Directed flow in Au+Au collisions from the RHIC Beam Energy Scan at the STAR experiment

We report results of $v_1(y)$ and $dv_1/dy$ near mid-rapidity for $\pi^{\pm}$, $K^{\pm}$, $K_s^0$, $p$, $\overline{p}$, $\Lambda$, $\overline{\Lambda}$ and $\phi$ from Beam Energy Scan Au+Au collisions at $\sqrt{s_{NN}} =$ 7.7 - 200 GeV using the STAR detector at RHIC. The $dv_{1}/dy$ of $\pi^{\pm}$, $K^{\pm}$ and $K_s^0$ mesons remains negative over all beam energies. The $dv_1/dy$ of $p$ and $\Lambda$ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net $\Lambda$) indicate a double sign change. The $dv_1/dy$ of $\overline{p}$, $\overline{\Lambda}$ and $\phi$ show a similar trend for $\sqrt{s_{NN}}>$ 14.5 GeV. For the first time, $v_{1}$ measurements are used to test a quark coalescence hypothesis. Many measurements are found to be consistent with the particles being formed via coalescence of constituent quarks. The observed deviations from that consistency offer a new approach for probing the collision process at the quark level.Comment: 7 pages, 4 figures to appear in CPOD 2017 proceedings, PoS(CPOD2017)00

Strange hadron and resonance production in Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV with ALICE experiment at LHC

The ALICE experiment at the LHC has measured the production of strange hadrons and resonances in Pb-Pb and pp collisions at unprecedented high beam energies. The study of strange hadrons and resonances helps us to understand the properties of the medium created in the heavy-ion collisions and its evolution. We present the yields ($dN/dy$) at mid-rapidity for strange hadrons ($\Lambda$, $\Xi^{-}$, $\Omega^{-}$, their anti-particles and $K_{S}^{0}$) and resonances ($\phi$ and $K^{*0}$) for several collision centrality intervals. The results from Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are presented and compared to corresponding results from pp collisions and lower energy measurements. Baryon to meson ratios and resonance to non-resonance particle ratios relative to pp collisions are shown as a function of collision centrality and compared with the results at lower energies.Comment: 4 pages, 3 figures (Quark Matter 2012 proceedings

Hadronic Resonance Production with ALICE Experiment at LHC

The production of resonances in heavy-ion collisions is expected to be sensitive to the properties of strongly interacting matter created in such collisions. We report on the measurements of $\phi$ and $K^{*0}$ resonances in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The masses, widths and yields in Pb-Pb collisions as a function of centrality are compared to that in pp collisions to understand the role of re-scattering and regeneration. The resonance to non-resonance particle ratios are shown as a function of collision centrality and compared with the results at lower energies.Comment: 4 pages, 8 figures (submitted CPOD 2013 proceedings

Scattering phase shifts in quasi-one-dimension

Scattering of an electron in quasi-one dimensional quantum wires have many unusual features, not found in one, two or three dimensions. In this work we analyze the scattering phase shifts due to an impurity in a multi-channel quantum wire with special emphasis on negative slopes in the scattering phase shift versus incident energy curves and the Wigner delay time. Although at first sight, the large number of scattering matrix elements show phase shifts of different character and nature, it is possible to see some pattern and understand these features. The behavior of scattering phase shifts in one-dimension can be seen as a special case of these features observed in quasi-one-dimensions. The negative slopes can occur at any arbitrary energy and Friedel sum rule is completely violated in quasi-one-dimension at any arbitrary energy and any arbitrary regime. This is in contrast to one, two or three dimensions where such negative slopes and violation of Friedel sum rule happen only at low energy where the incident electron feels the potential very strongly (i.e., there is a very well defined regime, the WKB regime, where FSR works very well). There are some novel behavior of scattering phase shifts at the critical energies where $S$-matrix changes dimension.Comment: Minor corrections mad