Tue·Feb 18, 2020Tuesday·February 18, 2020

1. 01*

   Jet shapes and fragmentation functions in Au+Au collisions at sqrt(sNN) = 200 GeV in STAR

   Saehanseul Oh (for the STAR Collaboration)🇺🇸

   The STAR Collaboration reports measurements of differential jet shapes and semi-inclusive jet fragmentation functions in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV with the STAR detector at RHIC. Jet shapes, which represent the radial distribution of momentum carried by constituents, are measured differentially for (1) the charged particles transverse momentum and (2) the jet azimuthal angle relative to the second-order event plane. Based on the semi-inclusive population of jets recoiling from a high transverse momentum trigger hadron, jet fragmentation functions in 40-60% central heavy-ion collisions are measured, and compared to those in PYTHIA simulations for pp collisions.

   nucl-exhep-exNPA(2021)·7 citations
2. 02*

   Study of Two-Photon Exchange via the Beam Transverse Single Spin Asymmetry in Electron-Proton Elastic Scattering at Forward Angles over a Wide Energy Range

   B. Gou (1, 2, 3)🇩🇪 · J. Arvieux (4)🇫🇷 · K. Aulenbacher (1, 2)🇩🇪 · D. Balaguer Ríos (1)🇩🇪 · S. Baunack (1)🇩🇪 · D. Becker (1)🇩🇪 · L. Capozza (1, 2)🇩🇪 · W. Deconinck (5)🇺🇸 · J. Diefenbach (1)🇩🇪 · R. Frascaria (4)🇫🇷 · M. Gorchtein (1)🇩🇪 · B. Gläser (1)🇩🇪 and 17 other authors

   We report on a new measurement of the beam transverse single spin asymmetry in electron-proton elastic scattering, $A_{\perp }^{ep}$, at five beam energies from 315.1 MeV to 1508.4 MeV and at a scattering angle of $30^{\circ }<\theta <40^{\circ }$. The covered $Q^2$ values are 0.032, 0.057, 0.082, 0.218, 0.613 (GeV/c)${}^2$. The measurement clearly indicates significant inelastic contributions to the two-photon-exchange (TPE) amplitude in the low-$Q^2$ kinematic region. No theoretical calculation is able to reproduce our result. Comparison with a calculation based on unitarity, which only takes into account elastic and $\pi \mathrm{N}$ inelastic intermediate states, suggests that there are other inelastic intermediate states such as $\pi \pi \mathrm{N}$, $\mathrm{K\Lambda }$ and $\eta \mathrm{N}$. Covering a wide energy range, our new high-precision data provide a benchmark to study those intermediate states.

   nucl-exPRL(2020)·15 citations
3. 03*

   Searching for the critical point of strongly interacting matter in nucleus-nucleus collisions at CERN SPS

   Nikolaos Davis (for the NA61/SHINE Collaboration)🇵🇱

   The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at CERN SPS. In the course of the experiment, a beam momentum and system size scan is performed. Local proton density fluctuations in transverse momentum space represent an order parameter of the chiral phase transition and are expected to scale according to a universal power-law in the vicinity of the CP; we probe their behavior through an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum space. Previous such analyses revealed power-law behavior in NA49 Si+Si collisions at 158$A$ GeV/$c$, with no intermittency observed in lighter or heavier NA49 & NA61/SHINE systems at the same energy. We now extend the analysis to NA61/SHINE Ar+Sc collisions at 150$A$ GeV/$c$, similar in size and baryochemical potential to NA49 Si+Si. We employ statistical techniques to subtract non-critical background and estimate statistical and systematic uncertainties. Subsequently, we use Monte Carlo simulations to assess the statistical significance of the observed intermittency effect.

   nucl-exActa Phys.Polon.Supp.(2020)·16 citations
4. 04*

   Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)

   N. Otuka🇦🇹 · E. Dupont🇫🇷 · V. Semkova🇦🇹 · B. Pritychenko🇺🇸 · A.I. Blokhin🇷🇺 · M. Aikawa🇯🇵 · S. Babykina🇷🇺 · M. Bossant🇫🇷 · G. Chen🇨🇳 · S. Dunaeva🇷🇺 · R.A. Forrest🇦🇹 · T. Fukahori🇯🇵 and 28 other authors

   The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) is successfully collaborating in the maintenance and development of the EXFOR library. As the scope of published data expands (e.g., to higher energy, to heavier projectile) to meet the needs from the frontier of sciences and applications, it becomes nowadays a hard and challenging task to maintain both completeness and accuracy of the whole EXFOR library. The paper describes evolution of the library with highlights on recent developments.

   nucl-exNucl.Data Sheets(2014)·496 citations
5. 05*

   Constraining parton energy loss via angular and momentum based differential jet measurements at STAR

   Raghav Kunnawalkam Elayavalli (for the STAR Collaboration)🇺🇸

   Parton energy loss has been established as an essential signature of the Quark-Gluon Plasma (QGP) in heavy ion collisions since the earliest measurements at RHIC indicating suppression of hadron spectra at high $p_{\mathrm{T}}$ and coincidence yields. Understanding this phenomenon of jet quenching is a requirement for extracting the microscopic properties of the QGP via jet-tomography. STAR has recently introduced a technique called Jet Geometry Engineering (JGE) wherein we enforce particular selection criteria imposed on the jet collection, such as recoiling off a high $p_{\mathrm{T}}$ hadron trigger along with an additional transverse momentum threshold for jet constituents in events with back-to-back di-jets. With JGE, we are able to control the extent of energy loss ranging from quenched/imbalanced to recovered/balanced di-jets. Since jet quenching is also expected to be dependent on the resolution/transverse-length scales with which the jet probes the medium, it is necessary to perform differential measurements with a handle on both momentum and angular scales. To quantify the angular scale within jets, we present the first measurement of the jet's inherent angular structure in Au$+$Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV via the opening angle between the two leading sub-jets (${\theta }_{\mathrm{SJ}}$). We also measure the di-jet asymmetry $A_{\mathrm{J}}$ differentially as a function of the ${\theta }_{\mathrm{SJ}}$ observable for these di-jets and find no significant dependence of the energy loss on the opening angle of the recoil jet.

   ↳ hep-exnucl-exNPA(2021)·2 citations
6. 06*

   Constraints on the muon fraction and density profile in neutron stars

   Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸

   Muons in neutron stars (NSs) play especially important roles in addressing several interesting new physics questions associated with detecting as well as understanding interactions and astrophysical effects of muonphilic dark matter particles. The key model inputs for studying the latter are the total muon mass $M_{\mu }$, the muon mass fraction $M_{\mu }/M_{\mathrm{NS}}$ over the NS mass $M_{\mathrm{NS}}$ and the muon radial density profile ${\rho }_{\mu }(r)$ in NSs of varying masses. We investigate these quantities within a minimum model for the core of NSs consisting of neutrons, protons, electrons, and muons using an explicitly isospin-dependent parametric Equation of State (EOS) constrained by available nuclear laboratory experiments and the latest astrophysical observations of NS masses, radii and tidal deformabilities. We found that the absolutely maximum muon mass $M_{\mu }$ and its mass fraction $M_{\mu }/M_{\mathrm{NS}}$ in the most massive NSs allowed by causality are about 0.025 $M_{\odot }$ and 1.1\%, respectively. For the most massive NS of mass 2.14 $M_{\odot }$ observed so far, they reduce to about 0.020 $M_{\odot }$ and 0.9\%, respectively. We also study respective effects of individual parameters describing the EOS of high-density neutron-rich nucleonic matter on the muon contents in NSs with varying masses. We found that the most important but uncertain nuclear physics ingredient for determining the muon contents in NSs is the high-density nuclear symmetry energy.

   ↳ astro-ph.HEnucl-exnucl-thApJ(2020)·38 citations
7. 07*

   Neutron star matter equation of state including $d^{\ast }$-hexaquark degrees of freedom

   A. Mantziris🇬🇧 · A. Pastore🇬🇧 · I. Vidaña🇮🇹 · D. P. Watts🇬🇧 · M. Bashkanov🇬🇧 · A. M. Romero🇬🇧

   We present an extension of a previous work where, assuming a simple free bosonic gas supplemented with a relativistic meand field model to describe the pure nucleonic part of the EoS, we studied the consequences that the first non-trivial hexaquark $d^{\ast }$(2380) could have on the properties of neutron stars. Compared to that exploratory work we employ a standard non-linear Walecka model including additional terms that describe the interaction of the $d^{\ast }(2380)$ di-baryon with the other particles of the system through the exchange of $\sigma$- and $\omega$-meson fields. Our results have show that the presence of the $d^{\ast }(2380)$ leads to maximum masses compatible with the recent observations of $\sim 2$M${}_{\odot }$ millisecond pulsars if the interaction of the $d^{\ast }(2380)$ is slightly repulsive or the $d^{\ast }(2380)$ does not interacts at all. An attractive interaction makes the equation of state too soft to be able to support a $2$M${}_{\odot }$ neutron star whereas an extremely repulsive one induces the collapse of the neutron star into a black hole as soon as the $d^{\ast }(2380)$ appears.

   ↳ nucl-thnucl-exAstron.Astrophys.(2020)·10 citations
8. 08*

   Monitoring the build-up of hydrogen polarization for polarized Hydrogen-Deuteride (HD) targets with NMR at 17 Tesla

   T. Ohta🇯🇵 · M. Fujiwara🇯🇵 · T. Hotta🇯🇵 · I. Ide🇯🇵 · K. Ishizaki🇯🇵 · H. Kohri🇯🇵 · Y. Yanai🇯🇵 · M. Yosoi🇯🇵

   We report on the frozen-spin polarized hydrogen--deuteride (HD) targets for photoproduction experiments at SPring-8/LEPS. Pure HD gas with a small amount of ortho-H2 (~0.1%) was liquefied and solidified by liquid helium. The temperature of the produced solid HD was reduced to about 30 mK with a dilution refrigerator. A magnetic field (17 T) was applied to the HD to grow the polarization with the static method. After the aging of the HD at low temperatures in the presence of a high-magnetic field strength for 3 months, the polarization froze. Almost all ortho-H2 molecules were converted to para-H2 molecules that exhibited weak spin interactions with the HD. If the concentration of the ortho-H2 was reduced at the beginning of the aging process, the aging time can be shortened. We have developed a new nuclear magnetic resonance (NMR) system to measure the relaxation times (T1) of the 1H and 2H nuclei with two frequency sweeps at the respective frequencies of 726 and 111 MHz, and succeeded in the monitoring of the polarization build-up at decreasing temperatures from 600 to 30 mK at 17 T. This technique enables us to optimize the concentration of the ortho-H2 and to efficiently polarize the HD target within a shortened aging time.

   ↳ physics.ins-detnucl-exRev.Sci.Instrum.(2020)·3 citations
9. 09*

   Calibration of MPD Electromagnetic Calorimeter with Muons

   A.Yu. Semenov🇷🇺 · I.A. Semenova🇷🇺 · M. Bhattacharjee🇷🇺 · A. Durum🇷🇺 · Yu. Krechetov🇷🇺 · V. Kulikov🇷🇺 · I. Mamonov🇷🇺 · M. Martemianov🇷🇺

   Shashlyk-type electromagnetic calorimeter (ECal) of the Multi-Purpose Detector at heavy-ion NICA collider is optimized to provide precise spatial and energy measurements for photons and electrons in the energy range from about 40 MeV to 2-3 GeV. To deal with high multiplicity of secondary particles from Au-Au reactions, ECal has a fine segmentation and consists of 38,400 cells ("towers"). Given the big number of "towers" and the time constraint, it is not possible to calibrate every ECal "tower" with beam. In this paper, we describe the strategy of the first-order calibration of ECal with cosmic muons.

   ↳ physics.ins-dethep-exnucl-exJINST(2020)·3 citations
10. 10*

    Model-independent determination of the nucleon charge radius from lattice QCD

    Constantia Alexandrou🇨🇾 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Konstantin Ottnad🇩🇪 · Marcus Petschlies🇩🇪

    Lattice QCD calculations of nucleon form factors are restricted to discrete values of the Euclidean four-momentum transfer. Therefore, the extraction of radii typically relies on parametrizing and fitting the lattice QCD data to obtain its slope close to zero momentum transfer. We investigate a new method, which allows to compute the nucleon radius directly from existing lattice QCD data, without assuming a functional form for the momentum dependence of the underlying form factor. The method is illustrated for the case of the isovector mean square charge radius of the nucleon $⟨r_{\mathrm{isov}}^2⟩$ and the quark-connected contributions to $⟨r_p^2⟩$ and $⟨r_n^2⟩$ for the proton and neutron, respectively. Computations are performed using a single gauge ensemble with $N_f=2+1+1$ maximally twisted mass clover-improved fermions at physical quark mass and a lattice spacing of $a=0.08\mathrm{fm}$.

    ↳ hep-lathep-phnucl-exnucl-thPRD(2020)·33 citations
11. 11*

    Effects of initial state fluctuations on the mean transverse momentum

    Fernando G. Gardim🇧🇷 · Giuliano Giacalone🇫🇷 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷

    We show that in ideal hydrodynamic simulations of heavy-ion collisions, initial state fluctuations result in an increase of the mean transverse momentum of outgoing hadrons, $⟨p_t⟩$. Specifically, $⟨p_t⟩$ is larger by a few percent if realistic fluctuations are implemented than with smooth initial conditions, the multiplicity and impact parameter being kept fixed. We show that result can be traced back to the fact that for a given total entropy, the initial energy contained in the fluid is larger if the density profile is bumpy. We discuss the implication of these results for the extraction of the equation of state of QCD from experimental data.

    ↳ nucl-thhep-phnucl-exNPA(2021)·26 citations
12. 12*

    Jet quenching in a multi-stage Monte Carlo approach

    A. Kumar🇺🇸 · A. Angerami🇺🇸 · S. A. Bass🇺🇸 · S. Cao🇺🇸 · Y. Chen🇺🇸 · J. Coleman🇺🇸 · L. Cunqueiro🇺🇸 · T. Dai🇺🇸 · L. Du🇺🇸 · R. Ehlers🇺🇸 · H. Elfner🇩🇪 · D. Everett🇺🇸 and 38 other authors

    We present a jet quenching model within a unified multi-stage framework and demonstrate for the first time a simultaneous description of leading hadrons, inclusive jets, and elliptic flow observables which spans multiple centralities and collision energies. This highlights one of the major successes of the JETSCAPE framework in providing a tool for setting up an effective parton evolution that includes a high-virtuality radiation dominated energy loss phase (MATTER), followed by a low-virtuality scattering dominated (LBT) energy loss phase. Measurements of jet and charged-hadron $R_{AA}$ set strong constraints on the jet quenching model. Jet-medium response is also included through a weakly-coupled transport description.

    ↳ nucl-thhep-phnucl-exNPA(2021)·11 citations
13. 13*

    Sterile neutrinos and neutrinoless double beta decay in effective field theory

    Wouter Dekens🇺🇸 · Jordy de Vries🇺🇸 · Kaori Fuyuto🇺🇸 · Emanuele Mereghetti🇺🇸 · Guanghui Zhou🇺🇸

    We investigate neutrinoless double beta decay ($0\nu \beta \beta$) in the presence of sterile neutrinos with Majorana mass terms. These gauge-singlet fields are allowed to interact with Standard-Model (SM) fields via renormalizable Yukawa couplings as well as higher-dimensional gauge-invariant operators up to dimension seven in the Standard Model Effective Field Theory extended with sterile neutrinos. At the GeV scale, we use Chiral effective field theory involving sterile neutrinos to connect the operators at the level of quarks and gluons to hadronic interactions involving pions and nucleons. This allows us to derive an expression for $0\nu \beta \beta$ rates for various isotopes in terms of phase-space factors, hadronic low-energy constants, nuclear matrix elements, the neutrino masses, and the Wilson coefficients of higher-dimensional operators. The needed hadronic low-energy constants and nuclear matrix elements depend on the neutrino masses, for which we obtain interpolation formulae grounded in QCD and chiral perturbation theory that improve existing formulae that are only valid in a small regime of neutrino masses. The resulting framework can be used directly to assess the impact of $0\nu \beta \beta$ experiments on scenarios with light sterile neutrinos and should prove useful in global analyses of sterile-neutrino searches. We perform several phenomenological studies of $0\nu \beta \beta$ in the presence of sterile neutrinos with and without higher-dimensional operators. We find that non-standard interactions involving sterile neutrinos have a dramatic impact on $0\nu \beta \beta$ phenomenology, and next-generation experiments can probe such interactions up to scales of $\mathcal{O}(100)$ TeV.

    ↳ hep-phnucl-exnucl-thJHEP(2020)·117 citations
14. 14*

    Beta decays as sensitive probes of lepton flavor universality

    Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭

    Nuclear $\beta$ decays as well as the decay of the neutron are well-established low-energy probes of physics beyond the Standard Model (SM). In particular, with the axial-vector coupling of the nucleon $g_A$ determined from lattice QCD, the comparison between experiment and SM prediction is commonly used to derive constraints on right-handed currents. Further, in addition to the CKM element $V_{us}$ from kaon decays, $V_{ud}$ from $\beta$ decays is a critical input for the test of CKM unitarity. Here, we point out that the available information on $\beta$ decays can be re-interpreted as a stringent test of lepton flavor universality (LFU). In fact, we find that the ratio of $V_{us}$ from kaon decays over $V_{us}$ from $\beta$ decays (assuming CKM unitarity) is extremely sensitive to LFU violation (LFUV) in $W$-$\mu$-$\nu$ couplings thanks to a CKM enhancement by $(V_{ud}/V_{us}{)}^2\sim 20$. From this perspective, recent hints for the violation of CKM unitarity can be viewed as further evidence for LFUV, fitting into the existing picture exhibited by semi-leptonic $B$ decays and the anomalous magnetic moments of muon and electron. Finally, we comment on the future sensitivity that can be reached with this LFU violating observable and discuss complementary probes of LFU that may reach a similar level of precision, such as $\Gamma (\pi \to \mu \nu )/\Gamma (\pi \to e\nu )$ at the PEN and PiENu experiments or even direct measurements of $W\to \mu \nu$ at an FCC-ee.

    ↳ hep-phhep-exhep-latnucl-ex+1PRL(2020)·122 citations
15. 15*

    Characterization of High-Purity Germanium (Ge) Crystals for Developing Novel Ge Detectors

    M.-S. Raut🇺🇸 · H. Mei · D.-M. Mei · S. Bhattarai🇺🇸 · W.-Z. Wei🇺🇸 · R. Panda · P. Acharya🇺🇸 · G.-J. Wang🇺🇸

    High-purity germanium (HPGe) crystals are required to be well-characterized before being fabricated into Ge detectors. The characterization of HPGe crystals is often performed with the Hall Effect system, which measures the carrier concentration, the Hall mobility, and the electrical resistivity. The reported values have a strong dependence on the size of the ohmic contacts and the geometry of the samples used in conducting the Hall Effect measurements. We conduct a systematic study using four samples cut from the same location in a HPGe crystal made into different sized ohmic contacts or different geometries to study the variation of the measured parameters from the Hall Effect system. The results are compared to the C-V measurements provided by the Ge detector made from the same crystal. We report the systematic errors involved with the Hall Effect system and find a reliable technique that minimizes the systematic error to be only a few percent from the Hall Effect measurements.

    ↳ physics.ins-detcond-mat.mtrl-scihep-exnucl-exJINST(2020)·9 citations
16. 16*

    Investigation of the Electrical Conduction Mechanisms in P-type Amorphous Germanium (a-Ge) Used as a-Ge Contacts for Ge Detectors

    S. Bhattarai🇺🇸 · R. Panth🇺🇸 · W.-Z. Wei🇺🇸 · H. Mei🇺🇸 · D.-M. Mei🇺🇸 · M.S. Raut🇺🇸 · P. Acharya🇺🇸 · W.-J. Wang🇺🇸

    Electrical conduction mechanisms in the disordered material system is experimentally studied for p-type amorphous germanium (a-Ge) used for high-purity Ge detector contacts. The localization length and the hopping parameters in a-Ge are determined using the surface leakage current measured from three high-purity planar Ge detectors. The temperature-dependent hopping distance and hopping energy are obtained for a-Ge fabricated as the electrical contact materials for high-purity Ge planar detectors. As a result, we find that the hopping energy in a-Ge increases as temperature increases while the hopping distance in a-Ge decreases as temperature increases. The localization length of a-Ge is on the order of $2.13_{+0.07}^{-0.05}{A}^{\circ }$ to $5.07_{+2.58}^{-0.83}{A}^{\circ }$, depending on the density of states near the Fermi energy level within bandgap. Using these parameters, we predict that the surface leakage current from a Ge detector with a-Ge contacts can be much smaller than one yocto amp (yA) at helium temperature, suitable for rare-event physics searches.

    ↳ physics.ins-dethep-exnucl-exEPJC(2020)·6 citations
17. 17*

    Electromagnetic Calorimeter for MPD Spectrometer at NICA Collider

    A.Yu. Semenov🇷🇺 · S. Bazylev🇷🇺 · E. Belyaeva🇷🇺 · M. Bhattacharjee🇷🇺 · B. Dabrowska🇷🇺 · D. Egorov🇷🇺 · V. Golovatyuk🇷🇺 · Yu. Krechetov🇷🇺 · A. Shutov🇷🇺 · V. Shutov🇷🇺 · S. Sukhovarov🇷🇺 · A. Terletskiy🇷🇺 · I. Tyapkin🇷🇺

    The Multi-Purpose Detector (MPD) is designed to study a hot and dense baryonic matter formed in heavy-ion collisions at SQRT(sNN)=4-11 GeV at the NICA accelerator complex (Dubna, Russia). Large-sized electromagnetic calorimeter (ECal) of the MPD spectrometer will provide precise spatial and energy measurements for photons and electrons in the central pseudorapidity region of |eta|<1.2. The Shashlyk-type sampling structure of the ECal is optimized for the photons energy range from about 40 MeV to 2-3 GeV. Fine segmentation and projective geometry of the calorimeter allow to deal with high multiplicity of secondary particles from Au-Au reactions. In this talk, we report on a design, a construction status and expected parameters of the ECal.

    ↳ physics.ins-dethep-exnucl-exJINST(2020)·19 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.