file access while keeping dCache as the frontend for data distribution and management. We describe our implementations that integrate dCache with Lustre filesystem and how to enable user data access without going through the dCache file read protocol. Our initial CMS analysis job measurement and transfer performance results are shown and the advantages of difference implementations are briefly discussed
The neutron 'thunder' accompanying the extensive air shower
Simulations show that neutrons are the most abundant component among
extensive air shower hadrons. However, multiple neutrons which appear with long
delays in neutron monitors nearby the EAS core ('neutron thunder') are mostly
not the neutrons of the shower, but have a secondary origin. The bulk of them
is produced by high energy EAS hadrons hitting the monitors. The delays are due
to the termalization and diffusion of neutrons in the moderator and reflector
of the monitor accompanied by the production of secondary gamma-quanta. This
conclusion raises the important problem of the interaction of EAS with the
ground, the stuff of the detectors and their environment since they have often
hydrogen containing materials like polyethilene in neutron monitors. Such
interaction can give an additional contribution to the signal in the EAS
detectors. It can be particularly important for the signals from scintillator
or water tank detectors at km-long distances from the EAS core where neutrons
of the shower become the dominant component after a few mcsec behind the EAS
front.Comment: 12 pages, 4 figures, accepted by J.Phys.G: Nucl.Part.Phy
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