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  • richardmitnick 9:17 pm on July 19, 2017 Permalink | Reply
    Tags: , , Helen Caines, Star collaboration, ,   

    From Yale: Women in STEM -“Yale’s Helen Caines takes a leadership role in international STAR experiment” 

    Yale University bloc

    Yale University

    July 12, 2017

    Jim Shelton

    The left half of this image shows the Solenoidal Tracker at RHIC. It is a detector that specializes in tracking the thousands of particles produced by each ion collision at RHIC. The right half of the image shows the end view of a collision of two 30-billion electron-volt gold beams in the STAR detector at RHIC. (Image courtesy of STAR)

    BNL RHIC Campus

    BNL/RHIC Star Detector


    Helen Caines has spent much of her professional life immersed in cosmic soup.

    While other physicists have chased gravitational waves, cultivated qubits, and mused about dark matter, Caines has focused squarely on the thick glop of particles that transformed into nuclear matter in the first milliseconds after the Big Bang. Through studying these particles, Caines believes, humanity can come to understand the basic processes that formed the early universe at that instant.

    Now Caines is a leading voice in explaining how much we’ve learned so far and what is to come. On July 1, she became co-spokesperson for the STAR experiment, an international collaboration of more than 600 physicists searching for the theorized “critical point” that transformed the universe from a soup of quarks into what we know as matter today.

    “We’re doing very exciting physics, things we never dreamed we’d be able to do when we started,” said Caines, an associate professor of physics and member of Yale’s Wright Lab. “STAR is a testament to how innovative a collaboration can be. We have the whole range of experience, from undergraduates to emeritus professors working with us.”

    The STAR experiment is focused on the dense, hot soup of quarks and gluons — known as the quark-gluon plasma — that is believed to have existed ten millionths of a second after the Big Bang. These conditions can be recreated in the laboratory by colliding heavy ions and studying the reactions — an endeavor that still amazes Caines even after more than 20 years of research.

    “It’s just so intriguing that you can smash heavy ions together and actually learn something about the early universe from it,” she said. “It’s like smashing two automobiles together and then trying to determine the make and model of each one.”

    Helen Caines will co-lead the STAR experiment’s investigation of what happened ten millionths of a second after the Big Bang. (Photo by Michael Marsland)

    STAR launched in 1991 and is based at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.

    The experiment began collecting data in 2000. More than 60 institutions in 13 countries are part of STAR.

    Yale’s involvement in the STAR experiment runs deep. Zhangbu Xu, co-spokesperson with Caines, has a Yale Ph.D., and Yale physics professor John Harris was the founding spokesperson, serving from 1991 until 2002. Current Yale collaborators, along with Caines and Harris, are emeritus professor Jack Sandweiss; adjunct professor Thomas Ullrich; graduate students Stephen Horvat, Daniel Nemes, and David Stewart; senior research scientist Richard Majka; research scientist Nikolai Smirnov; and postdoctoral associates Saehanseul Oh and Li Yi.

    “Yale has been committed to heavy ion physics research since the founding by professor D. Allan Bromley of the original Wright Nuclear Structure Laboratory in 1966 and its various upgrades of its tandem van de Graaff accelerators,” Harris said. Yale became a member institution of the STAR experiment in 1996, when Harris arrived on campus.

    Caines joined the experiment in 1996 as well. Her work involves measuring the high-momentum particles that are produced when ultra-relativistic heavy ions are collided. Specifically, she focuses on the particles’ movement through the surrounding soup. The work is helping scientists start to understand the properties and characteristics of a new state of matter in transition.

    This is where the so-called “critical point” becomes essential to physicists. Caines has been a major proponent for a program at RHIC called Beam Energy Scan, which has successfully concluded its first phase of experiments and is in the middle of its analysis.

    “BES covers the full range of collision energies at RHIC with the primary goal of potentially discovering a critical point that is predicted to exist in the phase diagram of nuclear matter,” Harris said. “At this critical point nuclear matter transforms into a plasma of quarks and gluons in a first order phase transition, where nuclear particles as we know them coexist for an instant with quarks and gluons in a very hot phase, about 100,000 times hotter than our Sun.”

    Caines will co-lead STAR in its continuing investigation of this nuclear phase and help lead a second phase of experiments over the next few years. She and Yale graduate student Horvat have identified an approximate region in collision energy and temperature where researchers may find the critical point — a region where the hotter phase of quarks and gluons gives way to the cooler nuclear phase.

    Caines’ colleagues say she is well suited to her new role.

    “These large collaborations require a lot from a spokesperson,” said Sarah Demers, the Horace Taft Associate Professor of Physics at Yale and a member of the ATLAS experiment at CERN’s Large Hadron Collider in Geneva, Switzerland. “You need to be a physics detector expert, a physics analysis expert, and you need to be able to keep your colleagues inspired and behind a common plan. Helen is an excellent physicist, and she knows how to lead a team.”

    Caines received her Ph.D. from the University of Birmingham, U.K., in 1996. She was appointed assistant professor at Yale in 2004 and promoted to associate professor in 2010. She is a faculty member of Yale’s Wright Lab.

    Part of the satisfaction of her job, she said, is the opportunity to be surprised even after decades of research. The STAR experiment exemplifies this, she explained.

    “We’re at a very interesting stage,” Caines said. “We think we may find a place in nuclear matter, where things go wild.”

    See the full article here .

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    Yale University Campus

    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

  • richardmitnick 2:06 pm on January 6, 2017 Permalink | Reply
    Tags: , , Star collaboration   

    From BNL: “Theory Provides Roadmap in Quest for Quark Soup ‘Critical Point'” 

    Brookhaven Lab

    January 4, 2017
    Karen McNulty Walsh

    Scientists seek to discover key point in transition from early universe soup of quarks and gluons to matter as we know it.

    The nuclear theorists behind the new analysis: Swagato Mukherjee, Raju Venugopalan, and Yi Yin.

    Thanks to a new development in nuclear physics theory, scientists exploring expanding fireballs that mimic the early universe have new signs to look for as they map out the transition from primordial plasma to matter as we know it. The theory work, described in a paper recently published as an Editor’s Suggestion in Physical Review Letters (PRL), identifies key patterns that would be proof of the existence of a so-called “critical point” in the transition among different phases of nuclear matter. Like the freezing and boiling points that delineate various phases of water—liquid, solid ice, and steam—the points nuclear physicists seek to identify will help them understand fundamental properties of the fabric of our universe.

    Nuclear physicists create the fireballs by colliding ordinary nuclei—made of protons and neutrons—in an “atom smasher” called the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory.

    BNL RHIC Campus

    The subatomic smashups generate temperatures measuring trillions of degrees, hot enough to “melt” the protons and neutrons and release their inner building blocks—quarks and gluons. The collider essentially turns back the clock to recreate the “quark-gluon plasma” (QGP) that existed just after the Big Bang. By tracking the particles that emerge from the fireballs, scientists can learn about nuclear phase transitions—both the melting and how the quarks and gluons “freeze out” as they did at the dawn of time to form the visible matter of today’s world.

    “We want to understand the properties of QGP,” said nuclear theorist Raju Venugopalan, one of the authors on the new paper. “We don’t know how those properties might be used, but 100 years ago, we didn’t know how we’d use the collective properties of electrons, which now form the basis of almost all of our technologies. Back then, electrons were just as exotic as the quarks and gluons are now.”

    Changing phases

    RHIC physicists believe that two different types of phase changes can transform the hot QGP into ordinary protons and neutrons. Importantly, they suspect that the type of change depends on the collision energy, which determines the temperatures generated and how many particles get caught up in the fireball. This is similar to the way water’s freezing and boiling points can change under different conditions of temperature and the density of water molecules, Venugopalan explained.

    In low energy RHIC collisions, scientists suspect that while the change in phase from QGP to ordinary protons/neutrons occurs, both distinct states (QGP and ordinary nuclear matter) coexist—just like bubbles of steam and liquid water coexist at the same temperature in a pot of boiling water. It’s as if the quarks and gluons (or liquid water molecules) have to stop at that temperature and pay a toll before they can gain the energy needed to escape as QGP (or steam).

    In contrast, in higher energy collisions, there is no toll gate at the transition temperature where quarks and gluons must “stop.” Instead they move on a continuous path between the two phases.

    But what happens between these low-energy and high-energy realms? Figuring that out is now one of the major goals of what’s known as the “beam energy scan” at RHIC. By systematically colliding nuclei at a wide range of energies, physicists in RHIC’s STAR collaboration are searching for evidence of a special point on their map of these nuclear phases and the transitions between them—the nuclear phase diagram.

    At this so-called “critical point,” there would be a toll stop, but the cost would be $0, so the quarks and gluons could transition from protons and neutrons to QGP very quickly—almost as if all the water in the pot turned to steam in a single instant. This can actually happen when water reaches its boiling point under high pressure, where the distinction between the liquid and the compressed gas phases blurs to the point of the two being virtually indistinguishable. In the case of QGP, the physicists would expect to see signs of this dramatic effect—patterns in the fluctuations of particles observed striking their detectors—the closer and closer they get to this critical point.

    In experiments already conducted at the intermediate energies, STAR physicists have observed such patterns, which may be signs of the hypothesized critical point. This search will continue with increased precision over a wider range of energies during a second beam energy scan, beginning in 2019. The new theoretical work of Brookhaven physicist Swagato Mukherjee, Venugopalan, and former postdoc Yi Yin (now at MIT)—part of a newly funded Beam Energy Scan Theory (BEST) Topical Collaboration in Nuclear Theory—will provide a roadmap to guide the experimental researchers.

    The STAR collaboration’s exploration of the “nuclear phase diagram” shows signs of a sharp border—a first-order phase transition—between the hadrons that make up ordinary atomic nuclei and the quark-gluon plasma (QGP) of the early universe when the QGP is produced at relatively low energies/temperatures. The data may also suggest a possible critical point, where the type of transition changes from the abrupt, first-order kind to a continuous crossover at higher energies.

    BNL/RHIC Star Detector
    BNL/RHIC Star Detector

    Signposts to look for

    Certain characteristics of the patterns that occur during phase changes are universal—no matter whether you are studying water, or quarks and gluons, or magnets. But one key advance of the new theory work was using a different set of universal characteristics to account for the dynamic conditions of the expanding quark-gluon plasma.

    “All the predictions, the way we started looking for a critical point so far, were based on patterns calculated assuming you have a pot boiling on a stove—a somewhat static system,” said Mukherjee. “But QGP is expanding and changing over time. It’s more like water boiling as it flows rapidly through a pipe.”

    To account for the evolving conditions of the QGP in their calculations, the theorists incorporated “dynamic universalities” that were first developed to describe similar pattern formation in the cosmological expansion of the universe itself.

    “These ideas have since been applied to other systems like liquid helium and liquid crystals,” Venugopalan said. “Yin realized that the specific mechanisms of dynamic universality identified in cosmology and condensed matter systems can be applied to the search for the critical point in heavy ion collisions. This paper is the first explicit demonstration of this conjecture.”

    Specifically, the paper predicts exactly what patterns to look for in the data—patterns in how the properties of particles emitted from the collisions are correlated—as the energy of the collisions changes.

    “If the STAR collaboration looks at the data in a particular way and sees these patterns, they can claim without any ambiguity that they have seen a critical point,” Venugopalan said.

    The Beam Energy Scan Theory Collaboration and research at RHIC are supported by the DOE Office of Science.

    Related Links

    Scientific paper: Universal Off-Equilibrium Scaling of Critical Cumulants in the QCD Phase Diagram

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

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