M. Panareo

Università del Salento, Lecce, Apulia, Italy

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Publications (106)203.33 Total impact

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    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{\deg} < l < 100{\deg} 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{\deg} < l < 100{\deg} and 65{\deg} < l < 85{\deg} (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 Astrophysical Journal 07/2015; 806(1). DOI:10.1088/0004-637X/806/1/20 · 6.28 Impact Factor
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    ABSTRACT: The search for Gamma Ray Burst (GRB) emission in the energy range 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 ($\sim$ 6700 m$^2$ of Resistive Plate Chambers), the wide field of view ($\sim 2~$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 $\sim$ 1 GeV can be reached, overlapping the direct measurements carried out by satellites. During the experiment lifetime, from December 17, 2004 to February 7, 2013, a total of 206 GRBs occurring within the ARGO-YBJ field of view (zenith angle $\theta$ $\le$ 45$^{\circ}$) have been analyzed. This is the largest sample of GRBs investigated with a ground-based detector. Two lightcurve 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$^{-5}~$erg cm$^{-2}$. 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.
    The Astrophysical Journal 02/2015; 794(1). DOI:10.1088/0004-637X/794/1/82 · 6.28 Impact Factor
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    ABSTRACT: The measurement of cosmic ray energy spectra, in particular for individual species, is an essential approach in finding their origin. Locating the "knees" of the spectra is an important part of the approach and has yet to be achieved. Here we report a measurement of the mixed Hydrogen and Helium spectrum using the combination of the ARGO-YBJ experiment and of a prototype Cherenkov telescope for the LHAASO experiment. A knee feature at 640+/-87 TeV, with a clear steepening of the spectrum, is observed. This gives fundamental inputs to galactic cosmic ray acceleration models.
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    ABSTRACT: The ARGO-YBJ experiment is an air shower detector for gamma ray astronomy and cosmic ray studies with an energy threshold of similar to 500 GeV. Working in "single particle mode", i.e. counting the single particles hitting the detector at fixed time intervals, ARGO-YBJ can monitor cosmic ray and gamma ray transients at energies of a few GeV. The single particle counting rate is modulated by the atmospheric pressure and temperature, and is affected by the local radioactivity from soil and air. Among the radioactive elements, radon gas is of particular importance since its concentration in air can vary significantly, according to environmental conditions. In this paper we evaluate the contribution of the radon daughter gamma ray emitters to the single particle counting rate measured by ARGO-YBJ. According to our analysis, the radon gas contribution is roughly 1-2%, producing a counting rate modulation of the same order of magnitude of the atmospheric effects.
    Radiation Measurements 09/2014; 68:42-48. DOI:10.1016/j.radmeas.2014.07.006 · 1.14 Impact Factor
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    ABSTRACT: 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 November 2007 to January 2013, 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 $10^{\circ}\times 10^{\circ}$, finding a source extension $\sigma_{ext}$= 1$^{\circ}$.8$\pm$0$^{\circ}$.5. The observed differential energy spectrum is $dN/dE =(2.5\pm0.4) \times 10^{-11}(E/1 TeV)^{-2.6\pm0.3}$ photons cm$^{-2}$ s$^{-1}$ TeV$^{-1}$, 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 indicates that the particle acceleration inside a superbubble is similar to that in a 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.
    The Astrophysical Journal 06/2014; 790(2). DOI:10.1088/0004-637X/790/2/152 · 6.28 Impact Factor
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    ABSTRACT: Low pressure helium/hydrocarbons mixtures are a key ingredient for next generation ultra-light drift chambers. Besides the obvious advantage of limiting the contribution to the momentum measurement due to multiple scattering, the operation at low pressure allows for a broad range of the drift chamber working parameters like drift velocity, diffusion, specific ionization and gas gain. Low pressure operation is of particular advantage for experiments where the tracking detector operates in vacuum. We present our campaign to characterize electron drift, primary ionization yield, gas gain, stability and the relative spatial resolution in helium based mixtures at absolute pressures down to 100 mbar.
    Nuclear Physics B - Proceedings Supplements 03/2014; s 248–250:131–133. DOI:10.1016/j.nuclphysbps.2014.02.026 · 0.88 Impact Factor
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    ABSTRACT: We developed a high performance full chain for drift chamber signals processing. The Front End electronics is a multistage amplifier board based on high performance commercial devices. In addition a fast readout algorithm for Cluster Counting and Timing purposes has been implemented on a Xilinx-Virtex 4 core FPGA. The algorithm analyzes and stores data coming from a Helium based drift tube and represents the outcome of balancing between efficiency and high speed performance.
    Nuclear Physics B - Proceedings Supplements 03/2014; s 248–250:140–142. DOI:10.1016/j.nuclphysbps.2014.02.029 · 0.88 Impact Factor
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    ABSTRACT: The energy spectrum of cosmic Hydrogen and Helium nuclei has been measured, below the so-called "knee", by using a hybrid experiment with a wide field-of-view Cherenkov telescope and the Resistive Plate Chamber (RPC) array of the ARGO-YBJ experiment at 4300 m above sea level. The Hydrogen and Helium nuclei have been well separated from other cosmic ray components by using a multi-parameter technique. A highly uniform energy resolution of about 25% is achieved throughout the whole energy range (100 TeV - 700 TeV). The observed energy spectrum is compatible with a single power law with index gamma=-2.63+/-0.06.
    Chinese Physics C 01/2014; 38(4). DOI:10.1088/1674-1137/38/4/045001 · 0.82 Impact Factor
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    ABSTRACT: We studied the radiative muon decay $\mu^+ \to e^+\nu\nu\gamma$ by using for the first time an almost fully polarized muon beam. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in the MEG experiment and measured the branching ratio B($\mu^+ \to e^+\nu\nu\gamma$) = (6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV, consistent with the Standard Model prediction. Moreover, the precise measurement of this decay mode provides the basic tool for the timing calibration and a strong quality check of the complete MEG experiment in the search for $\mu^+ \to e^+\gamma$ process.
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    ABSTRACT: The 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 $-10^{\circ}$ to $70^{\circ}$, using data recorded over the past five years. With an integrated sensitivity ranging from 0.24 to $\sim$1 Crab units depending on the declination, six sources have been detected with a statistical significance greater than 5 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 AGNs 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 Astrophysical Journal 11/2013; 779(1). DOI:10.1088/0004-637X/779/1/27 · 6.28 Impact Factor
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    ABSTRACT: Measuring the anisotropy of the arrival direction distribution of cosmic rays provides important information on the propagation mechanisms and the identification of their sources. In fact, the flux of cosmic rays is thought to be dependent on the arrival direction only due to the presence of nearby cosmic ray sources or particular magnetic-field structures. Recently, the observation of unexpected excesses at TeV energy down to an angular scale as narrow as $\ensuremath{\sim}10\ifmmode^\circ\else\textdegree\fi{}$ raised the possibility that the problem of the origin of Galactic cosmic rays may be addressed by studying the anisotropy. The ARGO-YBJ experiment is a full-coverage extensive air showers array, sensitive to cosmic rays with the energy threshold of a few hundred GeV. Searching for small-size deviations from the isotropy, the ARGO-YBJ Collaboration explored the declination region $\ensuremath{\delta}\ensuremath{\sim}\ensuremath{-}20\ifmmode^\circ\else\textdegree\fi{}\char21{}80\ifmmode^\circ\else\textdegree\fi{}$, making use of about $3.7\ifmmode\times\else\texttimes\fi{}{10}^{11}$ events collected from November 2007 to May 2012. In this paper, the detection of different significant (up to 13 standard deviations) medium-scale anisotropy regions in the arrival directions of cosmic rays is reported. The observation was performed with unprecedented detail. The relative excess intensity with respect to the isotropic flux extends up to ${10}^{\ensuremath{-}3}$. The maximum excess occurs for proton energies of 10\char21{}20 TeV, suggesting the presence of unknown features of the magnetic fields the charged cosmic rays propagate through, or some contribution of nearby sources never considered so far. The observation of new weaker few-degree excesses throughout the sky region $195\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}\mathrm{R}.\mathrm{A}.\ensuremath{\le}290\ifmmode^\circ\else\textdegree\fi{}$ is reported for the first time.
    Physical Review D 10/2013; 88(8). DOI:10.1103/PhysRevD.88.082001 · 4.86 Impact Factor
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    ABSTRACT: a b s t r a c t We propose a new photocathode configuration which presents the quantum efficiency and work function of yttrium (Y) and at the same time preserves all of the advantages of copper (Cu) when inserted into a radio-frequency gun. The configuration consists of a disk of Y covered by a coating of Cu deposited using the pulsed laser ablation technique, while masking the central part of the Y disk by a shield making the photoemission directly from the Y bulk possible. The new device was characterised by scanning electron microscopy to deduce the morphology and by X-ray diffraction to obtain structure information on both Cu film and Y substrate. The electrical resistivity of the Cu film was also measured obtaining a value slightly greater than that of bulk high purity Cu. & 2013 Published by Elsevier B.V.
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    ABSTRACT: Pb thin films were deposited on Nb substrates by means of pulsed laser deposition (PLD) with UV radiation (248 nm), in two different ablation regimes: picosecond (5 ps) and subpicosecond (0.5 ps). Granular films with grain size on the micron scale have been obtained, with no evidence of large droplet formation. All films presented a polycrystalline character with preferential orientation along the (111) crystalline planes. A maximum quantum efficiency (QE) of 7.3×10-5 (at 266 nm and 7 ns pulse duration) was measured, after laser cleaning, demonstrating good photoemission performance for Pb thin films deposited by ultrashort PLD. Moreover, Pb thin film photocathodes have maintained their QE for days, providing excellent chemical stability and durability. These results suggest that Pb thin films deposited on Nb by ultrashort PLD are a noteworthy alternative for the fabrication of photocathodes for superconductive radio-frequency electron guns. Finally, a comparison with the characteristics of Pb films prepared by ns PLD is illustrated and discussed.
    Physical Review Special Topics - Accelerators and Beams 09/2013; 16(9). DOI:10.1103/PhysRevSTAB.16.093401 · 1.52 Impact Factor
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    ABSTRACT: We present results on the measurements of gas gain for gas mixtures at absolute pressure below the atmospheric pressure, down to 100 mbar, and their relative stability. Besides the obvious advantage of further limiting the contribution to the momentum measurement due to multiple scattering, the operation at low pressure allows for a fine tuning of the working parameters of a drift chamber like drift velocity, diffusion and specific ionization. Furthermore, such a possibility is of particular interest for experiments like the direct muon to electron conversion experiment Mu2e at Fermilab, where the tracking detector needs to operate in vacuum. Plans for extending the measurements to transport parameters, like drift velocity and diffusion, will also be presented.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 08/2013; 718:409-411. DOI:10.1016/j.nima.2012.10.005 · 1.32 Impact Factor
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    ABSTRACT: CORAM (COsmic RAy Mission) is an outreach program carried out by INFN and the University of Salento in close collaboration with high schools. Students and their teachers are involved in the design, construction, test and operation of detectors for the measurement of several properties of the cosmic ray flux. The results of a set of measurements, made with a first detector prototype at different altitudes and underground, will be described.
    Nuclear Physics B - Proceedings Supplements 06/2013; s 239–240:245–249. DOI:10.1016/j.nuclphysbps.2013.05.037 · 0.88 Impact Factor
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    ABSTRACT: The Extreme Energy Events Project is an experiment for the detection of Extensive Air Showers which exploits the Multigap Resistive Plate Chamber technology. At the moment 40 EEE muon telescopes, distributed all over the Italian territory, are taking data, allowing the relative analysis to produce the first interesting results, which are reported here. Moreover, this Project has a strong added value thanks to its effectiveness in terms of scientific communication, which derives from the peculiar way it was planned and carried on.
    European Physical Journal Plus 06/2013; 128(6). DOI:10.1140/epjp/i2013-13062-8 · 1.48 Impact Factor
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    ABSTRACT: The analysis of a combined data set, totaling 3.6×10^{14} stopped muons on target, in the search for the lepton flavor violating decay μ^{+}→e^{+}γ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7×10^{-13} (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.
    Physical Review Letters 05/2013; 110(20):201801. DOI:10.1103/PhysRevLett.110.201801 · 7.51 Impact Factor
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    ABSTRACT: The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay μ +→e+γ by using one of the most intense continuous μ + beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.
    European Physical Journal C 04/2013; 73(4). DOI:10.1140/epjc/s10052-013-2365-2 · 5.44 Impact Factor
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    ABSTRACT: The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\ by using one of the most intense continuous $\mu^+$ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.
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    ABSTRACT: We report the observation of a very high energy \gamma-ray source, whose position is coincident with HESS J1841-055. This source has been observed for 4.5 years by the ARGO-YBJ experiment from November 2007 to July 2012. Its emission is detected with a statistical significance of 5.3 standard deviations. Parameterizing the source shape with a two-dimensional Gaussian function we estimate an extension \sigma=(0.40(+0.32,-0.22}) degree, consistent with the HESS measurement. The observed energy spectrum is dN/dE =(9.0-+1.6) x 10^{-13}(E/5 TeV)^{-2.32-+0.23} photons cm^{-2} s^{-1} TeV^{-1}, in the energy range 0.9-50 TeV. The integral \gamma-ray flux above 1 TeV is 1.3-+0.4 Crab units, which is 3.2-+1.0 times the flux derived by HESS. The differences in the flux determination between HESS and ARGO-YBJ, and possible counterparts at other wavelengths are discussed.
    The Astrophysical Journal 03/2013; 767(2). DOI:10.1088/0004-637X/767/2/99 · 6.28 Impact Factor

Publication Stats

774 Citations
203.33 Total Impact Points

Institutions

  • 1996–2015
    • Università del Salento
      • • Department of Mathematics and Physics "Ennio De Giorgi"
      • • Department of Engineering for Innovation
      Lecce, Apulia, Italy
  • 1994–2014
    • INFN - Istituto Nazionale di Fisica Nucleare
      Frascati, Latium, Italy
  • 2001
    • Università di Pisa
      Pisa, Tuscany, Italy
  • 1999
    • University of Rome Tor Vergata
      • Dipartimento di Fisica
      Roma, Latium, Italy
  • 1998
    • Università Degli Studi Roma Tre
      • Department of Mathematics and Physics
      Roma, Latium, Italy
  • 1993
    • University of Houston
      Houston, Texas, United States
  • 1991
    • Fermi National Accelerator Laboratory (Fermilab)
      Batavia, Illinois, United States