A new approach in modeling the response of RPC detectors

The response of RPC detectors is highly sensitive to environmental variables. A novel approach is presented to model the response of RPC detectors in a variety of experimental conditions. The algorithm, based on Artificial Neural Networks, has been developed and tested on the CMS RPC gas gain monitoring system during commissioning

The ARGO-YBJ Experiment Progresses and Future Extension

Gamma ray source detection above 30TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1km2 is proposed to boost the sensitivity. Hybrid detection with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual specie. Fluorescence light detector array will extend the spectrum measurement above 100PeV where the second knee is located. An energy scale determined by balloon experiments at 10TeV will be propagated to ultra high energy cosmic ray experiments

Effects of charged Higgs bosons in the deep inelastic process \nu_{\tau} {\cal N} \to \tau^- X and the possibility of detecting tau-neutrinos at cosmic neutrino detectors

We study the deep inelastic process $\nu_{\tau} + {\cal N} \to \tau^{-} + X$ (with ${\cal N} \equiv (n+p)/2$ an isoscalar nucleon), in the context of the two Higgs doublet model type II (2HDM(II)). We discuss the contribution to the total cross section of diagrams, in which a charged Higgs boson is exchanged. We present results which show the strong dependence of such contribution on $\tan\beta$ and $M_{H^{\pm}}$. We show that in the region $50 \leq \tan\beta \leq 200$ and 90 GeV $\leq M_{H^{\pm}}\leq$ 600 GeV with the additional experimental constraint on the involved model parameters $M_{H^{\pm}} \geq 1.5 \times \tan\beta$ GeV, the contribution of the charged Higgs boson exchange diagrams to the cross section of the charged current inclusive $\nu_{\tau} {\cal N}$ collision can become important. We obtain that this contribution for an inclusive dispersion generated through the collision of an ultrahigh energy tau-neutrino with $E_{\nu} \approx 10^{20}$ eV on a target nucleon can be larger than the value of the contribution of the $W^{\pm}$ exchange diagrams, provided that $M_{H^{\pm}} \approx 300$ GeV and $\tan\beta \approx 200$. Such enhancement and the induced variation on the mean inelasticity $^{CC}$ could lead to sizeable effects in the acceptance of cosmic tau-neutrino detectors at experiments such as HiRes, PAO, and the CRTNT, which are anchored to the ground, and at experiments such as EUSO and OWL, which are proposed to orbit around the Earth.Comment: 18 pages, 2 figures, 8 table

Gamma-Ray Astronomy with ARGO-YBJ

ARGO-YBJ is a full coverage air shower array located at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm2) recording data with a duty cycle 85% and an energy threshold of a few hundred GeV. In this paper the latest results in Gamma-Ray Astronomy are summarized

First measurements with the ARGO-YBJ detector

The detection of small size air showers at high altitude allows the search for γ-ray point sources at few hundreds GeV energy threshold. The ARGO-YBJ experiment, currently under construction at the Yangbajing Cosmic Ray Laboratory (4300 m a.s.l.), has been designed to meet these requirements by exploiting the RPC technology and a dedicated DAQ system based on a custom high-speed read-out architecture. About 1600 m2 of detector have been instrumented and put into operation for calibration runs devoted to test the performance of the individual components and their integrated operation. Events collected with a ’shower mode’ trigger have been recorded to check the consistency of physics data. We present the current status of the experiment and report on future prospects

The Trigger System of the ARGO-YBJ detector

The ARGO-YBJ experiment has been designed to detect air shower events over a large size scale and with an energy threshold of a few hundreds GeV. The building blocks of the ARGO-YBJ detector are single-gap Resistive Plate Counters (RPCs). The trigger logic selects the events on the basis of their hit multiplicity. Inclusive triggers as well as dedicated triggers for specific physics channels or calibration purposes have been developed. This paper describes the architecture and the main features of the trigger system

Background radioactivity in the scaler mode technique of the Argo-YBJ detector

ARGO-YBJ is an extensive air shower detector located at the Yangbajing Cosmic Ray Laboratory (4300 m a.s.l., 606 g cm−2 atmospheric depth, Tibet, China). It is made by a single layer of Resistive Plate Chambers (RPCs, total surface 6700 m2) grouped into 153 units called “clusters”. The low energy threshold of the experiment is obtained using the ”scaler operation mode”, counting all the particles hitting the detector without reconstruction of the shower size and arrival direction. For each cluster the signals generated by these particles are put in coincidence in a narrow time window (150 ns) and read by four independent scaler channels, giving the counting rates of channel 1, 2, 3 and 4 hits. The study of these counting rates pointed out a different behavior of channel 1 respect to the higher multiplicity channels: while the MC simulations can account fairly well for the coincident counting rates, the expectation for channel 1 is sensibly less than the measured value. Moreover, the regression coefficient with the atmospheric pressure for channel 1 is also about half of the value measured for the coincident counting rates: seemingly half of these counts did not cross the atmosphere. Measurements of the natural radioactivity background in the air of the detector hall and a MC simulation to estimate its contribution on our counting rates are presented and discussed

The status of the ARGO experiment at YBJ

The ARGO-YBJ experiment, located at Yangbajing, Tibet, China, performed by a wide Sino-Italian collaboration, is designed to study cosmic rays, sub-TeV gamma ray sources and GeV Gamma Ray Burst (GRB) emission in the northern hemisphere, by means of detecting small size EAS (Extensive Air Shower) using a full coverage RPC (Resistive Plate Chamber) carpet. The central carpet of the detector is installed and put into operation to date, with 1900 m^2 of the carpet already operating since December 2004. With a trigger multiplicity of ≥60 hits, corresponding to a primary mode energy of 2 TeV, the angular resolution of EAS measurements is < 1 degree for showers with more than 500 recorded hits. We report the preliminary results of data taking performed during 2005: the all-sky survey for gamma ray sources and the search for GRBs, as well as the cosmic ray spectrum up to about 100 TeV. The Forbush decrease of the cosmic ray flux during January, 2005 is observed using the ARGO data

Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment

The proton-air cross section in the energy range 1-100 TeV has been measured by the ARGO-YBJ cosmic ray experiment. The analysis is based on the flux attenuation for different atmospheric depths (i.e. zenith angles) and exploits the detector capabilities of selecting the shower development stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of shower fluctuations, the contribution of heavier primaries and the uncertainties of the hadronic interaction models, have been taken into account. The results have been used to estimate the total proton-proton cross section at center of mass energies between 70 and 500 GeV, where no accelerator data are currently available

Gamma ray bursts monitoring with the ARGO-YBJ experiment in scaler mode

We report on the search for Gamma Ray Bursts (GRBs) in the energy range 1−100 GeV in coincidence with the prompt emission detected by satellites, using the Astrophysical Radiation Ground-based Observatory at YangBa-Jing ARGO-YBJ). With its big active surface (6700 m 2) and large field of view (2 sr) the ARGO-YBJ air shower detector is particularly suitable to detect unpredictable and short duration events such as GRBs. The search has been performed using the single particle technique in time coincidence with satellite detections both for single events and for the piling up of all the GRBs in time and in phase. Between November 2004 and June 2010 115 GRBs, detected by different satellites (mainly Swift and Fermi), occurred within the field of view of ARGO-YBJ. For 94 of these we searched for a counterpart in the ARGO-YBJ data finding no statistically significant emission. Search methods and results are discussed