826 research outputs found
Solutions to the R_b, R_c and alpha_s puzzles by Vector Fermions
We propose two minimal extensions of Standard Model, both of which can easily
accommodate the recent puzzling observations about the excess in , the
deficit in and the discrepancy in the low energy and high energy
determinations of . Each model requires three additional heavy
vectorial fermions in order to resolve the puzzles. The current
phenomenological constraints and the new potential phenomena are also
discussed.Comment: 12 pages, in LaTeX, postscript file also appear
http://www.uic.edu/~keung/pub/rbrc.p
Phenomenology of neutral heavy leptons
We continue our previous work on the flavour-conserving leptonic decays of
the Z boson with neutral heavy leptons (NHL's) in the loops by considering box,
vertex, and self-energy diagrams for the muon decay. By inclusion of these
loops (they contribute to the input parameter M_W) we can probe the full
parameter space spanned by the so-called flavour-conserving mixing parameters
ee_(mix), \mu\mu_(mix), \tau\tau_(mix) in a superstring-inspired model of
neutrino mass. We compare the results of our analysis with the existing work in
this field and conclude that flavour-conserving decays have certain advantages
over traditionally considered flavour-violating ones.Comment: submitted to Phys. Rev. D, 30 pages, 9 figures (ps), REVTE
The OPERA experiment Target Tracker
The main task of the Target Tracker detector of the long baseline neutrino
oscillation OPERA experiment is to locate in which of the target elementary
constituents, the lead/emulsion bricks, the neutrino interactions have occurred
and also to give calorimetric information about each event. The technology used
consists in walls of two planes of plastic scintillator strips, one per
transverse direction. Wavelength shifting fibres collect the light signal
emitted by the scintillator strips and guide it to both ends where it is read
by multi-anode photomultiplier tubes. All the elements used in the construction
of this detector and its main characteristics are described.Comment: 25 pages, submitted to Nuclear Instrument and Method
Two-Fermion Production in Electron-Positron Collisions
This report summarizes the results of the two-fermion working group of the
LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the
theoretical calculations of the two fermion production process in the
electron-positron collision at LEP2 center of the mass energies are reported.
The Bhabha process and the production of muon, tau, neutrino and quark pairs is
covered. On the basis of comparison of various calculations, theoretical
uncertainties are estimated and compared with those needed for the final LEP2
data analysis. The subjects for the further studies are identified.Comment: 2-fermion working group report of the LEP2 Monte Carlo Workshop
1999/2000, 113 pages, 24 figures, 35 table
Event Generators for WW Physics
The report summarizes the results of the activities of the Working Group on
Event Generators for WW Physics at CERN during 1995.Comment: 99 Latex, including 30 figures, 24 tables. The report is part of:
G.Altarelli,T.Sjostrand and F.Zwirner (eds), Physics at LEP2 CERN 96-0
Spin physics with antiprotons
New possibilities arising from the availability at GSI of antiproton beams,
possibly polarised, are discussed. The investigation of the nucleon structure
can be boosted by accessing in Drell-Yan processes experimental asymmetries
related to cross-sections in which the parton distribution functions (PDF) only
appear, without any contribution from fragmentation functions; such processes
are not affected by the chiral suppression of the transversity function
. Spin asymmetries in hyperon production and Single Spin Asymmetries
are discussed as well, together with further items like electric and magnetic
nucleonic form factors and open charm production. Counting rates estimations
are provided for each physical case. The sketch of a possible experimental
apparatus is proposed.Comment: Presented for the proceedings of ASI "Spin and Symmetry", Prague,
July 5-10, 2004, to be published in Czech. J. Phys. 55 (2005
Measurement of the atmospheric muon charge ratio with the OPERA detector
The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used
to measure the atmospheric muon charge ratio in the TeV energy region. We
analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime
during the 2008 CNGS run. We computed separately the muon charge ratio for
single and for multiple muon events in order to select different energy regions
of the primary cosmic ray spectrum and to test the charge ratio dependence on
the primary composition. The measured charge ratio values were corrected taking
into account the charge-misidentification errors. Data have also been grouped
in five bins of the "vertical surface energy". A fit to a simplified model of
muon production in the atmosphere allowed the determination of the pion and
kaon charge ratios weighted by the cosmic ray energy spectrum.Comment: 14 pages, 10 figure
The detection of neutrino interactions in the emulsion/lead target of the OPERA experiment
The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode through the study of oscillations. The
apparatus consists of an emulsion/lead target complemented by electronic
detectors and it is placed in the high energy long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were
successfully carried out in 2007 and 2008 with the detector fully operational
with its related facilities for the emulsion handling and analysis. After a
brief description of the beam and of the experimental setup we report on the
collection, reconstruction and analysis procedures of first samples of neutrino
interaction events
First events from the CNGS neutrino beam detected in the OPERA experiment
The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode, through the study of nu_mu to nu_tau oscillations. The
apparatus consists of a lead/emulsion-film target complemented by electronic
detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. In August 2006 a first run with
CNGS neutrinos was successfully conducted. A first sample of neutrino events
was collected, statistically consistent with the integrated beam intensity.
After a brief description of the beam and of the various sub-detectors, we
report on the achievement of this milestone, presenting the first data and some
analysis results.Comment: Submitted to the New Journal of Physic
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
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