Fri·Oct 11, 2019Friday·October 11, 2019

1. 01*

   Measurement of non-strange D-meson production and azimuthal anisotropy in Pb-Pb collisions with ALICE at the LHC

   Syaefudin Jaelani (for the ALICE Collaboration)🇳🇱

   Heavy quarks are effective probes of the properties of the QGP created in ultra-relativistic heavy-ion collisions. The ALICE Collaboration measured the non-strange D-meson production in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The in-medium energy loss can be studied via the nuclear modification factor measurement. The measurement of the D-meson elliptic flow, $v_2$, allows us to investigate the participation of the heavy quarks in the collective expansion of the system at low momentum and their possible thermalization in the medium. Furthermore, the Event-Shape Engineering technique is used to measure D-meson elliptic flow in order to study the coupling of the charm quarks to the light quarks of the underlying medium.

   nucl-exhep-exSpringer Proc.Phys.(2020)·0 citations
2. 02*

   Measurement of electroweak-boson production in Pb--Pb and p--Pb collisions at the LHC with ALICE

   Guillaume Taillepied (for the ALICE Collaboration)🇫🇷

   Measurements of electroweak-bosons in heavy-ion collisions with ALICE are reported. They are measured at large rapidities, via their (di)muonic decay: Z $\to {\mu }^{+}{\mu }^{-}$ and W${}^{\pm }\to {\mu }^{\pm }\nu$. The Z production and nuclear modification factor in Pb--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 5.02 TeV are presented and compared to theoretical predictions with or without nuclear modifications of the Parton Distribution Functions. Measurements of electroweak-boson production in p--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 5.02 and 8.16 TeV are also presented and discussed.

   nucl-exhep-exPoS(2020)·0 citations
3. 03*

   Observation of thermal events on the plasma facing components of Wendelstein 7-X

   A. Puig Sitjes · Y. Gao · M. Jakubowski · P. Drewelow · H. Niemann · A. Ali · V. Moncada · F. Pisano · T.T. Ngo · B. Cannas · M. Sleczka · W7-X Team

   Long pulse operation of present and future magnetic fusion devices requires sophisticated methods for protection of plasma facing components from overheating. Typically, thermographic systems are being used to fulfill this task. Steady state operation requires, however, autonomous operation of the system and fully automatic detection of abnormal events. At Wendelstein 7-X (W7-X), a large advanced stellarator, which aims at demonstrating the capabilities of the stellarator line as a future fusion power plant, significant efforts are being undertaken to develop a fully automatic system based on thermographic diagnostics. In October 2018, the first divertor-based experimental campaign has been finished. One of the goals of this operation phase (named OP1.2) was to study the capabilities of the island divertor concept using an uncooled test divertor made of fine-grain graphite tiles. Throughout this campaign, it was possible to test the infrared imaging diagnostic system, which will be used to protect the actively water-cooled plasma facing components (PFCs) during the steady-state operation in the next experimental campaign. An overview of the most relevant thermal events on the PFCs that were detected in OP1.2 using this system are presented. This includes events that limited operation during the campaign, like baffe hot spots and divertor overloads, events that are potentially critical in steady state operation like leading edges, events caused by the ECRH and NBI heating systems and other events which are a common source of false alarms like surface layers. The detected thermal events are now part of an important and extensive image database which will be used to further automate the system by means of computer vision and machine learning techniques in preparation for steady-state operation, when the system must be able to detect dangerous events and protect the machine in real-time.

   ↳ physics.plasm-phnucl-exphysics.ins-detJINST(2019)·0 citations
4. 04*

   Ultra-low radioactivity Kapton and copper-Kapton laminates

   Isaac J. Arnquist🇺🇸 · Chelsie Beck🇫🇷 · Maria Laura di Vacri🇺🇸 · Khadouja Harouaka🇺🇸 · Richard Saldanha🇺🇸

   Polyimide-based materials, like Kapton, are widely used in flexible cables and circuitry due to their unique electrical and mechanical characteristics. This study is aimed at investigating the radiopurity of Kapton for use in ultralow background, rare-event physics applications by measuring the ${}^{238}$U, ${}^{232}$Th, and ${}^{nat}$K levels using inductively coupled plasma mass spectrometry. Commercial-off-the-shelf Kapton varieties, measured at approximately 950 and 120 pg/g ${}^{238}$U and ${}^{232}$Th (1.2$\times$10${}^4$ and 490 $\mu$Bq/kg), respectively, can be a significant background source for many current and next-generation ultralow background detectors. This study has found that the dominant contamination is due to the use of dicalcium phosphate (DCP), a nonessential slip additive added during manufacturing. Alternative Kapton materials were obtained that did not contain DCP and were determined to be significantly more radiopure than the commercially-available options with 12 and 19 pg/g ${}^{238}$U and ${}^{232}$Th (150 and 77 $\mu$Bq/kg), respectively. The lowest radioactivity version produced (Kapton ELJ, which contains an adhesive) was found to contain single digit pg/g levels of ${}^{238}$U and ${}^{232}$Th, two-to-three orders of magnitude cleaner than commercial-off-the-shelf options. Moreover, copper-clad polyimide laminates employing Kapton ELJ as the insulator were obtained and shown to be very radiopure at 8.6 and 22 pg/g ${}^{238}$U and ${}^{232}$Th (110 and 89 $\mu$Bq/kg), respectively.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2020)·18 citations
5. 05*

   Particle production as a function of underlying-event activity measured with ALICE at the LHC

   Valentina Zaccolo (for the ALICE Collaboration)🇮🇹

   ALICE has performed several measurements aimed at understanding the collective-like effects observed in small collision systems. New approaches may be needed to clarify particle-production mechanisms in high-multiplicity pp collisions. Transverse momentum ($p_{\mathrm{T}}$) spectra as a function of charged-particle multiplicity show intriguing features. For example, data exhibit a stronger-than-linear increase of the self-normalised high-$p_{\mathrm{T}}$ particle yields versus multiplicity. In order to understand the role of auto-correlations on these effects, it has been proposed to use the underlying event as a multiplicity estimator to factorise the hardest and the softest components of the events. This approach can also be used to study collective effects in events with exceptionally large activity in the underlying-event region with respect to the event-averaged mean. In these proceedings, $p_{\mathrm{T}}$ spectra as a function of underlying-event activity in pp collisions measured with the ALICE detector are presented. Results are compared with PYTHIA 8.2 event generator.

   ↳ hep-exnucl-exSpringer Proc.Phys.(2020)·5 citations
6. 06*

   Observing the deformation of nuclei with relativistic nuclear collisions

   Giuliano Giacalone🇫🇷

   I show that particle collider experiments on relativistic nuclear collisions can serve as direct probes of the deformation of the colliding nuclear species. I argue that collision events presenting very large multiplicities of particles and very small values of the average transverse momentum of the emitted hadrons probe collision geometries in which the nuclear ellipsoids fully overlap along their longer side. By looking at these events one selects interaction regions whose elliptic anisotropy is determined by the deformed nuclear shape, which becomes accessible experimentally through the measurement of the elliptic flow of outgoing hadrons.

   ↳ nucl-thhep-exhep-phnucl-exPRL(2020)·102 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.