6,792 research outputs found
The VELO High Voltage System Control Software
This note describes the VELO high voltage control software. The implementation of its structure as a PVSS Finite State Machine is emphasized. The main error conditions that may occur during operation is also discussed. The VELO HV software conforms to the specification of the VELO
A new generation photodetector for astroparticle physics: the VSiPMT
The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design we
proposed for a revolutionary photon detector. The main idea is to replace the
classical dynode chain of a PMT with a SiPM (G-APD), the latter acting as an
electron detector and amplifier. The aim is to match the large sensitive area
of a photocathode with the performance of the SiPM technology. The VSiPMT has
many attractive features. In particular, a low power consumption and an
excellent photon counting capability. To prove the feasibility of the idea we
first tested the performance of a special non-windowed SiPM by Hamamatsu (MPPC)
as electron detector and current amplifier. Thanks to this result Hamamatsu
realized two VSiPMT industrial prototypes. In this work, we present the results
of a full characterization of the VSiPMT prototype
Performance of the LHCb muon system
The performance of the LHCb Muon system and its stability across the full
2010 data taking with LHC running at ps = 7 TeV energy is studied. The
optimization of the detector setting and the time calibration performed with
the first collisions delivered by LHC is described. Particle rates, measured
for the wide range of luminosities and beam operation conditions experienced
during the run, are compared with the values expected from simulation. The
space and time alignment of the detectors, chamber efficiency, time resolution
and cluster size are evaluated. The detector performance is found to be as
expected from specifications or better. Notably the overall efficiency is well
above the design requirementsComment: JINST_015P_1112 201
Nanoscale modulation of the density of states at the conducting interface between LaAlO3 and SrTiO3 band insulators
The appearance of high-mobility electrons at the LaAlO3/SrTiO3 interface has raised strong interest in the material science community and a lively debate on the origin of the phenomenon. A possible explanation is an electronic reconstruction, realizing a transfer of electrons to SrTiO3 at the interface, thereby avoiding the build-up of excessive Coulomb energy as described by the "polarization catastrophe" associated with the alternating polar layers of the LaAlO3 film. Theoretical models predict that electrons are transferred into titanium 3d(xy) interface states and, in the presence of strong correlations, generate a charge and orbital order. Here we provide experimental evidence that at room temperature the local density of states of the LaAlO3/SrTiO3 conducting interface is modulated at the nanoscale in a short-range quasiperiodic pattern, which is consistent with the appearance of an orbital (short-range) order. This result, together with the splitting of the 3d states, confirms that an electronic reconstruction drives the functional properties of the LaAlO3/SrTiO3 oxide interface. The short-range superstructure does not fully agree with the theoretical predictions. Thus, further experimental and theoretical investigations are required to understand the electronic properties of the 2D electron system realised at the LaAlO3/SrTiO3 interface
Symmetry breaking at the (111) interfaces of SrTiO hosting a 2D-electron system
We used x-ray absorption spectroscopy to study the orbital symmetry and the
energy band splitting of (111) LaAlO/SrTiO and
LaAlO/EuTiO/SrTiO heterostructures, hosting a quasi
two-dimensional electron system (q2DES), and of a Ti-terminated (111)
SrTiO single crystal, also known to form a q2DES at its surface. We
demonstrate that the bulk tetragonal Ti-3d D crystal field is
turned into trigonal D crystal field in all cases. The symmetry
adapted a and e orbitals are non-degenerate in energy and
their splitting, \Delta, is positive at the bare STO surface but negative in
the heterostructures, where the a orbital is lowest in energy.
These results demonstrate that the interfacial symmetry breaking induced by
epitaxial engineering of oxide interfaces has a dramatic effect on their
electronic properties, and it can be used to manipulate the ground state of the
q2DES.Comment: 6 pages article, plus 5 pages supplementary informatio
Leading order analysis of neutrino induced dimuon events in the CHORUS experiment
We present a leading order QCD analysis of a sample of neutrino induced
charged-current events with two muons in the final state originating in the
lead-scintillating fibre calorimeter of the CHORUS detector. The results are
based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign
dimuon events collected during the exposure of the detector to the CERN Wide
Band Neutrino Beam between 1995 and 1998. % with GeV
and GeV collected %between 1995 and 1998. The analysis yields a
value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a
value of the ratio of the strange to non-strange sea in the nucleon of , improving the results obtained in similar analyses
by previous experiments.Comment: Submitted to Nuclear Physics
Two-dimensional electron gas at the (001) surface of ferromagnetic EuTiO3
Studies on oxide quasi-two-dimensional electron gas (q2DEG) have been a playground for the discovery of novel and sometimes unexpected phenomena, like the reported magnetism at the surface of SrTiO3 (001) and at the interface between nonmagnetic LaAlO3 and SrTiO3 band insulators. However, magnetism in this system is weak and there is evidence of a nonintrinsic origin. Here, by using in situ high-resolution angle-resolved photoemission, we demonstrate that ferromagnetic EuTiO3, the magnetic counterpart of SrTiO3 in the bulk, hosts a q2DEG at its (001) surface. This is confirmed by density functional theory calculations with Hubbard U terms in the presence of oxygen divacancies in various configurations, all of them leading to a spin-polarized q2DEG related to the ferromagnetic order of Eu-4f magnetic moments. The results suggest EuTiO3(001) as a new material platform for oxide q2DEGs, characterized by broken inversion and time-reversal symmetries
Performance of the LHCb muon system with cosmic rays
The LHCb Muon system performance is presented using cosmic ray events
collected in 2009. These events allowed to test and optimize the detector
configuration before the LHC start. The space and time alignment and the
measurement of chamber efficiency, time resolution and cluster size are
described in detail. The results are in agreement with the expected detector
performance.Comment: Submitted to JINST and accepte
Charged-Particle Multiplicities in Charged-Current Neutrino-- and Anti-Neutrino--Nucleus Interactions
The CHORUS experiment, designed to search for
oscillations, consists of a nuclear emulsion target and electronic detectors.
In this paper, results on the production of charged particles in a small sample
of charged-current neutrino-- and anti-neutrino--nucleus interactions at high
energy are presented. For each event, the emission angle and the ionization
features of the charged particles produced in the interaction are recorded,
while the standard kinematic variables are reconstructed using the electronic
detectors. The average multiplicities for charged tracks, the pseudo-rapidity
distributions, the dispersion in the multiplicity of charged particles and the
KNO scaling are studied in different kinematical regions. A study of
quasi-elastic topologies performed for the first time in nuclear emulsions is
also reported. The results are presented in a form suitable for use in the
validation of Monte Carlo generators of neutrino--nucleus interactions.Comment: 17 pages, 5 figure
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