2,267 research outputs found
Doorkeepers, the chamberlain and petitioning at the papal court, c.1150â1200
This article looks at the âsecond rankâ of courtiers at the papal curia. The doorkeepers (hostiarii) were part of the pope's personal household, subordinate to the papal chamberlain, but they played a significant role in curial administration: a clear division between âprivateâ household and âpublicâ administration is difficult to see. The hostiarii witnessed many of the financial and patrimonial deals struck by papal representatives; they could allow or deny entry into the pope's presence to petitioners and litigants; and they had a role in the production of papal letters and privileges. They were important figures at the curia
Yano-Koonin-Podgoretskii Parametrisation of the Hanbury Brown-Twiss Correlator
The Yano-Koonin-Podgoretskii (YKP) parametrisation of Hanbury Brown-Twiss
(HBT) two-particle correlation functions opens new strategies for extracting
the emission duration and testing the longitudinal expansion in heavy-ion
collisions. Based on the recently derived model-independent expressions, we
present a detailed parameter study of the YKP parameters for a finite,
hydrodynamically expanding source model of heavy-ion collisions. For the class
of models studied here, we show that the three YKP radius parameters have an
interpretation as longitudinal extension, transverse extension and emission
duration of the source in the YKP frame. This frame is specified by the fourth
fit parameter, the Yano-Koonin velocity which describes to a good approximation
the velocity of the fluid element with highest emissivity and allows to test
for the longitudinal expansion of the source. Deviations from this
interpretation of the YKP parameters are discussed quantitatively.Comment: 38 pages, REVTeX, 11 PS-figures, to be published in Z.Phys.
Space-time Characteristics of the Fireball from HBT Interferometry
We present the Yano-Koonin-Podgoretskii parametrisation of the correlation
function. Compared to the conventionally used Cartesian parametrisation, this
one provides more straightforward measurement of the duration of the emission
process in the fireball and a clearer signal of the longitudinal expansion,
which is expected in ulrarelativistic heavy ion collisions.Comment: 13 pages LaTeX,3 figures incl. with epsf-style. Proceedings of "Heavy
Ion Workshop on Particle Physics", Sept. 2.-6., 1996, Bratislava, Slovakia,
misprint in Eq.(27) correcte
Energy loss of quarks in deconfined matter at RHIC: photon-tagged jets, single electron and dilepton spectra from open charm
We report a first attempt (i) to derive constraints on the energy loss of
charm quarks in a deconfined medium from the recent PHENIX data of
single-electron transverse momentum spectra and (ii) to estimate the resulting
suppression of dileptons from correlated semi-leptonic decays of open charmed
mesons. The momentum imbalance of photon-tagged light-quark jets is also
considered.Comment: contribution to Quark Matter 2002, Nantes, France, July 18 - 24, 200
Universal Pion Freeze-out Phase-Space Density
Results on the pion freeze-out phase-space density in sulphur-nucleus, Pb-Pb
and pion-proton collisions at CERN-SPS are presented. All heavy-ion reactions
are consistent with the thermal Bose-Einstein distrtibution f=1/(exp(E/T)-1) at
T~120 MeV, modified for expansion. Pion-proton data are also consistent with f,
but at T~180 MeV.Comment: 1 page, 1 figure; 98' report for GSI-Darmstad
Jet quenching via jet collimation
The strong modifications of dijet properties in heavy ion collisions measured
by ATLAS and CMS provide important constraints on the dynamical mechanisms
underlying jet quenching. In this work, we show that the transport of soft
gluons away from the jet cone - jet collimation - can account for the observed
dijet asymmetry with values of that lie in the expected order of
magnitude. Further, we show that the energy loss attained through this
mechanism results in a very mild distortion of the azimuthal angle dijet
distribution.Comment: 4 pages, 2 figures; Proceedings of the "Quark Matter 2011" conferenc
The complex environment of the bright carbon star TX Psc as probed by spectro-astrometry
Context: Stars on the asymptotic giant branch (AGB) show broad evidence of
inhomogeneous atmospheres and circumstellar envelopes. These have been studied
by a variety of methods on various angular scales. In this paper we explore the
envelope of the well-studied carbon star TX Psc by the technique of
spectro-astrometry. Aims: We explore the potential of this method for detecting
asymmetries around AGB stars. Methods:We obtained CRIRES observations of
several CO v=1 lines near 4.6 m and HCN lines near 3 m in
2010 and 2013. These were then searched for spectro-astrometric signatures. For
the interpretation of the results, we used simple simulated observations.
Results: Several lines show significant photocentre shifts with a clear
dependence on position angle. In all cases, tilde-shaped signatures are found
where the positive and negative shifts (at PA 0deg) are associated with blue
and weaker red components of the lines. The shifts can be modelled with a
bright blob 70 mas to 210 mas south of the star with a flux of several percent
of the photospheric flux. We estimate a lower limit of the blob temperature of
1000 K. The blob may be related to a mass ejection as found for AGB stars or
red supergiants. We also consider the scenario of a companion object.
Conclusions: Although there is clear spectro-astrometric evidence of a rather
prominent structure near TX Psc, it does not seem to relate to the other
evidence of asymmetries, so no definite explanation can be given. Our data thus
underline the very complex structure of the environment of this star, but
further observations that sample the angular scales out to a few hundred
milli-arcseconds are needed to get a clearer picture
Non-Abelian Energy Loss at Finite Opacity
A systematic expansion in opacity, , is used to clarify the
non-linear behavior of induced gluon radiation in quark-gluon plasmas. The
inclusive differential gluon distribution is calculated up to second order in
opacity and compared to the zeroth order (factorization) limit. The opacity
expansion makes it possible to take finite kinematic constraints into account
that suppress jet quenching in nuclear collisions below RHIC (
AGeV) energies.Comment: 4 pages (revtex) with 3 eps figures, submitted to PR
Lifetimes and Sizes from Two-Particle Correlation Functions
We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the
two-particle correlation function for azimuthally symmetric expanding sources.
We derive model-independent expressions for the YKP fit parameters and discuss
their physical interpretation. We use them to evaluate the YKP fit parameters
and their momentum dependence for a simple model for the emission function and
propose new strategies for extracting the source lifetime. Longitudinal
expansion of the source can be seen directly in the rapidity dependence of the
Yano-Koonin velocity.Comment: 15 pages REVTEX, 2 figures included, submitted to Phys. Lett. B,
Expanded discussion of disadvantages of standard HBT fit and of Fig.
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