Tue·Dec 21, 2021Tuesday·December 21, 2021

1. 01*

   Physics Beyond the Standard Model with the J-PET detector

   Elena Perez del Rio (for the J-PET Collaboration)🇵🇱

   The Positronium (Ps) system, a bound state of an electron and a positron, is suitable for testing the predictions of quantum electrodynamics (QED), since its properties can be perturbatively calculated to high accuracy and, unlike the hydrogen system, is not affected by the finite size or QCD effects at the current experimental precision level. This makes the Ps atom a good laboratory to test the Fundamental Symmetries of Physics and also search for new particles not included in the Standard Model (SM) of physics. On one hand, time reversal (T) and CP symmetry violation have never been observed in pure leptonic systems like the Ps atom, and the current experimental limits for CP and CPT violation in the decays of Ps is currently set at the level of 10^-3, while for C violation are at the level of 10^-7. These limits are still six and two orders of magnitude lower than the expected precision of 10^-9 set by photon-photon interactions. Secondly, experiments searching for invisible decays of the Ps triplet state, the ortho-Positronium (o-Ps), which mainly decays to three photons, are being conducted, since they are sensitive to new physics scenarios, e.g. Mirror Matter (MM), a suitable Dark Matter candidate, proposed to restore parity (P) violation. By performing a high precision measurement of the o-Ps lifetime, the accuracy of the present QED calculations can be tested and a search for the invisible decays of the o-Ps can be performed. These studies are conducted with the novel total-body Positron-Electron Tomography (PET) scanner at the JagiellonianUniversity.

   nucl-exphysics.ins-detPoS(2022)·1 citation
2. 02*

   Charmonia photo-production in ultra-peripheral and peripheral PbPb collisions with LHCb

   Weisong Duan (On behalf of the LHCb Collaboration)🇨🇳

   The LHCb recorded $\sim$ 210 $\mu b^{-1}$ integrated luminosity of PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV in 2018. With an increase of the luminosity by a factor of 20 compared to the previous 2015 PbPb dataset, precise measurements on photo-produced charmonia in ultra-peripheral collisions are now possible. Moreover, the great momentum resolution of the detector allows photo-produced $J/\psi$ in collisions with a nuclear overlap to be studied. This new type of probe is sensitive to the geometry of the collisions but also to the electromagnetic field of the Pb nuclei. In this contribution, we present the latest results on $J/\psi$ photo-production measured by LHCb in peripheral and ultra-peripheral PbPb collisions.

   nucl-exhep-ex1 citation
3. 03*

   Measurement of the {\alpha}-particle monopole transition form factor challenges theory: a low-energy puzzle for nuclear forces?

   S. Kegel · P. Achenbach · S. Bacca · N. Barnea · J. Bericic · D. Bosnar · L. Correa · M. O. Distler · A. Esser · H. Fonvieille · I. Friscic · M. Heilig and 21 other authors

   We perform a systematic study of the $\alpha$-particle excitation from its ground state $0_1^{+}$ to the $0_2^{+}$ resonance. The so-called monopole transition form factor is investigated via an electron scattering experiment in a broad $Q^2$-range (from $0.5$ to $5.0$ fm${}^{-2}$). The precision of the new data dramatically superseeds that of older sets of data, each covering only a portion of the $Q^2$-range. The new data allow the determination of two coefficients in a low-momentum expansion leading to a new puzzle. By confronting experiment to state-of-the-art theoretical calculations we observe that modern nuclear forces, including those derived within chiral effective field theory which are well tested on a variety of observables, fail to reproduce the excitation of the $\alpha$-particle.

   nucl-exnucl-thPRL(2023)·28 citations
4. 04*

   Study of the Isomeric State in ${}^{16}$N Using the ${}^{16}$N${}^{g,m}$($d$,${}^3$He) Reaction

   T. L. Tang🇺🇸 · C. R. Hoffman🇺🇸 · B. P. Kay🇺🇸 · I. A. Tolstukhin🇺🇸 · S. Almaraz-Calderon · B. W. Asher · M. L. Avila🇺🇸 · Y. Ayyad🇪🇸 · K. W. Brown🇺🇸 · D. Bazin🇺🇸 · J. Chen🇺🇸 · K. A. Chipps🇺🇸 and 10 other authors

   The isomeric state of ${}^{16}$N was studied using the ${}^{16}$N${}^{g,m}$($d$,${}^3$He)~proton-removal reactions at \mbox{11.8~MeV/$u$} in inverse kinematics. The ${}^{16}$N beam, of which 24% was in the isomeric state, was produced using the ATLAS in-fight facility and delivered to the HELIOS spectrometer, which was used to analyze the ${}^3$He ions from the ($d$,${}^3$He) reactions. The simultaneous measurement of reactions on both the ground and isomeric states, reduced the systematic uncertainties from the experiment and in the analysis. A direct and reliable comparison of the relative spectroscopic factors was made based on a Distorted-Wave Born Approximation approach. The experimental results suggest that the isomeric state of ${}^{16}$N is an excited neutron-halo state. The results can be understood through calculations using a Woods-Saxon potential model, which captures the effects of weak-binding.

   nucl-exnucl-thPRC(2022)·2 citations
5. 05*

   Specific heat and its high-order moments in relativistic heavy-ion collisions from a multiphase transport model

   Ru-Xin Cao🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳

   Energy dependence of specific heat extracted from temperature fluctuation of Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 GeV to 200 GeV was investigated by using a multiphase transport (AMPT) model. The results were compared with those from other models and some differences at low $\sqrt{s_{NN}}$ were found. To explain the above differences and describe the properties of the hot dense matter at low $\sqrt{s_{NN}}$, a new quantity $C_v^{\ast }$ was derived for describing specific heat in heavy-ion collisions. It was found that, by using $C_v^{\ast }$ together with its high order moments (skewness and kurtosis), thermal properties of the hot dense matter can be described and different thermal properties with or without parton process can be clearly distinguished. The proposed observable provides a way to learn the property of QCD matter % phase transition %along with critical point in heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exPRC(2022)·13 citations
6. 06*

   Short range correlations in the extended quantum molecular dynamics model

   Lei Shen · Bo-Son Huang🇨🇳 · Yu-Gang Ma🇨🇳

   Short-range potential has been added into an extended quantum molecular dynamics (EQMD) model. The RMS radius, binding energy and momentum distribution of ${}^{12}$C with different initial structures and short-range potential parameters have been checked. The separation energy of ${}^{12}$C(p,2p)${}^{11}$B reaction is calculated and compared with the experimental data, it indicates that our modified EQMD model can be taken as a reliable tool for studying proton pair knock-out reaction. Furthermore, the short range correlation effects on emission time and momentum spectrum of two protons are discussed. Finally, the momentum correlation function of the emitted proton pair is calculated by the Lednicky and Lyuboshitz's analytical method. The result explains that short-range repulsion causes high momentum tail and weakens the momentum correlation function.

   ↳ nucl-thnucl-exPRC(2022)·17 citations
7. 07*

   BoxScore -- A real-time beam-diagnosis program for CAEN digitizer x730 series

   T. L. Tang🇺🇸

   BoxScore is a real-time beam diagnosis and monitoring program for the CAEN x730 series digitizer that was developed for the ATLAS in-flight facility at Argonne National Laboratory. The CAEN x730 series digitizer, with built-in Digital Pulse Processing for the Pulse-Height-Analysis, can analyze the input signal in real-time using a trapezoidal filter. BoxScore reads the digitizer's buffer directly, builds and saves events to local files, plots filled histograms for particle identification, and outputs the rates of selected isotopes every second. Implementation of BoxScore has shortened the time needed for in-flight beam-tuning and has potential applications for other nuclear physics experiments.

   ↳ physics.ins-detnucl-exphysics.acc-phNucl.Instrum.Meth.A(2022)·1 citation

* 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.