Tue·Aug 24, 2021Tuesday·August 24, 2021

1. 01*

   The Physics of Neutrinoless Double Beta Decay: A Primer

   B.J.P. Jones🇺🇸

   Neutrinoless double beta decay is a hypothetical radioactive process which, if observed, would prove the neutrino to be a Majorana fermion: a particle that is its own antiparticle. In this lecture mini-series I discuss the physics of Majorana fermions and the connection between the nature of neutrino mass and neutrinoless double beta decay. We review Dirac and Majorana spinors, discuss methods of distinguishing between Majorana and Dirac fermions, and derive in outline the connection between neutrino mass and double beta decay rates. We conclude by briefly summarizing the experimental landscape and the challenges associated with searches for this elusive process.

   nucl-exhep-phnucl-th35 citations
2. 02*

   Measurement of the 91Zr(p,gamma)92mNb cross section motivated by type Ia supernova nucleosynthesis

   Gy. Gyürky🇭🇺 · Z. Halász🇭🇺 · G.G. Kiss🇭🇺 · T. Szücs🇩🇪 · R. Huszánk🇭🇺 · Zs. Török · Zs. Fülöp🇭🇺 · T. Rauscher🇨🇭 · C. Travaglio🇮🇹

   The synthesis of heavy, proton rich isotopes is a poorly understood astrophysical process. Thermonuclear (type Ia) supernova explosions are among the suggested sites and the abundance of some isotopes present in the early solar system may be used to test the models. 92Nb is such an isotope and one of the reactions playing a role in its synthesis is 91Zr(p,gamma)92Nb. As no experimental cross sections were available for this reaction so far, nucleosynthesis models had to solely rely on theoretical calculations. In the present work the cross section of 91Zr(p,gamma)92mNb has been measured at astrophysical energies by activation. The results excellently confirm the predictions of cross sections and reaction rates for 91Zr(p,gamma)92Nb, as used in astrophysical simulations.

   nucl-exastro-ph.SRPhysics(2021)·3 citations
3. 03*

   Measurement of global polarization of $\Lambda$ hyperons in Au+Au $\sqrt{s_{\mathrm{NN}}}$ = 7.2 GeV fixed target collisions at RHIC-STAR experiment

   Kosuke Okubo (for the STAR collaboration)🇯🇵

   In non-central nuclear collisions, the created matter should exhibit strong vorticity, which induces spin polarization. Global polarization is a good tool to investigate the dynamics of the system. Global polarization of $\Lambda$ and $\bar{\Lambda }$ hyperons has been measured at $\sqrt{s_{\mathrm{NN}}}$ = 2.4 GeV - 5.02 TeV in various experiments. We have measured the global polarization of $\Lambda$ hyperons in Au+Au collisions with fixed-target configuration at $\sqrt{s_{\mathrm{NN}}}$ = 7.2 GeV at RHIC-STAR experiment. The non-zero signal is observed and it follows the global trend of $\Lambda$ global polarization that increases towards lower collision energies. The global polarization is larger in more peripheral collisions but it does not show any significant rapidity dependence as well as transverse momentum dependence within uncertainties.

   nucl-exEPJ Web Conf.(2022)·11 citations
4. 04*

   Evidence of the triaxial structure of ${}^{129}$Xe at the Large Hadron Collider

   Benjamin Bally🇪🇸 · Michael Bender🇫🇷 · Giuliano Giacalone🇩🇪 · Vittorio Somà🇫🇷

   The interpretation of the emergent collective behaviour of atomic nuclei in terms of deformed intrinsic shapes [1] is at the heart of our understanding of the rich phenomenology of their structure, ranging from nuclear energy to astrophysical applications across a vast spectrum of energy scales. A new window onto the deformation of nuclei has been recently opened with the realization that nuclear collision experiments performed at high-energy colliders, such as the CERN Large Hadron Collider (LHC), enable experimenters to identify the relative orientation of the colliding ions in a way that magnifies the manifestations of their intrinsic deformation [2]. Here we apply this technique to LHC data on collisions of ${}^{129}$Xe nuclei [3-5] to exhibit the first evidence of non-axiality in the ground state of ions collided at high energy. We predict that the low-energy structure of ${}^{129}$Xe is triaxial (a spheroid with three unequal axes), and show that such deformation can be determined from high-energy data. This result demonstrates the unique capabilities of precision collider machines such as the LHC as new means to perform imaging of the collective structure of atomic nuclei.

   ↳ nucl-thhep-exhep-phnucl-exPRL(2022)·105 citations
5. 05*

   Exploring the string shoving model in PYTHIA8 for collective behaviors in $pp$ collisions

   Junlee Kim🇰🇷 · Eun-Joo Kim🇰🇷 · SuJeong Ji🇰🇷 · SangHoon Lim🇰🇷

   Two-particle correlations have been used to study property of a produced medium called Quark-Gluon Plasma (QGP) in relativistic heavy-ion collisions, and a long-range correlation among produced particles has been considered as a strong evidence of strongly interacting QGP. Strikingly, clear long-range correlations have been also observed in small collision systems like $pp$ and $p$+$A$ at a wide range of collision energies. A model introducing a repulsive force between flux tubes called string shoving can qualitatively describe the long-range near-side correlations in high multiplicity $pp$ collisions. This model implemented in the PYTHIA Monte Carlo event generator allows us to perform detailed study. In this work, a full data analysis to calculate associated yields and flow coefficients is performed with PYTHIA events, and the results are compared with experimental results. We find that the string shoving model overestimates long-range near-side correlations particularly in low multiplicity events. We also introduce a method to subtract such overestimated correlations in low multiplicity to have a more relevant comparison with the data.

   ↳ nucl-thnucl-exJ.Korean Phys.Soc.(2021)·9 citations
6. 06*

   Open Charm production in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV with Pythia event generator

   Randhir Singh🇮🇳

   Charm and beauty are heavy quarks with observed masses of 1.28 GeV/${\text{c}}^2$ and 4.18 GeV/${\text{c}}^2$ respectively. They are produced in initial hard scattering processes. Due to their small formation time ($\Delta t\sim 0.1fm/\text{c}$) as compared to the formation time of QGP ($\Delta t\sim 0.3fm/\text{c}$) at the LHC, they experience all the stages occuring during the time evolution of the hot and dense medium produced in heavy-ion collisions. Therefore, the measurement of open charm and beauty production allows probing QGP properties and investigating the color charge and mass dependence of the parton in-medium energy loss. Moreover, due to their large masses ($m_c,m_b\gg {\Lambda }_{QCD}$ ) their pp production cross-sections are calculable within the domain of perturbative QCD constituting an excellent test of pQCD calculations. The aim of this study is to understand the processes involved in the production of charm quarks through the productions of D${}^{+}$, D${}^0$, D${}_s^{+}$ and ${\Lambda }_c^{+}$ hadrons. Further to investigate the possibility of hadronization of the charm quarks, ratios like ${\Lambda }_c^{+}$/$D^{+}$, $D_s^{+}$/$D^{+}$, ${\Lambda }_c^{+}$/$D^0$ and $D_s^{+}$/$D^0$ are also measured. For the current analysis, the events are generated by using PYTHIA 8 for pp collisions at $\sqrt{s}$ = 13 TeV. PYTHIA 8 has proved to be quite successful in explaining the heavy-flavor particle production at the LHC energies.

   ↳ hep-exnucl-ex1 citation
7. 07*

   Pileup Correction on Higher-order Cumulants with Unfolding Approach

   Yu Zhang🇨🇳 · Yige Huang🇨🇳 · Toshihiro Nonaka🇯🇵 · Xiaofeng Luo🇨🇳

   Higher-order cumulants of conserved charge distributions are sensitive observables to probe the critical fluctuations near QCD critical point in heavy-ion collisions. Due to high interaction rate, pileup event can be one of the major sources of background in the measurements of higher-order cumulants. In this paper, we studied the effects of pileup events on higher-order cumulants of proton multiplicity distributions using UrQMD model. It is found that the proposed pileup correction fails if the correction parameters are determined by the Glauber fitting of charged particle multiplicities, which is usually done in the real heavy-ion experiment. To address this, we propose a model independent unfolding approach to determine the parameters in the pileup correction. This approach can be applied in the pileup correction for the future measurement of higher-order cumulants in heavy-ion collision experiment.

   ↳ physics.data-anhep-exhep-phnucl-ex+1Nucl.Instrum.Meth.A(2022)·13 citations
8. 08*

   Recent progress on few-body hypernuclei

   Avraham Gal🇮🇱

   Few-body $\Lambda$ hypernuclei provide valuable information towards understanding strange matter. Recent experimental progress by the STAR Collaboration at the RHIC facility and by the ALICE Collaboration at the LHC has been matched by theoretical progress reviewed here: (i) lifetimes of the hypertriton ${}_{\Lambda }^3$H, ${}_{\Lambda }^3$n if particle-stable, ${}_{\Lambda }^4$H and ${}_{\Lambda }^4$He and their charge symmetry breaking, and (ii) the onset of $\Lambda \Lambda$ hypernuclear binding.

   ↳ nucl-thnucl-exEPJ Web Conf.(2022)·8 citations
9. 09*

   Characterization of a Spatially Resolved Multi-Element Laser Ablation Ion Source

   K. Murray🇨🇦 · C. Chambers🇨🇦 · D. Chen🇺🇸 · Z. Feng · J. Fraser · Y. Ito🇯🇵 · Y. Lan🇨🇦 · S. Mendez · M. Medina Peregrina🇨🇦 · H. Rasiwala🇨🇦 · L. Richez · N. Roy🇨🇦 and 5 other authors

   A laser ablation ion source (LAS) is a powerful tool by which diverse species of ions can be produced for mass spectrometer calibration, or surface study applications. It is necessary to frequently shift the laser position on the target to selectively ablate materials in a controlled manner, and to mitigate degradation of the target surface caused by ablation. An alternative to mounting the target onto a rotation wheel or $x-y$ translation stage, is to shift the laser position with a final reflection from a motorized kinematic mirror mount. Such a system has been developed, assembled and characterized with a two axis motorized mirror and various metal targets. In the system presented here, ions are ablated from the target surface and guided by a 90 degree quadrupole bender to a Faraday cup where the ion current is measured. Spatially resolved scans of the target are produced by actuating the mirror motors, thus moving the laser spot across the target, and performing synchronous measurements of the ion current to construct 2D images of a target surface which can be up to 50~mm in diameter. The spatial resolution of the system has been measured by scanning the interfaces between metals such as steel and niobium, where it was demonstrated that the LAS can selectively ablate an area of diameter $\approx$50 $\mu$m. This work informs the development of subsequent LAS systems, that are intended to serve as multi-element ion sources for commercial and custom-built time-of-flight mass spectrometers, or to selectively study surface specific regions of samples.

   ↳ physics.ins-detnucl-exInt.J.Mass Spectrometry(2022)·6 citations
10. 10*

    The MuX Project

    Frederik Wauters🇩🇪 · Andreas Knecht🇨🇭

    The \emph{muX} project is conducting a series of muonic X-ray measurements in medium- and high-Z nuclei at PSI, utilizing a high-purity germanium detector array, in-beam muon detectors, and a modern digital data-acquisition system. A novel hydrogen target for muon transfer was developed, enabling measurements with as little as a few micrograms of target material. First measurements with radioactive Cm and Ra targets were conducted, aimed at determining their nuclear charge radii. These serve as important input for upcoming atomic parity violation experiments. The apparatus is also used to perform a feasibility study of an atomic parity violation experiment with the $2s-1s$ muonic X-ray transition. In addition, the setup has been made available for a wider range of nuclear, particle, and solid-state physics measurements.

    ↳ physics.ins-detnucl-exSciPost Phys.Proc.(2021)·18 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.