Journals
2016 EN
L. Adamczyk · J. K. Adkins · G. Agakishiev
+325 more
Balance functions have been measured in terms of relative pseudorapidity (Delta(eta)) for charged particle pairs at the BNL Relativistic Heavy Ion Collider from Au + Au collisions at root s(NN) = 7.7 GeV to 200 GeV using the STAR detector. These results are compared with balance functions measured at the CERN Large Hadron Collider from Pb + Pb collisions at root s(NN) = 2.76 TeV by the ALICE Collaboration. The width of the balance function decreases as the collisions become more central and as the beam energy is increased. In contrast, the widths of the balance functions calculated using shuffled events show little dependence on centrality or beam energy and are larger than the observed widths. Balance function widths calculated using events generated by UrQMD are wider than the measured widths in central collisions and show little centrality dependence. The measured widths of the balance functions in central collisions are consistent with the delayed hadronization of a deconfined quark gluon plasma (QGP). The narrowing of the balance function in central collisions at root s(NN) = 7.7 GeV implies that a QGP is still being created at this relatively low energy
American Physical Society
Journals
2016 EN
J. Adamczewski-Musch · G. Agakishiev · O. Arnold
+103 more
We report on the first measurement of $p\Lambda$ and $pp$ correlations viathe femtoscopy method in p+Nb reactions at $\mathrm{\sqrt{s_{NN}}=3.18}~\mathrm{GeV}$, studied with the High Acceptance Di-Electron Spectrometer(HADES). By comparing the experimental correlation function to modelcalculations, a source size for $pp$ pairs of $r_{0,pp}=2.02 \pm0.01(\mathrm{stat})^{+0.11}_{-0.12} (\mathrm{sys}) ~\mathrm{fm}$ and a slightlysmaller value for $p\Lambda$ of $r_{0,\Lambda p}=1.62 \pm0.02(\mathrm{stat})^{+0.19}_{-0.08}(\mathrm{sys}) ~\mathrm{fm}$ is extracted.Using the geometrical extent of the particle emitting region, determinedexperimentally with $pp$ correlations as reference together with a sourcefunction from a transport model, it is possible to study different sets ofscattering parameters. The $p\Lambda$ correlation is proven sensitive topredicted scattering length values from chiral effective field theory. Wedemonstrate that the femtoscopy technique can be used as valid alternative tothe analysis of scattering data to study the hyperon-nucleon interaction.
American Physical Society
Journals
2016 EN
L. Adamczyk · J. K. Adkins · G. Agakishiev
+322 more
We present measurements of second-order azimuthal anisotropy (v(2)) at midrapidity (vertical bar y vertical bar (root s(NN) = 200, 62.4, 39, 27, and 19.6 GeV) and (3)(He) over bar (root s(NN) = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The v(2) for these light nuclei produced in heavy-ion collisions is compared with those for p and (p) over bar. We observe mass ordering in nuclei v(2)(p(T)) at low transverse momenta (p(T) . The magnitude of v(2) for t and He-3 agree within statistical errors. Light-nuclei v(2) are compared with predictions from a blast-wave model. Atomic mass number (A) scaling of light-nuclei v(2)(p(T)) seems to hold for p(T)/A < 1.5 GeV/c. Results on light-nuclei v(2) from a transport-plus-coalescence model are consistent with the experimental measurements
American Physical Society
Journals
2016 EN
STAR Collaboration · L. Adamczyk · J. K. Adkins
+335 more
We present a measurement of the inclusive production of Upsilon mesons in U+Ucollisions at 193 GeV at mid-rapidity (|y| < 1). Previous studies in centralAu+Au collisions at 200 GeV show a suppression of Upsilon(1S+2S+3S) productionrelative to expectations from the Upsilon yield in p+p collisions scaled by thenumber of binary nucleon-nucleon collisions (Ncoll), with an indication thatthe Upsilon(1S) state is also suppressed. The present measurement extends thenumber of participant nucleons in the collision (Npart) by 20% compared toAu+Au collisions, and allows us to study a system with higher energy density.We observe a suppression in both the Upsilon(1S+2S+3S) and Upsilon(1S) yieldsin central U+U data, which consolidates and extends the previously observedsuppression trend in Au+Au collisions.
American Physical Society
Journals
2016 EN
J. Adamczewski-Musch · G. Agakishiev · O. Arnold
+106 more
The inclusive production of {\Lambda} hyperons in proton-proton collisions at$\sqrt{s}$ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum f\"urSchwerionenforschung in Darmstadt. The experimental data are compared to adata-based model for individual exclusive {\Lambda} production channels in thesame reaction. The contributions of intermediate resonances such as{\Sigma}(1385), {\Delta}++ or N* are considered in detail. In particular, theresult of a partial wave analysis is accounted for the abundant pK$^+${\Lambda}final state. Model and data show a reasonable agreement at mid rapidities,while a difference is found for larger rapidities. A total {\Lambda} productioncross section in p+p collisions at $\sqrt{s}$ = 3.18 GeV of {\sigma}(pp $\to${\Lambda} + X) = 207.3 $\pm$ 1.3 +6.0 -7.3 (stat.) $\pm$ 8.4 (syst.) +0.4 -0.5(model) {\mu}b is found.
American Physical Society
Journals
2016 EN
Stuart L. Shapiro · Jessie Shelton
We reinvestigate the effect of annihilations on the distribution ofcollisionless dark matter (DM) in a spherical density spike around a massiveblack hole. We first construct a very simple, pedagogic, analytic model for anisotropic phase space distribution function that accounts for annihilation andreproduces the "weak cusp" found by Vasiliev for DM deep within the spike andaway from its boundaries. The DM density in the cusp varies as $r^{-1/2}$ for$s$-wave annihilation, where $r$ is the distance from the central black hole,and is not a flat "plateau" profile. We then extend this model by incorporatinga loss cone that accounts for the capture of DM particles by the hole. The losscone is implemented by a boundary condition that removes capture orbits,resulting in an anisotropic distribution function. Finally, we evolve aninitial spike distribution function by integrating the Boltzmann equation toshow how the weak cusp grows and its density decreases with time. We treat twocases, one for $s$-wave and the other for $p$-wave DM annihilation, adoptingparameters characteristic of the Milky Way nuclear core and typical WIMP modelsfor DM. The cusp density profile for $p$-wave annihilation is weaker, varyinglike $\sim r^{-0.34}$, but is still not a flat plateau.
American Physical Society
Journals
2016 EN
Yi Pang · Ergin Sezgin · Yaodong Zhu
We compute one loop free energy for D=4 Vasiliev higher spin gravities basedon Konstein-Vasiliev algebras hu(m;n|4), ho(m;n|4) or husp(m;n|4) and subjectto higher spin preserving boundary conditions, which are conjectured to be dualto the U(N), O(N) or USp(N) singlet sectors, respectively, of free CFTs on theboundary of $AdS_4$. Ordinary supersymmetric higher spin theories appear asspecial cases of Konstein-Vasiliev theories, when the corresponding higher spinalgebra contains $OSp({\cal N}|4)$ as subalgebra. In $AdS_4$ with $S^3$boundary, we use a modified spectral zeta function method, which avoids theambiguity arising from summing over infinite number of spins. We find that thecontribution of the infinite tower of bulk fermions vanishes. As a result, thefree energy is the sum of those which arise in type A and type B models withinternal symmetries, the known mismatch between the bulk and boundary freeenergies for type B model persists, and ordinary supersymmetric higher spintheories exhibit the mismatch as well. The only models that have a match aretype A models with internal symmetries, corresponding to $n=0$. The matchingrequires identification of the inverse Newton's constant $G_N^{-1}$ with $N$plus a proper integer as was found previously for special cases. In $AdS_4$with $S^1\times S^2$ boundary, the bulk one loop free energies match those ofthe dual free CFTs for arbitrary $m$ and $n$. We also show that asupersymmetric double-trace deformation of free CFT based on OSp(1|4) does notcontribute to the ${\cal O}(N^0)$ free energy, as expected from the bulk.
American Physical Society
Journals
2016 EN
PANDA Collaboration · B. Singh · W. Erni
+508 more
The exclusive charmonium production process in $\bar{p}p$ annihilation withan associated $\pi^0$ meson $\bar{p}p\to J/\psi\pi^0$ is studied in theframework of QCD collinear factorization. The feasibility of measuring thisreaction through the $J/\psi\to e^+e^-$ decay channel with the PANDA(AntiProton ANnihilation at DArmstadt) experiment is investigated. Simulationson signal reconstruction efficiency as well as the background rejection fromvarious sources including the $\bar{p}p\to\pi^+\pi^-\pi^0$ and $\bar{p}p\toJ/\psi\pi^0\pi^0$ reactions are performed with PandaRoot, the simulation andanalysis software framework of the PANDA experiment. It is shown that themeasurement can be done at PANDA with significant constraining power under theassumption of an integrated luminosity attainable in four to five months ofdata taking at the maximum design luminosity.
American Physical Society
Journals
2016 EN
STAR Collaboration · L. Adamczyk · J. K. Adkins
+327 more
We present high precision measurements of elliptic flow near midrapidity($|y|<1.0$) for multi-strange hadrons and $\phi$ meson as a function ofcentrality and transverse momentum in Au+Au collisions at center of mass energy$\sqrt{s_{NN}}=$ 200 GeV. We observe that the transverse momentum dependence of$\phi$ and $\Omega$ $v_{2}$ is similar to that of $\pi$ and $p$, respectively,which may indicate that the heavier strange quark flows as strongly as thelighter up and down quarks. This observation constitutes a clear piece ofevidence for the development of partonic collectivity in heavy-ion collisionsat the top RHIC energy. Number of constituent quark scaling is found to holdwithin statistical uncertainty for both 0-30$\%$ and 30-80$\%$ collisioncentrality. There is an indication of the breakdown of previously observed massordering between $\phi$ and proton $v_{2}$ at low transverse momentum in the0-30$\%$ centrality range, possibly indicating late hadronic interactionsaffecting the proton $v_{2}$.
American Physical Society
Journals
2016 EN
STAR Collaboration · L. Adamczyk · J. K. Adkins
+328 more
We present results from a harmonic decomposition of two-particle azimuthalcorrelations measured with the STAR detector in Au+Au collisions for energiesranging from $\sqrt{s_{NN}}=7.7$ GeV to 200 GeV. The third harmonic$v_3^2\{2\}=\langle \cos3(\phi_1-\phi_2)\rangle$, where $\phi_1-\phi_2$ is theangular difference in azimuth, is studied as a function of the pseudorapiditydifference between particle pairs $\Delta\eta = \eta_1-\eta_2$. Non-zero{\vthree} is directly related to the previously observed large-$\Delta\eta$narrow-$\Delta\phi$ ridge correlations and has been shown in models to besensitive to the existence of a low viscosity Quark Gluon Plasma (QGP) phase.For sufficiently central collisions, $v_3^2\{2\}$ persist down to an energy of7.7 GeV suggesting that QGP may be created even in these low energy collisions.In peripheral collisions at these low energies however, $v_3^2\{2\}$ isconsistent with zero. When scaled by pseudorapidity density of charged particlemultiplicity per participating nucleon pair, $v_3^2\{2\}$ for centralcollisions shows a minimum near {\snn}$=20$ GeV.
American Physical Society