Tue·May 19, 2020Tuesday·May 19, 2020

1. 01*

   Experimental study of the ${}^{11}\text{B}(p,3\alpha )\gamma$ reaction at $E_p=0.5-2.7$ MeV

   Oliver S. Kirsebom · Alan M. Howard · Michael Munch · Sanchit Sablok · Jacobus A. Swartz🇩🇰 · Hans O. U. Fynbo🇩🇰

   Our understanding of the low-lying resonance structure in ${}^{12}$C remains incomplete. We have used the ${}^{11}\text{B}(p,3\alpha )\gamma$ reaction at proton energies of $E_p=0.5-2.7$ MeV as a selective probe of the excitation region above the $3\alpha$ threshold in ${}^{12}$C. Transitions to individual levels in ${}^{12}$C were identified by measuring the 3$\alpha$ final state with a compact array of charged-particle detectors. Previously identified transitions to narrow levels were confirmed and new transitions to broader levels were observed for the first time. Here, we report cross sections, deduce partial $\gamma$-decay widths and discuss the relative importance of direct and resonant capture mechanisms.

   nucl-exEPJA(2020)·3 citations
2. 02*

   Role of chiral two-body currents in ${}^6$Li magnetic properties in light of a new precision measurement with the relative self-absorption technique

   U. Friman-Gayer🇩🇪 · C. Romig🇩🇪 · T. Hüther🇩🇪 · K. Albe · S. Bacca🇩🇪 · T. Beck🇩🇪 · M. Berger🇦🇹 · J. Birkhan · K. Hebeler🇩🇪 · O. J. Hernandez🇩🇪 · J. Isaak🇩🇪 · S. König🇩🇪 and 9 other authors

   A direct measurement of the decay width of the excited $0_1^{+}$ state of ${}^6$Li using the relative self-absorption technique is reported. Our value of ${\Gamma }_{\gamma ,0_1^{+}\to 1_1^{+}}=8.17(14{)}_{stat.}(11{)}_{syst.}\mathrm{eV}$ provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This enables a precision test of the impact of two-body currents that enter at next-to-leading order.

   nucl-exnucl-thPRL(2021)·25 citations
3. 03*

   Precision measurement of ${}^{210}$Bi $\beta$-spectrum

   I.E. Alekseev🇷🇺 · S.V. Bakhlanov🇷🇺 · A.V. Derbin🇷🇺 · I.S. Drachnev🇷🇺 · I.M. Kotina🇷🇺 · I.S. Lomskaya🇷🇺 · V.N. Muratova🇷🇺 · N.V. Niyazova🇷🇺 · D.A. Semenov🇷🇺 · M.V. Trushin🇷🇺 · E.V. Unzhakov🇷🇺

   The precision measurement of the $\beta -$spectrum shape for ${}^{210}$Bi (historically RaE) have been performed with a spectrometer based on semiconductor Si(Li) detector. This first forbidden non-unique transition has the transition form-factor strongly deviated from unity and knowledge of its spectrum would play an important role in low-background physics in presence of ${}^{210}$Pb background. The measured transition form-factor could be approximated as $S(W)=1+(-0.4363\pm 0.0037)W+(0.0523\pm 0.0010)W^2$, that is in good agreement with previous studies and has significantly increased parameter precision.

   nucl-exhep-exhep-phnucl-th+1PRC(2021)·12 citations
4. 04*

   Charged pion production in $\mathbf{Au}+\mathbf{Au}$ collisions at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}$ = 2.4$\mathbf{GeV}$

   J.Adamczewski-Musch · O.Arnold · C.Behnke · A.Belounnas · A.Belyaev · J.C.Berger-Chen · J.Biernat · A.Blanco · C.Blume · M.Boehmer · P.Bordalo · S.Chernenko and 116 other authors

   We present high-statistic data on charged pion emission from Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.4 GeV (corresponding to $E_{beam}$ = 1.23 A GeV) in four centrality classes in the range 0 - 40$\%$ of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the world data, but undershoot by $2.5\sigma$ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations.

   nucl-exEPJA(2020)·60 citations
5. 05*

   Determination of Beta Decay Ground State Feeding of Nuclei of Importance for Reactor Applications

   V. Guadilla🇪🇸 · J. L. Tain🇪🇸 · A. Algora🇪🇸 · J. Agramunt🇪🇸 · D. Jordan🇪🇸 · M. Monserrate🇪🇸 · A. Montaner-Pizá🇪🇸 · S. E. A. Orrigo🇪🇸 · B. Rubio🇪🇸 · E. Valencia🇪🇸 · J. A. Briz🇫🇷 · A. Cucoanes🇫🇷 and 32 other authors

   In $\beta$-decay studies the determination of the decay probability to the ground state of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed $\gamma$-ray emission. In this work we revisit the $4\pi \gamma -\beta$ method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the $\beta$-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large ground state branches. The method is relevant for nuclear structure studies as well. Pertinent formulae are revised and extended to the special case of $\beta$-delayed neutron emitters, and the robustness of the method is demonstrated with synthetic data. We apply it to a number of measured decays that serve as test cases and discuss the features of the method. Finally, we obtain ground state feeding intensities with reduced uncertainty for four relevant decays that will allow future improvements in antineutrino spectrum and decay heat calculations using the summation method.

   nucl-exPRC(2020)·11 citations
6. 06*

   Generic algorithm for multi-particle cumulants of azimuthal correlations in high energy nucleus collisions

   Zuzana Moravcova🇨🇿 · Kristjan Gulbrandsen🇩🇰 · You Zhou🇩🇰

   Multi-particle cumulants of azimuthal angle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions and the search for the QGP in small collision systems at RHIC and the LHC. However, only very few of them are available and have been studied in theoretical calculations and experimental measurements. In this paper, we present a generic recursive algorithm for multi-particle cumulants, which enables the calculation of arbitrary order multi-particle cumulants. Among them, the new 10-, 12-, 14-, and 16-particle cumulants of a single harmonic, named $c_n\{10\}$, $c_n\{12\}$, $c_n\{14\}$, and $c_n\{16\}$, and the corresponding $v_n$ coefficients, will be discussed for the first time. These new multi-particle cumulants can be readily used along with updates to the generic framework of multi-particle correlations to a very high order. Finally, we propose a particular series of mixed harmonic multi-particle cumulants, which measures the general correlations between any moments of different flow coefficients. The predictions of these new observables are shown based on an initial state model MC-Glauber, a toy Monte Carlo model, and the HIJING transport model for future comparisons between experimental data and theoretical model calculations. The study of these new multi-particle cumulants in heavy-ion collisions will significantly improve the understanding of the joint probability density function which involves both different harmonics of flow and also the symmetry planes. This will pave the way for more stringent constraints on the initial state and help to extract more precisely how the created hot and dense matter evolves. Meanwhile, the efforts applied to small systems could be very helpful in the understanding of the origin of the observed collectivity at RHIC and the LHC.

   ↳ nucl-thnucl-exPRC(2021)·42 citations
7. 07*

   Exact Relations for Two-Photon-Exchange Effect in Elastic $ep$ Scattering by Dispersion Relation and Hadronic Model

   Hui-Yun Cao🇨🇳 · Hai-Qing Zhou🇨🇳

   The two-photon-exchange (TPE) effect plays a key role to extract the form factors (FFs) of the proton. In this work, we present some exact properties on the TPE effect in the elastic $ep$ scattering based on four types of typical and general interactions. The possible kinematical singularities, the asymptotic behaviors and the branch cuts of the TPE amplitudes are analyzed. The analytic expressions clearly indicate some exact relations between the dispersion relation (DR) method and the hadronic model (HM) method. It suggests that the two methods should be modified to general forms, respectively. After the modifications the new forms give the same results. Furthermore, they automatically and correctly include the contributions due to the seagull interaction, the meson-exchange effect, the contact interactions and the off-shell effect. To analyze the elastic $e^{\pm }p$ scattering data sets, the new forms should be used.

   ↳ nucl-thhep-exhep-phnucl-exCPC(2021)·5 citations
8. 08*

   Two-photon decays and transition form factors of ${\pi }^0$, $\eta$, and ${\eta }^{\prime }$ in large-$N_c$ chiral perturbation theory

   Patricia Bickert🇩🇪 · Stefan Scherer🇩🇪

   We present a calculation of $P\to {\gamma }^{(\ast )}{\gamma }^{(\ast )}$ processes, where $P={\pi }^0,\eta ,{\eta }^{\prime }$, at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-$N_c$ chiral perturbation theory. The results are numerically evaluated successively at LO, NLO, and NNLO. The appearing low-energy constants are determined through fits to the available experimental data. We investigate the decay widths to real photons, the single-virtual transition form factors, and the widths of $P\to \gamma l^{+}{l}^{-}$, where $l=e,\mu$. Furthermore, we provide results for the slopes and curvatures of the transition form factors.

   ↳ hep-phnucl-exnucl-thPRD(2020)·16 citations
9. 09*

   Statistical Behavior of Lepton Pair Spectrum in Drell-Yan Process and Signal from Quark-Gluon Plasma in High Energy Collisions

   Xu-Hong Zhang🇨🇳 · Fu-Hu Liu🇨🇳

   We analyze the transverse momentum ($p_T$) spectra of lepton pairs ($\ell \bar{\ell }$) generated in the Drell-Yan process, as detected in proton-nucleus (pion-nucleus) and proton-(anti)proton collisions by ten collaborations over a center-of-mass energy ($\sqrt{s_{NN}}$ or $\sqrt{s}$ if in a simplified form) range from $\sim 20$ GeV to above 10 TeV. Three types of probability density functions (the convolution of two Lévy-Tsallis functions, the two-component Erlang distribution, and the convolution of two Hagedorn functions) are utilized to fit and analyze the $p_T$ spectra. The fit results are approximately in agreement with the collected experimental data. Consecutively, we obtained the variation law of related parameters as a function of $\sqrt{s}$ and invariant mass ($Q$). In the fit procedure, a given Lévy-Tsallis (or Hagedorn) function can be regarded as the probability density function of transverse momenta contributed by a single quark ($q$) or anti-quark ($\bar{q}$). The Drell-Yan process is then described by the statistical method.

   ↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2021)·1 citation
10. 10*

    Response of a Li-glass/multi-anode photomultiplier detector to focused proton and deuteron beams

    E. Rofors🇸🇪 · J. Pallon🇸🇪 · R. Al Jebali🇸🇪 · J.R.M. Annand🇬🇧 · L. Boyd🇬🇧 · M.J. Christensen🇸🇪 · U. Clemens🇩🇪 · S. Desert🇫🇷 · M. Elfman🇸🇪 · R. Engels🇩🇪 · K.G. Fissum🇸🇪 · H. Frielinghaus🇩🇪 and 17 other authors

    The response of a position-sensitive Li-glass based scintillation detector to focused beams of 2.5 MeV protons and deuterons has been investigated. The beams were scanned across the detector in 0.5 mm horizontal and vertical steps perpendicular to the beams. Scintillation light was registered using an 8 by 8 pixel multi-anode photomultiplier tube. The signal amplitudes were recorded for each pixel on an event-by-event basis. Several pixels generally registered considerable signals at each beam location. The number of pixels above set thresholds were investigated, with the optimization of the single-hit efficiency over the largest possible area as the goal. For both beams, at a threshold of ~50% of the mean of the full-deposition peak, ~80% of the events were registered in a single pixel, resulting in an effective position resolution of ~5 mm in X and Y.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·4 citations
11. 11*

    TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

    JUNO Collaboration: Angel Abusleme · Thomas Adam · Shakeel Ahmad · Sebastiano Aiello · Muhammad Akram · Nawab Ali · Fengpeng An · Guangpeng An · Qi An · Giuseppe Andronico · Nikolay Anfimov · Vito Antonelli and 580 other authors

    The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022.

    ↳ physics.ins-dethep-exnucl-ex175 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.