Wed·Nov 6, 2019Wednesday·November 6, 2019

1. 01*

   Search for the $N$(1685) in $\eta \pi$-Photoproduction

   Dominik Werthmüller🇬🇧

   The nucleon-like member $N(1685)$ of the speculative baryon antidecuplet denotes one possible explanation for the narrow peak-structure around $W=1.68$ GeV observed in the total cross section of $\eta$-photoproduction off the neutron. If this baryon existed, it would likely to be seen in other reactions as well. While the aforementioned peak, whatever its nature is, was confirmed by several experiments, claims for signatures of the $N(1685)$ in other reactions and observables are mainly made by V. Kuznetsov et al. using GRAAL data. Their latest work suggests signals of both $N(1685)$ charge states in all isospin channels of $\eta \pi$-photoproduction off the proton and neutron. This contribution reports on challenging these claims with data from the A2 at MAMI experiment employing photon beam energies from $E_{\gamma }$=1.43-1.58 GeV. The $\eta {\pi }^{0}p$ and $\eta {\pi }^{+}n$ final states produced from a hydrogen target were studied and new analysis cuts were tested in order to enhance a possible signal.

   nucl-exnucl-thEPJ Web Conf.(2020)·1 citation
2. 02*

   Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay

   Heiko Saul🇩🇪 · Christoph Roick🇩🇪 · Hartmut Abele🇦🇹 · Holger Mest🇩🇪 · Michael Klopf🇦🇹 · Alexander Petukhov🇫🇷 · Torsten Soldner🇫🇷 · Xiangzun Wang🇦🇹 · Dominik Werder🇩🇪 · Bastian Märkisch🇩🇪

   In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Non-zero scalar or tensor interactions would imply an additional contribution to the differential decay rate of the neutron, the Fierz interference term. We derive a limit on this hypothetical term from a measurement using spin polarized neutrons. This method is statistically less sensitive than the determination from the spectral shape but features much cleaner systematics. We obtain a limit of b = 0.017(21) at 68.27 C.L., improving the previous best limit from neutron decay by a factor of four.

   nucl-exPRL(2020)·41 citations
3. 03*

   Studies of charm quark diffusion inside jets using PbPb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with $p_{\mathrm{T}}^{\mathrm{jet}}$ $>$ 60 GeV and D${}^0$ mesons with $p_{\mathrm{T}}^{\mathrm{D}}$ $>$ 4 GeV in lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV, recorded by the CMS detector at the LHC. The radial distribution of D${}^0$ mesons with respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in PbPb collisions. When compared to Monte Carlo event generators, the radial distribution in pp collisions is found to be well-described by PYTHIA, while the slope of the distribution predicted by SHERPA is steeper than that of the data. In PbPb collisions, compared to the pp results, the D${}^0$ meson distribution for 4 $<$ $p_{\mathrm{T}}^{\mathrm{D}}$ $<$ 20 GeV hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. At higher $p_{\mathrm{T}}^{\mathrm{D}}$, the PbPb and pp radial distributions are found to be similar.

   ↳ hep-exnucl-exPRL(2020)·39 citations
4. 04*

   Sensitivity of one-neutron knockout of halo nuclei to their nuclear structure

   Chloë Hebborn🇺🇸 · Pierre Capel🇩🇪

   Halo nuclei are located far from stability and exhibit a very peculiar structure. Due to their very short lifetime, they are often studied through reactions. Breakup reactions are of particular interest since their cross sections are large for these loosely-bound nuclei. Inclusive measurements of breakup--also called knockout reactions--have even higher statistics. In this proceeding, we study which nuclear-structure information can be inferred from the parallel-momentum distribution of the core of one-neutron halo nuclei after the knockout of its halo neutron. In particular, we analyse the influence of the ground-state wavefunction, the presence of excited states within the halo-nucleus spectrum and resonances in the core-neutron continuum. Our analysis shows that such observables are sensitive to the tail of the ground-state wavefunction. The presence of excited state decreases the breakup strength, and this flux is transferred to the inelastic-scattering channel. This indicates a conservation of the flux within each partial wave. We also show that the parallel-momentum distributions are insensitive to the existence of resonances within the continuum, they can thus be ignored in practice. This independence on the continuum argues that the parallel-momentum distributions are ideal observables to extract very precisely the ANCs of halo nuclei.

   ↳ nucl-thnucl-exJ.Phys.Conf.Ser.(2020)·2 citations
5. 05*

   On the effective theory of neutrino-electron and neutrino-quark interactions

   Richard J. Hill🇺🇸 · Oleksandr Tomalak🇺🇸

   We determine the four Fermi effective theory of neutrino interactions within the Standard Model including one-loop electroweak radiative corrections, in combination with the measured muon lifetime and precision electroweak data. Including two-loop matching and three-loop running corrections, we determine lepton coefficients accounting for all large logarithms through relative order $\mathcal{O}(\alpha {\alpha }_s)$ and quark coefficients accounting for all large logarithms through $\mathcal{O}(\alpha )$. We present four-fermion coefficients valid in $n_f=3$ and $n_f=4$ flavor quark theories, as well as in the extreme low-energy limit. We relate the coefficients in this limit to neutrino charge radii governing matter effects via forward neutrino scattering on charged particles.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2020)·39 citations
6. 06*

   Initial, effective, and kinetic freeze-out temperatures from transverse momentum spectra in high energy proton(deuteron)-nucleus and nucleus-nucleus collisions

   Muhammad Waqas🇨🇳 · Fu-Hu Liu🇨🇳

   The transverse momentum spectra of charged particles produced in proton(deuteron)-nucleus and nucleus-nucleus collisions at high energies are analyzed by the Hagedorn thermal model and the standard distribution in terms of multi-component. The experimental data measured in central and peripheral gold-gold (Au-Au) and deuteron-gold ($d$-Au) collisions by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC), as well as in central and peripheral lead-lead (Pb-Pb) and proton-lead ($p$-Pb) collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) are fitted by the two models. The initial, effective, and kinetic freeze-out temperatures are then extracted from the fitting to the transverse momentum spectra. It is shown that the initial temperature is larger than the effective temperature, and the effective temperature is larger than the kinetic freeze-out temperature. The three types of temperatures in central collisions are comparable with those in peripheral collisions, and those at the LHC are comparable with those at the RHIC.

   ↳ hep-phhep-exnucl-exnucl-thEur.Phys.J.Plus(2020)·44 citations
7. 07*

   $K^{\ast }(892{)}^0$ production in p+p interactions from NA61/SHINE

   Angelika Tefelska (for the NA61/SHINE Collaboration)🇵🇱

   The measurement of $K^{\ast }(892{)}^0$ resonance production via its $K^{+}{\pi }^{-}$ decay mode in inelastic p+p collisions at beam momenta 40--158 GeV/c ($\sqrt{s_{NN}}$=8.8--17.3 GeV) is presented. The data were recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The analysis of $K^{\ast }(892{)}^0$ was done with the template method. The results include the double differential spectra $d^{2}n/(dyd{p}_T)$, $d^{2}n/(m_{T}d{m}_{T}dy)$ as well as dn/dy spectra.

   ↳ hep-exnucl-exSpringer Proc.Phys.(2020)·0 citations
8. 08*

   Precise Determination of Neutrino Flux with Hadron Production Measurements

   Yoshikazu Nagai🇺🇸

   A precise prediction of the neutrino flux is a critical input for achieving the physics goals of accelerator-based neutrino experiments. In modern experiments, neutrino beams are created from the decays of secondary hadrons produced in hadron-nucleus interactions. Hadron production is the leading systematic uncertainty source on the neutrino flux prediction; therefore, its precise measurement is essential. In this proceedings, recent results and ongoing analyses of hadron production measurements by the NA61/SHINE experiment, as well as prospect for achievable precision on the flux predictions of T2K and Fermilab-based long-baseline neutrino experiments, will be presented. In addition, the necessity and prospects of further hadron production measurements by NA61/SHINE at CERN and the EMPHATIC experiment at Fermilab for the next generation neutrino experiments will be discussed.

   ↳ hep-exnucl-exphysics.ins-det0 citations
9. 09*

   Deep Learning Jet Substructure from Two-Particle Correlation

   Kai-Feng Chen🇹🇼 · Yang-Ting Chien🇺🇸

   Deciphering the complex information contained in jets produced in collider events requires a physical organization of the jet data. We introduce two-particle correlations (2PCs) by pairing individual particles as the initial jet representation from which a probabilistic model can be built. Particle momenta, as well as particle types and vertex information are included in the correlation. A novel, two-particle correlation neural network (2PCNN) architecture is constructed by combining neural network based filters on 2PCs and a deep neural network for capturing jet kinematic information. The 2PCNN is applied to boosted boson and heavy flavor tagging, and it achieves excellent performance by comparing to models based on telescoping deconstruction. Major correlation pairs exploited in the trained models are also identified, which shed light on the physical significance of certain jet substructure.

   ↳ hep-phhep-exnucl-exPRD(2020)·7 citations
10. 10*

    Diffusion of heavy quarks in the early stage of high-energy nuclear collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

    J. H. Liu🇨🇳 · S. Plumari🇮🇹 · S. K. Das🇮🇳 · V. Greco🇮🇹 · M. Ruggieri🇨🇳

    We study the diffusion of charm and beauty in the early stage of high energy nuclear collisions at RHIC and LHC energies, considering the interaction of these heavy quarks with the evolving Glasma by means of the Wong equations. In comparison with previous works, we add the longitudinal expansion as well as we estimate the effect of energy loss due to gluon radiation. We find that heavy quarks diffuse in the strong transverse color fields in the very early stage (0.2-0.3 fm/c) and this leads to a suppression at low $p_T$ and enhancement at intermediate low $p_T$. The shape of the observed nuclear suppression factor obtained within our calculations is in qualitative agreement with the experimental results of the same quantity for $D-$mesons in proton-nucleus collisions. We compute the nuclear suppression factor in nucleus-nucleus collisions as well, for both charm and beauty, finding a substantial impact of the evolving Glasma phase on these, suggesting that initialization of heavy quarks spectra in the quark-gluon plasma phase should not neglect the early evolution in the strong gluon fields.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2020)·40 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.