Fri·Feb 15, 2019Friday·February 15, 2019

1. 01*

   Experimental nuclear astrophysics in Italy

   C. Broggini🇮🇹 · O. Straniero🇮🇹 · M.G.F. Taiuti🇮🇹 · G. de Angelis🇮🇹 · G. Benzoni🇮🇹 · G.E. Bruno🇮🇹 · S. Bufalino🇮🇹 · G. Cardella🇮🇹 · N. Colonna🇮🇹 · M. Contalbrigo🇮🇹 · G. Cosentino🇮🇹 · S. Cristallo🇮🇹 and 27 other authors

   Nuclear astrophysics, the union of nuclear physics and astronomy, went through an impressive expansion during the last twenty years. This could be achieved thanks to milestone improvements in astronomical observations, cross section measurements, powerful computer simulations and much refined stellar models. Italian groups are giving quite important contributions to every domain of nuclear astrophysics, sometimes being the leaders of worldwide unique experiments. In this paper we will discuss the astrophysical scenarios where nuclear astrophysics plays a key role and we will provide detailed descriptions of the present and future of the experiments on nuclear astrophysics which belong to the scientific programme of INFN (the National Institute for Nuclear Physics in Italy).

   nucl-exastro-ph.SRnucl-thRiv.Nuovo Cim.(2019)·18 citations
2. 02*

   Equation of state at finite densities for QCD matter in nuclear collisions

   Akihiko Monnai🇯🇵 · Björn Schenke🇺🇸 · Chun Shen🇺🇸

   We construct the QCD equation of state at finite chemical potentials including net baryon, electric charge, and strangeness, based on the conserved charge susceptibilities determined from lattice QCD simulations and the equation of state of the hadron resonance gas model. For the application to relativistic heavy ion collisions we consider the situation of strangeness neutrality and matter with a fixed electric charge-to-baryon ratio, resembling that of heavy nuclei. The importance of finite electric charge and strangeness chemical potentials for particle production in heavy ion collisions is demonstrated using hydrodynamic simulations.

   ↳ nucl-thhep-phnucl-exPRC(2019)·180 citations
3. 03*

   Quark Gluon Plasma Formation in Proton-Proton Collisions Using PYTHIA

   M. T. AlFiky🇪🇬 · O. T. ElSherif🇪🇬 · A. M. Hamed🇺🇸

   The aim of this study is to investigate the possibility of the Quark Gluon Plasma (QGP) formation in proton-proton (p-p) collisions. The p-p collisions at center of mass energies $\sqrt{s_{{}_{NN}}}=200$ $GeV$ and $\sqrt{s_{{}_{NN}}}=13$ $TeV$ were simulated using PYTHIA. These are the available energies of the current collider experiments; the Relativistic Heavy Ion Collider (RHIC), and the Large Hadron Collider (LHC). To search for the QGP Phase, the near-side yield to the away-side yield ratios were calculated for high transverse momentum particles. These ratios were then compared for the low and high multiplicity events as a function of transverse momentum. At the LHC energy in the high multiplicity events, the away-side yields show suppression compared with the near-side yields. This suppression might indicate the possibility of forming the QGP at the high-energy and high-multiplicity events in p-p collisions.

   ↳ hep-exnucl-ex3 citations
4. 04*

   Constraints on nuclear parton distributions from dijet photoproduction at the LHC

   V. Guzey (Jyvaskyla U., Helsinki U., St. Petersburg, INP)🇷🇺 · M. Klasen (Munster U., ITP)🇩🇪

   Using QCD calculations of the cross section of inclusive dijet photoproduction in Pb-Pb ultraperipheral collisions in the LHC kinematics as pseudo-data, we study the effect of including these data using the Bayesian reweighting technique on nCTEQ15, nCTEQ15np, and EPPS16 nuclear parton distribution functions (nPDFs). We find that, depending on the assumed error of the pseudo-data, it leads to a significant reduction of the nPDF uncertainties at small values of the momentum fraction $x_A$. Taking the error to be 5\%, the uncertainty of nCTEQ15 and nCTEQ15np nPDFs reduces approximately by a factor of two at $x_A=10^{-3}$. At the same time, the reweighting effect on EPPS16 nPDFs is much smaller due to the higher value of the tolerance and a more flexible parametrization form.

   ↳ hep-phnucl-exnucl-thEPJC(2019)·29 citations
5. 05*

   Transparent tiles of silica aerogels for high-energy physics

   Makoto Tabata🇯🇵

   Silica aerogels are important to be used as photon radiators in Cherenkov counters for high-energy-physics experiments because of their optical transparency and intermediate refractive indices between those of gases and liquids or solids. Cherenkov counters that employ silica aerogels as radiators and photodetectors are often used to identify subatomic charged particles (e.g., electrons, protons, and pions) with momenta on the order of sub-GeV/$c$ to GeV/$c$; they are also used to measure particle velocities in accelerator-based particle- and nuclear-physics experiments and in space- and balloon-borne experiments in the field of cosmic-ray physics. Recent studies have demonstrated that it is important for the design of Cherenkov counters that the transparent silica-aerogel tiles comprise solid material with recently improved transparency and a refractive index that can be controlled between 1.003 and 1.26 by varying the bulk density in the range of 0.01$-$1.0 g/cm${}^3$. Additionally, a technique for fabricating large-area silica-aerogel tiles without cracking has been developed. In this chapter, we describe advances in the technologies for producing silica aerogels with high optical performances to be used in scientific instruments. We further discuss the principles underlying the operation of detectors based on the Cherenkov effect. We also review applications of silica aerogels in specific high-energy-physics experiments.

   ↳ physics.ins-detastro-ph.IMcond-mat.mtrl-scihep-ex+1In: Aegerter, M.A., Leventis, N., Koebel,…·1 citation
6. 06*

   Electron Drift and Longitudinal Diffusion in High Pressure Xenon-Helium Gas Mixtures

   A.D. McDonald🇺🇸 · K. Woodruff🇺🇸 · B. Al Atoum🇺🇸 · D. González-Díaz🇪🇸 · B.J.P. Jones🇺🇸 · C. Adams🇺🇸 · V. Álvarez🇪🇸 · L. Arazi🇮🇱 · I.J. Arnquist🇺🇸 · C.D.R Azevedo🇵🇹 · K. Bailey🇺🇸 · F. Ballester🇪🇸 and 74 other authors

   We report new measurements of the drift velocity and longitudinal diffusion coefficients of electrons in pure xenon gas and in xenon-helium gas mixtures at 1-9 bar and electric field strengths of 50-300 V/cm. In pure xenon we find excellent agreement with world data at all $E/P$, for both drift velocity and diffusion coefficients. However, a larger value of the longitudinal diffusion coefficient than theoretical predictions is found at low $E/P$ in pure xenon, below the range of reduced fields usually probed by TPC experiments. A similar effect is observed in xenon-helium gas mixtures at somewhat larger $E/P$. Drift velocities in xenon-helium mixtures are found to be theoretically well predicted. Although longitudinal diffusion in xenon-helium mixtures is found to be larger than anticipated, extrapolation based on the measured longitudinal diffusion coefficients suggest that the use of helium additives to reduce transverse diffusion in xenon gas remains a promising prospect.

   ↳ physics.ins-detnucl-exJINST(2019)·34 citations
7. 07*

   Magnetic dipole excitation and its sum rule in nuclei with two valence nucleons

   Tomohiro Oishi🇭🇷 · Nils Paar🇭🇷

   Background: Magnetic dipole (M1) excitation is the leading mode of nuclear excitation by the magnetic field, which couples unnatural-parity states. Since the M1 excitation occurs mainly for open-shell nuclei, the nuclear pairing effect is expected to play a role. As expected from the form of operator, this mode may provide the information on the spin-related properties, including the spin component of dineutron and diproton correlations. In general, the sum rule for M1 transition strength has not been derived yet. Purpose: To investigate the M1 excitation of the systems with two valence nucleons above the closed-shell core, with pairing correlation included, and to establish the M1 sum rule that could be used to validate theoretical and experimental approaches. Possibility to utilize the M1 excitation as a tool to investigate the pairing correlation in medium is also discussed. Method: Three-body model, which consists of a rigid spherical core and two valence nucleons, is employed. Interactions for its two-body subsystems are phenomenologically determined in order to reproduce the two-body and three-body energies. We also derive the M1 sum rule within this three-body picture. Conclusion: The introduced M1 sum rule can be utilized as a benchmark for model calculations of M1 transitions in the systems with two valence nucleons. The total sum of the M1 transition strength is related with the coupled spin of valence nucleons in the open shell, where the pairing correlation is unnegligible. The three-body-model calculations for 18 O, 18 Ne, and 42 Ca nuclei demonstrate a significant effect of the pairing correlations on the low-lying M1 transitions. Therefore, further experimental studies of M1 transitions in those systems are on demand, in order to validate proposed sum rule, provide a suitable probe for the nuclear pairing in medium, as well as to optimize the pairing models.

   ↳ nucl-thnucl-exPRC(2019)·12 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.