60 research outputs found
First operation and drift field performance of a large area double phase LAr Electron Multiplier Time Projection Chamber with an immersed Greinacher high-voltage multiplier
We have operated a liquid-argon large-electron-multiplier time-projection
chamber (LAr LEM-TPC) with a large active area of 76 40 cm and a
drift length of 60 cm. This setup represents the largest chamber ever achieved
with this novel detector concept. The chamber is equipped with an immersed
built-in cryogenic Greinacher multi-stage high-voltage (HV) multiplier, which,
when subjected to an external AC HV of 1 kV, statically
charges up to a voltage a factor of 30 higher inside the LAr vessel,
creating a uniform drift field of 0.5 kV/cm over the full drift length.
This large LAr LEM-TPC was brought into successful operation in the
double-phase (liquid-vapor) operation mode and tested during a period of
1 month, recording impressive three-dimensional images of very
high-quality from cosmic particles traversing or interacting in the sensitive
volume. The double phase readout and HV systems achieved stable operation in
cryogenic conditions demonstrating their good characteristics, which
particularly suit applications for next-generation giant-scale LAr-TPCs.Comment: 26 pages, 19 figure
Phase Behavior of Bent-Core Molecules
Recently, a new class of smectic liquid crystal phases (SmCP phases)
characterized by the spontaneous formation of macroscopic chiral domains from
achiral bent-core molecules has been discovered. We have carried out Monte
Carlo simulations of a minimal hard spherocylinder dimer model to investigate
the role of excluded volume interations in determining the phase behavior of
bent-core materials and to probe the molecular origins of polar and chiral
symmetry breaking. We present the phase diagram as a function of pressure or
density and dimer opening angle . With decreasing , a transition
from a nonpolar to a polar smectic phase is observed near ,
and the nematic phase becomes thermodynamically unstable for . No chiral smectic or biaxial nematic phases were found.Comment: 4 pages Revtex, 3 eps figures (included
Neutrino-nucleus cross sections for oscillation experiments
Neutrino oscillations physics is entered in the precision era. In this
context accelerator-based neutrino experiments need a reduction of systematic
errors to the level of a few percent. Today one of the most important sources
of systematic errors are neutrino-nucleus cross sections which in the
hundreds-MeV to few-GeV energy region are known with a precision not exceeding
20%. In this article we review the present experimental and theoretical
knowledge of the neutrino-nucleus interaction physics. After introducing
neutrino oscillation physics and accelerator-based neutrino experiments, we
overview general aspects of the neutrino-nucleus cross sections, both
theoretical and experimental views. Then we focus on these quantities in
different reaction channels. We start with the quasielastic and
quasielastic-like cross section, putting a special emphasis on multinucleon
emission channel which attracted a lot of attention in the last few years. We
review the main aspects of the different microscopic models for this channel by
discussing analogies and differences among them.The discussion is always driven
by a comparison with the experimental data. We then consider the one pion
production channel where data-theory agreement remains very unsatisfactory. We
describe how to interpret pion data, then we analyze in particular the puzzle
related to the impossibility of theoretical models and Monte Carlo to
simultaneously describe MiniBooNE and MINERvA experimental results. Inclusive
cross sections are also discussed, as well as the comparison between the
and cross sections, relevant for the CP violation
experiments. The impact of the nuclear effects on the reconstruction of
neutrino energy and on the determination of the neutrino oscillation parameters
is reviewed. A window to the future is finally opened by discussing projects
and efforts in future detectors, beams, and analysis
First muon-neutrino disappearance study with an off-axis beam
We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment
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Airflow-aligned helical nanofilament (B4) phase in topographic confinement
We investigated a controlled helical nanofilament (HNF: B4) phase under topographic confinement with airflow that can induce a shear force and temperature gradient on the sample. The resulting orientation and ordering of the B4 phase in this combinational effort was directly investigated using microscopy. The structural freedom of the complex B7 phase, which is a higher temperature phase than the B4 phase, can result in relatively complex microscopic arrangements of HNFs compared with the B4 phase generated from the simple layer structure of the B2 phase. This interesting chiral/polar nanofilament behaviour offers new opportunities for further exploration of the exotic physical properties of the B4 phase
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