Comment on "Erratum: Negative-parity high-spin states and a possible magnetic rotation band in 135 59 Pr 76 [Phys. Rev. C 92, 054325 (2015)]"
CComment on “Erratum: Negative-parity high-spin states and a possible magneticrotation band in Pr [Phys. Rev. C 92, 054325 (2015)]” S. Guo
1, 2 and C. M. Petrache Key Laboratory of High Precision Nuclear Spectroscopy and Center for Nuclear Matter Science,Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China School of Nuclear Science and Technology, University of ChineseAcademy of Science, Beijing 100049, People’s Republic of China Centre de Sciences Nucl´eaires et Sciences de la Mati`ere, CNRS/IN2P3,Universit´e Paris-Saclay, Bˆat. 104-108, 91405 Orsay, France (Dated:)In [Ritika Garg et al., Phys. Rev. C 100, 069901(E) (2019)] the experimental results on the polar-ization asysmetry were revised due to a claimed change of the geometry asymmetry. However, therevised results can not be reproduced as claimed in the erratum by simply changing the geometryasymmetry in extracting the polarization asymmetry, without re-extracting the polarization asym-metry from the original experimental data. It is possible that the quoted errors were significantlyunderestimated.
PACS numbers: 21.10.Re, 21.60.Ev, 23.20.Lv, 27.60.+j
In Ref. [1] a series of results on polarization asymme-try (∆) were reported. Among them the results of twotransitions, with energies at 747.5 and 813.3 keV, were incontradiction with those reported in Ref. [2]. This con-tradiction gained wide attention since the reported E2dominating character on these two transitions providedthe critical experimental proof for the first wobbling bandout of A ∼
160 mass region. However, the results in Ref.[1] published six month later reported a negative polar-ization assymetry which induces a dominant M1 char-acter of the two transitions contradicting the wobblinginterpretation. Note that the two contradicting resultswere obtained using the same reaction ( O + Sb ) andthe same detectors array (INGA).
400 600 10000.90.9511.051.1 G e o m e t r y a s y mm e t r y Energy (keV)Δ old (used) Δ o l d ( c a l i b r a t e d ) Δ new FIG. 1. (Color online) Geometry asymmetry as functions oftransition energy.
Recently, this contradiction has been resolved by thecommented erratum, which revised the results to be incoincidence with Ref. [2]. The revision on the results wasexplained as due to the change of the geometry asymme-try ( a ), which is plotted in Fig. 1. The old a values werecalibrated as an increasing line with a considerable slope, though the coefficient a = 6 . × − was consideredto be insignificance and neglected. On the contrary, thenew a values were claimed to be energy dependent, buta small coefficient a = 1 . × − made them quiteflat. Therefore both the old and the new actually used a values are close to constants, with a nearly fixed differ-ence ( ∼ .
08) between them. Comparing to the error barof the old a values (0.06), the difference is quite large.However, the origin of the difference was not explained.In the commented erratum, the new results wereclaimed to be determined by using the new geometryasymmetry, without mentioning any change in the orig-inal data. There is a simple relation (see Eq. 1, whichis quoted from Ref. [1], Eq. 2) among the polarizationaymmetry (∆), geometry asymmetry ( a ) and the ratio(R) between the number of perpendicular ( N ⊥ ) and thatof parallel ( N (cid:107) ) scattering.∆ = aN ⊥ − N (cid:107) aN ⊥ + N (cid:107) (1)According to Eq. 1, R can be deduced when the polar-ization aymmetry and geometry asymmetry are known: R = N ⊥ N (cid:107) = 1 + ∆1 − ∆ /a (2)Using Eq. 2, the old and new R values have beendeduced and listed in Table I, which are expected tokeep unchanged when only the geometry asymmetry ischanged. The errors are not deduced since the error onthe new geometry asymmetry was not reported. Surpris-ingly, significant change has been found for all transi-tions. For 747.5- and 813.3-keV transitions, the R valueswere modified from 0.973 and 0.717 to 1.048 and 1.069,respectively. To make it clear how the new ∆ results a r X i v : . [ nu c l - e x ] J u l TABLE I. γ -ray energy, polarization asymmetry (∆) ratiosand deduced ratios between the counts of parallel and per-pendicular scattering (R). E γ (keV) ∆ old ∆ new ∆ deduced R old R new would be without inducing any change on R, we use Eq.3 which is deduced from Eqs. 1 and 2. The deduced newR values are listed in Table I and plotted in Fig. 2.∆ new = a new (1 + ∆ old ) − a old (1 − ∆ old ) a new (1 + ∆ old ) + a old (1 − ∆ old ) (3)The deduced ∆ values for the 747.5- and 813.3-keVtransitions obtained by maintaining the R values un-changed are -0.007 and -0.159, respectively. The smallnegative values still indicate the M1 dominated charac-ters. In Fig. 2 it can be seen that the ∆ deduced values arelarger than the ∆ old values by approximately constantdifference ( ∼ new − ∆ old = ( a new − a old ) + ( a new − a old )∆ old ( a new + a old ) + ( a new − a old )∆ old (4)Where ∆ old ∼ a new ∼
1, and a old ∼
1, it approxi-mately equal to: ∆ new − ∆ old ∼ ( a new − a old )2 (5)Considering that the new ∆ values published in theerratum and the old ∆ values published in Ref. [1] arealmost randomly changed (see Fig. 2), they cannot beachieved by simply changing the geometry asymmetry. -0.4-0.200.20.4 400 600 1000800 1200 14002000 P o l a r i za ti on a s y mm e t r y Energy (keV) oldnewdeduced
FIG. 2. (Color online) The old and new polarization asym-metry values, in comparison with the deduced ones assumingonly the geometry asymmetry is changed.
Assuming that no subjective fault is involved, it is pos-sible that the R ratios for the new results were deducedagain individually from the original data, not by scal-ing the former ratios by the new geometry asymmetry.In that case, the errors are significantly underestimated,since the deduced ∆ values using the former original datadiffer from the new ones too much comparing to the er-rors. That means, by properly taking into account thestatistical and background subtraction induced errors, itis impossible to judge if the M1/E2 characters of the747.5- and 813.3-keV transitions are M1 or E2 domi-nated, based on the polarization assymetry deduced fromexperimental data with statistics at the level of that re-ported in the work of Ref. [1]. [1] R. Garg, S. Kumar, M. Saxena, S. Goyal, D. Siwal, andS. Kalkal et al. , Phys. Rev. C , 054325 (2015).[2] J. T. Matta, U. Garg, W. Li, S. Frauendorf, A. D.Ayangeakaa, and D. Patel et al. , Phys. Rev. Lett.114