Fri·Dec 9, 2016Friday·December 9, 2016

1. 01*

   Quarkonium measurements via the di-muon decay channel in $\mathrm{p}$+$\mathrm{p}$ and $\mathrm{Au}$+$\mathrm{Au}$ collisions with the STAR experiment

   Takahito Todoroki (for the STAR collaboration)🇺🇸

   We present the first $J/\psi$ and ${\rm Y}$ measurements in the di-muon decay channel at mid-rapidity at RHIC using the newly installed Muon Telescope Detector. In p$+$p collisions at $\sqrt{s}=500$~GeV, inclusive $J/\psi$ cross section can be described by CGC+NRQCD and NLO NRQCD model calculations for $0<p_T<20$~GeV/$c$. In Au$+$Au collisions at $\sqrt{s_{NN}}=200$~GeV, we observe (i) clear $J/\psi$ suppression indicating dissociation; (ii) $J/\psi$ $R_{AA}$ can be qualitatively described by transport models including dissociation and regeneration with a tension at high $p_T$; and (iii) hint of less melting of ${\rm Y}(2S+3S)$ relative to ${\rm Y}(1S)$ at RHIC compared to that at LHC.

   nucl-exJ.Phys.Conf.Ser.(2017)·9 citations
2. 02*

   Identification of Jet-like events using a Multiplicity Detector

   Ranbir Singh🇮🇳 · Bedangadas Mohanty🇮🇳

   We present a method for studying the detection of jets in high energy hadronic collisions using multiplicity detector in forward rapidities. Such a study enhances the physics scope of multiplicity detectors at forward rapidities in LHC. At LHC energies the jets may be produced with significant cross section in forward rapidities. A multi resolution wavelet analysis technique can locate the spatial position of jets due to its feature of space-scale locality. The discrete wavelet proves to be very effective in probing physics simultaneously at different locations in phase space and at different scales to identify jet-like events. The key feature this analysis exploits is the difference in particle density in localized regions of the detector due to jet-like and underlying events. We find that this method has a significant sensitivity towards detecting jet position and its size. The jets can be found with the efficiency and purity of the order of 46%.

   ↳ hep-exnucl-exEPJC(2019)·0 citations
3. 03*

   Impact of $(\alpha ,n)$ reactions on weak r-process in neutrino-driven winds

   Julia Bliss · Almudena Arcones🇩🇪 · Fernando Montes🇺🇸 · Jorge Pereira

   After a successful core-collapse supernova, a neutrino-driven wind develops where it is possible to synthesize lighter heavy elements ($30<Z<45$). In the early galaxy, the origin of these elements is associated to the r-process and to an additional process. Here we assume the additional process corresponds to the weak r-process or alpha-process taking place in neutrino-driven winds. Based on a trajectory obtained from hydrodynamical simulations we study the astrophysics and nuclear physics uncertainties with our main focus on the $(\alpha ,n)$ reactions. These are critical to redistribute the matter and allow to further move it from light to heavy elements after nuclear statistical equilibrium freezes out. In this first sensitivity study, we vary all $(\alpha ,n)$ reactions by given constant factors which are justified based on the uncertainties of the statistical model and its nuclear physics input, mainly alpha optical potentials under the conditions found in the wind. Our results show that $(\alpha ,n)$ reactions are indeed very important to predict abundances. Therefore, further studies will follow to identify individual critical reactions. Since the nucleosynthesis path is close to stability, these reactions can be measured in the near future. This will uniquely allow to reduce the nuclear physics uncertainties and thus to use observations to constrain and understand the astrophysical conditions in the wind.

   ↳ astro-ph.SRastro-ph.HEnucl-exnucl-thJ.Phys.G(2017)·52 citations
4. 04*

   Hunting the Gluon Orbital Angular Momentum at the Electron-Ion Collider

   Xiangdong Ji🇨🇳 · Feng Yuan🇺🇸 · Yong Zhao🇺🇸

   Applying the connection between the parton Wigner distribution and orbital angular momentum (OAM), we investigate the probe of the gluon OAM in hard scattering processes at the planned electron-ion collider. We show that the single longitudinal target-spin asymmetry in the hard diffractive dijet production is very sensitive to the gluon OAM distribution. The associated spin asymmetry leads to a characteristic azimuthal angular correlation of $\sin ({\varphi }_q-{\varphi }_{\Delta })$, where ${\varphi }_{\Delta }$ and ${\varphi }_q$ are the azimuthal angles of the proton momentum transfer and the relative transverse momentum between the quark-antiquark pair. This study will enable a first measurement of the gluon OAM in the proton spin sum rule.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2017)·74 citations
5. 05*

   Gluon orbital angular momentum at small-$x$

   Yoshitaka Hatta🇯🇵 · Yuya Nakagawa🇯🇵 · Bowen Xiao🇨🇳 · Feng Yuan🇺🇸 · Yong Zhao🇺🇸

   We present a general analysis of the orbital angular momentum (OAM) distribution of gluons $L_g(x)$ inside the nucleon with particular emphasis on the small-$x$ region. We derive a novel operator representation of $L_g(x)$ in terms of Wilson lines and argue that it is approximately proportional to the gluon helicity distribution $L_g(x)\approx -2\Delta G(x)$ at small-$x$. We also compute longitudinal single spin asymmetry in exclusive diffractive dijet production in lepton-nucleon scattering in the next-to-eikonal approximation and show that the asymmetry is a direct probe of the gluon helicity/OAM distribution as well as the QCD odderon exchange.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·124 citations
6. 06*

   Thermal conductivity measurements of PTFE and Al${}_2$O${}_3$ ceramic at sub-Kelvin temperatures

   Alexey Drobizhev🇺🇸 · Jared Reiten · Vivek Singh🇮🇳 · Yury G. Kolomensky🇺🇸

   The design of low temperature bolometric detectors for rare event searches necessitates careful selection and characterization of structural materials based on their thermal properties. We measure the thermal conductivities of polytetrafluoroethylene (PTFE) and Al${}_2$O${}_3$ ceramic (alumina) in the temperature ranges of 0.17-0.43 K and 0.1-1.3 K, respectively. For the former, we observe a quadratic temperature dependence across the entire measured range. For the latter, we see a cubic dependence on temperature above ~0.3 K, with a linear contribution below that temperature. This paper presents our measurement techniques, results, and theoretical discussions. Keywords: Thermal Conductivity, PTFE, Al${}_2$O${}_3$ ceramic, Bolometer

   ↳ cond-mat.mtrl-scinucl-exphysics.ins-detCryogenics(2017)·6 citations
7. 07*

   Faddeev fixed center approximation to $\pi \bar{K}{K}^{\ast }$ system and the ${\pi }_1(1600)$

   Xu Zhang🇨🇳 · Ju-Jun Xie🇨🇳 · Xurong Chen🇨🇳

   We investigate the three-body system of $\pi \bar{K}{K}^{\ast }$ by using the fixed-center approximation to the Faddeev equation, taking the interaction between $\pi$ and $\bar{K}$, $\pi$ and $K^{\ast }$, and $\bar{K}$ and $K^{\ast }$ from the chiral unitary approach. The study is made assuming scattering of a $\pi$ on a $\bar{K}{K}^{\ast }$ cluster, which is known to generate the $f_1(1285)$ state. The resonant structure around $1650$ MeV shows up in the modulus squared of the $\pi$-$(\bar{K}{K}^{\ast }{)}_{f_1(1285)}$ scattering amplitude and suggests that a $\pi$-$(\bar{K}{K}^{\ast }{)}_{f_1(1285)}$ state, with "exotic" quantum numbers $J^{PC}=1^{-+}$, can be formed. This state can be identified as the observed ${\pi }_1(1600)$ resonance. We suggest that this is the origin of the present ${\pi }_1(1600)$ resonance and propose to look at the $\pi f_1(1285)$ mode in future experiments to clarify the issue.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·7 citations
8. 08*

   Medium effects in $\Lambda K^{+}$ pair production by 2.83 GeV protons on nuclei

   E. Ya. Paryev🇷🇺 · M. Hartmann🇩🇪 · Yu. T. Kiselev🇷🇺

   We study $\Lambda K^{+}$ pair production in the interaction of protons of 2.83 GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the nuclear spectral function approach for incoherent primary proton--nucleon and secondary pion--nucleon production processes, and processes associated with the creation of intermediate ${\Sigma }^0{K}^{+}$ pairs. The approach accounts for the initial proton and final $\Lambda$ hyperon absorption, final $K^{+}$ meson distortion in nuclei, target nucleon binding, and Fermi motion, as well as nuclear mean-field potential effects on these processes. We calculate the $\Lambda$ momentum dependence of the absolute $\Lambda K^{+}$ yield from the target nuclei considered, in the kinematical conditions of the ANKE experiment, performed at COSY, within the different scenarios for the $\Lambda$-nucleus effective scalar potential. We show that the above observable is appreciably sensitive to this potential in the low-momentum region. Therefore, direct comparison of the results of our calculations with the data from the ANKE-at-COSY experiment can help to determine the above potential at finite momenta. We also demonstrate that the two-step pion--nucleon production channels dominate in the low-momentum $\Lambda K^{+}$ production in the chosen kinematics and, therefore, they have to be taken into account in the analysis of these data.

   ↳ nucl-thnucl-exCPC(2017)·8 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.