January/February 2006

Thomas Jefferson National Accelerator Facility • A DEPARTMENT OF ENERGY FACILITY

Accelerator Division AD Newsletter goes electronic; this is named AAAS Fellow last paper issue

he On Target newsletter is going ing science, safety, technology transfer, New Users Group Chair Tcompletely electronic. This is the and significant events and awards. Many introduces himself; discusses last paper issue of the newsletter. The of the items currently found in the Briefs funding, JLab research impact first issue of the e-OnTarget will be post- section at the back of the newsletter ed on JLab’s web page before the end of will migrate to the intranet “Insider” on nuclear physics February. page or the “We Hear That” page. The Eliminating the paper version of the e-OnTarget will be available in a print- newsletter is just one of many cost-cut- friendly mode for individuals who prefer ting moves currently underway across to read a print version of the newsletter. Physicist Kim Egiyan, the Lab. “No more printing or postage Individuals currently receiving the recipient of Armenian State Award, expenses associated with the newsletter,” newsletter through the postal system, shares life, career highlights notes Linda Ware, Public Affairs manag- who wish to receive email announce- er. “In addition, going electronic allows ments regarding posting of the latest us to produce an issue every two weeks, electronic issue, may email magaldi@ enabling us to report on more topics and jlab.org to be added to the email notifi- Young researchers write in a more timely manner.” cation list. about their scientific research: The newsletter will consist of short All staff and users will be emailed X. Zheng examines spin identity; feature stories and news items highlight- the e-version as it becomes available. K. Slifer studies how spin arises in the nucleon

Pentaquark 2005: Update on status of search for enigmatic particle

By mid-February nearly all work groups had moved into the new CEBAF Center addition (Wing F). The few remaining moves are scheduled to take place before the end of February. Trailer City removal started during the week of Feb. 12. wapan Chattopadhyay, rewarding task of mentoring scientists SJLab’s Associate Director for worldwide,” Chattopadhyay said. AAAS Accelerators, has been awarded the Founded in 1848, AAAS repre- distinction of Fellow by the American sents the world’s largest federation of Association for the Advancement of scientists and works to advance sci- announces Science (AAAS). The award will be ence for human well being through its presented at the 2006 AAAS Annual projects, programs, and publications. Meeting in St. Louis, Mo., on Feb. 18. With more than 138,000 members and 2005 Fellows The honor of being named a 275 affiliated societies, AAAS con- Fellow recognizes individual AAAS ducts many programs in the areas of members for their “efforts toward science policy, science education, and advancing science or fostering applica- international scientific cooperation. tions that are deemed scientifically or AAAS publishes the prestigious peer- Accelerator Division socially distinguished.” For the year reviewed journal Science. The tradi- 2005, 376 members were elevated to tion of naming AAAS Fellows began AD among the rank of Fellow. in 1874. Chattopadhyay was cited for his Swapan Chattopadhyay received newly named “fundamental contributions to accel- his Ph.D. in Physics from the Fellows erator science, including phase-space University of California at Berkeley in cooling, innovative collider designs, 1982. Following a two-year associa- and pioneering femto-sources and tion as Scientific Attaché at CERN for mentoring accelerator scientists (1982-1984), he returned to Berkeley at facilities worldwide, especially in National Lab in 1984, where he made developing countries.” In his posi- contributions to the Advanced Light tion, he is responsible for all aspects Source from its design to commis- of Jefferson Lab’s accelerator and sioning (1984-1992) and was the Free-Electron Laser (FEL) programs, Founder/Director (1992) of the Center including research and development, for Beam Physics until his move to and operations, maintenance and Jefferson Lab in 2001. upgrades of the Continuous Electron He has contributed to the devel- Beam Accelerator Facility and the opment of accelerators in Europe, Free-Electron Laser. Chattopadhyay India, South Korea, Japan, Taiwan, leads a team of more than 350 in People’s Republic of China and North research of the physics of particles America. He established the first col- and light beams, forefront electronics, laboration between Berkeley Lab and superconductivity, surface science, Jefferson Lab on the development of cryogenics, and computer process con- FELs based on the superconducting trol applications. radiofrequency technology. Since “What an honor to be recognized 2002, he has served on the Governor’s Swapan Chattopadhyay by the AAAS for the development of Biotechnology Advisory Board of the research tools for the world and the Commonwealth of Virginia.

2 ON TARGET • Jan./Feb. 2006 Dear Colleagues, tion and that from recoil polar- As we begin a new year, I’d like ization; to take this opportunity to highlight -- a study of polarization transfer the world-class scientific research in Compton scattering off the conducted at Jefferson Lab during proton which established that 2005. JLab users, along with our own this reaction directly probes the experimentalists have been working quark carrying the spin of the to increase our understanding of the proton; nucleus of the atom. The past year has -- a theoretical calculation of the seen the successful completion of a spin-dependent structure func- number of critical experiments and the tions of protons and neutrons, publication of several important peer- including their modification reviewed papers as well as articles by a nuclear medium — a key in publications such as the CERN piece of the 12 GeV science Courier, Nature and Physics World. program; Among the experimental runs, the -- and an experiment investigating production run of the Hall A Proton the transition from the nucleon- Parity Experiment (HAPPEX II) will meson to the quark-gluon yield the world’s most precise data on description of the strong inter- the distribution of charge and current action in deuteron photodisinte- associated with strange quarks in the gration studies. proton; the Barely Off-Shell Nucleon Additionally, the exceptional pen- Structure (BONuS) experiment in Hall taquark data taken here with outstand- B is the first step in discovering how ing data quality and an order of mag- Christoph Leemann the proton’s momentum is distrib- nitude better statistics has eliminated Jefferson Lab Director uted among its quarks; and the High several pentaquark candidates. Resolution Kaon Spectrometer (HKS) There have also been many excel- experiment in Hall C, with strong lent presentations of Jefferson Lab- financial support from Japan, dramati- based physics — in talks, papers and cally extends our capacity to study posters presented at APS, PANIC, Pursuing strangeness in nuclei. The first experi- and other conferences. The complete ment using CEBAF began running description of generalized parton world-class in November 1995 in Hall C; by the distributions (GPDs) — a theory end of 2005, data collection had been developed by a very small group of science, safely completed on a total of 121 physics theorists, including JLab’s Anatoly experiments, and partial data collec- Radyushkin, was published in Physics tion had taken place on another eight Reports. Another major review in experiments. Physics Reports, involving JLab staff Groundbreaking papers published Rolf Ent, Cynthia Keppel and Wally in Physical Review Letters by JLab Melnitchouk, summarized our cur- scientists and users include: rent knowledge of duality, a major -- two papers regarding strange experimental program over the last few quarks in the proton — the years. This type of visibility for our exciting G-Zero result, which scientific results is vital as it increases From showed as a function of the profile of the Laboratory and its momentum transfer how work, and establishes us as a world strange quarks contribute to the leader in the field. the proton’s electric and magnetic In the coming year many more fields, and a lattice QCD cal- important studies are on the schedule, culation which established a including a measurement of the elec- Director remarkably precise theoretical tromagnetic form factor of the neutron result for the strange quark’s in Hall A, a search for new nucleon contribution to the proton’s resonances and other experiments with magnetic moment; the new Frozen Spin Target (FROST) -- a two-photon exchange correc- in Hall B’s CLAS, and the backward tion for elastic electron-proton angle run of the G-Zero experiment in scattering which clarified the Hall C. observed difference between In addition to nuclear physics the electric form factor extract- research, JLab scientists and engi- ed from a Rosenbluth separa- neers carried out research and devel- Continued on page 14 Jan./Feb. 2006 • ON TARGET 3 In their did my graduate work at Yale work- produce liter-type quantities of He-3, I ing under Vernon Hughes. Vernon something that had never been done was a student of I. I. Rabbi, a luminary before. This work played an important own in atomic physics, and the inventor role in the invention of a new type of of magnetic resonance. While Vernon magnetic resonance imaging (MRI) words eventually expanded into electron of the lungs, which provides unprec- scattering and related physics, he edented resolution. Will Happer and I always retained a fondness for using co-founded a small startup company to techniques borrowed from atomic commercialize the technology. With no physics in his experiments. Even medical school at Princeton, we con- with though I did my thesis at the MIT ducted much of the related research at Bates Accelerator, I received training Duke and UVa. Users Group in both nuclear and atomic physics, I first came to JLab in the mid- and also have a fondness for bringing 1990’s, as the SLAC program was Chair atomic physics techniques to bear on winding down and JLab was first fundamental nuclear physics problems. coming online. Zein-Eddine Meziani Gordon Cates Vernon was also the first person to and I proposed to study neutron spin study the spin structure of the nucleon, structure in the regime where we a subject about which I am passionate could observe the way quarks begin to this day. to assemble themselves into what we After Yale I took a job working as recognize as normal nuclear matter. It a post doc for Will Happer at Princeton. was an exciting time, and it quickly Bill Turchinetz at Bates had pointed out became clear that JLab was going to that Will was the guru of new techniques be a wonderful place to work. By the for spin polarizing certain noble gases, late 1990’s I found myself constantly including helium-3 (He-3). Will, an commuting to both JLab and UVa. I atomic physicist, almost didn’t hire me fell in love with the Charlottesville because he was afraid I would revert area for a variety of reasons including to doing nuclear physics. I told him the gorgeous country side, UVa, and that if I ended up joining the faculty at the easy two-hour drive to JLab. Princeton, I probably would, but that Despite being a full professor at while I was his post-doc, I would do Princeton, in the summer of 2000, what he asked of me. Once I became my wife Laura and I moved to the an assistant professor, I did indeed Charlottesville area (to Gordonsville begin a program in nuclear physics, of all places!) where we live on a but Will and I continued to collaborate 50-acre farm where we raise alpacas for the entire 13 1/2 years I spent at and cashmere goats with our children, Princeton. Gordie and Lynnie. This year I am on Gordon Cates The work for which I was prob- sabbatical at JLab and am renting a ably best known at Princeton, at least house in Hampton where I live dur- until the time I got tenure, were two ing the week. I am the current chair experiments at SLAC that studied the of the JLab Users Group Board of spin structure of the neutron. These Directors, a job that involves, among experiments both used a polarized other things, being an advocate for the He-3 target, and provide what is still users to both JLab management and the most precise data on the neutron the funding agencies. over the kinematic range that we It has been a challenging time for covered. In the process of developing funding issues recently, with lacklus- these targets, however, we learned to ter increases for several years, and a Continued on next page

4 ON TARGET • Jan./Feb. 2006 Continued from previous page whopping eight percent cut recom- remainder of the mass includes exotic mended for nuclear physics in the effects such as quark-antiquark pairs FY 06 federal budget. Such problems popping in and out of the vacuum, a are clearly not lost on our young subject that is being actively investi- physicists. We have seen some very gated by parity-violation experiments. talented people decide to leave the And this is only the beginning. With field recently as they find themselves the 12 GeV Upgrade, the science com- frustrated with the situation and the ing out of JLab will be more excit- implications that funding limitations ing than ever before. In many ways I has on the job front. Losing young believe that our growth in understand- physicists to other fields breaks my ing the nucleon at the beginning of the heart. And even though I feel their 21st century can be compared to the decision is ill motivated in the long growth of our understanding of the run, who can blame them when they atom at the beginning of the 20th cen- run out of patience? tury. JLab is key in making this hap- I cannot help but reflect on some pen. of the factors that led me into nuclear On the political front, things physics. When I was nine or ten, I are starting to turn. The National wrote an essay stating that I wanted Academies report, “Rising Above to be either a scientist or an astronaut. the Gathering Storm”, details how This was a time when the Mercury and the United States is beginning to Gemini programs often dominated the fall behind Europe and Asia in the headlines, and my mom would always physical sciences and engineering. let me stay home from school to watch While a frightening report, it has been a space launch. When I was not much embraced by people like Senator John older, I read a book titled “Atomic Warner who have quoted from it on Energy”. Again the wonders of nuclear the Senate floor while discussing the energy were being touted, and I funding for nuclear physics and JLab. viewed the field of nuclear physics The President’s FY07 budget rep- with considerable awe. All of this pos- resents a significant turn around for itive feedback played an important role which I am cautiously optimistic. The in drawing me into my current work. fact that JLab produces roughly 25% Limited funding, with its restrictions of the nuclear physics Ph.D.’s awarded on jobs, growth, and new opportuni- in the United States is not lost on our ties, can only have a similarly negative lawmakers. JLab is very special. Our effect. students are intimately involved in I remain, however, an extreme building the apparatus with which they optimist. In the nearly 30 years since I perform their respective thesis experi- graduated college, our view of nuclear ments. matter has blossomed in a manner that JLab is an essential component of would have been very tough to antici- nuclear physics in the United States, pate. We have now achieved what are and producing discoveries that are giv- essentially high-resolution pictures ing us a new view of nuclear matter. of the charge and magnetic currents Innovation and discovery of the sort inside the nucleon. We have estab- one finds at JLab will be a vital engine lished that more than 95% of the mass behind the technological and economic of protons and neutrons are something leadership that I believe will come other than what we might naively call from the United States over the com- the mass of the valence quarks. The ing century.

Jan./Feb. 2006 • ON TARGET 5 as told to Judi Tull

t is interesting to be given the Correlations (SRC). This problem fully Ichance to look back over my life as captured me, and I started to study it. I approach my 70th birthday, my 50th In the late ’60s and first half of year in physics and my 20th year in the ’70s, I organized a small group of collaboration with JLab. young physicists and proposed these In their I grew up in an Armenian village studies at YerPI using our electron that was what you would call a resort, accelerator with energy up to 6 GeV. a place where wealthy people from We got interesting data; however, these own words big cities came to rest and relax. I was results did not give us direct informa- always a child of nature; I loved to tion on SRCs. The beam parameters of be outside in the summer — day and our accelerator were too poor for that. night. So I started my search to find other sci- I am the fifth child in my fam- entific centers with better beam param- with ily. My parents were working people: eters. father was a carpenter and mother I looked all over the world. Then physicist worked on a collective farm. My three in 1979 I heard that an accelerator was brothers and only sister all were very going to be built in the United States, Kim Egiyan good students in high school, and they and by 1984 I started to think that this taught me to read and write when I was lab would be the perfect place for col- young. laboration. When I first proposed the School always came easy for collaboration, I was turned down, partly me. In all of my grades, I was first in because the then-Soviet Union already the class. However, when I became had a big team at Fermilab. But two a student of physics at Yerevan State years later I was granted a trip here to University in 1952, I was shocked to attend a summer workshop on the future discover that everyone there had been of CEBAF’s accelerator and physics first in their high school classes! The programs. I returned each summer, and competition was very, very hard, but in 1989, the PAC (Program Advisory (maybe because of that) my studies Committee) accepted our experiments. were very successful. I started working We drew up the MOU (Memorandum at the Yerevan Physics Institute (YerPI) of Understanding) between CEBAF and a year before my graduation, and I have the nuclear physics community of the been affiliated with it ever since. My Soviet Union. I believe it was CEBAF’s current title is Leading Scientist and first MOU with a foreign country, and I head of the electro-nuclear program. was the spokesman on the Soviet side. My career started in the late- After the collapse of the Soviet Union, 50s with the physics of cosmic rays. the collaboration split in to three sepa- However, during that time I read about rate collaborations and from that point R. Hofstadter’s experiments at SLAC, to this day our Yerevan-CEBAF col- studying the structure and proper- laboration has continued; and I am the ties of nucleons and nuclei with high spokesman for this collaboration. (at that time) energy electrons. I was In the ’90s we were highly involved shocked by the beauty and important in developing the CEBAF physics pro- results of these experiments. In particu- gram and in constructing experimental lar, it was shown that nuclei could be equipment in all three halls. We have described very well as a simple system three groups of five people — one of independent nucleons (neutrons group in each hall — and we are active and protons). But the question arises, partners in the experiments and work how can nuclei exist as a dilute bound on hardware. All three groups are cur- system of nucleons, when long-range rently analyzing and publishing interest- attraction between nucleons would ing results. As for me, and my desire lead to their collapse. Therefore the to better understand SRCs, we finally short-range repulsion should exist obtained direct information about them also. This repulsion should lead to the here, at CEBAF. We “saw” them and formation of a few (2, 3) nucleons in measured strengths (probabilities) of very close configurations, which in the 2 and 3 — nucleon SRCs in various ’60s we referred to as exotic states. nuclei. Experts in our field are discuss- Currently they are called Short-Range ing these results widely. Continued on next page

6 ON TARGET • Jan./Feb. 2006 Kim Egiyan earns Anania Shirakatsi Medal

Continued from previous page I believe that one of the great- at Saints Constantine and Helen est gifts I’ve given to science and the Greek Orthodox Church to hear a world of physics is the young people liturgy given by Father Hovsep, a priest I have brought along through these from St. James Armenian Church in Kim Egiyan poses for a photo in his years. Many of them have had signifi- Richmond. I hope one day the commu- JLab office. The Anania Shirakatsi cant success and I am very proud of nity will have its own church. Medal (pictured) presented to Egiyan them. Two of them work here; four I am here with my family. I have is an Armenian State Award recogniz- others are at U.S. universities. I con- two sons; they are both physicists and ing scientists for notable activities in tinue working with young people. I am are both in the United States. Hovanes economics, engineering, natural sci- currently supervising three “senior” graduated from William and Mary (he ence and technology, as well as for physicists who will defend their Ph.D. was the first young Armenian to obtain significant inventions and discoveries. work in the next 2-3 years and three his Ph.D. in high energy physics from The medal is named after Armenian graduate students. Last year one of my scholar, mathematician and geog- a U.S. university) and did his post-doc rapher Anania Shirakatsi (610-685), students defended his Ph.D. based on work at CEBAF. My other son, Gagik, experimental results obtained in Hall A. whose most famous works are is a graduate student in Detroit. I have Geography Guide, and Cosmography. Sometimes I feel a main purpose of my a granddaughter, Ofelia, the sweetest life is to be part of a channel for young (Information from the Republic of person in the world, who was born in Armenia Library website www.presi- people to grow in science. the U.S. and is a U.S. citizen (may be dent.am/library/eng/) I think I have had much suc- a future president of this country). My cess in my scientific and educational wife Elionora, a physician, is here and career and this was recognized in always is with me. We are part of our 2004 when I received the Medal of community — trying to keep our nation- Anania Shirakatsi from the President of al traditions and customs. We have great Armenia, the highest award in science help and support from all levels of JLab in my country. I am one of only 142 management, from physicists, engineers people to receive it. I am very proud and technicians. We have made many of this, not only because it came from good friends among individuals and the President, but because my home families within the Lab and the commu- Institute made the initial nomination, nity at large. Working conditions at the which means that the people working Lab are ideal, and America is a unique, with me recognize my achievements. sweet country where everyone has an I was likely the first Armenian opportunity to find himself. citizen to visit this area in 1986. No I am very happy to be here. But Armenian families lived around here my heart is in my small, mountainous during the first period of our col- Armenia. I am in the second year of a laboration. Now we have a commu- three-year stay here as a visiting sci- nity named the Tidewater Armenian entist. While I do not know what will Community, a group of about 50 happen when my time is up, one thing is people. The core of this community clear, I will continue to work in physics is made up of physicists at JLab and right up until the last minute. I will not their families. We gather once a month retire, no!

Jan./Feb. 2006 • ON TARGET 7 by Xiaochao Zheng pin is an essential and fascinat- strong forces holding it together. In Sing phenomenon in the physics the early 1980’s people thought that of elementary particles. Ever since the quarks’ spin should contribute a spin was first defined by Goudsmit majority of the proton spin. But in Spin Identity and Uhlenbech in 1925, it has played 1987, the pioneering spin experiment a dramatic role in elementary par- by the European Muon Collaborations ticle physics, sometimes refuting at CERN showed that the sum of the theories and at other times supporting spins carried by the quarks in a proton them. During Experiment E99-117 at add up to only about one-eighth of the Jefferson Lab, an international col- proton’s spin. This “proton spin crisis” Researchers grapple laboration consisting of more than 80 triggered tremendous efforts to further with fascinating physicists from 22 institutions and study the source of spin of protons and led by Jian-Ping Chen (JLab), Zein- neutrons. Now after 20 years of study, phenomenon of Eddine Meziani (Temple Univ.) and we know that the nucleon spin comes Xiaochao Zheng (then a Ph.D. student not only from the spin of quarks, but spinning quarks in at M.I.T.), collected precision data on also from the quarks’ orbital angular the spin of the neutron. Results from momentum, and from the angular the nucleon this experiment provide evidence that momentum of gluons, the particles that our current understanding of spin is hold the quarks together. not totally valid. Therefore, one attractive place In high-school physics lessons, to study the nucleon spin structure is nucleons simply consist of three the valence quark region, where the quarks. A more complete picture nucleon can be viewed as being made includes these three so-called valence of only three valence quarks, while quarks, plus a sea of quark-antiquark other components — gluon, strange- pairs that pop in and out of the vac- ness (s quarks) and other sea quarks uum, and gluons exchanged between — are scarce and the nucleon is rela- quarks. Experiments where both the tively easier to study. In particular, it is electron beams and the target spins expected when a valence quark carries are polarized can provide information a majority of the nucleon energy, it about how quarks’ spins are oriented should have negligible orbital angular inside the target proton or neutron, momentum (OAM) and its spin should helping us to understand the funda- align to the nucleon’s spin. mental structure of matter and the Since the nucleon is primarily made of two flavors of valence quarks, the up (u) and the down (d) quarks, Science benefits society it is necessary to combine informa- Magnetic moment leads to break- tion from both protons and neutrons through in medical imaging to decompose the nucleon spin into The spin of a particle describes different valence quark flavors. Due Xiaochao Zheng its intrinsic angular momentum. It to the lack of precision neutron data, allows the particle to have a mag- the valence quarks’ spin orientations netic moment, and in the pres- have not been explored until recently. ence of a magnetic field it tends Experiment E99-117 collected, for the to orient itself along or opposite to the field direction just like a first time, precision data on valence small magnet. It is this feature quarks’ spin distribution in the neu- that allowed medical physicists tron. to invent magnetic resonance imaging (MRI), a technique that The experiment ran in Hall A from reads the small magnetic signals June 1 to Sept. 29, 2001. In the experi- from either protons inside the ment, a polarized beam of electrons human body or a particular nuclei was sent into a polarized helium-3 being introduced into the body for (He-3) target. This target was used diagnostic purposes. The much higher spatial resolution and sen- because the He-3 nuclei is made of sitivity of this technique provided one neutron and two protons with a breakthrough in medical diag- nostics. Continued on page 14 8 ON TARGET • Jan./Feb. 2006 by Karl Slifer n scattering experiments, the nucleon and also about the individual Determining Imomentum transferred to a nucleon characteristics of the partons. But we target from the incident electron is a don’t know exactly how to join these primary characteristic of the interac- two pictures. JLab is uniquely posi- how spin tion. Large momentum transfer reac- tioned with one foot on the edge of tions probe the fundamental quarks the high momentum transfer region and gluons (collectively known as par- and the other on the edge of the low arises in the tons) that make up the nucleon. energy region. Experiment E94-010 At this high-energy scale, the scat- took advantage of this fact to measure nucleon tering occurs over a very short time the extended Gerasimov-Drell-Hearn and spatial extent within the nucleon. sum rule. “GDH” is one of the only The partons thus have little time to spin-dependent observables that can interact before the incident electron be measured at arbitrary momentum departs. As an analogy, consider a transfer and can also be calculated by high-speed bullet shot through an theorists from first principles. apple: The apple retains its basic shape Even more importantly, it has and characteristics for some short previously been measured at very time after the bullet has passed. This high momentum transfer, and is also is because the reaction has not had being investigated at very low (zero) enough time to propagate throughout momentum transfer by independent the apple. By examining the trajectory experiments. Observing how the of the scattered bullet, an observer GDH sum evolves in the intermediate could learn something about the range will be an important first step innards of the apple, whether it had a in understanding how partons form hard or soft core, for example, but not nucleons, and specifically how the much about the whole apple. nucleon’s spin is formed from the par- In electron scattering, high tons and their interactions. High preci- momentum transfer reactions can be sion neutron data from this experiment treated with a dramatically simplified and complementary proton data from theoretical approach, because the par- Halls B and C have helped to stimu- ton interactions are largely ignored. late a tremendous theoretical response, There is, in fact, a long and impressive resulting in a series of international history of investigation in this kine- conferences dedicated to the GDH sum. matic regime at labs like SLAC and Continued on page 14 Karl Slifer CERN, which has helped to form our current understanding of the nucleon’s structure. Science benefits society In a low momentum transfer reac- tion however, the partons behave col- Technology developed for experiment leads to new type lectively as a nucleon. To continue the of MRI capability earlier analogy, consider a pellet shot from a BB gun with much less energy, The spin exchange optical pump- which simply bounces off the outer ing technology developed for skin. In this case, a clever observer the polarized target has led to could learn something about the global some amazing medical imag- properties of the apple, its mass for ing breakthroughs. Traditional example, but not much about what is MRI (magnetic resonance imag- inside. Likewise, in low momentum ing) techniques detect signals transfer electron scattering, only the from hydrogen, which is found abundantly in human tissue, but gross properties of the nucleon are is absent in the open cavity of seen. The characteristics of the partons the lung. Enterprising collabora- within are not observed. tors realized that helium-3, when At this time, nuclear physicists inhaled, would enable excellent have collected lots of information imaging of human lungs during about the global properties of the MRI, while avoiding the risk due to radiation exposure necessary in other forms of tomography. Jan./Feb. 2006 • ON TARGET 9 by Kandice Carter

hen data hinting at the existence by strong force gluons as two-quark Wof an exotic particle dubbed the mesons or three-quark baryons such as pentaquark was first announced, it set protons and neutrons. However, current the scientific world on fire. Physicists understanding of the theory of Quantum were excited, because the pentaquark Chromodynamics (QCD), which de- could reveal information about how scribes quark-gluon behavior, says it is ordinary matter is glued together; the possible for quarks to show up as a five- Update on science-interested public was intrigued, some in the aptly named pentaquark. because the pentaquark represents an Very few attempts were made to research entirely new form of matter never seen find the pentaquark until recently. In a before — a rearrangement of nature’s 1997 theory paper, Maxim Polyakov, basic building blocks. Dmitri Diakonov and Victor Petrov, But recent experimental and theoret- from the Petersburg Nuclear Physics ical evidence has somewhat dampened Institute in the Russian Federation, pre- the excitement that followed the first dicted the mass of a pentaquark dubbed announcements. Some of the initial data the “Theta-plus.” The theorists predicted that seemed to suggest the reality of that the mass would be confined to a The state the pentaquark have now been revised, relatively narrow range, which would of the and kinematically similar experiments stand out in a graph of data as a nar- with higher statistics have produced null row spike, or peak. What’s more, this pentaquark results. pentaquark was predicted to contain This was the situation faced by pen- three different flavors of quarks: two up taquark researchers who visited JLab quarks, two down quarks and a strange for the Pentaquark 2005 Workshop Oct. anti-quark. The presence of the strange 20-22. Two and a half days of sessions anti-quark should make the particle laid out the current state of pentaquark uniquely identifiable, giving it a proper- research from the theoretical and experi- ty called “strangeness.” Spurred by this mental perspectives. Workshop attend- prediction, experimenters began hunting ees were encouraged by the increas- for the particle. ingly better quality of data and data The first pentaquark sighting was analysis that research in pentaquarks announced by researchers from SPring- has fostered. JLab has led the way in 8, a large synchrotron radiation facility these advances. High quality beam from in Japan, in spring 2003. They found CEBAF and the unique equipment in hints of the particle while mining data the experimental halls have allowed sets taken for other experiments. That researchers here to achieve far better same year, researchers from JLab’s Hall kinematics in pentaquark research than B, the Alikhanov Institute for Theoreti- anywhere else. JLab researchers have cal and Experimental Physics (ITEP) in also developed new statistical tools to the Russian Federation and the ELec- improve data analysis. While it’s un- tron Stretcher and Accelerator (ELSA) clear what the final verdict will be, the in Germany, announced that they, too, work has already proved interesting and might have spotted tantalizing hints of informative. the Theta-plus in data previously taken A Brief History in other experiments. Even better, these experiments quoted high sigma values The smallest building blocks of — values obtained through statistical ordinary matter consist of quarks and calculations that quantify how likely the associated gluons that “glue” quarks it is that the result is accurate. These together. There are six flavors of quarks: announcements sparked researchers’ up, down, strange, charm, bottom and imaginations. top. Each flavor of quark also has an opposite — the anti-quarks (up anti- However, they all suffered from rel- quark, down anti-quark, etc…). Most atively low statistics (a very small num- quarks come in groups of two or three, ber of potential pentaquarks amongst and are routinely found bound together a large number of other particles that could confuse identification). Further, 10 ON TARGET • Jan./Feb. 2006 Continued on next page Continued from previous page the pentaquark masses pinpointed taquarks repeating JLab’s first pen- by these experiments didn’t match taquark search with a factor of 10 higher — some seemed to center at 1520 statistics also came up negative. The MeV, while others were closer to 1550 researchers think a statistical fluctua- MeV. To clear up the matter, dedicated tion combined with a poor early under- pentaquark searches with high-statistics standing of background reactions in the measurements and additional theoreti- experiment added up to a ghost signal cal predictions were needed. masquerading as a potential pentaquark. A Matter of Statistics Volker Burkert, Hall B Leader, credits the second run for providing a better A short time later, the first high- understanding of the background and statistics searches for the pentaquark eliminating the ghost. began reporting results. None of these efforts revealed a pentaquark in the re- Andrew Sandorfi said in his pre- gion where one was expected, and none sentation at Pentaquark 2005, “So far, of the higher-statistics, higher-precision there are few peaks, but lots of statis- searches for pentaquark partners, such tics.” And more statistics are coming as a Hall A experiment aimed at finding in every day. Marco Battaglieri, a staff the Theta-plus-plus, came back posi- scientist at Italy’s INFN in Genova, a tive. JLab CLAS collaborator, and a member of the team that repeated the SAPHIR Theorists also began weighing in measurement and analysis, reported on the subject, performing new calcula- another null pentaquark result in a dif- tions for pentaquark production mecha- ferent reaction channel at Pentaquark nisms and probabilities. Some theorists 2005. even employed lattice QCD calcula- tions. However, few found possible Valery Kubarovsky, a researcher pentaquark states that could be easily affiliated with Rensselaer Polytechnic identified with current experimental Institute and JLab’s CLAS collabora- capabilities. What’s more, authors of tion, followed up with another null some of the original pentaquark papers result for an ultra-high statistics search began refining their sigma values. for the doubly charged Theta-plus-plus. Careful reevaluations of the data and The STAR collaboration at Brookhaven statistical methods led them to choose National Lab’s Relativistic Heavy Ion more conservative methods of calcula- Collider may have seen such a state. tion. The result was a smaller margin of Blind Alleys confidence in the original results. Still, Marston Bates, a zoologist whose the results stood untested by dedicated research on mosquitoes led to an under- measurements. standing of how yellow fever spreads, Then, at the American Physical once remarked, “Research is the process Society April 2005 meeting, Raffa- of going up alleys to see if they are ella De Vita, a staff scientist at Italy’s blind.” Istituto Nazionale di Fisica Nucleare While negative results in the hunt (INFN) in Genova and a JLab CLAS for the pentaquark may seem discourag- collaborator, presented the results of a ing, they’re still a solid step in the right high-precision measurement by Hall direction. Without these efforts, scien- B researchers of the same reaction that tists would never know if these particles the SAPHIR collaboration at ELSA in existed. This is especially important Germany announced had produced a since ruling out the presence of possible pentaquark. The JLab team, whose data subatomic particles is just as important contained two orders of magnitude bet- as finding new ones. Whether positive ter statistics, found no evidence of the or null, each result brings us closer to an pentaquark. understanding of the stuff the universe Two months later, another dedi- is made of. cated, high-precision search for pen-

Jan./Feb. 2006 • ON TARGET 11 ccelerator Operator Scott H. My- mug, and would not start his day with- Aers, 33, passed away at home sur- out it. One day his trusted mug broke rounded by his family on Oct. 1, 2005, and he almost lost his will to drink after a long and courageous battle with coffee. However, within a week there In brain cancer. Born in Buffalo, N.Y., he was a brand new Marvin the Martian had been a Peninsula resident for the mug ready for the task and balance Memoriam past five years and had been a JLab was restored to the Force! (Anything accelerator operator for approximately Star Wars, new or old, was a source of 5 years. enthusiasm for him.)” He earned his master’s degree in “Scott was a huge Buffalo Bills nuclear physics in 1998 from Florida fan and always knew the scores for JLab mourns State University and was a member not only his team but the scores & of Warwick United Church of Christ, stats for the teams that his fellow crew loss of Newport News. Myers is survived by members liked as well. Sometimes this Scott Myers his parents, Huston and Barbara Myers would be to his delight when a certain of Rotonda West, Fla.; sister, KelliAnn Miami Dolphin’s fan would show up Winkowski and her husband, Ray- knowing the team didn’t quite make mond, of York, Pa.; companion, Daniel the cut that weekend. (Scott hated Cuevas of Newport News; and many the Dolphins even though, or perhaps aunts, uncles, cousins and friends. Pas- because, he was an FSU graduate.)” tor Michael O’Christiansen conducted “He loved listening to music and the funeral service celebrating Scott’s one of his favorite groups was De- life Oct. 4 at the Warwick United peche Mode,” Fanning adds. “Scott Church of Christ. Interment followed liked to check up on his old campus. at Peninsula Memorial Park. When there was a quiet moment on Scott’s fellow accelerator operators shift he would quickly take a look at hold many special memories of their the campus via Florida State Univer- friend. “Scott was a wonderful asset sity’s building cameras to see students to the operations group and Jefferson rushing to and from class or to check Lab,” says Mike Epps, Deputy Group on the status of a favored faculty web- Leader for Operations. “He was a site. It could be 3 a.m. and he would friend and brother who is truly missed. grab a quick peek of his Alma Mater In addition to being a senior accelerator via the campus cameras. ‘Good memo- operator and a crew-chief-in-training, ries’ he would say. That and an occa- Scott Myers Scott worked on several different proj- sional ‘Oh-My-God!’ that could startle ects outside the control room. These a quiet crew only to find out ‘They left included writing documentation related the water fountain on in the quad!’ at to practical ARM (assigned radiation FSU.” monitor) survey factors, developing “Scott’s friendly demeanor is the and maintaining the video digitizer sys- part of him we all miss. He would tem, and providing diagnostic develop- always strike up a conversation with ment — in particular, developing the the crews or include himself in a topic linear CCD array project.” of debate. But, no matter how hot the “Scott looked forward to coming debate may have gotten he would let it to work and always came in wearing a slide and be the same old Scott before smile, even when he knew he was fac- the next meeting. That is if you didn’t ing an uncertain future,” recalls Harry take the [Buffalo] Bill’s name in vain,” Fanning, Crew Chief. “Coffee was an Fanning remembers with a smile. important part of that day and he was “We all, and especially our Ma- always willing to throw on a fresh pot. chine Control Center and Operations His favorite coffee cup was his trusty crews, will miss Scott Myers and his Marvin the Martian (a Warner Bros talents dearly,” says Swapan Chatto- cartoon character) mug. He loved that padhyay, Accelerator Division Associ- ate Director.

12 ON TARGET • Jan./Feb. 2006 ongtime Jefferson Lab Occupa- teer? Her husband Edward.” Ltional Medicine Nurse Melissa “Melissa regularly volunteered T. Holloway, 52, passed away Oct. 3, to be the stand-by nurse for many of 2005. Melissa and her husband Edward the Lab’s special events such as open resided in Poquoson. She joined JLab’s houses and run-a-rounds. She just liked staff in 1990 and handled the medical people, and she liked being there when training programs, including CPR/ help was needed. She was a good lis- AED (cardiopulmonary resuscitation/ tener, very giving, and generous in her automated external defibrillator) train- compassion for others’ medical prob- ing and provided support to the range lems. Her ‘fingerprints’ are all over of activities managed by Occupational Jefferson Lab, and I miss her greatly.” In Medicine. Melissa graduated from Poquo- “I worked with Melissa for more son High School in 1971 and earned Memoriam than 15 years and I miss her very her degree as a registered nurse from much,” comments Dr. Smitty Chandler, Thomas Nelson Community College JLab’s Occupational Medicine Direc- in 1979. Before coming to Jefferson tor. “She was an unusually kind person. Lab, she worked at Riverside Regional I never heard her make a cruel or Hospital, Williamsburg Community JLab mourns inconsiderate comment about anyone. Hospital and Mary Immaculate Hospi- She was a ‘people person’ through and tal. Holloway was a certified instruc- loss of through. Melissa cared about others in tor for Basic Trauma Life Support, Melissa Holloway an absolutely sincere manner. She had Advanced Cardiac Life Support and tremendous empathy for others, which Cardio Pulmonary Resuscitation. She is a primary reason why she was such was an Emergency Medical Cardiac an excellent nurse. She derived great Technician for the State of Virginia joy from her family.” and a member of the Poquoson Rescue “Apart from her occupational- Squad, serving as captain for five years health nurse role we at the Lab knew and as a representative on the Pen- so well, Melissa had a passion for insula Emergency Medical Services emergency medical services,” adds Council. John Kelly, JLab Emergency Manager. One line in her obituary read: “I suspect she was known to virtually “Melissa gave so much to so many everyone in the state who has certifica- people while serving in the medi- tion as an instructor in the field. At one cal profession … her kindness will time or another, they probably were long be remembered.” The numerous taught by her.” remembrances and eulogies posted on “She made many useful contribu- the Daily Press Obituary web site by tions to JLab’s emergency planning family, friends and co-workers recall- Melissa Holloway and the conduct of our drills and ing her passion, strength, kindness, and exercises. Her talents included a flair loving and giving nature are a testa- for moulage — applying a realistic ment to that statement. looking, simulated injury to a ‘victim’ Surviving Melissa is her husband to heighten realism and help medical of 34 years, Edward Farrell Holloway personnel see what they are treat- Sr.; son, Edward Farrell Holloway Jr. ing during a drill,” Kelly recalls. “It and wife, Brook, of Newport News; takes time and precision to make an one grandson, Brian Devin Lapp, and injury look real. I recall an emergency one granddaughter, her namesake Vic- exercise years ago that was based on a toria Melissa Holloway; one brother, simulated boiler-room explosion and Benny Topping and wife, Irina, of building fire in the VARC. Melissa Yorktown; one sister, Carolyn Kurtz spent hours moulaging a volunteer who and close friend, Steve Devan, of Yor- truly looked like an authentic trauma ktown; her father-in-law, Russell Hol- victim. The Newport News emergency loway of Poquoson; one sister-in-law, responders were impressed, to say the Regina Holloway McVaugh of York- least. And who was the patient volun- town; and many nieces and nephews.

Jan./Feb. 2006 • ON TARGET 13 Spin Identity: Spinning quarks in the nucleon... Continued from page 8 their spins anti-aligned with each other, When we combined the experi- predictions from relativistic constituent hence most of the helium-3 spin comes ment’s neutron results with previous quark models, which takes into account from the neutron. Electrons scattered data on the proton, we found that the quark OAM through relativistic from the target were detected in Hall while the spin of the valence up quark effects, agrees well with the new data. A’s two High Resolution Spectrometers is aligned parallel to the proton spin, Extensions of this measurement are (HRS). The nucleon spin asymmetry this is not true for the valence down being planned as one of the “flagship” was formed by comparing the counts of quark. This new result disagrees with experiments for the upgraded JLab. The scattered electrons for opposite electron our previous expectations and indi- doubled beam energy (12 GeV) will beam helicity states and then corrected cates that valence quarks’ OAM is not allow a test of our understanding of the for the helium-3 nuclear effects. negligible for the kinematic region nucleon spin at a cleaner valence and explored at JLab. On the other hand, more energetic region. Determining how spin arises in the nucleon... Continued from page 9 Experiment E94-010 (spokesmen energy of this experiment, where QCD- stable within a nucleus such as helium. G. Cates, J.P. Chen and Z.-E. Meziani) based calculations are available, our Helium-3 was chosen because it con- ran during the last three months of data is at odds with the expectation sists of two protons and a single neu- 1998 in Hall A and measured the polar- from theory. This has presented a sig- tron. When polarized, the protons align ized spin structure functions of the nificant challenge to the theorists, and themselves in such a way that their neutron. This international collabora- should help to refine our understanding spin-dependent properties nearly can- tion involved more than 100 physicists of the neutron’s spin. From the data, we cel, leaving the single unpaired neutron. from 32 different institutions and led were also able to evaluate the size and The E94-010 target is the highest lumi- to 5 Ph.D.s. We evaluated the extended strength of the quark-gluon interactions. nosity polarized target in the world, and GDH sum as a function of momen- To gain access to the neutron, the by providing a convenient source of tum transfer, and found a smooth but collaboration built the JLab polarized highly polarized neutrons, it has opened dramatic transition from the value helium-3 target. Free neutrons decay up an exciting new avenue of polarized previously measured at high energy. on average in about 15 minutes, but are studies at JLab. Intriguingly, at the lowest measured From the Director... Continued from page 3 opment work with technologies that ucts of 2005. A positron emission mam- its experimental halls, the Free-Electron enable, or are offshoots of, the Lab’s mography (PEM) device designed and Laser and medical imaging that put us nuclear physics program. The Institute developed by the Detector and Imaging at the forefront of nuclear science and for Superconducting Radiofrequency Group imaged breast cancer tumors laser research. Jefferson Lab scientists Science & Technology fabricated and with a sensitivity rivaling that of whole- and users produce incredible science on tested accelerating cavities made from body PET imaging systems, while a regular basis, a fact in which we can single-crystal niobium. This new pro- requiring a shorter imaging time and a all take pride. Continuing the exciting cess could reduce the cost and assembly lower radiation dose. Jefferson Lab has programs in science and technology time of record-breaking accelerator cav- become an incubator for many exciting at the Lab requires not only our dedi- ities, which could be added to existing and potentially beneficial research proj- cation to scientific excellence, but to accelerators to increase capability, such ects with benefits for society including operational excellence as well, particu- as JLab’s 12 GeV Upgrade, or to build defense, improved medical diagnostics, larly in the area of safety. The success new, more powerful accelerators, such industrial and commercial applications, of our programs will mean little if it as the International Linear Collider homeland security, and health and safety. comes at the expense of any one of our (ILC). The successful commissioning of To advance the exchange of sci- colleague’s health, and in a competitive the superconducting linear accelerator entific information, JLab hosted 11 funding environment, the Lab cannot for DOE’s Spallation Neutron Source in large scientific conferences, workshops afford even one mishap. Supporting Oak Ridge, Tennessee — built by JLab and meetings — attended by 1,100 our science programs takes the atten- — marked a major milestone in the participants — during 2005 on topics tion and efforts of all of us and we must large-scale application of SRF technol- ranging from Semi-Inclusive Reactions dedicate ourselves every day to excel- ogy and capabilities. to Energy-Recovering Linacs and the lence in safety performance in order to Jefferson Lab’s Free-Electron Laser Coordinated Theoretical-Experimental ensure that our science and technology achieved 10 kilowatts (at 6 microns) of Project on Quantum Chromodynamics programs remain healthy and produc- infrared laser light and was selected by (CTEQ). tive in the coming year and beyond. R&D Magazine as one of the 100 most Jefferson Lab provides unique technologically significant new prod- research capabilities with CEBAF and

14 ON TARGET • Jan./Feb. 2006 Briefs Goodbye (just outside the northeast corner of the National Air and Space Museum). Milestones Sherri Powers, Sr. Budget Analyst, For more information about Bennett for Oct.-Dec. 2005 Chief Finance Office and his work, visit www.jeffreybennett. Hello Kelly Mannsfeld, Associate Director com/. Also, available for purchase fol- of Admin. Div. lowing the lecture will be autographed Anthony Bavuso, Control System copies of Bennett’s latest children’s Michael McCrea Sr., Machinist, Accel. Computer Scientist, Accelerator book “Max goes to Mars.” Div. Division Then on Tuesday, March 21, Louis Lorelei Carlson, Front Desk Bloomfield, professor of physics at the Receptionist, Administration Div. University of Virginia, will examine Spring Science Series “How Things Work.” He will offer the Willie Durosseau, RadCon/IH Waste kicks off Feb. 21 audience an introduction to the phys- Technician, Enviornment, Health The 2006 Spring Science series ics and science in everyday life; and &Safety Div. kicks off at 7 p.m. on Tuesday, Feb. examine objects from our daily lives, Nina Farrish, Human Resources 21, in the CEBAF Center auditorium focusing on their principles of opera- Consultant, Admin. Div. with astronomer, teacher and author tion, histories, and relationships to one Jeffrey Bennett from the University of another. For additional information Michael Gericke, Hall C Post Doctoral about Bloomfield, visit http://rabi.phys. Fellow, Physics Div. Colorado (Boulder) presenting “The Scale of the Universe.” If you could virginia.edu/HTW/. Jade Johnson, Human Resources hold the Sun in your hand, where The presentations begin at 7 p.m. Assistant, Admin. Div. would we find the planets and other in the CEBAF Center auditorium. The stars? Bennett will take a virtual trip lectures are free and open to anyone Dennis Turner, Accelerator Operator, interested in learning more about sci- Accel. Div. across the universe, in both space and time, which will fascinate and amaze ence; they last about one hour and Michael Sprouse, Mechanical and his audience. include a question and answer period at Controls Inspector/Evaluator, Admin. One of the many projects Bennett the end. For security purposes during Div. has been involved in is “Voyage: A Science Series events, enter at JLab’s 1-to-10 Billion Scale Model Solar main entrance (Onnes Dr.). Everyone Mike Klopf, Terahertz Post Doctoral over 16 is asked to carry a photo ID Fellow, Accel. Div. System” that opened in 2001 on the National Mall in Washington, D.C. and security guards may inspect IDs, bookbags, purses and vehicles.

Reaching out to youth in need; baker’s dozen bikes donated to Toys for Tots! Christiana Grenoble and Larry King, Accel- erator Division, thank everyone at JLab who supported the 2005 Toys for Tots drive. “See- ing the generosity of the people we work with all year long really gets the holidays off to a proper start,” King said. “I’m sure your dona- tions have made the holidays of many fami- lies quite a bit happier this year!” This is the fourth year that staff in the Test Lab collected donations to buy children’s bikes for the Toys for Tots drive; and each year the outpouring has gotten bigger. Each 20” bike was as- sembled and included a helmet and bike lock. U.S. Marines handling the local Toys for Tots program picked up the bikes and other toys during JLab’s Children’s Holiday Party, Dec. 10. Special thanks to Larry’s son and Santa’s Little Helper (aka Ned King) for bike assem- bly, set-up and tire inflation assistance!

Jan./Feb. 2006 • ON TARGET 15 Determine JLab status has specifically informed you that you TIAA-CREF offers retire- are designated as “essential personnel” during, after severe weather for a weather-related event, be alert ment counseling sessions If there is a delayed opening or JLab for special instructions. All others — The 2006 spring schedule for indi- closure due to severe weather, there are employees, users and contractors — are vidual counseling sessions with Anthony three primary ways for employees, users subject to closure status instructions and Kohlrus, TIAA-CREFF senior individual and contractors to get current informa- shouldn’t return to JLab before the time consultant, is posted. This is an oppor- tion on JLab’s operating schedule. For specified. tunity for JLab employees to discuss the updated, recorded messages, call the The Lab’s procedures for winter current status of their account, invest- main phone number, (757) 269-7100, storms are posted in the EH&S Manual, ment strategy and retirement goals with which can handle up to 16 calls simul- Appendix 3510-T4 under the heading Kohlrus, according to Doug Roeder, taneously; or call the JLab Status Line, “Winter Storms.” (www.jlab.org/ehs/ Compensation and Benefits. The dates (757) 232-2000, which can receive up to manual/PDF/3510T4SevereWeather.pdf) available are: Thursday, March 16; 20 calls at a time; or visit the JLab web- The Lab’s Administrative Manual Thursday, April 13; Thursday, May 11; site (www.jlab.org/) where weather clos- (section 207.08.D.2) contains policy and Thursday, June 15. ing or delay information will be posted regarding taking leave due to a weather To sign up for an appointment go to as a banner message. JLab closing/delay emergency and states: “Employees, www://tiaa-cref.org click on Meetings/ information is also given to local TV who, on their own, decide that weather Counseling and follow the menu or you and radio stations but JLab cannot guar- conditions preclude their attendance or may call 800-842-2008. Sessions will antee that the information will be aired. requires their early departure, may take be held in VARC (Bldg. 28), room 40A. If after checking these avenues you vacation leave provided they obtain the are still uncertain about going to work, advance approval of their supervisor.” call your supervisor. If your supervisor

Jefferson Lab/MS 12B 12000 Jefferson Avenue Newport News, VA 23606 On Target is published by the Thomas Jefferson National Accelerator Facility, a national nuclear physics research laboratory in Newport News, VA, operated by the Southeastern Universities Research Association for the U.S. Department of Energy’s Office of Science. News items are published on a space-available basis and are sub- ject to editing. Submit news items to the Jefferson Lab Public Affairs Office, MS12B, 12000 Jefferson Avenue, Newport News, VA 23606. Editors Linda Ware Debbie Magaldi Contributing Writers Kandice Carter Judi Tull Photographer Greg Adams

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16 ON TARGET • Jan./Feb. 2006