Fri·Sep 27, 2019Friday·September 27, 2019

1. 01*

   Cosmogenic Neutron Production at the Sudbury Neutrino Observatory

   B. Aharmim🇨🇦 · S. N. Ahmed🇨🇦 · A. E. Anthony🇺🇸 · N. Barros🇵🇹 · E. W. Beier🇺🇸 · A. Bellerive🇨🇦 · B. Beltran🇨🇦 · M. Bergevin🇺🇸 · S. D. Biller🇬🇧 · R. Bonventre🇺🇸 · K. Boudjemline🇨🇦 · M. G. Boulay🇨🇦 and 119 other authors

   Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of GEANT4 physics models. In addition, the cosmogenic neutron yield, in units of $10^{-4}{\text{cm}}^2/\left(\text{g}\cdot \mu \right)$, is measured to be $7.28\pm 0.09{\text{stat.}}_{-1.12}^{+1.59}\text{syst.}$ in pure heavy water and $7.30\pm 0.07{\text{stat.}}_{-1.02}^{+1.40}\text{syst.}$ in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB.

   ↳ hep-exnucl-exPRD(2019)·17 citations
2. 02*

   The ANL-Osaka Partial-Wave Amplitudes of $\pi N$ and $\gamma N$ Reactions

   H. Kamano🇯🇵 · T.-S. H. Lee🇺🇸 · S.X. Nakamura🇨🇳 · T. Sato🇯🇵

   The determination of the Argonne National Laboratory-Osaka University (ANL-Osaka) Partial-Wave Amplitudes (PWA) of $\pi N$ and $\gamma N$ Reactions is reviewed. The predicted PWA are presented on a web page (https://www.phy.anl.gov/theory/research/anl-osaka-pwa). The formulas are given for using the predicted PWA to calculate the cross sections of (1) meson-baryon ($MB$) scattering $MB\to M^{\prime }{B}^{\prime }$ with $MB,M^{\prime }{B}^{\prime }=\pi N,\eta N,K\Lambda ,K\Sigma$, (2) two-pion production $\pi N\to \pi \Delta ,\rho N,\sigma N\to \pi \pi N$, (3) Meson photoproduction $\gamma N\to \pi N,\eta N,K\Lambda ,K\Sigma$, (4) Pion electroproduction $N(e,e^{\prime }\pi )N$, (5) inclusive $N(e,e^{\prime })X$. We also present sample results from our fits to the data.

   ↳ nucl-thhep-exhep-phnucl-ex23 citations
3. 03*

   Exploring continuum structures in reactions with three-body nuclei

   J. Casal🇮🇹 · M. Gómez-Ramos🇪🇸 · A. M. Moro🇪🇸 · A. Corsi🇫🇷

   The Transfer to the Continuum method has been applied to describe the ${}^{11}\text{Li}(p,pn)$ and ${}^{14}\text{Be}(p,pn)$ reactions in inverse kinematics, using structure overlaps computed within a full three-body model for the projectile. Calculations agree with the available experimental data on the unbound ${}^{10}$Li and ${}^{13}$Be nuclei.

   ↳ nucl-thnucl-exJ.Phys.Conf.Ser.(2020)·2 citations
4. 04*

   Baseline study for net-proton number fluctuations at top energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider with the Angantyr model

   Nirbhay Kumar Behera🇰🇷 · Ranjit Kumar Nayak🇮🇳 · Sadhana Dash🇮🇳

   The multiplicity percentile dependence of cumulants, of net-proton number distributions in Au$-$Au collisions at $\sqrt{s_{NN}}=$ 200 GeV and Pb$-$Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV has been investigated using the Angantyr model (the heavy-ion extension of the \textsc{Pythia 8} model). The effects of finite transverse momentum ($p_{\mathrm{T}}$) and pseudorapidity ($\eta$) acceptance on the net-proton cumulants have also been studied. Furthermore, the effects of the hydrodynamic expansion and feed down from weak decays were explored. It was found that radial flow has substantial impact on the cumulants and their ratios, while weak decays have a finite but relatively smaller effect. The obtained values of cumulants and their ratios with the Angantyr model, where the formation of thermalized medium is not assumed can serve as a baseline for future measurements.

   ↳ hep-phhep-exnucl-exPRC(2020)·3 citations
5. 05*

   $\beta$-delayed proton emission from ${}^{11}$Be in effective field theory

   Wael Elkamhawy🇩🇪 · Zichao Yang🇺🇸 · Hans-Werner Hammer🇩🇪 · Lucas Platter🇺🇸

   We calculate the rate of the rare decay ${}^{11}\text{Be}$ into ${}^{10}\text{Be}+p+e^{-}+{\bar{\nu }}_e$ using Halo effective field theory, thereby describing the process of beta-delayed proton emission. We assume a shallow $1/2^{+}$ resonance in the ${}^{10}\text{Be}-p$ system with an energy consistent with a recent experiment by Ayyad et al. and obtain $b_p=4.9_{-2.9}^{+5.6}{\text{(exp.)}}_{-0.8}^{+4.0}\text{(theo.)}\times 10^{-6}$ for the branching ratio of this decay, predicting a resonance width of ${\Gamma }_R=(9.0_{-3.3}^{+4.8}{\text{(exp.)}}_{-2.2}^{+5.3}\text{(theo.)})\text{keV}$. Our calculation shows that the experimental branching ratio and resonance parameters of Ayyad et al. are consistent with each other. Moreover, we analyze the general impact of a resonance on the branching ratio and demonstrate that a wide range of combinations of resonance energies and widths can reproduce branching ratios of the correct order. Thus, no exotic mechanism (such as beyond the standard model physics) is needed to explain the experimental decay rate.

   ↳ nucl-thnucl-exPLB(2021)·18 citations
6. 06*

   Recent results for forward J/$\mathbf{\psi }$ production in Pb--Pb Ultra-Peripheral Collisions at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}=5.02$ TeV with the ALICE detector

   Simone Ragoni (for the ALICE Collaboration)🇬🇧

   The LHC is not only the highest energy collider for protons and heavy ions, but also for photon photon and photon hadron ($\gamma$p and $\gamma$Pb) interactions. This is because the protons and ions accelerated in the LHC carry an electromagnetic field, which can be viewed as a source of photons, and such photons can interact with either other photons or with hadrons. Ultra Peripheral Collisions (UPC) occur when the incoming ions pass beyond the range of the strong force, with impact parameters larger than the sum of the radii of the incoming projectiles, and are mediated by the exchange of virtual photons between the nuclei. The number of photons scales with the square of the nuclear electric charge, and the photon energies increase rapidly with beam energy. The beam energies at the LHC make the LHC the most energetic photon source ever built. In particular, the photoproduction of heavy vector mesons is favoured because such mesons couple to the photon. Recent results for forward J/$\psi$ production in Pb--Pb UPCs at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector are presented here.

   ↳ hep-exnucl-ex1 citation
7. 07*

   Probing the evolution of heavy-ion collisions using direct photon interferometry

   Oscar Garcia-Montero🇩🇪 · Nicole Löher🇩🇪 · Aleksas Mazeliauskas🇨🇭 · Jürgen Berges🇩🇪 · Klaus Reygers🇩🇪

   We investigate the measurement of Hanbury Brown-Twiss (HBT) photon correlations as an experimental tool to discriminate different sources of photon enhancement, which are proposed to simultaneously reproduce the direct photon yield and the azimuthal anisotropy measured in nuclear collisions at RHIC and the LHC. To showcase this, we consider two different scenarios in which we enhance the yields from standard hydrodynamical simulations. In the first, additional photons are produced from the early pre-equilibrium stage computed from the \textit{bottom-up} thermalization scenario. In the second, the thermal rates are enhanced close to the pseudo-critical temperature $T_c\approx 155\text{MeV}$ using a phenomenological ansatz. We compute the correlators for relative momenta $q_o,q_s$ and $q_l$ for different transverse pair momenta, $K_{\perp }$, and find that the longitudinal correlation is the most sensitive to different photon sources. Our results also demonstrate that including anisotropic pre-equilibrium rates enhances non-Gaussianities in the correlators, which can be quantified using the kurtosis of the correlators. Finally, we study the feasibility of measuring a direct photon HBT signal in the upcoming high-luminosity LHC runs. Considering only statistical uncertainties, we find that with the projected $\sim 10^{10}$ heavy ion events a measurement of the HBT correlations for $K_{\perp }<1\text{GeV}$ is statistically significant.

   ↳ hep-phnucl-exnucl-thPRC(2020)·24 citations
8. 08*

   Gluon polarization measurements from longitudinally polarized proton-proton collisions at STAR

   Zilong Chang (for the STAR Collaboration)🇺🇸

   The gluon polarization contribution to the proton spin is an integral part to solve the longstanding proton spin puzzle. At the Relativistic Heavy Ion Collider (RHIC), the STAR experiment has measured jets produced in mid-pseudo-rapidity, $|\eta |<$ 1.0, and full azimuth, $\varphi$, from longitudinally polarized $pp$ collisions to study the gluon polarization in the proton. At center of mass energies $\sqrt{s}=$ 200 and 510 GeV, jet production is dominated by hard QCD scattering processes such as gluon-gluon ($gg$) and quark-gluon ($qg$), thus making the longitudinal double-spin asymmetry ($A_{LL}$) sensitive to the gluon polarization. Early STAR inclusive jet $A_{LL}$ results at $\sqrt{s}=$ 200 GeV provided the first evidence of the non-zero gluon polarization at momentum fraction $x>$ 0.05. The higher center of mass energy $\sqrt{s}=510$ GeV allows to explore the gluon polarization as low as $x\sim$ 0.015. In this talk we will present the recent STAR inclusive jet and dijet $A_{LL}$ results at $\sqrt{s}=510$ GeV, and discuss the relevant new analysis techniques for the estimation of trigger bias and reconstruction uncertainty, the underlying event correction on the jet energy and its effect on jet $A_{LL}$. Dijet results are shown for different topologies in regions of pseudo-rapidity, effectively scanning the $x$-dependence of the gluon polarization.

   ↳ hep-exnucl-ex0 citations
9. 09*

   Inclusive Jet Measurements in Longitudinally Polarized proton-proton Collisions at STAR

   Zilong Chang (for the STAR Collaboration)🇺🇸

   Jet production in high energy proton-proton ($p+p$) collisions is dominated by hard QCD subprocesses such as gluon-gluon and quark-gluon scatterings. Therefore $p+p$ is an effective tool to probe the internal distribution of gluons in the proton. The STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC) is using longitudinally polarized $p+p$ collisions at the center of mass energies, $\sqrt{s}=$ 200 and 510 GeV, to study the cross-section and double spin asymmetries, $A_{LL}$, of inclusive jet and di-jet production. The measurements at $\sqrt{s}=$ 200 GeV showed that the jet cross-sections are well described by the next-to-leading-order perturbative QCD calculations after underlying event and hadronization corrections. The previous 2009 $\sqrt{s}=$ 200 GeV inclusive jet asymmetry $A_{LL}$ measurement at pseudo-rapidity $|\eta |<$ 1.0 showed the first experimental evidence of a non-zero gluon polarization for partonic momentum fraction, $x>0.05$. The inclusive jet $A_{LL}$ measurement at $\sqrt{s}=$ 510 GeV allows to explore the gluon polarization to smaller $x\sim 0.02$. The 2012 inclusive jet $A_{LL}$ and cross-section measurements at $\sqrt{s}=$ 510 GeV, the techniques used in the jet analysis including underlying event correction, and future perspectives related to jet measurements at STAR will be presented.

   ↳ hep-exnucl-exPoS(2018)·0 citations
10. 10*

    Catching a glimpse of the parton structure of the bound proton

    Sara Fucini🇮🇹 · Sergio Scopetta🇮🇹 · Michele Viviani🇮🇹

    A new generation of experiments is expected to shed light on the elusive parton structure of the bound proton. One of the most promising directions is incoherent deeply virtual Compton scattering, which can provide a tomographic view of the bound proton. The first measurement has been recently performed, using ${}^4$He targets at Jefferson Lab. In the work presented here, a rigorous Impulse Approximation analysis of this process is proposed. As ingredients, state-of-the-art models of the nuclear spectral function and of the parton structure of the struck proton, together with novel scattering amplitudes expressions for a bound moving nucleon, have been used. A good overall agreement with the data is obtained, in particular at high values of the photon virtuality. The observed big difference between results for the bound proton and those for the free one turns out to be due in small part to modifications of the parton structure, and rather it should be related to kinematical nuclear effects. The analysis demonstrates that the comparison of the results of this approach, based on a conventional description, with future precise data, has the potential to expose exotic quark and gluon effects in nuclei.

    ↳ nucl-thhep-phnucl-exPRD(2020)·12 citations
11. 11*

    Non-equilibrium photons from the bottom-up thermalization scenario

    Oscar Garcia-Montero🇩🇪

    In this work, I calculate the $p_{\perp }$ resolved spectra for the three stages of the \textit{bottom-up} scenario, which are comparable to the thermal contribution, particularly at higher values of the saturation scale $Q_S^2$. Analytical solutions are obtained by including a parametrization of scaling solutions from far-from-equilibrium classical statistical lattice simulations into a small angle kinetic rate. Furthermore, a theoretically motivated ansatz is used to account for near-collinear enhancement of the low-$p_{\perp }$ radiation. The system is phenomenologically constrained using the charge hadron multiplicities from LHC and RHIC as in previous parametric estimates and fair agreement with the data available for photons was found. I find that for this realistic set of parameters, the contribution from the thermalizing glasma dominates the excess photons.

    ↳ hep-phnucl-exnucl-thAnnals Phys.(2022)·21 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.