3,525 research outputs found
Nonlinear motion and mechanical mixing in as-grown GaAs nanowires
We report nonlinear behavior in the motion of driven nanowire cantilevers.
The nonlinearity can be described by the Duffing equation and is used to
demonstrate mechanical mixing of two distinct excitation frequencies.
Furthermore, we demonstrate that the nonlinearity can be used to amplify a
signal at a frequency close to the mechanical resonance of the nanowire
oscillator. Up to 26 dB of amplitude gain are demonstrated in this way
Time Calibration of the LHCb muon System
The LHCb muon System consists of about 122,000 frontend channels. It plays a basic role in the first trigger level. The trigger requires 95% efficiency in muon tracks detection. It is then necessary to reach a system time alignment at the level of about 2 ns. This alignment must be monitored against possible fluctuations due to changes in the detector operating conditions. We describe the custom instrumentation implemented at system level for time calibration, the strategy adopted, the procedure to be followed both for system alignment and monitoring, the control program realized for this purpose. We also illustrate first results obtained during the detector commissioning in the LHCb pit
Far UV responsivity of commercial silicon photodetectors
Abstract Responsivity measurements have been performed on commercial silicon photodetectors in the UV range 200–400 nm. The microstrip and pixel detectors have been reverse biased in fully depleted condition (more than 25 V reverse bias) and in partially depleted condition (5 V reverse bias). We have also performed measurements in back illumination geometry, of particular interest in most industrial applications. Promising results obtained with commercial photodetectors in the UV range in terms of photocurrent stability and sensitivity open a variety of applications
Low-mass dark matter search with the DarkSide-50 experiment
We present the results of a search for dark matter weakly interacting massive particles (WIMPs) in the mass range below 20 GeV=c2using a target of low-radioactivity argon with a 6786.0 kg d exposure. The data were obtained using the DarkSide-50 apparatus at Laboratori Nazionali del Gran Sasso. The analysis is based on the ionization signal, for which the DarkSide-50 time projection chamber is fully efficient at 0.1 keVee. The observed rate in the detector at 0.5 keVee is about 1.5 event=keVee=kg=d and is almost entirely accounted for by known background sources. We obtain a 90% C.L. exclusion limit above 1.8 GeV=c2for the spin-independent cross section of dark matter WIMPs on nucleons, extending the exclusion region for dark matter below previous limits in the range 1.8-6 GeV=c2
Potentialities of a low-energy detector based on He evaporation to observe atomic effects in coherent neutrino scattering and physics perspectives
We propose an experimental setup to observe coherent elastic neutrino-atom
scattering (CEAS) using electron antineutrinos from tritium decay and a
liquid helium target. In this scattering process with the whole atom, that has
not beeen observed so far, the electrons tend to screen the weak charge of the
nucleus as seen by the electron antineutrino probe. The interference between
the nucleus and the electron cloud produces a sharp dip in the recoil spectrum
at atomic recoil energies of about 9 meV, reducing sizeably the number of
expected events with respect to the coherent elastic neutrino-nucleus
scattering case. We estimate that with a 60 g tritium source surrounded by 500
kg of liquid helium in a cylindrical tank, one could observe the existence of
CEAS processes at 3 in 5 years of data taking. Keeping the same
amount of helium and the same data-taking period, we test the sensitivity to
the Weinberg angle and a possible neutrino magnetic moment for three different
scenarios: 60 g, 160 g, and 500 g of tritium. In the latter scenario, the
Standard Model (SM) value of the Weinberg angle can be measured with a
statistical uncertainty of
. This would represent the
lowest-energy measurement of , with the advantage of being
not affected by the uncertainties on the neutron form factor of the nucleus as
the current lowest-energy determination. Finally, we study the sensitivity of
this apparatus to a possible electron neutrino magnetic moment and we find that
using 60 g of tritium it is possible to set an upper limit of about
at 90% C.L., that is more than one order of magnitude
smaller than the current experimental limit.Comment: 9 pages, 7 figures, Fig. 3 corrected, improved discussion on electron
form factor (Fig. 1 added) and detector layou
New constraint on neutrino magnetic moment and neutrino millicharge from LUX-ZEPLIN dark matter search results
Elastic neutrino-electron scattering represents a powerful tool to investigate key neutrino properties. In view of the recent results released by the LUX-ZEPLIN collaboration, we provide a first determination of the limits achievable on the neutrino magnetic moment and neutrino millicharge, whose effect becomes non-negligible in some beyond the Standard Model theories. In this context, we evaluate and discuss the impact of different approximations to describe the neutrino interaction with atomic electrons. The new LUX-ZEPLIN data allows us to set a very competitive limit on the neutrino magnetic moment when compared to the other laboratory bounds, namely mu effv < 1.1 x 10-11 mu B at 90% C.L., which improves by a factor of 2.5 the Borexino collaboration limit and represents the second best world limit after the recent XENONnT result. Moreover, exploiting the so-called equivalent photon approximation, we obtain the most stringent limit on the neutrino millicharge, namely Iqeffv I < 1.5 x 10-13e0 at 90% C.L., which represents a great improvement with respect to the previous laboratory bounds
Gallium arsenide photodetectors for imaging in the far ultraviolet region
The aim of the present work is to systematically investigate the response and stability of commercial GaAs devices in the 200–400 nm UV range with a view to establishing their potentiality in imaging devices. The irradiation results of GaAs detectors with various geometries are presented and discussed. The detectors were reverse biased in fully depleted condition and in partially depleted condition (5 V reverse bias) in order to investigate the possibilities of integration with the standard bias values of read-out-integrated circuits. The results show that fabrication technology for nondedicated devices is still immature
- …