Refine
Document Type
- Article (10)
- Preprint (2)
- Part of Periodical (1)
Language
- English (13)
Has Fulltext
- yes (13)
Is part of the Bibliography
- no (13)
Keywords
- Cold nuclear matter effects (1)
- J/ψ suppression (1)
- RHIC (1)
Institute
Measurement of cold nuclear matter effects for inclusive J/ψ in p+Au collisions at √sNN = 200 GeV
(2022)
Measurement by the STAR experiment at RHIC of the cold nuclear matter (CNM) effects experienced by inclusive J/ψ at mid-rapidity in 0-100% p+Au collisions at √sNN = 200 GeV is presented. Such effects are quantified utilizing the nuclear modification factor, RpAu, obtained by taking a ratio of J/ψ yield in p+Au collisions to that in p+p collisions scaled by the number of binary nucleon-nucleon collisions. The differential J/ψ yield in both p+p and p+Au collisions is measured through the dimuon decay channel, taking advantage of the trigger capability provided by the Muon Telescope Detector in the RHIC 2015 run. Consequently, the J/ψ RpAu is derived within the transverse momentum (pT) range of 0 to 10 GeV/c. A suppression of approximately 30% is observed for pT < 2 GeV/c, while J/ψ RpAu becomes compatible with unity for pT greater than 3 GeV/c, indicating the J/ψ yield is minimally affected by the CNM effects at high pT. Comparison to a similar measurement from 0-20% central Au+Au collisions reveals that the observed strong J/ψ suppression above 3 GeV/c is mostly due to the hot medium effects, providing strong evidence for the formation of the quark-gluon plasma in these collisions. Several model calculations show qualitative agreement with the measured J/ψ RpAu, while their agreement with the J/ψ yields in p+p and p+Au collisions is worse.
We report the first multi-differential measurements of strange hadrons of K −, φ and − yields as well as the ratios of φ/K − and φ/− in Au+Au collisions at √sNN = 3 GeV with the STAR experiment fixed target configuration at RHIC. The φ mesons and − hyperons are measured through hadronic decay channels, φ → K + K − and Ξ− → Λπ−. Collision centrality and rapidity dependence of the transverse momentum spectra for these strange hadrons are presented. The 4π yields and ratios are compared to thermal model and hadronic transport model predictions. At this collision energy, thermal model with grand canonical ensemble (GCE) under-predicts the φ/K − and φ/− ratios while the result of canonical ensemble (CE) calculations reproduce φ/K −, with the correlation length rc ∼ 2.7 fm, and φ/−, rc ∼ 4.2 fm, for the 0-10% central collisions. Hadronic transport models including high mass resonance decays could also describe the ratios. While thermal calculations with GCE work well for strangeness production in high energy collisions, the change to CE at 3 GeV implies a rather different medium property at high baryon density.
We report on the measurements of directed flow v1 and elliptic flow v2 for hadrons (π±, K ±, K0 S , p, φ, Λ and ) from Au+Au collisions at √sN N = 3 GeV and v2 for (π±, K ±, p and p) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the numberof-constituent-quark (NCQ) scaling holds, at 3 GeV the v2 at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the v1 slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative v2 and positive v1 slope at 3 GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.
Elliptic flow measurements from two-, four- and six-particle correlations are used to investigate flow fluctuations in collisions of U+U at sNN−−−√= 193 GeV, Cu+Au at sNN−−−√= 200 GeV and Au+Au spanning the range sNN−−−√= 11.5 - 200 GeV. The measurements show a strong dependence of the flow fluctuations on collision centrality, a modest dependence on system size, and very little if any, dependence on particle species and beam energy. The results, when compared to similar LHC measurements, viscous hydrodynamic calculations, and T$\mathrel{\protect\raisebox{-2.1pt}{R}}$ENTo model eccentricities, indicate that initial-state-driven fluctuations predominate the flow fluctuations generated in the collisions studied.
Elliptic flow measurements from two-, four- and six-particle correlations are used to investigate flow fluctuations in collisions of U+U at sNN−−−√ = 193 GeV, Cu+Au at sNN−−−√ = 200 GeV and Au+Au spanning the range sNN−−−√ = 11.5 - 200 GeV. The measurements show a strong dependence of the flow fluctuations on collision centrality, a modest dependence on system size, and very little if any, dependence on particle species and beam energy. The results, when compared to similar LHC measurements, viscous hydrodynamic calculations, and Glauber model eccentricities, indicate that initial-state-driven fluctuations predominate the flow fluctuations generated in the collisions studied.
The Tetragonoderus (Peronoscelis) quadriguttatus assemblage is a postulated monophyletic part of the intersectus complex. This assemblage is characterized against a background that includes review of a classification of the genus and comparison, in the form of a key, to other unrelated Western Hemisphere genera that share elongate tibial spurs with Tetragonoderus Dejean. The principal, easily observed feature that unites the three members (T. laevigatus Chaudoir, 1876; T. deuvei, new species (type locality: Cuijaba, Mato Grosso, Brazil), and T. quadriguttatus Dejean) of the quadriguttatus assemblage is the four-spotted elytra (two spots per elytron). These species are treated in detail, including key, synonymy (as required), comparisons, description (external and male genitalic features), habitat (if known), locality data, and geographical range map. Also, T. subfasciatus Putzeys, 1846, the elytral color pattern of whose members may be confused with the spotted pattern of the quadriguttatus assemblage, is treated similarly. The following new synonymies were established: T. quadriguttatus Dejean 1829 = T. columbicus Steinheil 1875 = T. lacordairei Chaudoir 1876 = T. tetragrammus Chaudoir 1876; and T. laevigatus Chaudoir 1876 = T. chaudoiri Liebke 1928 (replacement name for the junior homonym, T. unicolor Chaudoir, 1876). Lectotypes are designated for T. unicolor Chaudoir, T. lacordairei Chaudoir, and T. subfasciatus Putzeys. A neotype is designated for T. quadriguttatus Dejean. New distribution records in the West Indies for T. quadriguttatus are recorded for the islands of Grand Cayman, Jamaica and Hispaniola. These records may be the result of recent natural overseas dispersal from northern South America, or they may be the result of human-mediated accidental introduction, or a combination of both. The southern Floridian (Nearctic) records for T. laevigatus probably represent a recent accidental introduction through commerce, followed by dispersal through flights of adults.
Phylogenetic analysis of structural features of adults shows that the tribe Peleciini comprises eight genera, grouped in two subtribes: the southeastern Australian Agonicina (new status), including Pseudagonica Moore, 1960 (type species P. nitida Moore, 1960) and Agonica Sloane, 1920 (type species A. simsoni Sloane, 1920); and the Inabresian Peleciina (new status, with Peleciini and Disphaericini of authors), including the Neotropical Eripus Dejean, 1829 (type species E. scydmaenoides Dejean, 1829), Pelecium Kirby, 1817 (type species P. cyanipes Kirby, 1817), and Stricteripus, new genus (type species Pelecium peruvianum Straneo, 1953), the Oriental Ardistomopsis, new genus (type species Disphaericus myrmex, Andrewes, 1923), and the Afrotropical Dyschiridium Chaudoir, 1861 (type species D. ebeninum Chaudoir, 1861) and Disphaericus Waterhouse, 1842 (type species D. gambianus Waterhouse, 1842). A key is provided to distinguish among these genera, and the structural features of each genus are described and illustrated, with habitus and SEM photographs. For the genera Eripus, Pelecium, Stricteripus, and Ardistomopsis, the species are keyed and characterized in terms of structural features and geographical distribution, and illustrations of habitus and range maps are provided. Application of names is based on study of type material.
Based on adult character states, a key is provided to the seven known species of Oreodicastes Maindron 1905 (type species Oxyglossus subcyaneus Chaudoir 1843). Two new species (with type locality) are described: O. virginia (Fa zenda dos Campos, Virginia, state of Minas Gerais, Brazil) and O. zikani (Macieiras, Itatiaia, state of Rio de Janeiro, Brazil).
A taxonomic review of the lebiine sub tribe Pericalina in the Western Hemisphere, this paper includes a treatment of the genus-groups, a key to the genera, keys to subgenera, species groups, and species of each polybasic genus, descriptions of new species and new subgenera, new locality records for previously described species, re-rankings, and new synonymy. In total, 111 species and subspecies are treated, 26 of which are described as new.
The transverse momentum (pT) spectrum and nuclear modification factor (RAA) of reconstructed jets in 0–10% and 10–30% central Pb–Pb collisions at √sNN = 2.76 TeV were measured. Jets were reconstructed using the anti-kT jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet pT spectra are reported in the pseudorapidity interval of |ηjet| < 0.5 for 40 < pT, jet < 120 GeV/c in 0–10% and for 30 < pT, jet < 100 GeV/c in 10–30% collisions. Reconstructed jets were required to contain a leading charged particle with pT > 5 GeV/c to suppress jets constructed from the combinatorial background in Pb–Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb–Pb collisions had a negligible effect on the RAA. The nuclear modification factor RAA was found to be 0.28 ± 0.04 in 0–10% and 0.35 ± 0.04 in 10–30% collisions, independent of pT, jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching.
The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons1,2. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories3, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons (d) and anti-deuterons (), and 3He and nuclei carried out with the ALICE (A Large Ion Collider Experiment)4 detector in Pb–Pb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV. Our direct measurement of the mass-over-charge differences confirms CPT invariance to an unprecedented precision in the sector of light nuclei5,6. This fundamental symmetry of nature, which exchanges particles with anti-particles, implies that all physics laws are the same under the simultaneous reversal of charge(s) (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T).
We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible Λn‾ bound state. The search is performed with the ALICE detector in central (0–10%) Pb–Pb collisions at √sNN=2.76 TeV, by invariant mass analysis in the decay modes Λn‾→d‾π+ and H-dibaryon →Λpπ−. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.