Tue·Jun 14, 2016Tuesday·June 14, 2016

1. 01*

   Cumulants of Net-Proton, Net-Kaon and Net-Charge Multiplicity Distributions in Au+Au Collisions at RHIC BES Energies from UrQMD Model

   Ji Xu🇨🇳 · Shili Yu🇨🇳 · Feng Liu🇨🇳 · Xiaofeng Luo🇨🇳

   Fluctuations of conserved quantities are sensitive observables to probe the signature of QCD phase transition and critical point in heavy-ion collisions. With the UrQMD model, we have studied the centrality and energy dependence of various order cumulants and cumulant ratios (up to fourth order) of net-proton,net-charge and net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}}$= 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV. The model results show that the production mechanism of the particles and anti-particles have significant impacts on the cumulants of net-particles multiplicity distributions and show strong energy dependence. We also made comparisons between model calculations and experimental data measured in the first phase of the beam energy scan (BES) program by the STAR experiment at RHIC. The comparisons indicate that the baryon conservation effect strongly suppress the cumulants of net-proton distributions at low energies and the non-monotonic energy dependence for the net-proton {\KV} at the most central Au+Au collisions measured by the STAR experiment can not be described by the UrQMD model. Since there has no physics of QCD phase transition and QCD critical point implemented in the UrQMD, the model results provide us baselines and qualitative estimates about the non-critical background contributions to the fluctuations observables in heavy-ion collisions.

   nucl-exhep-exhep-phnucl-thPRC(2016)·47 citations
2. 02*

   Open heavy-flavour and quarkonium production in Pb-Pb and p-Pb collisions measured by the ALICE detector at the LHC

   Davide Caffarri (for the ALICE Collaboration)🇨🇭

   Open heavy-flavour and quarkonia measurements are important tools to study the hot and dense partonic medium formed in ultra-relativistic heavy-ion collisions. The modification of their production in those collisions, with respect to the pp and p-Pb ones, can help in the characterization of this medium. Quarkonia and open heavy-flavour production is measured in ALICE in the three different collision systems, at mid- and forward rapidity. A selection of those results recently obtained in Pb-Pb and p-Pb collisions by the ALICE Collaboration is presented.

   nucl-ex1 citation
3. 03*

   Change of nuclear configurations in the neutrinoless double-$\beta$ decay of ${}^{130}$Te $\to$ ${}^{130}$Xe and ${}^{136}$Xe $\to$ ${}^{136}$Ba

   J. P. Entwisle🇬🇧 · B. P. Kay🇺🇸 · A. Tamii🇯🇵 · S. Adachi🇯🇵 · N. Aoi🇯🇵 · J. A. Clark🇺🇸 · S. J. Freeman🇬🇧 · H. Fujita🇯🇵 · Y. Fujita🇯🇵 · T. Furuno🇯🇵 · T. Hashimoto🇰🇷 · C. R. Hoffman🇺🇸 and 15 other authors

   The change in the configuration of valence protons between the initial and final states in the neutrinoless double-$\beta$ decay of ${}^{130}$Te $\to$ ${}^{130}$Xe and of ${}^{136}$Xe $\to$ ${}^{136}$Ba has been determined by measuring the cross sections of the ($d$,${}^3$He) reaction with 101-MeV deuterons. Together with our recent determination of the relevant neutron configurations involved in the process, a quantitative comparison with the latest shell-model and interacting-boson-model calculations reveals significant discrepancies. These are the same calculations used to determine the nuclear matrix elements governing the rate of neutrinoless double-$\beta$ decay in these systems.

   nucl-exnucl-thPRC(2016)·37 citations
4. 04*

   Monte Carlo simulation of a very high resolution thermal neutron detector composed of glass scintillator microfibers

   Song Yushou · Joseph Conner · Xiaodong Zhang🇺🇸 · Jason P. Hayward🇺🇸

   In order to develop a high spatial resolution (micron level) thermal neutron detector, a detector assembly composed of cerium doped lithium glass microfibers, each with a diameter of 1\,$\mu$m, is proposed, where the neutron absorption location is reconstructed from the observed charged particle products that result from neutron absorption. To suppress the cross talk of the scintillation light, each scintillating fiber is surrounded by air-filled glass capillaries with the same diameter as the fiber. This pattern is repeated to form a bulk microfiber detector. On one end, the surface of the detector is painted with a thin optical reflector to increase the light collection efficiency at the other end. Then the scintillation light emitted by any neutron interaction is transmitted to one end, magnified, and recorded by an intensified CCD camera. A simulation based on the Geant4 toolkit was developed to model this detector. All the relevant physics processes including neutron interaction, scintillation, and optical boundary behaviors are si\-mulated. This simulation was first validated through measurements of neutron response from lithium glass cylinders. With good expected light collection, an algorithm based upon the features inherent to alpha and triton particle tracks is proposed to reconstruct the neutron reaction position in the glass fiber array. Given a 1\,$\mu$m fiber diameter and 0.1\,mm detector thickness, the neutron spatial resolution is expected to reach $\sigma \sim 1\mu$m with a Gaussian fit in each lateral dimension. The detection efficiency was estimated to be 3.7\% for a glass fiber assembly with thickness of 0.1\,mm. When the detector thickness increases from 0.1\,mm to 1\,mm, the position resolution is not expected to vary much, while the detection efficiency is expected to increase by about a factor of ten.

   ↳ physics.ins-detnucl-exAppl.Radiat.Isot.(2016)·2 citations
5. 05*

   Exclusive $\omega$ meson muoproduction on transversely polarised protons

   C. Adolph🇩🇪 · J. Agarwala🇮🇹 · M. Aghasyan🇮🇹 · R. Akhunzyanov🇷🇺 · M.G. Alexeev🇮🇹 · G.D. Alexeev🇷🇺 · A. Amoroso🇮🇹 · V. Andrieux🇫🇷 · N.V. Anfimov🇷🇺 · V. Anosov🇷🇺 · W. Augustyniak🇵🇱 · A. Austregesilo🇩🇪 and 217 other authors

   Exclusive production of $\omega$ mesons was studied at the COMPASS experiment by scattering $160\mathrm{GeV}/c$ muons off transversely polarised protons. Five single-spin and three double-spin azimuthal asymmetries were measured in the range of photon virtuality $1(\mathrm{GeV}/c{)}^2<Q^2<10(\mathrm{GeV}/c{)}^2$, Bjorken scaling variable $0.003<x_{Bj}<0.3$ and transverse momentum squared of the $\omega$ meson $0.05(\mathrm{GeV}/c{)}^2<p_T^2<0.5(\mathrm{GeV}/c{)}^2$. The measured asymmetries are sensitive to the nucleon helicity-flip Generalised Parton Distributions (GPD) $E$ that are related to the orbital angular momentum of quarks, the chiral-odd GPDs $H_T$ that are related to the transversity Parton Distribution Functions, and the sign of the $\pi \omega$ transition form factor. The results are compared to recent calculations of a GPD-based model.

   ↳ hep-exnucl-exNPB(2017)·18 citations
6. 06*

   Thermal blurring of event-by-event fluctuations provoked by rapidity conversion

   Yutaro Ohnishi🇯🇵 · Masakiyo Kitazawa🇯🇵 · Masayuki Asakawa🇯🇵

   We study the effect of thermal blurring caused by the use of (momentum-space) rapidity as a proxy of coordinate-space rapidity in experimental measurements of conserved charge fluctuations in relativistic heavy ion collisions. In theoretical studies assuming statistical mechanics, calculated fluctuations are those in a spatial volume. Experiments, on the other hand, can measure fluctuations only in a momentum-space in the final state. In a standard argument to compare experimental results for a momentum space with theoretical studies for a coordinate space, rapidities of particles are implicitly regarded as equivalent to their coordinate-space rapidity. We show that the relation of two fluctuations is significantly altered by the existence of the thermal motion, i.e. thermal blurring. We discuss that the thermal blurring can be regarded as a part of the diffusion process, and the effect can be understood by studying the rapidity window dependences of fluctuations. Centrality dependence of the thermal blurring effect is also discussed.

   ↳ nucl-thhep-phnucl-exPRC(2016)·32 citations
7. 07*

   Perspective on the origin of hadron masses

   Craig D. Roberts🇺🇸

   The energy-momentum tensor in chiral QCD, $T_{\mu \nu }$, exhibits an anomaly, viz. ${\Theta }_0:=T_{\mu \mu }\ne 0$. Measured in the proton, this anomaly yields $m_p^2$, where $m_p$ is the proton's mass; but, at the same time, when computed in the pion, the answer is $m_{\pi }^2=0$. Any attempt to understand the origin and nature of mass, and identify observable expressions thereof, must explain and unify these two apparently contradictory results, which are fundamental to the nature of our Universe. Given the importance of Poincaré-invariance in modern physics, the utility of a frame-dependent approach to this problem seems limited. That is especially true of any approach tied to a rest-frame decomposition of $T_{\mu \nu }$ because a massless particle does not possess a rest-frame. On the other hand, the dynamical chiral symmetry breaking (DCSB) paradigm, connected with a Poincaré-covariant treatment of the continuum bound-state problem, provides a straightforward, simultaneous explanation of both these identities, and also a diverse array of predictions, testable at existing and proposed facilities. From this perspective, $⟨\pi |{\Theta }_0|\pi ⟩=0$ owing to exact, symmetry-driven cancellations which occur between one-body dressing effects and two-body-irreducible binding interactions in any well-defined computation of the forward scattering amplitude that defines this expectation value in the pseudoscalar meson. The cancellation is incomplete in any other hadronic bound state, with a remainder whose scale is set by the size of one-body dressing effects.

   ↳ nucl-thhep-lathep-phnucl-exFew Body Syst.(2017)·97 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.