Pion HBT results from E895
The E895 Collaboration has studied HBT of negative pions for Au+Au collisions at bombarding
energies 2-8 AGeV. Two experimental papers report our results. One of these represents
a new direction in intensity interferometry, and required a seperate theory paper to discuss
the information available. In another paper, we apply the source-imaging technique of Brown
and Danielewicz to our correlation functions. Finally, the HBT results have been featured
(along with other E895 data) in two Quark Matter presentations and proceedings.
Below, we provide access to these papers, including postscript and gif versions of the
figures, and, in some cases, tabulations of the data.
Bombarding Energy Dependence of 
- Interferometry at the Brookhaven AGS
E895 Collaboration, Phys. Rev. Lett. 84, 2798 (2000)
Abstract
We present the first excitation function of - intensity interferometry
at Alternating Gradient Synchrotron (AGS) energies (2-8 A GeV). The sensitivity of the multidimensional
correlation functions to the geometry and dynamics of the pion-emitting system provides a stringent test
of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both
with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction
dynamics is different in the model than in the data. A significantly increased - emission time scale,
which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.
- Get the paper PDF file
- Figure 1 - eps file or gif file
or tabulated data
- Figure 2 - eps file or gif file
or tabulated data
Azimuthal dependence of pion interferometry at the AGS
E895 Collaboration, Phys. Lett. B496 1 (2000)
Update 2006
Unfortunately, the figures 3-5 which we published look not real nice, so here are some
better versions. (Only appearance has changed.)
Figure 3 - 4 GeV: eps file or png file
Figure 4 - 2 GeV: eps file or png file
Figure 5 - 6 GeV: eps file or png file
Tilted pion sources from azimuthally sensitive HBT interferometry
M.A. Lisa, U. Heinz, and U.A. Wiedemann, Phys. Lett. B489 287 (2000)
(Although this is not an E895 experimental paper, it was motivated by the need
to explain the effects seen in the data of the previous paper listed.)
Abstract
Intensity interferometry in noncentral heavy ion collisions provides access to novel information
on the geometry of the effective pion-emitting source. We demonstrate analytically that, even for
vanishing pair momentum, the cross terms Rol2 and Rsl2 of the HBT correlation function in general
show a strong first harmonic in their azimuthal dependence. The strength of this oscillation
characterizes the tilt of the major axis of the spatial emission ellipsoid away from the direction
of the beam. Event generator studies indicate that this tilt can be large (>20°) at AGS energies
which makes it by far the most significant azimuthally sensitive HBT signal at these energies.
Moreover, transport models suggest that for pions this spatial tilt is directed opposite to the
tilt of the directed flow ellipsoid in momentum space. A measurement of the azimuthal dependence
of the HBT cross terms Rol2 and Rsl2 thus probes directly the physical origin of directed pion flow.
- Get the paper - PDF file
- Figure 1 - eps file or
gif file
- Figure 2 - eps file or
gif file
- Figure 3 (top) - eps file or
gif file
- Figure 3 (bottom) - eps file or
gif file
Azimuthally-sensitive HBT - poster presented at Quark Matter 2001
This poster (Heinz, Lisa, Weidemann) presents the basic idea and formalism
of azimuthally-sensitive HBT, shows model calculations, and application to
E895 data. Importantly, it also contains some symmetry considerations which
apply to the HBT parameters.
Get the poster as a powerpoint file here
Beam Energy Evolution of HBT Systematics at the AGS
E895 Collaboration, Nucl.Phys. A661 444c (2000)
Proceedings of Quark Matter '99 - Torino, Italy
Abstract
We present preliminary results of the first piminus
interferometry (HBT) excitation function at intermediate AGS energies.
The beam energy evolution of the correlations' dependence on m_T, centrality, and
emission angle with respect to the reaction plane are discussed. Comparisons
with predictions of the RQMD cascade model are made.
- Get the talk - powerpoint file
- Get the paper - ps file
- Figure 1 - eps file or
gif file
- Figure 2 - eps file or
gif file
- Figure 3 - eps file or
gif file
- Figure 4 - eps file or
gif file
- Figure 5 - eps file or
gif file
Laying the groundwork at the AGS: Recent results from experiment E895
E895 Collaboration, Nucl. Phys. A698 185c (2002).
Proceedings of Quark Matter '01 - Stony Brook, NY
Abstract
The E895 Collaboration at the Brookhaven AGS has performed
a systematic investigation of Au+Au collisions at 2-8 AGeV,
using a large-acceptance Time Projection Chamber. In addition
to extensive measurements of particle flow, spectra, two-particle
interferometry, and strangeness production, we have performed novel
hybrid analyses, including azimuthally-sensitive pion HBT,
extraction of the six-dimensional pion phasespace density, and
a first measurement of the $\Lambda$-p correlation function.
- Get the talk - powerpoint file
- Get the paper - ps file
- Figure 1 - eps file or gif file
- Figure 2 - eps file or gif file
- Figure 3 - eps file or
gif file
- Color Figure 3 - eps file or
gif file
- Figure 4 - eps file or gif file
- Figure 5 - eps file or gif file
Still to come
- Imaging paper
- Proton-lambda ?
- Phasespace density ?
Mike Lisa
Last modified: Fri Apr 12 10:16:10 EDT 2002
