arXiv subjects

H. W. Grießhammer

Publications and source records attributed to H. W. Grießhammer.

4 recordsLinked to original sources

arXiv2026

First Measurement of Compton Scattering on $^3\text{He}$ at HI$γ$S

The world's first Compton scattering measurements on a $^3$He target were performed to probe neutron electromagnetic polarizabilities. Differential cross sections were measured at laboratory angles of $40^\circ$, $55^\circ$, $90^\circ$, $115^\circ$, $150^\circ$, using circularly polarized, quasi-monoenergetic photon beams at weighted mean energy values of 61.5 and 97.1 MeV from the High Intensity $γ$-ray Source at the Triangle Universities Nuclear Laboratory. Comparisons with chiral effective field theory show good agreement at 97.1 MeV but over-prediction at 61.5 MeV, motivating further theoretical development.

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arXiv2022

Proton Compton Scattering from Linearly Polarized Gamma Rays

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of $55^\circ$, $90^\circ$, and $125^\circ$ in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4\,MeV (81.3\,MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives $α_{E1}^p = 13.8\pm1.2_{\rm stat}\pm0.1_{\rm BSR}\pm0.3_{\rm theo}, β_{M1}^p = 0.2\mp1.2_{\rm stat}\pm0.1_{\rm BSR}\mp0.3_{\rm theo}$ in units of 10$^{-4}$\, fm$^3$.

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arXiv2020

Compton scattering from $^4$He at the TUNL HI$γ$S facility

Differential cross sections for elastic Compton scattering from $^4$He have been measured with high statistical precision at the High Intensity $γ$-ray Source at laboratory scattering angles of $55^\circ$, $90^\circ$, and $125^\circ$ 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 $^4$He to fully interpret the data.

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arXiv2014

New Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data --- and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world dataset. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using Chiral Effective Field Theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world dataset. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities and combining them with a recent result for the proton, we obtain the neutron polarizabilities as α_n = [11.55 +/- 1.25(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and β_n = [3.65 -/+ 1.25(stat) +/- 0.2(BSR) -/+ 0.8(th)] X 10^{-4} fm3, with χ^2 = 45.2 for 44 degrees of freedom.

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