Jefferson Science Associates, LLC Managing and Operating the Thomas Jefferson National Accelerator Facility for the U.S. Department of Energy

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1 Jefferson Science Associates, LLC Managing and Operating the Thomas Jefferson National Accelerator Facility for the U.S. Department of Energy Download and complete this form. Application for Sabbatical/Research Leave Support Program Part 1. Contact Information and Citizenship. The mailing address and address you provide below are where you will receive notification of status of your application. Name (First, MI, Last) Dipangkar Dutta Mailing Address 10C Hilbun Hall, Lee Blvd, Box 5167 City, State, Zip Mississippi State, MS, Phone Cell Country of citizenship U.S. (citizen or legal permanent resident) Other (specify) Check if applicable Visa type/date Visa status expires Alien registration number Part 2. Proposal. Attach a written proposal (no more than 3 pages please) that describes the significance of your proposed research at the Jefferson Lab, including the major research tasks anticipated in your proposal. Identify below the name of your proposal and the Jefferson Lab researcher with whom you plan to collaborate. Name of Proposal: The Proton Charge Radius Experiment JLab Collaborator: Eugene Pasyuk Part 3. Professional References. Provide the names and contact information of three professional references from whom you have requested letters of recommendation to support your proposal. References may be submitted with your application or separately mailed (see mailing information below). Upon receipt of your reference letters, JSA will notify you via . Reference #1: Name Haiyan Gao Title: Chair and Professor Institution Duke University gao@tunl.duke.edu Reference #2: Name Mahbub Khandaker Title: Chair and Professor Institution Idaho State University mahbub@jlab.org Reference #3: Name Volker Burkert Title: Hall-B Group leader Institution Jefferson Lab burkert@jlab.org Part 4. Curriculum Vita. Attach a CV (no more than 2 pages please) referencing no more than 10 publications relevant to your proposed research. Part 5. Institutional Approval. Attach your institution s approval for your sabbatical or research leave. Page 1 of 2 April 2014

2 Jefferson Science Associates, LLC Managing and Operating the Thomas Jefferson National Accelerator Facility for the U.S. Department of Energy Part 6. Application Checklist. To assist you in submitting a complete application package, use the following checklist. Part 1. Applicant Information. I have provided my contact and citizenship information. Part 2. Proposal. I have attached my proposal and provided the name of my JLab collaborator. Part 3. Professional References. I have provided the names and contact information of three professional references. JSA will contact me if letters are sent separately. Part 4. Curriculum Vita. I have provided my CV including requested publications. Part 5. Institutional Approval. I have provided my institution s approval of my leave. Other information you want to provide: Part 7. Where to Send Your Application Package. This completed application form and attachments should be ed to jsaprograms@sura.org with the subject line JSA Sabbatical Support no later than COB June 2, If you cannot submit supporting materials in electronic form, those materials may be mailed, with a copy of this application form to the following address. All supporting materials must be received no later than the announced deadline. Packages that do not include this application form via will be considered incomplete. Jefferson Science Associates, LLC c/o SURA 1201 New York Avenue, NW Suite 430 Washington, DC Attn: Chief Governance Office IMPORTANT: Failure to check this box will render your application package incomplete. I certify that the information I am providing in my application package is complete, truthful, and accurate. Your Name Dipangkar Dutta Page 2 of 2 April 2014

3 The Proton Charge Radius Experiment The root-mean-square (rms) charge radius of the proton, r p, is one of the fundamental quantities in physics. A precise knowledge of its value is critically important for the understanding of the structure of nucleon in terms of quark and gluon degrees of freedom of Quantum Chromodynamics (QCD), the current theory of strong interactions, and for the high precision spectroscopy of the hydrogen atom. The determinations of r p in the past have been based on three different measurement methods: (i) electron-proton (ep) elastic scattering yielding r p = 0.895(18) fm [1], (ii) the electronic hydrogen Lamb shift method resulting in r p = (69) fm [2] as quoted in the CODATA compilation, and (iii) the muonic hydrogen Lamb shift studies. In 2010, results from two precision measurements of the charge radius were published. The first one was from new studies of muonic hydrogen Lamb shift performed at PSI in Switzerland by Pohl et al. providing a factor of ten more precise result than all previous experiments: r p = (67) fm [3]. The second result was from MAMI at Mainz, obtained using the traditional ep scattering method by Bernauer et al. giving r p = 0.879(8) fm [4] and it is consistent with previous ep results. The muonic hydrogen measurements and analyzes of proton charge radius. Figure 1: A compilation of recent measurement was repeated and confirmed with even better precision in 2013 [5]. A compilation of recent measurements and analyzes of r p are shown in Fig. 1, as indicated, the regular hydrogen measurements disagree with the muonic hydrogen measurements by 8 σ. A very significant amount of theoretical effort had also been devoted to understanding this discrepancy, but the difference remains unresolved. This puzzle has attracted wide coverage in the science media, making it on to the cover of Nature, Science and most recently Scientific American [6]. There is an urgent need to carry out a new measurement which relies on a different technique with completely different systematic uncertainties. The PRAD Experiment The PI is a co-spokesperson of a new proposed experiment (E : PRAD experiment [7]) to perform a high precision ep elastic cross section measurement at very low four-momentum transfer squared, Q 2, from 10 4 to 10 2 GeV 2 range using a high resolution calorimeter. The experiment was approved by the JLab Program Advisory Committee (PAC) in 2012 with an A rating. In the PRAD experiment the absolute values of the ep cross sections will be normalized by a well known QED process e e e e, Møller scattering, which will be continuously measured in this experiment within similar kinematics and the same experimental acceptances. The high precision differential cross sections, measured for the first time in this low Q 2 range, will allow a sub-percent and essentially model independent extraction of the proton charge radius. This experiment will have a direct impact on the proton charge radius puzzle. The experiment will be performed in Hall B at Jefferson 1

4 Lab using the unique low-intensity electron beam control capabilities of the hall, a high resolution and high acceptance PbWO 4 calorimeter (HYCAL) which was used in the PrimEx experiment, and a novel windowless hydrogen gas flow target. The windowless hydrogen target is being constructed using NSF MRI funds. In the most recent precision measurements of elastic ep scattering cross sections from MAMI at Mainz [4], the primary source of background was the elastic and quasielastic scattering off the nuclei in the walls of the closed-cell target. Having a windowless target cell has the definitive advantage over closed cell targets in minimizing the overall background in the experiment. The PRAD experiment will critically improve all systematic uncertainties typical for the traditional magnetic spectrometer based experiments by implementing three major improvements over previous experiments: (1) The extracted ep cross sections will be normalized to a well known QED process - Møller scattering. The high resolution calorimeter HYCAL will be used to detect both the ep elastic and the ee Møllerevents within the same experimental acceptance. The energy and angular resolution of HYCAL is adequate to separate the ep events from ee events using the energy-scattering angle correlation. (2) We will reach very forward scattering angles for the first time in ep experiments covering a Q 2 range of GeV 2. The experiment will use electron beam with energy of 1.1 and 2.2 GeV. (3) In this experiment we propose to use a windowless cryo-cooled hydrogen gas flow target of thickness t hydrogen atoms/cm 2 at a beam current of 10 na. The windowless hydrogen gas flow target will sufficiently reduce the experimental background to reach the unprecedented precision of this experiment. Figure 2: A schematic of the PRAD experimental setup. Plan of Work The PRad experiment is expected to be installed in Hall-B by the end of This sabbatical request is to support the PI s stay at JLab during the period of January 1 - July 31 2

5 of During the first half of this period the PI will work with his students and post-doc and the physics liaison for PRad- Eugene Pasyuk, to perform the post installation checkout and the commissioning of the PRad experiment and get the experiment ready to collect data as soon as beam becomes available. The major equipment that has to be commissioned/recommissioned include the Hall-B tagger, the HYCAL calorimeter including the transporter, the gain monitoring system and the climate control system for the calorimeter, the GEM tracker, the EPICS based slow controls and the complete DAQ system. During this same period the online data analysis package which is currently under development will be extensively tested and validated against simulated data. The PRad experiment has a window of opportunity to run during the March - May 2015 period using any beam available during nights and weekends. The PI will work on commissioning the experiment with beam during this period and coordinate the data collection for the experiment during this period. The early data will be used to establish the experimental background, to optimize the experimental setup in order to minimize backgrounds and setup the exact trigger conditions. We will also use this data to improve and enhance the Monte Carlo simulation of the experiment. During the June - July period after the initial run period, the PI will coordinate the first pass data analysis effort and prepare the preliminary results for presentation at the Fall conferences Summary The proton radius puzzle is one of the most intriguing problems in contemporary physics. The PRad experiment at JLab has the potential to make a major impact towards resolving this puzzle. This sabbatical request will enable the PI to be present full time at JLab during the crucial commissioning and opportunistic data collection phase of the PRad experiment. This is essential for the successful commissioning and execution of the PRad experiment. References [1] I. Sick, Phys. Lett. B576, 62 (2003). [2] P.J. Mohr, B.N. Taylor, Rev. Mod. Phys. 80, 633 (2008). [3] R. Pohl et al., Nature 466, 213 (2010). [4] J.C. Bernauer et al., Phys. Rev. Lett. 105, (2010). [5] A. Antognini et al., Science 339, 417 (2013). [6] J.C. Bernauer and R. Pohl, Scientific American 310, No. 2 (2014). [7] A. Gasparian, M. Khandaker, H. Gao, and D. Dutta, JLAB Experiment E (2011) ( prog/generated/12gev/apphallb.html). 3

6 CURRICULUM VITAE Personal Data Name: Dipangkar Dutta Contact Information: Mississippi State University, (662) (Tel.) 010-C Hilbun Hall, (662) (Fax) P.O. Drawer 5167, Mississippi State, MS Employment Associate Professor Present Assistant Professor Mississippi State University, Mississippi State, Mississippi Assistant Research Professor Duke University, Medium Energy Group, Durham, North Carolina Postdoctoral to Senior Postdoctoral Research Associate Massachusetts Institute of Technology, Medium Energy Group, Cambridge, Massachusetts. Education Northwestern University, Evanston, IL ( ) Ph.D. degree in Physics, June 1999 Thesis title: The (e, e p) Reaction Mechanism in the Quasi-Elastic Region. Thesis advisers: Prof. Ralph E. Segel Indian Institute of Technology, Bombay, India ( ) B.Tech. degree in Engineering Physics, May Senior thesis: Heavy ion scattering cross-sections using a novel region-wise analysis technique. Thesis adviser: Prof. Y. K. Gambhir 1

7 Honors Henry Family Dean s Eminent Scholar (2010) Argonne National Lab, Graduate Fellowship. ( ) Student Awards Edward Leggett - Honors Research Fellowship (2008) Prajwal Mohanmurthy - Honors Research Fellowship (2010, 2011), Clinton E. Wallace Student Excellence Undergraduate Research Award (2011), Jefferson Science Associates, Undergraduate Research Award (2012) John Madsen - Honors Research Fellowship (2013, 2014) Synergistic Activities TUNL Seminar Chair, Jefferson Lab, Hall-C Steering Committee, Jefferson Lab, JSA Travel Grant Committee, present Jefferson Lab, Hall-A Collaboration Committee, Jefferson Lab, User Group Board of Directors, present Reviewer for Physics Letters B, National Science Foundation and the U.S. Department of Energy, Canada Foundation for Innovation and Research Foundation - Fladers (Belgium). Summary of Publications and Presentations 85 peer reviewed journal articles, with an average of 42 citations per article. 27 Conference proceeding and other publications. 28 invited presentations, 35 colloquium and seminars & contributed talks 3 Important Recent Publications 1. A Spin-Light Polarimeter for Multi-GeV Longitudinally Polarized Electron Beams, P. Mohanmurthy and D. Dutta, IEEE Trans. in Nucl. Sci., 61, 528 (2014). 2. The First Determination of the Weak Charge of the Proton. D. Androic et al., Phys. Rev. Lett. 111, (2013). 3. Color transparency: Past, present and future, D. Dutta, K. Hafidi, and M. Strikman, Prog. Part. Nucl. Phys., 69, 1 (2013). 2

8 1 June 2014 To whom it may concern: Dipangkar Dutta, Associate Professor at the Department of Physics & Astronomy at Mississippi State University, has applied for JSA Sabbatical Support. The Sabbatical is planned for the spring of Dr. Dutta is a lead member of the PRad collaboration. The collaboration is currently planning to run an experiment to measure the proton charge radius during the spring of 2015 in Hall B. This experiment has received scientific rating of A, and was placed on a short list of "High Impact" experiments at the PAC41 meeting in May 19-22, The PRad experimental equipment is currently being setup in Hall B. The full participation of Dr. Dutta's full in the PRad experiment is essential for the success of the experiment. As the Hall B leader I fully support his application for JSA Sabbatical support. Sincerely, Volker Burkert, Principal Staff Scientist, Hall B Leader Phone: (757) e- mail: burkert@jlab.org

9 HAIYAN GAO HENRY NEWSON PROFESSOR AND CHAIR DEPARTMENT OF PHYSICS DUKE UNIVERSITY, BOX DURHAM, NC DURHAM NORTH CAROLINA VOICE: (919) FAX: (919) URL: May 31, 2014 Dear JSA Program Committee: I am most delighted in writing a letter supporting Prof. Dipangkar Dutta's application for the JSA sabbatical program in the spring 2015 semester. I have known Dipangkar for many years - we worked together on the very first experiments in Hall C at Jefferson Lab in the mid 1990s when he was a graduate student and I was a postdoc at the time. Later he became my postdoc at MIT after he received his Ph.D. from Northwestern in early He moved to Duke University together with me in 2002 and was promoted to Research Assistant Professor in Dipangkar moved onto an Assistant Professor position at Mississippi State University (MSU) in He has been doing extremely well at MSU - he received the Dean's Eminent Scholar award at MSU in 2010, and was promoted to the rank of Associate Professor at MSU with tenure in In the last several years, Dipangkar has achieved a list of extremely impressive accomplishments: (i) his early success in 2007 in obtaining funding from the Department of Energy, and the two successful renewals with the most recent one for the period of ; (ii) he led and completed the analysis of the pion transparency experiment from Hall C at Jefferson Lab which led to a high profile publication in Physical Review Letters with a number of press coverage; (iii) he built the first ever diamond microstrip detectors that was used at Jefferson Lab as the recoil electron detector for the Compton polarimeter of the Qweak experiment successfully, the first such detectors used as tracking detectors; (iv) being a cospokesperson on a number of approved Jefferson Lab experiments and analysis proposal including a new experiment on a precise measurement of the proton charge radius, which I will discuss in somewhat more details later; (v) he built a detector and target lab for the medium energy group at MSU. Dipangkar also holds an extremely impressive record in mentoring students both at the graduate and undergraduate level. Since his move to MSU in 2006, he has advised one postdoc, four graduate students (three have completed masters degrees). Currently he is supervising three Ph.D. students with two expecting their Ph.D. degrees in He has also mentored eight undergraduate students research as well as two high school students research. Two of the undergrads won the Shakolous honors college summer research fellowship for conducting research with him in 2008 and One of the undergraduate students he mentored won an JSA award and went on to MIT as a Ph.D. student. His students have presented many talks and posters in various national and international conferences. As co-spokespersons, he and I are collaborating more closely in recent years on a new experiment to carry out a precise measurement of the proton charge radius. The proton charge radius is a fundamental quantity related to the structure of the nucleon. The precise knowledge of this quantity is important to advance our understanding about how quantum chromodynamics works in the non-perturbative region. It is also a crucial input to high precision tests of QED. Recent ultra-high precision determinations of the proton charge radius from muonic hydrogen Lamb shift measurements show a 6-8 σ difference from values from electron scattering and CODATA compilation. This has triggered great excitements in the fields of atomic, nuclear and particle physics. Is this new physics or something else? To help solve this newly developed proton radius puzzle, we proposed a new experiment (PRad) at small angles at JLab

10 using an internal gas target and an electromagnetic calorimeter as opposed to previous ep experiments using magnetic spectrometers. The experiment was approved with an A rating by the Jefferson Lab PAC39 in An NSF MRI grant for about $0.5M for the construction of this windowless gas flow target has been awarded for this experiment for which he and I are both co-pis. Dipangkar has been playing a very important role in this highly visible and also difficult experiment. Our plan for the PRad experiment is to be ready for installation at the end of the 2014 calendar year and hope to run this experiment in The JSA sabbatical program support of Dipangkar for the spring 2015 semester will allow him to spend time at JLab during the most crucial period for the PRad experiment. This support will be extremely important for the success of the PRad experiment and I encourage you to consider his application most favorably. His application has my strongest support. Please do not hesitate to contact me by phone or if you have any question or need additional information. Sincerely, Haiyan Gao

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