Notes on Meeting of STAR HBT Physics Working Group
9-11 AM Sunday, August 1, 1999.

  1. Mike Lisa gave a summary of recent progress on the StHbt analysis framework for HBT and other physics analysis. The code has already been used in preliminary analyses of 1-D and 3-D HBT simulations as well as on kaon simulations to extract the invariant mass of the phi, and on event-by-event analysis of proposed parity-violation variables. Mike acknowledged considerable help in developing the framework was provided by Frank Laue and Selemon Bekele.

    1. The micro-DST format for HBT developed by Dave Hardtke was presented and discussed. A topology variable will be added to the format. There was a question of whether extra "placeholders" are needed. ML will discuss this with the Strangeness PWG.

    2. There was a discussion of how the HBT analysis code will be optimized for speed of execution after the micro-DST format is in place. It was suggested that some attention to I/O speed may be needed.

    3. There was a discussion of the fitting object needed for HBT analysis. Robert Willson and Sanjeev Pandey volunteered to do the implementation of the fitting methods. It is planned that the non-linear search code MINUIT will be integrated into the framework. Time scale for this work is one week or so.

    4. Robert Willson agreed to write a proposal on how to do 3-particle (and perhaps n-particle) correlations within the StHbt framework. This will be done in consultation with Brian Lasuik.

    5. Fabrice Retiere suggested an upgrade to StHbt that would provide a mechanism that would pass "true momentum" and freeze-out position from Monte-Carlo event generators (e.g., RMD) to the correlation functions. He agreed to work on implementing this.

    6. John Cramer reported that tabulated finite-size Coulomb correction functions for like and opposite sign pions have been calculated for radii of 6 fm to 18 fm in 2 fm steps using the Pratt code which does a 6-dimensional integration of Coulomb wave functions over the source, using 1,000,000 MonteCarlo steps per table entry. These are available at /afs/rhic/star/hbt/coul . Tom Humanic requested that Coulomb tables be extended to smaller radii. Cramer agreed to do extend the range to 0 to 20 fm in 2 fm steps. Randy Wells agreed to work on a C++ object operating within StHbt that will provide Coulomb corrections for any requested source radius and eta (or Q_rel, particle masses, and Z1*Z2) by interpolating these tables.

  2. Jinbo Zhang reported on his recent RQMD/CRAB simulations of HBT correlation functions for Au+Au at RHIC. An interesting question was raised: Must Rout=Rside when the transverse momentum pt=0? This constraint was not apparent in the simulations.

  3. Fuqiang Wang reported on his investigations of the possibility of p-Lambda correlations at STAR. The correlation functions are surprisingly strong and have no Coulomb effects. Fairly sensitive sequence-of-emission tests are possible with these correlations. Furthermore, these correlations have significantly increased sensitivity to large sources (such as we hope to see at RHIC) as compared to traditional two-proton correlations.

  4. We agreed that the HBT PWG will begin bi-weekley phone meetings, to be set up by Mike Lisa. The first of these will probably be on 9/2/99 at noon to 1 PM EDT.

The meeting adjourned at 11:00 AM.
(Notes by J. G. Cramer and M. A. Lisa)