Tue·Sep 29, 2015Tuesday·September 29, 2015

1. 01*

   Novel Collective Phenomena in High-Energy Proton-Proton and Proton-Nucleus Collisions

   Kevin Dusling🇺🇸 · Wei Li🇺🇸 · Bjoern Schenke🇺🇸

   The observation of long-range collective correlations for particles emitted in high-multiplicity pp and pPb collisions has opened up new opportunities of investigating novel high-density QCD phenomena in small colliding systems. We review experimental results related to the studies of collective phenomena in small systems from RHIC and the LHC over the past several years. Latest development in theoretical interpretations motivated by different frameworks are also reviewed, and confronted with the experimental data. Perspectives on possible future directions are discussed, with the aim of further exploring the rich emergent QCD phenomena.

   nucl-exhep-exhep-phnucl-thIJMPE(2016)·301 citations
2. 02*

   Test of Lorentz Invarience from Compton Scattering

   Prajwal Mohanmurthy🇺🇸 · Dipangkar Dutta🇺🇸 · Amrendra Narayan🇺🇸

   In the recent times, test of Lorentz Invariance has been used as a means to probe theories of physics beyond the standard model. We describe a simple way of utilizing the polarimeters, which are a critical beam instrument at precision and intensity frontier nuclear physics labs such as the erstwhile Stanford Linear Accelerator Center (SLAC) and Jefferson Lab (JLab), to constrain the dependence of vacuum dispersion with the energy of the photons and its direction of propagation at unprecedented level of precision. We obtain a limit of minimal Standard Model extension (MSME) parameters: $\sqrt{{\kappa }_X^2+{\kappa }_Y^2}<4.6\times 10^{-10}$ and $\sqrt{{\left(2c_{TX}-({\tilde{\kappa }}_{0^{+}}^{YZ}\right)}^2+{\left(2c_{TY}-({\tilde{\kappa }}_{0^{+}}^{ZX}\right)}^2}<4.6\times 10^{-10}$. We also obtain a leading constraint for the refractive index of free space $n=1+(2.44\times 10^{-9}\pm 6.82\times 10^{-9})$.

   nucl-exphysics.ins-det4 citations
3. 03*

   Centrality dependence of identified particle elliptic flow in relativistic heavy ion collisions at sqrt(s)= 7.7--62.4 GeV

   STAR Collaboration: L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · A. Aparin · D. Arkhipkin · E. C. Aschenauer · G. S. Averichev · X. Bai · V. Bairathi and 329 other authors

   Elliptic flow (v_2) values for identified particles at midrapidity in Au + Au collisions measured by the STAR experiment in the Beam Energy Scan at the Relativistic Heavy Ion Collider at sqrt{s_{NN}}= 7.7--62.4 GeV are presented for three centrality classes. The centrality dependence and the data at sqrt{s_{NN}}= 14.5 GeV are new. Except at the lowest beam energies we observe a similar relative v_2 baryon-meson splitting for all centrality classes which is in agreement within 15% with the number-of-constituent quark scaling. The larger v_2 for most particles relative to antiparticles, already observed for minimum bias collisions, shows a clear centrality dependence, with the largest difference for the most central collisions. Also, the results are compared with A Multiphase Transport Model and fit with a Blast Wave model.

   nucl-exPRC(2016)·119 citations
4. 04*

   Hadronic resonance production and interaction in partonic and hadronic matter in EPOS3 with and without the hadronic afterburner UrQMD

   A. G. Knospe🇺🇸 · C. Markert🇺🇸 · K. Werner🇫🇷 · J. Steinheimer🇩🇪 · M. Bleicher🇩🇪

   We study the production of hadronic resonances and their interaction in the partonic and hadronic medium using the EPOS3 model, which employs the UrQMD model for the description of the hadronic phase. We investigate the centrality dependence of the yields and momentum distributions for various resonances (rho(770),K(892),phi(1020),Delta(1232),Sigma(1385),Lambda(1520),Xi(1530) and their antiparticles) in Pb-Pb collisions at sNN= 2.76 TeV. The predictions for K(892) and phi(1020) will be compared with the experimental data from the ALICE collaboration. The observed signal suppression of the K(892) with increasing centrality will be discussed with respect to the resonance interaction in the hadronic medium. The mean transverse momentum and other particle ratios such as phi(1020)/p and Omega/phi(1020) will be discussed with respect to additional contributions from the hadronic medium interactions.

   ↳ nucl-thnucl-exPRC(2016)·139 citations
5. 05*

   Jets and Centrality in p(d)-A Collisions

   M. Kordell🇺🇸 · A. Majumder🇺🇸

   The production of jets, and high-$p_T$ leading pions from jets, in d-Au collisions at the Relativistic Heavy-Ion Collider (RHIC) and p-Pb collisions at the Large Hadron Collider (LHC) are studied. Using a modified version of the event generator PYTHIA, in conjunction with a nuclear Glauber Monte-Carlo event generator, we demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile nucleon is frozen during its interaction with the extended nucleus. Using our hybrid Monte-Carlo event generator, we demonstrate that the enhancement in $R_{pA}$ seen in peripheral events at RHIC and at LHC, as well as the depletion in central or semi-central events, is mainly due to "mis-binning" of central and semi-central events with a jet, as peripheral events. This occurs due to the reduction of soft particle production caused by a depletion of energy available in a nucleon (of the deuteron in the case of d-Au collisions), after the production of a hard jet. This represents a form of "color transparency" of the projectile nucleon, which has fluctuated to a state with fewer and harder partons, in events which lead to jet production. We conclude with discussions of the form of multi-parton correlations in a nucleon which may be responsible for such a startling effect.

   ↳ nucl-thnucl-exNucl.Part.Phys.Proc.(2016)·0 citations
6. 06*

   Nuclear excitations as coupled one and two random--phase--approximation modes

   D. Gambacurta🇷🇴 · F. Catara🇮🇹 · M. Grasso🇫🇷 · M. Sambataro🇮🇹 · M. V. Andrés🇪🇸 · E. G. Lanza🇮🇹

   We present an extension of the random--phase approximation (RPA) where the RPA phonons are used as building blocks to construct the excited states. In our model, that we call double RPA (DRPA), we include up to two RPA phonons. This is an approximate and simplified way, with respect to the full second random--phase approximation (SRPA), to extend the RPA by including two particle--two hole configurations. Some limitations of the standard SRPA model, related to the violation of the stability condition, are not encountered in the DRPA. We also verify in this work that the energy--weighted sum rules are satisfied. The DRPA is applied to low--energy modes and giant resonances in the nucleus ${}^{16}$O. We show that the model (i) produces a global downwards shift of the energies with respect to the RPA spectra; (ii) provides a shift that is however strongly reduced compared to that generated by the standard SRPA. This model represents an alternative way of correcting for the SRPA anomalous energy shift, compared to a recently developed extension of the SRPA, where a subtraction procedure is applied. The DRPA provides results in good agreeement with the experimental energies, with the exception of those low--lying states that have a dominant two particle--two hole nature. For describing such states, higher--order calculations are needed.

   ↳ nucl-thnucl-exPRC(2016)·14 citations
7. 07*

   Role of the $f_1(1285)$ state in the $J/\psi \to \varphi \bar{K}{K}^{\ast }$ and $J/\psi \to \varphi f_1(1285)$ decays

   Ju-Jun Xie🇨🇳 · E. Oset🇪🇸

   We study the role of the $f_1(1285)$ resonance in the decays of $J/\psi \to \varphi \bar{K}{K}^{\ast }$ and $J/\psi \to \varphi f_1(1285)$. The theoretical approach is based on the results of chiral unitary theory where the $f_1(1285)$ resonance is dynamically generated from the $K^{\ast }\bar{K}-c.c.$ interaction. In order to further test the dynamical nature of the $f_1(1285)$ state, we investigate the $J/\psi \to \varphi \bar{K}{K}^{\ast }$ decay close to the $\bar{K}{K}^{\ast }$ threshold and make predictions for the ratio of the invariant mass distributions of the $J/\psi \to \varphi \bar{K}{K}^{\ast }$ decay and the $J/\psi \to \varphi f_1(1285)$ partial decay width with all the parameters of the mechanism fixed in previous studies. The results can be tested in future experiments and therefore offer new clues on the nature of the $f_1(1285)$ state.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2016)·9 citations
8. 08*

   Inclusive quarkonium production at forward rapidity in pp collisions at $\sqrt{s}=8$ TeV

   ALICE Collaboration

   We report on the inclusive production cross sections of J/$\psi$, $\psi$(2S), ${\rm Y}$(1S), ${\rm Y}$(2S) and ${\rm Y}$(3S), measured at forward rapidity with the ALICE detector in pp collisions at a center-of-mass energy $\sqrt{s}=8$ TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.28 pb${}^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum $p_{\mathrm{T}}$ and rapidity $y$, over the $p_{\mathrm{T}}$ ranges $0<p_{\mathrm{T}}<20$ GeV/$c$ for J/$\psi$, $0<p_{\mathrm{T}}<12$ GeV/$c$ for all other resonances, and for $2.5<y<4$. The cross sections, integrated over $p_{\mathrm{T}}$ and $y$, and assuming unpolarized quarkonia, are ${\sigma }_{\mathrm{J}/\psi }=8.98\pm 0.04\pm 0.82$ $\mu$b, ${\sigma }_{\psi (2S)}=1.23\pm 0.08\pm 0.22$ $\mu$b, ${\sigma }_{{\rm Y}(1S)}=71\pm 6\pm 7$ nb, ${\sigma }_{{\rm Y}(2S)}=26\pm 5\pm 4$ nb and ${\sigma }_{{\rm Y}(3S)}=9\pm 4\pm 1$ nb, where the first uncertainty is statistical and the second one is systematic. These values agree, within at most $1.4\sigma$, with measurements performed by the LHCb collaboration in the same rapidity range.

   ↳ hep-exnucl-exEPJC(2016)·71 citations
9. 09*

   Clustering in nuclei from ab initio nuclear lattice simulations

   Ulf-G. Meißner🇩🇪

   Nuclear Lattice Effective Field Theory is a new many-body approach that is firmly rooted in the symmetries of QCD. In particular, it allows for truly ab initio calculations of nuclear structure and reactions. In this talk, I focus on the emergence of alpha-clustering in nuclei based on this approach. I also discuss various recent achievements, the deficiencies of the chiral forces used at present and the prospects to improve upon these and the calculations of nuclear properties and dynamics.

   ↳ nucl-thhep-lathep-phnucl-ex1 citation

* 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.