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1. Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering.

Author

Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, Magee, J, Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, and Magee, J

Abstract

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q^{2}) up to 15.75 (GeV/c)^{2}. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q^{2} and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q^{2} and attributed to hard two-photon exchange (TPE) effects, extending to 8 (GeV/c)^{2} the range of Q^{2} for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q^{2}.

Published
2022

2. Deeply Virtual Compton Scattering Cross Section at High Bjorken x_{B}.

Author

Georges, F, Georges, F, Rashad, MNH, Stefanko, A, Dlamini, M, Karki, B, Ali, SF, Lin, P-J, Ko, H-S, Israel, N, Adikaram, D, Ahmed, Z, Albataineh, H, Aljawrneh, B, Allada, K, Allison, S, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Biswas, D, Brash, E, Bulumulla, D, Campbell, J, Camsonne, A, Carmignotto, M, Castellano, J, Chen, C, Chen, J-P, Chetry, T, Christy, ME, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, De Persio, F, Deconinck, W, Defurne, M, Desnault, C, Di, D, Duer, M, Duran, B, Ent, R, Fanelli, C, Franklin, G, Fuchey, E, Gal, C, Gaskell, D, Gautam, T, Glamazdin, O, Gnanvo, K, Gray, VM, Gu, C, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, CE, Ibrahim, H, Jen, C-M, Jin, K, Jones, M, Kabir, A, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, WB, Liu, J, Liu, H, Liyanage, A, Magee, J, Malace, S, Mammei, J, Markowitz, P, McClellan, E, Mazouz, M, Meddi, F, Georges, F, Georges, F, Rashad, MNH, Stefanko, A, Dlamini, M, Karki, B, Ali, SF, Lin, P-J, Ko, H-S, Israel, N, Adikaram, D, Ahmed, Z, Albataineh, H, Aljawrneh, B, Allada, K, Allison, S, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Biswas, D, Brash, E, Bulumulla, D, Campbell, J, Camsonne, A, Carmignotto, M, Castellano, J, Chen, C, Chen, J-P, Chetry, T, Christy, ME, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, De Persio, F, Deconinck, W, Defurne, M, Desnault, C, Di, D, Duer, M, Duran, B, Ent, R, Fanelli, C, Franklin, G, Fuchey, E, Gal, C, Gaskell, D, Gautam, T, Glamazdin, O, Gnanvo, K, Gray, VM, Gu, C, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, CE, Ibrahim, H, Jen, C-M, Jin, K, Jones, M, Kabir, A, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, WB, Liu, J, Liu, H, Liyanage, A, Magee, J, Malace, S, Mammei, J, Markowitz, P, McClellan, E, Mazouz, M, and Meddi, F

Abstract

We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable x_{B}. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of x_{B}, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

Published
2022

3. Deeply Virtual Compton Scattering Cross Section at High Bjorken x_{B}.

Author

Georges, F, Georges, F, Rashad, MNH, Stefanko, A, Dlamini, M, Karki, B, Ali, SF, Lin, P-J, Ko, H-S, Israel, N, Adikaram, D, Ahmed, Z, Albataineh, H, Aljawrneh, B, Allada, K, Allison, S, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Biswas, D, Brash, E, Bulumulla, D, Campbell, J, Camsonne, A, Carmignotto, M, Castellano, J, Chen, C, Chen, J-P, Chetry, T, Christy, ME, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, De Persio, F, Deconinck, W, Defurne, M, Desnault, C, Di, D, Duer, M, Duran, B, Ent, R, Fanelli, C, Franklin, G, Fuchey, E, Gal, C, Gaskell, D, Gautam, T, Glamazdin, O, Gnanvo, K, Gray, VM, Gu, C, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, CE, Ibrahim, H, Jen, C-M, Jin, K, Jones, M, Kabir, A, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, WB, Liu, J, Liu, H, Liyanage, A, Magee, J, Malace, S, Mammei, J, Markowitz, P, McClellan, E, Mazouz, M, Meddi, F, Georges, F, Georges, F, Rashad, MNH, Stefanko, A, Dlamini, M, Karki, B, Ali, SF, Lin, P-J, Ko, H-S, Israel, N, Adikaram, D, Ahmed, Z, Albataineh, H, Aljawrneh, B, Allada, K, Allison, S, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Biswas, D, Brash, E, Bulumulla, D, Campbell, J, Camsonne, A, Carmignotto, M, Castellano, J, Chen, C, Chen, J-P, Chetry, T, Christy, ME, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, De Persio, F, Deconinck, W, Defurne, M, Desnault, C, Di, D, Duer, M, Duran, B, Ent, R, Fanelli, C, Franklin, G, Fuchey, E, Gal, C, Gaskell, D, Gautam, T, Glamazdin, O, Gnanvo, K, Gray, VM, Gu, C, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, CE, Ibrahim, H, Jen, C-M, Jin, K, Jones, M, Kabir, A, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, WB, Liu, J, Liu, H, Liyanage, A, Magee, J, Malace, S, Mammei, J, Markowitz, P, McClellan, E, Mazouz, M, and Meddi, F

Abstract

We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable x_{B}. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of x_{B}, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

Published
2022

4. Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering.

Author

Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, Magee, J, Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, and Magee, J

Abstract

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q^{2}) up to 15.75 (GeV/c)^{2}. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q^{2} and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q^{2} and attributed to hard two-photon exchange (TPE) effects, extending to 8 (GeV/c)^{2} the range of Q^{2} for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q^{2}.

Published
2022

5. Measurement of the beam-normal single-spin asymmetry for elastic electron scattering from C12 and Al27

Author

Androić, D, Androić, D, Armstrong, DS, Asaturyan, A, Bartlett, K, Beminiwattha, RS, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, RD, Christy, ME, Cornejo, JC, Dusa, S Covrig, Dalton, MM, Davis, CA, Deconinck, W, Dowd, JF, Dunne, JA, Dutta, D, Duvall, WS, Elaasar, M, Falk, WR, Finn, JM, Forest, T, Gal, C, Gaskell, D, Gericke, MTW, Gray, VM, Guo, F, Hoskins, JR, Jones, DC, Kargiantoulakis, M, King, PM, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, JP, Lee, AR, Lee, JH, Lee, L, MacEwan, S, Mack, D, Magee, JA, Mahurin, R, Mammei, J, Martin, JW, McHugh, MJ, Meekins, D, Mesick, KE, Michaels, R, Mkrtchyan, A, Mkrtchyan, H, Narayan, A, Ndukum, LZ, Nelyubin, V, Nuruzzaman, van Oers, WTH, Owen, VF, Page, SA, Pan, J, Paschke, KD, Phillips, SK, Pitt, ML, Radloff, RW, Rajotte, JF, Ramsay, WD, Roche, J, Sawatzky, B, Seva, T, Shabestari, MH, Silwal, R, Simicevic, N, Smith, GR, Solvignon, P, Spayde, DT, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, WA, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, SP, Wood, SA, Zang, P, Zhamkochyan, S, Androić, D, Androić, D, Armstrong, DS, Asaturyan, A, Bartlett, K, Beminiwattha, RS, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, RD, Christy, ME, Cornejo, JC, Dusa, S Covrig, Dalton, MM, Davis, CA, Deconinck, W, Dowd, JF, Dunne, JA, Dutta, D, Duvall, WS, Elaasar, M, Falk, WR, Finn, JM, Forest, T, Gal, C, Gaskell, D, Gericke, MTW, Gray, VM, Guo, F, Hoskins, JR, Jones, DC, Kargiantoulakis, M, King, PM, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, JP, Lee, AR, Lee, JH, Lee, L, MacEwan, S, Mack, D, Magee, JA, Mahurin, R, Mammei, J, Martin, JW, McHugh, MJ, Meekins, D, Mesick, KE, Michaels, R, Mkrtchyan, A, Mkrtchyan, H, Narayan, A, Ndukum, LZ, Nelyubin, V, Nuruzzaman, van Oers, WTH, Owen, VF, Page, SA, Pan, J, Paschke, KD, Phillips, SK, Pitt, ML, Radloff, RW, Rajotte, JF, Ramsay, WD, Roche, J, Sawatzky, B, Seva, T, Shabestari, MH, Silwal, R, Simicevic, N, Smith, GR, Solvignon, P, Spayde, DT, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, WA, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, SP, Wood, SA, Zang, P, and Zhamkochyan, S

Abstract

We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries $B_n$ on $^{12}$C and $^{27}$Al, obtained with an electron beam polarized transverse to its momentum direction. These measurements add an additional kinematic point to a series of previous measurements of $B_n$ on $^{12}$C and provide a first measurement on $^{27}$Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of 1.158 GeV. The average lab scattering angle for both targets was 7.7 degrees, and the average $Q^2$ for both targets was 0.02437 GeV$^2$ (Q=0.1561 GeV). The asymmetries are $B_n$ = -10.68 $\pm$ 0.90 stat) $\pm$ 0.57 (syst) ppm for $^{12}$C and $B_n$ = -12.16 $\pm$ 0.58 (stat) $\pm$ 0.62 (syst) ppm for $^{27}$Al. The results are consistent with theoretical predictions, and are compared to existing data. When scaled by Z/A, the Q-dependence of all the far-forward angle (theta < 10 degrees) data from $^{1}$H to $^{27}$Al can be described by the same slope out to $Q \approx 0.35$ GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep.

Published
2021

6. Measurement of the beam-normal single-spin asymmetry for elastic electron scattering from C12 and Al27

Author

Androić, D, Androić, D, Armstrong, DS, Asaturyan, A, Bartlett, K, Beminiwattha, RS, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, RD, Christy, ME, Cornejo, JC, Dusa, S Covrig, Dalton, MM, Davis, CA, Deconinck, W, Dowd, JF, Dunne, JA, Dutta, D, Duvall, WS, Elaasar, M, Falk, WR, Finn, JM, Forest, T, Gal, C, Gaskell, D, Gericke, MTW, Gray, VM, Guo, F, Hoskins, JR, Jones, DC, Kargiantoulakis, M, King, PM, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, JP, Lee, AR, Lee, JH, Lee, L, MacEwan, S, Mack, D, Magee, JA, Mahurin, R, Mammei, J, Martin, JW, McHugh, MJ, Meekins, D, Mesick, KE, Michaels, R, Mkrtchyan, A, Mkrtchyan, H, Narayan, A, Ndukum, LZ, Nelyubin, V, Nuruzzaman, van Oers, WTH, Owen, VF, Page, SA, Pan, J, Paschke, KD, Phillips, SK, Pitt, ML, Radloff, RW, Rajotte, JF, Ramsay, WD, Roche, J, Sawatzky, B, Seva, T, Shabestari, MH, Silwal, R, Simicevic, N, Smith, GR, Solvignon, P, Spayde, DT, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, WA, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, SP, Wood, SA, Zang, P, Zhamkochyan, S, Androić, D, Androić, D, Armstrong, DS, Asaturyan, A, Bartlett, K, Beminiwattha, RS, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, RD, Christy, ME, Cornejo, JC, Dusa, S Covrig, Dalton, MM, Davis, CA, Deconinck, W, Dowd, JF, Dunne, JA, Dutta, D, Duvall, WS, Elaasar, M, Falk, WR, Finn, JM, Forest, T, Gal, C, Gaskell, D, Gericke, MTW, Gray, VM, Guo, F, Hoskins, JR, Jones, DC, Kargiantoulakis, M, King, PM, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, JP, Lee, AR, Lee, JH, Lee, L, MacEwan, S, Mack, D, Magee, JA, Mahurin, R, Mammei, J, Martin, JW, McHugh, MJ, Meekins, D, Mesick, KE, Michaels, R, Mkrtchyan, A, Mkrtchyan, H, Narayan, A, Ndukum, LZ, Nelyubin, V, Nuruzzaman, van Oers, WTH, Owen, VF, Page, SA, Pan, J, Paschke, KD, Phillips, SK, Pitt, ML, Radloff, RW, Rajotte, JF, Ramsay, WD, Roche, J, Sawatzky, B, Seva, T, Shabestari, MH, Silwal, R, Simicevic, N, Smith, GR, Solvignon, P, Spayde, DT, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, WA, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, SP, Wood, SA, Zang, P, and Zhamkochyan, S

Abstract

We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries $B_n$ on $^{12}$C and $^{27}$Al, obtained with an electron beam polarized transverse to its momentum direction. These measurements add an additional kinematic point to a series of previous measurements of $B_n$ on $^{12}$C and provide a first measurement on $^{27}$Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of 1.158 GeV. The average lab scattering angle for both targets was 7.7 degrees, and the average $Q^2$ for both targets was 0.02437 GeV$^2$ (Q=0.1561 GeV). The asymmetries are $B_n$ = -10.68 $\pm$ 0.90 stat) $\pm$ 0.57 (syst) ppm for $^{12}$C and $B_n$ = -12.16 $\pm$ 0.58 (stat) $\pm$ 0.62 (syst) ppm for $^{27}$Al. The results are consistent with theoretical predictions, and are compared to existing data. When scaled by Z/A, the Q-dependence of all the far-forward angle (theta < 10 degrees) data from $^{1}$H to $^{27}$Al can be described by the same slope out to $Q \approx 0.35$ GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep.

Published
2021

7. Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering

Author

Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Gayoso, C Ayerbe, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Dusa, S Covrig, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, Magee, J, Christy, ME, Christy, ME, Gautam, T, Ou, L, Schmookler, B, Wang, Y, Adikaram, D, Ahmed, Z, Albataineh, H, Ali, SF, Aljawrneh, B, Allada, K, Allison, SL, Alsalmi, S, Androic, D, Aniol, K, Annand, J, Arrington, J, Atac, H, Averett, T, Gayoso, C Ayerbe, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Bhatt, H, Bhetuwal, D, Biswas, D, Brash, E, Bulumulla, D, Camacho, CM, Campbell, J, Camsonne, A, Carmignotto, M, Castellanos, J, Chen, C, Chen, J-P, Chetry, T, Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, JC, Dusa, S Covrig, Crowe, B, Danagoulian, S, Danley, T, Deconinck, W, Defurne, M, Desnault, C, Di, D, Dlamini, M, Duer, M, Duran, B, Ent, R, Fanelli, C, Fuchey, E, Gal, C, Gaskell, D, Georges, F, Gilad, S, Glamazdin, O, Gnanvo, K, Gramolin, AV, Gray, VM, Gu, C, Habarakada, A, Hague, T, Hamad, G, Hamilton, D, Hamilton, K, Hansen, O, Hauenstein, F, Hernandez, AV, Henry, W, Higinbotham, DW, Holmstrom, T, Horn, T, Huang, Y, Huber, GM, Hyde, C, Ibrahim, H, Israel, N, Jen, C-M, Jin, K, Jones, M, Kabir, A, Karki, B, Keppel, C, Khachatryan, V, King, PM, Li, S, Li, W, Liu, H, Liu, J, Liyanage, AH, Mack, D, and Magee, J

Abstract

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q$^2$) up to 15.75~\gevsq. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q$^2$ and double the range over which a longitudinal/transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q$^2$ and attributed to hard two-photon exchange (TPE) effects, extending to 8~(GeV/c)$^2$ the range of Q$^2$ for which a discrepancy is established at $>$95\% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q$^2$.

Published
2021

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