587 research outputs found
A high-precision polarimeter
We have built a polarimeter in order to measure the electron beam
polarization in hall C at JLAB. Using a superconducting solenoid to drive the
pure-iron target foil into saturation, and a symmetrical setup to detect the
Moller electrons in coincidence, we achieve an accuracy of <1%. This sets a new
standard for Moller polarimeters.Comment: 17 pages, 9 figures, submitted to N.I.
Moment Analysis and Zipf Law
The moment analysis method and nuclear Zipf's law of fragment size
distributions are reviewed to study nuclear disassembly. In this report, we
present a compilation of both theoretical and experimental studies on moment
analysis and Zipf law performed so far. The relationship of both methods to a
possible critical behavior or phase transition of nuclear disassembly is
discussed. In addition, scaled factorial moments and intermittency are
reviewed.Comment: Caption of Fig.6 was corrected. Review paper for WCI (World Consensus
Initiative) Book "Dynamics and Thermodynamics with Nuclear Degrees of
Freedom", published in Euorpean Physics Journal A as part of the Topical
Volume. 16 pages, 21 figure
Licht-Transillumination trĂŒber MEdien: Verbesserung der Ortsauflösung durch ein zeitauflösendes Verfahren
Liquid-gas phase transition in nuclei in the relativistic Thomas-Fermi theory
The equation of state (EOS) of finite nuclei is constructed in the
relativistic Thomas-Fermi theory using the non-linear
model. The caloric curves are calculated by confining the nuclei in the
freeze-out volume taken to be a sphere of size about 4 to 8 times the normal
nuclear volume. The results obtained from the relativistic theory are not
significantly different from those obtained earlier in a non-relativistic
framework. The nature of the EOS and the peaked structure of the specific heat
obtained from the caloric curves show clear signals of a liquid-gas phase
transition in finite nuclei. The temperature evolution of the Gibbs potential
and the entropy at constant pressure indicate that the characteristics of the
transition are not too different from the first-order one.Comment: RevTex file(19 pages) and 12 psfiles for fugures. Physical Review C
(in Press
One-loop chiral amplitudes of Moller scattering process
The high energy amplitudes of the large angles Moller scattering are
calculated in frame of chiral basis in Born and 1-loop QED level. Taking into
account as well the contribution from emission of soft real photons the compact
relations free from infrared divergences are obtained. The expressions for
separate chiral amplitudes contribution to the cross section are in agreement
with renormalization group predictions.Comment: 15 pages, 3 figure
Microcanonical studies concerning the recent experimental evaluations of the nuclear caloric curve
The microcanonical multifragmentation model from [Al. H. Raduta and Ad. R.
Raduta, Phys. Rev. C 55, 1344 (1997); 56, 2059 (1997); 59, 323 (1999)] is
refined and improved by taking into account the experimental discrete levels
for fragments with and by including the stage of sequential decay of
the primary excited fragments. The caloric curve is reevaluated and the heat
capacity at constant volume curve is represented as a function of excitation
energy and temperature. The sequence of equilibrated sources formed in the
reactions studied by the ALADIN group (Au+Au at 600, 800 and
1000 MeV/nucleon bombarding energy) is deduced by fitting simultaneously the
model predicted mean multiplicity of intermediate mass fragments ()
and charge asymmetry of the two largest fragments () versus bound
charge () on the corresponding experimental data. Calculated HeLi
isotopic temperature curves as a function of the bound charge are compared with
the experimentally deduced ones.Comment: 13 pages, 4 figure
Search for spontaneous muon emission from lead nuclei
We describe a possible search for muonic radioactivity from lead nuclei using
the base elements ("bricks" composed by lead and nuclear emulsion sheets) of
the long-baseline OPERA neutrino experiment. We present the results of a Monte
Carlo simulation concerning the expected event topologies and estimates of the
background events. Using few bricks, we could reach a good sensitivity level.Comment: 12 pages, 4 figure
Thermal Bremsstrahlung photons probing the nuclear caloric curve
Hard-photon (E 30 MeV) emission from second-chance
nucleon-nucleon Bremsstrahlung collisions in intermediate energy heavy-ion
reactions is studied employing a realistic thermal model. Photon spectra and
yields measured in several nucleus-nucleus reactions are consistent with an
emission from hot nuclear systems with temperatures 4 - 7 MeV. The
corresponding caloric curve in the region of excitation energies
3{\it A} - 8{\it A} MeV shows lower values of than
those expected for a Fermi fluid.Comment: 13 pages, 3 figures. To appear in Physics Letters
User geospatial context for music recommendation in microblogs
Music information retrieval and music recommendation are seeing a paradigm shift towards methods that incorporate user context aspects. However, structured experiments on a standardized music dataset to investigate the effects of do-ing so are scarce. In this paper, we compare performance of various combinations of collaborative filtering and geospatial as well as cultural user models for the task of music recom-mendation. To this end, we propose a geospatial model that uses GPS coordinates and a cultural model that uses seman-tic locations (continent, country, and state of the user). We conduct experiments on a novel standardized music collec-tion, the âMillion Musical Tweets Dataset â of listing events extracted from microblogs. Overall, we find that modeling listeners â location via Gaussian mixture models and comput-ing similarities from these outperforms both cultural user models and collaborative filtering. Categories and Subject Descriptors Information systems [Information retrieval]: Music rec-ommendation; Human-centered computing [Collaborative and social computing]: Social medi
On the reliability of negative heat capacity measurements
A global protocol for the thermostatistical analysis of hot nuclear sources
is discussed. Within our method of minimization of variances we show that the
abnormal kinetic energy fluctuation signal recently reported in different
experimental data (M.D'Agostino et al.-Phys. Lett. B 473 (2000) 219, N. Le
Neindre et al.- contr. to the XXXVIII Bormio Winter Meeting on Nucl. Phys.
(2001) 404) is a genuine signal of a first order phase transition in a finite
system.Comment: 15 Postscript figures, submitted to NUCL. Phys. A on 24-apr-200
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