2,708 research outputs found
The Hyper-Kamiokande Experiment
The Hyper-Kamiokande experiment is a next generation underground water Cherenkov detector, based on the highly successful Super-Kamiokande experiment. It will serve as a far detector of a long baseline neutrino experiment for the J-PARC neutrino beam, with the main focus the determination of CP violation, and will also be a detector capable of observing - far beyond the sensitivity of the Super-Kamiokande detector - proton decay, atmospheric neutrinos, and neutrinos from astronomical sources
Expression of Interest: The Atmospheric Neutrino Neutron Interaction Experiment (ANNIE)
Neutron tagging in Gadolinium-doped water may play a significant role in
reducing backgrounds from atmospheric neutrinos in next generation proton-decay
searches using megaton-scale Water Cherenkov detectors. Similar techniques
might also be useful in the detection of supernova neutrinos. Accurate
determination of neutron tagging efficiencies will require a detailed
understanding of the number of neutrons produced by neutrino interactions in
water as a function of momentum transferred. We propose the Atmospheric
Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the
neutron yield of atmospheric neutrino interactions in gadolinium-doped water.
An innovative aspect of the ANNIE design is the use of precision timing to
localize interaction vertices in the small fiducial volume of the detector. We
propose to achieve this by using early production of LAPPDs (Large Area
Picosecond Photodetectors). This experiment will be a first application of
these devices demonstrating their feasibility for Water Cherenkov neutrino
detectors.Comment: Submitted for the January 2014 Fermilab Physics Advisory Committee
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Test and commissioning of the CARLOS control boards for the ALICE Silicon Drift Detectors
This paper presents the test strategy employed during the installation of the CARLOS end ladder boards developed for the Silicon Drift Detectors (SDD) of ALICE. Each CARLOS board compresses the data provided by the front-end electronics of one SDD and sends them via an optical link of 800 Mbit/s to the data concentrator card (CARLOSrx) located in the counting room. The paper describes the integration of the CARLOS boards in the final SDD system, including its cooling and mechanical support, the power supply distribution and the optical interconnections. The results of the tests performed after each step of the installation sequence are reported
INSPIRE: INvestigating stellar population in RElics: II. First data release (DR1)
[Context] The INvestigating Stellar Population In RElics (INSPIRE) is an ongoing project targeting 52 ultra-compact massive galaxies at 0.1 2) through a short and intense star formation burst, and then have evolved passively and undisturbed until the present day. Relics provide a unique opportunity to study the mechanisms of star formation at high-z. [Aims] INSPIRE is designed to spectroscopically confirm and fully characterise a large sample of relics, computing their number density in the redshift window 0.1 < z < 0.5 for the first time, thus providing a benchmark for cosmological galaxy formation simulations. In this paper, we present the INSPIRE Data Release (DR1), comprising 19 systems with observations completed in 2020. [Methods] We use the methods already presented in the INSPIRE Pilot, but revisiting the 1D spectral extraction. For the 19 systems studied here, we obtain an estimate of the stellar velocity dispersion, fitting the two XSH arms (UVB and VIS) separately at their original spectral resolution to two spectra extracted in different ways. We estimate [Mg/Fe] abundances via line-index strength and mass-weighted integrated stellar ages and metallicities with full spectral fitting on the combined (UVB+VIS) spectrum. [Results] For each system, different estimates of the velocity dispersion always agree within the errors. Spectroscopic ages are very old for 13/19 galaxies, in agreement with the photometric ones, and metallicities are almost always (18/19) super-solar, confirming the mass-metallicity relation. The [Mg/Fe] ratio is also larger than solar for the great majority of the galaxies, as expected. We find that ten objects formed more than 75% of their stellar mass (Mâ) within 3 Gyr from the big bang and classify them as relics. Among these, we identify four galaxies that had already fully assembled their Mâ by that time and are therefore 'extreme relics' of the ancient Universe. Interestingly, relics, overall, have a larger [Mg/Fe] and a more metal-rich stellar population. They also have larger integrated velocity dispersion values compared to non-relics (both ultra-compact and normal-size) of similar stellar mass. [Conclusions ]The INSPIRE DR1 catalogue of ten known relics is the largest publicly available collection, augmenting the total number of confirmed relics by a factor of 3.3, and also enlarging the redshift window. The resulting lower limit for the number density of relics at 0.17 < z < 0.39 is Ï âŒ 9.1 Ă 10-8 Mpc-3.CS is supported by an âHintze Fellowâ at the Oxford Centre for Astrophysical Surveys, which is funded through generous support from the Hintze Family Charitable Foundation. CS, CT, FLB, AG, and SZ acknowledge funding from the INAF PRIN-INAF 2020 program 1.05.01.85.11. AFM has received financial support through the Postdoctoral Junior Leader Fellowship Programme from âLa Caixaâ Banking Foundation (LCF/BQ/LI18/11630007). GD acknowledges support from CONICYT project Basal AFB-170002. DS is a member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne
INSPIRE: INvestigating Stellar Population in RElics: I. Survey presentation and pilot study
[Context] Massive elliptical galaxies are thought to form through a two-phase process. At early times (z > 2), an intense and fast starburst forms blue and disk-dominated galaxies. After quenching, the remaining structures become red, compact, and massive (i.e. red nuggets). Then, a time-extended second phase, which is dominated by mergers, causes structural evolution and size growth. Given the stochastic nature of mergers, a small fraction of red nuggets survive, without any interaction, massive and compact until today: these are relic galaxies. Since this fraction depends on the processes dominating the size growth, counting relics at low-z is a valuable way of disentangling between different galaxy evolution models. [Aims] In this paper, we introduce the INvestigating Stellar Population In RElics (INSPIRE) Project, which aims to spectroscopically confirm and fully characterise a large number of relics at 0:1z0:5. We focus here on the first results based on a pilot study targeting three systems, representative of the whole sample. [Methods] For these three candidates, we extracted 1D optical spectra over an aperture of r = 0:4000, which comprises 30% of the galaxiesâ light, and we obtained the line-of-sight integrated stellar velocity and velocity dispersion. We also inferred the stellar [/Fe] abundance from line-index measurements and mass-weighted age and metallicity from full-spectral fitting with single stellar population models. [Results] Two galaxies have large integrated stellar velocity dispersion values (250 km s), confirming their massive nature. They are populated by stars with super-solar metallicity and [/Fe]. Both objects have formed 80% of their stellar mass within a short (0:5:0 Gyr) initial star formation episode occurred only 1 Gyr after the Big Bang. The third galaxy has a more extendedstar formation history and a lower velocity dispersion. Thus we confirm two out of three candidates as relics. [Conclusions] This paper is the first step towards assembling the final INSPIRE catalogue that will set stringent lower limits on the number density of relics at z0:5, thus constituting a benchmark for cosmological simulations, and their predictions on number densities, sizes, masses, and dynamical characteristics of these objects.CS is supported by a Hintze Fellowship at the Oxford Centre for Astrophysical Surveys, which is funded through generous support from the Hintze Family Charitable Foundation. C.S. is also very grateful to Ortwin Gerhard and his ?Dynamics Group? at the Max-Planck-Institut f?r Extraterrestrische Physik (MPE, Garching by Munich) for interesting and constructive discussions. C.T., A.G., L.H. and S.Z. acknowledge funding from the INAF PRIN-SKA 2017 programme 1.05.01.88.04. G.D. acknowledges support from CONICYT project Basal AFB-170002. AFM has received financial support through the Postdoctoral Junior Leader Fellowship Programme from La Caixa Banking Foundation (LCF/BQ/LI18/11630007). N.R.N. acknowledges financial support from the One hundred top talent programme of Sun Yat-sen University, Grant N. 71000-18841229. D.S. is a member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne
Inclusive Measure of |V_ub| with the Analytic Coupling Model
By analyzing B -> X_u l nu_l spectra with a model based on soft-gluon
resummation and an analytic time-like QCD coupling, we obtain |V_ub| = (3.76
+-0.13 +- 0.22)*10^(-3), where the first and the second error refers to
experimental and theoretical errors, respectively. The V_ub value is obtained
from the available measured semileptonic branching fractions in limited regions
of the phase-space. The distributions in the lepton energy E_l, the hadron
invariant mass m_X, the light-cone momentum P_+ = E_X - p_X, together with the
double distributions in (m_X,q^2) and (E_l,s_h^max), are used to select the
phase-space regions. The q^2 is the dilepton squared momentum and s_h^max is
the maximal m_X^2 at fixed q^2 and E_l. The V_ub value obtained is in complete
agreement with the value coming from exclusive B decays and from an over-all
fit to the Standard Model parameters. We show that the slight disagreement (up
to +2 sigma) with respect to previous inclusive measurements is not related to
different choices for the b (and c) masses but to a different modelling of the
threshold (Sudakov) region.Comment: 19 pages, 2 figures, revised version accepted in Eur.Phys.J.
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