spokespersons' welcome

Welcome to the STAR website. Helen Caines and Zhangbu Xu are proud to serve as the coSpokespeople. Both of us have worked on STAR for most of our professional careers, we are proud of what STAR has achieved to-date and have a strong desire to ensure STAR remains as vibrant and internationally successful over the next 3 years.

RHIC is a discovery machine with STAR at center stage. Our Collaboration is composed of 63 institutions from 13 countries, with a total of over 500 collaborators. We are proud of having over 280 Ph.D. and master’s students graduate from our program, and for publishing over 230 peer-reviewed scientific papers. We have maintained a similar pace in our scientific productivity and training of the next generation of young scientists for the last 20 years. The collaboration has solidified viable approaches for clarifying fundamental phenomena such as the Chiral Magnetic Effect and Chiral Symmetry Restoration, while maintaining a scientific environment which allows for surprising discoveries (e.g. antiproton interactions and global hyperon polarization).

STAR recently published first papers from two major upgrades, the Heavy-flavor Tracker (HFT) and the Muon Telescope Detector (MTD). We are now busy installing three more, the inner Time Projection Chamber (iTPC), the event-plan detector (EPD), and the endcap Time-Of-Flight (eTOF), which will allow us to reach our high-priority scientific goals related to exploring the QCD phase diagram and seeking evidence of a critical point, during the upcoming beam energy scan II (BES-II).

Our Spin and Cold QCD research remain key features of the STAR scientific program. The 2017 RHIC run was dedicate to polarized proton-proton collisions at a center-of-mass collision energy of 510 GeV to allow us to test unique QCD predictions on relations between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scattering. These data will allow the first significant measurement of the sign change of the Sivers function, as compared to the value measured in semi-inclusive deep inelastic scattering experiments, through measurements of single spin asymmetries in W+/-, Z, direct photon and Drell-Yan production. This program has significant scientific discovery potential since the sign change measurement is a fundamental test of QCD.  These measurements will also shed light on the size and nature of the evolution of these transverse momentum dependent distributions.

We continue to develop a path forward beyond the BES-II and have identified forward instrumentation as the key upgrade post 2020. This forward proposal enables a novel scientific program, outlined in the Cold QCD plan, while expanding our rapidity acceptance to allow for a detailed study of longitudinal dynamics.

The STAR Collaboration is organized and governed by the STAR Council. The Council consists of one individual member from each member institution who will represent the individual members from that institution. We are the representatives of the Collaboration in scientific, technical, and managerial concerns, and provide continued leadership of the Collaboration. We have assembled a strong and diverse management team to work broadly within and beyond STAR to achieve our goals.

Information related to your possible visits and user required trainings for the facility is available online.

For details of recent events and publications from STAR please take a look at our STAR Focus pages

We will take the role of coSpokesperson very seriously and encourage you to contact both of us at with questions and/or comments about the STAR experiment at RHIC!

We are committed to cultivating an environment where every individual feels safe to express their ideas. Every collaborator must accept the responsibility to demonstrate civility and respect for the diversity of voices and experiences within our collaboration. Expressions or actions that disparage others are contrary to our expectations. As outlined in our bylaws, behavior that is harmful or disruptive to the work of the collaboration will not be tolerated and may result in collaboration membership being revoked.

Helen and Zhangbu

Former Spokespersons

2014 - 2017
Zhangbu Xu
Brookhaven National Laboratory

2008 - 2014
Nu Xu
Nuclear Science Division
Lawrence Berkeley National Laboratory

2002 - 2008
Tim Hallman
Brookhaven National Laboratory
Now at:
Associate Director of Science for Nuclear Physics at DOE

1991 - 2002
John Harris
Yale University (1996 --)
Lawrence Berkeley National Laboratory (1991 - 1996)

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