# Presentation: 868931

## Slide 1

## Presentation Overview

-  Motivation
-  Analysis Technique (very brief)
-  Ξ Spectra
-  Ξ0(1530) Signal Extraction
-  Ratios
-  Summary & Outlook

## Motivation

- Ξ0(1530)

- What is the Xi*?
-  Spin 3/2 multi-strange
-  baryon resonance
-  Well established (4-star)
-  Two charge states
-  Only Ξ0 in this analysis
-  Long-lived (cτ~21 fm)

- Why Xi*?
-  Ξ feed-down correction
-  Model constraint
-  Rescattering in Au+Au

- Why not?
-  Rare, σ ~ few b
-  4-particle final state

## Motivation

- STAR Preliminary

- Why Xi*?
-  Clarify <pT> trend in *p+p*

- PDG (note on Ξ resonances):
- “...there has not been a single
- new piece of data on Ξ
- resonances since our 1988
- edition.”

-  Because we can
-  It's cool
-  It's not trivial

## Analysis Technique

-  Topological Decay Identification
-  Several Geometrical Cuts
-  DCA, Decay Length, etc.

-  Corrections from Embedding
- Embedding in Red
- Data in Black

- Ξ-

- Λ

- π-

- π-

##  p+p Results

-  Total Data Set:
-     ~10 million events after quality cuts

-  Sufficient Statistics for 12 Bins in pT

-  0.5  pT .0 GeV/*c*

##  Background Subtraction

-  Ξ's and primary π's
-  Mixed events (red)
-  Cuts on:
-  Event must contain Ξ
-  Number of Ξ's +/- 2
-  Event vertex Z +/- 5cm
-  Multiplicity +/- 2

##  Signal Extraction

-  Fit Breit-Wigner + linear BG
-  Mass, good agreement
-  Slightly wider (~1 σ)

## Anti pT Bins, p+p

- Anti pT Bins, *p+p*

-  500 MeV/c bins
-  Low pT BG?
-  More stats.

## Ratios in p+p

- Ratios in *p*+*p*

##  in d+Au

-  Much stronger signal
-  Only half the d+Au statistics

## Ratios in d+Au

- Ratios in d+Au

## Summary & Outlook

-  Ξ0(1530) measured in *p+p* & d+Au
-  Anti-Ξ*/Ξ* measured vs. pT (statistics limited)
-  2 M *p+p* events not yet analyzed
-  Some run scenarios will double *p+p* minbias
-  Only half d+Au analyzed so far
-  No signal (yet) in Au+Au events at any energy
-  Physics?
-  BG too high?
-  Just me?
-  Embedding on the way
-  Tune cuts more carefully
-  Corrected spectra & yields for *p+p* & d+Au

## The STAR Collaboration

**Argonne National Laboratory•  Institute of High Energy Physics, Beijing•  Institute of Physics, Bhubaneswar•  University of Bern, Switzerland•  University of Birmingham•  Brookhaven National Laboratory•  University of California, Berkeley•  University of California, Davis•  University of California, Los Angeles•  Carnegie Mellon University•  Creighton University•  Laboratory for High Energy (JINR), Dubna•  Particle Physics Laboratory (JINR), Dubna•  University of Frankfurt•  Indiana University, Bloomington•  Institut de Recherches Subatomiques, Strasbourg•  Jammu University•  Kent State University•  Institute of Modern Physics, Lanzhou•  Lawrence Berkeley Laboratory•  Max-Planck-Instit fuer Physik, Munich•  Michigan State University•  Moscow Engineering Physics Institute•  Indian Institute of Technology, Mumbai•  City College of New York•  Ohio State University•  Panjab University•  Pennsylvania State University•  Institute of High Energy Physics, Protvino•  Purdue University•  University of Rajasthan•  Rice University•  Universidade de Sao Paulo•  University of Science and Technology of China (USTC)•  Shanghai Institue of Nuclear Research (SINR)•  SUBATECH, Nantes•  Texas A & M•  University of Texas, Austin•  Tsinghua University•  Variable Energy Cyclotron Centre, Kolkata•  Warsaw University•  Warsaw University of Technology•  University of Washington•  Wayne State University•  Institute of Particle Physics, Wuhan•  Yale University**