4,404 research outputs found
Efficient and robust calculation of femtoscopic correlation functions in spherical harmonics directly from the raw pairs measured in heavy-ion collisions
We present the formalism for calculating the femtoscopic correlation function
directly in spherical harmonics. The numerator and denominator are stored as a
set of one-dimensional histograms representing the spherical harmonic
decompositions of each. We present the formalism to calculate the correlation
function from them directly, without going to any three-dimensional histogram.
We discuss the practical implementation of the method and we provide an example
of its use. We also discuss the stability of the method in the presence of
- holes in the underlying data (e.g. from experimental
acceptance).Comment: 7 pages, 4 figures, submitted to Phys. Rev.
Describing transverse dynamics and space-time evolution at RHIC in a hydrodynamic model with statistical hadronization
A hydrodynamic model coupled to the statistical hadronization code
Therminator is used to study a set of observables in the soft sector at RHIC. A
satisfactory description of the pT-spectra and elliptic flow is obtained,
similarly to other hydrodynamic models. With the Gaussian initial conditions
the transverse femtoscopic radii are also reproduced, providing a possible
solution of the RHIC HBT puzzle.Comment: to appear in the conference proceedings for Quark Matter 2009, March
30 - April 4, Knoxville, Tennesse
Exploring Lifetime Effects in Femtoscopy
We investigate the role of lifetime effects from resonances and emission
duration tails in femtoscopy at RHIC in two Blast-Wave models. We find the
non-Gaussian components compare well with published source imaged data, but the
value of R_out obtained from Gaussian fits is not insensitive to the
non-Gaussian contributions when realistic acceptance cuts are applied to
models.Comment: 5 pages, 2 figure
Measurement of CHD on Titan at Submillimeter Wavelengths
We present the first radio/submillimeter detection of monodeuterated methane
(CHD) in Titan's atmosphere, using archival data from of the Atacama Large
Millimeter/submillimeter Array (ALMA). The and
transitions at 465.235 and 465.250 GHz ( mm) were measured at
significance levels of and , respectively. These two
lines were modeled using the Non-linear optimal Estimator for MultivariatE
spectral analySIS (NEMESIS) radiative transfer code to determine the
disk-averaged CHD volume mixing ratio = in Titan's
stratosphere (at altitudes km). By comparison with the CH vertical
abundance profile measured by Cassini-Huygens mass spectrometry, the resulting
value for D/H in CH is . This is consistent
with previous ground-based and in-situ measurements from the Cassini-Huygens
mission, though slightly lower than the average of the previous values.
Additional CHD observations at higher spatial resolution will be required
to determine a value truly comparable with the Cassini-Huygens CH
measurements, by measuring CHD with ALMA close to Titan's equator. In the
post-Cassini era, spatially resolved observations of CHD with ALMA will
enable the latitudinal distribution of methane to be determined, making this an
important molecule for further studies.Comment: 9 pages, 4 figure
Femtoscopy of Pb-Pb and pp collisions at the LHC with the ALICE experiment
We report on the results of femtoscopic analysis of Pb-Pb collisions at
sqrt(s_NN)=2.76 TeV and pp collisions at sqrt(s)=0.9, 2.76 and 7 TeV with
identical pions and kaons. Detailed femtoscopy studies in heavy-ion collisions
at SPS and RHIC have shown that emission region sizes ("HBT radii") decrease
with increasing pair transverse momentum k_T, which is understood as a
manifestation of the collective behavior of matter. The trend was predicted to
persist at the LHC. The data from Pb-Pb collisions confirm the existence of a
flowing medium and provide strict constraints on the dynamical models. Similar
analysis is carried out for pp collisions for pions and kaons and qualitative
similarities to heavy-ion data are seen, especially in collisions producing
large number of particles. The observed trends give insight into the soft
particle production mechanism in pp collisions. 3D radii were also found to
universally scale with event multiplicity in heavy-ion collisions. We extend
the range of multiplicities both upwards with the Pb-Pb data and downwards with
the pp data to test the scaling in new areas. In particular the high
multiplicity pp collisions reach particle densities comparable to the ones
measured in peripheral Cu-Cu and Au-Au collisions at RHIC. This allows for the
first time to directly compare freeze-out sizes for systems with very different
initial states.Comment: 8 pages, 5 figures, Proceedings of the Quark Matter 2011 plenary tal
Evaluation of the Beam Background Contribution to the pp Minimum Bias Sample Used for First Physics
The note describes the beam background conditions during first physics data taking with ALICE and the strategy for the evaluation of the LHC beam background contribution to the minimum bias event sample used for first physics
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