7,067 research outputs found
Nuclear modification of valence-quark distributions and its effects on NuTeV sin^2 theta_W anomaly
We investigated a nuclear modification difference between up- and
down-valence quark distributions by analyzing structure function F_2 and
Drell-Yan cross-section ratios. Although nuclear modifications of the
valence-quark distributions themselves are rather well determined, it is
difficult to find their difference from the present data. We estimated such an
effect on the NuTeV sin^2 theta_W value and its uncertainty by the Hessian
method. At this stage, it is not large enough to explain the whole NuTeV
anomaly. However, the modification difference cannot be precisely determined,
so that further studies are needed.Comment: 3 pages, LaTeX, 1 eps file, to be published in Proceedings of the 6th
International Workshop on Neutrino Factories and Superbeams (NuFact04
Shortage of vaccines during a yellow fever outbreak in Guinea.
A yellow fever epidemic erupted in Guinea in September, 2000. From Sept 4, 2000, to Jan 7, 2001, 688 instances of the disease and 225 deaths were reported. The diagnosis was laboratory confirmed by IgM detection in more than 40 patients. A mass vaccination campaign was limited by insufficient international stocks. After the epidemic in Guinea, the International Coordinating Group on Vaccine Provision for Epidemic Meningitis Control decided that 2 million doses of 17D yellow fever vaccine, being stored as part of a UNICEF stockpile, should be used only in response to outbreaks
Can a 3+2 Oscillation Model Explain the NuTeV Electroweak Results?
The weak mixing angle result from NuTeV falls three standard deviations above
the value determined by global electroweak fits. It has been suggested that one
possible explanation for this result could be the oscillation of electron
neutrinos in the NuTeV beam to sterile neutrinos. This article examines several
cases of masses and mixings for 3+2 neutrino oscillation models which fit the
current oscillation data at 99% CL. We conclude that electron to sterile
neutrino oscillations can account for only up to a third of a standard
deviation between the NuTeV determination of the weak mixing angle and the
standard model.Comment: 3 pages, 2 figures, submitted to Brief Report
An aza-cyclophane stacked in racemic columnar assemblies: whole-molecule disorder in a two-dimensional solid solution
The oxime derivative of [1.1.1]cyclophane cyclotriveratrylene (CTV) was ring expanded utilizing a Beckmann rearrangement to provide a ten-membered N-acetyl macrocyclic amide that crystallizes as a chloroform monosolvate in columnar assemblies manifesting an unusual disorder within the crystal. Columns made up of this structure consist of infinite columnar assemblies of alternating D and L enantiomers and therefore necessarily are made up of a racemate, yet the chiralities of individual molecules in adjacent columns are independent of one another, leading to the overall formation of a two-dimensional solid solution. The random arrangement of the columns within the structure leads to the emergence of a crystallographic mirror plane not reflected by the molecular symmetry, to a change of symmetry from Pna21 to Pnma and to whole-molecule disorder of the bowl-shaped molecules within the columns
Overview of progress in neutrino scattering measurements
Recent progress in neutrino scattering experiments with few GeV neutrino
beams is reviewed, focusing on new experimental input since the beginning of
the NuInt workshop series in 2001. Progress in neutrino quasi-elastic
scattering, resonance production, coherent pion production, scattering in the
transition region between the resonance and deep inelastic regimes, and nuclear
effects in neutrino-nucleus scattering, is discussed.Comment: To appear in the proceedings of 5th International Workshop on
Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt07), Batavia,
Illinois, 30 May - 3 Jun 2007. Submitted to AIP Conf.Pro
Understanding the Forward Muon Deficit in Coherent Pion Production
For any inelastic process with ,
the cross section at is given by Adler's PCAC theorem.
Inclusion of the lepton mass has a dynamical effect (``PCAC-screening'') caused
by interference of spin-zero () and spin-one exchanges. This effect may
be relevant to the forward suppression reported in recent experiments.Comment: 3 pages, 2 figures, presented at NuInt07, Fermilab, may 31 - june 3
200
Modified Paschos-Wolfenstein relation and extraction of weak mixing angle sin^2 theta_W
The NuTeV collaboration reported anomalously large weak mixing angle sin^2
theta_W in comparison with the standard model prediction. Neutrino and
antineutrino charged- and neutral-current events are analyzed for extracting
sin^2 theta_W. Although the Paschos-Wolfenstein relation is not directly used
in the analysis, it plays an important role in the determination. Noting that
the target nucleus, iron, is not an isoscalar nucleus, we derive a
leading-order expression for a modified Paschos-Wolfenstein relation for
nuclei, which may have neutron excess. Then, using charge and baryon-number
conservations for nuclei, we discuss a nuclear correction in the sin^2 theta_W
determination. It is noteworthy that nuclear modifications are different
between valence up- and down-quark distributions. We show this difference
effect on the NuTeV sin^2 theta_W deviation.Comment: 5 pages, REVTeX4.0, revtex4.cls, url.sty, natbib.sty, revsymb.sty,
10pt.rtx, aps.rtx, amssymb.sty, amsfonts.sty, 3 eps figures. Phys. Rev. D in
press. Email: [email protected] See also http://hs.phys.saga-u.ac.j
A steerable UV laser system for the calibration of liquid argon time projection chambers
A number of liquid argon time projection chambers (LAr TPC's) are being build
or are proposed for neutrino experiments on long- and short baseline beams. For
these detectors a distortion in the drift field due to geometrical or physics
reasons can affect the reconstruction of the events. Depending on the TPC
geometry and electric drift field intensity this distortion could be of the
same magnitude as the drift field itself. Recently, we presented a method to
calibrate the drift field and correct for these possible distortions. While
straight cosmic ray muon tracks could be used for calibration, multiple coulomb
scattering and momentum uncertainties allow only a limited resolution. A UV
laser instead can create straight ionization tracks in liquid argon, and allows
one to map the drift field along different paths in the TPC inner volume. Here
we present a UV laser feed-through design with a steerable UV mirror immersed
in liquid argon that can point the laser beam at many locations through the
TPC. The straight ionization paths are sensitive to drift field distortions, a
fit of these distortion to the linear optical path allows to extract the drift
field, by using these laser tracks along the whole TPC volume one can obtain a
3D drift field map. The UV laser feed-through assembly is a prototype of the
system that will be used for the MicroBooNE experiment at the Fermi National
Accelerator Laboratory (FNAL)
Neutral Current Production in MiniBooNE
This paper describes the analysis used to determine the neutral current
production in MiniBooNE in bins of momentum. Additionally, a
measurement of the relative coherent production of s is discussed. The
coherent production rate is found to be (19.5 1.1 (stat) 2.5 (sys))%
of the total exclusive neutral current production rate.Comment: Prepared for the Proceedings of Neutrino Interactions 200
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