Tue·Jan 17, 2017Tuesday·January 17, 2017

1. 01*

   $\beta$-decay half-lives and $\beta$-delayed neutron emission probabilities for several isotopes of Au, Hg, Tl, Pb and Bi, beyond N=126

   R.Caballero-Folch🇪🇸 · C.Domingo-Pardo🇪🇸 · J.Agramunt🇪🇸 · A.Algora🇪🇸 · F.Ameil🇩🇪 · Y.Ayyad🇯🇵 · J.Benlliure🇪🇸 · M.Bowry🇬🇧 · F.Calviño🇪🇸 · D.Cano-Ott🇪🇸 · G.Cortès🇪🇸 · T.Davinson🇬🇧 and 49 other authors

   $Background:$ Previous measurements of $\beta$-delayed neutron emitters comprise around 230 nuclei, spanning from the ${}^8$He up to ${}^{150}$La. Apart from ${}^{210}$Tl, with a minuscule branching ratio of 0.007\%, no other neutron emitter is measured yet beyond $A=150$. Therefore new data are needed, particularly in the heavy mass region around N=126, in order to guide theoretical models and to understand the formation of the third r-process peak at $A\sim 195$. $Purpose:$ To measure both, $\beta$-decay half-lives and neutron branching ratios of several neutron-rich Au, Hg, Tl, Pb and Bi isotopes beyond $N=126$. $Method:$ Ions of interest are produced by fragmentation of a ${}^{238}$U beam, selected and identified via the GSI-FRS fragment separator. A stack of segmented silicon detectors (SIMBA) is used to measure ion-implants and $\beta$-decays. An array of 30 ${}^3$He tubes embedded in a polyethylene matrix (BELEN) is used to detect neutrons with high efficiency and selectivity. A self-triggered digital system is employed to acquire data and to enable time-correlations. The latter are analyzed with an analytical model and results for the half-lives and neutron-branching ratios are derived using the binned Maximum-Likelihood method. $Results:$ Twenty new $\beta$-decay half-lives are reported for ${}^{204-206}$Au, ${}^{208-211}$Hg,${}^{211-216}$Tl,${}^{215-218}$Pb and ${}^{218-220}$Bi, nine of them for the first time. Neutron emission probabilities are reported for ${}^{210,211}$Hg and ${}^{211-216}$Tl. $Conclusions:$ The new $\beta$-decay half-lives are in good agreement with previous measurements in this region. The measured neutron emission probabilities are comparable or smaller than values predicted by global models like RHB+RQRPA.

   nucl-exPRC(2017)·30 citations
2. 02*

   Ultrarelativistic heavy ion collisions: the first billion seconds

   Gordon Baym🇺🇸

   I first review the early history of the ultrarelativistic heavy ion program, starting with the 1974 Bear Mountain Workshop, and the 1983 Aurora meeting of the U.S. Nuclear Science Committee, just one billion seconds ago, which laid out the initial science goals of an ultrarelativistic collider. The primary goal, to discover the properties of nuclear matter at the highest energy densities, included finding new states of matter -- the quark-gluon plasma primarily -- and to use collisions to open a new window on related problems of matter in cosmology, neutron stars, supernovae, and elsewhere. To bring out how the study of heavy ions and hot, dense matter in QCD has been fulfilling these goals. I concentrate on a few topics, the phase diagram of matter in QCD, and connections of heavy ion physics to cold atoms, cosmology, and neutron stars.

   nucl-exnucl-thNPA(2016)·23 citations
3. 03*

   High-precision mass measurements for the isobaric multiplet mass equation at A = 52

   D.A. Nesterenko🇩🇪 · A. Kankainen🇫🇮 · L. Canete · M. Block🇺🇸 · D. Cox · T. Eronen🇫🇮 · C. Fahlander · U. Forsberg · J. Gerl🇩🇪 · P. Golubev🇸🇪 · J. Hakala🇫🇮 · A. Jokinen and 12 other authors

   Masses of ${}^{52}$Co, ${}^{52}$Co${}^m$, ${}^{52}$Fe, ${}^{52}$Fe${}^m$, and ${}^{52}$Mn have been measured with the JYFLTRAP double Penning trap mass spectrometer. Of these, ${}^{52}$Co and ${}^{52}$Co${}^m$ have been experimentally determined for the first time and found to be more bound than predicted by extrapolations. The isobaric multiplet mass equation for the $T=2$ quintet at $A=52$ has been studied employing the new mass values. No significant breakdown (beyond the $3\sigma$ level) of the quadratic form of the IMME was observed (${\chi }^2/n=2.4$). The cubic coefficient was 6.0(32) keV (${\chi }^2/n=1.1$). The excitation energies for the isomer and the $T=2$ isobaric analogue state in ${}^{52}$Co have been determined to be 374(13) keV and 2922(13) keV, respectively. The $Q$ value for the proton decay from the $19/2^{-}$ isomer in ${}^{53}$Co has been determined with an unprecedented precision, $Q_p=1558.8(17)$ keV. The proton separation energies of ${}^{52}$Co and ${}^{53}$Ni relevant for the astrophysical rapid proton capture process have been experimentally determined for the first time. \end{abstract}

   nucl-exJ.Phys.G(2017)·17 citations
4. 04*

   Revealing long-range multi-particle collectivity in small collision systems via subevent cumulants

   Jiangyong Jia🇺🇸 · Mingliang Zhou🇺🇸 · Adam Trzupek🇵🇱

   Multi-particle azimuthal cumulants, often used to study collective flow in high-energy heavy-ion collisions, have recently been applied in small collision systems such as $pp$ and $p$+A to extract the second-order azimuthal harmonic flow $v_2$. Recent observation of four-, six- and eight-particle cumulants with "correct sign" $c_2\{4\}<0,c_2\{6\}>0,c_2\{8\}<0$ and approximate equality of the inferred single-particle harmonic flow, $v_2\{4\}\approx v_2\{6\}\approx v_2\{8\}$, have been used as strong evidence for a collective emission of all soft particles produced in the collisions. We show that these relations in principle could be violated due to the non-Gaussianity in the event-by-event fluctuation of flow and/or non-flow. Furthermore, we show, using $pp$ events generated with the PYTHIA model, that $c_2\{2k\}$ obtained with standard cumulant method are dominated by non-flow from dijets. An alternative cumulant method based on two or more $\eta$-separated subevents is proposed to suppress the dijet contribution. The new method is shown to be able to recover a flow signal as low as 4\% imposed on the PYTHIA events, independently of how the event activity class is defined. Therefore the subevent cumulant method offers a more robust way of studying collectivity based on the existence of long-range azimuthal correlations between multiple distinct $\eta$ ranges. The prospect of using the subevent cumulants to study collective flow in A+A collisions, in particular its longitudinal dynamics, is discussed.

   ↳ nucl-thnucl-exPRC(2017)·174 citations
5. 05*

   Compton suppression in BEGe detectors by digital pulse shape analysis

   Yuhao Mi🇨🇳 · Hao Ma🇨🇳 · Zhi Zeng🇨🇳 · Jianping Cheng🇨🇳 · Junli Li🇨🇳 · Hui Zhang🇨🇳

   A new method of pulse shape discrimination (PSD) for BEGe detectors is developed to suppress Compton-continuum by digital pulse shape analysis (PSA), which helps reduce the Compton background level in gamma ray spectrometry. A decision parameter related to the rise time of a pulse shape was presented. The method was verified by experiments using 60Co and 137Cs sources. The result indicated that the 60Co Peak to Compton ratio and the Cs-Peak to Co-Compton ratio could be improved by more than two and three times, respectively.

   ↳ physics.ins-detnucl-ex0 citations
6. 06*

   The Sun as a probe of Fundamental Physics and Cosmology

   Ilídio Lopes🇵🇹

   The high quality data provided by helioseismology, solar neutrino flux measurements, spectral determination of solar abundances, nuclear reactions rates coefficients among other experimental data, leads to the highly accurate prediction of the internal structure of the present Sun - the standard solar model. In this talk, I have discussed how the standard solar model, the best representation of the real Sun, can be used to study the properties of dark matter, for which two complementary approaches have been developed: - to limit the number of theoretical candidates proposed as the dark matter particles, this analysis complements the experimental search of dark matter, and - as a template for the study of the impact of dark matter in the evolution of stars, which possibly occurs for stellar populations formed in regions of high density of dark matter, such as stars formed in the centre of galaxies and the first generations of stars.

   ↳ astro-ph.COastro-ph.SRnucl-exnucl-thJ.Phys.Conf.Ser.(2016)·3 citations
7. 07*

   Production of ${\rho }^0$ meson with large $p_T$ at NLO in heavy-ion collisions

   Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳

   Production of large transverse momentum ${\rho }^0$ meson in high-energy nuclear collisions is investigated for the first time at the next-leading-order in the QCD improved parton model. The ${\rho }^0$ fragmentation functions (FFs) in vacuum at any scale $Q$ are obtained, by evolving a newly developed initial parametrization of ${\rho }^0$ FFs at a scale ${\mathrm{Q}}_0^2=1.5\mathrm{Ge}{\mathrm{V}}^2$ from a broken SU(3) model through NLO DGLAP equations. The numerical simulations of $p_{\mathrm{T}}$ spectra of ${\rho }^0$ meson in the elementary $\mathrm{p}+\mathrm{p}$ collisions at NLO give a decent description of STAR $\mathrm{p}+\mathrm{p}$ data. In $\mathrm{A}+\mathrm{A}$ reactions the jet quenching effect is taken into account with the higher-twist approach by the medium-modified parton FFs due to gluon radiation in the quark-gluon plasma, whose space-time evolution is described by a (3+1D) hydrodynamical model. The nuclear modification factors for ${\rho }^0$ meson and its double ratio with ${\pi }^{\pm }$ nuclear modification in central $\mathrm{Au}+\mathrm{Au}$ collisions at the RHIC are calculated and found to be in good agreement with STAR measurement. Predictions of ${\rho }^0$ nuclear modification and the yield ratio ${\rho }^0/{\pi }^0$ in central Pb+Pb at the LHC are also presented. It is shown that the ratio ${\rho }^0/{\pi }^0$ in central Pb+Pb will approach to that in p+p reactions when $p_{\mathrm{T}}>12$~GeV.

   ↳ nucl-thnucl-exPRC(2018)·10 citations
8. 08*

   The QCD Equation of State to $\mathcal{O}({\mu }_B^6)$ from Lattice QCD

   A. Bazavov🇺🇸 · H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · O. Kaczmarek🇩🇪 · F. Karsch🇩🇪 · E. Laermann🇩🇪 · Y. Maezawa🇯🇵 · S. Mukherjee🇺🇸 · H. Ohno🇯🇵 · P. Petreczky🇺🇸 · H. Sandmeyer🇩🇪 · P. Steinbrecher🇩🇪 and 4 other authors

   We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon, strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range $T\in [135\mathrm{MeV},330\mathrm{MeV}]$ using up to four different sets of lattice cut-offs corresponding to lattices of size $N_{\sigma }^3\times N_{\tau }$ with aspect ratio $N_{\sigma }/N_{\tau }=4$ and $N_{\tau }=6-16$. The strange quark mass is tuned to its physical value and we use two strange to light quark mass ratios $m_s/m_l=20$ and $27$, which in the continuum limit correspond to a pion mass of about $160$ MeV and $140$ MeV espectively. Sixth-order results for Taylor expansion coefficients are used to estimate truncation errors of the fourth-order expansion. We show that truncation errors are small for baryon chemical potentials less then twice the temperature (${\mu }_B\le 2T$). The fourth-order equation of state thus is suitable for the modeling of dense matter created in heavy ion collisions with center-of-mass energies down to $\sqrt{s_{NN}}\sim 12$ GeV. We provide a parametrization of basic thermodynamic quantities that can be readily used in hydrodynamic simulation codes. The results on up to sixth order expansion coefficients of bulk thermodynamics are used for the calculation of lines of constant pressure, energy and entropy densities in the $T$-${\mu }_B$ plane and are compared with the crossover line for the QCD chiral transition as well as with experimental results on freeze-out parameters in heavy ion collisions. These coefficients also provide estimates for the location of a possible critical point. We argue that results on sixth order expansion coefficients disfavor the existence of a critical point in the QCD phase diagram for ${\mu }_B/T\le 2$ and $T/T_c({\mu }_B=0)>0.9$.

   ↳ hep-lathep-phnucl-exnucl-thPRD(2017)·586 citations
9. 09*

   Investigating the impact of the gluon saturation effects on the momentum transfer distributions for the exclusive vector meson photoproduction in hadronic collisions

   V. P. Goncalves🇧🇷 · F. S. Navarra🇧🇷 · D. Spiering🇧🇷

   The exclusive vector meson production cross section is one of the most promising observables to probe the high energy regime of the QCD dynamics. In particular, the squared momentum transfer ($t$) distributions are an important source of information about the spatial distribution of the gluons in the hadron and about fluctuations of the color fields. In this paper we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the $t$ - spectrum measured in exclusive $\rho$, $\varphi$ and $J/\Psi$ photoproduction in $pp$ and $PbPb$ collisions at the LHC. We compute the differential cross sections taking into account gluon saturation effects and compare the predictions with those obtained in the linear regime of the QCD dynamics. Our results show that gluon saturation suppresses the magnitude of the cross sections and shifts the position of the dips towards smaller values of $t$.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2017)·25 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.