Helicity Asymmetry in gamma p -> pi+ n with FROST

The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction gamma p to pi+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses.Comment: Contribution to the Proceedings of NSTAR 2011 - The 8th International Workshop on the Physics of Excited Nucleons, May 17-20, 2011, Thomas Jefferson National Accelerator Facility, Newport News, Virginia US

\u3cem\u3ecis\u3c/em\u3e-(Diethyldithiocarbamato)diiodo(phenyl)tellurium(IV), PhTe(S\u3csub\u3e2\u3c/sub\u3eCNEt\u3csub\u3e2\u3c/sub\u3e)I\u3csub\u3e2\u3c/sub\u3e, and its Methoxy-Substituted Mixed Br/1 Analogue \u3cem\u3ecis\u3c/em\u3e-Bis(0.4-bromo/0.6-iodo)-(diethyldithiocarbamato)(4-methoxyphenyl) tellurium(IV), \u3cem\u3ep\u3c/em\u3e-MeOC\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3eTe(S\u3csub\u3e2\u3c/sub\u3e CNEt\u3csub\u3e2\u3c/sub\u3e)(Br\u3csub\u3e0.4\u3c/sub\u3eI\u3csub\u3e0.6\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e

The TeIV complexes PhTe(S2CNEt2)I2, (1), and p-MeOC6H4Te(S2CNEt2)Br0.4/I0.6) 2, (2), have been synthesized by reacting PhTeI3 with NaS2CNEt2, and p-MeOC6H4Te(S2CNEt2)2I with Br2, respectively. In (2), both I atoms are partially replaced by Br atoms in a 3:2 ratio. The structures display distorted octahedral Te coordination with two symmetrically coordinated S atoms [Te—S 2.550 (2)—2.569 (2) Å in three independent molecules of (1) and 2.523 (1) Å in (2)] and with two cis-disposed halogen atoms [Te—I 2.941 (1)—2.986 (1) Å in (1) and 3.003 (4) and 3.049 (3) Å in (2); Te—Br 2.962(8) and 2.967 (8) Å in (2)] in equatorial positions. The aryl group is axial in both complexes [Te—C 2.137(6)—2.146(6) and 2.123(5) Å in (1) and (2) respectively] and the second axial position is occupied by a halogen atom of a neighbouring molecule [Te⋅⋅⋅I 3.898(1)—4233(1) Å in (1); Te⋅ ⋅ ⋅I3872(3) Å and Te⋅ ⋅ ⋅Br 3.676(6) Å in (2); trans angles C---Te⋅ ⋅ ⋅ (Br) 153.4(2)—177.7(2)°] so that the molecules are joined into (quasi)centrosymmetric pairs by these secondary interactions

Medium Modification of the Proton Form Factor

I argue that the double ratio of proton-recoil polarization-transfer coefficients, P'_x and P'_z, of the quasielastic 4He(e,e'p)3H reaction with respect to the elastic 1H(e,e'p) reaction is sensitive to possible medium modifications of the proton form factor in 4He. Recent measurements at both Mainz and Jefferson Lab of this double ratio at four-momentum transfers squared between between 0.4 GeV2 and 2.6 GeV2 are discussed. I show that the data challenge state-of-the-art conventional meson-nucleon calculations, as these are unable to describe the results. The data hint at the need to include medium modifications of the proton form factor, as predicted by a quark-meson-coupling model, in the calculations. A recently approved follow-up experiment at a Q2 of 0.8 GeV2 and 1.3 GeV2 with unprecedented precision will provide one of the most stringent tests of the applicability of various calculations.Comment: presented at ``Fourth International Conference on Perspectives in Hadronic Physics'', ICTP, Trieste, 12 -- 16 May 200

NSTAR 2017

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Nucleon Spectroscopy with CLAS

Meson photoproduction is an important tool in the study of nucleon resonances. The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of polarization observables. The N* program at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) includes experimental studies with linearly- and circularly-polarized tagged-photon beams, longitudinally- and transversely-polarized nucleon targets, and recoil polarizations. Selected results from these experimental studies will be presented

A study on the psychometric properties of the short version of the physical activity enjoyment scale in an adult population

A new measure of the short form of the Physical Activity Enjoyment Scale (PACES-S), including four items, has been developed that focuses on the subjective experience of enjoyment. As validation has so far only been conducted in a youth population, the purpose of the present article was to test the psychometric properties of the measure in an adult population in three studies. In the first study (n = 1017) the results supported the unidimensional structure of the instrument (χ2 = 10.0; df = 2; p < 0.01; CFI = 0.992; RMSEA = 0.063), revealed a satisfactory level of internal consistency (ω = 0.79), and showed that the measure is invariant across gender. The results on factorial validity and internal consistency were generally supported by the second study (n = 482), which additionally showed satisfactory test–retest reliability (r = 0.73). Finally, the third study (n = 1336) also supported the factorial validity and internal consistency of the measure and additionally showed a positive correlation with physical activity (r = 0.40), thus supporting the criterion-related validity of the measure. This more economical version of PACES seems to be particularly useful for large-scale studies

Implementation of a Toffoli Gate with Superconducting Circuits

The quantum Toffoli gate allows universal reversible classical computation. It is also an important primitive in many quantum circuits and quantum error correction schemes. Here we demonstrate the realization of a Toffoli gate with three superconducting transmon qubits coupled to a microwave resonator. By exploiting the third energy level of the transmon qubit, the number of elementary gates needed for the implementation of the Toffoli gate, as well as the total gate time can be reduced significantly in comparison to theoretical proposals using two-level systems only. We characterize the performance of the gate by full process tomography and Monte Carlo process certification. The gate fidelity is found to be $68.5\pm0.5$%.Comment: 4 pages, 5figure

Preparation and Measurement of Three-Qubit Entanglement in a Superconducting Circuit

Traditionally, quantum entanglement has played a central role in foundational discussions of quantum mechanics. The measurement of correlations between entangled particles can exhibit results at odds with classical behavior. These discrepancies increase exponentially with the number of entangled particles. When entanglement is extended from just two quantum bits (qubits) to three, the incompatibilities between classical and quantum correlation properties can change from a violation of inequalities involving statistical averages to sign differences in deterministic observations. With the ample confirmation of quantum mechanical predictions by experiments, entanglement has evolved from a philosophical conundrum to a key resource for quantum-based technologies, like quantum cryptography and computation. In particular, maximal entanglement of more than two qubits is crucial to the implementation of quantum error correction protocols. While entanglement of up to 3, 5, and 8 qubits has been demonstrated among spins, photons, and ions, respectively, entanglement in engineered solid-state systems has been limited to two qubits. Here, we demonstrate three-qubit entanglement in a superconducting circuit, creating Greenberger-Horne-Zeilinger (GHZ) states with fidelity of 88%, measured with quantum state tomography. Several entanglement witnesses show violation of bi-separable bounds by 830\pm80%. Our entangling sequence realizes the first step of basic quantum error correction, namely the encoding of a logical qubit into a manifold of GHZ-like states using a repetition code. The integration of encoding, decoding and error-correcting steps in a feedback loop will be the next milestone for quantum computing with integrated circuits.Comment: 7 pages, 4 figures, and Supplementary Information (4 figures)