121546704
Experimental Program of the Future COMPASS-II Experiment at CERN
Over the last decade the COMPASS experiment has successfully obtained precise results on nucleon structure and hadron spectroscopy, with statistical errors much lower than previously reported. Recently, the new COMPASS-II program, focused on the study of a more complete nucleon description, was approved by CERN. The goal of the program is to access the nucleon structure beyond the collinear approxi-mation, including the quark intrinsic transverse momentum distributions, which are described by the Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs) and by Generalised Parton Distributions (GPDs). The COMPASS collaboration proposes to measure the TMD PDFs, for the first time, via the polarised Drell-Yan process. The results will be complementary to those already obtained in polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS). The GPDs can be accessed using deeply virtual Compton scattering and hard exclusive meson production using an unpolarised hydrogen target in a kinematic region not yet covered by any existing experiment. Also unpolarised SIDIS will be studied, by improving the knowledge of the strange quark PDF and obtaining the kaon fragmentation functions. Another topic covered in this COMPASS-II program is the measurement of the pion and kaon polarisabilities using the Primakoff reaction, which corresponds to a test of the chiral perturbative theory.
118204757
Gluon polarisation from high transverse momentum hadron pairs production (COMPASS)
A new preliminary result of a gluon polarisation \Delta G/G obtained selecting high transverse momentum hadron pairs in DIS events with Q^2>1 (GeV/c)^2 is presented. Data has been collected by COMPASS at CERN during the 2002-2004 years. In the extraction of $\Delta G/G$ contributions coming from the leading order $\gamma q$ and QCD processes are taken into account. A new weighting method based on a neural network approach is used. Also a preliminary result of \Delta G/G for events with Q^2<1 (GeV/c)^2 is presented.
117242696
Measurement of The Gluon Polarisation Through High $p_T$ Hadron Production in COMPASS
One of the missing keys in the present understanding of the spin structure of the nucleon is the contribution from the gluons: the so called gluon polarisation. This quantity can be determined in DIS through the Photon-Gluon Fusion (PGF) process, in which two analysis methods may be used: (i) identifying open charm events or (ii) selecting events with high pT hadrons. The data used in the present work were collected by the COMPASS Experiment, where a naturally polarised muon beam of 160 GeV, impinging on a polarised nucleon fixed target, is used. The results for the gluon polarisation from high pT are presented. The gluon polarisation result for high pT hadrons is divided, for the first time, into three independent xG bins at leading order (LO). A new weighted method based on a neural network approach is used.
8619236
Reproducing the assembly of massive galaxies within the hierarchical cosmogony
In order to gain insight into the physical mechanisms leading to the formation of stars and their assembly in galaxies, we compare the predictions of the MOdel for the Rise of GAlaxies aNd Active nuclei (MORGANA) to the properties of K- and 850-μm-selected galaxies (such as number counts, redshift distributions and luminosity functions) by combining MORGANA with the spectrophotometric model GRASIL. We find that it is possible to reproduce the K- and 850-μm-band data sets at the same time and with a standard Salpeter initial mass function, and ascribe this success to our improved modelling of cooling in DM haloes. We then predict that massively star-forming discs are common at z ∼ 2 and dominate the star formation rate, but most of them merge with other galaxies within ∼100 Myr. Our preferred model produces an overabundance of bright galaxies at z < 1; this overabundance might be connected to the build-up of the diffuse stellar component in galaxy clusters, as suggested by Monaco et al., but a naive implementation of the mechanism suggested in that paper does not produce a sufficient slowdown of the evolution of these objects. Moreover, our model overpredicts the number of
9385790
A Physical Model for the joint evolution of high-z QSOs and Spheroids
We summarize our physical model for the early co-evolution of spheroidal galaxies and of active nuclei at their centers. Our predictions are in excellent agreement with a number of observables which proved to be extremely challenging for all the current semi-analytic models, including the sub-mm counts and the corresponding redshift distributions, and the epoch-dependent K-band luminosity function of spheroidal galaxies. Also, the black hole mass function and the relationship between the black hole mass and the velocity dispersion in the galaxy are nicely reproduced. The mild AGN activity revealed by X-ray observations of SCUBA sources is in keeping with our scenario, and testify the build up of SMBH triggered by intense star formation.
1119742
Old massive ellipticals and S0 in the Hubble deep field vanish from view at z > 1.3: Possible solutions of the enigma
We have investigated the properties of a bright K-band selected sample of early-type galaxies in the Hubble Deep Field, as representative of the field galaxy population. This dataset, based on public archives from HST and from deep observations at Hawaii and Kitt-Peak, is unique as for the morphological information on faint high-z sources, and for complete photometric and spectroscopic coverage. The majority of bright early-type galaxies in this field are found at redshifts z ≤ 1.3 to share common properties with those of high-z cluster samples, as for the age and mass of the dominant stellar population – which are found to be as old as 3-5 Gyr and as massive as 10 M⊙ already at z ≃ 1. The bright end of the E/S0 population is already in place by that cosmic epoch, with space densities, masses and luminosities consistent with those of the local field population. There is no evidence of a steepening of the mass function from z=0 to z=1, as inferred by some authors from analyses of optically-selected samples and favoured by hierarchical clustering models forming most of the E/S0s at z 1.3, which would be expected as clearly detectable above the flux limits, given the aged properties of the lower redshift counterparts. So, something hide them at high redshifts. Merging could be an explanation, but it would require that already formed and old stellar systems would assemble on short timescales of Dipartimento di Astronomia, Vicolo Osservatorio 5, I-35122, Padova, Italy. E-mail: Franceschini@astrpd.pd.astro.it International School for Advanced Studies, Via Beirut, I34014 Trieste, Italy Osservatorio Astronomico, Vicolo dell’Osservatorio 5, I35122 Padova, Italy.
18579879
Models of Galaxy Evolution from the UV to the Sub-Millimeter
We present the first results of a detailed modeling of chemical and photometric evolution of galaxies including the effects of a dusty interstellar medium. A chemical evolution code follows the SF rate, the gas fraction and the metallicity, basic ingredients for the stellar population synthesis. The latter is performed with a grid of integrated spectra for SSP of different ages and metallicities, in which the effects of dusty envelopes around AGB stellar are included. The residual fraction of gas in the galaxy is divided into two phases: the star forming molecular clouds and the diffuse medium. The molecular gas is sub-divided into clouds of given mass and radius: it is supposed that any SSP is borne within the cloud and progressively escapes it. The emitted spectrum of the star forming molecular clouds is computed with a radiative transfer code. The diffuse dust emission (cirrus) is derived by describing the galaxy as an axially symmetric system, in which the local dust emissivity is consistently calculated as a function of the local field intensity due to the stellar component. Effects of very small grains, subject to temperature fluctuations, as well as PAH are included. The model is compared and calibrated with available data of starburst galaxies in the local universe, in particular new broad-band and spectroscopic ISO observations. It will be a fundamental tool to extract information on global evolution of the stellar component and of ISM of galaxies from observations covering four decades in $\lambda$. The combination of observations from HST, Keck, ISO and ground-based optical, IR and sub-mm telescopes already provided several objects at relevant $z$ with spectral information on this large $\lambda$ range. Their number will increase after the completion of ISO surveys, and will burst when SIRFT, FIRST, Planck