First Determination of the Weak Charge of the Proton
The Q[subscript weak] experiment has measured the parity-violating asymmetry in e⃗ p elastic scattering at Q[superscript 2] = 0.025 (GeV/c)[superscript 2], employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the exper...
| Main Authors: | , , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
American Physical Society
2014
|
| Online Access: | http://hdl.handle.net/1721.1/84934 https://orcid.org/0000-0001-5360-2804 https://orcid.org/0000-0003-3088-6060 |
| _version_ | 1826191081923936256 |
|---|---|
| author | Balewski, Jan T. Guo, Fang Rajotte, Jean-Francois Kowalski, Stanley B |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Balewski, Jan T. Guo, Fang Rajotte, Jean-Francois Kowalski, Stanley B |
| author_sort | Balewski, Jan T. |
| collection | MIT |
| description | The Q[subscript weak] experiment has measured the parity-violating asymmetry in e⃗ p elastic scattering at Q[superscript 2] = 0.025 (GeV/c)[superscript 2], employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the experiment’s commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A[subscript ep]= −279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in e⃗ p scattering. The small Q[superscript 2] of this experiment has made possible the first determination of the weak charge of the proton Q[p over W] by incorporating earlier parity-violating electron scattering (PVES) data at higher Q[superscript 2] to constrain hadronic corrections. The value of Q[p over W] obtained in this way is Q[p over W](PVES) = 0.064 ± 0.012, which is in good agreement with the standard model prediction of Q[p over W](SM) = 0.0710 ± 0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES + APV analysis reveals the neutron’s weak charge to be Q[n over W](PVES + APV) = −0.975 ± 0.010. |
| first_indexed | 2024-09-23T08:49:54Z |
| format | Article |
| id | mit-1721.1/84934 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:49:54Z |
| publishDate | 2014 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/849342023-02-26T06:00:23Z First Determination of the Weak Charge of the Proton Balewski, Jan T. Guo, Fang Rajotte, Jean-Francois Kowalski, Stanley B Massachusetts Institute of Technology. Department of Physics Massachusetts Institute of Technology. Laboratory for Nuclear Science Balewski, Jan T. Guo, Fang Kowalski, Stanley B. Rajotte, Jean-Francois The Q[subscript weak] experiment has measured the parity-violating asymmetry in e⃗ p elastic scattering at Q[superscript 2] = 0.025 (GeV/c)[superscript 2], employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the experiment’s commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A[subscript ep]= −279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in e⃗ p scattering. The small Q[superscript 2] of this experiment has made possible the first determination of the weak charge of the proton Q[p over W] by incorporating earlier parity-violating electron scattering (PVES) data at higher Q[superscript 2] to constrain hadronic corrections. The value of Q[p over W] obtained in this way is Q[p over W](PVES) = 0.064 ± 0.012, which is in good agreement with the standard model prediction of Q[p over W](SM) = 0.0710 ± 0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES + APV analysis reveals the neutron’s weak charge to be Q[n over W](PVES + APV) = −0.975 ± 0.010. United States. Dept. of Energy (Contract DE-AC05-06OR23177) 2014-02-10T20:48:19Z 2014-02-10T20:48:19Z 2013-10 2013-07 Article http://purl.org/eprint/type/JournalArticle 0031-9007 1079-7114 http://hdl.handle.net/1721.1/84934 Androic, D., D. S. Armstrong, A. Asaturyan, T. Averett, J. Balewski, J. Beaufait, R. S. Beminiwattha, et al. “First Determination of the Weak Charge of the Proton.” Physical Review Letters 111, no. 14 (October 2013). © 2013 American Physical Society https://orcid.org/0000-0001-5360-2804 https://orcid.org/0000-0003-3088-6060 en_US http://dx.doi.org/10.1103/PhysRevLett.111.141803 Physical Review Letters Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Physical Society American Physical Society |
| spellingShingle | Balewski, Jan T. Guo, Fang Rajotte, Jean-Francois Kowalski, Stanley B First Determination of the Weak Charge of the Proton |
| title | First Determination of the Weak Charge of the Proton |
| title_full | First Determination of the Weak Charge of the Proton |
| title_fullStr | First Determination of the Weak Charge of the Proton |
| title_full_unstemmed | First Determination of the Weak Charge of the Proton |
| title_short | First Determination of the Weak Charge of the Proton |
| title_sort | first determination of the weak charge of the proton |
| url | http://hdl.handle.net/1721.1/84934 https://orcid.org/0000-0001-5360-2804 https://orcid.org/0000-0003-3088-6060 |
| work_keys_str_mv | AT balewskijant firstdeterminationoftheweakchargeoftheproton AT guofang firstdeterminationoftheweakchargeoftheproton AT rajottejeanfrancois firstdeterminationoftheweakchargeoftheproton AT kowalskistanleyb firstdeterminationoftheweakchargeoftheproton |