From Jefferson Laboratory: “The Weak Side of the Proton”


From Jefferson Laboratory

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The Q-weak experiment was conducted in Jefferson Lab’s Experimental Hall C, and its goal was to very precisely measure the proton’s weak charge, a term that quantifies the influence that the weak force can exert on protons. The Q-weak apparatus, shown here, was installed in the hall for the experimental run, which concluded in 2012.

5.9.18

Kandice Carter
757-269-7263
kcarter@jlab.org

A new result from the Q-weak experiment at the Department of Energy’s Thomas Jefferson National Accelerator Facility provides a precision test of the weak force, one of four fundamental forces in nature. This result, published recently in Nature, also constrains possibilities for new particles and forces beyond our present knowledge.

“Precision measurements like this one can act as windows into a world of potential new particles that otherwise might only be observable using extremely high-energy accelerators that are currently beyond the reach of our technical capabilities,” said Roger Carlini, a Jefferson Lab scientist and a co-spokesperson for the Q-weak Collaboration.

While the weak force is difficult to observe directly, its influence can be felt in our everyday world. For example, it initiates the chain of reactions that power the sun and it provides a mechanism for radioactive decays that partially heat the Earth’s core and that also enable doctors to detect disease inside the body without surgery.

Now, the Q-weak Collaboration has revealed one of the weak force’s secrets: the precise strength of its grip on the proton. They did this by measuring the proton’s weak charge to high precision, which they probed using the high-quality beams available at the Continuous Electron Beam Accelerator Facility, a DOE Office of Science User Facility.

The proton’s weak charge is analogous to its more familiar electric charge, a measure of the influence the proton experiences from the electromagnetic force. These two interactions are closely related in the Standard Model, a highly successful theory that describes the electromagnetic and weak forces as two different aspects of a single force that interacts with subatomic particles.

To measure the proton’s weak charge, an intense beam of electrons was directed onto a target containing cold liquid hydrogen, and the electrons scattered from this target were detected in a precise, custom-built measuring apparatus. The key to the Q-weak experiment is that the electrons in the beam were highly polarized – prepared prior to acceleration to be mostly “spinning” in one direction, parallel or anti-parallel to the beam
direction. With the direction of polarization rapidly reversed in a controlled manner, the experimenters were able to latch onto the weak interaction’s unique property of parity (akin to mirror symmetry) violation, in order to isolate its tiny effects to high precision: a different scattering rate by about 2 parts in 10 million was measured for the two beam polarization states.

The proton’s weak charge was found to be QWp=0.0719±0.0045, which turns out to be in excellent agreement with predictions of the Standard Model, which takes into account all known subatomic particles and the forces that act on them.

The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.


Standard Model of Particle Physics from Symmetry Magazine

Because the proton’s weak charge is so precisely predicted in this model, the new Q-weak result provides insight into predictions of hitherto unobserved heavy particles, such as those that may be produced by the Large Hadron Collider (LHC) at CERN in Europe or future high energy particle accelerators.

LHC

CERN/LHC Map

CERN LHC Tunnel

CERN LHC particles

“This very challenging experimental result is yet another clue in the world-wide search for new physics beyond our current understanding. There is ample evidence the Standard Model of Particle physics provides only an incomplete description of nature’s phenomena, but where the breakthrough will come remains elusive,” said Timothy J. Hallman, Associate Director for Nuclear Physics of the Department of Energy Office of Science. “Experiments like Q-weak are pressing ever closer to finding the answer.”

For example, the Q-weak result has set limits on the possible existence of leptoquarks, which are hypothetical particles that can reverse the identities of two broad classes of very different fundamental particles – turning quarks (the building blocks of nuclear matter) into leptons (electrons and their heavier counterparts) and vice versa.

“After more than a decade of careful work, Q-weak not only informed the Standard Model, it showed that extreme precision can enable moderate-energy experiments to achieve results on par with the largest accelerators available to science,” said Anne Kinney, Assistant Director for the Mathematical and Physical Sciences Directorate at the National Science Foundation. “Such precision will be important in the hunt for physics beyond the Standard Model, where new particle effects would likely appear as extremely tiny deviations.”

“It’s complementary information. So, if they find evidence for new physics in the future at the LHC, we can help identify what it might be, from the limits that we’re setting already in this paper,” said Greg Smith, Jefferson Lab scientist and Q-weak project manager.

The Q-weak Collaboration consists of about 100 scientists and more than 20 institutions. The experiment was funded by the U.S. Department of Energy Office of Science, the National Science Foundation, the Natural Sciences and Engineering Research Council of Canada, and the Canadian Foundation for Innovation, with matching and in-kind contributions from a number of the collaborating institutions.

See the full article here .

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Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science.

Jefferson Lab is supported by the Office of Science of the U.S. Department of Energy. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.
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From JLab: “First Result from Jefferson Lab’s Upgraded CEBAF Opens Door to Exploring the Universal Glue”

Jefferson Laboratory

May 3, 2017
Kandice Carter
kcarter@jlab.org
757-269-7263

1
Jefferson Lab’s Experimental Hall D.

An experiment designed to detail the inner workings of the strong force inside matter reports its first data.

The first experimental result has been published from the newly upgraded Continuous Electron Beam Accelerator Facility (CEBAF) at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility. The result demonstrates the feasibility of detecting a potential new form of matter to study why quarks are never found in isolation.

The 12 GeV CEBAF Upgrade is a $338 million, multi-year project to triple CEBAF’s original operational energy for investigating the quark structure of the atom’s nucleus. The majority of the upgrade is complete and will be finishing up in 2017.

Scientists have been rigorously commissioning the experimental equipment to prepare for a new era of nuclear physics experiments. These activities have already led to the first scientific result, which comes from the Gluonic Excitations Experiment. GlueX conducts studies of the strong force, which glues matter together, through searches for hybrid mesons.

According to Curtis Meyer, a professor of physics at Carnegie Mellon University and spokesperson for the GlueX experiment at Jefferson Lab, these hybrid mesons are built of the same stuff as ordinary protons and neutrons, which are quarks bound together by the “glue” of the strong force. But unlike ordinary mesons, the glue in hybrid mesons behaves differently.

“The basic idea is that a meson is a quark and antiquark bound together, and our understanding is that the glue holds those together. And that glue manifests itself as a field between the quarks. A hybrid meson is one with that strong gluonic field being excited,” Meyer explains.

He says that producing these hybrid mesons allows nuclear physicists to study particles in which the strong gluonic field is contributing directly to their properties. The hybrid mesons may ultimately provide a window into how subatomic particles are built by the strong force, as well as “quark confinement” – why no quark has ever been found alone.

“We hope to show that this “excited” gluonic field is an important constituent of matter. That’s something that has not been observed in anything that we’ve seen so far. So, in some sense, it’s a new type of hadronic matter that has not been observed,” he says.

In this first result, data were collected over a two-week period following equipment commissioning in the spring of 2016. The experiment produced two ordinary mesons called the neutral pion and the eta, and the production mechanisms of these two particles were carefully studied.

The experiment takes advantage of the full-energy, 12 GeV electron beam produced by the CEBAF accelerator and delivered into the new Experimental Hall D complex. There, the 12 GeV beam is converted into a first-of-its-kind 9 GeV photon beam.

“The photons go through our liquid hydrogen target. Some of them will interact with a proton in that target, something is exchanged between the photon and the proton, and something is kicked out – a meson,” Meyer explains. “This publication looked at some of the simplest mesons you could kick out. But it’s the same, basic production mechanism that most of our reactions will follow.”

The result was published as a Rapid Communication in the April issue of Physical Review C. It demonstrated that the linear polarization of the photon beam provides important information by ruling out possible meson production mechanisms.

“It’s not so much that the particles we created were interesting, but how they were produced: Learning what reactions were important in making them,” Meyer says.

The next step for the collaboration is further analysis of data already collected and preparations for the next experimental run in the fall.

“I’m sure that we’ve produced hybrid mesons already, we just don’t have enough data to start looking for them yet,” Meyer says. “There are a number of steps that we’re going through in terms of understanding the detector and our analysis. We’re doing the groundwork now, so that we’ll have confidence that we understand things well enough that we can validate results we’ll be getting in the future.”

“This new experimental facility – Hall D – was built by dedicated efforts of the Jefferson Lab staff and the GlueX collaboration,” says Eugene Chudakov, Hall D group leader. “It is nice to see that all of the equipment, including complex particle detectors, is operating as planned, and the exciting scientific program has successfully begun.”

The 12 GeV CEBAF Upgrade project is in its last phase of work and is scheduled for completion in September. Other major experimental thrusts for the upgraded CEBAF include research that will enable the first snapshots of the 3D structure of protons and neutrons, detailed explorations of the internal dynamics and quark-gluon structure of nuclei, and tests of fundamental theories of matter.

See the full article here .

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Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science.

Jefferson Lab is supported by the Office of Science of the U.S. Department of Energy. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.
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From JLab: “Innovative device allows 3D imaging of the breast with less radiation”

6.21.16
Kandice Carter,
Jefferson Lab Public Affairs
757-269-7263
kcarter@jlab.org

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Adding this variable angle slant hole collimator to an existing breast molecular imaging system allows the system to get six times better contrast of cancer lesions in the breast, providing the same or better image quality while also potentially reducing the radiation dose to the patient by half.

Preliminary tests have demonstrated that a new device may enable existing breast cancer imagers to provide up to six times better contrast of tumors in the breast, while maintaining the same or better image quality and halving the radiation dose to patients. The advance is made possible by a new device developed for 3D imaging of the breast by researchers at the Department of Energy’s Thomas Jefferson National Accelerator Facility, Dilon Technologies and the University of Florida Department of Biomedical Engineering.

In breast cancer screening, mammography is the gold standard. But about half of all women who follow standard screening protocol for 10 years will receive a false-positive result that will require additional screening, particularly women who have dense breast tissue. Used in conjunction with mammography, imaging based on nuclear medicine is currently being used as a successful secondary screening alongside mammography to reduce the number of false positive results in women with dense breasts and at higher risk for developing breast cancer.

Now, researchers are hoping to improve this imaging technique, known as molecular breast imaging or breast specific gamma imaging, with better image quality and precise location (depth information) within the breast, while reducing the amount of radiation dose to the patient for these procedures.

According to Drew Weisenberger, leader of the Jefferson Lab Radiation Detector and Imaging Group, a new device called a variable angle slant hole collimator provides all of these benefits and more. When used in a molecular breast imager, the device has just demonstrated in early studies to capture 3D molecular breast images at higher resolution than current 2D scans in a format that may be used alongside 3D digital mammograms.

“These results really focus on the breast. We hope to build on this to perhaps improve the imaging of other organs,” Weisenberger said.

The new device replaces a component in existing molecular breast imagers.

While a mammogram uses X-rays to show the structure of breast tissue, molecular breast imagers show tissue function. For instance, cancer tumors are fast growing, so they gobble up certain compounds more rapidly that healthy tissue. A radiopharmaceutical made of such a compound will quickly accumulate in tumors. A radiotracer attached to the molecule gives off gamma rays, which can be picked up by the molecular breast imager.

“You can image that accumulation external to the breast by using a gamma camera,” said Weisenberger.

Current molecular breast imaging systems use a traditional collimator, which is essentially a rectangular plate of dense metal with a grid of holes, to “filter” the gamma rays for the camera. The collimator only allows the system to pick up the gamma rays that come straight out of the breast, through the holes of collimator, and into the imager. This provides for a clear, well-defined image of any cancer tumors.

The variable angle slant hole collimator, or VASH collimator, is constructed from a stack of 49 tungsten sheets, each one a quarter of a millimeter thick and containing an identical array of square holes. The sheets are stacked like a deck of cards, with angled edges on two sides. The angle of the array of square holes in the stack can be easily slanted by two small motors that slide the individual sheets by their edges. The result is a systematic varying of the focusing angle of the collimator during the imaging procedure.

“Now, you can get a whole range of angles of projections of the breast without moving the breast or moving the imager. You’re able to come in real close, you’re able to compress the breast, and you can get a one-to-one comparison to a 3D mammogram,” Weisenbeger explained.

In a recent test of the system, the researchers evaluated the spatial resolution and contrast-to-noise ratio in images of a “breast phantom,” a plastic mockup of a breast with four beads inside simulating cancer tumors of varying diameter that are marked with a radiotracer. They found that using the VASH collimator with an existing breast molecular imaging system, they could get six times better contrast of tumors in the breast, which could potentially reduce the radiation dose to the patient by half from the current levels, while maintaining the same or better image quality. The test results match a published paper that predicted this performance via a Monte Carlo simulation.

The collimator was built at Jefferson Lab and the test results were analyzed at the University of Florida with funds provided by a Commonwealth Research Commercialization Fund grant from the Commonwealth of Virginia’s Center for Innovative Technology, and with matching support provided by Dilon Technologies.

The test results were presented at the 2016 Society of Nuclear Medicine and Molecular Imaging Annual Meeting in San Diego on June 13. The technologies developed for the Variable Angle Slant Hole Collimator are included in two filings to the U.S. Patent and Trademark Office.

See the full article here .

Please help promote STEM in your local schools.

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Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science.

Jefferson Lab is supported by the Office of Science of the U.S. Department of Energy. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.

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From JLab: “Award enables research for more efficient accelerators”

May 12, 2016
Kandice Carter
Jefferson Lab Public Affairs
757-269-7263
kcarter@jlab.org

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A furnace system designed by Jefferson Lab Staff Scientist Grigory Eremeev and his colleagues adds tin to the inside surface of niobium cavities. A niobium test cavity and tin are placed inside and heated up to 1200 degrees Celsius. At that temperature, the tin is vaporized by the heat. The tin vapor bonds to the inner surface of the niobium cavity, producing a layer of niobium-tin that is just a few thousandths of a millimeter thick.

Grigory Eremeev wants to double the efficiency of some of the most efficient particle accelerators being used for research. Now, the staff scientist at the Department of Energy’s Thomas Jefferson National Accelerator Facility has just been awarded a five-year grant through DOE’s Early Career Research Program to do just that.

Managed by the DOE’s Office of Science, the program provides support to exceptional researchers during the crucial early career years, when many scientists do their most formative work. Eremeev is one of 49 awardees this year, which includes 22 from the National Labs and 27 from universities. His award includes $500K per year for five years.

“We invest in promising young researchers early in their careers to support lifelong discovery science to fuel the nation’s innovation system,” said Cherry Murray, director of DOE’s Office of Science. “We are proud of the accomplishments these young scientists already have made, and look forward to following their achievements in years to come.”

Eremeev works with accelerator components made of a metal called niobium. Niobium is a shiny silver metal that becomes a superconductor when chilled to just a few degrees above absolute zero.

For use in an accelerator, the niobium is formed into specially shaped accelerating structures called cavities. Niobium cavities harness and impart energy onto particles, thereby “accelerating” the particles for use in nuclear physics experiments for exploring the particles inside the nucleus of the atom.

Superconducting niobium cavities can store energy with almost no losses, allowing the structures to accelerate a continuous beam of particles. Jefferson Lab’s Continuous Electron Beam Accelerator Facility was the first large-scale accelerator to use this technology.

Jlab CEBAF
Jlab CEBAF

Because of its efficiency, CEBAF has been used to conduct many experiments in the nucleus of the atom that weren’t thought possible before, and a recent upgrade of the machine has taken advantage of new technology advances, yielding even more efficient accelerator cavities.

But Eremeev thinks that these structures can be further improved, so he and his colleagues are looking at ways to optimize the preparation of these structures to coax improved performance from them.

“We are trying new techniques to reach the potential of the material. So, we are trying different parameters to get better performance,” Eremeev says.

One of the most promising new parameters that Eremeev and his colleagues are testing is the addition of other superconducting metals to the surface of niobium accelerator cavities, such as tin. Like niobium, tin is a shiny metal that becomes superconducting when cooled to low temperatures. The researchers are working to mix tin with the surface layer of niobium on the inside of the cavities to produce a thin layer of niobium-tin (called Nb3Sn). It’s thought that this alloy will provide a more efficient superconducting surface than pure niobium.

Eremeev and his colleagues designed and constructed a furnace system to add tin to the inside surface of niobium cavities. A niobium cavity and tin are placed inside and heated up to 1200 degrees Celsius. At that temperature, the tin is vaporized by the heat. The tin vapor bonds to the inner surface of the niobium cavity, producing a layer of niobium-tin that is just a few thousandths of a millimeter thick.

Eremeev says the niobium-tin cavities have already shown great promise in initial testing.

“We want to understand and push the limits of the niobum-tin, trying to approach, as close as we can, the performance limitation of the superconductor,” he says.

For instance, the niobium-tin cavities will stay superconducting at twice the temperatures that are needed for pure niobium accelerating cavities, which could provide significant operational cost savings for future accelerators using the technology.

In the 12 GeV CEBAF, for instance, the niobium cavities must be kept near 2 Kelvin (-456 degrees Fahrenheit) when operating, which requires 10 MW of power to refrigerate. At double that temperature, 4 Kelvin, there is the potential to only require 6.5 MW of power, a significant savings.

So far, tests of this new type of accelerator cavity have been limited to R&D units. Eremeev says the next step is to produce two full-size cavities and install them in a section of accelerator for testing under real-world operating conditions, a goal that is now made possible by the DOE Early Career Research Program grant.

“We need to demonstrate it in a CEBAF five-cell cavity to show that it works,” he says.

Jefferson Lab is a world-leading nuclear physics research laboratory devoted to the study of the building blocks of matter inside the atom’s nucleus – quarks and gluons – that make up 99 percent of the mass of our visible universe. Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.

See the full article here .

Please help promote STEM in your local schools.

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Thomas Jefferson National Accelerator Facility is managed by Jefferson Science Associates, LLC for the U.S. Department of Energy

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From Jlab via DOE: “Why Physics Needs Diamonds”

April 26, 2016
Kandice Carter

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A detailed view of the diamond wafers scientists use to get a better measure of spinning electrons. | Photo courtesy of Jefferson Lab.

Diamonds are one of the most coveted gemstones. But while some may want the perfect diamond for its sparkle, physicists covet the right diamonds to perfect their experiments. The gem is a key component in a novel system at Jefferson Lab that enables precision measurements to discover new physics in the sub-atomic realm — the domain of the particles and forces that build the nucleus of the atom.

Explorations of this realm require unique probes with just the right characteristics, such as the electrons that are prepared for experiments inside the Continuous Electron Beam Accelerator Facility [CEBAF] at Jefferson Lab.

Jlab CEBAF
Jlab CEBAF

CEBAF is an atom smasher. It can take ordinary electrons and pack them with just the right energy, group them together in just the right number and set those groups to spinning in just the right way to probe the nucleus of the atom and get the information that physicists want.

But to ensure that electrons with the correct characteristics have been dialed up for the job, nuclear physicists need to be able to measure the electrons before they are sent careening into the nucleus of the atom. That’s where the diamonds in a device called the Hall C Compton Polarimeter come in. The polarimeter measures the spins of the groups of electrons that CEBAF is about to use for experiments.

This quantity, called the beam polarization, is a key unit in many experiments. Physicists can measure it by shining laser light on the electrons as they pass by on their way to an experiment. The light will knock some of the electrons off the path, where they’re gathered up into a detector to be counted, a procedure that yields the beam polarization.

Ordinarily, this detector would be made of silicon, but silicon is relatively easily damaged when struck by too many particles. The physicists needed something a bit hardier, so they turned to diamond, hoping it could also be a physicist’s best friend.

The Hall C Compton Polarimeter uses a novel detector system built of thin wafers of diamond. Specially lab-grown plates of diamond, measuring roughly three-quarters of an inch square and a mere two hundredths of an inch thick, are outfitted like computer chips, with 96 tiny electrodes stuck to them. The electrodes send a signal when the diamond detector counts an electron.

This novel detector was recently put to the test, and it delivered. The detector provided the most direct and accurate measurement to date of electron beam polarization at high current in CEBAF.

But the team isn’t resting on its laurels: New experiments for probing the subatomic realm will require even higher accuracies. Now, the physicists are focused on improving the polarimeter, so that its diamonds will be ready to sparkle for the next precision experiment.

See the full article here .

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From JLab: “Jefferson Lab Accelerator Delivers Its First 12 GeV Electrons”

December 21, 2015
Kandice Carter, Jefferson Lab Public Affairs
757-269-7263
kcarter@jlab.org

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On December 14, full-energy 12 GeV electron beam was provided for the first time, to the Experimental Hall D complex, located in the upper, left corner of this aerial photo of the Continuous Electron Beam Accelerator Facility. Hall D is the new experimental research facility – added to CEBAF as part of the 12 GeV Upgrade project. Beam was also delivered to Hall A (dome in the lower left).

The newly upgraded accelerator at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has delivered full-energy electrons as part of commissioning activities for the ongoing 12 GeV Upgrade project. At 4:20 p.m. on Monday, Dec. 14, operators of the Continuous Electron Beam Accelerator Facility (CEBAF) delivered the first batch of 12 GeV electrons (12.065 GeV) to its newest experimental hall complex, Hall D.

“Through part of the ongoing upgrade process, we have refurbished or replaced virtually every one of the many thousands of components in CEBAF,” said Allison Lung, deputy project manager for the CEBAF 12 GeV Upgrade project and Jefferson Lab assistant director. “Now, to see the machine already reaching its top design energy – It’s a testament to the hard work of the many Jefferson Lab staff members who have made it possible.”

The 12 GeV Upgrade project, which is scheduled to be completed in September 2017, was designed to enable the machine to provide 12 GeV electrons, which is triple its original design and double its maximum operational energy before the upgrade. By increasing the energy of the electrons, scientists are increasing the resolution of the CEBAF microscope for probing ever more deeply into the nucleus of the atom. The $338 million upgrade entails adding ten new acceleration modules and support equipment to CEBAF, as well as construction of a fourth experimental hall, upgrades to instrumentation in the existing halls, and other upgrade components.

“The CEBAF accelerator commissioning and achievement of the design energy required hard work, patience and teamwork,” said Arne Freyberger, Jefferson Lab’s director of accelerator operations. “It’s just fantastic to watch it all come together, and the sense of accomplishment is palpable.”

Once the upgrade is complete, CEBAF will become an unprecedented tool for the study of the basic building blocks of the visible universe. It will be able to deliver 11 GeV electrons into its original experimental areas, Halls A, B and C for experiments. The full-energy, 12 GeV electrons are now being provided to the Experimental Hall D complex to initiate studies of the force that glues matter together. In Hall D, scientists hope to produce new particles, called hybrid mesons. Hybrid mesons are made of quarks bound together by the strong force, the same building blocks of protons and neutrons, but in hybrid mesons, this force is somewhat modified. It’s hoped that observing these hybrid mesons and revealing their properties will offer a new window into the inner workings of matter.

“This kind of science explores the most fundamental mysteries: Why are we here? Why is it that one particular combination of quarks and forces takes on that material property, while a different combination of quarks and forces makes up the human body?” Lung said. “One particularly compelling question that scientists have had, is why do we always find quarks bound together in two and threes, but never alone? We will have an entirely unique facility designed to answer the question.”

Jefferson Lab is a world-leading nuclear physics research laboratory devoted to the study of the building blocks of matter inside the atom’s nucleus – quarks and gluons – that make up 99 percent of the mass of our visible universe. Jefferson Science Associates, LLC, a joint venture of the Southeastern Universities Research Association, Inc. and PAE Applied Technologies, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.

See the full article here .

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Thomas Jefferson National Accelerator Facility is managed by Jefferson Science Associates, LLC for the U.S. Department of Energy

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From Nature: “Billion-dollar particle collider gets thumbs up”

Nature Mag
Nature

19 May 2015
Edwin Cartlidge

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Brookhaven National Laboratory in New York is a potential host for the Electron-Ion Collider. Brookhaven National Laboratory/CC BY-NC-ND 2.0

A machine that would allow scientists to peer deeper than ever before into the atomic nucleus is a big step closer to being built. A high-level panel of nuclear physicists is expected to endorse the proposed Electron-Ion Collider (EIC) in a report scheduled for publication by October. It is unclear how long construction would take.

The panel is the [DOE] Nuclear Science Advisory Committee, or NSAC, which produces regular ten-year plans for the US Department of Energy (DOE) and the National Science Foundation. Its latest plan is still being finalized, but NSAC’s long-range planning group “strongly recommended” construction of the EIC at a meeting last month, says NSAC member Abhay Deshpande, a nuclear physicist at Stony Brook University in New York. The EIC will almost certainly be formally endorsed in the NSAC report, he says. It must then be approved by the DOE, but most projects backed by the expert panel have come to fruition, he says.

The collider would allow unprecedented insights into how protons and neutrons are built up from quarks and the particles that act between them, known as gluons.

The current leading facilities for studying quark–gluon matter are the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, New York, and the Large Hadron Collider at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland.

BNL RHIC Campus
BNL RHIC
BNL RHIC

CERN LHC Map
CERN LHC Grand Tunnel
CERN LHC particles
CERN LHC

These facilities smash protons and heavy ions together to recreate the energetic conditions of the early Universe, when quarks and gluons existed as a plasma rather than in atomic nuclei. The EIC would collide point-like electrons with either protons or heavy ions, generating collisions that have a similarly high energy but are more precise and so can be used to study subatomic particles in detail.

In particular, the EIC would be ideal for studying an exotic state of matter that is made up entirely of gluons. The machine should also solve a puzzle about the proton that has baffled physicists for nearly 30 years. The proton has a quantum-mechanical property called spin, but, strangely, the spins of its three constituent quarks add up to only about one-third of its own spin. The EIC would determine what makes up the difference: options include the spin of the proton’s gluons, the angular momentum of its quarks or of the gluons from their orbital motion, or a mixture of all three.

“Until we have the EIC, there are huge areas of nuclear physics that we are not going to make progress in,” says Donald Geesaman, a nuclear physicist at Argonne National Laboratory in Illinois, and the chair of NSAC.

The machine would not be built from scratch. One option is to add an electron-beam facility to RHIC — a plan that is estimated to cost about US$1 billion and would depend on some as-yet-unproven technologies. Another is to add an ion accelerator and new collider rings to the Continuous Electron Beam Accelerator Facility [CEBAF] at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, which would cost about $1.5 billion.

Jlab CEBAF
CEBAF at JLab

Deshpande hopes that the DOE will give the collider the thumbs up within a year of the NSAC plan’s publication. Two or three more years would be needed to finalize the competing bids and choose one, meaning that construction could start in about 2020 and be completed five years later, he says.

Others say that this outlook is too rosy. The 2008 financial crisis led to a drop in science funding that forced NSAC to review its 2007 ten-year plan. A specially formed subcommittee concluded in 2013 that RHIC would have to shut down if funding for the DOE’s Office of Nuclear Physics remained flat over the following five years. In fact, those funds have grown slightly, keeping RHIC in business, but the scare led to a more cautious approach this time around, says Geesaman. He points out that when the DOE and the National Science Foundation commissioned the ten-year plan, they specified that NSAC should consider what US physicists could achieve if funding remained flat, as well as how much support they would need to maintain a “world-leadership position”.

Robert McKeown, deputy director for science at the Jefferson lab, thinks that limited funds might delay the start up of the EIC until at least 2030. And Michael Lubell, director of public affairs at the American Physical Society, questions whether it is feasible for the EIC to be built by the United States alone. He notes that the $1.5-billion Long-Baseline Neutrino Experiment became an international project [DUNE managed by FNAL] after a slimmed-down $600-million version failed to pass scientific muster. “It is hard to see how to do this unless you get international buy-in,” he says.

Deshpande thinks that the United States can go it alone. But he notes that collaborations at CERN and in China are also developing plans for electron–ion colliders and that the three groups are already exchanging ideas.

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