Fri·Dec 10, 2021Friday·December 10, 2021

1. 01*

   Spin alignment measurement of vector mesons produced in high energy collisions

   Bedangadas Mohanty🇮🇳 · Sourav Kundu🇨🇭 · Subhash Singha🇨🇳 · Ranbir Singh🇮🇳

   This review covers the recent experimental development on spin alignment measurements of $K^{\ast 0}$ and $\varphi$ vector mesons in heavy-ion and pp collisions at RHIC and LHC energies. Measurements in $e^{+}{e}^{-}$ collisions at LEP energies are also discussed. Spin alignment of vector mesons are studied by measuring the second diagonal element ${\rho }_{00}$ of spin density matrix. The ${\rho }_{00}$ is obtained by measuring the angular distribution of vector meson decay daughter with respect to the quantization axis in vector meson rest frame. Measured ${\rho }_{00}$ values for vector mesons are found to be larger than 1/3 at high momentum in $e^{+}{e}^{-}$ collisions at LEP energies, suggesting the preferential production of vector meson with helicity zero state from the fragmentation process. The ${\rho }_{00}$ values are found to be smaller than 1/3 (${\rho }_{00}$ = 1/3 implies no spin alignment) for $K^{\ast 0}$ and $\varphi$ vector mesons at low transverse momentum in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. This observations are qualitatively consistent with the expectation from models which attribute the spin alignment effect due to polarization of quarks in the presence of large initial angular momentum in non-central heavy-ion collisions and its subsequent hadronization by the process of recombination. No significant spin alignment effect is observed for $K_S^0$ (spin = 0) in mid-central Pb--Pb collisions and for vector mesons in pp collisions. However, the preliminary results of ${\rho }_{00}$ for $\varphi$ mesons are larger than 1/3 at intermediate $p_{\mathrm{T}}$ in Au--Au collisions at RHIC energies and can be attributed to the presence of $\varphi$ meson field. Although there is evidence of spin alignment effect of vector mesons in heavy-ion collisions but the measured effect is surprisingly larger in context of hyperon polarization. Therefore these results will trigger further theoretical study.

   nucl-exMod.Phys.Lett.A(2021)·30 citations
2. 02*

   Sympathetic cooling schemes for separately trapped ions coupled via image currents

   C. Will🇩🇪 · M. Bohman🇩🇪 · T. Driscoll🇺🇸 · M. Wiesinger🇩🇪 · F. Abbass🇩🇪 · M. J. Borchert🇯🇵 · J. A. Devlin🇯🇵 · S. Erlewein🇯🇵 · M. Fleck🇯🇵 · B. Latacz🇯🇵 · R. Moller🇩🇪 · A. Mooser🇩🇪 and 9 other authors

   Cooling of particles to mK-temperatures is essential for a variety of experiments with trapped charged particles. However, many species of interest lack suitable electronic transitions for direct laser cooling. We study theoretically the remote sympathetic cooling of a single proton with laser-cooled ${}^9$Be${}^{+}$ in a double-Penning-trap system. We investigate three different cooling schemes and find, based on analytical calculations and numerical simulations, that two of them are capable of achieving proton temperatures of about 10 mK with cooling times on the order of 10 s. In contrast, established methods such as feedback-enhanced resistive cooling with image-current detectors are limited to about 1 K in 100 s. Since the studied techniques are applicable to any trapped charged particle and allow spatial separation between the target ion and the cooling species, they enable a variety of precision measurements based on trapped charged particles to be performed at improved sampling rates and with reduced systematic uncertainties.

   ↳ physics.atom-phnucl-exNew J.Phys.(2022)·17 citations
3. 03*

   Revisiting NLO QCD corrections to total inclusive J/psi and Upsilon photoproduction cross sections in lepton-proton collisions

   Alice Colpani Serri🇫🇷 · Yu Feng🇨🇳 · Carlo Flore🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Melih A. Ozcelik🇫🇷 · Hua-Sheng Shao🇫🇷 · Yelyzaveta Yedelkina🇫🇷

   We revisit inclusive J/psi and Upsilon photoproduction at lepton-hadron colliders, namely in the limit when the exchanged photon is quasi real. Our computation includes the next-to-leading-order (NLO) alpha_s corrections to the leading-order contributions in v. Similarly to the case of NLO charmonium-hadroproduction processes, the resulting cross sections obtained in the MS-bar factorisation scheme are sometimes found to be negative. We show that the scale-fixing criteria which we derived in a previous study of eta(c) production successfully solves this problem from the EicC all the way up to the FCC-eh energies. We then elaborate on how to study a scale uncertainty akin to that derived by scale variations when one fixes a scale. In turn, we investigate where both J/psi and Upsilon photoproduction could be used to improve our knowledge of gluon content of the proton at scales as low as a couple of GeV.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2022)·33 citations
4. 04*

   Use of Bayesian Optimization to Understand the Structure of Nuclei

   J. Hooker🇺🇸 · J. Kovoor · K.L. Jones · R. Kanungo🇨🇦 · M. Alcorta · J. Allen🇺🇸 · C. Andreoiu · L. Atar🇩🇪 · D.W. Bardayan🇺🇸 · S.S. Bhattacharjee🇨🇦 · D. Blankstein · C. Burbadge🇨🇦 and 32 other authors

   Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a ${}^{12}$Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the ${}^{12}$C(d,p) reaction to well-known states in ${}^{13}$C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for ${}^{13}$Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in ${}^{13}$C were extracted to better than 90 keV, paving a way for extracting information on ${}^{13}$Be.

   ↳ physics.comp-phnucl-exNucl.Instrum.Meth.B(2022)·4 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.