987 research outputs found
Event activity-dependence of jet production in p-Pb collisions at TeV measured with semi-inclusive hadron+jet correlations by ALICE
We report measurement of the semi-inclusive distribution of charged-particle
jets recoiling from a high transverse momentum () hadron trigger,
for p-Pb collisions at TeV, in p-Pb events
classified by event activity. This observable has been measured in pp and Pb-Pb
collisions at the LHC, providing a new probe to measure quenching. Jets are
reconstructed from charged particle tracks using anti- with and low IR cutoff of jet constituents ( GeV/).
The complex uncorrelated jet background is corrected by a data-driven approach.
Recoil jet distributions are reported for
GeV/. Events are classified by signal in the ALICE V0A detector, which
measures forward multiplicity, and ZNA, which measures the number of neutrons
at zero degrees. This self-normalized observable does not require scaling of
reference distributions by , thereby avoiding the need for
geometric modeling. We compare the trigger-normalized recoil jet yield for p-Pb
collisions with different event activity to measure the effects of jet
quenching in small systems at the LHC.Comment: Proceedings of the Quark Matter 2017 conference, February 6-11, 201
Correlations and flavors in jets in ALICE
We report on the measurement of hadron composition in charged jets in pp at
TeV and show the first data on particle type dependent jet
fragmentation at the LHC. Further, we present
K ratios measured in charged jets
in Pb-Pb collisions at TeV and in p-Pb
collisions at TeV. While the ratio of the
inclusive spectra of and K
exhibits centrality dependent enhancement both in Pb-Pb and p-Pb system, the
K ratio measured in charged jets
reveals that jet fragmentation does not contribute to the observed baryon
anomaly.
Finally, we discuss the measurement of semi-inclusive
spectra of charged jets that recoil from a high- hadron trigger
in Pb-Pb and pp collisions at TeV and TeV, respectively. The jet yield uncorrelated with the trigger hadron is
removed at the event-ensemble level without introducing a bias on the jet
population which is therefore infrared and collinear safe. The recoil jet yield
in central Pb-Pb is found to be suppressed w.r.t. that from pp PYTHIA
reference. On the other hand, there is no sign of intra-jet broadening even for
anti- jets with a resolution parameter as large as .Comment: Proceedings of Strangeness in Quark Matter conference, 6 July - 11
July 2015, Dubna, Russi
ULTRA-LOW INTENSITY PROTON BEAMS FOR RADIATION RESPONSE RELATED EXPERIMENTS AT THE U-120M CYCLOTRON
The U-120M cyclotron at the Nuclear Physics Institute (NPI) of the Czech Academy of Sciences in Rez is used for radiation hardness tests of electronics for high-energy physics experiments. These tests are usually carried out with proton fluxes of the order of 105–109 proton·cm−2·s−1. Some tests done for the upgrade of the Inner Tracking System of the ALICE experiment at CERN, however, required proton beam intensities several orders of magnitude lower. This paper presents a method which has been developed to achieve the proton beam flux of the order of 1 proton · cm−2·s−1. The method is mainly based on reduction of the discharge current in the cyclotron internal Penning type ion source. Influence of this new operation mode on the lifetime of ion source cathodes is discussed
Shadow epitaxy for in-situ growth of generic semiconductor/superconductor devices
Uniform, defect-free crystal interfaces and surfaces are crucial ingredients
for realizing high-performance nanoscale devices. A pertinent example is that
advances in gate-tunable and topological superconductivity using
semiconductor/superconductor electronic devices are currently built on the hard
proximity-induced superconducting gap obtained from epitaxial indium
arsenide/aluminium heterostructures. Fabrication of devices requires selective
etch processes; these exist only for InAs/Al hybrids, precluding the use of
other, potentially superior material combinations. We present a crystal growth
platform -- based on three-dimensional structuring of growth substrates --
which enables synthesis of semiconductor nanowire hybrids with in-situ
patterned superconductor shells. This platform eliminates the need for etching,
thereby enabling full freedom in choice of hybrid constituents. We realise and
characterise all the most frequently used architectures in superconducting
hybrid devices, finding increased yield and electrostatic stability compared to
etched devices, along with evidence of ballistic superconductivity. In addition
to aluminium, we present hybrid devices based on tantalum, niobium and
vanadium.
This is the submitted version of the manuscript. The accepted, peer reviewed
version is available from Advanced Materials:
http://doi.org/10.1002/adma.201908411
Previous title: Shadow lithography for in-situ growth of generic
semiconductor/superconductor device
Field effect enhancement in buffered quantum nanowire networks
III-V semiconductor nanowires have shown great potential in various quantum
transport experiments. However, realizing a scalable high-quality
nanowire-based platform that could lead to quantum information applications has
been challenging. Here, we study the potential of selective area growth by
molecular beam epitaxy of InAs nanowire networks grown on GaAs-based buffer
layers. The buffered geometry allows for substantial elastic strain relaxation
and a strong enhancement of field effect mobility. We show that the networks
possess strong spin-orbit interaction and long phase coherence lengths with a
temperature dependence indicating ballistic transport. With these findings, and
the compatibility of the growth method with hybrid epitaxy, we conclude that
the material platform fulfills the requirements for a wide range of quantum
experiments and applications
Development of Nb-GaAs based superconductor semiconductor hybrid platform by combining in-situ dc magnetron sputtering and molecular beam epitaxy
We present Nb thin films deposited in-situ on GaAs by combining molecular
beam epitaxy and magnetron sputtering within an ultra-high vacuum cluster. Nb
films deposited at varying power, and a reference film from a commercial
system, are compared. The results show clear variation between the in-situ and
ex-situ deposition which we relate to differences in magnetron sputtering
conditions and chamber geometry. The Nb films have critical temperatures of
around . and critical perpendicular magnetic fields of up to
at . From STEM images of the GaAs-Nb
interface we find the formation of an amorphous interlayer between the GaAs and
the Nb for both the ex-situ and in-situ deposited material.Comment: 12 pages paper, 9 pages supplementary, 6 figures paper, 7 figures
supplementar
Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis
Epitaxially
connected nanowires allow for the design of electron
transport experiments and applications beyond the standard two terminal
device geometries. In this Letter, we present growth methods of three
distinct types of wurtzite structured InAs nanocrosses via the vapor–liquid–solid
mechanism. Two methods use conventional wurtzite nanowire arrays as
a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses.
A third method uses the 2-fold cubic symmetry of (100) substrates
to form well-defined coherent inclusions of zinc blende in the center
of the nanocrosses. We show that all three types of nanocrosses can
be transferred undamaged to arbitrary substrates, which allows for
structural, compositional, and electrical characterization. We further
demonstrate the potential for synthesis of as-grown nanowire networks
and for using nanowires as shadow masks for in situ fabricated junctions
in radial nanowire heterostructures
Terahertz probing of anisotropic conductivity and morphology of CuMnAs epitaxial thin films
Antiferromagnetic CuMnAs thin films have attracted attention since the
discovery of the manipulation of their magnetic structure via electrical,
optical, and terahertz pulses of electric fields, enabling convenient
approaches to the switching between magnetoresistive states of the film for the
information storage. However, the magnetic structure and, thus, the efficiency
of the manipulation can be affected by the film morphology and growth defects.
In this study, we investigate the properties of CuMnAs thin films by probing
the defect-related uniaxial anisotropy of electric conductivity by contact-free
terahertz transmission spectroscopy. We show that the terahertz measurements
conveniently detect the conductivity anisotropy, that are consistent with
conventional DC Hall-bar measurements. Moreover, the terahertz technique allows
for considerably finer determination of anisotropy axes and it is less
sensitive to the local film degradation. Thanks to the averaging over a large
detection area, the THz probing also allows for an analysis of strongly
non-uniform thin films. Using scanning near-field terahertz and electron
microscopies, we relate the observed anisotropic conductivity of CuMnAs to the
elongation and orientation of growth defects, which influence the local
microscopic conductivity. We also demonstrate control over the morphology of
defects by using vicinal substrates.Comment: 33 pages, 16 figure
Molecular beam epitaxy of CuMnAs
We present a detailed study of the growth of the tetragonal polymorph of
antiferromagnetic CuMnAs by the molecular beam epitaxy technique. We explore
the parameter space of growth conditions and their effect on the
microstructural and transport properties of the material. We identify its
typical structural defects and compare the properties of epitaxial CuMnAs
layers grown on GaP, GaAs and Si substrates. Finally, we investigate the
correlation between the crystalline quality of CuMnAs and its performance in
terms of electrically induced resistance switching.Comment: 10 pages, 8 figures and supplementary materia
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