Tue·Jul 2, 2019Tuesday·July 2, 2019

1. 01*

   Direct observation of proton emission in 11Be

   Y. Ayyad🇯🇵 · B. Olaizola🇨🇦 · W. Mittig🇺🇸 · G. Potel🇺🇸 · V. Zelevinsky🇺🇸 · M. Horoi🇺🇸 · S. Beceiro-Novo🇺🇸 · M. Alcorta🇪🇸 · C. Andreoiu🇨🇦 · T. Ahn🇺🇸 · M. Anholm · L. Atar🇩🇪 and 21 other authors

   The elusive ${\beta }^{-}{\text{p}}^{+}$ decay was observed in ${}^{11}$Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber (pAT-TPC) in an experiment performed at ISAC-TRIUMF. The measured ${\beta }^{-}{\text{p}}^{+}$ branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in ${}^{11}$B above the proton separation energy.

   nucl-exPRL(2019)·54 citations
2. 02*

   Measurement of the beam-helicity asymmetry in photoproduction of ${\pi }^0\eta$ pairs on carbon, aluminum, and lead

   V. Sokhoyan🇩🇪 · S. Prakhov🇩🇪 · A. Fix🇷🇺 · S. Abt🇨🇭 · P. Achenbach🇩🇪 · P. Adlarson🇩🇪 · F. Afzal🇩🇪 · P. Aguar-Bartolomé🇩🇪 · Z. Ahmed🇨🇦 · K. Altangerel🇩🇪 · J. R. M. Annand🇬🇧 · H. J. Arends🇩🇪 and 79 other authors

   The beam-helicity asymmetry was measured, for the first time, in photoproduction of ${\pi }^0\eta$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for ${\pi }^0\eta$ pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the $D_{33}$ partial wave with the $\eta \Delta (1232)$ intermediate state.

   nucl-exPLB(2020)·5 citations
3. 03*

   Estimation of fusion-evaporation cross sections by artificial neural networks

   Serkan Akkoyun

   Accurate determination of fusion-evaporation reaction cross section is important in experimental nuclear physics studies. In this study, by using artificial neural network (ANN) method, we have estimated the cross section values for different reactions. The related root mean square errors have been obtained as 18.5 and 110.4mb for training and test data which correspond to 1.8% and 10.5% deviations from the experimental values, respectively.This order of deviations is lower than the cross section value from most common theoretical calculations. The results of this study indicate that ANN method is capable for the estimation of cross section values of fusion-evaporation reactions.

   nucl-exNucl.Instrum.Meth.B(2020)·19 citations
4. 04*

   PCN calculations for Z=111 to Z=118

   Walter Loveland · Liangyu Yao

   In previous publications, we presented evidence for the importance of spin in determining capture and evaporation residue cross sections in the synthesis of heavy nuclei. We extend the previous calculations which dealt with nuclei where ZCN is less than 110 to the region of ZCN = 111-118. We deduce a new systematics of the fusion probability for these reactions

   nucl-exnucl-thSpringer Proc.Phys.(2021)·1 citation
5. 05*

   Confinement in Nuclei and the Expanding Proton

   Gerald A. Miller🇺🇸

   High-precision knowledge of electromagnetic form factors of nuclei is a subject of much current experimental and theoretical activity in nuclear and atomic physics. Such precision mandates that effects of the non-zero spatial extent of the constituent nucleons be handled in a manner that goes beyond the usual impulse approximation. A series of simple, Poincare-invariant, composite-proton models that respect the Ward-Takahashi identity and in which quarks are confined are used to study the validity of this approximation. The result of all of the models is a general theorem showing that medium modification of proton structure must occur. Combining this result with lattice QCD calculations leads to a conclusion that a bound proton must be larger than a free one.

   ↳ nucl-thhep-phnucl-exPRL(2019)·14 citations
6. 06*

   An Improved Evaluation of the Neutron Background in the PandaX-II Experiment

   Qiuhong Wang🇨🇳 · Abdusalam Abdukerim🇨🇳 · Wei Chen🇨🇳 · Xun Chen🇨🇳 · Yunhua Chen🇨🇳 · Xiangyi Cui🇨🇳 · Yingjie Fan🇨🇳 · Deqing Fang🇨🇳 · Changbo Fu🇨🇳 · Lisheng Geng🇨🇳 · Karl Giboni🇨🇳 · Franco Giuliani🇨🇳 and 51 other authors

   In dark matter direct detection experiments, neutron is a serious source of background, which can mimic the dark matter-nucleus scattering signals. In this paper, we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach. Instead of fully relying on the Monte Carlo simulation, the overall neutron background is determined from the neutron-induced high energy signals in the data. In addition, the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator, where the correlated emission of neutron(s) and $\gamma$(s) in the ($\alpha$, n) reactions and spontaneous fissions is taken into consideration. With this method, the neutron backgrounds in the Run 9 (26-ton-day) and Run 10 (28-ton-day) data sets of PandaX-II are estimated to be 0.66$\pm$0.24 and 0.47$\pm$0.25 events, respectively.

   ↳ hep-exnucl-exphysics.ins-detSCPMA(2020)·16 citations
7. 07*

   An insight into strangeness with $\varphi$(1020) production in small to large collision systems with ALICE at the LHC

   Sushanta Tripathy (for the ALICE collaboration)🇮🇳

   Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects in the hadronic phase of heavy-ion collisions. As the $\varphi$ meson has a longer lifetime compared to other resonances, it is expected that its production will not be affected by regeneration and re-scattering processes. Measurements in small collision systems such as proton-proton (pp) collisions provide a necessary baseline for heavy-ion data and help to tune pQCD inspired event generators. Given that the $\varphi$ is a bound state of strange-antistrange quark pair (s$\bar{\mathrm{s}}$), measurements of its production can contribute to the study of strangeness production. Recent results obtained by using the ALICE detector show that although $\varphi$ has zero net strangeness content, it behaves like a particle with open strangeness in small collision systems and the experimental results agree with thermal model predictions in large systems. The production mechanism of $\varphi$ is yet to be understood. We report on measurements with the ALICE detector at the LHC of $\varphi$ meson production in pp, p--Pb, Xe--Xe and Pb--Pb collisions. These results are reported for minimum bias event samples and as a function of the charged particle multiplicity or centrality. The results include the transverse momentum ($p_{\mathrm{T}}$) distributions of $\varphi$ as well as the $⟨p_{\mathrm{T}}⟩$ and particle yield ratios. The $\varphi$ effective strangeness will be discussed in relation to descriptions of its production mechanism, such as strangeness canonical suppression, non-equilibrium production of strange quarks and thermal models.

   ↳ hep-exnucl-exSpringer Proc.Phys.(2021)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.