physics

Relativistic Heavy Ion Collider

Relativistic Heavy Ion Collider is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Relativistic Heavy Ion Collider rather than just read about it. In short: The Relativistic Heavy Ion Collider (RHIC ) is the first and one of only two operating heavy-ion colliders, and the only spin-polarized proton collider ever built. Located at Brookhaven National Laboratory (BNL) in Upton, New York, and used by an international team of researchers, it was the last operating particle collider in the US.

Key takeaways

Relativistic Heavy Ion Collider belongs to physics; place it in that map before memorising details.
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Reproduce the core statement of Relativistic Heavy Ion Collider from memory before moving on to harder problems.

Reference excerpt

The Relativistic Heavy Ion Collider (RHIC ) is the first and one of only two operating heavy-ion colliders, and the only spin-polarized proton collider ever built. Located at Brookhaven National Laboratory (BNL) in Upton, New York, and used by an international team of researchers, it was the last operating particle collider in the US. By using RHIC to collide ions traveling at relativistic speeds, physicists study the primordial form of matter that existed in the universe shortly after the Big Bang. By colliding spin-polarized protons, the spin structure of the proton is explored. RHIC was the second-highest-energy heavy-ion collider in the world, with nucleon energies for collisions reaching 100 GeV for gold ions and 250 GeV for protons. As of November 7, 2010, the Large Hadron Collider (LHC) has collided heavy ions of lead at higher energies than RHIC. The LHC operating time for ions (lead–lead and lead–proton collisions) is limited to about one month per year. In 2010, RHIC physicists published results of temperature measurements from earlier experiments which concluded that temperatures in excess of 345 MeV (4 terakelvin or 7 trillion degrees Fahrenheit) had been achieved in gold ion collisions, and that these collision temperatures resulted in the breakdown of "normal matter" and the creation of a liquid-like quark–gluon plasma. In January 2020, the US Department of Energy Office of Science selected the eRHIC design for the future Electron–Ion collider (EIC), building on the existing RHIC facility at BNL. RHIC had its last collisions and ended data collection on 6 February 2026.

The accelerator RHIC is an intersecting storage ring particle accelerator. Two independent rings (arbitrarily denoted as "Blue" and "Yellow") circulate heavy ions and/or polarized protons in opposite directions and allow a virtually free choice of colliding positively charged particles (the eRHIC upgrade will allow collisions between positively and negatively charged particles). The RHIC double storage ring is hexagonally shaped and has a circumference of 3834 m, with curved edges in which stored particles are deflected and focused by 1,740 superconducting magnets using niobium-titanium conductors. The dipole magnets operate at 3.45 T. The six interaction points (between the particles circulating in the two rings) are in the middle of the six relatively straight sections, where the two rings cross, allowing the particles to collide. The interaction points are enumerated by clock positions, with the injection near 6 o'clock. Two large experiments, STAR and sPHENIX, are located at 6 and 8 o'clock respectively. The sPHENIX experiment is the newest experiment to be built at RHIC, replacing PHENIX at the 8 o'clock position. A particle passes through several stages of boosters before it reaches the RHIC storage ring. The first stage for ions is the electron beam ion source (EBIS), while for protons, the 200 MeV linear accelerator (Linac) is used. As an example, gold nuclei leaving the EBIS have a kinetic energy of 2 MeV per nucleon and have an electric charge Q = +32 (32 of 79 electrons stripped from the gold atom). The particles are then accelerated by the Booster synchrotron to 100 MeV per nucleon, which injects the projectile now with Q = +77 into the Alternating Gradient Synchrotron (AGS), before they finally reach 8.86 GeV per nucleon and are injected in a Q = +79 state (no electrons left) into the RHIC storage ring over the AGS-to-RHIC Transfer Line (AtR). To date the types of particle combinations explored at RHIC are p + p, p + Al, p + Au, d + Au, h + Au, Cu + Cu, Cu + Au, Zr + Zr, Ru + Ru, Au + Au, U + U O+O. The projectiles typically travel at 99.995% of the speed of light. For Au + Au collisions, the center-of-mass energy is typically 200 GeV per nucleon-pair, and was as low as 7.7 GeV per nucleon-pair. An average luminosity of 2×1026 cm−2⋅s−1 was targeted during the planning. The current average Au + Au luminosity of the collider has reached 87×1026 cm−2⋅s−1, 44 times the design value. The heavy ion luminosity is substantially increased through stochastic cooling. One unique characteristic of RHIC is its capability to collide polarized protons. RHIC holds the record of highest energy polarized proton beams. Polarized protons are injected into RHIC and preserve this state throughout the energy ramp. This is a difficult task that is accomplished with the aid of corkscrew magnetics called 'Siberian snakes' (in RHIC a chain 4 helical dipole magnets). The corkscrew induces the magnetic field to spiral along the direction of the beam Run-9 achieved center-of-mass energy of 500 GeV on 12 February 2009. In Run-13 the average p + p luminosity of the collider reached 160×1030 cm−2⋅s−1, with a time and intensity averaged polarization of 52%. AC dipoles have been used in non-linear machine diagnostics for the first time in RHIC.

The experiments There are two detectors currently operating at RHIC: STAR (6 o'clock, and near the AGS-to-RHIC Transfer Line) and sPHENIX (8 o'clock), the successor to PHENIX. PHOBOS (10 o'clock) completed its operation in 2005, and BRAHMS (2 o'clock) in 2006. Among the two larger detectors, STAR is aimed at the detection of hadrons with its system of time projection chambers covering a large solid angle and in a conventionally generated solenoidal magnetic field, while PHENIX is further specialized in detecting rare and electromagnetic particles, using a partial coverage detector system in a superconductively generated axial magnetic field. The smaller detectors have larger pseudorapidity coverage, PHOBOS has the largest pseudorapidity coverage of all detectors, and tailored for bulk particle multiplicity measurement, while BRAHMS is designed for momentum spectroscopy, in order to study the so-called "small-x" and saturation physics. There is an additional experiment, PP2PP (now part of STAR), investigating spin dependence in p + p scattering. The spokespersons for each of the experiments are:

STAR: Frank Geurts (Rice University) PHENIX: Yasuyuki Akiba (Riken) sPHENIX: Megan Connors (Georgia State University) and Jin Huang (Brookhaven National Laboratory)

Current results

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Illustrations

Worked examples

Example 1 — a first encounter with Relativistic Heavy Ion Collider

Start with the simplest possible case. Write down what Relativistic Heavy Ion Collider claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Relativistic Heavy Ion Collider before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Relativistic Heavy Ion Collider ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Relativistic Heavy Ion Collider

In research: Relativistic Heavy Ion Collider appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Relativistic Heavy Ion Collider in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Relativistic Heavy Ion Collider is common in secondary-school and first-year university syllabi. It links to neighbouring topics Brookhaven National Laboratory, Laboratories in the United States, Particle accelerators, so understanding it makes those chapters shorter.
In everyday life: Look for Relativistic Heavy Ion Collider outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Relativistic Heavy Ion Collider in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Relativistic Heavy Ion Collider means in your own words.
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Frequently asked questions

What is Relativistic Heavy Ion Collider in simple terms?

Why does Relativistic Heavy Ion Collider matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Relativistic Heavy Ion Collider?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Relativistic Heavy Ion Collider.