This document presents the motivation, experimental method, manpower and schedule for the Nab experiment at the Fundamental Neutron Physics Beamline at the SNS. Thanks to its highly precise theoretical treatment within the framework of the standard model and high sensitivity to departures from the basic V −A description, neutron beta decay offers an attractive platform for searches for signals of new physics. The Nab experiment will precisely measure beta decays of the unpolarized neutron, with the goal to determine the electron–neutrino correlation with relative precision of 10−3, and the Fierz interference term, a distortion of the beta spectrum never before measured in neutron decay, with an uncertainty of ∼ 3× 10−3. These results will lead to a new precise determination of the ratio λ = GA/GV and to significant reductions in the allowed limits for both rightand left-handed scalar and tensor currents. Alternatively, the experiment will detect a nonzero signal consistent with certain realizations of supersymmetry. An optimized asymmetric magnetic and electrostatic spectrometer has been designed to achieve the required narrow momentum response function, and thus accomplish the physics goals of the experiment. Detailed breakdown of equipment cost, schedule of activities and distribution of collaborator effort are appended in separate spreadsheets. ∗Experiment Manager †Co-Spokesmen ‡On-site Manager Nab experiment at SNS/FnPB Proposal update and funding request 1. Physics motivation Neutron β decay, n → peν̄e, is one of the basic processes in nuclear physics. Its experimental study provides the most sensitive means to evaluate the ratio of axial-vector to vector coupling constants λ = GA/GV . The precise value of λ is important in many applications of the theory of weak interactions, especially in astrophysics; e.g., a star’s neutrino production is proportional to λ. More precise measurements of neutron β-decay parameters are also important in the search for new physics. Measurement of the neutron decay rate Γ, or lifetime τn = 1/Γ, allows a determination of Vud, the u-d Cabibbo-Kobayashi-Maskawa (CKM) matrix element, independent of nuclear models, because Γ is proportional to |Vud|, as seen in the leading order expression: Γ = 1 τn = fmec 4 2π3~7 ( |GV | + 3|GA| ) ∝ |GV | ( 1 + 3|λ| ) = |Vud| |gV | GF (1 + 3|λ|) , (1) where f = 1.71482(15) is a phase space factor, me is the electron mass, gV,A the vector and axial-vector weak nucleon form factors at zero momentum transfer, respectively, and GF is the fundamental Fermi weak coupling constant. While the conservation of vector current (CVC) fixes gV at unity, two unknowns, Vud and λ, remain as variables in the above expression for Γ. Hence, an independent measurement of λ is necessary in order to determine Vud from the neutron lifetime. Several neutron decay parameters can be used to measure λ; they are discussed below. Precise knowledge of Vud helps greatly in establishing the extent to which the three-generation CKM matrix is unitary. CKM unitarity, in turn, provides an independent cross-check of the presence of certain processes and particles not included in the Standard Model (SM) of elementary particles and interactions, i.e., an independent constraint on new physics. Currently, the most accurate value of the CKM matrix element Vud is obtained from measurements of 0 → 0 nuclear β-decays, the so-called superallowed Fermi transitions [1]. However, the procedure of the extraction of Vud involves calculations of radiative and nuclear structure corrections for the Fermi transition in nuclei. Despite the fact that these calculations have been done with high precision (see [2, 8] and references therein), it is impossible to verify the values of these nuclear corrections from independent experiments, and, as discussed below, questions concerning these corrections have been raised. A problem with CKM matrix unitarity at the 2−3σ level persisted for over two decades. For example, the 2002 Review of Particle Properties [3] reported values of CKM matrix elements that yield for the first row ∆ ≡ 1− |Vud| − |Vus| − |Vub| = (32± 14)× 10−4 . (2) The situation changed drastically in 2003 and 2004 when a series of experiments at Brookhaven, Fermilab and CERN reported revised values of Kl3 decay branching ratios, leading to an upward adjustment, by about 2.5σ, of the CKM matrix element Vus [4, 5, 6]. Skipping the details of this revolutionary development, we note that a revised CKM unitarity check yields [7, 1] ∆ = (1± 10)× 10−4 . (3)

A search for exotic mesons in the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ system photoproduced by the charge exchange reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}(n)$ was carried out by the CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the photoproduction of an exotic ${J}^{PC}={1}^{\ensuremath{-}+}$ resonant state in the 1 to 2 GeV mass range. Our partial wave analysis shows production of the ${a}_{2}(1320)$ and the ${\ensuremath{\pi}}_{2}(1670)$ mesons, but no evidence for the ${a}_{1}(1260)$, nor the ${\ensuremath{\pi}}_{1}(1600)$ exotic state at the expected levels. An upper limit of 13.5 nb is determined for the exotic ${\ensuremath{\pi}}_{1}(1600)$ cross section, less than 2% of the ${a}_{2}(1320)$ production.

K. Slifer, 2 O.A. Rondón, A. Aghalaryan, A. Ahmidouch, R. Asaturyan, F. Bloch, W. Boeglin, P. Bosted, C. Carasco, R. Carlini, J. Cha, J.P. Chen, M.E. Christy, L. Cole, L. Coman, D. Crabb, S. Danagoulian, D. Day, J. Dunne, M. Elaasar, R. Ent, H. Fenker, E. Frlez, D. Gaskell, L. Gan, J. Gomez, B. Hu, J. Jourdan, M. K. Jones, C. Keith, C.E. Keppel, M. Khandaker, A. Klein, L. Kramer, Y. Liang, J. Lichtenstadt, R. Lindgren, D. Mack, P. McKee, D. McNulty, 15 D. Meekins, H. Mkrtchyan, R. Nasseripour, I. Niculescu, K. Normand, B. Norum, D. Pocanic, Y. Prok, B. Raue, J. Reinhold, J. Roche, D. Kiselev (nee Rohe), 16 N. Savvinov, B. Sawatzky, M. Seely, I. Sick, C. Smith, G. Smith, S. Stepanyan, L. Tang, S. Tajima, G. Testa, W. Vulcan, K. Wang, G. Warren, 7 F.R. Wesselmann, 12 S. Wood, C. Yan, L. Yuan, J. Yun, M. Zeier, and H. Zhu

M. Bychkov, ∗ D. Počanić, † B. A. VanDevender, ‡ V. A. Baranov, W. Bertl, Yu. M. Bystritsky, E. Frlež, V. A. Kalinnikov, N. V. Khomutov, A. S. Korenchenko, S. M. Korenchenko, M. Korolija, T. Kozlowski, N. P. Kravchuk, N. A. Kuchinsky, W. Li, § D. Mekterović, D. Mzhavia, 6 S. Ritt, P. Robmann, O. A. Rondon-Aramayo, A. M. Rozhdestvensky, T. Sakhelashvili, S. Scheu, U. Straumann, I. Supek, Z. Tsamalaidze, 6 A. van der Schaaf, E. P. Velicheva, V. P. Volnykh, Y. Wang, ¶ and H.-P. Wirtz ∗∗ Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA Joint Institute for Nuclear Research, RU-141980 Dubna, Russia Paul Scherrer Institute, Villigen PSI, CH-5232, Switzerland Rudjer Bošković Institute, HR-10000 Zagreb, Croatia Institute for Nuclear Studies, PL-05-400 Swierk, Poland Institute for High Energy Physics, Tbilisi State University, GUS-380086 Tbilisi, Georgia Physik Institut der Universität Zürich, CH-8057 Zürich, Switzerland (Dated: 9 Apr 2008)

Citation for published version: Nasseripour, R, Raue, BA, Carman, DS, Ambrozewicz, P, Amaryan, MJ, Anciant, E, Anghinolfi, M, Asavapibhop, B, Asryan, G, Audit, G, Auger, T, Avakian, H, Bagdasaryan, H, Baillie, N, Ball, JP, Baltzell, NA, Barrow, S, Battaglieri, M, Beard, K, Bedlinskiy, I, Bektasoglu, M, Bellis, M, Benmouna, N, Berman, BL, Biselli, AS, Blaszczyk, L, Bonner, BE, Bouchigny, S, Boiarinov, S, Bradford, R, Branford, D, Briscoe, WJ, Brooks, WK, Burkert, VD, Butuceanu, C, Calarco, JR, Careccia, SL, Casey, L, Cetina, C, Chen, S, Cheng, L, Cole, PL, Collins, P, Coltharp, P, Cords, D, Corvisiero, P, Crabb, D, Crede, V, Thompson, R, Watts, DP & CLAS Collaboration 2008, 'Polarized structure function sigma(')(LT) for H-1((e)over-rightarrow,e(')K(+))Lambda in the nucleon resonance region', Physical Review C, vol. 77, no. 6, 065208, pp. -. https://doi.org/10.1103/PhysRevC.77.065208

Received 30 March 2006DOI:https://doi.org/10.1103/PhysRevLett.96.169905©2006 American Physical Society

V. Kubarovsky, M. Battaglieri, R. De Vita, J. Goett, L. Guo, G. S. Mutchler, P. Stoler, D. P. Weygand, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, N. Baillie, J. P. Ball, N. A. Baltzell, V. Batourine, I. Bedlinskiy, M. Bellis, N. Benmouna, B. L. Berman, A. S. Biselli, S. Bouchigny, S. Boiarinov, R. Bradford, D. Branford, W. J. Briscoe, W. K. Brooks, S. Bültmann, V. D. Burkert, C. Butuceanu, J. R. Calarco, S. L. Careccia, D. S. Carman, S. Chen, E. Clinton, P. L. Cole, P. Collins, P. Coltharp, D. Crabb, H. Crannell, V. Crede, J. P. Cummings, R. De Masi, D. Dale, E. De Sanctis, P. V. Degtyarenko, A. Deur, K. V. Dharmawardane, C. Djalali, G. E. Dodge, J. Donnelly, D. Doughty, M. Dugger, O. P. Dzyubak, H. Egiyan,* K. S. Egiyan, L. Elouadrhiri, P. Eugenio, G. Fedotov, H. Funsten, M. Y. Gabrielyan, L. Gan, M. Garçon, A. Gasparian, G. Gavalian, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, O. Glamazdin, J. T. Goetz, E. Golovach, A. Gonenc, C. I. O. Gordon, R. W. Gothe, K. A. Griffioen, M. Guidal, N. Guler, V. Gyurjyan, C. Hadjidakis, K. Hafidi, R. S. Hakobyan, J. Hardie, F. W. Hersman, K. Hicks, I. Hleiqawi, M. Holtrop, C. E. Hyde-Wright, Y. Ilieva, D. G. Ireland, B. S. Ishkhanov, E. L. Isupov, M. M. Ito, D. Jenkins, H. S. Jo, K. Joo, H. G. Juengst, J. D. Kellie, M. Khandaker, W. Kim, A. Klein, F. J. Klein, A. V. Klimenko, M. Kossov, L. H. Kramer, J. Kuhn, S. E. Kuhn, S. V. Kuleshov, J. Lachniet, J. M. Laget, J. Langheinrich, D. Lawrence, T. Lee, Ji Li, K. Livingston, H. Lu, M. MacCormick, N. Markov, B. McKinnon, B. A. Mecking, J. J. Melone, M. D. Mestayer, C. A. Meyer, T. Mibe, K. Mikhailov, R. Minehart, M. Mirazita, R. Miskimen, V. Mochalov, V. Mokeev, L. Morand, S. A. Morrow, M. Moteabbed, P. Nadel-Turonski, I. Nakagawa, R. Nasseripour, S. Niccolai, G. Niculescu, I. Niculescu, B. B. Niczyporuk, M. R. Niroula, R. A. Niyazov, M. Nozar, M. Osipenko, A. I. Ostrovidov, K. Park, E. Pasyuk, C. Paterson, J. Pierce, N. Pivnyuk, D. Pocanic, O. Pogorelko, S. Pozdniakov, J. W. Price, Y. Prok, D. Protopopescu, B. A. Raue, G. Riccardi, G. Ricco, M. Ripani, B. G. Ritchie, F. Ronchetti, G. Rosner, P. Rossi, F. Sabatié, C. Salgado, J. P. Santoro, V. Sapunenko, R. A. Schumacher, V. S. Serov, Y. G. Sharabian, N. V. Shvedunov, E. S. Smith, L. C. Smith, D. I. Sober, A. Stavinsky, S. S. Stepanyan, S. Stepanyan, B. E. Stokes, I. I. Strakovsky, S. Strauch,18,x M. Taiuti, D. J. Tedeschi, A. Teymurazyan, U. Thoma,2,k A. Tkabladze, S. Tkachenko, L. Todor, C. Tur, M. Ungaro, M. F. Vineyard, A. V. Vlassov, L. B. Weinstein, M. Williams, E. Wolin, M. H. Wood,4,{ A. Yegneswaran, L. Zana, J. Zhang, and B. Zhao

R. Bradford,1,∗ R. A. Schumacher,1 J. W. C. McNabb,1 L. Todor,1 G. Adams,29 P. Ambrozewicz,10 E. Anciant,5 M. Anghinolfi,16 B. Asavapibhop,22 G. Asryan,38 G. Audit,5 H. Avakian,15,33 H. Bagdasaryan,27 N. Baillie,37 J. P. Ball,2 N. A. Baltzell,32 S. Barrow,11 V. Batourine,20 M. Battaglieri,16 K. Beard,19 I. Bedlinskiy,18 M. Bektasoglu,27,† M. Bellis,1 N. Benmouna,12 B. L. Berman,12 N. Bianchi,15 A. S. Biselli,1,29 B. E. Bonner,30 S. Bouchigny,17,33 S. Boiarinov,18,33 D. Branford,9 W. J. Briscoe,12 W. K. Brooks,33 S. Bültmann,27 V. D. Burkert,33 C. Butuceanu,37 J. R. Calarco,24 S. L. Careccia,27 D. S. Carman,26 B. Carnahan,4 S. Chen,11 P. L. Cole,14,33 A. Coleman,37 P. Coltharp,11 P. Corvisiero,16 D. Crabb,36 H. Crannell,4 J. P. Cummings,29 R. DeVita,16 E. De Sanctis,15 P. V. Degtyarenko,33 H. Denizli,28 L. Dennis,11 A. Deur,33 K. V. Dharmawardane,27 K. S. Dhuga,12 C. Djalali,32 G. E. Dodge,27 J. Donnelly,13 D. Doughty,6,33 P. Dragovitsch,11 M. Dugger,2 S. Dytman,28 O. P. Dzyubak,32 H. Egiyan,33,37 K. S. Egiyan,38 L. Elouadrhiri,6,33 A. Empl,29 P. Eugenio,11 R. Fatemi,36 G. Fedotov,23 G. Feldman,12 R. J. Feuerbach,1 T. A. Forest,27 H. Funsten,37 M. Garçon,5 G. Gavalian,27,38 G. P. Gilfoyle,31 K. L. Giovanetti,19 F. X. Girod,5 J. T. Goetz,3 E. Golovatch,16 A. Gonenc,10 R. W. Gothe,32 K. A. Griffioen,37 M. Guidal,17 M. Guillo,32 N. Guler,27 L. Guo,33 V. Gyurjyan,33 C. Hadjidakis,17 R. S. Hakobyan,4 J. Hardie,6,33 D. Heddle,6,33 F. W. Hersman,24 K. Hicks,26 I. Hleiqawi,26 M. Holtrop,24 J. Hu,29 M. Huertas,32 C. E. Hyde-Wright,27 Y. Ilieva,12 D. G. Ireland,13 B. S. Ishkhanov,23 M. M. Ito,33 D. Jenkins,35 H. S. Jo,17 K. Joo,7,36 H. G. Juengst,27 J. D. Kellie,13 M. Khandaker,25 K. Y. Kim,28 K. Kim,20 W. Kim,20 A. Klein,27 F. J. Klein,4,33 A. V. Klimenko,27 M. Klusman,29 M. Kossov,18 L. H. Kramer,10,33 V. Kubarovsky,29 J. Kuhn,1 S. E. Kuhn,27 S. V. Kuleshov,18 J. Lachniet,1 J. M. Laget,5,33 J. Langheinrich,32 D. Lawrence,22 A. C. S. Lima,12 K. Livingston,13 K. Lukashin,33 J. J. Manak,33 C. Marchand,5 S. McAleer,11 B. McKinnon,13 B. A. Mecking,33 M. D. Mestayer,33 C. A. Meyer,1 T. Mibe,26 K. Mikhailov,18 R. Minehart,36 M. Mirazita,15 R. Miskimen,22 V. Mokeev,23 S. A. Morrow,5,17 V. Muccifora,15 J. Mueller,28 G. S. Mutchler,30 P. Nadel-Turonski,12 J. Napolitano,29 R. Nasseripour,32 S. Niccolai,12,17 G. Niculescu,19,26 I. Niculescu,12,19 B. B. Niczyporuk,33 R. A. Niyazov,27,33 M. Nozar,33 G. V. O’Rielly,12 M. Osipenko,16,23 A. I. Ostrovidov,11 K. Park,20 E. Pasyuk,2 C. Paterson,13 S. A. Philips,12 J. Pierce,36 N. Pivnyuk,18 D. Pocanic,36 O. Pogorelko,18 E. Polli,15 I. Popa,12 S. Pozdniakov,18 B. M. Preedom,32 J. W. Price,3 Y. Prok,36 D. Protopopescu,13 L. M. Qin,27 B. P. Quinn,1 B. A. Raue,10,33 G. Riccardi,11 G. Ricco,16 M. Ripani,16 B. G. Ritchie,2 F. Ronchetti,15 G. Rosner,13 P. Rossi,15 D. Rowntree,21 P. D. Rubin,31 F. Sabatié,5,27 C. Salgado,25 J. P. Santoro,33,35 V. Sapunenko,16,33 V. S. Serov,18 A. Shafi,12 Y. G. Sharabian,33,38 J. Shaw,22 S. Simionatto,12 A. V. Skabelin,21 E. S. Smith,33 L. C. Smith,36 D. I. Sober,4 M. Spraker,8 A. Stavinsky,18 S. S. Stepanyan,20 S. Stepanyan,33,38 B. E. Stokes,11 P. Stoler,29 I. I. Strakovsky,12 S. Strauch,12 R. Suleiman,21 M. Taiuti,16 S. Taylor,30 D. J. Tedeschi,32 U. Thoma,33 R. Thompson,28 A. Tkabladze,26 S. Tkachenko,27 C. Tur,32 M. Ungaro,7,29 M. F. Vineyard,31,34 A. V. Vlassov,18 K. Wang,36 L. B. Weinstein,27 H. Weller,8 D. P. Weygand,33 M. Williams,1 E. Wolin,33 M. H. Wood,32 A. Yegneswaran,33 J. Yun,27 L. Zana,24 J. Zhang,27 and B. Zhao7 (CLAS Collaboration) 1Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA 2Arizona State University, Tempe, Arizona 85287-1504, USA 3University of California at Los Angeles, Los Angeles, California 90095-1547, USA 4Catholic University of America, Washington, DC 20064, USA 5CEA-Saclay, Service de Physique Nucléaire, F-91191 Gif-sur-Yvette, Cedex, France 6Christopher Newport University, Newport News, Virginia 23606, USA 7University of Connecticut, Storrs, Connecticut 06269, USA 8Duke University, Durham, North Carolina 27708-0305, USA 9Edinburgh University, Edinburgh EH9 3JZ, United Kingdom 10Florida International University, Miami, Florida 33199, USA 11Florida State University, Tallahassee, Florida 32306, USA 12The George Washington University, Washington, DC 20052, USA 13University of Glasgow, Glasgow G12 8QQ, United Kingdom 14Idaho State University, Pocatello, Idaho 83209, USA 15INFN, Laboratori Nazionali di Frascati, Frascati, Italy 16INFN, Sezione di Genova, I-16146 Genova, Italy 17Institut de Physique Nucleaire ORSAY, Orsay, France 18Institute of Theoretical and Experimental Physics, Moscow, RU-117259, Russia 19James Madison University, Harrisonburg, Virginia 22807, USA 20Kyungpook National University, Daegu 702-701, South Korea 21Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA 22University of Massachusetts, Amherst, Massachusetts 01003, USA 23Moscow State University, General Nuclear Physics Institute, RU-119899 Moscow, Russia 24University of New Hampshire, Durham, New Hampshire 03824-3568, USA 25Norfolk State University, Norfolk, Virginia 23504, USA

The exclusive reactions (cid:1)p ! (cid:1) K 0 K (cid:1) n and (cid:1)p ! (cid:1) K 0 K 0 p have been studied in the photon energy range 1.6–3.8 GeV, searching for evidence of the exotic baryon (cid:2) (cid:1) (cid:2) 1540 (cid:3) in the decays (cid:2) (cid:1) ! nK (cid:1) and (cid:2) (cid:1) ! pK 0 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The integrated luminosity was about 70 pb (cid:4) 1 . The reactions have been isolated by detecting the K (cid:1) and proton directly, the neutral kaon via its decay to K S ! (cid:2) (cid:1) (cid:2) (cid:4) and the neutron or neutral kaon via the missing mass technique. The mass and width of known hyperons such as (cid:3) (cid:1) , (cid:3) (cid:4) and (cid:4) (cid:2) 1116 (cid:3) were used as a check of the mass determination accuracy and experimental resolution. Approximately 100 000 (cid:4) (cid:5) (cid:2) 1520 (cid:3) ’s and 150 000 (cid:3) ’s were observed in the (cid:1) K 0 K (cid:1) n and (cid:1) K 0 K 0 p final state, respectively. No evidence for the (cid:2) (cid:1) pentaquark was found in the nK (cid:1) or pK S invariant mass spectra. Upper limits were set on the production cross section of the reaction (cid:1)p ! (cid:1) K 0 (cid:2) (cid:1) as functions of center-of-mass angle, nK (cid:1) and pK S masses. Combining the results of the two reactions, the 95% C.L. upper limit on the total cross section for a resonance peaked at 1540 MeV was found to be 0.7 nb. Within most of the available theoretical models, this corresponds to an upper limit on the (cid:2) (cid:1) width, (cid:5) (cid:2) (cid:1) , ranging between 0.01 and 7 MeV.

The exclusive reactions gamma p ->(K) over bar (0)K(+)n and gamma p ->(K) over bar (0)K(0)p have been studied in the photon energy range 1.6-3.8 GeV, searching for evidence of the exotic baryon Theta(+)(1540) in the decays Theta(+)-> nK(+) and Theta(+)-> pK(0). Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The integrated luminosity was about 70 pb(-1). The reactions have been isolated by detecting the K+ and proton directly, the neutral kaon via its decay to K-S ->pi(+)pi(-) and the neutron or neutral kaon via the missing mass technique. The mass and width of known hyperons such as Sigma(+), Sigma(-) and Lambda(1116) were used as a check of the mass determination accuracy and experimental resolution. Approximately 100 000 Lambda(*)(1520)'s and 150 000 phi's were observed in the (K) over bar (0)K(+)n and (K) over bar (0)K(0)p final state, respectively. No evidence for the Theta(+) pentaquark was found in the nK(+) or pK(S) invariant mass spectra. Upper limits were set on the production cross section of the reaction gamma p ->(K) over bar (0)Theta(+) as functions of center-of-mass angle, nK(+) and pK(S) masses. Combining the results of the two reactions, the 95% C.L. upper limit on the total cross section for a resonance peaked at 1540 MeV was found to be 0.7 nb. Within most of the available theoretical models, this corresponds to an upper limit on the Theta(+) width, Gamma(+)(Theta), ranging between 0.01 and 7 MeV.

We review the recent experimental and theoretical progress in the determination of |Vud| and |Vus|, and the status of the most stringent test of CKM unitarity. Future prospects on |Vcd| and |Vcs| are also briefly discussed.