Tue·Feb 12, 2019Tuesday·February 12, 2019

1. 01*

   Reactor Neutrinos: Toward Oscillations

   Petr Vogel🇺🇸

   I shall sketch the history of reactor neutrino physics over five decades since the Reines-Cowan proof of neutrino existence in the late 50s, till the advent of the present era of precision reactor neutrino oscillation experiments. There are three chapters of this story: i) Exploration of possibilities of the reactor neutrinos in the 60s and 70s; ii) Looking for oscillations under the streetlamp in the 80s and 90s; iii) Exploring oscillations in detail with known (almost) $\Delta m_{atm}^2$ and $\Delta m_{sol}^2$.}

   ↳ hep-phnucl-exnucl-thphysics.ins-det1 citation
2. 02*

   The analysing powers in proton-deuteron elastic scattering

   Yu.Uzikov🇷🇺 · C.Wilkin🇬🇧

   It is shown that the ratio of the deuteron and proton analysing powers in proton-deuteron elastic scattering at small angles is sensitive to subtle effects in a theoretical description. These include the transverse spin-spin term in the elementary nucleon-nucleon amplitudes and double-scattering corrections. On the other hand there is far less sensitivity to the spin-orbit amplitude and to binding or other kinematic effects associated with the use of the deuteron, as either target or projectile. The available data are in agreement with the results of a refined Glauber theory model.

   ↳ nucl-thnucl-exPLB(2019)·3 citations
3. 03*

   Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.44 TeV

   CMS Collaboration

   Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=$ 5.44 TeV are presented. The measurements are based on data collected by the CMS experiment at the LHC. The yield of primary charged hadrons produced in xenon-xenon collisions in the pseudorapidity range $|\eta |$ $<$ 3.2 is determined using the silicon pixel detector in the CMS tracking system. For the 5% most central collisions, the charged-hadron pseudorapidity density in the midrapidity region $|\eta |$ $<$ 0.5 is found to be 1187 $\pm$ 36 (syst), with a negligible statistical uncertainty. The rapidity distribution of charged hadrons is also presented in the range $|y|$ $<$ 3.2 and is found to be independent of rapidity around $y=$ 0. Existing Monte-Carlo event generators are unable to simultaneously describe both results. Comparisons of charged-hadron multiplicities between xenon-xenon and lead-lead collisions at similar collision energies show that particle production at midrapidity is strongly dependent on the collision geometry in addition to the system size and collision energy.

   ↳ hep-exnucl-exPLB(2019)·34 citations
4. 04*

   Coherent J/$\psi$ photoproduction in Pb-Pb collisions with nuclear overlap studied with ALICE at the LHC

   L. Massacrier (for the ALICE Collaboration)🇫🇷

   The photoproduction of heavy vector mesons in the electromagnetic interactions of ultra-relativistic nuclei is sensitive to the gluon distribution in the nucleus and thus to cold nuclear matter effects like shadowing or parton saturation. Besides the well known observations of vector meson production in ultra-peripheral collisions, first observations of an excess over the expected hadronic J/$\psi$ production at very low transverse momentum ($p_T<$~0.3 GeV/$c$) in peripheral and semi-central nucleus-nucleus collisions both at LHC and RHIC energies were interpreted as the first sign of coherent J/$\psi$ photoproduction occurring in Pb-Pb collisions with nuclear overlap. The ALICE Collaboration published the J/$\psi$ coherent photoproduction cross sections in peripheral and semi-central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76~TeV and forward rapidity ($2.5<y<4.0$). Using the LHC Run-2 data, ALICE presents preliminary results in peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV at mid-rapidity ($|y|<0.9$) and forward rapidity. Thanks to the very good tracking resolution of the central barrel, the extraction of the $p_T$-differential cross section was also possible, strengthening the photoproduction origin of the observed J/$\psi$ excess. The quantitative understanding of this low-$p_T$ excess poses significant theoretical challenges since the J/$\psi$ photoproduction depends on the collision dynamics as well as on the photon-flux and the photonuclear cross section. In this proceeding, we present the latest ALICE measurements on J/$\psi$ photoproduction cross section in peripheral Pb-Pb collisions, with emphasis on the new forward measurement in the dimuon decay channel at $\sqrt{s_{\mathrm{NN}}}$ = 5.02~TeV. These results will be discussed and compared to several model calculations of J/$\psi$ photoproduction in Pb-Pb collisions with nuclear overlap.

   ↳ hep-exnucl-exPoS(2019)·4 citations
5. 05*

   Longitudinal spin asymmetries in polarized deuteron DIS with spectator tagging

   W. Cosyn🇧🇪 · C. Weiss🇺🇸

   Polarized electron-deuteron DIS with spectator proton tagging offers a way of measuring the neutron spin structure functions with maximal theoretical control of nuclear effects. We calculate the nuclear structure factors in the longitudinal double-spin asymmetries using methods of light-front nuclear structure. A unique feature of the spin-1 system is that spin asymmetries can be formed either relative to the cross section in all three spin states (${\lambda }_d=\pm 1,0$) or in the two maximum-spin states only ($\pm 1$, involving tensor polarization). We find that the two-state deuteron spin asymmetry at small spectator proton momenta permits accurate extraction of the neutron structure function $g_{1n}$. Such measurements could be performed at a future electron-ion collider (EIC) with polarized deuteron beams and suitable forward detectors.

   ↳ hep-phnucl-exnucl-thPoS(2019)·0 citations
6. 06*

   Neutron-mirror neutron oscillations in stars

   Wanpeng Tan🇺🇸

   Based on a newly proposed mirror-matter model of neutron-mirror neutron ($n-n^{\prime }$) oscillations [Phys. Lett. B 797, 134921 (2019)], evolution and nucleosynthesis in single stars under a new theory is presented. In the new model, $n-n^{\prime }$ oscillations are caused by a very small mass difference between particles of the two sectors. The new theory with the new $n-n^{\prime }$ model can demonstrate the evolution in a much more convincing way than the conventional belief. In particular, many observations in stars show strong support for the new theory and the new $n-n^{\prime }$ model. For example, progenitor mass limits and structures for white dwarfs and neutron stars, two different types of core collapse supernovae (II-P and II-L), synthesis of heavy elements, pulsating phenomena in stars, etc, can all be easily and naturally explained under the new theory.

   ↳ astro-ph.SRastro-ph.HEhep-thnucl-ex10 citations
7. 07*

   Production of open charm and beauty states in pPb collisions with LHCb

   Yanxi Zhang🇨🇭

   These proceedings summarize the LHCb measurements of charm- and beauty-hadron production in pPb collisions. The studies are made down to very low-\pt of the observed heavy-flavor hadrons using fully reconstructed decays. Nuclear matter effects are quantified via nuclear modification factors and forward-backward production ratios. A strong suppression is observed at positive rapidity (proton beam direction), while a modest or no suppression is seen for the backward rapidity (lead beam direction). The nuclear parton distributions of the lead nucleus is constrained down to Bjorken-$x\sim 10^{-5}$, assuming it is the only nuclear effect for open heavy-flavor production. These data provide important inputs to understand the Quark-Gluon Plasma formed in heavy-nucleus collisions.

   ↳ hep-exnucl-exPoS(2019)·2 citations
8. 08*

   Core-excitation effects in three-body breakup reactions studied using the Faddeev formalism

   A. Deltuva🇱🇹

   Previous studies of $(d,p)$ reactions in three-body (proton, neutron, nuclear core) systems revealed a nontrivial effect of the core excitation: the transfer cross section cannot be factorized into the spectroscopic factor and the single-particle cross section obtained neglecting the core excitation. This observable, up to a kinematic factor, is the angular distribution of the core nucleus in the $(p,d)$ reaction. The study of the core excitation effect for the most closely related observable in the $(p,pn)$ three-body breakup, i.e., the core angular distribution, is aimed in the present work. Breakup of the one-neutron halo nucleus in the collision with the proton is described using three-body Faddeev-type equations extended to include the excitation of the nuclear core. The integral equations for transition operators are solved in the momentum-space partial-wave representation. Breakup of 11Be nucleus as well as of model $A=11$ $p$-wave nuclei is studied at beam energies of 30, 60, and 200 MeV per nucleon. Angular and momentum distributions for the 10Be core in ground and excited states is calculated. In sharp contrast to $(p,d)$ reactions, the differential cross section in most cases factorizes quite well into the spectroscopic factor and the single-particle cross section. Due to different reaction mechanisms the core excitation effect in the breakup is very different from transfer reactions. A commonly accepted approach to evaluate the cross section, i.e., the rescaling of single-particle model results by the corresponding spectroscopic factor, appears to be reliable for breakup though it fails in general for transfer reactions.

   ↳ nucl-thnucl-exPRC(2019)·9 citations
9. 09*

   Search for dark matter with a 231-day exposure of liquid argon using DEAP-3600 at SNOLAB

   R. Ajaj🇨🇦 · P.-A. Amaudruz🇨🇦 · G. R. Araujo🇩🇪 · M. Baldwin🇬🇧 · M. Batygov🇨🇦 · B. Beltran🇨🇦 · C. E. Bina🇨🇦 · J. Bonatt🇨🇦 · M. G. Boulay🇨🇦 · B. Broerman🇨🇦 · J. F. Bueno🇨🇦 · P. M. Burghardt🇩🇪 and 90 other authors

   DEAP-3600 is a single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. This paper reports on the analysis of a 758 tonne\cdot day exposure taken over a period of 231 live-days during the first year of operation. No candidate signal events are observed in the WIMP-search region of interest, which results in the leading limit on the WIMP-nucleon spin-independent cross section on a LAr target of $3.9\times 10^{-45}$ cm${}^2$ ($1.5\times 10^{-44}$ cm${}^2$) for a 100 GeV/c${}^2$ (1 TeV/c${}^2$) WIMP mass at 90\% C. L. In addition to a detailed background model, this analysis demonstrates the best pulse-shape discrimination in LAr at threshold, employs a Bayesian photoelectron-counting technique to improve the energy resolution and discrimination efficiency, and utilizes two position reconstruction algorithms based on PMT charge and photon arrival times.

   ↳ astro-ph.COastro-ph.IMhep-exnucl-exPRD(2019)·314 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.