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The STAR detector (for Solenoidal Tracker at RHIC) is one of the four experiments at the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Laboratory, United States.

The primary scientific objective of STAR is to study the formation and characteristics of the quark-gluon plasma (QGP), a state of matter believed to exist at sufficiently high energy densities. Detecting and understanding the QGP allows physicists to understand better the Universe in the seconds after the Big Bang, when the presently-observed symmetries (and asymmetries) of the Universe were established.

Unlike other physics experiments where a theoretical prediction can be tested directly by a single measurement, STAR must make use of a variety of simultaneous studies in order to draw strong conclusions about the QGP. This is due both to the complexity of the system formed in the high-energy nuclear collision and the unexplored landscape of the physics studied. STAR therefore consists of several types of detectors, each specializing in detecting certain types of particles or characterizing their motion. These detectors work together in an advanced data acquisition and subsequent physics analysis that allows definitive statements to be made about the collision.

Introduction
In the immediate aftermath of the Big Bang, the expanding matter was so hot and dense that protons and neutrons could not exist. Instead, the early universe comprised a plasma of quarks and gluons, which in today's cool universe are confined and exist only within composite particles (bound states) &#x2013; the hadrons, such as protons and neutrons. Collisions of heavy nuclei at sufficiently high energies allow physicists to study whether quarks and gluons become deconfined at high densities, and if so, what the properties of this matter (i.e. quark–gluon plasma) are.

In particular, STAR studies the collective expansion of the hot quark-gluon matter, such as the elliptic flow. This allows to extract the transport coefficients that characterize the quark-gluon matter, including the shear and bulk viscosity, and to investigate macroscopic quantum phenomena, such as the chiral magnetic effect.

History
The STAR collaboration was formed in 1991 and the conceptual design for the experiment presented in 1992. Construction of the TPC, which occurred at LBNL, was completed in 1997. In November 1998 the $15 million detector was flown via a C5A cargo plane to Long Island and installed into the RHIC complex. First gold-gold collisions at a center of mass collision energy of 30 GeV per nucleon were recorded by STAR on June 12, 2000. Initial first results present at the Quark Matter 2001 international conference.

In 2000 the STAR collaboration consisted of ~400 collaborators from 34 institutions from 8 countries. In 2020 the collaboration has expanded to 67 institutions from 13 countries, with a total of 711 collaborators. The collaboration consists of students, university faculty and staff, national laboratory staff, and engineers.

Over the past twenty years a large variety of collision systems and collision energies have been recorded at STAR to probe the properties of nuclear matter at extreme temperatures, and understand the various contributions to the spin of the proton.

As of 2020 the STAR detector is currently the only operating experiment at RHIC, although the sPHENIX detector is expected to begin operations in ~2023.

The STAR detectors
STAR was designed as a large acceptance multipurpose experiment, and therefore consists of several types of detectors, each specializing in detecting certain types of particles or characterizing their motion. These detectors work together in an advanced data acquisition and subsequent physics analysis that allows final statements to be made about the collision. STAR is a massive detecotr that weighs 1,200 tons and is as large as a house.

The "heart" of STAR is a Time projection chamber (TPC) that sits within a 0.5T uniform magnetic field. The TPC was upgraded in 2018 by replacing the inner sectors. This iTPC project resulted in an increase in the TPC's acceptance in both rapidity and at low transverse momentum. Next radially outwards is the Time of Flight detector (ToF), followed by electro-magnetic Calorimetry (the Barrel EMCal) and a Muon Tracking Detector (MTD). At forward rapidity there is another Electro-Magnetic Calorimeter (the End-Cap Calorimeter) and the recently installed end-cap Time Of Flight (eTOF). Roman Pots sit way forward. The Event-Plane Detector (EPD), Beam-Beam Counters (BBC) , and Zero Degree Counters (ZDCs) are used a trigger detectors. There is also a high level trigger system (HLT) and the data aquisition (DAQ) to filter and record the data.

Previous sub-system detectors include the Silicon Vertex Tracker (SVT), a photon multiplicity detector (PMD) , the RICH dector the Forward TPC (FTPC) , the Foward Pion Detector (FPD) , and the Heavy Flavor Tracker (HFT).

Results
Among the most important discoveries by the STAR collaboration is the "perfect liquid".

Collaboration governance
The governance of STAR is via two branches: the institutional Council which is run by a Chairperson elected from the Council ranks, and elected Spokesperson(s) and their management team. The Spokesperson(s) represent the Collaboration in scientific, technical, and managerial concerns. The Council deals with general issues that concern the collaboration. Examples include the organization and governance of the Collaboration, adoption of bylaws and amendments thereto, the policy on admission of new members institutions to the Collaboration, and Policies for the Publication and Presentation of STAR Results.

The term of the office of the Council Chair is nominally two years. he Council elects, a Spokesperson or a team of two Spokespersons who then serve at the discretion of the Council. The normal term of office for the Spokesperson(s) is 3 years, and an individual is eligible to serve at most two consecutive terms as Spokesperson(s).

The elected Spokesperson(s) and their team of Deputies, and the Council Chairs of STAR are listed below. The Institute listed indicates the institute the person was at when they held the position.

Spokespersons

 * 2020 - Present  Spokespeople : Helen Caines (Yale), Lijuan Ruan (BNL)
 * Deputies: Kenneth Barish (UC Riverside), Xin Dong (LBNL)
 * 2017 - 2020  Spokespeople : Helen Caines (Yale), Zhangbu Xu (BNL)
 * Deputies:  Jim Drachenberg (ACU), Frank Geurts (Rice)
 * 2014 - 2017 : Zhangbu Xu (BNL)
 * Deputies : Helen Caines (Yale), Renee Fatemi (UTK), Ernst Sichtermann (LBNL)
 * 2011 - 2014 : Nu Xu (LBNL)
 * Deputies:  James Dunlop (BNL), Bedangadas Mohanty (VECC/NISER), Scott Wissink (Indiana)
 * 2008 - 2011: Nu Xu (LBNL)
 * Deputies : James Dunlop (BNL), Olga Evdokimov (UIC), Berndt Surrow (MIT)
 * 2005 - 2008 : Tim Hallman (BNL)
 * Deputies : Carl Gagliardi (Texas A&M), Hans Georg Ritter (LBNL), Helen Caines (Yale) (2007 - 2008)
 * 2002 - 2005 : Tim Hallman (BNL)
 * Deputies : Jim Thomas (LBNL), Steven Vigdor (Indiana)
 * 1991 - 2002 : John Harris (Yale)
 * Deputies : Rene Bellwied (Wayne State) (2001-2002), Tim Hallman (BNL) (1999-2000)

Council Chairpersons

 * 2016 - Present : Olga Evdokimov (UIC)
 * 2014 - 2016 : Huan Huang (UCLA)
 * 2009 - 2014 : Gary Westfall (MSU)
 * 2005 - 2008 : Hank Crawford (UC Berkeley)
 * 2003 - 2005 : Bill Christie (BNL)
 * 2000 - 2003 : Jay Marx (LBNL)