Fri·Mar 2, 2018Friday·March 2, 2018

1. 01*

   Jet properties in PbPb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   Modifications of the properties of jets in PbPb collisions, relative to those in pp collisions, are studied at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV via correlations of charged particles with the jet axis in relative pseudorapidity ($\Delta \eta$), relative azimuth ($\Delta \varphi$), and relative angular distance from the jet axis $\Delta \mathrm{r}=\sqrt{(\Delta \eta {)}^2+(\Delta \varphi {)}^2}$. This analysis uses data collected with the CMS detector at the LHC, corresponding to integrated luminosities of 404 $\mu$b${}^{-1}$ and 27.4 pb${}^{-1}$ for PbPb and pp collisions, respectively. Charged particle number densities, jet fragmentation functions, and jet shapes are presented as a function of PbPb collision centrality and charged-particle track transverse momentum, providing a differential description of jet modifications due to interactions with the quark-gluon plasma.

   nucl-exhep-exJHEP(2018)·110 citations
2. 02*

   Development of GEM Detectors at Hampton University

   Anusha Liyanage🇺🇸 · Michael Kohl🇺🇸 · Jesmin Nazeer🇺🇸 · Tanvi Patel🇺🇸

   Two GEM telescopes, each consisting of three 10x10 cm${}^2$ triple-GEM chambers were built, tested and operated by the Hampton University group. The GEMs are read out with APV25 frontend chips and FPGA based digitizing electronics developed by INFN Rome. The telescopes were used for the luminosity monitoring system at the OLYMPUS experiment at DESY in Germany, with positron and electron beams at 2 GeV. The GEM elements have been recycled to serve in another two applications: Three GEM elements are used to track beam particles in the MUSE experiment at PSI in Switzerland. A set of four elements has been configured as a prototype tracker for phase 1a of the DarkLight experiment at the Low-Energy Recirculator Facility (LERF) at Jefferson Lab in Newport News, USA, in a first test run in summer 2016. The Hampton group is responsible for the DarkLight phase-I lepton tracker in preparation. Further efforts are ongoing to optimize the data acquisition speed for GEM operations in MUSE and DarkLight. An overview of the group's GEM detector related activities will be given.

   ↳ physics.ins-detnucl-exPoS(2019)·5 citations
3. 03*

   Nonlinear coupling of flow harmonics: Hexagonal flow and beyond

   Giuliano Giacalone🇫🇷 · Li Yan🇨🇦 · Jean-Yves Ollitrault🇫🇷

   Higher Fourier harmonics of anisotropic flow ($v_4$ and beyond) get large contributions induced by elliptic and triangular flow through nonlinear response. We present a general framework of nonlinear hydrodynamic response which encompasses the existing one, and allows to take into account the mutual correlation between the nonlinear couplings affecting Fourier harmonics of any order. Using Large Hadron Collider data on Pb+Pb collisions at ~$\sqrt[]{s}=2.76$ TeV, we perform an application of our formalism to hexagonal flow, $v_6$, a coefficient affected by several nonlinear contributions which are of the same order of magnitude. We obtain the first experimental measure of the coefficient ${\chi }_{624}$, which couples $v_6$ to $v_2$ and $v_4$. This is achieved by putting together the information from several analyses: event-plane correlations, symmetric cumulants, as well as new higher-order moments recently analyzed by the ALICE collaboration. The value of ${\chi }_{624}$ extracted from data is in fair agreement with hydrodynamic calculations, although with large error bars, which would be dramatically reduced by a dedicated analysis. We argue that within our formalism the nonlinear structure of a given higher harmonic can be determined more accurately than the harmonic itself, and we emphasize potential applications to future measurements of $v_7$ and $v_8$.

   ↳ nucl-thhep-phnucl-exPRC(2018)·14 citations
4. 04*

   A Cold/Ultracold Neutron Detector using Fine-grained Nuclear Emulsion with Spatial Resolution less than 100 nm

   N. Naganawa🇯🇵 · T. Ariga🇨🇭 · S. Awano🇯🇵 · M. Hino🇯🇵 · K. Hirota🇯🇵 · H. Kawahara🇯🇵 · M. Kitaguchi🇯🇵 · K. Mishima🇯🇵 · H. M. Shimizu🇯🇵 · S. Tada🇯🇵 · S. Tasaki🇯🇵 · A. Umemoto🇯🇵

   A new type of cold/ultracold neutron detector that can realize a spatial resolution of less than 100 nm was developed using nuclear emulsion. The detector consists of a fine-grained nuclear emulsion coating and a 50-nm thick ${}^{10}$B${}_4$C layer for the neutron conversion. The detector was exposed to cold and ultracold neutrons (UCNs) at the J-PARC. Detection efficiencies were measured as (0.16$\pm$0.02)% and (12$\pm$2)% for cold and ultracold neutrons consistently with the ${}^{10}$B content in the converter. Positions of individual neutrons can be determined by observing secondary particle tracks recorded in the nuclear emulsion. The spatial resolution of incident neutrons were found to be in the range of 11-99 nm in the angle region of tan$\theta \le 1.9$, where $\theta$ is the angle between a recorded track and the normal direction of the converter layer. The achieved spatial resolution corresponds to the improvement of one or two orders of magnitude compared with conventional techniques and it is comparable with the wavelength of UCNs.

   ↳ physics.ins-dethep-exnucl-exEPJC(2018)·11 citations
5. 05*

   Beta Spectrum Generator: High precision allowed $\beta$ spectrum shapes

   Leendert Hayen🇧🇪 · Nathal Severijns🇧🇪

   Several searches for Beyond Standard Model physics rely on an accurate and highly precise theoretical description of the allowed $\beta$ spectrum. Following recent theoretical advances, a C++ implementation of an analytical description of the allowed beta spectrum shape was constructed. It implements all known corrections required to give a theoretical description accurate to a few parts in $10^4$. The remaining nuclear structure-sensitive input can optionally be calculated in an extreme single-particle approximation with a variety of nuclear potentials, or obtained through an interface with more state-of-the-art computations. Due to its relevance in modern neutrino physics, the corresponding (anti)neutrino spectra are readily available with appropriate radiative corrections. In the interest of user-friendliness, a graphical interface was developed in Python with a coupling to a variety of nuclear databases. We present several test cases and illustrate potential usage of the code. Our work can be used as the foundation for current and future high-precision experiments related to the beta decay process. Source code: https://github.com/leenderthayen/BSG Documentation: http://bsg.readthedocs.io

   ↳ nucl-thnucl-exComput.Phys.Commun.(2019)·24 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.