Professor Puckett awarded new three-year grant from the Department of Energy

Professor Puckett was recently awarded a new three-year grant from the US Department of Energy, Office of Science, Office of Nuclear Physics (topic area: Medium-Energy Nuclear Physics) to support our group’s efforts in the Super BigBite Spectrometer (SBS) Collaboration in Jefferson Lab’s Experimental Hall A. The research supported by the grant, titled “Three-dimensional structure of the nucleon”, includes measurements of nucleon electromagnetic form factors at large momentum transfers and single-spin asymmetries on a transversely polarized Helium-3 target. The figure below shows the projected results of the form factor part of the program.

Projected results from SBS form factor program
Projected results on nucleon electromagnetic form factors at large momentum transfers (Q^2) from the upcoming SBS program in Hall A at Jefferson Lab. These measurements are a major component of the research supported by the new DOE grant

Preprint of ECT* Diquark Workshop Proceedings submitted to PPNP

The manuscript of the proceedings paper from the September 2019 ECT* “Diquark Correlations” workshop in Trento, Italy has recently been submitted for publication to Progress in Particle and Nuclear Physics. The preprint of the paper can be found at the following link. Professor Puckett gave an invited talk at the workshop and wrote the section of the paper titled “Super BigBite Spectrometer Programme on High-Q2 Space-like Nucleon Form Factors”.

 

Two new experiments approved by Jefferson Lab Program Advisory Committee

Two new experiments using the Super BigBite Spectrometer (SBS) have been approved by the Jefferson Lab Program Advisory Committee (PAC) at its 48th meeting.

The goal of the first experiment (E12-20-010), with UConn postdoc Eric Fuchey as co-spokesperson and contact person, is to perform the first precise measurement of the so-called “Rosenbluth slope” in the elastic electron-neutron scattering cross section at a large momentum transfer, to determine whether there are significant contributions to this process beyond the dominant single-photon-exchange contribution, as is already well established for elastic electron-proton scattering. The PAC approved this experiment for two days of new beam time with a scientific rating of “A-“.

The slides from Dr. Fuchey’s PAC presentation can be found here

The goal of the second experiment (E12-20-008), with Professor Puckett as co-spokesperson and contact person, is to perform a first measurement of the polarization transfer observables in the photoproduction of charged pions in the reaction γ+n → π+p at high energies and wide scattering angles in the center-of-mass frame. These measurements can unambiguously test predictions based on the framework of Generalized Parton Distributions (GPDs). The PAC approved this experiment for two days of new beam time with a scientific rating of “B+”.

The slides from Prof. Puckett’s PAC presentation can be found here

Proton radius puzzle apparently resolved…

The PRAD collaboration recently published their results on very low Q2 electron-proton scattering in Hall B at Jefferson Lab, extracting a proton charge radius of rp = 0.831 ± 0.007 (stat) ± 0.012 (syst) fm, consistent with the precise extraction of this quantity from measurements of the Lamb shift in muonic hydrogen, first published in 2010.

Nature article

It appears that after nearly a decade of additional investigation, the “proton radius puzzle” that emerged after the original publication of the muonic hydrogen Lamb shift results has been more or less resolved in favor of the smaller proton charge radius of about 0.84 fm, as opposed to the pre-2010 consensus value of around 0.88 fm.

While our group was not directly involved in the measurement, we were very interested in the results, as we are focused on studying the same process (elastic electron-proton scattering) at very large values of Q2.

 

First paper from Tritium family of experiments in Hall A published

The first paper from the recently completed family of tritium target experiments in JLab’s Hall A is now published in Physics Letters B. The final published version of the paper can be found online at https://doi.org/10.1016/j.physletb.2019.134890

The INSPIRE-HEP database entry for the paper can be found at http://inspirehep.net/record/1720567

The paper reports the first measurement of the cross section ratios between Helium-3 and tritium for quasi-elastic (QE) proton knockout in electron scattering at large values of the missing momentum, in kinematics for which the contributions of non-QE reaction mechanisms are suppressed (large Q2, x > 1). The measured 3He/3H cross section ratios agree with state-of-the-art few-body nuclear theory calculations up to missing momenta of about 250 MeV/c, equivalent to the Fermi momentum, but exceed all available calculations by 20-50% for missing momenta above the Fermi momentum of these A = 3 mirror nuclei. The high-missing-momentum data are sensitive to the dynamics of short-range-correlated two-nucleon pairs that dominate the high-momentum tail of the nuclear wave-function.

Current and former group members including Prof. Puckett, Eric Fuchey, and Freddy Obrecht are co-authors on the publication, having contributed to the data taking for the tritium experiments in the form of shifts and/or run coordination.

PRL paper from experiment E04-108 becomes “famous paper” on INSPIRE

The 2010 publication of Professor Puckett’s doctoral dissertation research in Physical Review Letters recently became a “famous paper” (250-499 citations) in the INSPIRE High Energy Physics publication database.

The INSPIRE database entry for the paper can be found here.

The final published version of the paper at the Physical Review Online Archive (PROLA)

The recent, more detailed archival publication of the GEp-III and GEp-2gamma experiments.

Professor Puckett’s doctoral dissertation on which both papers are based.