Thu·Jun 17, 2021Thursday·June 17, 2021

1. 01*

   Neutron Spin Structure from e-3He Scattering with Double Spectator Tagging at the Electron-Ion Collider

   Ivica Friscic🇺🇸 · Dien Nguyen🇺🇸 · Jackson Pybus🇺🇸 · Alex Jentsch🇺🇸 · Efrain Segarra🇺🇸 · Mark Baker🇺🇸 · Or Hen🇺🇸 · Douglas Higinbotham🇺🇸 · Richard Milner🇺🇸 · Arun Tadepalli🇺🇸 · Zhoudunming Tu🇺🇸 · Jennifer Rittenhouse West🇺🇸

   The spin structure function of the neutron is traditionally determined by measuring the spin asymmetry of inclusive electron deep inelastic scattering (DIS) off polarized3He nuclei. In such experiments, nuclear effects can lead to large model dependencies in the interpretation of experimental data. Here we study the feasibility of suppressing such model dependencies by tagging both spectator protons in the process of DIS off neutrons in3He at the forthcoming Electron-Ion Collider (EIC). This allows reconstructing the momentum of the struck neutron to ensure it was nearly at rest in the initial state, thereby reducing sensitivity to nuclear corrections, and suppress contributions from electron DIS off protonsin3He. Using realistic accelerator and detector configurations, we find that the EIC can probe the neutron spin structure from xB of 0.003 to 0.651. We further find that the double spectator tagging method results in reduced uncertainties bya factor of 4 on the extracted neutron spin asymmetries over all kinematics, and by a factor of 10 in the low-xB region,thereby providing valuable insight to the spin and flavor structure of nucleons

   nucl-exhep-phPLB(2021)·16 citations
2. 02*

   ALICE Central Trigger System for LHC Run 3

   Jakub Kvapil🇬🇧 · Anju Bhasin🇮🇳 · Marek Bombara🇸🇰 · David Evans🇬🇧 · Anton Jusko🇬🇧 · Alexander Kluge🇨🇭 · Marian Krivda🇬🇧 · Ivan Kralik🇸🇰 · Roman Lietava🇬🇧 · Sanket Kumar Nayak🇮🇳 · Simone Ragoni🇬🇧 · Orlando Villalobos Baillie🇬🇧

   A major upgrade of the ALICE experiment is in progress and will result in high-rate data taking during LHC Run 3 (2022-2024). The LHC interaction rate at Point 2 where the ALICE experiment is located will be increased to $50\mathrm{kHz}$ in Pb--Pb collisions and $1\mathrm{MHz}$ in pp collisions. The ALICE experiment will be able to read out data at these interaction rates leading to an increase of the collected luminosity by a factor of up to about 100 with respect to LHC Runs 1 and 2. To satisfy these requirements, a new readout system has been developed for most of the ALICE detectors, allowing the full readout of the data at the required interaction rates without the need for a hardware trigger selection. A novel trigger and timing distribution system will be implemented, based on Passive Optical Network (PON) and GigaBit Transceiver (GBT) technology. To assure backward compatibility a triggered mode based on RD12 Trigger-Timing-Control (TTC) technology, as used in the previous LHC runs, will be maintained and re-implemented under the new Central Trigger System (CTS). A new universal ALICE Trigger Board (ATB) based on the Xilinx Kintex Ultrascale FPGA has been designed to function as a Central Trigger Processor (CTP), Local Trigger Unit (LTU), and monitoring interfaces. In this paper, this new hybrid multilevel system with continuous readout will be described, together with the triggering mechanism and algorithms. An overview of the CTS, the design of the ATB and the different communication protocols will be presented.

   ↳ physics.ins-dethep-exnucl-exEPJ Web Conf.(2021)·19 citations
3. 03*

   Regarding the distribution of glue in the pion

   Lei Chang🇨🇳 · Craig D. Roberts🇨🇳

   Understanding why the scale of emergent hadron mass is obvious in the proton but hidden in the pion may rest on mapping the distribution functions (DFs) of all partons within the pion and comparing them with those in the proton; and since glue provides binding in quantum chromodynamics, the glue DF could play a special role. Producing reliable predictions for the proton's DFs is difficult because the proton is a three valence-body bound-state problem. As sketched herein, the situation for the pion, a two valence-body problem, is much better, with continuum and lattice predictions for the valence-quark and glue DFs in agreement. This beginning of theory alignment is timely because experimental facilities now either in operation or planning promise to realise the longstanding goal of providing pion targets, thereby enabling precision experimental tests of rigorous theory predictions concerning Nature's most fundamental Nambu-Goldstone bosons.

   ↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2021)·31 citations
4. 04*

   Shape of atomic nuclei in heavy ion collisions

   Jiangyong Jia🇺🇸

   In the hydrodynamic model description of heavy ion collisions, the final-state anisotropic flow $v_n$ are linearly related to the strength of the multi-pole shape of the distribution of nucleons in the transverse plane ${\epsilon }_n$, $v_n\propto {\epsilon }_n$. The ${\epsilon }_n$, for $n=1,2,3,4$, are sensitive to the shape of the colliding ions, characterized by the quadrupole ${\beta }_2$, octupole ${\beta }_3$ and hexadecapole ${\beta }_4$ deformations. This sensitivity is investigated analytically and also in a Monte Carlo Glauber model. One observes a robust linear relation, $⟨{\epsilon }_n^2⟩=a_n^{\prime }+b_n^{\prime }{\beta }_n^2$, for events in a fixed centrality. The $⟨{\epsilon }_1^2⟩$ has a contribution from ${\beta }_3$ and ${\beta }_4$, and $⟨{\epsilon }_3^2⟩$ from ${\beta }_4$. In the ultra-central collisions, there are little cross contributions between ${\beta }_2$ and ${\epsilon }_3$ and between ${\beta }_3$ and ${\epsilon }_2$, but clear cross contributions are present in non-central collisions. Additionally, $⟨{\epsilon }_n^2⟩$ are insensitive to non-axial shape parameters such as the triaxiality. This is good news because the measurements of $v_2$, $v_3$ and $v_4$ can be used to constrain simultaneously the ${\beta }_2$, ${\beta }_3$, and ${\beta }_4$ values. This is best done by comparing two colliding ions with similar mass numbers and therefore nearly identical $a_n^{\prime }$, to obtain simple equation that relates the ${\beta }_n$ of the two species. This opens up the possibility to map the shape of the atomic nuclei at a timescale ($<10^{-24}$s) much shorter than probed by low-energy nuclear structure physics ($<10^{-21}$s), which ultimately may provide information complementary to those obtained in the nuclear structure experiments.

   ↳ nucl-thhep-phnucl-exPRC(2022)·122 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.