In high-energy heavy-ion collisions, partonic collectivity is evidenced by the constituent quark number scaling of elliptic flow anisotropy for identified hadrons. A breaking of this scaling and ...dominance of baryonic interactions is found for identified hadron collective flow measurements in sNN = 3 GeV Au+Au collisions. In this paper, we report measurements of the first- and second-order azimuthal anisotropic parameters, v1 and v2, of light nuclei (d, t, 3He, 4He) produced in sNN = 3 GeV Au+Au collisions at the STAR experiment. An atomic mass number scaling is found in the measured v1 slopes of light nuclei at mid-rapidity. For the measured v2 magnitude, a strong rapidity dependence is observed. Unlike v2 at higher collision energies, the v2 values at mid-rapidity for all light nuclei are negative and no scaling is observed with the atomic mass number. Calculations by the Jet AA Microscopic Transport Model (JAM), with baryonic mean-field plus nucleon coalescence, are in good agreement with our observations, implying baryonic interactions dominate the collective dynamics in 3 GeV Au+Au collisions at RHIC.
We report the beam energy (sqrtsNN=7.7-200 GeV) and collision centrality dependence of the mean (M), standard deviation (σ), skewness (S), and kurtosis (κ) of the net-proton multiplicity ...distributions in Au+Au collisions. The measurements are carried out by the STAR experiment at midrapidity (|y|<0.5) and within the transverse momentum range 0.4<pT<0.8 GeV/c in the first phase of the Beam Energy Scan program at the Relativistic Heavy Ion Collider. These measurements are important for understanding the quantum chromodynamic phase diagram. The products of the moments, Sσ and κσ2, are sensitive to the correlation length of the hot and dense medium created in the collisions and are related to the ratios of baryon number susceptibilities of corresponding orders. The products of moments are found to have values significantly below the Skellam expectation and close to expectations based on independent proton and antiproton production. The measurements are compared to a transport model calculation to understand the effect of acceptance and baryon number conservation and also to a hadron resonance gas model.
According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have ...the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron and a Λ hyperon. With data recorded by the STAR detector1–3 at the Relativistic Heavy Ion Collider, we measure the Λ hyperon binding energy BΛ for the hypertriton, and find that it differs from the widely used value4 and from predictions5–8, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon–nucleon interaction9,10 and have implications for understanding neutron star interiors, where strange matter may be present11. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness, and we observe no deviation from the expected exact symmetry.The STAR collaboration reports a measurement of the mass difference and binding energy of the hypertriton and its antiparticle. This work constrains the hyperon–nucleon interaction and allows us to test the CPT theorem in a nucleus with strangeness.
In tropical cropping systems, a better understanding of P transformations and short-term P cycling during decomposition of incorporated residues is pertinent. The primary objectives of this study ...were (i) to assess P immobilization in decomposing residues of sorghum (Sorghum bicolor (L.) Moench.) and crotalaria (Crotalaria juncea L.), (ii) to establish the role of soil fungi in the process, and (iii) to determine the contribution of P immobilization in explaining differences in soil P availability from plant residues in two weathered soils (Ultisol and Alfisol). Phosphorus associated with particulate organic matter (POM-P) was measured at different residue decomposition stages. Irradiated and nonirradiated residues were utilized to evaluate the origin of fungal colonization of particulate organic matter (POM). Results indicate a significant release of P from the residues at early stages of decomposition. An average of 93 and 76% of the initial POM-P was released after 5 d of decomposition in the Ultisol and Alfisol, respectively; and no significant differences were found between the residue types. After this initial 5-d period, significantly higher values of POM-P were observed for sorghum (5.8 and 7.9 mg P kg-1) as compared with crotalaria (1.9 and 2.8 mg P kg-1) in the two soils, suggesting a higher P immobilization in decomposing sorghum residue. Phosphorus immobilization represented up to 30% of the P in the residues and it could account for observed differences in P availability in the amended soils. A correspondence between patterns of P accumulation and fungal colonization of POM suggested that soil fungi might be responsible for this P immobilization. Further research is required however, to identify the mechanisms regulating this fungal colonization and P immobilization of plant residues in tropical acid soils.
We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at s=500 GeV by the STAR experiment at RHIC. The ...measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.
Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge ...separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies.
Although nitrogen (N) is an essential nutrient that is a key component of intensive irrigated agricultural systems, its management
to maximize yields and reduce losses to the environment is ...difficult. One reason is due to the spatial and temporal variability
that affect residual soil nitrate-N (NO 3 -N) and NO 3 -N leaching potential. The objective of this study was to evaluate the potential of N fertilization prescriptions based on
site-specific management zones to reduce NO 3 -N leaching losses. We mapped site-specific management zones based on soil color from aerial photographs, topography, and
the producer's past management experiences that reflect spatial soil variability. We used the Nitrate Leaching and Economic
Analysis Package (NLEAP) model to assess the benefits of N management based on site-specific management zones. Nitrate leaching
was variable across management zones with the highest leaching occurring in the low productivity zone. This study found that
productivity zone is an important spatial factor in determining NO 3 -N leaching potential since site-specific management zones characterized the variability of factors that affect NO 3 -N leaching. As the N fertilizer rate is increased by productivity zone the rate of NO 3 -N leaching increased faster for the low productivity zone creating a â higher leaky zone. â Since we found that a factor other than N is limiting yields, a better N management practice is to apply N accounting by
realistic maximum yields to avoid over-fertilization, to reduce NO 3 -N leaching losses during the growing season and residual soil NO 3 -N that is available to leach during the non-growing season. Furthermore, this study demonstrates that spatially variable
N management based on productivity zones produces less NO 3 -N leaching than uniform strategies while maintaining maximum yield. We estimated that by using a Site Specific Management
Zone we cut NO 3 -N leaching losses by 25 percent during the first year after a site-specific management zones nutrient management plan.
We report the direct virtual photon invariant yields in the transverse momentum ranges 1<pT<3 GeV/c and 5<pT<10 GeV/c at mid-rapidity derived from the dielectron invariant mass continuum region ...0.10<Mee<0.28 GeV/c2 for 0–80% minimum-bias Au+Au collisions at sNN=200 GeV. A clear excess in the invariant yield compared to the nuclear overlap function TAA scaled p+p reference is observed in the pT range 1<pT<3 GeV/c. For pT>6 GeV/c the production follows TAA scaling. Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield.
We report precision measurements of hypernuclei $^3_ΛH$ and $^4_ΛH$ lifetimes obtained from Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV and 7.2 GeV collected by the STAR experiment at the ...Relativistic Heavy Ion Collider, and the first measurement of $^3_ΛH$ and $^4_ΛH$ midrapidity yields in Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV. $^3_ΛH$ and $^4_ΛH$, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be 221 ± 15 (stat) ± 19 (syst) ps for $^3_ΛH$ and 218 ± 6 (stat) ± 13 (syst) ps for $^4_ΛH$. The pT-integrated yields of $^3_ΛH$ and $^4_ΛH$ are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of $4_ΛH$ is different for 0%–10% and 10%–50% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the $^3_ΛH$ yield well, while underestimating the $^4_ΛH$ yield. Transport models, combining baryonic mean-field and coalescence (jam) or utilizing dynamical cluster formation via baryonic interactions (phqmd) for light nuclei and hypernuclei production, approximately describe the measured $^3_ΛH$ and $^4_ΛH$ yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.
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