Tue·Feb 26, 2019Tuesday·February 26, 2019

1. 01*

   $\Lambda p$ Elastic Scattering in the CLAS Detector

   John W. Price (for the CLAS Collaboration)🇺🇸

   The elastic scattering process $\Lambda p\to \Lambda p$ offers insights on multiple problems in nuclear physics. $\mathrm{SU}(3{)}_F$ symmetry implies a close agreement between the $\Lambda p$ and $pp$ scattering cross sections. The $\Lambda p$ elastic scattering cross section can also illuminate the structure of neutron stars. A data-mining project was started using multiple CLAS data sets taken for other purposes with photon beams on a long liquid hydrogen target. A $\Lambda$ produced in a process such as $\gamma p\to K^{+}\Lambda$ can interact with a second proton inside the target before either decaying or leaving the target. The good angular acceptance and momentum resolution of CLAS make it well-suited for this type of analysis, even though it was not designed for such a measurement. The scattered $\Lambda$ can be identified from the ${\pi }^{-}p$ invariant mass. The four-vector of the initial $\Lambda$ is then reconstructed in the process $Xp\to \Lambda p$, which shows a strong peak at the $\Lambda$ mass with roughly twice the number of events as the existing world data sample. This observation opens up the possibility of other measurements using secondary beams of short-lived particles. This paper will discuss the current status of the analysis, and our plans for future work on this project.

   nucl-exAIP Conf.Proc.(2019)·4 citations
2. 02*

   Measurement of $\gamma$-ray production via the neutron-${}^{16}$O reaction using a 77 MeV quasi-monoenergetic neutron beam

   Y. Ashida · H. Nagata · M. Mori · G. Collazuol🇮🇹 · D. Fukuda🇯🇵 · T. Horai · F. Iacob · A. Konaka🇨🇦 · Y. Koshio🇯🇵 · T. Nakaya🇯🇵 · C. Nantais🇨🇦 · T. Shima🇯🇵 and 5 other authors

   Understanding of $\gamma$-ray production via neutron interactions on oxygen is essential for the study of neutrino neutral-current quasielastic interactions in water Cherenkov detectors. A measurement of $\gamma$-ray production from such reactions was performed using a 77~MeV quasi-monoenergetic neutron beam. Several $\gamma$-ray peaks, which are expected to come from neutron-${}^{16}\mathrm{O}$ reactions, are observed and production cross sections are measured for nine $\gamma$-ray components of energies between 2 and 8~MeV. These are the first measurements at this neutron energy using a nearly monoenergetic beam.

   nucl-exphysics.ins-detPRC(2024)·15 citations
3. 03*

   Cosmogenic production of ${}^{39}$Ar and ${}^{37}$Ar in argon

   R. Saldanha🇺🇸 · H.O. Back🇺🇸 · R.H.M. Tsang🇺🇸 · T. Alexander🇺🇸 · S.R. Elliott🇺🇸 · S. Ferrara🇨🇭 · E. Mace · C. Overman🇺🇸 · M.Zalavadia

   We have experimentally determined the production rate of ${}^{39}$Ar and ${}^{37}$Ar from cosmic ray neutron interactions in argon at sea level. Understanding these production rates is important for argon-based dark matter experiments that plan to utilize argon extracted from deep underground because it is imperative to know what the ingrowth of ${}^{39}$Ar will be during the production, transport, and storage of the underground argon. These measurements also allow for the prediction of ${}^{39}$Ar and ${}^{37}$Ar concentrations in the atmosphere which can be used to determine the presence of other sources of these isotopes. Through controlled irradiation with a neutron beam that mimics the cosmic ray neutron spectrum, followed by direct counting of ${}^{39}$Ar and ${}^{37}$Ar decays with sensitive ultra-low background proportional counters, we determined that the production rate from cosmic ray neutrons at sea-level is expected to be $(759\pm 128)$ atoms/kg${}_{\text{Ar}}$/day for ${}^{39}$Ar, and $(51.0\pm 7.4)$ atoms/kg${}_{\text{Ar}}$/day for ${}^{37}$Ar. We also performed a survey of the alternate production mechanisms based on the state-of-knowledge of the associated cross-sections to obtain a total sea-level cosmic ray production rate of $(1048\pm 133)$ atoms/kg${}_{\text{Ar}}$/day for ${}^{39}$Ar, $(56.7\pm 7.5)$ atoms/kg${}_{\text{Ar}}$/day for ${}^{37}$Ar in underground argon, and $(92\pm 13)$ atoms/kg${}_{\text{Ar}}$/day for ${}^{37}$Ar in atmospheric argon.

   nucl-exastro-ph.IMphysics.ins-detPRC(2019)·39 citations
4. 04*

   Multiplicity dependence of (anti-)deuteron production in pp collisions at $\sqrt{s}$ = 7 TeV

   ALICE Collaboration

   In this letter, the production of deuterons and anti-deuterons in pp collisions at $\sqrt{s}=7$ TeV is studied as a function of the charged-particle multiplicity density at mid-rapidity with the ALICE detector at the LHC. Production yields are measured at mid-rapidity in five multiplicity classes and as a function of the deuteron transverse momentum ($p_{\mathrm{T}}$). The measurements are discussed in the context of hadron-coalescence models. The coalescence parameter $B_2$, extracted from the measured spectra of (anti-)deuterons and primary (anti-)protons, exhibits no significant $p_{\mathrm{T}}$-dependence for $p_{\mathrm{T}}<3$ GeV/$c$, in agreement with the expectations of a simple coalescence picture. At fixed transverse momentum per nucleon, the $B_2$ parameter is found to decrease smoothly from low multiplicity pp Pb-Pb collisions, in qualitative agreement with more elaborate coalescence models. The measured mean transverse momentum of (anti-)deuterons in pp is not reproduced by the Blast-Wave model calculations that simultaneously describe pion, kaon and proton spectra, in contrast to central Pb-Pb collisions. The ratio between the $p_{\mathrm{T}}$-integrated yield of deuterons to protons, d/p, is found to increase with the charged-particle multiplicity, as observed in inelastic pp collisions at different centre-of-mass energies. The d/p ratios are reported in a wide range, from the lowest to the highest multiplicity values measured in pp collisions at the LHC.

   nucl-exhep-exPLB(2019)·83 citations
5. 05*

   Acoustic Rabi oscillations between gravitational quantum states and impact on symmetron dark energy

   Gunther Cronenberg🇦🇹 · Philippe Brax🇫🇷 · Hanno Filter🇦🇹 · Peter Geltenbort🇫🇷 · Tobias Jenke🇫🇷 · Guillaume Pignol🇫🇷 · Mario Pitschmann🇦🇹 · Martin Thalhammer🇦🇹 · Hartmut Abele🇦🇹

   The standard model of cosmology provides a robust description of the evolution of the universe. Nevertheless, the small magnitude of the vacuum energy is troubling from a theoretical point of view. An appealing resolution to this problem is to introduce additional scalar fields. However, these have so far escaped experimental detection, suggesting some kind of screening mechanism may be at play. Although extensive exclusion regions in parameter space have been established for one screening candidate - chameleon fields - another natural screening mechanism based on spontaneous symmetry breaking has also been proposed, in the form of symmetrons 11. Such fields would change the energy of quantum states of ultra-cold neutrons in the gravitational potential of the earth. Here we demonstrate a spectroscopic approach based on the Rabi resonance method that probes these quantum states with a resolution of E=2 x 10^(-15) eV. This allows us to exclude the symmetron as the origin of Dark Energy for a large volume of the three-dimensional parameter space.

   ↳ hep-phgr-qcnucl-exNat.Phys.(2018)·89 citations
6. 06*

   Octet baryon electromagnetic form factor double ratios $(G_E^{\ast }/G_M^{\ast })/(G_E/G_M)$ in a nuclear medium

   G. Ramalho🇧🇷 · J.P.B.C. de Melo🇧🇷 · K. Tsushima🇧🇷

   The ratios of the baryon electric ($G_E$) to magnetic ($G_M$) form factors, $G_E/G_M$, can provide us with important information on the structure of baryons in vacuum as demonstrated in recent studies for the proton and neutron systems. It has been argued that the corresponding in-medium ratios, $G_E^{\ast }/G_M^{\ast }$, can also provide useful information on the electromagnetic structure of baryons in a nuclear medium. Although the ratios may not be measured directly in experiments except for the proton at present, the double ratios $(G_E^{\ast }/G_M^{\ast })/(G_E/G_M)$ can be directly related to the polarization-transfer measurements of bound baryons. In the present work we estimate, for the first time, the double ratios $(G_E^{\ast }/G_M^{\ast })/(G_E/G_M)$ for all the members of octet baryons in symmetric nuclear matter in the range $Q^2=0$--3 GeV${}^2$, where $Q^2=-q^2$ with $q$ being the four-momentum transfer.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2019)·16 citations
7. 07*

   Charm-Baryon Production in Proton-Proton Collisions

   Min He🇨🇳 · Ralf Rapp🇺🇸

   Recent measurements of charm-baryon production in proton-proton collisions at the LHC have found a surprisingly large yield relative to those of $D$-mesons. We propose that this observation can be explained by the statistical hadronization model (SHM), by employing a largely augmented set of charm-baryon states beyond the current listings of the particle data group. We estimate the additional states using guidance from the relativistic quark model and from lattice QCD. Using charm- and strange-quark fugacity factors to account for the well-known suppression of heavy flavor in elementary collisions, we compute the yields and spectra of $D$, $D_s$ and ${\Lambda }_c$ hadrons in proton-proton collisions at $\sqrt{s}=5$\,TeV. Our main finding is that the enhanced feeddown from excited charm baryons can account for the ${\Lambda }_c/D^0$ ratio measured by ALICE at midrapidity, with some caveat for the forward-rapidity LHCb data. Furthermore, assuming independent fragmentation of charm quarks but with the hadronic ratios fixed by the SHM, the measured transverse-momentum ($p_T$) spectra of $D$-mesons and ${\Lambda }_c$ can also be described; in particular, the low-$p_T$ enhancement in the observed ${\Lambda }_c/D^0$ ratio is attributed to the enhanced feeddown from "missing" charm-baryon states. We comment on the implications of these findings for measurements of $D_s$ and ${\Lambda }_c$ in heavy-ion collisions.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2019)·173 citations
8. 08*

   Event Shape Sorting: prospects and femtoscopy applications

   Jakub Cimerman🇨🇿 · Boris Tomášik🇸🇰

   We demonstrate the use of Event Shape Sorting in femtoscopy. The method allows to select events with similar distributions if hadrons in azimuthal angle. We show that also their correlation radii exhibit interesting dependence on azimuthal angle with anisotropies of different orders visible at the same time. We further demonstrate such features of the hadron distribution which can be hardly recognised by Event Shape Engineering, but shows up in Event Shape Sorting. Finally, the influence of statistical fluctuations on sorting is investigated.

   ↳ nucl-thhep-phnucl-exPoS(2019)·0 citations
9. 09*

   Studies on photo- and electro-productions of $\Lambda (1405)$ via ${\gamma }^{(\ast )}p\to K^{\ast +}{\pi }^0{\Sigma }^0$

   Seung-il Nam🇰🇷 · Atsushi Hosaka🇯🇵

   We study the photo- and electro-productions of the vector kaon off the proton, i.e., ${\gamma }^{(\ast )}p\to K^{\ast +}{\pi }^0{\Sigma }^0$, and investigate the line shape of the ${\pi }^0{\Sigma }^0$ invariant mass in an effective Lagrangian approach with the inclusion of a $K^{\ast }N{\Lambda }^{\ast }$ interaction. Relevant electromagnetic form factors for the neutral hyperons and charged strange mesons are constructed by considering experimental and theoretical information. We find that the ${\Lambda }^{\ast }$ peak is clearly observed for the photo- and electro-productions with the finite $K^{\ast }N{\Lambda }^{\ast }$ interaction, whereas the clear peak signals survive only for the electro-production, when we ignore the interaction. These different behaviors can be understood by different $Q^2$ dependences in the $K^{\ast }$ electromagnetic and $K^{\ast }\to \gamma K$ transition form factors. We suggest a photon-polarization asymmetry $\Sigma$ to extract information of the $K^{\ast }N{\Lambda }^{\ast }$ interaction. It turns out that $\Sigma$ near the ${\Lambda }^{\ast }$ peak region becomes negative with a finite $K^{\ast }N{\Lambda }^{\ast }$ interaction while positive without it for $Q^2=0$, due to the different naturalities of $K$ and $K^{\ast }$ exchanges. For $Q^2\ne 0$, we observe more obvious signals in the peak region due to the additional contribution of the longitudinal virtual photon for ${\Lambda }^{\ast }$.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2019)·0 citations
10. 10*

    A Precise Determination of (Anti)neutrino Fluxes with (Anti)neutrino-Hydrogen Interactions

    H. Duyang🇺🇸 · B. Guo🇺🇸 · S.R. Mishra🇺🇸 · R. Petti🇺🇸

    We present a novel method to accurately determine the flux of neutrinos and antineutrinos, one of the dominant systematic uncertainty affecting current and future long-baseline neutrino experiments, as well as precision neutrino scattering experiment. Using exclusive topologies in $\nu (\bar{\nu })$-hydrogen interactions, ${\nu }_{\mu }p\to {\mu }^{-}p{\pi }^{+}$, ${\bar{\nu }}_{\mu }p\to {\mu }^{+}p{\pi }^{-}$, and ${\bar{\nu }}_{\mu }p\to {\mu }^{+}n$ with small hadronic energy, we achieve an overall accuracy on the relative fluxes better than 1\% in the energy range covering most of the available flux. Since we cannot rely on simulations nor model corrections at this level of precision, we present techniques to constrain all relevant systematic uncertainties using data themselves. The method can be implemented using the approach we recently proposed to collect high statistics samples of $\nu (\bar{\nu })$-hydrogen interactions in a low-density and high-resolution detector, which could serve as part of the near detector complex in a long-baseline neutrino experiment, as well as a dedicated beam monitoring detector.

    ↳ hep-phhep-exnucl-exnucl-th+1PLB(2019)·32 citations
11. 11*

    Ultrahigh-energy cosmic rays: Anomalies, QCD, and LHC data

    David d'Enterria🇨🇭

    Measurements of proton and nuclear collisions at the Large Hadron Collider at nucleon-nucleon c.m. energies up to $\sqrt{s_{NN}}=$ 13 TeV, have improved our understanding of hadronic interactions at the highest energies reached in collisions of cosmic rays with nuclei in the earth atmosphere, up to $\sqrt{s_{NN}}\approx 450$ TeV. The Monte Carlo event generators (EPOS, QGSJET, and SIBYLL) commonly used to describe the air showers generated by ultrahigh-energy cosmic rays (UHECR, with $E_{CR}\approx 10^{17}$--$10^{20}$ eV) feature now, after parameter retuning based on LHC Run-I data, more consistent predictions on the nature of the cosmic rays at the tail of the measured spectrum. However, anomalies persist in the data that cannot be accommodated by the models. Among others, the total number of muons (as well as their maximum production depth) remains significantly underestimated (overestimated) by all models. Comparisons of EPOS, QGSJET, and SIBYLL predictions to the latest LHC data, and to collider MC generators such as PYTHIA, indicate that improved description of hard multiple minijet production and nuclear effects may help reduce part of the data--model discrepancies, shed light on the UHECR composition approaching the observed $E_{CR}\approx 10^{20}$ eV cutoff, and uncover any potential new physics responsible of the observed anomalies.

    ↳ astro-ph.HEhep-exhep-phnucl-ex+1EPJ Web Conf.(2019)·6 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.