Tue·Sep 11, 2018Tuesday·September 11, 2018

1. 01*

   Gamma Ray Spectrum from Thermal Neutron Capture on Gadolinium-157

   Kaito Hagiwara · Takatomi Yano · Tomoyuki Tanaka · Pretam Kumar Das · Sebastian Lorenz · Iwa Ou · Takashi Sudo · Mandeep Singh Reen · Yoshiyuki Yamada · Takaaki Mori · Tsubasa Kayano · Rohit Dir and 11 other authors

   We have measured the $\gamma$-ray energy spectrum from the thermal neutron capture, ${}^{157}$Gd$(n,\gamma ){}^{158}$Gd, on an enriched ${}^{157}$Gd target (Gd${}_2$O${}_3$) in the energy range from 0.11 MeV up to about 8 MeV. The target was placed inside the germanium spectrometer of the ANNRI detector at J-PARC and exposed to a neutron beam from the Japan Spallation Neutron Source (JSNS). Radioactive sources (${}^{60}$Co, ${}^{137}$Cs, and ${}^{152}$Eu) and the reaction ${}^{35}$Cl($n$,$\gamma$) were used to determine the spectrometer's detection efficiency for $\gamma$ rays at energies from 0.3 to 8.5 MeV. Using a Geant4-based Monte Carlo simulation of the detector and based on our data, we have developed a model to describe the $\gamma$-ray spectrum from the thermal ${}^{157}$Gd($n$,$\gamma$) reaction. While we include the strength information of 15 prominent peaks above 5 MeV and associated peaks below 1.6 MeV from our data directly into the model, we rely on the theoretical inputs of nuclear level density and the photon strength function of ${}^{158}$Gd to describe the continuum $\gamma$-ray spectrum from the ${}^{157}$Gd($n$,$\gamma$) reaction. Our model combines these two components. The results of the comparison between the observed $\gamma$-ray spectra from the reaction and the model are reported in detail.

   nucl-exhep-exphysics.ins-detPTEP(2019)·46 citations
2. 02*

   Consistent account of deuteron-induced reactions on Cr up to 60 MeV

   E. Simeckova · M. Avrigeanu🇷🇴 · U. Fischer · J. Mrazek🇨🇿 · J. Novak🇫🇷 · M. Stefanik · C. Costache🇷🇴 · V. Avrigeanu

   Purpose: Accurate new measurements of low-energy deuteron-induced reaction cross sections for natural Cr target can enhance the related database and the opportunity for an unitary and consistent account of the involved reaction mechanisms. Methods: The activation cross sections of ${}^{51,52,54}$Mn, ${}^{51}$Cr, and ${}^{48}$V nuclei for deuterons incident on natural Cr at energies up to 20 MeV, were measured by the stacked-foil technique and high resolution gamma spectrometry using U-120M cyclotron of the Center of Accelerators and Nuclear Analytical Methods (CANAM) of the Nuclear Physics Institute of the Czech Academy of Sciences (NPI CAS). They as well as formerly available data for deuteron interactions with Cr isotopes up to 60 MeV are the object of an extended analysis of all processes from elastic scattering until the evaporation from fully equilibrated compound system, but with a particular attention given to the BU and DR mechanisms. Results: The new measured activation excitation functions proved essential for the enrichment of the deuteron database, while the theoretical analysis of all available data strengthens for the first time their consistent account provided that (i) a suitable BU and DR assessment is completed by (ii) the assumption of PE and CN contributions corrected for decrease of the total-reaction cross section due to the leakage of the initial deuteron flux towards BU and DR processes. Conclusions: The suitable description of nuclear mechanisms involved within deuteron-induced reactions on chromium, taking into account especially the BU and DR direct processes, is validated by an overall agreement of the calculated and measured cross sections including particularly the new experimental data at low energies.

   nucl-exnucl-thPRC(2018)·11 citations
3. 03*

   Experimentally well-constrained masses of ${}^{27}$P and ${}^{27}$S: Implications for studies of explosive binary systems

   L. J. Sun · X. X. Xu🇨🇳 · S. Q. Hou🇺🇸 · C. J. Lin🇺🇸 · J. José🇪🇸 · J. Lee🇨🇳 · J. J. He🇨🇳 · Z. H. Li · J. S. Wang🇨🇳 · C. X. Yuan🇨🇳 · F. Herwig🇨🇦 · J. Keegans and 49 other authors

   The mass of ${}^{27}$P was predicted to impact the X-ray burst (XRB) model predictions of burst light curves and the composition of the burst ashes. To address the uncertainties and inconsistencies in the reported ${}^{27}$P masses in literature, a wealth of information has been extracted from the $\beta$-decay spectroscopy of the drip-line nucleus ${}^{27}$S. We determine the most precise mass excess of ${}^{27}$P to date to be $-659(9)$~keV, which is 63~keV (2.3$\sigma$) higher than the AME2016 recommended value of $-722(26)$~keV. The experimentally unknown mass excess of ${}^{27}$S was estimated to be 17030(400)~keV in AME2016, and we constrain this mass to be 17678(77)~keV based on the measured $\beta$-delayed two-proton energy. In the temperature region of $(0.06-0.3)$~GK, the ${}^{26}$Si$(p,\gamma {)}^{27}$P reaction rate determined in this work is significantly lower than the rate recommended in the reaction rate libraries, up to two orders of magnitude around 0.1~GK. The impact of these newly determined masses and well-constrained rate on the modeling of the explosive astrophysical scenarios has been explored by hydrodynamic nova and post-processing XRB models. No substantial change was found in the nova contribution to the synthesis of galactic ${}^{26}$Al or in the XRB energy generation rate, but we found that the calculated abundances of ${}^{26}$Al and ${}^{26}$Si at the last stage of XRB are increased by a factor of 2.4. We also conclude that ${}^{27}$S is not a significant waiting point in the rapid proton capture process.

   nucl-exPLB(2020)·21 citations
4. 04*

   Beta-decay spectroscopy of ${}^{27}$S

   L. J. Sun🇺🇸 · X. X. Xu🇨🇳 · S. Q. Hou🇺🇸 · C. J. Lin🇺🇸 · J. José🇪🇸 · J. Lee🇨🇳 · J. J. He🇨🇳 · Z. H. Li · J. S. Wang🇨🇳 · C. X. Yuan🇨🇳 · D. X. Wang🇨🇳 · H. Y. Wu🇨🇳 and 46 other authors

   Background: Beta-decay spectroscopy provides valuable nuclear physics input for thermonuclear reaction rates of astrophysical interest and stringent test for shell-model theories far from the stability line. Purpose: The available decay properties of proton drip-line nucleus ${}^{27}$S is insufficient to constrain the properties of the key resonance in ${}^{26}$Si$(p,\gamma {)}^{27}$P reaction rate and probe the possible isospin asymmetry. The decay scheme of ${}^{27}$S is complicated and far from being understood, which has motivated but also presented challenges for our experiment. Method: The ${}^{27}$S ions were implanted into a double-sided silicon strip detector array surrounded by the high-purity germanium detectors, where the $\beta$-delayed protons and $\gamma$ rays were measured simultaneously. Results: The improved spectroscopic properties including the precise half-life of ${}^{27}$S, the excitation energies, $\beta$-decay branching ratios, log~$ft$ values, and $B$(GT) values for the states of ${}^{27}$P populated in the $\beta$ decay of ${}^{27}$S were measured and compared to the ${}^{27}$Mg mirror states and the shell-model calculations. The present work has expanded greatly on the previously established decay scheme of ${}^{27}$S. Conclusions: The precise proton-separation energy of ${}^{27}$P, the energy and the ratio between $\gamma$ and proton partial widths of the $3/2^{+}$ resonance were obtained, thereby determining the ${}^{26}$Si$(p,\gamma {)}^{27}$P reaction rate based mainly on experimental constraints. The first evidence for the observation of a large isospin asymmetry for the mirror decays of ${}^{27}$S and ${}^{27}$Na is also provided. The experimental spectroscopic information can be reproduced by the shell-model calculation taking the weakly bound effect of the proton $1s_{1/2}$ orbit into account.

   nucl-exPRC(2019)·28 citations
5. 05*

   Charged jet cross section and fragmentation in proton-proton collisions at $\sqrt{s}$ = 7 TeV

   ALICE Collaboration

   We report the differential charged jet cross section and jet fragmentation distributions measured with the ALICE detector in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 7 TeV. Jets with pseudo-rapidity $\left|\eta \right|<0.5$ are reconstructed from charged particles using the anti-$k_{\mathrm{T}}$ jet finding algorithm with a resolution parameter $R$ = 0.4. The jet cross section is measured in the transverse momentum interval 5 $\le p_{\mathrm{T}}^{\mathrm{ch}\mathrm{jet}}<$ 100 GeV/$c$. Jet fragmentation is studied measuring the scaled transverse momentum spectra of the charged constituents of jets in four intervals of jet transverse momentum between 5 GeV/$c$ and 30 GeV/$c$. The measurements are compared to calculations from the PYTHIA model as well as next-to-leading order perturbative QCD calculations with POWHEG + PYTHIA8. The charged jet cross section is described by POWHEG for the entire measured range of $p_{\mathrm{T}}^{\mathrm{ch}\mathrm{jet}}$. For $p_{\mathrm{T}}^{\mathrm{ch}\mathrm{jet}}$ $>$ 40 GeV/$c$, the PYTHIA calculations also agree with the measured charged jet cross section. PYTHIA6 simulations describe the fragmentation distributions to 15%. Larger discrepancies are observed for PYTHIA8.

   nucl-exhep-exPRD(2019)·45 citations
6. 06*

   Energy dependence of exclusive $J/\psi$ photoproduction off protons in ultra-peripheral p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of $J/\psi$ vector mesons off proton targets in ultra-peripheral p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The e${}^{+}$e${}^{-}$ and ${\mu }^{+}{\mu }^{-}$ decay channels are used to measure the cross section as a function of the rapidity of the $J/\psi$ in the range $-2.5<y<2.7$, corresponding to an energy in the $\gamma$p centre-of-mass in the interval $40<W_{\gamma \mathrm{p}}<550$ GeV. The measurements, which are consistent with a power law dependence of the exclusive $J/\psi$ photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements.

   nucl-exhep-exEPJC(2019)·118 citations
7. 07*

   Evaluation of particle--anti-particle scaled correlation within effective models

   Andre Garcia🇧🇷 · Volker Koch🇺🇸 · Marcus Benghi Pinto🇧🇷

   Correlations and fluctuations of physical quantities are known to play an important role in phase transitions and critical phenomena. In recent years some experimental attempts were made in the scope of the Beam Energy Scan program to locate a possible critical point in the QCD phase diagram. In this work we use the Nambu--Jona-Lasinio model to investigate the off-diagonal quark susceptibility, which is related to the quark--anti-quark scaled correlation at the mean field level. We show that this correlation has a significant peak near the critical point and, therefore, may be a useful quantity to measure in experiment. We further study the effects of a repulsive vector coupling, which reduces the strength of the scaled correlation near the critical point.

   ↳ nucl-thhep-phnucl-exNPA(2020)·3 citations
8. 08*

   Squeezed back-to-back correlations of $K^{+}$$K^{-}$ in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV

   Yong Zhang🇨🇳 · Jing Yang🇨🇳 · WeiHua Wu🇨🇳

   We investigate the squeezed back-to-back correlations (BBC) of $K^{+}$$K^{-}$, caused by the mass modification of the particle in the dense medium formed in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV. Considering some kaons may be not affected by the medium, we further study the BBC functions of $K^{+}$$K^{-}$ when parts of all kaons have a mass-shift. Our results indicate that the BBC functions of $K^{+}$$K^{-}$ can be observed when only about 10$\%$ of all kaons have a mass-shift in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and the peripheral collisions of Au+Au at $\sqrt{s_{NN}}=62.4$ GeV. Since the BBC function is caused by the mass-shift due to the interaction between the particle and the medium, the successful detection of the BBC function indirectly marks that the dense medium has formed in these collision systems. We suggest to measure the BBC function of $K^{+}$$K^{-}$ experimentally in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV and peripheral collisions of Au+Au at $\sqrt{s_{NN}}=62.4$ GeV.

   ↳ nucl-thnucl-exCPC(2019)·1 citation
9. 09*

   Spectator partons contribution in the rapidity width of lamda in p+p collisions at various SPS and LHC energies

   Nur Hussain🇮🇳 · Banajit Barman🇮🇳 · Buddhadeb Bhattacharjee🇮🇳

   Pseudorapidity distributions of all primary charged particles produced in p+p collisions at various Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies using UrQMD-3.4 and PYTHIA8.2-generated events are estimated and compared with the existing results of UA5 and ALICE collaborations. With both the sets of generated data, the variation of rapidity widths with the rest masses of different mesons and baryons of p+p collisions at various Super Proton Synchrotron (SPS) and LHC energies are presented. An increase in the width of the rapidity distribution of lambda, similar to heavy-ion data, could be seen in p+p collisions as well from SPS to the LHC energies (up to {sqrt_s} =13 TeV) when the entire rapidity space is considered, indicating its universal feature both in p+p and A+A collisions. The genesis of the increased width of rapidity distribution of Lambda in p+p collision is found to be in the production of light flavored quarks and diquarks from the spectator partons of the colliding hadrons resulting {lambda}/{anti_lambda}>1 at the extreme rapidities of the studied p+p collisions. At the LHC energies for central p+p collision, when there is no spectator partons, the rapidity width of {lambda} is found to take the same Gaussian shape as that of lambda and the widths of both the distributions become the same confirming no non-trivial contribution to the rapidity width of {lambda} as seen in heavy-ion and non-central p+p collisions.

   ↳ nucl-thnucl-ex2 citations
10. 10*

    Weak Neutral Current Axial Form Factor Using $(\bar{\nu })\nu$-Nucleon Scattering and Lattice QCD Inputs

    Raza Sabbir Sufian🇺🇸 · Keh-Fei Liu🇺🇸 · David G. Richards🇺🇸

    We present a determination of the neutral current weak axial charge $G_A^Z(0)=-0.654(3{)}_{\mathrm{stat}}(5{)}_{\mathrm{sys}}$ using the strange quark axial charge $G_A^s(0)$ calculated with lattice QCD. We then perform a phenomenological analysis, where we combine the strange quark electromagnetic form factor from lattice QCD with (anti)neutrino-nucleon scattering differential cross section from MiniBooNE experiments in a momentum transfer region $0.24\lesssim Q^2\lesssim 0.71$ GeV${}^2$ to determine the neutral current weak axial form factor $G_A^Z(Q^2)$ in the range of $0\lesssim Q^2\le 1$ GeV${}^2$. This yields a phenomenological value of $G_A^Z(0)=-0.687(89{)}_{\mathrm{stat}}(40{)}_{\mathrm{sys}}$. The value of $G_A^Z(0)$ constrained by the lattice QCD calculation of $G_A^s(0)$, when compared to its phenomenological determination, provides a significant improvement in precision and accuracy and can be used to provide a constraint on the fit to $G_A^Z(Q^2)$ for $Q^2>0$. This constrained fit leads to an unambiguous determination of (anti)neutrino-nucleon neutral current elastic scattering differential cross section near $Q^2=0$ and can play an important role in numerically isolating nuclear effects in this region. We show a consistent description of $G_A^Z(Q^2)$ obtained from the (anti)neutrino-nucleon scattering cross section data requires a nonzero contribution of the strange quark electromagnetic form factor. We demonstrate the robustness of our analysis by providing a post-diction of the BNL E734 experimental data.

    ↳ hep-phhep-latnucl-exnucl-thJHEP(2020)·17 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.