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News from the Nuclear Science Division at Berkeley Lab
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Nuclear Science Division Newsletter
In this issue:January, 2016

NSD contributes to SNO Nobel Prize

Art McDonaldArt McDonald delivering a colloquium on SNO at LBNL on November 10, 2015.
This year’s Nobel Prize in Physics is awarded to Art McDonald of Queen’s University and Takaaki Kajita of the University of Tokyo for their contributions to the demonstration of neutrino oscillation in the Sudbury Neutrino Observatory (SNO) and Super-Kamiokande experiments.  Nuclear Science Division played important roles in the SNO experiment.

In the summer of 1984 Herb Chen of UC Irvine presented a paper at a conference in Lead, South Dakota, in which he concluded that using heavy water as solar-neutrino target would resolve the long-standing “Solar Neutrino Problem” even if neutrinos oscillate.  In March 1989, a group from NSD, led by Rick Norman, joined the SNO experiment, which turned this idea into reality. 

Kevin Lesko (then at NSD) and the Engineering Division led the design and construction of the geodesic frame that held nearly 10,000 8-inch photomultiplier tubes for detecting flashes of light from neutrino interactions in the target.  It was an engineering and technical tour de force to construct this 18-m diameter structure in a cleanroom 6800 feet underground in Sudbury, Canada.

Art McDonaldLocal SNO members celebrated after the colloquium. L-R: Christine Chen (Herb Chen's daughter), Catherine Li Chen (Herb Chen's widow), Janet McDonald, and her husband Art McDonald.
NSD played leading roles in other areas of the SNO project as well, including cleanliness control design and implementation at the underground laboratory, calibration source construction and deployment, radioactive background assays of materials at the Low Background Facility, and physics analysis.  Alan Poon served as a physics analysis coordinator for the collaboration.

On November 10, Art McDonald gave a special colloquium on SNO at LBNL’s main auditorium.  In the talk, he highlighted NSD’s contributions to this epochal experiment.  The video recording of the talk can be found at:

https://drive.google.com/a/lbl.gov/file/d/0B3l9ObEzIj-9d3ZWRUdpS1dSMnM/view?ts=566f5218

A more detailed account of NSD’s contributions to the SNO experiment can be found at: http://newscenter.lbl.gov/2015/10/14/2015-nobel-prize-in-physics-has-berkeley-lab-roots

RNC Group Shines at Quark Matter 2015

Art McDonald The flow of D-mesons in Au+Au collisions.
The Quark Matter 2015 conference was held in Kobe, Japan, on September 27 to October 3, 2015. Quark Matter conference is the major conference in the field of ultra-relativistic nuclear collisions, with about 700 attendees from around the world. The NSD Theory Group and the Relativistic Nuclear Collisions Program (RNC) were strongly represented, with a total of 14 plenary and parallel talks. NSD highlights included first results from the STAR Heavy Flavor Tracker and a new measurement of jets in Au+Au collisions at RHC:
  • Plenary: STAR Overview (Mustafa Mustafa, RNC postdoc), Light systems at the LHC (Constantin Loizides), and EIC (Ernst Sichtermann);
  • Theory Parallel: D-meson correlations (Shanshan Cao) and jet quenching (Wei Chen and Tan Luo, PhD students);
  • The spectrum of jets recoiling from a high momentum trigger in Au+Au collisions.
    Experiment parallel: first results from the STAR HFT on D-meson yield suppression and elliptic flow (Mike Lomnitz and Guannan Xie, Ph.D. students),  HFT performance and future STAR upgrades (Giacomo Contin), RHIC Beam Energy Scan (Jochen Thäder, postdoc), and jets in Au+Au collisions (Peter Jacobs);
  • Poster: charm with the HFT (Long Ma, PhD student);
  • Student Day Lectures (Nu Xu, Barbara Jacak).
The figures show two highlights from the RNC presentations. The top figure shows the first STAR measurement of D-meson elliptic flow (v2) with the Heavy Flavor Tracker, compared to model calculations. The bottom figure shows the STAR measurement of reconstructed jets recoiling from a high momentum single hadron trigger in central and peripheral Au+Au collisions, with the arrow indicating the first direct measurement of partonic energy loss in the QGP at RHIC.

The First Majorana Demonstrator Module is Commissioned

The first module being inserted into its lead and copper shield.
One of two electronics boxes used in the first MJD module. The signal processing electronics were designed and built by NSD and the Engineering Division
In late May, 2015, the first of two low-radioactive-background cryostat modules was moved into Majorana Demonstrator’s (MJD) lead and copper shield in the underground laboratory at the 4850’ level at Sanford Underground Research Facility in Lead, South Dakota.  This marked the beginning of a four-month commissioning data run for MJD, a project to search for lepton-number-violating neutrinoless double-beta decays in 76Ge. In this first commissioning run, two components, an inner layer of shielding composed of ultra-low background electroformed copper and a low-activity vacuum seal for the vacuum cryostat, were being prepared and were not installed.

NSD personnel led MJD’s “detector task,” which includes the acquisition of the 76Ge-enriched germanium detectors, design and implementation of signal readout electronics, and the assembly of detector strings, which consist of four to five detectors each.  A significant milestone was reached in June when the detector vendor AMETEK-ORTEC delivered the last enriched detector to the project.   The total mass of the delivered enriched detectors was 29.7 kg.  The first cryostat module contains seven detector strings, with 16.8 kg of enriched detectors and 5.6 kg of natural detectors.

In the commissioning run, the production version of the signal readout electronics was installed.  Over 600 kg-days of data were taken during this commissioning run.  The collaboration is now actively studying the data and preparing for the beginning of production data taking.

NSD Collects Awards

The ratio of measured anti-neutrino flux from reactor experiments to the expected flux assuming no neutrino oscillations. The shaded region indicates the range of flux ratios predicted by the large mixing angle (LMA) solution. The dashed curve is the best LMA fit from solar neutrinos.
This was a busy awards season for NSD, with staffers garnering a number of key prizes.

Breakthrough Prize.  On November 8, 2015, the Sudbury Neutrino Observatory (SNO) and KamLAND experiments were among five neutrino experiments awarded the 2016 Breakthrough Prize in Fundamental Physics for their roles in the discovery and exploration of neutrino oscillations. The Breakthrough Prizes honor advances in Fundamental Physics, Life Sciences, and Mathematics, and are the awards are the richest in their fields. The 2016 neutrino physicists shared a total of $3 million.

Scientists from Nuclear Science Division and personnel from the Engineering and Physics divisions played leading roles in these two experiments.  The roles NSD played in SNO are described elsewhere in this newsletter.  The late Stuart Freedman (UC Berkeley and NSD) led the US effort in KamLAND.  The Daya Bay experiment, led by our Lab’s Physics Division, was also named as one of the five winning experiments.

In 2001, SNO released the first measurement on the flux of electron-type neutrinos from the Sun.  In 2002, the total flux of all three active neutrino types was determined, and demonstrated conclusively in one experiment that neutrinos from the sun undergo flavor transformation.  The results both validated the solar model prediction of neutrino flux and solved the four-decade-old solar neutrino problem.

Later that year, KamLAND, studied antineutrinos from over 50 commercial nuclear power reactors in Japan and observed a clear deficit in the flux of reactor antineutrinos.  This observation confirmed the prediction of the “Large Mixing Angle” (LMA) solution that could explain the solar neutrino flavor transformation under the neutrino oscillation hypothesis. 

A list of NSD and other LBNL personnel who share this year’s Breakthrough Prize can be found in: http://newscenter.lbl.gov/2015/11/09/2016-breakthrough-prize-in-physics.

Bonner Prize.  I.-Yang Lee won the American Physical Society’s 2016 Tom W. Bonner prize in Nuclear Physics.  I.-Yang was cited for “For seminal contributions to the field of nuclear structure through the development of advanced gamma-ray detectors as realized in the Gammasphere device, and for pioneering work on gamma-ray energy tracking detectors demonstrated by the Gamma-ray Energy Tracking Array (GRETINA).”  These gamma-ray tracking detectors have revolutionized the field of precision nuclear spectroscopy.  One measure of the success of GRETINA was the recent decision by the Department of Energy, to award CD-0 status to the next generation gamma-ray tracking array, GRETA.  GRETA builds on GRETINA, and will feature near 4π coverage.  GRETA will be one of the key instruments at the DOE’s Facility for Rare Isotope Beams (FRIB) which is now under construction at Michigan State University.

The three APS Fellowship recipients. From left, Rod Clark, Kai Vetter and Lee Bernstein.
APS Fellowships. Three NSD staffers were named APS Fellows in 2015: Lee Bernstein, Rod Clark and Kai Vetter.  Lee Bernstein was honored  “for work developing novel methods of determining neutron-nucleus cross sections via high-resolution γ-ray spectroscopy, the early development of surrogate ratio method, and the study of nuclear processes in high energy density plasmas at NIF.” Rod Clark was recognized “for contributions to our understanding of superdeformation, decisive measurements providing firm evidence of the shears mechanism in atomic nuclei, and recent studies of the structure of isomeric states in heavy elements.” Kai Vetter received his award “for pioneering contributions to fundamental radiation detection techniques, particularly gamma-ray imaging, and important societal applications.”
STAR Event Plane Detector Prototype Moves to Brookhaven

The prototype EPD sector. Four of the twentyfour optically separated tiles are illuminated.
RNC students Sierra Garrett andJinlong Zhang wrapping a part of the prototype, before shipment to BNL.
The prototype STAR event plane detector (EPD) has been sent to Brookhaven National Laboratory, for installation in STAR before the upcoming 2016 run.   The event plane detector will be used to more accurately determine the event plane in heavy ion collisions by observing particles produced at far forward rapidities.  By using these far-forward particles short-range (in rapidity) correlations are avoided with particles seen in the central detector.   The EPD should be complete in time for the Beam Energy Scan phase II, which is anticipated in 2019-2020.  

The complete EPD system will comprise 2 detectors, covering positive and negative rapidity.  Each detector will consist of 24 sectors, each covering 15 degrees in azimuth.  The prototype EPD consists of a single sector. The sensors are based on 1 cm thick scintillators with embedded wave length shifting (WLS) fibers. The fibers have 1 mm diameter and are mainly glued into σ-shaped groves. The WLS fibers are coupled to clear fibers via self designed 3D printed optical connectors. The prototype sector has 24 optically separated tiles.  Four of them are illuminated in the top photo.   The EPD prototype uses the latest generation of Silicon PhotoMultipliers (SiPM) from Hamamatsu with an active area of 1.3*1.3 mm2 and 50 μm pitch size. The SiPMs convert the light produced by the particles in the scintillators into electrical signals. The clear fibers are connected to the SiPMs via 3D printed connectors. The detector is covered into a layer of aluminized mylar and a second layer of black paper to guarantee light tightness.

The EPD represents the work of a number of RNC personnel, including Sierra Garrett, Michael Lomnitz, Bandon McKinzie, Alexander Schmah and Jinlong Zhang.
 
Newsletter Notes
Please send any comments, including story suggestions to Spencer Klein at srklein@lbl.gov.

Previous issues of the newsletter are available here.

Newsletter layout of current and previous issues by Sandra Ritterbusch.
Copyright © 2016 NSD, Berkeley Lab, All rights reserved.


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