5,149 research outputs found
Re-Hardening of Hadron Transverse Mass Spectra in Relativistic Heavy-Ion Collisions
We analyze the spectra of pions and protons in heavy-ion collisions at
relativistic energies from 2 A GeV to 65+65 A GeV by using a jet-implemented
hadron-string cascade model. In this energy region, hadron transverse mass
spectra first show softening until SPS energies, and re-hardening may emerge at
RHIC energies. Since hadronic matter is expected to show only softening at
higher energy densities, this re-hardening of spectra can be interpreted as a
good signature of the quark-gluon plasma formation.Comment: 10 pages, 3 figures, 1 table, Poster presentation at QM2001, Revised
to correct latex error in citation on April 6, 200
Jet Reconstruction in Heavy Ion Collisions
We examine the problem of jet reconstruction at heavy-ion colliders using
jet-area-based background subtraction tools as provided by FastJet. We use
Monte Carlo simulations with and without quenching to study the performance of
several jet algorithms, including the option of filtering, under conditions
corresponding to RHIC and LHC collisions. We find that most standard algorithms
perform well, though the anti-kt and filtered Cambridge/Aachen algorithms have
clear advantages in terms of the reconstructed transverse-momentum offset and
dispersion.Comment: 31 pages, 17 figure
Implementation of a medium-modified parton shower algorithm
We present a Monte Carlo implementation of medium-induced gluon radiation in
the final-state branching process. Medium effects are introduced through an
additive term in the splitting functions. We have implemented such modification
within PYTHIA. We show the medium effects on the hump-backed plateau, and the
transverse momentum and angular distributions with respect to the parent
parton. As expected, with increasing medium densities there is an increase
(decrease) of partons with small (large) momentum fraction, and angular
broadening is observed. The effects on the transverse-momentum distributions
are more involved, with an enhancement of low- and intermediate- partons
and a decrease at large , which is related to energy conservation, and to
the lack of momentum exchange with the medium in our approach.Comment: LaTeX, 6 pages, 2 eps figures; proceedings of the 3rd International
Conference on Hard and Electromagnetic Probes in High-Energy Nuclear
Collisions - Hard Probes 2008 (Illa de A Toxa, Spain, June 8th-14th 2008
Decay modes of 250No
The Fragment Mass Analyzer at the ATLAS facility has been used to
unambiguously identify the mass number associated with different decay modes of
the nobelium isotopes produced via 204Pb(48Ca,xn)(252-x)No reactions.
Isotopically pure (>99.7%) 204Pb targets were used to reduce background from
more favored reactions on heavier lead isotopes. Two spontaneous fission
half-lives (t_1/2 = 3.7+1.1-0.8 us and 43+22-15 us) were deduced from a total
of 158 fission events. Both decays originate from 250No rather than from
neighboring isotopes as previously suggested. The longer activity most likely
corresponds to a K-isomer in this nucleus. No conclusive evidence for an alpha
branch was observed, resulting in upper limits of 2.1% for the shorter lifetime
and 3.4% for the longer activity.Comment: RevTex4, 10 pages, 5 figures, submitted to PR
Influence of nuclear structure on sub-barrier hindrance in Ni+Ni fusion
Fusion-evaporation cross sections for Ni+Ni have been measured
down to the 10 nb level. For fusion between two open-shell nuclei, this is the
first observation of a maximum in the -factor, which signals a strong
sub-barrier hindrance. A comparison with the Ni+Ni,
Ni+Ni, and Ni+Ni systems indicates a strong
dependence of the energy where the hindrance occurs on the stiffness of the
interacting nuclei.Comment: Submitted to Phys. Rev. Lett. 4 pages, 3 figure
CGC, QCD Saturation and RHIC data (Kharzeev-Levin-McLerran-Nardi point of view)
This is the talk given at the Workshop:"Focus on Multiplicitioes", Bari,
Italy, 17-19 June,2004.. In this talk, we are going to discuss ion-ion and
deuteron - nucleus RHIC data and show that they support, if not more, the idea
of the new QCD phase: colour glass condensate with saturated parton density. .Comment: 26 pages with 33 figure
Medium dependence of multiplicity distributions in MLLA
We study the modification of the multiplicity distributions in MLLA due to
the presence of a QCD medium. The medium is introduced though a multiplicative
constant () in the soft infrared parts of the kernels of QCD evolution
equations. Using the asymptotic ansatz for quark and gluons mean multiplicities
and respectively, we study two
cases: fixed as previously considered in the literature, and fixed
. We find opposite behaviors of the dispersion of the multiplicity
distributions with increasing in both cases. For fixed the
dispersion decreases, while for fixed it increases.Comment: LaTeX, 9 pages, 4 eps figures; proceedings of the 3rd International
Conference on Hard and Electromagnetic Probes in High-Energy Nuclear
Collisions - Hard Probes 2008 (Illa de A Toxa, Spain, June 8th-14th 2008
Calculating the jet-quenching parameter in STU background
In this paper we use the AdS/CFT correspondence to compute the jet-quenching
parameter in a N=2 thermal plasma. We consider the general three-charge black
hole and discuss some special cases. We add a constant electric field to the
background and find the effect of the electric field on the jet-quenching
parameter. Also we include higher derivative terms and obtain the first-order
correction for the jet-quenching parameter.Comment: 17 pages, 3 figures, revised versio
Research encounters, reflexivity and supervision
Reflexivity in qualitative and ethnographic social science research can provide a rich source of data, especially regarding the affective, performative and relational aspects of interviews with research subjects. This paper explores by means of three case examples different ways of accessing and using such reflexivity. The examples are drawn from an empirical psycho-social study into the identity transitions of first-time mothers in an inner-city multicultural environment. Fieldnotes and supervision were used to engage with researcher subjectivity, to enhance the productive use of reflexivity and to address the emotional work of research. The methodology of the supervision was psychoanalytic, in its use of a boundaried frame and of psychoanalytic forms of noticing oneself, of staying engaged emotionally as well as creating a reflective distance. The examples illustrate how this can enhance the knowledge gained about the research subjects
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