The Astrophysical Radiation with Ground-based Observatory at Yang Ba Jing (ARGO-YBJ) detector is an extensive air shower array that has been used to monitor the northern gamma -ray sky at energies ...above 0.3 TeV from 2007 November to 2013 January. In this paper, we present the results of a sky survey in the declination band from -10degrees to 70degrees, using data recorded over the past five years. With an integrated sensitivity ranging from 0.24 to ~1 Crab units depending on the declination, six sources have been detected with a statistical significance greater than five standard deviations. Several excesses are also reported as potential gamma -ray emitters. The features of each source are presented and discussed. Additionally, 95% confidence level upper limits of the flux from the investigated sky region are shown. Specific upper limits for 663 GeV gamma -ray active galactic nuclei inside the ARGO-YBJ field of view are reported. The effect of the absorption of gamma -rays due to the interaction with extragalactic background light is estimated.
The Sun blocks cosmic-ray particles from outside the solar system, forming a detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ experiment in Tibet. Because the cosmic-ray ...particles are positively charged, the magnetic field between the Sun and the Earth deflects them from straight trajectories and results in a shift of the shadow from the true location of the Sun. Here, we show that the shift measures the intensity of the field that is transported by the solar wind from the Sun to the Earth.
The potential offered by the cloud paradigm is often limited by technical issues, rules and regulations. In particular, the activities related to the design and deployment of the Infrastructure as a ...Service (IaaS) cloud layer can be difficult to apply and time-consuming for the infrastructure maintainers. In this paper the research activity, carried out during the Open City Platform (OCP) research project 1, aimed at designing and developing an automatic tool for cloud-based IaaS deployment is presented. Open City Platform is an industrial research project funded by the Italian Ministry of University and Research (MIUR), started in 2014. It intends to research, develop and test new technological solutions open, interoperable and usable on-demand in the field of Cloud Computing, along with new sustainable organizational models that can be deployed for and adopted by the Public Administrations (PA). The presented work and the related outcomes are aimed at simplifying the deployment and maintenance of a complete IaaS cloud-based infrastructure.
After the successful LHC data taking in Run-I and in view of the future runs, the LHC experiments are facing new challenges in the design and operation of the computing facilities. The computing ...infrastructure for Run-II is dimensioned to cope at most with the average amount of data recorded. The usage peaks, as already observed in Run-I, may however originate large backlogs, thus delaying the completion of the data reconstruction and ultimately the data availability for physics analysis. In order to cope with the production peaks, CMS - along the lines followed by other LHC experiments - is exploring the opportunity to access Cloud resources provided by external partners or commercial providers. Specific use cases have already been explored and successfully exploited during Long Shutdown 1 (LS1) and the first part of Run 2. In this work we present the proof of concept of the elastic extension of a CMS site, specifically the Bologna Tier-3, on an external OpenStack infrastructure. We focus on the "Cloud Bursting" of a CMS Grid site using a newly designed LSF configuration that allows the dynamic registration of new worker nodes to LSF. In this approach, the dynamically added worker nodes instantiated on the OpenStack infrastructure are transparently accessed by the LHC Grid tools and at the same time they serve as an extension of the farm for the local usage. The amount of resources allocated thus can be elastically modeled to cope up with the needs of CMS experiment and local users. Moreover, a direct access integration of OpenStack resources to the CMS workload management system is explored. In this paper we present this approach, we report on the performances of the on-demand allocated resources, and we discuss the lessons learned and the next steps.
The search for gamma-ray burst (GRB) emission in the energy range of 1-100 GeV in coincidence with the satellite detection has been carried out using the Astrophysical Radiation with Ground-based ...Observatory at YangBaJing (ARGO-YBJ) experiment. The high-altitude location (4300 m a.s.l.), the large active surface (~6700 m super(2) of Resistive Plate Chambers), the wide field of view (~2 sr, limited only by the atmospheric absorption), and the high duty cycle (>86%) make the ARGO-YBJ experiment particularly suitable to detect short and unexpected events like GRBs. With the scaler mode technique, i.e., counting all the particles hitting the detector with no measurement of the primary energy and arrival direction, the minimum threshold of ~1 GeV can be reached, overlapping the direct measurements carried out by satellites. During the experiment lifetime from 2004 December 17 to 2013 February 7, a total of 206 GRBs occurring within the ARGO-YBJ field of view (zenith angle theta < or =, slant 45degrees) have been analyzed. This is the largest sample of GRBs investigated with a ground-based detector. Two light curve models have been assumed and since in both cases no significant excess has been found, the corresponding fluence upper limits in the 1-100 GeV energy region have been derived, with values as low as 10 super(-5) erg cm super(-2). The analysis of a subset of 24 GRBs with known redshift has been used to constrain the fluence extrapolation to the GeV region together with possible cutoffs under different assumptions on the spectrum.
ABSTRACT The events recorded by ARGO-YBJ in more than five years of data collection have been analyzed to determine the diffuse gamma-ray emission in the Galactic plane at Galactic longitudes 25° < l ...< 100° and Galactic latitudes . The energy range covered by this analysis, from ∼350 GeV to ∼2 TeV, allows the connection of the region explored by Fermi with the multi-TeV measurements carried out by Milagro. Our analysis has been focused on two selected regions of the Galactic plane, i.e., 40° < l < 100° and 65° < l < 85° (the Cygnus region), where Milagro observed an excess with respect to the predictions of current models. Great care has been taken in order to mask the most intense gamma-ray sources, including the TeV counterpart of the Cygnus cocoon recently identified by ARGO-YBJ, and to remove residual contributions. The ARGO-YBJ results do not show any excess at sub-TeV energies corresponding to the excess found by Milagro, and are consistent with the predictions of the Fermi model for the diffuse Galactic emission. From the measured energy distribution we derive spectral indices and the differential flux at 1 TeV of the diffuse gamma-ray emission in the sky regions investigated.
The extended TeV gamma-ray source ARGO J2031+4157 (or MGRO J2031+41) is positionally consistent with the Cygnus Cocoon discovered by Fermi-LAT at GeV energies in the Cygnus superbubble. Reanalyzing ...the ARGO-YBJ data collected from 2007 November to 2013 January, the angular extension and energy spectrum of ARGO J2031+4157 are evaluated. After subtracting the contribution of the overlapping TeV sources, the ARGO-YBJ excess map is fitted with a two-dimensional Gaussian function in a square region of 10degrees x 10degrees, finding a source extension sigma sub(ext)= 1degrees.8 + or - 0degrees.5. The observed differential energy spectrum is dN/dE = (2.5 + or - 0.4) x 10 super(-11) (E/1 TeV) super(-2.6+ or -0.3) photons cm super(-2) s super(-1) TeV super(-1), in the energy range 0.2-10 TeV. The angular extension is consistent with that of the Cygnus Cocoon as measured by Fermi-LAT and the spectrum also shows a good connection with the one measured in the 1-100 GeV energy range. These features suggest to identify ARGO J2031+4157 as the counterpart of the Cygnus Cocoon at TeV energies. The Cygnus Cocoon, located in the star-forming region of Cygnus X, is interpreted as a cocoon of freshly accelerated cosmic rays related to the Cygnus superbubble. The spectral similarity with supernova remnants (SNRs) indicates that the particle acceleration inside a superbubble is similar to that in an SNR. The spectral measurements from 1 GeV to 10 TeV allows for the first time to determine the possible spectrum slope of the underlying particle distribution. A hadronic model is adopted to explain the spectral energy distribution.
Resistive Plate Chambers have largely been used in High Energy Physics and Cosmic Ray research. In view of using this detector for calorimetry applications it is important to know the maximum ...measurable particle density, or its intrinsic linearity limit, which is tightly related to the dimension of the discharge region. In this paper we report the results of measurements performed at the Beam Test Facility (INFN National Laboratory of Frascati, Italy) where the intrinsic linearity of bakelite RPCs operated in streamer mode has been tested at different impinging particle densities.
The extended gamma-ray source MGRO J1908+06, discovered by the Milagro air shower detector in 2007, has been observed for ~4 years by the ARGO-YBJ experiment at TeV energies, with a statistical ...significance of 6.2 standard deviations. The peak of the signal is found at a position consistent with the pulsar PSR J1907+0602. Parameterizing the source shape with a two-dimensional Gauss function, we estimate an extension of sigma sub(ext) = 0.degrees 49 + or - 0.degrees 22, which is consistent with a previous measurement by the Cherenkov Array H.E.S.S. The observed energy spectrum is dN/dE = 6.1 + or - 1.4 x 10 super(-13) (E/4 TeV) super(-2.54+ or -0.36) photons cm super(-2) s super(-1) TeV super(-1), in the energy range of ~1-20 TeV. The measured gamma-ray flux is consistent with the results of the Milagro detector, but is ~2-3 times larger than the flux previously derived by H.E.S.S. at energies of a few TeV. The continuity of the Milagro and ARGO-YBJ observations and the stable excess rate observed by ARGO-YBJ and recorded in four years of data support the identification of MGRO J1908+06 as the steady powerful TeV pulsar wind nebula of PSR J1907+0602, with an integrated luminosity over 1 TeV ~ 1.8 times the luminosity of the Crab Nebula.
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