Fri·Oct 9, 2015Friday·October 9, 2015

1. 01*

   Search for Long-Range Correlations in Relativistic Heavy-Ion Collisions at SPS Energies

   Shakeel Ahmad🇮🇳 · Anisa Khatun🇮🇳 · Shaista Khan🇮🇳 · A. Ahmad🇮🇳 · M. Irfan🇮🇳

   Long range correlations are searched for by analyzing the experimental data on 16O-AgBr and 32S-AgBr collisions at 200A GeV/c and the results are compared with the predictions of a multi phase transport (AMPT) model. The findings reveal that the observed forward-backward (F-B) multiplicity correlations are mainly of short-range in nature. The range of F-B correlations are observed to extend with increasing projectile mass. The observed extended range of F-B correlations might be due to overall multiplicity fluctuations arising because of nuclear geometry. The findings are not sufficient for making any definite conclusions regarding the presence of long-range correlations.

   nucl-exhep-phnucl-thAdv.High Energy Phys.(2015)·4 citations
2. 02*

   GEM-based TPC with CCD Imaging for Directional Dark Matter Detection

   N. S. Phan🇺🇸 · R. J. Lauer🇺🇸 · E. R. Lee🇺🇸 · D. Loomba🇺🇸 · J. A. J. Matthews🇺🇸 · E. H. Miller🇺🇸

   The world's leading directional dark matter experiments currently all utilize low-pressure gas Time Projection Chamber (TPC) technologies. We discuss some of the challenges for this technology, for which balancing the goal of achieving the best sensitivity with that of cost effective scale-up requires optimization over a large parameter space. Critical for this are the precision measurements of the fundamental properties of both electron and nuclear recoil tracks down to the lowest detectable energies. Such measurements are necessary to provide a benchmark for background discrimination and directional sensitivity that could be used for future optimization studies for directional dark matter experiments. In this paper we describe a small, high resolution, high signal- to-noise GEM-based TPC with a 2D CCD readout designed for this goal. The performance of the detector was characterized using alpha particles, X-rays, gamma-rays, and neutrons, enabling detailed measurements of electron and nuclear recoil tracks. Stable effective gas gains of greater than $1\times 10^5$ were obtained in 100 Torr of pure CF${}_4$ by a cascade of three standard CERN GEMs each with a 140 $\mu$m pitch. The high signal-to-noise and sub-millimeter spatial resolution of the GEM amplification and CCD readout, together with low diffusion, allow for excellent background discrimination between electron and nuclear recoils down below $\sim$10 keVee ($\sim$23 keVr fluorine recoil). Even lower thresholds, necessary for the detection of low mass WIMPs for example, might be achieved by lowering the pressure and utilizing full 3D track reconstruction. These and other paths for improvements are discussed, as are possible fundamental limitations imposed by the physics of energy loss.

   ↳ physics.ins-detastro-ph.IMhep-exnucl-exAstropart.Phys.(2016)·31 citations
3. 03*

   Inclusive cross section and double-helicity asymmetry for ${\pi }^0$ production at midrapidity in $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · J. Alexander · M. Alfred · K. Aoki · N. Apadula · Y. Aramaki · H. Asano · E.T. Atomssa and 402 other authors

   PHENIX measurements are presented for the cross section and double-helicity asymmetry ($A_{LL}$) in inclusive ${\pi }^0$ production at midrapidity from $p$$+$$p$ collisions at $\sqrt{s}=510$~GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The ${\pi }^0{A}_{LL}$ results follow an increasingly positive asymmetry trend with $p_T$ and $\sqrt{s}$ with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on ${\pi }^0$ and jet $A_{LL}$, and suggested a positive contribution of gluon polarization to the spin of the proton $\Delta G$ for the gluon momentum fraction range $x>0.05$. The data presented here extend to a currently unexplored region, down to $x\sim 0.01$, and thus provide additional constraints on the value of $\Delta G$. The results confirm the evidence for nonzero $\Delta G$ using a different production channel in a complementary kinematic region.

   ↳ hep-exnucl-exPRD(2016)·84 citations
4. 04*

   First tests of the applicability of $\gamma$-ray imaging for background discrimination in time-of-flight neutron capture measurements

   D.L. Pérez Magán · L. Caballero-Ontanaya · C. Domingo-Pardo · J. Agramunt-Ros · F. Albiol · A. Casanovas · A. González · C. Guerrero · J. Lerendegui-Marco · A. Tarifeño-Saldivia · the n_TOF Collaboration

   In this work we explore for the first time the applicability of using $\gamma$-ray imaging in neutron capture measurements to identify and suppress spatially localized background. For this aim, a pinhole gamma camera is assembled, tested and characterized in terms of energy and spatial performance. It consists of a monolithic CeBr${}_3$ scintillating crystal coupled to a position-sensitive photomultiplier and readout through an integrated circuit AMIC2GR. The pinhole collimator is a massive carven block of lead. A series of dedicated measurements with calibrated sources and with a neutron beam incident on a ${}^{197}$Au sample have been carried out at n_TOF, achieving an enhancement of a factor of two in the signal-to-background ratio when selecting only those events coming from the direction of the sample.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·10 citations
5. 05*

   Effective field theory for nuclear vibrations with quantified uncertainties

   E. A. Coello Pérez🇩🇪 · T. Papenbrock🇺🇸

   We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients - quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level - are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for ${}^{62}$Ni, ${}^{98,100}$Ru, ${}^{106,108}$Pd, ${}^{110,112,114}$Cd, and ${}^{118,120,122}$Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.

   ↳ nucl-thnucl-exPRC(2015)·57 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.