Popularizing science in Italy: a historical perspective. An interview with Paola Govoni

The interview concerns the role of scientific books in the Italian society from the 19th century until today. Having played an important role in the formation of a national scientific community, science popularization has offered a ceaseless high-quality production during the past two centuries. On the other hand, even today scientific publications do reach only a narrow \ue9lite. In the author\u2019s opinion, only the school system has the power to widen the public for science in Italy

The CMS ECAL in situ intercalibration

The electromagnetic calorimeter (ECAL) of the CMS detector contains about 76000 lead-tungstate (PbWO4) crystals. This calorimeter has an excellent intrinsic energy resolution, below 0.5% above 120 GeV. At high energies, the major contribution to the resolution is given by the inter-calibration of the channels that compose the detector. It is therefore important to keep this contribution below 0.5%. To reach such a precision, several techniques have been envisaged, both before and after the start of the experiment. During the data taking, in particular, physics channels will be used to equalize the response of all the PbWO4 crystals of the detector. At the very beginning the symmetry of the minimum bias deposition, together with the Z invariant mass reconstruction, will provide a first estimate of the calibration coefficients, that will be eventually determined by using the E/p ratio of isolated electrons, mainly coming from the W decay. The π 0 and η 0 decays will also help determining the calibration coefficients

Historians of science and the Sobel effect

In 1995, journalist Dava Sobel\u2019s Longitude caused an earthquake in the history of science community. The present article analyses how only recently historians of science have fully realized the novelty the book represented. In the meantime, the international success of popular books by journalists on the history of science has become a well-known phenomenon. The author suggests that the huge publishing success of Sobel\u2019s book - the \u201cSobel Effect\u201d \u2013 has provoked three main kinds of reaction among historians: rejection, detachment, and imitation. Which of the three strategies is the best, for both public and authors

Diffuse radio emission in a REFLEX cluster

Deep Very Large Array radio observations are presented for the REFLEX clusters RXCJ0437.1+0043 and RXCJ1314.4-2515. They are at similar distance and show similar X-ray luminosity, but they are quite different in X-ray structure. Indeed RXCJ0437.1+0043 is regular and relaxed, whereas RXCJ1314.4-2515 is characterized by substructure and possible merging processes. The radio images reveal no diffuse emission in RXCJ0437.1+0043, and a complex diffuse structure in RXCJ1314.4-2515. The diffuse source in the latter cluster consists of a central radio halo which extends to the West toward the cluster periphery and bends to the North to form a possible relic. Another extended source is detected in the eastern cluster peripheral region. Although there could be plausible optical identifications for this source, it might also be a relic candidate owing to its very steep spectrum. The present results confirm the tight link between diffuse cluster radio sources and cluster merger processes.Comment: Accepted for publication in A&A. Figures here have been degraded to reduce their size. A version with full resolution figures is available at http://www.ira.cnr.it/~lferetti/OUTGOING/papREFLEX.ps.g

The intracluster magnetic field power spectrum in Abell 2382

The goal of this work is to put constraints on the strength and structure of the magnetic field in the cluster of galaxies A2382. We investigate the relationship between magnetic field and Faraday rotation effects in the cluster, using numerical simulations as a reference for the observed polarization properties. For this purpose we present Very Large Array observations at 20 cm and 6 cm of two polarized radio sources embedded in A2382, and we obtained detailed rotation measure images for both of them. We simulated random three-dimensional magnetic field models with different power spectra and thus produced synthetic rotation measure images. By comparing our simulations with the observed polarization properties of the radio sources, we can determine the strength and the power spectrum of intra-cluster magnetic field fluctuations that best reproduce the observations. The data are consistent with a power law magnetic field power spectrum with the Kolmogorov index $n=11/3$, while the outer scale of the magnetic field fluctuations is of the order of 35 kpc. The average magnetic field strength at the cluster center is about 3 $\mu$G and decreases in the external region as the square root of the electron gas density. The average magnetic field strength in the central 1 Mpc$^{3}$ is about 1 $\mu$G.Comment: Comments: 18 pages, 13 figures, accepted by A&A. For a version with high quality figures, see http://erg.ca.astro.it/preprints/guidetti2007

The CMS Electromagnetic Calorimeter Pre-calibration with Cosmic Rays and Test Beam Electrons

The electromagnetic calorimeter of the CMS experiment at the new CERN proton-proton Collider (LHC) is at an advanced stage of construction. A necessary condition for its optimal performance is a precise channel-to-channel calibration. The use of cosmic rays allows the pre-calibration of all the channels at the level of 2% before the final installation in CMS and provides an extensive functionality test, essential for the commissioning of the detector. On the other hand, a beam of electrons permits extremely precise (better than 0.5%) pre-calibration coefficients to be obtained on a fraction of the calorimeter, that can also be used as a reference for the in situ calibration procedures that will rely on physics data

Electron affinity of liquid water.

Understanding redox and photochemical reactions in aqueous environments requires a precise knowledge of the ionization potential and electron affinity of liquid water. The former has been measured, but not the latter. We predict the electron affinity of liquid water and of its surface from first principles, coupling path-integral molecular dynamics with ab initio potentials, and many-body perturbation theory. Our results for the surface (0.8 eV) agree well with recent pump-probe spectroscopy measurements on amorphous ice. Those for the bulk (0.1-0.3 eV) differ from several estimates adopted in the literature, which we critically revisit. We show that the ionization potential of the bulk and surface are almost identical; instead their electron affinities differ substantially, with the conduction band edge of the surface much deeper in energy than that of the bulk. We also discuss the significant impact of nuclear quantum effects on the fundamental gap and band edges of the liquid

The intercalibration of the CMS electromagnetic calorimeter at the test beam

During summer 2006, 9 supermodules of the CMS electromagnetic calorimeter (ECAL) have been exposed to an electron beam at the CERN SPS north area facility. Each supermodule contains 1700 crystals. The intercalibration coefficients of the different channels have been measured for each supermodule. The reproducibility of the intercalibration has been tested by measuring a supermodule twice. The intercalibration coefficients obtained in the electron beam have also been compared with those obtained with cosmic ray muons

Structure of the magnetoionic medium around the FR Class I radio galaxy 3C 449

The goal of this work is to constrain the strength and structure of the magnetic field associated with the environment of the radio source 3C 449, using observations of Faraday rotation, which we model with a structure function technique and by comparison with numerical simulations. We assume that the magnetic field is a Gaussian, isotropic random variable and that it is embedded in the hot intra-group plasma surrounding the radio source. For this purpose, we present detailed rotation measure images for the polarized radio source 3C 449, previously observed with the Very Large Array at seven frequencies between 1.365 and 8.385 GHz. We quantify the statistics of the magnetic-field fluctuations by deriving rotation measure structure functions, which we fit using models derived from theoretical power spectra. We quantify the errors due to sampling by making multiple two-dimensional realizations of the best-fitting power spectrum.We also use depolarization measurements to estimate the minimum scale of the field variations. We then make three-dimensional models with a gas density distribution derived from X-ray observations and a random magnetic field with this power spectrum. Under these assumptions we find that both rotation measure and depolarization data are consistent with a broken power-law magnetic-field power spectrum, with a break at about 11 kpc and slopes of 2.98 and 2.07 at smaller and larger scales respectively. The maximum and minimum scales of the fluctuations are around 65 and 0.2 kpc, respectively. The average magnetic field strength at the cluster centre is 3.5 +/-1.2 micro-G, decreasing linearly with the gas density within about 16 kpc of the nucleus.Comment: 19 pages; 14 figures; accepted for publication on A&A. For a high quality version use ftp://ftp.eso.org/pub/general/guidetti

Testing the radio halo-cluster merger scenario. The case of RXCJ2003.5-2323

We present a combined radio, X-ray and optical study of the galaxy cluster RXCJ2003.5-2323. The cluster hosts one of the largest, most powerful and distant giant radio halos known to date, suggesting that it may be undergoing a strong merger process. The aim of our multiwavelength study is to investigate the radio-halo cluster merger scenario. We studied the radio properties of the giant radio halo in RXCJ2003.5-2323 by means of new radio data obtained at 1.4 GHz with the Very Large Array, and at 240 MHz with the Giant Metrewave Radio Telescope, in combination with previously published GMRT data at 610 MHz. The dynamical state of the cluster was investigated by means of X-ray Chandra observations and optical ESO--NTT observations. Our study confirms that RXCJ2003.5-2323 is an unrelaxed cluster. The unusual filamentary and clumpy morphology of the radio halo could be due to a combination of the filamentary structure of the magnetic field and turbulence in the inital stage of a cluster merger.Comment: 10 page, 10 figures, accepted for publication on A&