26,208 research outputs found
Star formation in galaxies hosting Active Galactic Nuclei up to z~1
We review recent evidence for a clear association between accretion onto
supermassive black holes and star formation up to z~1 in the zCOSMOS survey.
Star formation rates (SFRs) are determined from the [OII] emission-line
strength and a correction for the AGN contribution. We find that SFRs of X-ray
selected AGN span a distribution of 1-100 solar masses per year and evolve in a
manner that is indistinguishable from that of massive, star-forming galaxies.
The close relationship between AGN activity and star formation is further
supported by an increase in the AGN fraction with bluer rest-frame colors
(U-V); we further illustrate how the location of AGNs in a color-magnitude
diagram can be misleading in luminosity-limited samples due to the dependence
of AGN activity on the stellar mass and the low mass-to-light ratios of blue
cloud galaxies. To conclude, our results support a co-evolutionary scenario up
to z~1 based on the constancy with redshift of the ratio between mass accretion
rate and SFR.Comment: Invited talk, to appear in the Proceedings of "AGN Feedback in Galaxy
Formation", V.Antonuccio-Delogu and J. Silk, eds., in pres
Measurement of Orbitally Excited D-Mesons at CDF II
Measurement of Orbitally Excited D-Mesons at CDF II Igor V. Gorelov (For the
CDF Collaboration)
Talk given on behalf of the CDF Collaboration at the First Meeting of the APS
Topical Group on Hadronic Physics, GHP 2004, 24-26 October 2004, FERMILAB.
Results on the first measurement of orbitally excited neutral D-meson states,
D*_2 and D_1, produced in hadron collisions at Tevatron are presented. Using
data from the displaced track trigger, CDF II collects the largest world sample
of these states in decay modes D*+ pi-, D+ pi-. Masses and widths of both
states have been measured with precision better than or comparable to the world
average.Comment: 6 pages, 5 figures, talk given on behalf of the CDF Collaboration at
the First Meeting of the APS Topical Group on Hadronic Physics, GHP 2004, Oct
24-26,2004, Fermilab, Batavia, Illinoi
Probing the QCD equation of state with thermal photons in nucleus-nucleus collisions at RHIC
Thermal photon production at mid-rapidity in Au+Au reactions at
= 200 GeV is studied in the framework of a 2D+1 hydrodynamical
model that describes efficiently the bulk identified hadron spectra at RHIC.
The combined thermal plus NLO pQCD photon spectrum is in good agreement with
the yields measured by the PHENIX experiment for all Au+Au centralities. Within
our model, we demonstrate that the correlation of the thermal photon slopes
with the charged hadron multiplicity in each centrality bin provides direct
empirical information on the underlying degrees of freedom and on the equation
of state, , of the strongly interacting matter.Comment: Version to appear in EPJ-C (extended discussion and refs. and a few
corrections
Remarks Concerning the Study of Four-Jet Events from Hadronic Decays of the Z0
The angular correlations of four-jet events from hadronic decays of the Z0
have been studied in the past mainly to extract from them the fundamental
constants of quantum chromodynamics called colour factors. Previous studies
have used all the available phase-space in order to maximize statistics. In
this note we want to point out the possibility that significant differences
between experiment and theory in restricted regions of phase-space might have
escaped detection. Such differences could be a harbinger of the existence of
new particles. Some preliminary results are presented.Comment: 9 pages, 3 figure
The neutrino velocity anomaly as an explanation of the missing observation of neutrinos in coincidence with GRB
The search for neutrinos emitted in coincidence with Gamma-Bay Burst has been
so far unsuccessfully. In this paper we show that the recent result reported by
the OPERA Collaboration on an early arrival time of muon neutrinos with respect
to the one computed assuming the speed of light in vacuum could explain the
null search for neutrinos in coincidence with Gamma-Ray Burst
Baryon Number Transfer in Hadron+Nucleus and Nucleus+Nucleus Collisions: A Link between Elementary and Complex Interactions
The baryon number transfer is studied in elementary and complex hadronic
interactions at the CERN experiment NA49 at the SPS, at 158 AGeV beam energy
(\sqrt{s}=17.2 GeV). A two component picture is proposed, which builds up the
net proton distribution from a target and a projectile component. Using pion
beam, the projectile component is experimentally determined for p+p and p+A
interactions. A similar stopping behaviour of the projectile component is found
for p+A and A+A interactions. Based on these observations, the baryon transfer
is assumed to provide a common scale of inelasticity in p+p, p+A and A+A
interactions. A model-independent way is proposed to predict the pion
multiplicity in A+A.Comment: 10 pages, 12 figures. To appear in the proceedings of International
Workshop on Quark and Hadron Dynamics in Relativistic Heavy Ion Collisions
(BP 2002), Budapest, Hungary, 3-7 Mar 200
Measurement of the B0 and B- meson lifetimes in ALEPH
The lifetimed of the Bbar0 and B- meson lifetimes are measured using data
recorded on the Z peak with the ALEPH detector at LEP. An improved analysis
based on partially reconstructed Bbar0 -> D*+l-nubar and B- -> D0l-nubar decays
is presented.Comment: 3 pages, 1 figur
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