Search

We present systematic measurements of azimuthal anisotropy for strange and multistrange hadrons (Ks0, Λ, Ξ, and ω) and φ mesons at midrapidity (|y|< 1.0) in collisions of U+U nuclei at sNN=193 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. Transverse momentum (pT) dependence of flow coefficients (v2, v3, and v4) is presented for minimum bias collisions and three different centrality intervals. Number of constituent quark scaling of the measured flow coefficients in U+U collisions is discussed. We also present the ratio of vn scaled by the participant eccentricity (ɛn2) to explore system size dependence and collectivity in U+U collisions. The magnitude of v2/ɛ2 is found to be smaller in U+U collisions than that in central Au+Au collisions contradicting naive eccentricity scaling. Furthermore, the ratios between various flow harmonics (v3/v23/2, v4/v24/2) are studied and compared with hydrodynamic and transport model calculations.

The STAR Collaboration reports measurements of the transverse single-spin asymmetry (TSSA) of inclusive π0 at center-of-mass energies (s) of 200 GeV and 500 GeV in transversely polarized proton-proton collisions in the pseudo-rapidity region 2.7 to 4.0. The results at the two different energies show a continuous increase of the TSSA with Feynman-x, and, when compared to previous measurements, no dependence on s from 19.4 GeV to 500 GeV is found. To investigate the underlying physics leading to this large TSSA, different topologies have been studied. π0 with no nearby particles tend to have a higher TSSA than inclusive π0. The TSSA for inclusive electromagnetic jets, sensitive to the Sivers effect in the initial state, is substantially smaller, but shows the same behavior as the inclusive π0 asymmetry as a function of Feynman-x. To investigate final-state effects, the Collins asymmetry of π0 inside electromagnetic jets has been measured. The Collins asymmetry is analyzed for its dependence on the π0 momentum transverse to the jet thrust axis and its dependence on the fraction of jet energy carried by the π0. The asymmetry was found to be small in each case for both center-of-mass energies. All the measurements are compared to QCD-based theoretical calculations for transverse-momentum-dependent parton distribution functions and fragmentation functions. Some discrepancies are found, which indicates new mechanisms might be involved.

In 2018, the STAR collaboration collected data from 4496Ru+4496Ru and 4096Zr+4096Zr at sNN=200 GeV to search for the presence of the chiral magnetic effect in collisions of nuclei. The isobar collision species alternated frequently between 4496Ru+4496Ru and 4096Zr+4096Zr. In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data, STAR developed a three-step blind analysis procedure. Analysts are initially provided a “reference sample” of data, comprised of a mix of events from the two species, the order of which respects time-dependent changes in run conditions. After tuning analysis codes and performing time-dependent quality assurance on the reference sample, analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual ≈ 30 -min data-taking runs. For this sample, species-specific information is disguised, but individual output files contain data from a single isobar species. Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage. Following these modifications, the “frozen” code is passed over the fully un-blind data, completing the blind analysis. As a check of the feasibility of the blind analysis procedure, analysts completed a “mock data challenge,” analyzing data from Au + Au collisions at sNN=27 GeV, collected in 2018. The Au + Au data were prepared in the same manner intended for the isobar blind data. The details of the blind analysis procedure and results from the mock data challenge are presented.

We report high-precision measurements of the longitudinal double-spin asymmetry, ALL, for midrapidity inclusive jet and dijet production in polarized pp collisions at a center-of-mass energy of s=200 GeV. The new inclusive jet data are sensitive to the gluon helicity distribution, Δg(x,Q2), for gluon momentum fractions in the range from x≃0.05 to x≃0.5, while the new dijet data provide further constraints on the x dependence of Δg(x,Q2). The results are in good agreement with previous measurements at s=200 GeV and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that Δg(x,Q2) is positive for x>0.05.

We report on the W and Z/γ∗ differential and total cross sections as well as the W+/W- and (W++W-)/(Z/γ∗) cross section ratios measured by the STAR experiment at RHIC in p+p collisions at s=500 GeV and 510 GeV. The cross sections and their ratios are sensitive to quark and antiquark parton distribution functions. In particular, at leading order, the W cross section ratio is sensitive to the d¯/ū ratio. These measurements were taken at high Q2∼MW2,MZ2 and can serve as input into global analyses to provide constraints on the sea quark distributions. The results presented here combine three STAR datasets from 2011, 2012, and 2013, accumulating an integrated luminosity of 350 pb-1. We also assess the expected impact that our W+/W- cross section ratios will have on various quark distributions, and find sensitivity to the ū-d¯ and d¯/ū distributions.

In this letter, measurements of the shared momentum fraction (zg) and the groomed jet radius (Rg), as defined in the SoftDrop algorithm, are reported in p+p collisions at s=200 GeV collected by the STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from R=0.2−0.6 in the transverse momentum range 15

The STAR Collaboration at the Relativistic Heavy Ion Collider reports the first measurement of inclusive jet production in peripheral and central Au+Au collisions at sNN=200 GeV. Jets are reconstructed with the anti-kT algorithm using charged tracks with pseudorapidity |η

We report on new measurements of inclusive J/ψ polarization at midrapidity in p+p collisions at s=200 GeV by the STAR experiment at the Relativistic Heavy Ion Collider. The polarization parameters, λθ, λφ, and λθφ, are measured as a function of transverse momentum (pT) in both the helicity and Collins-Soper (CS) reference frames within pT

Flow harmonics (vn) of the Fourier expansion for the azimuthal distributions of hadrons are commonly employed to quantify the azimuthal anisotropy of particle production relative to the collision symmetry planes. While lower order Fourier coefficients (v2 and v3) are more directly related to the corresponding eccentricities of the initial state, the higher-order flow harmonics (vn>3) can be induced by a mode-coupled response to the lower-order anisotropies, in addition to a linear response to the same-order anisotropies. These higher-order flow harmonics and their linear and mode-coupled contributions can be used to more precisely constrain the initial conditions and the transport properties of the medium in theoretical models. The multiparticle azimuthal cumulant method is used to measure the linear and mode-coupled contributions in the higher-order anisotropic flow, the mode-coupled response coefficients, and the correlations of the event plane angles for charged particles as functions of centrality and transverse momentum in Au+Au collisions at nucleon-nucleon center-of-mass energy sNN= 200 GeV. The results are compared to similar LHC measurements as well as to several viscous hydrodynamic calculations with varying initial conditions.

High transverse momentum (PT) particle production is suppressed owing to the parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest PT has been difficult to measure, owing to large anisotropic backgrounds. We report a data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at √SNN = 200 GeV in the STAR experiment. The correlation shapes, for trigger particles and various associated particle PT ranges within, are consistent with Gaussians, and their widths increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.

We present a measurement of the first-order azimuthal anisotropy v1 of deuterons from Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, and 39 GeV recorded with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The energy dependence of the v1(y) slope, dv1/dy|y=0, for deuterons, where y is the rapidity, is extracted for semicentral collisions (10%-40% centrality) and compared with that of protons. While the v1(y) slopes of protons are generally negative for sNN>10GeV, those for deuterons are consistent with zero, a strong enhancement of the v1(y) slope of deuterons is seen at the lowest collision energy (the largest baryon density) at sNN=7.7GeV. In addition, we report the transverse momentum dependence of v1 for protons and deuterons. The experimental results are compared with transport and coalescence models.

We report results on the total and elastic cross sections in proton-proton collisions at s=200 GeV obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section was measured in the squared four-momentum transfer range 0.045≤−t≤0.135 GeV2. The value of the exponential slope parameter B of the elastic differential cross section dσ/dt∼e−Bt in the measured −t range was found to be B=14.32±0.09(stat.)−0.28+0.13(syst.) GeV−2. The total cross section σtot, obtained from extrapolation of the dσ/dt to the optical point at −t=0, is σtot=54.67±0.21(stat.)−1.38+1.28(syst.) mb. We also present the values of the elastic cross section σel=10.85±0.03(stat.)−0.41+0.49(syst.) mb, the elastic cross section integrated within the STAR t-range σeldet=4.05±0.01(stat.)−0.17+0.18(syst.) mb, and the inelastic cross section σinel=43.82±0.21(stat.)−1.44+1.37(syst.) mb. The results are compared with the world data.

The measurements of particle multiplicity distributions have generated considerable interest in understanding the fluctuations of conserved quantum numbers in the quantum chromodynamics (QCD) hadronization regime, in particular near a possible critical point and near the chemical freeze-out. Net-protons and net-kaons have been used as proxies for the net-baryon number and net-strangeness, respectively. We report the measurement of efficiency- and centrality-bin width-corrected cumulant ratios (C2/C1, C3/C2) of net-Λ distributions, in the context of both strangeness and baryon number conservation, as a function of collision energy, centrality, and rapidity. The results are for Au+Au collisions at five beam energies (sNN=19.6, 27, 39, 62.4, and 200 GeV) recorded with the Solenoidal Tracker at RHIC (STAR). We compare our results to the Poisson and negative binomial (NBD) expectations, as well as to ultrarelativistic quantum molecular dynamics (UrQMD) and hadron resonance gas (HRG) model predictions. Both NBD and Poisson baselines agree with data within the statistical and systematic uncertainties. UrQMD describes the measured net-ΛC1 and C3 at 200 GeV reasonably well but deviates from C2, and the deviation increases as a function of collision energy. The ratios of the measured cumulants show no features of critical fluctuations. The chemical freeze-out temperatures extracted from a recent HRG calculation, which was successfully used to describe the net-proton, net-kaon, and net-charge data, indicate Λ freeze-out conditions similar to those of kaons. However, large deviations are found when comparing with temperatures obtained from net-proton fluctuations. The net-Λ cumulants show a weak but finite dependence on the rapidity coverage in the acceptance of the detector, which can be attributed to quantum number conservation.

Open heavy-flavor hadrons provide unique probes of the medium produced in ultrarelativistic heavy-ion collisions. Due to their increased mass relative to light-flavor hadrons, long lifetime, and early production in hard-scattering interactions, they provide access to the full evolution of the partonic medium formed in heavy-ion collisions. This paper reports two-dimensional (2D) angular correlations between neutral D mesons and unidentified charged particles produced in minimum-bias Au+Au collisions at sNN=200GeV. D0 and D¯0 mesons are reconstructed via their weak decay to Kπ± using the Heavy Flavor Tracker in the Solenoidal Tracker at RHIC experiment. Correlations on relative pseudorapidity and azimuth (Δη,Δφ) are presented for peripheral, midcentral, and central collisions with D0 transverse momentum from 2-10GeV/c. Attention is focused on the 2D peaked correlation structure near the triggered D0 meson, the near-side (NS) peak, which serves as a proxy for a charm-quark-containing jet. The correlated NS yield of charged particles per D0 meson and the 2D widths of the NS peak increase significantly from peripheral to central collisions. These results are compared with similar correlations using unidentified charged particles, consisting primarily of light-flavor hadrons, at similar trigger particle momenta. Similar per-trigger yields and widths of the NS correlation peak are observed. The present results provide additional evidence that D0 mesons undergo significant interactions with the medium formed in heavy-ion collision and show, for the first time, significant centrality evolution of the NS 2D peak in the correlations of particles associated with a heavy-flavor hadron produced in these collisions.

We report on the measurement of the Central Exclusive Production of charged particle pairs h+h− (h = π, K, p) with the STAR detector at RHIC in proton-proton collisions at s = 200 GeV. The charged particle pairs produced in the reaction pp → p′ + h+h− + p′ are reconstructed from the tracks in the central detector and identified using the specific energy loss and the time of flight method, while the forward-scattered protons are measured in the Roman Pot system. Exclusivity of the event is guaranteed by requiring the transverse momentum balance of all four final-state particles. Differential cross sections are measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. They are measured in a fiducial region corresponding to the acceptance of the STAR detector and determined by the central particles’ transverse momenta and pseudorapidities as well as by the forward-scattered protons’ momenta. This fiducial region roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range 0.04 GeV2< −t1, −t2< 0.2 GeV2, invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range |η| < 0.7. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of π+π− and K+K− pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to π+π− production. For π+π− production, the fiducial cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by the continuum production and at least three resonances, the f0(980), f2(1270) and f0(1500), with a possible small contribution from the f0(1370). Fits to the extrapolated differential cross section as a function of t1 and t2 enable extraction of the exponential slope parameters in several bins of the invariant mass of π+π− pairs. These parameters are sensitive to the size of the interaction region. [Figure not available: see fulltext.].

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.

Particle production sensitive to nonfactorizable and nonperturbative processes that contribute to the underlying event associated with a high transverse momentum (pT) jet in proton+proton collisions at s=200 GeV is studied with the STAR detector. Each event is divided into three regions based on the azimuthal angle with respect to the highest-pT jet direction: In the leading jet direction ("Toward"), opposite to the leading jet ("Away"), and perpendicular to the leading jet ("Transverse"). In the Transverse region, the average charged particle density is found to be between 0.4 and 0.6 and the mean transverse momentum

J/ψ suppression has long been considered a sensitive signature of the formation of the Quark-Gluon Plasma (QGP) in relativistic heavy-ion collisions. In this letter, we present the first measurement of inclusive J/ψ production at mid-rapidity through the dimuon decay channel in Au+Au collisions at sNN=200 GeV with the STAR experiment. These measurements became possible after the installation of the Muon Telescope Detector was completed in 2014. The J/ψ yields are measured in a wide transverse momentum (pT) range of 0.15 GeV/c to 12 GeV/c from central to peripheral collisions. They extend the kinematic reach of previous measurements at RHIC with improved precision. In the 0-10% most central collisions, the J/ψ yield is suppressed by a factor of approximately 3 for pT>5 GeV/c relative to that in p+p collisions scaled by the number of binary nucleon-nucleon collisions. The J/ψ nuclear modification factor displays little dependence on pT in all centrality bins. Model calculations can qualitatively describe the data, providing further evidence for the color-screening effect experienced by J/ψ mesons in the QGP.

We present measurements of the differential cross sections of inclusive J/ψ meson production as a function of transverse momentum (pTJ/ψ) using the μ+μ- and e+e- decay channels in proton+proton collisions at center-of-mass energies of 510 and 500 GeV, respectively, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The measurement from the μ+μ- channel is for 0

We report the first measurements of a complete second-order cumulant matrix of net-charge, net-proton, and net-kaon multiplicity distributions for the first phase of the beam energy scan program at the Relativistic Heavy Ion Collider. This includes the centrality and, for the first time, the pseudorapidity window dependence of both diagonal and off-diagonal cumulants in Au+Au collisions at sNN= 7.7-200 GeV. Within the available acceptance of |η

We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at the BNL Relativistic Heavy Ion Collider. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter B2 are discussed. We find that the values of B2 for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at sNN from 19.6 to 39 GeV. In addition, values of B2 are found to vary with collision energy and show a broad minimum around sNN=20-40 GeV, which might imply a change of the equation of state of the medium in these collisions.

We present two-particle pt correlations as a function of event centrality for Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at sNN=200 GeV show a power-law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at sNN=2.76TeV from ALICE. As the collision energy is lowered from sNN=200 to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power-law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to sNN=200 GeV in contrast to previous measurements that showed little dependence on the collision energy.

We present the first measurement of the proton–Ω correlation function in heavy-ion collisions for the central (0–40%) and peripheral (40–80%) Au + Au collisions at s NN =200 GeV by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). Predictions for the ratio of peripheral collisions to central collisions for the proton–Ω correlation function are sensitive to the presence of a nucleon–Ω bound state. These predictions are based on the proton–Ω interaction extracted from (2+1)-flavor lattice QCD calculations at the physical point. The measured ratio of the proton–Ω correlation function between the peripheral (small system) and central (large system) collisions is less than unity for relative momentum smaller than 40 MeV/c. Comparison of our measured correlation ratio with theoretical calculation slightly favors a proton–Ω bound system with a binding energy of ∼ 27 MeV.

We report new STAR measurements of the single-spin asymmetries AL for W+ and W- bosons produced in polarized proton-proton collisions at s=510 GeV as a function of the decay-positron and decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb-1. The results are combined with previous results obtained with 86 pb-1. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton-proton data suggests a difference between the ū and d quark helicity distributions for 0.05

We present a measurement of inclusive J/ψ production at mid-rapidity (|y

The transverse spin transfer from polarized protons to Λ and Λ hyperons is expected to provide sensitivity to the transversity distribution of the nucleon and to the transversely polarized fragmentation functions. We report the first measurement of the transverse spin transfer to Λ and Λ along the polarization direction of the fragmenting quark, DTT, in transversely polarized proton-proton collisions at s=200 GeV with the STAR detector at RHIC. The data correspond to an integrated luminosity of 18 pb-1 and cover the pseudorapidity range |η

© 2018 authors. Published by the American Physical Society. The transverse spin transfer from polarized protons to Λ and Λ hyperons is expected to provide sensitivity to the transversity distribution of the nucleon and to the transversely polarized fragmentation functions. We report the first measurement of the transverse spin transfer to Λ and Λ along the polarization direction of the fragmenting quark, DTT, in transversely polarized proton-proton collisions at s=200 GeV with the STAR detector at RHIC. The data correspond to an integrated luminosity of 18 pb-1 and cover the pseudorapidity range |η

©) between 40 and 60 MeV/c. The absolute cross section of the excess depends weakly on centrality, while those from a theoretical model calculation incorporating an in-medium broadened ρ spectral function and radiation from a quark gluon plasma or hadronic cocktail contributions increase dramatically with an increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the pT2 distributions. © 2018 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP 3 . We report first measurements of e+e- pair production in the mass region 0.4

© 2018 New measurements of directed flow for charged hadrons, characterized by the Fourier coefficient v1, are presented for transverse momenta pT, and centrality intervals in Au+Au collisions recorded by the STAR experiment for the center-of-mass energy range sNN=7.7–200 GeV. The measurements underscore the importance of momentum conservation, and the characteristic dependencies on sNN, centrality and pT are consistent with the expectations of geometric fluctuations generated in the initial stages of the collision, acting in concert with a hydrodynamic-like expansion. The centrality and pT dependencies of v1even, as well as an observed similarity between its excitation function and that for v3, could serve as constraints for initial-state models. The v1even excitation function could also provide an important supplement to the flow measurements employed for precision extraction of the temperature dependence of the specific shear viscosity.

New measurements of directed flow for charged hadrons, characterized by the Fourier coefficient v1, are presented for transverse momenta pT, and centrality intervals in Au+Au collisions recorded by the STAR experiment for the center-of-mass energy range sNN=7.7–200 GeV. The measurements underscore the importance of momentum conservation, and the characteristic dependencies on sNN, centrality and pT are consistent with the expectations of geometric fluctuations generated in the initial stages of the collision, acting in concert with a hydrodynamic-like expansion. The centrality and pT dependencies of v1even, as well as an observed similarity between its excitation function and that for v3, could serve as constraints for initial-state models. The v1even excitation function could also provide an important supplement to the flow measurements employed for precision extraction of the temperature dependence of the specific shear viscosity.

© 2018 The Author Flow harmonics (vn) in the Fourier expansion of the azimuthal distribution of particles are widely used to quantify the anisotropy in particle emission in high-energy heavy-ion collisions. The symmetric cumulants, SC(m,n), are used to measure the correlations between different orders of flow harmonics. These correlations are used to constrain the initial conditions and the transport properties of the medium in theoretical models. In this Letter, we present the first measurements of the four-particle symmetric cumulants in Au+Au collisions at sNN=39 and 200 GeV from data collected by the STAR experiment at RHIC. We observe that v2and v3are anti-correlated in all centrality intervals with similar correlation strengths from 39 GeV Au+Au to 2.76 TeV Pb+Pb (measured by the ALICE experiment). The v2–v4correlation seems to be stronger at 39 GeV than at higher collision energies. The initial-stage anti-correlations between second and third order eccentricities are sufficient to describe the measured correlations between v2and v3. The best description of v2–v4correlations at sNN=200GeV is obtained with inclusion of the system's nonlinear response to initial eccentricities accompanied by the viscous effect with η/s>0.08. Theoretical calculations using different initial conditions, equations of state and viscous coefficients need to be further explored to extract η/s of the medium created at RHIC.

We present the first measurements of the longitudinal double-spin asymmetry ALL for dijets with at least one jet reconstructed within the pseudorapidity range 0.8

© 2018 authors. Published by the American Physical Society. We present the first measurements of the longitudinal double-spin asymmetry ALL for dijets with at least one jet reconstructed within the pseudorapidity range 0.8

The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, ALL, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass energy of 510 GeV. Results are given for transverse momenta in the range 2

Flow harmonics (vn) in the Fourier expansion of the azimuthal distribution of particles are widely used to quantify the anisotropy in particle emission in high-energy heavy-ion collisions. The symmetric cumulants, SC(m,n), are used to measure the correlations between different orders of flow harmonics. These correlations are used to constrain the initial conditions and the transport properties of the medium in theoretical models. In this Letter, we present the first measurements of the four-particle symmetric cumulants in Au+Au collisions at sNN=39 and 200 GeV from data collected by the STAR experiment at RHIC. We observe that v2 and v3 are anti-correlated in all centrality intervals with similar correlation strengths from 39 GeV Au+Au to 2.76 TeV Pb+Pb (measured by the ALICE experiment). The v2–v4 correlation seems to be stronger at 39 GeV than at higher collision energies. The initial-stage anti-correlations between second and third order eccentricities are sufficient to describe the measured correlations between v2 and v3. The best description of v2–v4 correlations at sNN=200GeV is obtained with inclusion of the system's nonlinear response to initial eccentricities accompanied by the viscous effect with η/s>0.08. Theoretical calculations using different initial conditions, equations of state and viscous coefficients need to be further explored to extract η/s of the medium created at RHIC.

Wan-Ju Hsieh,1 Chan-Jung Liang,1 Jen-Jie Chieh,4 Shu-Huei Wang,1 I-Rue Lai,1 Jyh-Horng Chen,2 Fu-Hsiung Chang,3 Wei-Kung Tseng,4–6 Shieh-Yueh Yang,4 Chau-Chung Wu,7 Yuh-Lien Chen11Institute of Anatomy and Cell Biology, College of Medicine, 2Department of Electrical Engineering, 3Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan; 4Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei, Taiwan; 5Division of Cardiology, Department of Internal Medicine, E-Da Hospital, Taipei, Taiwan; 6Department of Medical Imaging and Radiological Sciences, I-Shou University, Taipei, Taiwan; 7Department of Internal Medicine and Primary Care Medicine, National Taiwan University Hospital, Taipei, TaiwanBackground: Active targeting by specific antibodies combined with nanoparticles is a promising technology for cancer imaging and detection by magnetic resonance imaging (MRI). The aim of the present study is to investigate whether the systemic delivery of antivascular endothelial growth factor antibodies conjugating to the surface of functionalized supermagnetic iron oxide nanoparticles (anti-VEGF-NPs) led to target-specific accumulation in the tumor.Methods: The VEGF expression in human colon cancer and in Balb/c mice bearing colon cancers was examined by immunohistochemistry. The distribution of these anti-VEGF-NPs particles or NPs particles were evaluated by MRI at days 1, 2, or 9 after the injection into the jugular vein of Balb/c mice bearing colon cancers. Tumor and normal tissues (liver, spleen, lung, and kidney) were collected and were examined by Prussian blue staining to determine the presence and distribution of NPs in the tissue sections.Results: VEGF is highly expressed in human and mouse colon cancer tissues. MRI showed significant changes in the T*2 signal and T2 relaxation in the anti-VEGF-NP- injected-mice, but not in mice injected with NP alone. Examination of paraffin sections of tumor tissues stained for the iron constituent of the NPs with Prussian blue revealed a strong blue reaction in the tumors of anti-VEGF-NP-treated mice, but only a weak reaction in mice injected with NPs. In both groups, at all time points, Prussian blue-stained liver and spleen sections showed only light staining, while stained cells were rarely detected in kidney and lung sections. Transmission electron microscopy showed that many more electron-dense particles were present in endothelial cells, tumor cells, and extracellular matrix in tumor tissues in mice injected with anti-VEGF-NPs than in NP-injected mice.Conclusion: These results demonstrated in vivo tumor targeting and efficient accumulation of anti-VEGF-NPs in tumor tissues after systemic delivery in a colon cancer model, showing that anti-VEGF-NPs have potential for use as a molecular-targeted tumor imaging agent in vivo.Keywords: nanoparticles, vascular endothelial growth factor, colon tumor, magnetic resonance imaging, transmission electron microscopy

Study Objective. To assess the effectiveness, in terms of pregnancy rates, of isotopic 13 CO 2 laser laparoscopy versus traditional laparoscopy or laparotomy in the treatment of infertile women with moderate or severe endometriosis. Design. Prospective 5-year study. Setting. Medical school-affiliated hospital. Patients. Three hundred nine infertile women with moderate to severe endometriosis. Interventions. The patients were treated with one of four options: operative laparoscopy with the 13 carbon dioxide ( 13 CO 2 ) laser vaporization and/or resection, operative laparoscopy with simple electrocoagulation and sharp dissection, laparotomy with electrocoagulation and sharp dissection, and medical treatment with danazol. Estimated cumulative pregnancy rates using life table analyses were indicators of treatment of success and compared among treatments. A subgroup of 192 women considered to have endometriosis as the only infertility factor was also evaluated. Measurements and Main Results. Pregnancy rates in the laparoscopy group were equal to or higher than those of the laparotomy group, for both the entire population and the endometriosis-only subset. When the CO 2 laser was used as an adjuvant option, the rates were better, especially in patients with advanced disease and with endometriosis as the only infertility factor. Conclusion. In women with endometriosis as the only infertility factor, laparoscopic surgery with the 13 CO 2 laser was more effective than nonlaser treatment.

In order to develop a better system for support of human sperm function in vitro, we conducted studies to evaluate whether reproductive tract cells are better than non-reproductive tract cells as an adjunt in that regard.Human spermatozoa were cocultured with Vero cells, with human oviduct cells and endometrial cells, and without cells (control) for either 1, 4, or 24 hr. Sperm motility was then analyzed with a computer-aided sperm analyzer (CASA-Hamiliton Thron, HTM IVOS Motility Analyzer). Aliquots of spermatozoa incubated for 24 hr were also stained with Hoechst 33258 and FITC-PNA to evaluate the status of acrosome in live cells.Significant differences (P0.05) between the oviduct cell and the control groups after 24 hr were evident in the curvilinear velocity (VCL) (81.4 +/- 13.4 vs 60.0 +/- 14.1 microns/sec) and amplitude of lateral head displacement (ALH) (5.2 +/- 0.6 vs 4.1 +/- 0.5 microns). The incidence of acrosome reaction of live sperm was significantly higher in the endometrial cell group than in the controls (25.4 +/- 9.9 vs 6.6 +/- 2.4%; P0.001).Coculture with human reproductive tract cells seems to improve some functional parameters of human spermatozoa. Coincubation with such cell lines, especially oviduct cells, might be a feasible approach to optimization of human spermatozoa for assisted fertilization using subfertile or frozen-thawed samples. We think coincubating human spermatozoa with a human reproductive tract cell line, especially oviduct cells, might be a feasible approach in preparing human spermatozoa for assisted fertilizatioin in subfertile and frozen-thawed semen samples.

We report the cases of one patient with a right cornual pregnancy and one with a right interstitial pregnancy who were treated successfully with laparoscopic resection. In the patient with interstitial pregnancy, intra-abdominal ultrasonography was used for definite diagnosis and confirmation of complete removal of gestational tissue during the operation. These two patients were discharged within 2 days and could return to work within 1 week after the procedure. For a well experienced laparoscopist, these dangerous forms of ectopic pregnancies may not be contraindications to be laparoscopic management. For cases with uncertain diagnosis before operation, the combined use of intra-operative ultrasound is efficacious and recommended.

In 12 patients who had known or suspected intraabdominal adhesions, we evaluated the benefit of using Palmer's point for inserting the Veress needle and primary cannula during laparoscopic adhesiolysis to prevent direct intestinal injury. After inserting the laparoscope through this point, four women were found to have extreme intestinal adhesions around the umbilical area, and intestinal or severe omental injury might occur if the cannulas were inserted directly through the umbilical fossa. The other eight patients had omentum, partial to severe, adherent to the anterior abdominal wall. No complication occurred during insertion of the Veress needle and primary cannula through Palmer's point. Nine patients had successful laparoscopic adhesiolysis and were discharged within 2 days. In the other three women the procedure was converted to laparotomy because of extensive intestinal adhesions (2 patients) and small bowel injury during laparoscopic adhesiolysis (1). Palmer's point can be considered a safe and good alternative site for inserting the Veress needle and primary cannula to lyse dense intestinal and extensive omental adhesions. This technique should provide the surgeon with wider visual angel and surgical field, thus making adhesiolysis much easier to perform.

Study Objective. To assess the efficacy of 13 CO 2 laser laparoscopy in treating infertile women with minimal to mild endometriosis according the American Fertility Society classification in terms of pregnancy rates. Design. Prospective study. Setting. Medical school-affiliated hospital. Patients. One hundred seventy-six women whose infertility was associated with minimal or mild endometriosis diagnosed by laparoscopy. Interventions. The patients were treated with one of four methods: 49 underwent operative laparoscopy with newly developed 13 CO 2 laser vaporization and/or resection; 45 were treated by operative laparoscopy with simple monopolar electrocoagulation; 43 who had undergone only diagnostic laparoscopy did not receive any treatment; and 39 received danazol 800 mg/day for 3 months after diagnostic laparoscopy. Measurements and Main Results. Estimated cumulative pregnancy rates using life table analyses were indicators of treatment of success and compared among the treatments. A subgroup of 111 patients considered to have endometriosis as the only major infertility factor were also evaluated and compared among treatment options. Pregnancy rates in the CO 2 laser laparoscopy group were significantly higher than in the other three groups and in endometriosis-only subset. Conclusions. Advanced laparoscopic surgery with the CO 2 laser can be more efficient than other modalities in treating infertile women with minimal to mild endometriosis in terms of pregnancy rates. It appears that in experienced hands, laser laparoscopy has more favorable results than the other treatments.

Despite the expanding role of laparoscopic surgery in many gynaecological fields, some discrepancies still exist regarding the efficacy of laparoscopic myomectomy in treating patients with large symptomatic leiomyoma. In this report, a better operative procedure and the results of treatment are evaluated. Patients (n = 14) presenting with infertility, menorrhagia, pressure symptoms or pelvic mass associated with a large leiomyoma were managed with laparoscopic myomectomy using airlift gasless laparoscopy. Uterine size ranged from 14 to 24 weeks gestational age and the weight of the myoma ranged from 246 to 669 g (mean 454); operative time ranged from 78 to 165 min (mean 104) and blood loss from 90 to 580 ml (mean 201). No major complication occurred during the operation or follow-up. All except one patient were discharged within 72 h of the operation and resumed normal activity within 1 week. When myomectomy is indicated, the airlift gasless laparoscopic approach appears to offer a better alternative to abdominal or pneumoperitoneum laparoscopic surgery in selected cases. Airlift gasless laparoscopy has several advantages: (i) small abdominal incisions and minimal endoscopic equipment are required; (ii) the excised leiomyomata mass can be easily cut into strips and removed through the small abdominal incision; (iii) the uterine defect can be more efficiently repaired using easily performed suture techniques; (iv) high-pressure irrigation and large-volume suction devices can be used without fear of decompressing the pneumoperitoneum; and (v) the potential risk of metabolic and haemodynamic derangements during pneumoperitoneum laparoscopy are obviated. Gasless laparoscopy also has some disadvantages. The exposure obtained with gasless laparoscopy is not as good, under some circumstances, as that achieved by pneumoperitoneum. For patients who are thin, and even those with moderate obesity, the exposure obtained with airlift mechanical suspension is adequate; however, morbidly obese patients with previous abdominal surgery with suspected pelvic adhesions can incur some problems during the operation because of a poor operative field.

Construction of a neovagina using pelvic peritoneum via a laparoscopically assisted approach was used in 18 patients with congenital absence of the vagina. A better operative procedure is reported, which was modified from our preliminary technique, and the results of treatment are evaluated. Pelvic peritoneum was used for construction of a vagina, replacing a laparotomy by a minimally invasive laparoscopic approach. During follow-up, the advantages of our procedures are : (i) minimal likelihood of 'poor take' or later contraction because an autograft peritoneal epithelial line is used ; (ii) minimal short and long term care is required ; (iii) the technique is simple in experienced hands and has all the well-recognized benefits of minimal invasive surgery ; (iv) the average length of neovagina is adequate and patency and depth can be maintained with minimal dilatation ; (v) the neovagina, with epithelial lining resembling that of a normal vagina, facilitates comfortable sexual intercourse ; (vi) the procedure is unaccompanied by dyspareunia or scarring, which are frequently associated with other techniques ; (vii) less emotional stress and better cosmetic and economic benefits are noted.

Operative laparoscopy frequently requires large cannulas below or above the umbilicus, which may result in unusual complications such as small bowel herniation through these insertion sites. Three women experienced small bowel herniation through cannula incision sites, either extraumbilically or paraumbilically, after major laparoscopic surgery. Two patients who had undergone laparoscopic myomectomy developed small bowel herniation through the 12-ram extraumbilical cannula site on postoperative days 7 and 8, respectively. In the first woman, the nontender, palpable, and reducible herniation healed spontaneously, with no episode of herniation during follow-up. The second patient required laparoscopic reduction of the herniated loop and repair of the fascial defect. The last woman had undergone laparoscopic-assisted vaginal hysterectomy and developed small bowel herniation through an unrecognized fasciat defect paraumbilicalty 3 days postoperatively. Intended repair by laparoscopy was changed to laparotomy due to extensive and incarcerated bowel herniation.

Some discrepancies still exist with regard to the efficacy of laparoscopic removal of large symptomatic leiomyomas. In our experience, when performing myomectomy, airlift gasless laparoscopy has several advantages. First, a small incision can be made, through which conventional surgical instruments (endoscopic equipment is not required) are inserted and the myomectomy is efficiently performed. Second, the large excised leiomyoma can be cut into strips easily with a conventional long knife and removed through a small abdominal incision. Third, sutures can be placed easily, and the surgeon can place fingers through a small surgical wound to palpate the organ and tie the knot directly. Fourth, high-pressure irrigation and large-volume suction devices can be used without fear of decompressing the pneumoperitoneum. Finally, the potential risks of metabolic and hemodynamic instability due to carbon dioxide insufflation to establish pneumoperitoneum are avoided.

Seventeen patients who had known or suspected intra-abdominal adhesions underwent laparoscopic surgery with the use of Palmer's Point for insertion of the operative laparoscope. Five of them were found to have extensive periumbilical adhesions. Intestinal or omental injury can occur if the trocar is inserted directly through the umbilical fossa. Though the incidence of direct trauma is reportedly low, there were still mild to moderate omental adhesions to the anterior abdominal wall, as we expected, in the remaining 12 patients. Possible inadequate aspiration and irrigation during laparoscopic removal of a dermoid cyst in one woman had resulted in severe postsurgical intraabdominal adhesions. More than two 10 mm incisions were used in our patients for insertion of the laparoscope interchangeablely to facilitate the procedure of laparoscopic adhesiolysis. The operative field can be expanded greatly. Fourteen patients completed the laparoscopic surgery, and the other 3 had alternative procedures eventually. No complications occurred during the laparoscopic procedure. The postoperative courses were uneventful in all 17 patients. Our experience suggests that Palmer's Point is a good alternative for insertion of the Veress needle and laparoscope in patients with previous laparotomies and suspected severe pelvic adhesions.