Wed·Aug 12, 2015Wednesday·August 12, 2015

1. 01*

   Probing Pb+Pb collisions at $\sqrt{S_{NN}}=2760$ GeV with spectators

   Vipul Bairathi🇮🇳 · Sandeep Chatterjee🇮🇳 · Md. Rihan Haque🇮🇳 · Bedangadas Mohanty🇮🇳

   There is event by event geometric as well as quantum fluctuations in the initial condition of heavy-ion collisions. The standard technique of analysing heavy-ion collisions in bins of centrality obtained from final state multiplicity averages out the various initial configurations and thus restricts the study to only a limited range of initial conditions. In this paper, we propose an additional binning in terms of total spectator neutrons in an event. This offers us a key control parameter to probe events with broader range of initial conditions providing us an opportunity to peep into events with rarer initial conditions which otherwise get masked when analysed by centrality binning alone. We find that the inclusion of spectator binning allows one to vary ${\epsilon }_2$ and ${\epsilon }_3$ independently. We observe that the standard scaling relation between $v_2/{\epsilon }_2$ and $\frac{1}{S}\frac{d{N}_{\text{ch}}}{d\eta }$ exhibited by centrality bins is broken by the spectator neutron bins. However, the acoustic scaling relation between $\ln \left(v_n/{\epsilon }_n\right)$ and transverse system size holds for both centrality as well as spectator bins for central to mid-central collisions. The introduction of the spectator binning allows us to tune over a wide range viscosity driven effects for events with varying initial states but similar final state multiplicity.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2016)·5 citations
2. 02*

   Strong diquark correlations inside the proton

   Jorge Segovia🇪🇸

   Quantum Chromodynamics is thought to be the relativistic quantum field theory that describes the strong interaction of the Standard Model. This interaction produces mesons but it is also able to generate quark-quark (diquark) correlations inside baryons. In this work, we employ a continuum approach to QCD based on Dyson-Schwinger equations to calculate the electromagnetic form factors of the proton and analyze in a deeper way the consequences of having strong diquark correlations. Comparison with the experimental data reveals that the presence of strong diquark correlations within the proton is sufficient to understand empirical extractions of the flavour-separated form factors. The explained reduction of the ratios $F_1^d/F_1^u$ and $F_2^d/F_2^u$ at high $Q^2$ in the quark-diquark picture are responsible of the precocious scaling of the $F_2^p/F_1^p$ observed experimentally.

   ↳ nucl-thhep-exhep-lathep-ph+1EPJ Web Conf.(2016)·0 citations
3. 03*

   Di-photon "Ridge" in p+p and p+A collisions at RHIC and the LHC

   Alex Kovner🇺🇸 · Amir H. Rezaeian🇨🇱

   We obtain prompt di-photon cross-section in proton-nucleus collisions in Hamiltonian light-cone approach within a hybrid approximation, treating the projectile proton in the parton model and the target nucleus in the Color-Glass-Condensate approach. We study in details the di-photon correlations in quark-nucleus and proton-nucleus collisions at RHIC and the LHC. We show that the single fragmentation di-photon produces the away side correlations peak, and the double fragmentation component of prompt di-photon is responsible for the near-side peak, and the long-range in rapidity near-side azimuthal collimation, the so-called "ridge" structure. We study the transverse momentum, density and energy dependence of the di-photon ridge and show that it strongly depends on the kinematics and saturation dynamics. We show that while di-photon ridge exists at the LHC in quark-nucleus collisions, the effect disappears in proton-nucleus collisions at the LHC. At RHIC the ridge-type structure persists at low transverse momenta of di-photon even in proton-nucleus collisions. We argue that di-photon correlation measurments in p+A collisions can help to discriminate among models and understand the true origin of the observed di-hadron ridge in p+A collisions. We also show that in addition to the ridge structure, prompt di-photon correlation also exhibits some distinct novel features, including the emergence of away side double-peak structure at intermediate transverse momenta.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2015)·22 citations
4. 04*

   Sensitivity of flow harmonics to sub-nucleon scale fluctuations in heavy ion collisions

   Jacquelyn Noronha-Hostler (Columbia U.)🇺🇸 · Jorge Noronha (Sao Paulo U. & Columbia U.)🇧🇷 · Miklos Gyulassy (Columbia U.)🇺🇸

   In this paper a new procedure to smooth out the initial energy densities of hydrodynamics is employed to show that the initial spatial eccentricities ${\epsilon }_{m,n}$, which drive the final state flow harmonics $v_n$, are remarkably robust with respect to variations of the underlying scale of initial energy density spatial gradients, $\lambda$, in nucleus-nucleus collisions. For $\sqrt{s}=2.76$ TeV Pb+Pb collisions, the ${\epsilon }_{m,n}$'s (across centrality classes) change by less than $10\%$ if the scale of fluctuations is varied from $0.1$ to $1$ fm. We show, using the 2+1 Lagrangian hydrodynamic code, v-USPhydro, that this robustness is transferred to the final $v_n$'s computed within event by event viscous hydrodynamics. This indicates that the flow harmonics in nucleus-nucleus collisions are not yet particularly sensitive to the underlying microscopic sub-nucleon physics below the confinement scale. On the other hand, the eccentricities of top $1\%$ high multiplicity $\sqrt{s}=5.02$ TeV p+Pb collisions are found to be very sensitive to sub-nucleonic scale fluctuations, which should be contrasted with the robustness found in peripheral Pb+Pb collisions with the same multiplicity.

   ↳ nucl-thhep-phnucl-exPRC(2016)·84 citations
5. 05*

   New sum rule for the nuclear magnetic polarizability

   Mikhail Gorchtein🇩🇪

   I extend the well-known photonuclear sum rule that relates the strength of the photoexcitation of the giant dipole resonance in a nucleus to the number of elementary scatterers-nucleons to the case of virtual photons. The new sum rule relates the size of the magnetic polarizability of a nucleus to the slope of the transverse virtual photoabsorption cross section integrated over the energy in the nuclear range. I check this sum rule for the deuteron where necessary data is available, discuss possible applications and connection with other sum rules postulated in the literature.

   ↳ nucl-thhep-phnucl-exPRL(2015)·8 citations
6. 06*

   Effects of kinematic cuts on net-electric charge fluctuations

   Frithjof Karsch🇩🇪 · Kenji Morita🇯🇵 · Krzysztof Redlich🇵🇱

   The effects of kinematic cuts on electric charge fluctuations in a gas of charged particles are discussed. We consider a very transparent example of an ideal pion gas with quantum statistics, which can be viewed as a multi-component gas of Boltzmann particles with different charges and masses. Cumulants of net-electric charge fluctuations ${\chi }_n^Q$ are calculated in a static and expanding medium with flow parameters adjusted to the experimental data. We show that the transverse momentum cut, $p_{t_{\text{min}}}\le p_t\le p_{t_{\text{max}}}$, weakens the effects of Bose statistics, i.e. contributions of effectively multi-charged states to higher order moments. Consequently, cuts in $p_t$ modify the experimentally measured cumulants and their ratios. We discuss the influence of kinematic cuts on the ratio of mean and variance of electric charge fluctuations in a hadron resonance gas, in the light of recent data of the STAR and PHENIX Collaborations. We find that the different momentum cuts of $p_{t_{\text{min}}}=0.2$~GeV (STAR) and $p_{t_{\text{min}}}=0.3$~GeV (PHENIX) are responsible for more than 30\% of the difference between these two data sets. We argue that the $p_t$ cuts imposed on charged particles will influence the normalized kurtosis {${\kappa }_Q{\sigma }_Q^2={\chi }_4^Q/{\chi }_2^Q$} of the electric charge fluctuations. In particular, the reduction of ${\kappa }_Q{\sigma }_Q^2$ with increasing $p_{t_{\text{min}}}$ will lead to differences between PHENIX and STAR data of $\mathcal{O}(6\%)$ which currently are buried under large statistical and systematic errors. We furthermore introduce the relation between momentum cut-off and finite volume effects, which is of relevance for the comparison between experimental data and lattice QCD calculations.

   ↳ hep-phhep-latnucl-exnucl-thPRC(2016)·49 citations
7. 07*

   Toward an automated analysis of slow ions in nuclear track emulsion

   K.Z. Mamatkulov🇷🇺 · R.R. Kattabekov🇷🇺 · I. Ambrozova · D.A. Artemenkov🇷🇺 · V. Bradnova🇷🇺 · D.V. Kamanin · L. Majling · A. Marey · O. Ploc · V.V. Rusakova🇷🇺 · R. Stanoeva🇧🇬 · K. Turek and 3 other authors

   Application of the nuclear track emulsion technique (NTE) in radioactivity and nuclear fission studies is discussed. It is suggested to use a HSP-1000 automated microscope for searching for a collinear cluster tri-partition of heavy nuclei implanted in NTE. Calibrations of $\alpha$-particles and ion ranges in a novel NTE are carried out. Surface exposures of NTE samples to a ${}^{252}$Cf source started. Planar events containing fragments and long-range $\alpha$-particles as well as fragment triples only are studied. NTE samples are calibrated by ions Kr and Xe of energy of 1.2 and 3 A MeV.

   ↳ physics.ins-detnucl-exPhys.Procedia(2015)·5 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.