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104 results on '"Oussena, B."'

101. Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.

Author

Martel PP, Miskimen R, Aguar-Bartolome P, Ahrens J, Akondi CS, Annand JR, Arends HJ, Barnes W, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Jude TC, Kaeser A, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancell J, Manley DM, Meyer W, Middleton DG, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ortega Spina H, Ostrick M, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyansky V, Prakhov S, Rajabi A, Reicherz G, Rostomyan T, Sarty A, Schrauf S, Schumann S, Sikora MH, Starostin A, Steffen O, Strakovsky II, Strub T, Supek I, Thiel M, Tiator L, Thomas A, Unverzagt M, Usov Y, Watts DP, Witthauer L, Werthmüller D, and Wolfes M

Abstract

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4)  fm(4).

Published
2015
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102. Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter.

Author

Sikora MH, Watts DP, Glazier DI, Aguar-Bartolomé P, Akasoy LK, Annand JR, Arends HJ, Bantawa K, Beck R, Bekrenev VS, Berghäuser H, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Codling RF, Demissie BT, Downie EJ, Drexler P, Fil'kov LV, Freehart B, Gregor R, Hamilton D, Heid E, Hornidge D, Howdle DA, Jaegle I, Jahn O, Jude TC, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Kotulla M, Koulbardis AA, Kruglov SP, Krusche B, Lisin V, Livingston K, MacGregor IJ, Maghrbi Y, Manley DM, Marinides Z, Martinez M, McGeorge JC, McKinnon B, McNicoll EF, Mekterovic D, Metag V, Micanovic S, Middleton DG, Mushkarenkov A, Nefkens BM, Nikolaev A, Novotny R, Ostrick M, Otte PB, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov S, Robinson J, Rosner G, Rostomyan T, Schumann S, Sober DI, Starostin A, Strakovsky II, Suarez IM, Supek I, Thiel M, Thomas A, Unverzagt M, Werthmüller D, Workman RL, Zamboni I, and Zehr F

Abstract

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4

Published
2014
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103. Narrow structure in the excitation function of η photoproduction off the neutron.

Author

Werthmüller D, Witthauer L, Keshelashvili I, Aguar-Bartolomé P, Ahrens J, Annand JR, Arends HJ, Bantawa K, Beck R, Bekrenev V, Braghieri A, Branford D, Briscoe WJ, Brudvik J, Cherepnya S, Demissie B, Dieterle M, Downie EJ, Drexler P, Fil'kov LV, Fix A, Glazier DI, Hamilton D, Heid E, Hornidge D, Howdle D, Huber GM, Jaegle I, Jahn O, Jude TC, Käser A, Kashevarov VL, Kondratiev R, Korolija M, Kruglov SP, Krusche B, Kulbardis A, Lisin V, Livingston K, MacGregor IJ, Maghrbi Y, Mancell J, Manley DM, Marinides Z, Martinez M, McGeorge JC, McNicoll EF, Metag V, Middleton DG, Mushkarenkov A, Nefkens BM, Nikolaev A, Novotny R, Oberle M, Ostrick M, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov SN, Robinson J, Rosner G, Rostomyan T, Schumann S, Sikora MH, Sober D, Starostin A, Supek I, Thiel M, Thomas A, Unverzagt M, and Watts DP

Abstract

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5)  MeV and Γ=(30±15)  MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Published
2013
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104. Accurate test of chiral dynamics in the γp→π0p reaction.

Author

Hornidge D, Aguar Bartolomé P, Annand JR, Arends HJ, Beck R, Bekrenev V, Berghäuser H, Bernstein AM, Braghieri A, Briscoe WJ, Cherepnya S, Dieterle M, Downie EJ, Drexler P, Fernández-Ramírez C, Filkov LV, Glazier DI, Hall Barrientos P, Heid E, Hilt M, Jaegle I, Jahn O, Jude TC, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Koulbardis A, Krambrich D, Kruglov S, Krusche B, Laffoley AT, Lisin V, Livingston K, MacGregor IJ, Mancell J, Manley DM, McNicoll EF, Mekterovic D, Metag V, Micanovic S, Middleton DG, Moores KW, Mushkarenkov A, Nefkens BM, Oberle M, Ostrick M, Otte PB, Oussena B, Pedroni P, Pheron F, Polonski A, Prakhov S, Robinson J, Rostomyan T, Scherer S, Schumann S, Sikora MH, Starostin A, Supek I, Thiel M, Thomas A, Tiator L, Unverzagt M, Watts DP, Werthmüller D, and Witthauer L

Abstract

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσ⊥-dσ∥)/(dσ⊥+dσ∥) for the γp→π0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

Published
2013
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