Tue·Apr 10, 2018Tuesday·April 10, 2018

1. 01*

   First application of combined isochronous and Schottky mass spectrometry: Half-lives of fully ionized 49Cr24+ and 53Fe26+ atoms

   X. L. Tu🇨🇳 · X. C. Chen🇨🇳 · J. T. Zhang · P. Shuai🇨🇳 · K. Yue🇨🇳 · X. Xu🇨🇳 · C. Y. Fu🇨🇳 · Q. Zeng🇨🇳 · X. Zhou · Y. M. Xing🇨🇳 · J. X. Wu · R. S. Mao🇨🇳 and 12 other authors

   Lifetime measurements of b -decaying highly charged ions have been performed in the storage ring CSRe by applying the isochronous Schottky mass spectrometry. The fully ionized 49Cr and 53Fe ions were produced in projectile fragmentation of 58Ni primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled 49Cr24+ and 53Fe26+ ions. The extracted half-lives T1/2(49Cr24+) = 44.0(27) min and T1/2(53Fe26+) = 8.47(19) min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities.

   nucl-exphysics.ins-detPRC(2018)·18 citations
2. 02*

   A Precision Experiment to Investigate Long-Lived Radioactive Decays

   J. R. Angevaare🇳🇱 · P. Barrow🇨🇭 · L. Baudis🇨🇭 · P. A. Breur🇳🇱 · A. Brown🇨🇭 · A. P. Colijn🇳🇱 · G. Cox🇺🇸 · M. Gienal · F. Gjaltema · A. Helmling-Cornell · M. Jones🇺🇸 · A. Kish🇨🇭 and 9 other authors

   Radioactivity is understood to be described by a Poisson process, yet some measurements of nuclear decays appear to exhibit unexpected variations. Generally, the isotopes reporting these variations have long half lives, which are plagued by large measurement uncertainties. In addition to these inherent problems, there are some reports of time-dependent decay rates and even claims of exotic neutrino-induced variations. We present a dedicated experiment for the stable long-term measurement of gamma emissions resulting from $\beta$ decays, which will provide high-quality data and allow for the identification of potential systematic influences. Radioactive isotopes are monitored redundantly by thirty-two 76 mm $\times$ 76 mm NaI(Tl) detectors in four separate temperature-controlled setups across three continents. In each setup, the monitoring of environmental and operational conditions facilitates correlation studies. The deadtime-free performance of the data acquisition system is monitored by LED pulsers. Digitized photomultiplier waveforms of all events are recorded individually, enabling a study of time-dependent effects spanning microseconds to years, using both time-binned and unbinned analyses. We characterize the experiment's stability and show that the relevant systematics are accounted for, enabling precise measurements of effects at levels well below $\mathcal{O}(10^{-4})$.

   nucl-exphysics.ins-detJINST(2018)·4 citations
3. 03*

   Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ and $2.76$ TeV

   ALICE Collaboration

   Measurements of anisotropic flow coefficients with two- and multi-particle cumulants for inclusive charged particles in Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ and 2.76 TeV are reported in the pseudorapidity range $|\eta |<0.8$ and transverse momentum $0.2<p_{\text{T}}<50$ GeV/$c$. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) $\mu$b${}^{-1}$ in the centrality range 0-80%, is analysed. Flow coefficients up to the sixth flow harmonic ($v_6$) are reported and a detailed comparison among results at the two energies is carried out. The $p_{\text{T}}$ dependence of anisotropic flow coefficients and its evolution with respect to centrality and harmonic number $n$ are investigated. An approximate power-law scaling of the form $v_n(p_{\text{T}})\sim p_{\text{T}}^{n/3}$ is observed for all flow harmonics at low $p_{\text{T}}$ ($0.2<p_{\text{T}}<3$ GeV/$c$). At the same time, the ratios $v_n/v_m^{n/m}$ are observed to be essentially independent of $p_{\text{T}}$ for most centralities up to about $p_{\text{T}}=10$ GeV/$c$. Analysing the differences among higher-order cumulants of elliptic flow ($v_2$), which have different sensitivities to flow fluctuations, a measurement of the standardised skewness of the event-by-event $v_2$ distribution $P(v_2)$ is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise $P(v_2)$, extracting its parameters from fits to cumulants. The measurements are compared to different model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio.

   nucl-exhep-exJHEP(2018)·179 citations
4. 04*

   Ionization Electron Signal Processing in Single Phase LArTPCs II. Data/Simulation Comparison and Performance in MicroBooNE

   MicroBooNE collaboration: C. Adams · R. An · J. Anthony · J. Asaadi · M. Auger · S. Balasubramanian · B. Baller · C. Barnes · G. Barr · M. Bass · F. Bay · A. Bhat and 158 other authors

   The single-phase liquid argon time projection chamber (LArTPC) provides a large amount of detailed information in the form of fine-grained drifted ionization charge from particle traces. To fully utilize this information, the deposited charge must be accurately extracted from the raw digitized waveforms via a robust signal processing chain. Enabled by the ultra-low noise levels associated with cryogenic electronics in the MicroBooNE detector, the precise extraction of ionization charge from the induction wire planes in a single-phase LArTPC is qualitatively demonstrated on MicroBooNE data with event display images, and quantitatively demonstrated via waveform-level and track-level metrics. Improved performance of induction plane calorimetry is demonstrated through the agreement of extracted ionization charge measurements across different wire planes for various event topologies. In addition to the comprehensive waveform-level comparison of data and simulation, a calibration of the cryogenic electronics response is presented and solutions to various MicroBooNE-specific TPC issues are discussed. This work presents an important improvement in LArTPC signal processing, the foundation of reconstruction and therefore physics analyses in MicroBooNE.

   ↳ physics.ins-dethep-exnucl-exJINST(2018)·161 citations
5. 05*

   Next Generation of Phonon Tests of Lorentz Invariance using Quartz BAW Resonators

   Maxim Goryachev🇦🇺 · Zeyu Kuang🇨🇳 · Eugene N. Ivanov🇦🇺 · Philipp Haslinger🇺🇸 · Holger Muller🇺🇸 · Michael E. Tobar🇦🇺

   We demonstrate technological improvements in phonon sector tests of Lorentz Invariance that implement quartz Bulk Acoustic Wave oscillators. In this experiment, room temperature oscillators with state-of-the-art phase noise are continuously compared on a platform that rotates at a rate of order a cycle per second. The discussion is focused on improvements in noise measurement techniques, data acquisition and data processing. Preliminary results of the second generation of such tests are given, and indicate that SME coefficients in the matter sector can be measured at a precision of order $10^{-16}$ GeV after taking a years worth of data. This is equivalent to an improvement of two orders of magnitude over the prior acoustic phonon sector experiment.

   ↳ physics.ins-detnucl-exphysics.data-anIEEE Transactions on Ultrasonics, Ferroel…·13 citations
6. 06*

   Charm quarks are more hydrodynamic than light quarks in final-state elliptic flow

   Hanlin Li🇨🇳 · Zi-Wei Lin🇺🇸 · Fuqiang Wang🇺🇸

   We study the charm quark elliptic flow ($v_2$) in heavy ion as well as small system collisions by tracking the evolution history of quarks of different flavors within a multi-phase transport model. The charm quark $v_2$ is studied as a function of the number of collisions the charm quark suffers with other quarks and then compared to the $v_2$ of lighter quarks. We find that the common escape mechanism is at work for both the charm and light quark $v_2$. However, contrary to the naive expectation, the hydrodynamics-type flow is found to contribute more to the final state charm $v_2$ than light quark $v_2$. This could be explained by the smaller average deflection angle the heavier charm quark undergoes in each collision, so that heavy quarks need more scatterings to accumulate a significant $v_2$, while lighter quarks can more easily change directions with scatterings with their $v_2$ coming more from the escape mechanism. Our finding thus suggests that the charm $v_2$ is a better probe for studying the hydrodynamic properties of the quark-gluon plasma.

   ↳ hep-phnucl-exnucl-thPRC(2019)·25 citations
7. 07*

   Reconstructing the impact parameter of proton-nucleus and nucleus-nucleus collisions

   Rudolph Rogly🇫🇷 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷

   In proton-nucleus and nucleus-nucleus collision experiments, one determines the centrality of a collision according to the multiplicity or energy deposited in a detector. This serves as a proxy for the true collision centrality, as defined by the impact parameter. We show that the probability distribution of impact parameter in a given bin of experiment-defined centrality can be reconstructed without assuming any specific model for the collision dynamics, in both proton-nucleus and nucleus-nucleus systems. The reconstruction is reliable up to about 10\% centrality, and is more accurate for nucleus-nucleus collisions. We perform an application of our procedure to experimental data from all the CERN Large Hadron Collider (LHC) collaborations, from which we extract, in Pb+Pb and $p$+Pb collisions, the corresponding distributions of impact parameter.

   ↳ nucl-thhep-phnucl-exPRC(2018)·38 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.