Single and Double Spin Asymmetries for Pion Electro-Production From the Deuteron in the Resonance Region

The single and double spin asymmetries At and Aet have been measured in π- electro-production off the deuteron using a longitudinally polarized electron beam and a polarized ND3 target. The electron beam was polarized using a strained GaAs cathode and the target was polarized using Dynamic Nuclear Polarization. The data were collected at beam energies of 1.6, 1.7, 2.5 and 4.2 GeV in Hall B at Jefferson Lab in the spring of 2001. The final state particles were detected in the CEBAF Large Acceptance Spectrometer (CLAS). The d(e,e\u27π-p)p exclusive channel was identified using the missing mass technique and the asymmetries were extracted as a function of the momentum transfer Q2, invariant mass W, and center of mass pion angles cos (θ*) and (Φ*). The results are generally in agreement with the phenomenological model MAID at low energies, but there are discrepancies in the 2nd and 3rd resonance regions, as well as at forward angle

Traditional masonry and archaeological restoration. A case study from Salūt, Oman

[EN] This paper shows the restoration work carried out on the mudbrick structures uncovered at the Iron Age (c. 1300-300 BC) site of Salūt, in central Oman. In the region, traditional earthen architecture represented the key building technique until modern times. The traditional concept of constant upkeep is arguably the only way of efficiently preserving ancient structures. However, different mud plaster compositions were tested which could provide a better aspect and a lower static load on the structures. The work strategy was meant to be sustainable from an economic, ecological, and sociological point of view, as it also aimed at documenting and hopefully reviving the traditional earthen architecture currently endangered by the disinterest of younger generations.[ES] Este artículo describe la restauración de las estructuras de adobe descubiertas en el sitio de Salūt, en el centro de Omán, que datan de la Edad del Hierro (c. 1300-300 a. C.). En esta región, la arquitectura tradicional de tierra ha representado la técnica de construcción clave hasta tiempos modernos. El concepto tradicional de mantenimiento continuo es la única forma de preservar eficazmente las estructuras antiguas. Por otra parte, se experimentó con revocos de barro de diversa composición que pudieran conferir un mejor aspecto y una menor carga estática en las estructuras. La estrategia de trabajo pretendía ser sostenible y se fijaba como objetivo documentar y tratar de revivir la arquitectura tradicional de tierra, actualmente en peligro por el desinterés de las generaciones más jóvenes.Bizzarri, S.; Degli Esposti, M.; Careccia, C.; De Gennaro, T.; Tangheroni, E. (2021). Albañilería tradicional y restauración arqueológica. El caso de Salūt, Omán. Loggia, Arquitectura & Restauración. 0(34):46-61. https://doi.org/10.4995/loggia.2021.15063OJS4661034ALVA BALDERRAMA, A.; CHIARI, G. (1995): «Protection and conservation of excavated structures of mudbrick», en Stanley Price, P. (ed.): Conservation on archaeological excavations. With particular reference to the Mediterranean area. Roma: ICCROM, 101-112.AVANZINI, A.; DEGLI ESPOSTI, M. (eds.) (2018): «Husn Salūt and the Iron Age of South East Arabia. Excavations of the Italian Mission to Oman 2004-2014». Arabia Antica, 15. Roma: L'«Erma» di Bretschneider.BIZZARRI, S. (2015): «Restoration works at Salūt», en Avanzini, A. (ed.): In the heart of Oman. The castle of Salūt. (Ancient Oman, 1). Roma: L'«Erma» di Bretschneider, 87-95.BIZZARRI, S.; DEGLI ESPOSTI, M.; CARECCIA, C.; DE GENNARO, T.; TANGHERONI, E.; AVANZINI, N. (2020): «The use of traditional mud-based masonry in the restoration of the iron age site of Salūt (Oman). A way towards mutual preservation», International archives of the photogrammetry, remote sensing and spatial information sciences, vol. XLIV-M-1-2020, pp. 1081-1088. Disponible en / Available at: . https://doi.org/10.5194/isprs-archives-XLIV-M-1-2020-1081-2020DOAT, P.; HAYS, A.; HOUBEN, H.; MATUK, S.; VITOUXEDS, F. (1983): Construire en terre. París: Editions Alternatives.HAGO, A. W.; AL-RAWAS, A. (1997): «Properties of the Omani Sarooj». Engineering Journal of University of Qatar, 10, 81-91.ICOMOS (2003): ICOMOS Charter - Recommendations for the analysis, conservation and structural restoration of architectural heritage. Ratified by the ICOMOS 14th General Assembly in Victoria Falls, Zimbabwe, 2003. Disponible en / Available at: .MEDDAH, M. S.; BENKARI, N.; AL-BUSAIDI, M. (2019): «Potential Use of Locally and Traditionally Produced Bending Construction Material». IOP Conference Series: Materials Science and Engineering, vol. 471, n.º 4: 471,MERSHEN, B. (2010): «Unveiling the Past: the Role of Oral History in Understanding Oasis Development», en Buerkert, A.; Schlecht, E. (eds.): Oases of Oman. Livelihood System at the crossroads. Muscat: Al Roya Press & Publishing House, 60-63.OGEGA, J. J. (2011): «Oral Traditions in the Conservation of Earthen Architecture», in Rainer, L.; Bass Rivera, A.; Gandreau, D. (eds.): Terra 2008: The 10th International Conference on the Study and Conservation of Earthen Architectural Heritage. Los Angeles: The Getty Conservation Institute, 124-128.PETZET, M. (2004): «Principles of preservation: An introduction to the International Charters for Conservation and Restoration 40 years after the Venice Charter», in Petzet, M.; Ziesemer, J. (eds.): International Charters for Conservation and Restoration. Monuments & Sites. I. Munich: ICOMOS, 7-29.RAINER, L. (2008): «Deterioration and pathology of earthen architecture». In Avrami, E.; Guillaud, H.; Hardy, M. (eds.): Terra Literature Review: An Overview of Research in Earthen Architecture Conservation. Los Angeles: The Getty Conservation Institute, 45-61.RUSKULIS, O. (2009): «Mud Plasters and Renders». Appropriate Technology Journal. Disponible en / Available at: (Consultado: 15 de enero de 2020)

Target and Beam Target Spin Asymmetries in Exclusive π+ and π- Electroproduction with 1.6 to 5.7 GeV Electrons

Beam-target double-spin asymmetries and target single-spin asymmetries in exclusive π+ and quasiexclusive π- electroproduction were obtained from scattering of 1.6- to 5.7-GeV longitudinally polarized electrons from longitudinally polarized protons (for π+) and deuterons (for π-) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic range covered is 1.1 \u3c W \u3c 2.6 GeV and 0.05 \u3c Q2 \u3c 5 GeV2, with good angular coverage in the forward hemisphere. The asymmetry results were divided into approximately 40 000 kinematic bins for π+ from free protons and 15 000 bins for π- production from bound nucleons in the deuteron. The present results are found to be in reasonable agreement with fits to previous world data for W \u3c 1.7 GeV and Q2 \u3c 0.5 GeV2, with discrepancies increasing at higher values of Q2, especially for W \u3e 1.5 GeV. Very large target-spin asymmetries are observed for W \u3e 1.6 GeV. When combined with cross-section measurements, the present results can provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q2, for resonances with masses as high as 2.3 GeV

Electroexcitation of Nucleon Resonances from CLAS Data on Single Pion Electroproduction

We present results on the electroexcitation of the low mass resonances Δ(1232)P33 , N(1440)P11 , N(1520)D13 , and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of data from the Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS) detector at the Thomas Jefferson National Accelerator Facility (JLab) on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for π electroproduction off the proton. The data were analyzed using two conceptually different approaches—fixed-t dispersion relations and a unitary isobar model—allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Δ(1232)P33 show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2⩽6 GeV2 . For the Roper resonance, N(1440)P11, the data provide strong evidence that this state is a predominantly radial excitation of a three-quark (3q) ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the πN and ηN channels via comparison with the results extracted from η electroproduction. The extensive CLAS data also enabled the extraction of the γ∗p → N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision. For the N(1535)S11, these results became a challenge for quark models and may be indicative of large meson-cloud contributions or of representations of this state that differ from a 3q excitation. The transverse amplitudes for the N(1520)D13 clearly show the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 \u3e1 GeV2, confirming a long-standing prediction of the constituent quark model

Measurement of the Differential Cross Section for the Reaction γn →π⁻p from Deuterium

We report a measurement of the differential cross section for the γn →π⁻p process from the CLAS detector at Jefferson Laboratory in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles ( c.m.) between 50° and 115°. We confirm a previous indication of a broad enhancement around a c.m. energy (√ s) of 2.1 GeV at c.m. = 90° in the scaled differential cross section s7 dσdt and a rapid falloff in a center-of-mass energy region of about 400 MeV following the enhancement. Our data show an angular dependence of this enhancement as the suggested scaling region is approached for c.m. from 70° degrees to 105°

Measurement of Direct fₒ(980) Photoproduction on the Proton

We report on the results of the first measurement of exclusive f0(980) meson photoproduction on protons for Eγ = 3.0–3.8  GeV and −t = 0.4–1.0  GeV2 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the π+π− channel by performing a partial wave analysis of the reaction γp→pπ+π− . Clear evidence of the f0(980) meson was found in the interference between P and S waves at M π+π− ∼1  GeV. The S -wave differential cross section integrated in the mass range of the f0(980) was found to be a factor of about 50 smaller than the cross section for the ρ meson. This is the first time the f0(980) meson has been measured in a photoproduction experiment

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpEfrom the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ε) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2 ≈ 1.75 GeV2and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2

Photodisintegration of \u3csup\u3e4\u3c/sup\u3eHE into \u3ci\u3ep\u3c/i\u3e+\u3ci\u3et\u3c/i\u3e

The two-body photodisintegration of 4He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid 4He target. This is the first measurement of the photodisintegration of 4He above 0.4 GeV. The differential cross sections for the γ 4He →pt reaction were measured as a function of photon-beam energy and proton-scattering angle and are compared with the latest model calculations by J.-M. Laget. At 0.6−1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of 3He that demonstrated the great importance of three-body mechanisms in the energy region 0.5−0.8 GeV

Determination of the Proton Spin Structure Functions for 0.05 \u3c Q\u3csup\u3e2\u3c/sup\u3e \u3c5GEV\u3csup\u3e2\u3c/sup\u3e Using CLAS

We present the results of our final analysis of the full data set of gp1 Q2, the spin structure function of the proton, collected using CLAS at Jefferson Laboratory in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.7 GeV were scattered from proton targets 15NH3 dynamically polarized along the beam direction) and detected with CLAS. From the measured double spin asymmetries, we extracted virtual photon asymmetries Ap1 and Ap2 and spin structure functions g p1 and gp2 over a wide kinematic range (0.05 GeV2 \u3c Q2 \u3c 5 GeV2 and 1.08 GeV\u3c W \u3c 3 GeV) and calculated moments of gp1. We compare our final results with various theoretical models and expectations, as well as with parametrizations of the world data. Our data, with their precision and dense kinematic coverage, are able to constrain fits of polarized parton distributions, test pQCD predictions for quark polarizations at large x, offer a better understanding of quark-hadron duality, and provide more precise values of higher twist matrix elements in the framework of the operator product expansion