Omega and eta meson production in p+p reactions at E_{kin} = 3.5 GeV

We report on the exclusive production of omega and eta mesons in p+p reactions at 3.5 GeV beam kinetic energy. Production cross sections, angular distributions and Dalitz plots of both mesons were determined. Moreover, the relative contribution of the N(1535) resonance in eta production at this energy was evaluated. We conclude that eta mesons produced via N(1535) exihibit an isotropic angular distribution, whereas those produced directly show a strong anisotropic distribition. omega mesons show a slightly anisotropic angular distribition.Comment: 5 pages, 6 figures, proceedings of the 11th International Workshop on Meson Production, Properties and Interaction, Krak\'ow, Poland, 10 - 15 June 201

On the muon neutrino mass

During the runs of the PS 179 experiment at LEAR of CERN, we photographed an event of antiproton-Ne absorption, with a complete pi+ -> mu+ ->e+ chain. From the vertex of the reaction a very slow energy pi+ was emitted. The pi+ decays into a mu+ and subsequently the mu+ decays into a positron. At the first decay vertex a muon neutrino was emitted and at the second decay vertex an electron neutrino and a muon antineutrino. Measuring the pion and muon tracks and applying the momentum and energy conservation and using a classical statistical interval estimator, we obtained an experimental upper limit for the muon neutrino mass: m_nu < 2.2 MeV at a 90% confidence level. A statistical analysis has been performed of the factors contributing to the square value of the neutrino mass limit.Comment: 18 pages, 5 eps figure

X-ray reprocessing in Seyfert Galaxies: simultaneous XMM-Newton/BeppoSAX observations

We selected a sample of eight bright unobscured (at least at the iron line energy) Seyfert Galaxies observed simultaneously by XMM-Newton and BeppoSAX, taking advantage of the complementary characteristics of the two missions. The main results of our analysis can be summarized as follows: narrow neutral iron lines are confirmed to be an ubiquitous component in Seyfert spectra; none of the analyzed sources shows unambiguously a broad relativistic iron line; all the sources of our sample (with a single exception) show the presence of a Compton reflection component; emission lines from ionized iron are observed in some sources; peculiar weak features around 5-6 keV (possibly arising from rotating spots on the accretion disk) are detected in two sources. The scenario emerging from these results strongly requires some corrections for the classical model of reprocessing from the accretion disk. As for materials farther away from the Black Hole, our results represent a positive test for the Unification Model, suggesting the presence of the torus in (almost) all sources, even if unobscured.Comment: Accepted for publication in A&

The evolution of the spatially-resolved metal abundance in galaxy clusters up to z=1.4

We present the combined analysis of the metal content of 83 objects in the redshift range 0.09-1.39, and spatially-resolved in the 3 bins (0-0.15, 0.15-0.4, >0.4) R500, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008) and Baldi et al. (2012). We use the pseudo-entropy ratio to separate the Cool-Core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the Non-Cool-Core systems. The average, redshift-independent, metal abundance measured in the 3 radial bins decrease moving outwards, with a mean metallicity in the core that is even 3 (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989) estimated at r>0.4 R500 in CC (NCC) objects. We find that the values of the emission-weighted metallicity are well-fitted by the relation $Z(z) = Z_0 (1+z)^{-\gamma}$ at given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05-0.15, is observed below 0.4 R500. The nominal best-fit value of $\gamma$ is significantly different from zero in the inner cluster regions ($\gamma = 1.6 \pm 0.2$) and in CC clusters only. These results are confirmed also with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P>99.9 per cent). No redshift-evolution is observed when regions above the core (r > 0.15 R500) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form $Z(r,z)=Z_0 (1+(r/0.15 R500)^2)^{-\beta} (1+z)^{-\gamma}$, with $(Z_0, \beta, \gamma) = (0.83 \pm 0.13, 0.55 \pm 0.07, 1.7 \pm 0.6)$ in CC clusters and $(0.39 \pm 0.04, 0.37 \pm 0.15, 0.5 \pm 0.5)$ for NCC systems. Our results represent the most extensive study of the spatially-resolved metal distribution in the cluster plasma as function of redshift.Comment: 5 pages. Research Note accepted for publication in A&

Evolution in the iron abundance of the ICM

We present a Chandra analysis of the X-ray spectra of 56 clusters of galaxies at $z>0.3$, which cover a temperature range of $3> kT > 15$ keV. Our analysis is aimed at measuring the iron abundance in the ICM out to the highest redshift probed to date. We find that the emission-weighted iron abundance measured within $(0.15-0.3) R_{vir}$ in clusters below 5 keV is, on average, a factor of $\sim2$ higher than in hotter clusters, following $Z(T)\simeq 0.88 T^{-0.47} Z_\odot$, which confirms the trend seen in local samples. We made use of combined spectral analysis performed over five redshift bins at $0.3> z > 1.3$ to estimate the average emission weighted iron abundance. We find a constant average iron abundance $Z_{Fe}\simeq 0.25 Z_\odot$ as a function of redshift, but only for clusters at $z>0.5$. The emission-weighted iron abundance is significantly higher ($Z_{Fe}\simeq0.4 Z_\odot$) in the redshift range $z\simeq0.3-0.5$, approaching the value measured locally in the inner $0.15 R_{vir}$ radii for a mix of cool-core and non cool-core clusters in the redshift range $0.1<z<0.3$. The decrease in $Z_{Fe}$ with $z$ can be parametrized by a power law of the form $\sim(1+z)^{-1.25}$. The observed evolution implies that the average iron content of the ICM at the present epoch is a factor of $\sim2$ larger than at $z\simeq 1.2$. We confirm that the ICM is already significantly enriched ($Z_{Fe}\simeq0.25 Z_\odot$) at a look-back time of 9 Gyr. Our data provide significant constraints on the time scales and physical processes that drive the chemical enrichment of the ICM.Comment: 4 pages, 4 figures, to appear in the Proceedings of "The Extreme Universe in the Suzaku Era", Dicember 2006, Kyoto (Japan

CLASH-VLT: Dissecting the Frontier Fields Galaxy Cluster MACS J0416.1-2403 with ∼800 Spectra of Member Galaxies

We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields cluster MACS J0416.1-2403 (z = 0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ~600 arcmin^2, including ~800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ~2.2 r _(200) (~4 Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster (M _(200) ~ 0.9 × 10^(15) M_⊙ and σ_(V,r200) ~ 1000 km s^(−1)) presenting two major features: (i) a bimodal velocity distribution, showing two central peaks separated by ΔV _(rf) ~ 1100 km s^(−1) with comparable galaxy content and velocity dispersion, and (ii) a projected elongation of the main substructures along the NE–SW direction, with a prominent sub-clump ~600 kpc SW of the center and an isolated BCG approximately halfway between the center and the SW clump. We also detect a low-mass structure at z ~ 0.390, ~10' south of the cluster center, projected at ~3 Mpc, with a relative line-of-sight velocity of ΔV_(rf) ~ −1700 km s^(−1). The cluster mass profile that we obtain through our dynamical analysis deviates significantly from the "universal" NFW, being best fit by a Softened Isothermal Sphere model instead. The mass profile measured from the galaxy dynamics is found to be in relatively good agreement with those obtained from strong and weak lensing, as well as with that from the X-rays, despite the clearly unrelaxed nature of the cluster. Our results reveal an overall complex dynamical state of this massive cluster and support the hypothesis that the two main subclusters are being observed in a pre-collisional phase, in agreement with recent findings from radio and deep X-ray data. In this article, we also release the entire redshift catalog of 4386 sources in the field of this cluster, which includes 60 identified Chandra X-ray sources and 105 JVLA radio sources

The outer regions of galaxy clusters: Chandra constraints on the X-ray surface brightness

(Abridged version) We study the properties of the X-ray surface brightness profiles in a sample of galaxy clusters that were observed with Chandra and have emission detectable with a signal-to-noise ratio higher than 2 at a radius beyond R500 ~ 0.7 R200. Our study aims to measure the slopes of the X-ray surface brightness and of the gas density profiles in the outskirts of massive clusters. These constraints are compared to similar results obtained from observations and numerical simulations of the temperature and dark matter density profiles with the intention of presenting a consistent picture of the outer regions of galaxy clusters. We extract the surface brightness profiles Sb(r) of 52 X-ray luminous galaxy clusters at z>0.3 from X-ray exposures obtained with Chandra. We estimate R200 using both a beta-model that reproduces Sb(r) and scaling relations from the literature. The two methods converge to comparable values. We determine the radius, R_S2N, at which the signal-to-noise ratio is larger than 2 and select the objects in the sample that satisfy the criterion R_S2N/R200 > 0.7. For the eleven selected objects, we model with a power-law the behaviour of Sb(r). We measure a consistent steepening of the Sb(r) profile moving outward from 0.4 R200, where an average slope of -3.6 (sigma=0.8) is estimated. At R200, we evaluate a slope of -4.3 (sigma=0.9) that implies a slope in the gas density profile of -2.6 and a predicted mean value of the surface brightness in the 0.5-2 band of 2e-12 erg/s/cm2/deg2. Combined with estimates of the outer slope of the gas temperature profile and expectations about the dark matter distribution, these measurements allow us to describe properly how X-ray luminous clusters behave out to the virial radius.Comment: 7 pages. A&A in press. Minor revisions to match published version: added references, corrected typo

An X-ray view of Mrk 705: A borderline narrow-line Seyfert 1 galaxy

Mrk 705 exhibits optical properties of both narrow- and broad-line Seyfert 1 galaxies. We examine the X-ray properties of this borderline object utilising proprietary and public data from Chandra, ASCA, ROSAT and RXTE, spanning more than twelve years. Though long-term flux variability from the pointed observations appears rather modest (about 3 times), we do find examples of rare large amplitude outbursts in the RXTE monitoring data. There is very little evidence of long-term spectral variability as the low- and high-energy spectra appear constant with time. A 6.4 keV emission line is detected in the ASCA spectra of Mrk 705, but not during the later, higher flux state Chandra observation. However, the upper limit on the equivalent width of a line in the Chandra spectrum is consistent with a constant-flux emission line and a brighter continuum, suggesting that the line is emitted from distant material such as the putative torus. Overall, the X-ray properties of Mrk 705 appear typical of BLS1 activity.Comment: 7 pages, 7 figures. Accepted for publication in A&A (Research Note

Bottom-Up Approach to Moduli Dynamics in Heavy Gravitino Scenario : Superpotential, Soft Terms and Sparticle Mass Spectrum

The physics of moduli fields is examined in the scenario where the gravitino is relatively heavy with mass of order 10 TeV, which is favored in view of the severe gravitino problem. The form of the moduli superpotential is shown to be determined, if one imposes a phenomenological requirement that no physical CP phase arise in gaugino masses from conformal anomaly mediation. This bottom-up approach allows only two types of superpotential, each of which can have its origins in a fundamental underlying theory such as superstring. One superpotential is the sum of an exponential and a constant, which is identical to that obtained by Kachru et al (KKLT), and the other is the racetrack superpotential with two exponentials. The general form of soft supersymmetry breaking masses is derived, and the pattern of the superparticle mass spectrum in the minimal supersymmetric standard model is discussed with the KKLT-type superpotential. It is shown that the moduli mediation and the anomaly mediation make comparable contributions to the soft masses. At the weak scale, the gaugino masses are rather degenerate compared to the minimal supergravity, which bring characteristic features on the superparticle masses. In particular, the lightest neutralino, which often constitutes the lightest superparticle and thus a dark matter candidate, is a considerable admixture of gauginos and higgsinos. We also find a small mass hierarchy among the moduli, gravitino, and superpartners of the standard-model fields. Cosmological implications of the scenario are briefly described.Comment: 45 pages, 10 figures, typos correcte

Tracing the evolution in the iron content of the ICM

We present a Chandra analysis of the X-ray spectra of 56 clusters of galaxies at z>0.3, which cover a temperature range of 3>kT>15 keV. Our analysis is aimed at measuring the iron abundance in the ICM out to the highest redshift probed to date. We find that the emission-weighted iron abundance measured within (0.15-0.3)R_vir in clusters below 5 keV is, on average, a factor of ~2 higher than in hotter clusters, following Z(T)~0.88T^-(0.47)Z_o, which confirms the trend seen in local samples. We made use of combined spectral analysis performed over five redshift bins at 0.3>z>1.3 to estimate the average emission weighted iron abundance. We find a constant average iron abundance Z_Fe~0.25Z_o as a function of redshift, but only for clusters at z>0.5. The emission-weighted iron abundance is significantly higher (Z_Fe~0.4Z_o) in the redshift range z~0.3-0.5, approaching the value measured locally in the inner 0.15R_vir radii for a mix of cool-core and non cool-core clusters in the redshift range 0.1<z<0.3. The decrease in Z_Fe with redshift can be parametrized by a power law of the form ~(1+z)^(-1.25). The observed evolution implies that the average iron content of the ICM at the present epoch is a factor of ~2 larger than at z=1.2. We confirm that the ICM is already significantly enriched (Z_Fe~0.25Z_o) at a look-back time of 9 Gyr. Our data provide significant constraints on the time scales and physical processes that drive the chemical enrichment of the ICM.Comment: 6 pages, 6 figures, to appear in the Proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching (Germany