3,459 research outputs found
Measurement of Longitudinal Spin Asymmetries for Weak Boson Production in Polarized Proton-Proton Collisions at RHIC
No full textWe report measurements of single- and double-spin asymmetries for W[superscript ±] and Z/γ[superscript ∗] boson production in longitudinally polarized p + p collisions at √s = 510 GeV by the STAR experiment at RHIC. The asymmetries for W[superscript ±] were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton’s polarized quark distributions at the scale of the W mass. The results are compared to theoretical predictions, constrained by polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range 0.05 < x < 0.2.Brookhaven National LaboratoryLawrence Berkeley National LaboratoryUnited States. Dept. of Energy. Office of Nuclear PhysicsUnited States. Dept. of Energy. Office of High Energy PhysicsNational Science Foundation (U.S.
[J over ψ] polarization in p+p collisions at √s = 200 TeV in STAR
No full textWe report on a polarization measurement of inclusive [J over ψ] mesons in the di-electron decay channel at mid-rapidity at 2<p[subscript T]<6 GeV/c in p+p collisions at √s = 200 GeV. Data were taken with the STAR detector at RHIC. The [J over ψ] polarization measurement should help to distinguish between different models of the [J over ψ] production mechanism since they predict different p[subscript T] dependences of the [J over ψ] polarization. In this analysis, [J over ψ] polarization is studied in the helicity frame. The polarization parameter λ[subscript θ] measured at RHIC becomes smaller towards high p[subscript T], indicating more longitudinal [J over ψ] polarization as p[subscript T] increases. The result is compared with predictions of presently available models.United States. Dept. of Energy. Office of ScienceNational Science Foundation (U.S.
Beam Energy Dependence of Moments of the Net-Charge Multiplicity Distributions in Au + Au Collisions at RHIC
No full textWe report the first measurements of the moments—mean (M), variance (σ[superscript 2]), skewness (S), and kurtosis (κ)—of the net-charge multiplicity distributions at midrapidity in Au + Au collisions at seven energies, ranging from √s[subscript NN] = 7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, σ[superscript 2]/M, Sσ, and κσ[superscript 2], with the expectations from Poisson and negative binomial distributions (NBDs). The Sσ values deviate from the Poisson baseline and are close to the NBD baseline, while the κσ[superscript 2] values tend to lie between the two. Within the present uncertainties, our data do not show nonmonotonic behavior as a function of collision energy. These measurements provide a valuable tool to extract the freeze-out parameters in heavy-ion collisions by comparing with theoretical models.Brookhaven National LaboratoryLawrence Berkeley National LaboratoryUnited States. Dept. of Energy. Office of Nuclear PhysicsUnited States. Dept. of Energy. Office of High Energy PhysicsNational Science Foundation (U.S.
Q[subscript weak]: First Direct Measurement of the Proton’s Weak Charge
No full textThe Q[subscript weak] experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q² = 0.025 (GeV/c)². The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis
J/ψ Production at High Transverse Momenta in P+p and Au + Au Collisions at √SNN=200 GeV
No full textWe report J/ψ spectra for transverse momenta p[subscript T]> 5GeV/c at mid-rapidity in p+p and Au+Au collisions at √sNN=200GeV. The inclusive J/ψ spectrum and the extracted B-hadron feed-down are compared to models incorporating different production mechanisms. We observe significant suppression of the J/ψ yields for p[subscript T] > 5GeV/c in 0-30% central Au+Au collisions relative to the p+p yield scaled by the number of binary nucleon-nucleon collisions in Au+Au collisions. In 30-60% mid-central collisions, no such suppression is observed. The level of suppression is consistently less than that of high-p[subscript T]π[superscript ±] and low-p[subscript T]J/ψ at RHIC and high-p[subscript T]J/ψ at the LHC. Keywords: J/ψ, suppression, Color-screening, Quarkonium, Heavy-ion collisions, STARNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Author Correction: Auto-aggressive CXCR6+ CD8 T cells cause liver immune pathology in NASH
No full textIn this Article, the surname of Tobias Boettler was incorrectly shown as ‘Böttler’, and the surname of author Jan-Philipp Mallm was incorrectly shown as ‘Malm’. The original Article has been corrected online
Fluctuations of charge separation perpendicular to the event plane and local parity violation in √S[subscript NN] = 200 GeV Au + Au collisions at the BNL Relativistic Heavy Ion Collider
No full textPrevious experimental results based on data (∼15 × 10[superscript 6] events) collected by the STAR detector at the BNL Relativistic Heavy Ion Collider suggest event-by-event charge-separation fluctuations perpendicular to the event plane in noncentral heavy-ion collisions. Here we present the correlator previously used split into its two component parts to reveal correlations parallel and perpendicular to the event plane. The results are from a high-statistics 200-GeV Au + Au collisions data set (57 × 10[superscript 6] events) collected by the STAR experiment. We explicitly count units of charge separation from which we find clear evidence for more charge-separation fluctuations perpendicular than parallel to the event plane. We also employ a modified correlator to study the possible P-even background in same- and opposite-charge correlations, and find that the P-even background may largely be explained by momentum conservation and collective motion.Brookhaven National LaboratoryLawrence Berkeley National LaboratoryOpen Science GridUnited States. Dept. of Energy. Office of ScienceNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Stochastical inference in the model of extreme events
No full textTitle: Stochastical inference in the model of extreme events Author: Jan Dienstbier Department/Institute: Department of probability and mathematical statistics Supervisor of the doctoral thesis: Doc. RNDr. Jan Picek, CSc. Abstract: The thesis deals with extremal aspects of linear models. We provide a brief explanation of extreme value theory. The attention is then turned to linear models Yn×1 = Xn×pβp×1 + En×1 with the errors Ei ∼ F, i = 1, . . . , n fulfilling the do- main of attraction condition. We examine the properties of the regression quantiles of Koenker and Basset (1978) under this setting we develop theory dealing with extremal characteristics of linear models. Our methods are based on an approximation of the regression quantile process for α ∈ [0, 1] expanding older results of Gutenbrunner et al. (1993). Our result holds in [α∗ n, 1 − α∗ n] with a better rate of α∗ n → 0 than the other approximations described previously in the literature. Consecutively we provide an ap- proximation of the tails of regression quantile. The approximations of the tails enable to develop theory of the smooth functionals, which are used to establish a new class of estimates of extreme value index. We prove T(F−1 n (1 − knt/n)) is consistent and asymp- totically normal estimate of extreme for any T member of the class...
Event-plane-dependent dihadron correlations with harmonic v[subscript n] subtraction in Au + Au collisions at √s[subscript NN] = 200 GeV
No full textSTAR measurements of dihadron azimuthal correlations (Δϕ) are reported in midcentral (20–60%) Au + Au collisions at √s[subscript NN] = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, ϕ[subscript s] = |ϕ[subscript t] − ψ[subscript EP]|. The elliptic (v[subscript 2]), triangular (v[subscript 3]), and quadratic (v[subscript 4]) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d + Au collisions. It is found that a finite near-side (|Δϕ| π/2) correlation shows a modification from d + Au data, varying with ϕ[subscript s]. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD.United States. Dept. of Energy. Office of Nuclear PhysicsUnited States. Dept. of Energy. Office of High Energy PhysicsNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Demonstration of a healthy young adult walking under the conditions tested in Experiment 2.
No full textAuthor name: Ryan T. Roemmich, PhD. Videographer: Jan Stenum, PhD. Participant: Ryan T. Roemmich, PhD. Length: 1:51. Size: 77,700 MB. (MP4)</p
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