Fri·Jun 1, 2018Friday·June 1, 2018

1. 01*

   "${\text{K}}^{-}\text{p}\text{p}$", a $\overline{K}$-Meson Nuclear Bound State, Observed in ${}^3\mathrm{He}(K^{-},\Lambda p)n$ Reactions

   J-PARC E15 collaboration · S. Ajimura · H. Asano · G. Beer · C. Berucci · H. Bhang · M. Bragadireanu · P. Buehler · L. Busso · M. Cargnelli · S. Choi · C. Curceanu and 58 other authors

   We observed a distinct peak in the $\Lambda p$ invariant mass spectrum of ${}^3\mathrm{He}(K^{-},\Lambda p)n$, well below the mass threshold of $m_K+2m_p$. By selecting a relatively large momentum-transfer region $q=350\sim 650$ MeV/$c$, one can clearly separate the peak from the quasi-free process, $\overline{K}N\to \overline{K}N$ followed by the non-resonant absorption by the two spectator-nucleons $\overline{K}NN\to \Lambda N$. We found that the simplest fit to the observed peak gives us a Breit-Wigner pole position at $B_{Kpp}=47\pm 3(stat.){}_{-6}^{+3}(sys.)$ MeV having a width ${\Gamma }_{Kpp}=115\pm 7(stat.){}_{-9}^{+10}(sys.)$ MeV, and the $S$-wave Gaussian reaction form-factor parameter $Q_{Kpp}=381\pm 14(stat.){}_{-0}^{+57}(sys.)$ MeV/$c$, as a new form of the nuclear bound system with strangeness -- "$K^{-}pp$".

   nucl-exPLB(2019)·86 citations
2. 02*

   Dispersive Corrections to the Born Approximation in Elastic Electron-Nucleus Scattering in the Intermediate Energy Regime

   P. Gueye · A. A. Kabir J. Glister · B. W. Lee · R. Gilman · D. W. Higinbotham · E. Piasetzky · G. Ron · A. J. Sarty · S. Strauch · A. Adeyemi · K. Allada · W. Armstrong and 80 other authors

   Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of 12C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of 12C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.

   nucl-exnucl-thEPJA(2020)·9 citations
3. 03*

   p-p, p-$\Lambda$ and $\Lambda$-$\Lambda$ correlations studied via femtoscopy in pp reactions at $\sqrt{s}$ = 7 TeV

   ALICE Collaboration

   We report on the first femtoscopic measurement of baryon pairs, such as p-p, p-$\Lambda$ and $\Lambda$-$\Lambda$, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at $\sqrt{s}$ = 7 TeV. This study demonstrates the feasibility of such measurements in pp collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p-p, p-$\Lambda$ and $\Lambda$-$\Lambda$ correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems 'Correlation Analysis Tool using the Schrödinger Equation' (CATS). Within the assumption that in pp collisions the three particle pairs originate from a common source, its radius is found to be equal to $r_0=1.125\pm 0.018$ (stat) ${}_{-0.035}^{+0.058}$ (syst) fm. The sensitivity of the measured p-$\Lambda$ correlation is tested against different scattering parameters which are defined by the interaction among the two particles, but the statistics is not sufficient yet to discriminate among different models. The measurement of the $\Lambda$-$\Lambda$ correlation function constrains the phase space spanned by the effective range and scattering length of the strong interaction. Discrepancies between the measured scattering parameters and the resulting correlation functions at LHC and RHIC energies are discussed in the context of various models.

   nucl-exhep-exPRC(2019)·212 citations
4. 04*

   Experimental and theoretical study of deuteron-proton elastic scattering for proton kinetic energies between $T_p=882.2\text{MeV}$ and $T_p=918.3\text{MeV}$

   C. Fritzsch🇩🇪 · S. Barsov🇷🇺 · I. Burmeister🇩🇪 · S. Dymov🇩🇪 · R. Gebel🇩🇪 · M. Hartmann🇩🇪 · A. Kacharava🇩🇪 · A. Khoukaz🇩🇪 · V. Komarov🇷🇺 · P. Kulessa🇵🇱 · A. Kulikov🇷🇺 · V. I. Kukulin🇷🇺 and 15 other authors

   New precise unpolarised differential cross sections of deuteron-proton elastic scattering have been measured at 16 different deuteron beam momenta between $p_d=3120.17\text{MeV}/c$ and $p_d=3204.16\text{MeV}/c$ at the COoler SYnchrotron COSY of the Forschungszentrum Jülich. The data, which were taken using the magnetic spectrometer ANKE, cover the equivalent range in proton kinetic energies from $T_p=882.2\text{MeV}$ to $T_p=918.3\text{MeV}$. The experimental results are analysed theoretically using the Glauber diffraction model with accurate nucleon-nucleon input. The theoretical cross section at $T_p=900\text{MeV}$ agrees very well with the experimental one at low momentum transfers $|t|<0.2(\text{GeV}/c{)}^2$.

   nucl-exnucl-thPLB(2018)·3 citations
5. 05*

   Muon-induced background in the KATRIN main spectrometer

   K. Altenmüller🇩🇪 · M. Arenz🇩🇪 · W.-J. Baek🇩🇪 · M. Beck🇩🇪 · A. Beglarian🇩🇪 · J. Behrens🇩🇪 · T. Bergmann🇩🇪 · A. Berlev🇷🇺 · U. Besserer🇩🇪 · K. Blaum🇩🇪 · S. Bobien🇩🇪 · T. Bode🇩🇪 and 122 other authors

   The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to make a model-independent determination of the effective electron antineutrino mass with a sensitivity of 0.2 eV/c${}^2$. It investigates the kinematics of $\beta$-particles from tritium $\beta$-decay close to the endpoint of the energy spectrum. Because the KATRIN main spectrometer (MS) is located above ground, muon-induced backgrounds are of particular concern. Coincidence measurements with the MS and a scintillator-based muon detector system confirmed the model of secondary electron production by cosmic-ray muons inside the MS. Correlation measurements with the same setup showed that about $12\%$ of secondary electrons emitted from the inner surface are induced by cosmic-ray muons, with approximately one secondary electron produced for every 17 muon crossings. However, the magnetic and electrostatic shielding of the MS is able to efficiently suppress these electrons, and we find that muons are responsible for less than $17\%$ ($90\%$ confidence level) of the overall MS background.

   ↳ physics.ins-detnucl-exAstropart.Phys.(2019)·25 citations
6. 06*

   First-forbidden transitions in the reactor anomaly

   L. Hayen🇧🇪 · J. Kostensalo🇫🇮 · N. Severijns🇧🇪 · J. Suhonen🇫🇮

   We study the dominant forbidden transitions in the antineutrino spectra of the fission actinides from 4 MeV onward using the nuclear shell model. Through explicit calculation of the shape factor, taking into account Coulomb corrections, we show the expected changes on cumulative electron and antineutrino spectra. Compared to the usual allowed approximation this results in a minor decrease of electron spectra from 4 MeV and onward, whereas an increase of several percent is observed in antineutrino spectra. We show that, despite their limited number, forbidden transitions dominate the spectral flux for most of the experimentally accessible range. Based on the shell model calculations we attempt a parametrization of forbidden transitions and propose a spectral correction for all forbidden transitions. We enforce correspondence with the ILL dataset using a summation+conversion approach. When compared against modern reactor neutrino experiments, the resultant spectral change is observed to be of comparable magnitude and shape as the reported spectral shoulder, drastically decreasing the statistical significance of the latter.

   ↳ nucl-thnucl-exPhys. Rev. C 100, 054323 (2019)·5 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.