Tue·Jun 11, 2019Tuesday·June 11, 2019

1. 01*

   Investigation of potential ultra-low $Q$-value $\beta$-decay candidates ${}^{89}$Sr and ${}^{139}$Ba using Penning trap mass spectrometry

   R. Sandler🇺🇸 · G. Bollen🇺🇸 · N. D. Gamage · A. Hamaker🇺🇸 · C. Izzo🇨🇦 · D. Puentes🇺🇸 · M. Redshaw🇺🇸 · R. Ringle🇺🇸 · I. Yandow🇺🇸

   Background: Ultra-low $Q$-value $\beta$-decays are interesting processes to study with potential applications to nuclear $\beta$-decay theory and neutrino physics. While a number of potential ultra-low $Q$-value $\beta$-decay candidates exist, improved mass measurements are necessary to determine which are energetically allowed. Method: Penning trap mass spectrometry was used to determine the atomic mass of ${}^{89}$Y and ${}^{139}$La, from which $\beta$-decay $Q$-values for ${}^{89}$Sr and ${}^{139}$Ba were obtained to determine if there could be an ultra-low $Q$-value decay branch in the $\beta$-decay of ${}^{89}$Sr $\to$ ${}^{89}$Y or ${}^{139}$Ba $\to$ ${}^{139}$La. Results: The ${}^{89}$Sr $\to$ ${}^{89}$Y and ${}^{139}$Ba $\to$ ${}^{139}$La $\beta$-decay $Q$-values were measured to be $Q_{\mathrm{Sr}}$ = 1502.20(0.35) keV and $Q_{\mathrm{Ba}}$ = 2308.37(68) keV. These were compared to energies of excited states in ${}^{89}$Y at 1507.4(1) keV, and in ${}^{139}$La at 2310(19) keV and 2313(1) keV to determine $Q$-values of -5.20(37) keV for the potential ultra-low $\beta$-decay branch of ${}^{89}$Sr and -1.6(19.0) keV and -4.6(1.2) keV for those of ${}^{139}$Ba. Conclusion: The potential ultra-low $Q$-value decay branch of ${}^{89}$Sr to the ${}^{89}$Y (3/2${}^{-}$, 1507.4 keV) state is energetically forbidden and has been ruled out. The potential ultra-low $Q$-value decay branch of ${}^{139}$Ba to the 2313 keV state in ${}^{139}$La with unknown J${}^{\pi }$ has also been ruled out at the 4$\sigma$ level, while more precise energy level data is needed for the ${}^{139}$La (1/2${}^{+}$, 2310 keV) state to determine if an ultra-low $Q$-value $\beta$-decay branch to this state is energetically allowed.

   nucl-exPRC(2019)·15 citations
2. 02*

   Charge-dependent pair correlations relative to a third particle in $p$+Au and $d$+Au collisions at RHIC

   STAR collaboration

   Quark interactions with topological gluon configurations can induce chirality imbalance and local parity violation in quantum chromodynamics. This can lead to electric charge separation along the strong magnetic field in relativistic heavy-ion collisions -- the chiral magnetic effect (CME). We report measurements by the STAR collaboration of a CME-sensitive observable in $p$+Au and $d$+Au collisions at 200 GeV, where the CME is not expected, using charge-dependent pair correlations relative to a third particle. We observe strong charge-dependent correlations similar to those measured in heavy-ion collisions. This bears important implications for the interpretation of the heavy-ion data.

   nucl-exhep-exhep-phnucl-thPLB(2019)·56 citations
3. 03*

   Measurement of prompt D${}^0$, D${}^{+}$, D${}^{\ast +}$, and D${}_s^{+}$ production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The measurement of the production of prompt D${}^0$, D${}^{+}$, D${}^{\ast +}$, and D${}_s^{+}$ mesons in proton$-$lead (p$-$Pb) collisions at the centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, with an integrated luminosity of $292\pm 11$ $\mu$b${}^{-1}$, are reported. Differential production cross sections are measured at mid-rapidity ($-0.96<y_{\mathrm{cms}}<0.04$) as a function of transverse momentum ($p_{\mathrm{T}}$) in the intervals $0<p_{\mathrm{T}}<36$ GeV/$c$ for D${}^0$, $1<p_{\mathrm{T}}<36$ GeV/$c$ for D${}^{+}$ and D${}^{\ast +}$, and $2<p_{\mathrm{T}}<24$ GeV/$c$ for D${}_s^{+}$ mesons. For each species, the nuclear modification factor $R_{\mathrm{pPb}}$ is calculated as a function of $p_{\mathrm{T}}$ using a proton-proton (pp) reference measured at the same collision energy. The results are compatible with unity in the whole $p_{\mathrm{T}}$ range. The average of the non-strange D mesons $R_{\mathrm{pPb}}$ is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The $p_{\mathrm{T}}$ dependence of the D${}^0$, D${}^{+}$, and D${}^{\ast +}$ nuclear modification factors is also reported in the interval $1<p_{\mathrm{T}}<36$ GeV/$c$ as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the $p_{\mathrm{T}}$-differential cross sections of D${}^0$, D${}^{+}$, D${}^{\ast +}$, and D${}_s^{+}$ mesons are also reported. The D${}_s^{+}$ and D${}^{+}$ yields are compared as a function of the charged-particle multiplicity for several $p_{\mathrm{T}}$ intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties.

   nucl-exhep-exJHEP(2019)·124 citations
4. 04*

   Strange hadron production in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 7.7, 11.5, 19.6, 27, and 39 GeV

   STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · R. Aoyama🇯🇵 · A. Aparin🇷🇺 · D. Arkhipkin🇺🇸 and 340 other authors

   We present STAR measurements of strange hadron (${\mathrm{K}}_{\mathrm{S}}^0$, $\Lambda$, $\overline{\Lambda }$, ${\Xi }^{-}$, ${\overline{\Xi }}^{+}$, ${\Omega }^{-}$, ${\overline{\Omega }}^{+}$, and $\varphi$) production at mid-rapidity ($|y|<0.5$) in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 7.7 - 39 GeV from the Beam Energy Scan Program at the Relativistic Heavy Ion Collider (RHIC). Transverse momentum spectra, averaged transverse mass, and the overall integrated yields of these strange hadrons are presented versus the centrality and collision energy. Antibaryon-to-baryon ratios ($\overline{\Lambda }$/$\Lambda$, ${\overline{\Xi }}^{+}$/${\Xi }^{-}$, ${\overline{\Omega }}^{+}$/${\Omega }^{-}$) are presented as well, and used to test a thermal statistical model and to extract the temperature normalized strangeness and baryon chemical potentials at hadronic freeze-out (${\mu }_B/T_{\mathrm{ch}}$ and ${\mu }_S/T_{\mathrm{ch}}$) in central collisions. Strange baryon-to-pion ratios are compared to various model predictions in central collisions for all energies. The nuclear modification factors ($R_{\text{CP}}$) and antibaryon-to-meson ratios as a function of transverse momentum are presented for all collision energies. The ${\mathrm{K}}_{\mathrm{S}}^0$ $R_{\text{CP}}$ shows no suppression for $p_{\mathrm{T}}$ up to 3.5 $\mathrm{GeV}/c$ at energies of 7.7 and 11.5 GeV. The $\overline{\Lambda }$/${\mathrm{K}}_{\mathrm{S}}^0$ ratio also shows baryon-to-meson enhancement at intermediate $p_{\mathrm{T}}$ ($\approx$2.5 $\mathrm{GeV}/c$) in central collisions at energies above 19.6 GeV. Both observations suggest that there is likely a change of the underlying strange quark dynamics at collision energies below 19.6 GeV.

   nucl-exPRC(2020)·190 citations
5. 05*

   Discovery of ${}^{68}$Br in secondary reactions of radioactive beams

   K. Wimmer🇯🇵 · P. Doornenbal🇯🇵 · W. Korten🇫🇷 · T. Arici🇩🇪 · P. Aguilera🇨🇱 · A. Algora🇪🇸 · T. Ando🇯🇵 · H. Baba🇯🇵 · B. Blank🇫🇷 · A. Boso🇮🇹 · S. Chen🇯🇵 · A. Corsi🇫🇷 and 22 other authors

   The proton-rich isotope 68Br was discovered in secondary fragmentation reactions of fast radioactive beams. Proton-rich secondary beams of 70,71,72Kr and 70Br, produced at the RIKEN Nishina Center and identified by the BigRIPS fragment separator, impinged on a secondary 9Be target. Unambiguous particle identification behind the secondary target was achieved with the ZeroDegree spectrometer. Based on the expected direct production cross sections from neighboring isotopes, the lifetime of the ground or long-lived isomeric state of 68Br was estimated. The results suggest that secondary fragmentation reactions, where relatively few nucleons are removed from the projectile, offer an alternative way to search for new isotopes, as these reactions populate preferentially low-lying states.

   nucl-exPLB(2019)·7 citations
6. 06*

   Measurement of the single-spin asymmetry $A_y^0$ in quasi-elastic ${}^3$He${}^{\uparrow }$($e,e^{\prime }n$) scattering at $0.4<Q^2<1.0$ GeV$/c^2$

   E. Long🇺🇸 · Y.W. Zhang · M. Mihoviloviv · G. Jin🇺🇸 · V. Sulkosky🇺🇸 · A. Kelleher🇺🇸 · B. Anderson🇺🇸 · D.W. Higinbotham🇺🇸 · S. Sirca🇸🇮 · K. Allada🇺🇸 · J.R.M. Annand🇬🇧 · T. Averett🇺🇸 and 79 other authors

   Due to the lack of free neutron targets, studies of the structure of the neutron are typically made by scattering electrons from either ${}^2$H or ${}^3$He targets. In order to extract useful neutron information from a ${}^3$He target, one must understand how the neutron in a ${}^3$He system differs from a free neutron by taking into account nuclear effects such as final state interactions and meson exchange currents. The target single spin asymmetry $A_y^0$ is an ideal probe of such effects, as any deviation from zero indicates effects beyond plane wave impulse approximation. New measurements of the target single spin asymmetry $A_y^0$ at $Q^2$ of 0.46 and 0.96 (GeV/$c{)}^2$ were made at Jefferson Lab using the quasi-elastic ${}^3{\mathrm{He}}^{\uparrow }(e,e^{\prime }n)$ reaction. Our measured asymmetry decreases rapidly, from $>20\%$ at $Q^2=0.46$ (GeV/$c{)}^2$ to nearly zero at $Q^2=0.96$ (GeV$/c{)}^2$, demonstrating the fall-off of the reaction mechanism effects as $Q^2$ increases. We also observed a small $ϵ$-dependent increase in $A_y^0$ compared to previous measurements, particularly at moderate $Q^2$. This indicates that upcoming high $Q^2$ measurements from the Jefferson Lab 12 GeV program can cleanly probe neutron structure from polarized ${}^3$He using plane wave impulse approximation.

   nucl-exPLB(2019)·8 citations
7. 07*

   Production of ${\Lambda }_{\mathrm{c}}^{+}$ baryons in proton-proton and lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   The differential cross sections of ${\Lambda }_{\mathrm{c}}^{+}$ baryon production are measured via the exclusive decay channel ${\Lambda }_{\mathrm{c}}^{+}$ $\to$ pK${}^{-}{\pi }^{+}$ using the CMS detector at the LHC. Spectra are measured as a function of transverse momentum ($p_{\mathrm{T}}$) in proton-proton (pp) and lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measurement is performed within the ${\Lambda }_{\mathrm{c}}^{+}$ rapidity interval $|y|$ $<$ 1.0 in the $p_{\mathrm{T}}$ range of 5-20 GeV/$c$ in pp and 10-20 GeV/$c$ in PbPb collisions. The observed yields of ${\Lambda }_{\mathrm{c}}^{+}$ for $p_{\mathrm{T}}$ of 10-20 GeV/$c$ suggest a possible suppression in central PbPb collisions compared to pp collisions scaled by the number of nucleon-nucleon (NN) interactions. The ${\Lambda }_{\mathrm{c}}^{+}/$D${}^0$ production ratio in pp collisions is compared to theoretical models. In PbPb collisions, this ratio is consistent with the result from pp collisions in their common $p_{\mathrm{T}}$ range.

   ↳ hep-exnucl-exPLB(2020)·108 citations
8. 08*

   Sensitivity of the excitation functions of collective flow to relativistic scalar and vector meson interactions in the relativistic quantum molecular dynamics model RQMD.RMF

   Yasushi Nara🇯🇵 · Horst Stoecker🇩🇪

   Relativistic quantum molecular dynamics with scalar and vector interactions based on the relativistic mean meson field theory, RQMD.RMF, is developed.It is implemented into the microscopic transport code JAM.The sensitivity of the directed and of the elliptic proton flow in high energy heavy-ion collisions on the stiffness of the RMF equation of state (EoS) is examined. These new calculations are compared to experimental data at mid-central Au + Au collisions in the beam energy range $2.5<\sqrt{s_{NN}}<20$ GeV. This new RQMD model with the relativistic mean field scalar and vector meson interactions does describe consistently, with one RMF parameter set,the beam energy dependence of both the directed flow and the elliptic flow,from SIS18 to AGS and RHIC BES-II energies, $\sqrt{s_{NN}}<10$ GeV.There are different sensitivities of these different kinds of flow to the EoS: elliptic flow is most sensitive to the nuclear incompressibility constant,at the moderate beam energies $\sqrt{s_{NN}}<3$ GeV,whereas the directed flow is most sensitive to the effective baryon mass at saturation density at $3<\sqrt{s_{NN}}<5$ GeV. Matters abruptly change in the next higher energy range,$\sqrt{s_{NN}}\gtrsim 10-20$ GeV:the directed flow data show a double change of sign of the slope of $v_1$, inverting twice in this energy range,in sudden contradiction to the RQMD.RMF calculation for a monotonous, stiff EoS. This surprising oscillating behavior,a double change of sign of the $v_1$ slope, points to the appearance of a hitherto unknown first-order phase transition in excited QCD matter at high baryon densities in mid-central Au + Au collisions.

   ↳ nucl-thhep-phnucl-exPRC(2019)·42 citations
9. 09*

   Fast neutron spectroscopy from 1 MeV up to 15 MeV with Mimac-FastN, a mobile and directional fast neutron spectrometer

   Nadine Sauzet🇫🇷 · Daniel Santos🇫🇷 · Olivier Guillaudin🇫🇷 · Germain Bosson🇫🇷 · Joël Bouvier🇫🇷 · Thierry Descombes🇫🇷 · Marc Marton🇫🇷 · Jean-François Muraz🇫🇷

   In the frame of direct dark matter search, the fast neutrons producing elastic collisions are the ultimate background. The MIMAC (MIcro-tpc MAtrix Chambers) project has developed a directional detector providing the directional signature to discriminate them based on 3D nuclear tracks reconstruction. The MIMAC team of the LPSC has adapted one MIMAC chamber as a portable fast neutron spectrometer, the Mimac-FastN detector, having a very large neutron energy range (10 keV - 600 MeV) with different gas mixtures and pressures. The present paper shows its main features and functionality and demonstrates its potential in the energy range from 1 MeV to 15 MeV at the GENESIS neutron source facility of LPSC.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·6 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.