Thu·Jun 21, 2018Thursday·June 21, 2018

1. 01*

   Measuring hydrodynamical expansion via the production of identified hadrons in Pb$-$Pb collisions with ALICE

   Nicolò Jacazio (for the ALICE Collaboration)🇮🇹

   During the LHC Run-2, ALICE has collected data from Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. The centrality dependence of identified particle production, including elliptic ($v_2$) and higher harmonic flow coefficients ($v_3,v_4$), has been measured. The high-precision measurement of transverse momentum ($p_{\mathrm{T}}$) differential elliptic flow of the $\varphi$-meson (whose mass is close to that of the proton) allows for a unique testing of mass ordering at low $p_{\mathrm{T}}$ as well as baryon and meson grouping at intermediate $p_{\mathrm{T}}$. The $p_{\mathrm{T}}$-differential hadron spectra are presented and, together with flow coefficients, compared with state-of-the-art calculations from models based on relativistic hydrodynamics coupled with UrQMD. The added transport code is to describe rescattering in the hadronic phase, which has been successful in describing the $p_{\mathrm{T}}$-spectra of identified particles up to a few GeV/$c$. Moreover, results from the simultaneous Blast-Wave fit to the $p_{\mathrm{T}}$ distributions are compared across multiple collisions energies and system sizes in order to address the evolution of collective behaviour from small systems to large systems.

   nucl-exhep-ex3 citations
2. 02*

   Azimuthal correlations of the longitudinal structure of the mid-rapidity charged-particle multiplicity in Pb-Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 2.76 TeV with ALICE

   Saehanseul Oh (for the ALICE Collaboration)🇺🇸

   Studies of longitudinal correlations of the charged-particle multiplicity in heavy-ion collisions have provided insights into the asymmetry and fluctuations of the initial-state collision geometry. In addition to the expansion of the medium in the transverse direction, commonly quantified using Fourier coefficients ($v_n$), the initial geometry and resulting longitudinal expansion as a function of azimuthal angle enable us to better understand the full 3-dimensional picture of heavy-ion collisions. In these proceedings, azimuthal correlations of the longitudinal structure of charged-particle multiplicity are reported for Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV. The azimuthal angle distribution is divided into regions of in-plane and out-of-plane with respect to the second-order event plane, and the coefficients of Legendre polynomials are estimated from a decomposition of the longitudinal structure of the charged-particle multiplicity at midrapidity ($|\eta |<0.8$) on an event-by-event basis in each azimuthal region for different centralities. Correlations between the coefficients of various orders in different azimuthal regions are studied and exhibit collective features of longitudinal structure in the azimuthal direction. The results are compared with HIJING and AMPT simulations.

   nucl-exJ.Phys.Conf.Ser.(2018)·0 citations
3. 03*

   Nonperturbative factorization breaking and color entanglement effects in dihadron and direct photon-hadron angular correlations in $p$$+$$p$ and $p$$+$A collisions

   Joseph D. Osborn🇺🇸

   New predictions regarding the role of color flow in high energy Quantum Chromodynamics (QCD) processes have emerged in the last decade. In particular, the role of color flow is now being explored through many different observables; one such observable is nearly back-to-back hadron correlations in proton-proton collisions which are predicted to be sensitive to states that are entangled via their QCD color charge. The PHENIX detector at the Relativistic Heavy Ion Collider is well suited to study potential effects from color flow. Angular correlations between nearly back-to-back hadrons or a direct photon-hadron are measured to study the prediction of color entanglement or factorization breaking. The correlations can be treated in a transverse-momentum-dependent framework where sensitivity to non-Abelian effects from color are predicted. These measurements are the first ever to search for experimental evidence of these entangled states and will help establish color flow in hadronic interactions as a new area of focus within QCD research. Results are presented for proton-proton collisions at center-of-mass energies of 200 and 510 GeV and proton-nucleus collisions at nucleon-nucleon center-of-mass energies of 200 GeV. World measurements of processes where factorization is predicted to hold are also compiled and analyzed to compare to the new experimental results presented here. The measured results do not indicate any obvious qualitative differences from observables where factorization is predicted to hold. This indicates that quantitative comparisons with phenomenological calculations will be necessary to identify the magnitude of effects from color entanglement. As QCD is the only non-Abelian quantum field theory known to exist in nature that admits bound states, it will be essential to continue exploring unique QCD phenomena due to color interactions in controlled ways in the coming years.

   ↳ hep-exnucl-ex0 citations
4. 04*

   There Is No Proof of Thermalized Quark-Gluon Plasma at RHIC and LHC

   Gouranga C Nayak🇺🇸

   Although Tevatron has discovered top quark and LHC (pp collisions) has discovered Higgs boson but the RHIC and LHC heavy-ion colliders have not discovered thermalized quark-gluon plasma (QGP). This is because the experimental data of top quark at Tevatron and the experimental data of Higgs boson at LHC are compared with the exact first principle calculation but the experimental data at RHIC and LHC are compared with simplistic models and assumptions which are not exact first principle calculation. In this paper we show that the exact first principle method to study quark-gluon plasma at RHIC and LHC is the nonequilibrium-nonperturbative QCD by using closed-time path integral formalism. Hence in the absence of such exact first principle calculation we conclude that there is no proof of thermalized quark-gluon plasma at RHIC and LHC.

   ↳ hep-phhep-exhep-latnucl-ex+10 citations
5. 05*

   Evaluation of noise limits of a precision ADC for direct digital signal integration of magnetic measurements

   Roberto Cavazzana · Marco Gottardo · Andrea Rigoni Garola

   The characterization of laboratory plasma instabilities, magnetic reconnection and turbulence associated phenomena, require the simultaneous signal sampling from arrays of magnetic sensors (hundreds or even thousands) to obtain spatial resolution, with several hundred kHz for time resolution. Magnetic measurements based on pick-up (Mirnov) coil are quite common in experimental pulsed devices for plasma research, thanks to their simplicity and reliability. Being the signal from this type of sensor proportional to the time variation of the magnetic field ($dB/dt$), it has to be time-integrated to recover the instant value of magnetic field. Depending on the required integration time usually either analog integrators or chopped integrators are used. However these solutions tend to limit the frequency bandwidth in the kHz range, they are not easy to design and build, and require additional fast channels to directly acquire the $dB/dt$ signal to recover the plasma dynamic features at higher frequencies. In this paper we evaluate the feasibility of using a direct single channel precision ADC to allow the simultaneous acquisition of $dB/dt$ measurements and to provide the integrated B measurement by means of digital integration on the new RFX-mod2 device. On this purpose we interfaced an existing ADC-module to a Xilinx Zynq FPGA, in order to evaluate the intrinsic noise and to investigate the feasible integration window of this configuration. The result opens the door to a compact, cost-effective and reliable acquisition system, usable for simultaneous real-time control and transient signal recording, scalable from tenths to thousands channels, applicable to a broad class of pulsed plasma experimental devices.

   ↳ physics.ins-detnucl-ex0 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.