Fri·Jul 15, 2016Friday·July 15, 2016

1. 01*

   Measurement of Target and Double-spin Asymmetries for the $\vec{e}\vec{p}\to e{\pi }^{+}(n)$ Reaction in the Nucleon Resonance Region at Low $Q^2$

   X. Zheng · K.P. Adhikari · P. Bosted · A. Deur · V. Drozdov · L. El Fassi · Hyekoo Kang · K. Kovacs · S. Kuhn · E. Long · S.K. Phillips · M. Ripani and 138 other authors

   We report measurements of target- and double-spin asymmetries for the exclusive channel $\vec{e}\vec{p}\to e{\pi }^{+}(n)$ in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized NH${}_3$ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3 and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low $Q^2$ range from $0.0065$ to $0.35$ (GeV$/c$)${}^2$. The $Q^2$ access was made possible by a custom-built Cherenkov detector that allowed the detection of electrons for scattering angles as low as $6^{\circ }$. These results are compared with the unitary isobar models JANR and MAID, the partial-wave analysis prediction from SAID and the dynamic model DMT. In many kinematic regions our results, in particular results on the target asymmetry, help to constrain the polarization-dependent components of these models.

   nucl-exPRC(2016)·10 citations
2. 02*

   An experimental review on heavy flavor $v_2$ in heavy-ion collision

   Md. Nasim🇺🇸 · Roli Esha🇺🇸 · Huan Zhong Huang🇺🇸

   For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions -high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb and U+U collisions at energies ranging from $\sqrt{s_{NN}}$ = 7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nuclei-nuclei collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson ($D$-meson), $J/\psi$ and leptons from heavy flavor decay at RHIC and LHC energy.

   nucl-exAdv.High Energy Phys.(2016)·2 citations
3. 03*

   Production of $\Lambda \Lambda$ and $\overline{\Lambda \text{n}}$ in central Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV within a covariant coalescence model

   Kai-Jia Sun🇨🇳 · Lie-Wen Chen🇨🇳

   We study the production of $\Lambda \Lambda$ and $\overline{\Lambda \text{n}}$ exotic states in central Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at LHC via both hadron and quark coalescence within a covariant coalescence model with a blast-wave-like parametrization for the phase-space configurations of constituent particles at freezeout. In the hadron coalescence, the two states are considered as molecular states while they are considered as six-quark states in the quark coalescence.For $\overline{\Lambda \text{n}}$, we find that the yields of both molecular and six-quark states are much larger than the experimental upper-limits. For $\Lambda \Lambda$, while the molecule-state yield is much larger than the experimental upper-limits, the six-quark-state yield could be lower than the upper-limits. The higher molecule-state yields are mainly due to the large contribution of short-lived strong resonance decays into (anti-)nucleons and (anti-)$\Lambda$ which can significantly enhance the molecule-state yields of $\Lambda \Lambda$ and $\overline{\Lambda \text{n}}$ via hadron coalescence. Our results suggest that the current experimental measurement at LHC cannot exclude the existence of the $\Lambda \Lambda$ as an exotic six-quark state, and if $\Lambda \Lambda$ is a six-quark state, it is then on the brink of being discovered.

   ↳ nucl-thhep-phnucl-exPRC(2016)·14 citations
4. 04*

   Universality of nucleon-nucleon short-range correlations: the factorization property of the nuclear wave function, the relative and center-of-mass momentum distributions, and the nuclear contacts

   Massimiliano Alvioli🇮🇹 · Claudio Ciofi degli Atti🇮🇹 · Hiko Morita🇯🇵

   The two-nucleon momentum distributions have been calculated for nuclei up to A=40 and various values of the relative and center-of-mass momenta and angle between them. For complex nuclei a parameter-free linked-cluster expansion, based upon a realistic local two-nucleon interaction of the Argonne family and variational wave function featuring central, tensor, spin and iso-spin correlations, has been used. The obtained results show that: 1) independently of the mass number A, at values of the relative momentum k_rel> 2 fm^{-1} the proton-neutron momentum distributions for back-to-back (BB) nucleons (K_cm=0) exhibit the factorization property n_A^{pn}(k_rel,K_cm=0)=C_A^{pn} n_D(k_rel) n_{cm}^{pn}(K_cm=0), where n_D is the deuteron momentum distribution, n_{cm}^{pn}(K_{cm}=0) the momentum distribution of the c.m. motion of the pair and C_A^{pn} the nuclear contact measuring the number of BB pn pairs with deuteron-like momenta; 2) the values of the proton-neutron nuclear contact C_A^{pn} are obtained in a model-independent way from the ratio n_A^{pn}(k_rel,K_cm=0)/n_D(k_rel) n_{cm}^{pn}(K_cm=0); 3) also the K_cm-integrated pn momentum distributions divided by the deuteron momentum distribution exhibits a constant behavior equal to C_A^{pn}, but only at very high values of k_{rel}> 3.5fm^{-1}, where the relative momentum distribution is entirely governed by BB short-range correlated nucleons; 4) the absolute value of the number of pn and pp short-range correlated pairs is calculated, illustrating that the high values (K_cm>1 fm^{-1}) of the pair c.m. momentum appreciably reduce the dominance of the pn over pp pairs produced by the tensor force when K_cm=0; 5) calculations are in good agreement with the VMC calculations for light nuclei and with available experimental on the processes A(e,e'pn)X and A(e,e'pp)X.

   ↳ nucl-thnucl-exPRC(2016)·44 citations
5. 05*

   Improvement of radiopurity level of enriched ${}^{116}$CdWO${}_4$ and ZnWO${}_4$ crystal scintillators by recrystallization

   A.S. Barabash🇷🇺 · P. Belli🇮🇹 · R. Bernabei🇮🇹 · Yu.A. Borovlev🇷🇺 · F. Cappella🇮🇹 · V. Caracciolo🇮🇹 · R. Cerulli🇮🇹 · F.A. Danevich🇺🇦 · A. Incicchitti🇮🇹 · V.V. Kobychev🇺🇦 · S.I. Konovalov🇷🇺 · M. Laubenstein🇮🇹 and 8 other authors

   As low as possible radioactive contamination of a detector plays a crucial role to improve sensitivity of a double beta decay experiment. The radioactive contamination of a sample of ${}^{116}$CdWO${}_4$ crystal scintillator by thorium was reduced by a factor $\approx 10$, down to the level 0.01 mBq/kg (${}^{228}$Th), by exploiting the recrystallization procedure. The total alpha activity of uranium and thorium daughters was reduced by a factor $\approx 3$, down to 1.6 mBq/kg. No change in the specific activity (the total $\alpha$ activity and ${}^{228}$Th) was observed in a sample of ZnWO${}_4$ crystal produced by recrystallization after removing $\approx 0.4$ mm surface layer of the crystal.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.(2016)·37 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.