Nuclear Experiment

This note points out an apparent error in the publication Phys.~Lett.~B {\bf 809} (2020) 135771 by Magdy, Nie, Ma, and Lacey.

In [Ritika Garg et al., Phys. Rev. C 100, 069901(E) (2019)] the experimental results on the polarization asysmetry were revised due to a claimed change of the geometry asymmetry. However, the revised results can not be reproduced as claimed in the erratum by simply changing the geometry asymmetry in extracting the polarization asymmetry, without re-extracting the polarization asymmetry from the original experimental data. It is possible that the quoted errors were significantly underestimated.

In [S. Nandi et al., Phys. Rev. Lett. 125, 132501 (2020)] two transverse wobbling bands were reported in 183 Au. The critical experimental proof for this assignment is the E2 dominated linking transitions between the wobbling and normal bands, which are supported by fitting the measured DCO ratio and polarization results. However, the uncertainties are significantly underestimated according to an analysis on the statistical error. With reasonable error, the mixing ratios cannot be exclusively decided, and the M1 dominated character cannot be excluded, indicating that the wobbling assignment is still questionable.

In [S. Biswas et al., Eur. Phys. J. A 55, 159 (2019)] a longitudinal wobbling band was reported in 133 La. The critical experimental proof for this assignment is the E2 dominated linking transitions between the wobbling and normal bands, which are supported by angular distribution and linear polarization measurements. However, severe problems are found in the reported experimental information, indicating that the assignment of wobbling band was not firmly established.

We comment on a recent paper by the LEPS2/BGOegg Collaboration [Phys. Rev. Lett. 124, 202501 (2020), arXiv:2005.03449].

We show that recently reported radioactive decay data support an earlier observation of an unexpected signal associated with the GW170817 binary neutron star inspiral.

In [J. T. Matta et al., Phys. Rev. Lett. 114, 082501 (2015)] a transverse wobbling band was reported in 135 Pr. The critical experimental proof for this assignment is the E2 dominated linking transitions between the wobbling and normal bands, which are supported by two experiments performed with Gammasphere and INGA. However, the M1 dominated character cannot be excluded based on the reported experimental information, indicating that the wobbling assignment is still questionable.

The article recently published by M. Gai et al. claims to reach conclusions from a collaborative experiment dedicated to the study of the 7Be(n,alpha) reaction. These claims were published with no authorization from key collaborators, including a PI of the experiment. The Authors of the present Comment reject the conclusions of M. Gai et et al. and condemn the scientific and ethical misconduct involved in their publication. A formal Comment, similarly expressing the Authors' rejection of these conclusions was submitted to EPJ Web of Conferences who published the above article.

We present first measurements of the double ratio of the polarization transfer components ( P ′ x / P ′ z ) p /( P ′ x / P ′ z ) s for knock-out protons from s and p shells in 12 C measured by the 12 C( e → , e ′ p → ) reaction in quasi-elastic kinematics. The data are compared to theoretical predictions in relativistic distorted-wave impulse approximation. Our results show that differences between s - and p -shell protons, observed when compared at the same initial momentum (missing momentum) largely disappear when the comparison is done at the same proton virtuality. We observe no density-dependent medium modifications for protons from s and p shells with the same virtuality in spite of the large differences in the respective nuclear densities.

The STAR Collaboration reports a measurement of the transverse single-spin asymmetries, A N , for neutral pions produced in polarized proton collisions with protons ( pp ), with aluminum nuclei ( pAl ) and with gold nuclei ( pAu ) at a nucleon-nucleon center-of-mass energy of 200 GeV. Neutral pions are observed in the forward direction relative to the transversely polarized proton beam, in the pseudo-rapidity region 2.7<η<3.8 . Results are presented for π 0 s observed in the STAR FMS electromagnetic calorimeter in narrow Feynman x ( x F ) and transverse momentum ( p T ) bins, spanning the range 0.17< x F <0.81 and 1.7< p T <6.0 GeV/ c . For fixed x F <0.47 , the asymmetries are found to rise with increasing transverse momentum. For larger x F , the asymmetry flattens or falls as p T increases. Parametrizing the ratio r(A)≡ A N (pA)/ A N (pp)= A P over the kinematic range, the ratio r(A) is found to depend only weakly on A , with ⟨P⟩=−0.027±0.005 . No significant difference in P is observed between the low- p T region, p T <2.5 GeV/ c , where gluon saturation effects may play a role, and the high- p T region, p T >2.5 GeV/ c . It is further observed that the value of A N is significantly larger for events with a large- p T isolated π 0 than for events with a non-isolated π 0 accompanied by additional jet-like fragments. The nuclear dependence r(A) is similar for isolated and non-isolated π 0 events.