p/pi Ratio in Di-Hadron Correlations

Particle ratios are important observables used to constrain models of particle production in heavy-ion collisions. In this work we report on a measurement of the p/pi ratio in the transverse momentum range 2.0 < p_{T,assoc} < 4.0 GeV/c, associated with a charged trigger particle of 5.0 < p_{T,trig} < 10.0 GeV/c, in 0-10% central Pb--Pb collisions at sqrt{s_{NN}}=2.76 TeV. The ratio is measured in the jet peak and in a region at large Delta eta separation from the peak (bulk region). The presented results are based on 14M minimum-bias Pb--Pb collisions, recorded by the ALICE detector. It is observed that the p/pi ratio in the bulk region is compatible with the p/pi ratio of an inclusive measurement, and is much larger than the p/pi ratio in the jet peak. The p/pi ratio in the jet peak is compatible with a PYTHIA reference, in which fragmentation in the vacuum is the dominant mechanism of particle production

Azimuthal correlations of forward di-hadrons in d+Au collisions at RHIC in the Color Glass Condensate

We present a good description of recent experimental data on forward di-hadron azimuthal correlations measured in deuteron-gold collisions at RHIC, where monojet production has been observed. Our approach is based on the Color Glass Condensate effective theory for the small-x degrees of freedom of the nuclear wave function, including the use of non-linear evolution equations with running QCD coupling. Our analysis provides further evidence for the presence of saturation effects in RHIC data.Comment: 4 pages, 2 figures, version to appear in PR

Evaluation of Strategies to Enhance NCLEX-RN Success

Successful performance on the National Council Licensure Examination for Registered Nurses (NCLEX-RN) is a measure of competence indicating that newly licensed nurses have attained standards to ensure safe nursing practice. Concerned about a declining pass rate, one urban state university implemented multiple strategies over a period of time in order to enhance the success rate of frrst-time test-takers. The purpose of this research project was to focus on the state university\u27s NCLEX-RN pass rates for frrst-time candidates, examined and evaluated new implemented strategies, and determined how the interventions influenced these pass rates. Data were collected using retrospective existing records on a sample of 680 subjects .. These included more stringent admission criteria, several testing modalities, and students\u27 progression policies. Passage of the NCLEX-RN exam assures the competencies required for safe patient care. Findings indicate a variety of strategies could be implemented by other Schools of Nursing to enhance their students\u27 success

Measurements of Lambda, Lambda-bar and K-short from Pb-Pb collisions at 158 GeV per nucleon in a large acceptance experiment

The main reason for studying relativistic heavy-ion collisions is to discover the phase transition from nuclear matter to the Quark-Gluon Plasma. Such a transition is predicted to occur under conditions of high temperature and density. The predicted state features deconfined quarks and gluons as the relevant degrees of freedom instead of colour-singlet hadrons. These new degrees of freedom should lead to an enhanced production of strange quarks which has directly observable consequences on the composition of the final state hadrons detected in such a collision. The NA49 experiment is able to measure hadronic production in central Pb+Pb collisions. It uses a Pb beam, of energy 158 GeV per nucleon, from the CERN SPS with a fixed Pb target. The experiment features four large tracking detectors which can measure the trajectories of charged particles. In this thesis the method of reconstructing neutral strange particles, Lambda, Lambda-bar and K-short from their charged decay products is described. The procedure for correcting the raw yields for losses due to the limited experimental acceptance and efficiency in reconstruction is explained. An estimate of some systematic errors is made. The resulting rapidity distributions, which span either side of mid-rapidity are peaked (with the possible exception of Lambda) and the transverse momentum spectra fit the Hagedorn distribution. The inverse slope parameters, T_Lambda = 274 ± 5 MeV, T_Lambda-bar = 279 ± 10 MeV and T_K = 238 ± 5 MeV are consistent with the picture of transverse flow observed in these collisions. These results are compared with other measurements

Strange and identified hadron production at the LHC with ALICE

The ALICE detector was designed to identify hadrons over a wide range of transverse momentum at mid-rapidity. Here measurements of light charged ({\pi}, K, p) and neutral ({\Lambda}, K0S) hadrons in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV are presented with additional data from a pp reference at sqrt(s) = 7 TeV. Such measurements are crucial for understanding the properties of the fireball produced in heavy-ion collisions at the LHC. The particle-type dependence of the spectra and the yields of particles extracted give information on the expansion dynamics and chemical composition respectively. In addition studying the ratio of baryons to mesons may help in understanding the mechanisms by which hadronisation takes place. We find that, when comparing to data at sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC, a more strongly expanding system is created with a similar relative population of hadron species. We also see that collective effects or complex mechanisms responsible for a relative enhancement of baryons have an influence at a much higher pT than was previously seen.Comment: 6 pages, 4 figures; EPIC@LHC - International Workshop on Early Physics with heavy-Ion Collisions at LHC, Bari (Italy), 6-8 July 2011; submitted proceedings (fixed cut and paste error in abstract

Upsilon cross section in p+p collisions at STAR

The main focus of the heavy flavor program at RHIC is to investigate the properties of the dense matter produced in heavy-ion collisions by studying its effect on open heavy flavor and quarkonia production. This in turn requires a detailed understanding of their production in elementary p+p collisions so that the dense matter effects can be later unfolded. In this paper, we present the first mid-rapidity cross section measurement of bottomonium at $\sqrt{s}=200$ GeV with the STAR experiment. We compare our results with perturbative QCD calculations. A brief status on the study of charmonium in STAR is given.Comment: 4 pages, 4 figures. To appear in the proceedings of Quark Matter 2006 as a special issue of Journal of Physics G: Nuclear and Particle Physic

The first measurement of BB meson semi-leptonic decay contribution to non-photonic electrons at RHIC

We present the first measurement for the $B$ meson semi-leptonic decay contribution to non-photonic electrons at RHIC using non-photonic electron azimuthal correlations with charged hadrons in p+p collisions at $\sqrt{s_{NN}} = 200$ GeV from STAR.Comment: 4 pages, 3 figures, Quark Matter 2006 Proceedings, to appear in J. Phys.

Physics with Identified Particles at STAR

New physics results with identified particles at STAR are presented. Measurements at low $p_T$ address bulk properties of the collision, while those at high $p_T$ address jet energy loss in the bulk matter produced. Between these extremes, measurements at intermediate $p_T$ address the interplay between jets and the bulk. We highlight: measurements of $v_2$ fluctuations as a new, sensitive probe of the initial conditions and the equation of state; correlations involving multi-strange particles, along with ratios of identified particles to test coalescence as a mechanism of particle production at intermediate $p_T$; three particle azimuthal correlation to search for conical emission; and the energy and particle-type dependence of hadron production at high $p_T$ to study quark and gluon jet energy loss.Comment: 9 pages, 7 figures. To appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai, China, November 14-20, 200

Selected results on Strong and Coulomb-induced correlations from the STAR experiment

Using recent high-statistics STAR data from Au+Au and Cu+Cu collisions at full RHIC energy I discuss strong and Coulomb-induced final state interaction effects on identical ($\pi-\pi$) and non-identical ($\pi-\Xi$) particle correlations. Analysis of $\pi-\Xi$ correlations reveals the strong and Coulomb-induced FSI effects allowing for the first time to estimate space extension of $\pi$ and $\Xi$ sources and average shift between them. Source imaging technique providing clean separation of these effects from effects due to the source function itself is applied to one-dimensional relative momentum correlation function of identical pions. For low momentum pions and/or non-central collisions large departure from a single-Gaussian shape is observed

Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR

We have measured 2D autocorrelations for all charged hadrons in STAR with $p_{t}$ $>$ 0.15 GeV/c and $| \eta |$ $<$ 1 from Au+Au collisions at 62 and 200 GeV. The correlation structure is dominated by a peak centered at zero relative opening angles on $\eta$ and $\phi$ which we hypothesize is caused by minimum-bias jets (minijets). We observe a large excess of minijet correlations in more-central Au-Au collisions relative to binary-collision scaling (more correlated pairs than expected from surface emission or even volume emission). We also observe a sudden increase of the minijet peak amplitude and $\eta$ width relative to binary-collision scaling of scattered partons which occurs at an energy-dependent centrality point. There is a possible scaling of the transition point with transverse particle density.Comment: Quark Matter 2008 proceedings, submitted to Journal of Physics G. v2: added STAR Collaboration to author lis