Tilted Pion Sources from Azimuthally Sensitive HBT Interferometry

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 $R_{ol}^2$ and $R_{sl}^2$ 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 degrees) 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 $R_{ol}^2$ and $R_{sl}^2$ thus probes directly the physical origin of directed pion flow.Comment: submitted to Phys. Rev. Lett; revised version has some wording changes/clarification, finer binning in q leads to tiny changes in Fig. 2, one new referenc

Symmetry constraints for the emission angle dependence of Hanbury Brown--Twiss radii

We discuss symmetry constraints on the azimuthal oscillations of two-particle correlation (Hanbury Brown--Twiss interferometry) radii for non-central collisions between equal spherical nuclei. We also propose a new method for correcting in a model-independent way the emission angle dependent correlation function for finite event plane resolution and angular binning effects.Comment: 8 pages revtex4, 2 tables, no figures. Short Section VI added and correction algorithm in Section VII made more explicit. Submitted to Physical Review

Ambiguities in the HBT approach to determine the interaction regions

The necessary and sufficient condition for a quantity to be measurable by the HBT method is given and discussed.Comment: Report at the conference QCD08, July 2008, LateX 8 pages, no figure

Emission angle dependent pion interferometry at RHIC and beyond

We use hydrodynamics to generate freeze-out configurations for non-central heavy-ion collisions at present and future collider energies. Such collisions are known to produce strong elliptic flow. The accompanying space-time structure of the source at freeze-out is analyzed using pion interferometry. Between RHIC and LHC energies the source deformation in the transverse plane changes sign. This leaves characteristic signatures in the emission angle dependence of the HBT radii.Comment: Minor changes (some references and discussion added), accepted by Physics Letters

Femtoscopy in Relativistic Heavy Ion Collisions: Two Decades of Progress

Analyses of two-particle correlations have provided the chief means for determining spatio-temporal characteristics of relativistic heavy ion collisions. We discuss the theoretical formalism behind these studies and the experimental methods used in carrying them out. Recent results from RHIC are put into context in a systematic review of correlation measurements performed over the past two decades. The current understanding of these results is discussed in terms of model comparisons and overall trends.Comment: 49 pages, 16 figures; to appear in Annual Review of Nuclear and Particle Science; final version includes minor updates in text, a few references added, and two figures updated; Figures and numerical data tables available at http://www.physics.ohio-state.edu/~lisa/FemtoscopyReview2005

Detection of source inhomogeneity through event-by-event two-pion Bose-Einstein correlations

We develop a method for detecting the inhomogeneity of the pion-emitting sources produced in ultra-relativistic heavy ion collisions, through event-by-event two-pion Bose-Einstein correlations. The root-mean-square of the error-inverse-weighted fluctuations between the two-pion correlation functions of single and mixed events are useful observables for the detection. By investigating the root-mean-square of the weighted fluctuations for different impact parameter regions people may hopefully determine the inhomogeneity of the particle-emitting in the coming Large Hadron Collider (LHC) heavy ion experiments.Comment: 10 pages, 6 figure

Correlation femtoscopy

The basics of correlation femtoscopy, recent results from femtoscopy in relativistic heavy ion collisions and their consequences are shortly reviewed.Comment: 10 pages, plenary review talk at Quark Matter 2005, 2 references adde

HBT: A (mostly) experimental overview

I will present a review of the field of Hanbury Brown-Twiss interferometry in relativistic heavy-ion collisions. The "HBT puzzle" is explored in detail, emphasizing recent theoretical attempts to understand the persisting puzzle. I also present recent experimental results on azimuthally sensitive HBT, HBT of direct photons, and some surprises in the comparison of HBT results from p+p and Au+Au collisions at RHIC.Comment: 8 pages, 3 figures. Proceedings of the Quark Matter 2004 conference (Oalkland, CA, USA, January 2004

Hydrodynamic emission of strange and non-strange particles at RHIC and LHC

The hydrodynamic model is used to describe the single-particle spectra and elliptic flow of hadrons at RHIC and to predict the emission angle dependence of HBT correlations at RHIC and LHC energies.Comment: 6 pages LaTeX, 3 postscript figures. Proceedings for the conference "Strange Quark Matter 2003", Atlantic Beach, NC, March 12-17, 2003, to appear in J. Phys.