Study of RPC gas mixtures for the ARGO-YBJ experiment

The ARGO-YBJ experiment consists of a RPC carpet to be operated at the Yangbajing laboratory (Tibet, P.R. China), 4300 m a.s.l., and devoted to the detection of showers initiated by photon primaries in the energy range 100 GeV - 20 TeV. The measurement technique, namely the timing on the shower front with a few tens of particles, requires RPC operation with 1 ns time resolution, low strip multiplicity, high efficiency and low single counting rate. We have tested RPCs with many gas mixtures, at sea level, in order to optimize these parameters. The results of this study are reported.Comment: 6 pages, 3 figures. To be published in Nucl. Instr. Meth. A, talk given at the "5th International Workshop on RPCs and Related Detectors", Bari (Italy) 199

Performance of the PADME calorimeter prototype at the DAΦ\PhiNE BTF

The PADME experiment at the DA$\Phi$NE Beam-Test Facility (BTF) aims at searching for invisible decays of the dark photon by measuring the final state missing mass in the process $e^+e^- \to \gamma+ A'$, with $A'$ undetected. The measurement requires the determination of the 4-momentum of the recoil photon, performed using a homogeneous, highly segmented BGO crystals calorimeter. We report the results of the test of a 5$\times$5 crystals prototype performed with an electron beam at the BTF in July 2016

Characterization and Performance of PADME's Cherenkov-Based Small-Angle Calorimeter

The PADME experiment, at the Laboratori Nazionali di Frascati (LNF), in Italy, will search for invisible decays of the hypothetical dark photon via the process $e^+e^-\rightarrow \gamma A'$, where the $A'$ escapes detection. The dark photon mass range sensitivity in a first phase will be 1 to 24 MeV. We report here on measurement and simulation studies of the performance of the Small-Angle Calorimeter, a component of PADME's detector dedicated to rejecting 2- and 3-gamma backgrounds. The crucial requirement is a timing resolution of less than 200 ps, which is satisfied by the choice of PbF$_2$ crystals and the newly released Hamamatsu R13478UV photomultiplier tubes (PMTs). We find a timing resolution of 81 ps (with double-peak separation resolution of 1.8 ns) and a single-crystal energy resolution of 5.7%/$\sqrt{E}$ with light yield of 2.07 photo-electrons per MeV, using 100 to 400 MeV electrons at the Beam Test Facility of LNF. We also propose the investigation of a two-PMT solution coupled to a single PbF$_2$ crystal for higher-energy applications, which has potentially attractive features.Comment: 12 pages, 19 figures. v2: added section on radiation damage studie

Particle acoustic detection in gravitational wave aluminum resonant antennas

The results on cosmic rays detected by the gravitational antenna NAUTILUS have motivated an experiment (RAP) based on a suspended cylindrical bar, which is made of the same aluminum alloy as NAUTILUS and is exposed to a high energy electron beam. Mechanical vibrations originate from the local thermal expansion caused by warming up due to the energy lost by particles crossing the material. The aim of the experiment is to measure the amplitude of the fundamental longitudinal vibration at different temperatures. We report on the results obtained down to a temperature of about 4 K, which agree at the level of about 10% with the predictions of the model describing the underlying physical process.Comment: RAP experiment, 16 pages, 7 figure

Evaluation of the nutritional status of infants from mothers tested positive to HIV/AIDS in the health district of Dschang, Cameroon

INTRODUCTION: Poor infant feeding practices are common in Africa, resulting in physical and intellectual developmental impairments. Good feeding practices are crucial, especially in the first year of growth. HIV/AIDS has worsened the clinical and nutritional status of both mothers and their children, exacerbating high rates of malnutrition. The aim of this study was to assess by participative approach, the nutritional status of infants from mothers tested positive to HIV in the health district of Dschang. METHODS: This is a cross sectional study with a period of recruitment of 2 years (2010-2012). Data Collection was done by the aim of a personal slip followed by training to strengthen the nutritional and hygienic capacity of targeted parents. Height and weight of infants were measured and body mass index (BMI) calculated. RESULTS: Significant difference (p ≤ 0.05) was noticed in height-for-age z-score (HAZ) of girls aged between 1 to 2 years compared to 1-year old girls as well as to boys of all ages, defining them as stunted. Furthermore, the weight-for-age z-score (WAZ) results indicate that both girls and boys of all age are in moderate state of malnutrition. The results of BMI thinness classified according to gender and age groups, indicates that most infants (68/130, 52.3%) showed grade 2 thinness predominantly in 2-years old both boys and girls. However, no participants fall within the normal category for age and sex, as well as overweight and obesity categories. CONCLUSION: Undernutrition exists among infants from mothers tested positive to HIV residing in Dschang, as most of the infants are underweight, and malnourished

On the backward bifurcation of a vaccination model with nonlinear incidence

A compartmental epidemic model, introduced by Gumel and Moghadas [1], is considered. The model incorporates a nonlinear incidence rate and an imperfect preventive vaccine given to susceptible individuals. A bifurcation analysis is performed by applying the bifurcation method introduced in [2], which is based on the use of the center manifold theory. Conditions ensuring the occurrence of backward bifurcation are derived. The obtained results are numerically validated and then discussed from both the mathematical and the epidemiological perspective

Commissioning Status of the CTF3 Delay Loop

The CLIC Test Facility CTF3, built at CERN by an international collaboration, aims at demonstrating the linear collider by 2010. In particular, one of the main goals is to study the generation of high-current electron pulses by interleaving bunch trains in delay lines and rings using transverse RF deflectors. This will be done in the 42 m long delay loop, built under the responsibility of INFN/LNF, and the 84 m long combiner ring that will follow it. The delay loop installation was completed and its commissioning started at the end of 2005. In this paper the commissioning results are presented, including the first tests of beam recombination