Browsing by Author "Gao, H"

Now showing 1 - 9 of 9
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    Compton scattering from 4He at 61 MeV
    (PRC, 2017-11-27) Sikora, MH; Ahmed, MW; Banu, A; Bartram, C; Crowe, B; Downie, EJ; Feldman, G; Gao, H; Grießhammer, HW; Hao, H; Howell, CR; Karwowski, HJ; Kendellen, DP; Kovash, MA; Li, X; Markoff, DM; Mikhailov, S; Popov, V; Pywell, RE; Silano, JA; Spraker, MC; Wallace, P; Weller, HR; Whisnant, CS; Wu, YK; Xiong, W; Yan, X; Zhao, ZW
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    Compton scattering from 4He at the TUNL HIγS facility
    (PRC, 2020-03-30) Li, X; Ahmed, MW; Banu, A; Bartram, C; Crowe, B; Downie, EJ; Emamian, M; Feldman, G; Gao, H; Godagama, D; Grießhammer, HW; Howell, CR; Karwowski, HJ; Kendellen, DP; Kovash, MA; Leung, KKH; Markoff, D; Mikhailov, S; Pywell, RE; Sikora, MH; Silano, JA; Sosa, RS; Spraker, MC; Swift, G; Wallace, P; Weller, HR; Whisnant, CS; Wu, YK; Zhao, ZW
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    Compton scattering from He 4 at the TUNL HIγ S facility
    (Physical Review C, 2020-03-01) Li, X; Ahmed, MW; Banu, A; Bartram, C; Crowe, B; Downie, EJ; Emamian, M; Feldman, G; Gao, H; Godagama, D; Grießhammer, HW; Howell, CR; Karwowski, HJ; Kendellen, DP; Kovash, MA; Leung, KKH; Markoff, D; Mikhailov, S; Pywell, RE; Sikora, MH; Silano, JA; Sosa, RS; Spraker, MC; Swift, G; Wallace, P; Weller, HR; Whisnant, CS; Wu, YK; Zhao, ZW
    © 2020 American Physical Society. Differential cross sections for elastic Compton scattering from He4 have been measured with high statistical precision at the High Intensity γ-ray Source at laboratory scattering angles of 55°, 90°, and 125° using a quasi-monoenergetic photon beam with a weighted mean energy value of 81.3 MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from He4 to fully interpret the data.
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    Electron-Ion Collider: The next QCD frontier: Understanding the glue that binds us all
    (European Physical Journal A, 2016-09-01) Accardi, A; Albacete, JL; Anselmino, M; Armesto, N; Aschenauer, EC; Bacchetta, A; Boer, D; Brooks, WK; Burton, T; Chang, NB; Deng, WT; Deshpande, A; Diehl, M; Dumitru, A; Dupré, R; Ent, R; Fazio, S; Gao, H; Guzey, V; Hakobyan, H; Hao, Y; Hasch, D; Holt, R; Horn, T; Huang, M; Hutton, A; Hyde, C; Jalilian-Marian, J; Klein, S; Kopeliovich, B; Kovchegov, Y; Kumar, K; Kumerički, K; Lamont, MAC; Lappi, T; Lee, JH; Lee, Y; Levin, EM; Lin, FL; Litvinenko, V; Ludlam, TW; Marquet, C; Meziani, ZE; McKeown, R; Metz, A; Milner, R; Morozov, VS; Mueller, AH; Müller, B; Müller, D; Nadel-Turonski, P; Paukkunen, H; Prokudin, A; Ptitsyn, V; Qian, X; Qiu, JW; Ramsey-Musolf, M; Roser, T; Sabatié, F; Sassot, R; Schnell, G; Schweitzer, P; Sichtermann, E; Stratmann, M; Strikman, M; Sullivan, M; Taneja, S; Toll, T; Trbojevic, D; Ullrich, T; Venugopalan, R; Vigdor, S; Vogelsang, W; Weiss, C; Xiao, BW; Yuan, F; Zhang, YH; Zheng, L
    © 2016, The Author(s). This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.
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    Experimental study of the A(e,e′π+) reaction on H1, H2, C12, Al27, Cu63, and Au197
    (Physical Review C - Nuclear Physics, 2010-05-25) Qian, X; Horn, T; Clasie, B; Arrington, J; Asaturyan, R; Benmokhtar, F; Boeglin, W; Bosted, P; Bruell, A; Christy, ME; Chudakov, E; Dalton, MM; Daniel, A; Day, D; Dutta, D; El Fassi, L; Ent, R; Fenker, HC; Ferrer, J; Fomin, N; Gao, H; Garrow, K; Gaskell, D; Gray, C; Huber, GM; Jones, MK; Kalantarians, N; Keppel, CE; Kramer, K; Li, Y; Liang, Y; Lung, AF; Malace, S; Markowitz, P; Matsumura, A; Meekins, DG; Mertens, T; Miyoshi, T; Mkrtchyan, H; Monson, R; Navasardyan, T; Niculescu, G; Niculescu, I; Okayasu, Y; Opper, AK; Perdrisat, C; Punjabi, V; Rauf, AW; Rodriquez, VM; Rohe, D; Seely, J; Segbefia, E; Smith, GR; Sumihama, M; Tadevosyan, V; Tang, L; Villano, A; Vulcan, WF; Wesselmann, FR; Wood, SA; Yuan, L; Zheng, X
    Cross sections for the H1(e,e′π+)n process on H1, H2, C12, Al27, Cu63, and Au197 targets were measured at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) to extract nuclear transparencies. Data were taken from Q2=1.1-4.7 GeV2 for a fixed center-of-mass energy of W=2.14 GeV. The ratio of σL and σT was extracted from the measured cross sections for H1, H2, C12, and Cu63 targets at Q2=2.15 and 4.0 GeV2, allowing for additional studies of the reaction mechanism. In this article, we present the experimental setup and the analysis of the data in detail, including systematic uncertainty studies. Differential cross sections and nuclear transparencies as a function of the pion momentum at different values of Q2 are presented. Our results are consistent with the predicted early onset of color transparency in mesons. Global features of the data are discussed and the data are compared with model calculations for the H1(e,e′π+)n reaction from nuclear targets. © 2010 The American Physical Society.
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    Genetic signatures in the envelope glycoproteins of HIV-1 that associate with broadly neutralizing antibodies.
    (PLoS Comput Biol, 2010-10-07) Gnanakaran, S; Daniels, MG; Bhattacharya, T; Lapedes, AS; Sethi, A; Li, M; Tang, H; Greene, K; Gao, H; Haynes, BF; Cohen, MS; Shaw, GM; Seaman, MS; Kumar, A; Gao, F; Montefiori, DC; Korber, B
    A steady increase in knowledge of the molecular and antigenic structure of the gp120 and gp41 HIV-1 envelope glycoproteins (Env) is yielding important new insights for vaccine design, but it has been difficult to translate this information to an immunogen that elicits broadly neutralizing antibodies. To help bridge this gap, we used phylogenetically corrected statistical methods to identify amino acid signature patterns in Envs derived from people who have made potently neutralizing antibodies, with the hypothesis that these Envs may share common features that would be useful for incorporation in a vaccine immunogen. Before attempting this, essentially as a control, we explored the utility of our computational methods for defining signatures of complex neutralization phenotypes by analyzing Env sequences from 251 clonal viruses that were differentially sensitive to neutralization by the well-characterized gp120-specific monoclonal antibody, b12. We identified ten b12-neutralization signatures, including seven either in the b12-binding surface of gp120 or in the V2 region of gp120 that have been previously shown to impact b12 sensitivity. A simple algorithm based on the b12 signature pattern was predictive of b12 sensitivity/resistance in an additional blinded panel of 57 viruses. Upon obtaining these reassuring outcomes, we went on to apply these same computational methods to define signature patterns in Env from HIV-1 infected individuals who had potent, broadly neutralizing responses. We analyzed a checkerboard-style neutralization dataset with sera from 69 HIV-1-infected individuals tested against a panel of 25 different Envs. Distinct clusters of sera with high and low neutralization potencies were identified. Six signature positions in Env sequences obtained from the 69 samples were found to be strongly associated with either the high or low potency responses. Five sites were in the CD4-induced coreceptor binding site of gp120, suggesting an important role for this region in the elicitation of broadly neutralizing antibody responses against HIV-1.
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    Interannual variation of the surface temperature of tropical forests from satellite observations
    (Advances in Meteorology, 2015-05-17) Gao, H; Zhang, S; Fu, R; Li, W; Dickinson, RE
    Land surface temperatures (LSTs) within tropical forests contribute to climate variations. However, observational data are very limited in such regions. This study used passive microwave remote sensing data from the Special Sensor Microwave/Imager (SSM/I) and the Special Sensor Microwave Imager Sounder (SSMIS), providing observations under all weather conditions, to investigate the LST over the Amazon and Congo rainforests. The SSM/I and SSMIS data were collected from 1996 to 2012. The morning and afternoon observations from passive microwave remote sensing facilitate the investigation of the interannual changes of LST anomalies on a diurnal basis. As a result of the variability of cloud cover and the corresponding reduction of solar radiation, the afternoon LST anomalies tend to vary more than the morning LST anomalies. The dominant spatial and temporal patterns for interseasonal variations of the LST anomalies over the tropical rainforest were analyzed. The impacts of droughts and El Niños on this LST were also investigated. Differences between early morning and late afternoon LST anomalies were identified by the remote sensing product, with the morning LST anomalies controlled by humidity (according to comparisons with the National Centers for Environmental Prediction (NCEP) reanalysis data).
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    Radiative corrections beyond the ultra relativistic limit in unpolarized ep elastic and Møller scatterings for the PRad Experiment at Jefferson Laboratory
    (European Physical Journal A, 2015-01-01) Akushevich, I; Gao, H; Ilyichev, A; Meziane, M
    © 2015, SIF, Springer-Verlag Berlin Heidelberg.The clear 7σ discrepancy between measurements of the proton charge radius from muonic hydrogen Lamb shifts and those from hydrogen Lamb shift and electron scattering lead to both intense theoretical and experimental efforts to understand and explain this difference. In this regard, a new experiment (PRad) based on unpolarized ep elastic scattering cross section measurements normalized to Møller scattering is underway at Jefferson Laboratory to extract the proton charge radius based on new proton electric form factor down to values of momentum transfer squared Q2, as low as 10−4 GeV/c)2. To reach the precision of the experiment in such a small Q2 region requires reliable knowledge of radiative corrections. In this paper, we present a complete calculation of radiative corrections for unpolarized elastic ep and Møller scatterings performed within a covariant formalism resulting in the set of explicit formulas beyond the ultra relativistic approximation (me2 ≪ Q2), and numerical results for the kinematics of the PRad experiment.
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    Role of mesons in the electromagnetic form factors of the nucleon
    (Physical Review C - Nuclear Physics, 2010-11-30) Crawford, C; Akdogan, T; Alarcon, R; Bertozzi, W; Booth, E; Botto, T; Calarco, JR; Clasie, B; de Grush, A; Donnelly, TW; Dow, K; Farkhondeh, M; Fatemi, R; Filoti, O; Franklin, W; Gao, H; Geis, E; Gilad, S; Hasell, D; Karpius, P; Kohl, M; Kolster, H; Lee, T; Lomon, E; Maschinot, A; Matthews, J; McIlhany, K; Meitanis, N; Milner, R; Rapaport, J; Redwine, R; Seely, J; Shinozaki, A; Sindile, A; Širca, S; Six, E; Smith, T; Tonguc, B; Tschalaer, C; Tsentalovich, E; Turchinetz, W; Xiao, Y; Xu, W; Zhang, C; Zhou, Z; Ziskin, V; Zwart, T
    The roles played by mesons in the electromagnetic form factors of the nucleon are explored using as a basis a model containing vector mesons with coupling to the continuum together with the asymptotic Q2 behavior of perturbative QCD. Specifically, the vector dominance model (GKex) developed by E. L. Lomon is employed, as it is known to be very successful in representing the existing high-quality data published to date. An analysis is made of the experimental uncertainties present when the differences between the GKex model and the data are expanded in orthonormal basis functions. A main motivation for the present study is to provide insight into how the various ingredients in this model yield the measured behavior, including discussions of when dipole form factors are to be expected or not, of which mesons are the major contributors, for instance, at low Q2 or large distances, and of what effects are predicted from coupling to the continuum. Such insights are first discussed in momentum space, followed by an analysis of how different and potentially useful information emerges when both the experimental and theoretical electric form factors are Fourier transformed to coordinate space. While these Fourier transforms should not be interpreted as "charge distributions," nevertheless the roles played by the various mesons, especially those which are dominant at large or small distance scales, can be explored via such experiment-theory comparisons. © 2010 The American Physical Society.