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We report the first measurement of inclusive antiproton production at midrapidity in Au+Au collisions at sqrt[sNN] = 130 GeV by the STAR experiment at RHIC. The antiproton transverse mass distributions in the measured transverse momentum range of 0.25<pperp<0.95 GeV/c are found to fall less steeply for more central collisions. The extrapolated antiproton rapidity density is found to scale approximately with the negative hadron multiplicity density.
We report results on the ratio of midrapidity antiproton-to-proton yields in Au+Au collisions at sqrt[sNN] = 130 GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of | y|<0.5 and 0.4<pt<1.0 GeV/c, the ratio is essentially independent of either transverse momentum or rapidity, with an average of 0.65±0.01(stat)±0.07(syst) for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the p-p-bar pair production becomes important at midrapidity, a significant excess of baryons over antibaryons is still present.
Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at sqrt(s_NN)=130 GeV using the STAR TPC at RHIC. The elliptic flow signal, v_2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.
Purpose: The aim of this study was to investigate characteristics associated with ectopic pregnancy (EP) that could be utilized for predicting morbidity or mortality.
Methods: This was a retrospective analysis of pregnancy-related records from a tertiary center over a period of ten years. Data on age, gravidity, parity, EP risk, amenorrhea duration, abdominal pain presence and location, β-human chorionic gonadotropin (β-HCG) level, ultrasound findings, therapeutic intervention, exact EP implantation site and length of hospital stay (LOS) were obtained from the database. The LOS was used as a proxy for morbidity and was tested for an association with all variables. All statistical analyses were conducted with Stata® (ver. 16.1, Texas, USA).
Results: The incidence of EP in a cohort of 30,247 pregnancies over a ten-year period was 1.05%. Patients presented with lower abdominal pain in 87.9% of cases, and the likelihood of experiencing pain was tenfold higher if fluid was detectable in the pouch of Douglas. Only 5.1% of patients had a detectable embryonic heartbeat, and 18.15% had one or more risk factors for EP. While most EPs were tubal, 2% were ovarian. The LOS was 1.9 days, and laparoscopic intervention was the main management procedure. The cohort included one genetically proven dizygotic heterotopic pregnancy (incidence, 3.3 × 10− 5) that was diagnosed in the 7th gestational week. The only association found was between the β-HCG level and LOS, with a linear regression β coefficient of 0.01 and a P-value of 0.04.
Conclusion: EP is a relatively common condition affecting approximately 1% of all pregnancies. β-HCG correlates with EP-related morbidity, but the overall morbidity rate of EP is low regardless of the implantation site. Laparoscopic surgery is an effective therapeutic procedure that is safe for managing EP, even in cases of heterotopic pregnancy.
The results from the STAR Collaboration on directed flow (v1), elliptic flow (v2), and the fourth harmonic (v4) in the anisotropic azimuthal distribution of particles from Au+Au collisions at sqrt[sNN]=200GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v2, scaling with the number of constituent quarks and parton coalescence are discussed. For v4, scaling with v22 and quark coalescence are discussed.
We present a systematic analysis of two-pion interferometry in Au+Au collisions at sqrt[sNN]=200GeV using the STAR detector at Relativistic Heavy Ion Collider. We extract the Hanbury-Brown and Twiss radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianness of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast-wave parametrizations. The expansion of the source and its relation with the initial energy density distribution is studied.