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Two-particle correlations on transverse rapidity in Au+Au collisions at √sNN = 200 GeV at STAR
(2022)
Two-particle correlation measurements projected onto two-dimensional, transverse rapidity coordinates (yT1,yT2), allow access to dynamical properties of the QCD medium produced in relativistic heavy-ion collisions that angular correlation measurements are not sensitive to. We report non-identified charged-particle correlations for Au + Au minimum-bias collisions at sNN−−−√ = 200 GeV taken by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). Correlations are presented as 2D functions of transverse rapidity for like-sign, unlike-sign and all charged-particle pairs, as well as for particle pairs whose relative azimuthal angles lie on the near-side, the away-side, or at all relative azimuth. The correlations are constructed using charged particles with transverse momentum pT≥0.15 GeV/c, pseudorapidity from −1 to 1, and azimuthal angles from −π to π. The significant correlation structures that are observed evolve smoothly with collision centrality. The major correlation features include a saddle shape plus a broad peak with maximum near yT≈3, corresponding to pT≈ 1.5 GeV/c. The broad peak is observed in both like- and unlike-sign charge combinations and in near- and away-side relative azimuthal angles. The all-charge, all-azimuth correlation measurements are compared with the theoretical predictions of {\sc hijing} and {\sc epos}. The results indicate that the correlations for peripheral to mid-central collisions can be approximately described as a superposition of nucleon + nucleon collisions with minimal effects from the QCD medium. Strong medium effects are indicated in mid- to most-central collisions.
The strong force, as one of the four fundamental forces at work in the universe, governs interactions of quarks and gluons, and binds together the atomic nucleus. Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange, a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distance scales on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely ϕ and K∗0, emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for ϕ is unexpectedly large, while that for K∗0 is consistent with zero. The observed spin-alignment pattern and magnitude for the ϕ cannot be explained by conventional mechanisms, while a model with strong force fields accommodates the current data. This is the first time that the strong force field is experimentally supported as a key mechanism that leads to global spin alignment. We extract a quantity proportional to the intensity of the field of the strong force. Within the framework of the Standard Model, where the strong force is typically described in the quark and gluon language of Quantum Chromodynamics, the field being considered here is an effective proxy description. This is a qualitatively new class of measurement, which opens a new avenue for studying the behaviour of strong force fields via their imprint on spin alignment.
We report a systematic measurement of cumulants, Cn, for net-proton, proton and antiproton multiplicity distributions, and correlation functions, κn, for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at sNN−−−√ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The Cn and κn are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the BNL Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (|y|< 0.5) and transverse momentum 0.4 < pT < 2.0 GeV/c, using the STAR detector at RHIC. We observe a non-monotonic energy dependence (sNN−−−√ = 7.7 -- 62.4 GeV) of the net-proton C4/C2 with the significance of 3.1σ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with sNN−−−√. For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, κ2, of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, κ4, of protons plays a role in determining the energy dependence of proton C4/C1 below 19.6 GeV, which cannot be understood by the effect of baryon number conservation.
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.
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.
The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at √sNN = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.
We report a systematic measurement of cumulants, Cn, for net-proton, proton and antiproton, and correlation functions, κn, for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at sNN−−−√ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4 and 200 GeV. The Cn and κn are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010 -- 2017) at the Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (|y|< 0.5) and transverse momentum 0.4 < pT < 2.0 GeV/c, using the STAR detector at RHIC. We observe a non-monotonic energy dependence (sNN−−−√ = 7.7 -- 62.4 GeV) of the net-proton C4/C2 with the significance of 3.1σ for the 0-5\% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with sNN−−−√. For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, κ2, of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, κ4, of protons plays a role in determining the energy dependence of proton C4/C1 below 19.6 GeV, which cannot be solely understood by the negative values of κ2 for protons.
Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange, a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distances on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely ϕ and K∗0, emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for ϕ is unexpectedly large, while that for K∗0 is consistent with zero. The observed spin-alignment pattern and magnitude for the ϕ cannot be explained by conventional mechanisms, while a model with a connection to strong force fields, i.e. an effective proxy description within the Standard Model and Quantum Chromodynamics, accommodates the current data. This connection, if fully established, will open a potential new avenue for studying the behaviour of strong force fields.
Investigation of the linear and mode-coupled flow harmonics in Au+Au collisions at √sNN = 200 GeV
(2020)
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 modecoupled 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 √sN N= 200 GeV. The results are compared to similar LHC measurements as well as to several viscous hydrodynamic calculations with varying initial conditions.
Measurement of groomed jet substructure observables in p+p collisions at √s = 200 GeV with STAR
(2020)
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 < pT,jet < 60 GeV/c. These studies show that, in the pT,jet range accessible at √s = 200 GeV and with increasing jet resolution parameter and jet transverse momentum, the zg distribution asymptotically converges to the DGLAP splitting kernel for a quark radiating a gluon. The groomed jet radius measurements reflect a momentum-dependent narrowing of the jet structure for jets of a given resolution parameter, i.e., the larger the pT,jet, the narrower the first splitting. For the first time, these fully corrected measurements are compared to Monte Carlo generators with leading order QCD matrix elements and leading log in the parton shower, and to state-of-the-art theoretical calculations at next-to-leading-log accuracy. We observe that PYTHIA 6 with parameters tuned to reproduce RHIC measurements is able to quantitatively describe data, whereas PYTHIA 8 and HERWIG 7, tuned to reproduce LHC data, are unable to provide a simultaneous description of both zg and Rg, resulting in opportunities for fine parameter tuning of these models for p+p collisions at RHIC energies. We also find that the theoretical calculations without non-perturbative corrections are able to qualitatively describe the trend in data for jets of large resolution parameters at high pT,jet, but fail at small jet resolution parameters and low jet transverse momenta.
Quark interactions with topological gluon configurations can induce chirality imbalance and local parity violation in quantum chromodynamics. This can lead to electric charge separation along the strong magnetic field in relativistic heavy-ion collisions – the chiral magnetic effect (CME). We report measurements by the STAR collaboration of a CME-sensitive observable in p + Au and d + Au collisions at 200 GeV, where the CME is not expected, using charge-dependent pair correlations relative to a third particle. We observe strong charge-dependent correlations similar to those measured in heavy-ion collisions. This bears important implications for the interpretation of the heavy-ion data.
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.)+0.13 −0.28(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.)+1.28 −1.38(syst.) mb. We also present the values of the elastic cross section σel = 10.85 ± 0.03(stat.)+0..49 −0.41(syst.) mb, the elastic cross section integrated within the STAR t-range σ det el = 4.05 ± 0.01(stat.)+0.18−0.17(syst.) mb, and the inelastic cross section σinel = 43.82 ± 0.21(stat.)+1.37−1.44(syst.) mb. The results are compared with the world data
Johann Gottwerth Müller (1743-1828), erfolgreicher Romancier der Spätaufklärung, arbeitet zwischen 1770 und 1808 mit dreizehn Verlegern zusammen, darunter den Verlagsbuchhändlern Johann Christian Dieterich und Friedrich Nicolai. Während der Freundschafts- und Geschäftsbeziehung zu Dieterich von 1782/83 bis 1800 veröffentlicht Müller zwischen 1783 und 1791 bei ihm drei mehrbändige Romane und einen Kommentar. Die Edition der nicht komplett überlieferten Korrespondenz umfaßt dreizehn Schreiben Müllers. Inhaltlich handelt es sich um Texte, die – paradigmatisch für die Autor-/Verleger-Beziehung der Zeit – geschäftliche Aspekte wie Buchprojekte, Ausstattungs-, Druck- und Distributionsfragen behandeln, grundsätzliche Fragen der freien Schriftstellerexistenz und Verlegerabhängigkeit erörtern, aber auch private Anliegen der Freundschaft, Familien und Krankheit erwähnen.
Der spätaufklärerische Romancier und studierte, aber nicht praktizierende Mediziner (Studium 1762-1770) hinterläßt innerhalb seiner rd. 13.000 Bände umfassenden enzyklopädischen Bibliothek einen medizinalen Buchbestand von mehr als 280 Büchern. Die Ausführungen analysieren und dokumentieren diesen Bestand, der in exemplarischer Weise den medizinalen Diskurs vom 16. bis zum frühen 19. Jahrhundert vorstellt und mit den Publikationen aus dem 18. Jahrhundert den Übergang von der humoral- zum solidarpathologischen Gesundheits-, Kranksheits- und Therapieverständnis markiert.
We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine non-statistical fluctuations, perhaps related to a first or second order QCD phase transition. Such fluctuations are shown to be very small.
Directed and elliptic flow of charged pions and protons in Pb + Pb collisions at 40 and 158 A GeV
(2003)
Directed and elliptic flow measurements for charged pions and protons are reported as a function of transverse momentum, rapidity, and centrality for 40 and 158A GeV Pb + Pb collisions as recorded by the NA49 detector. Both the standard method of correlating particles with an event plane, and the cumulant method of studying multiparticle correlations are used. In the standard method the directed flow is corrected for conservation of momentum. In the cumulant method elliptic flow is reconstructed from genuine 4, 6, and 8-particle correlations, showing the first unequivocal evidence for collective motion in A+A collisions at SPS energies.
Der Forschung ist es bislang nicht gelungen, den biographischen Beginn von Charles Sealsfields USA-Aufenthaltes von 1823 bis 1826 zu klären, als er das Provinznest Kittanning zum Ausgangspunkt seiner Aktivitäten wählt. Das bezieht sich auf die Umstände von Ein- und Weiterreise, die Pseudonymisierung seines Namens als Teil des Identitätswandels, die Qualität seiner Kontakte und seines Tuns in Pennsylvania, deren Funktion für sein Identitätsverständnis und die publizistischen Anfänge. Einiges davon kann nunmehr erläutert werden.
Schreibfeder und Börsenkurse : der ökonomische Mensch Charles Sealsfield und die Affinität zum Geld
(2014)
Alexander Ritter beschreibt in "Schreibfeder und Börsenkurse. Der ökonomische Mensch Charles Sealsfield und die Affinität zum Geld" den österreichischamerikanischen Autor Charles Sealsfield als sozial desintegrierten Literaten und Börsenspekulanten mit problematischer Biografie, in der zwei Momente des divergierenden Prozesses 'storytelling' und 'economics' verknüpft seien: in seiner verwertungsorientierten Publizistik sowie im Wertpapierhandel, die sich in den narrativen Strategien des Zentralmotivs Geld/Macht in seinen Romanen bündelten. Trotz einer beeindruckenden Produktivität in den Jahren als Publizist sei die ersehnte finanzielle Absicherung und damit auch die gesellschaftliche Integration unter anderem an der Unkenntnis des amerikanischen und schweizerischen Buchmarktes gescheitert. Auf dem Hintergrund der problematischen Biografie Sealsfields führe diese Erfahrung in den 1830ern zu einer Konzentration seiner Tätigkeit auf den Wertpapierhandel; investiert werde nahezu ausschließlich in amerikanische Eisenbahngesellschaften. Der kontrollierende Blick auf das Börsengeschehen bestimme den Alltag des ehemaligen Autors. Mit der Transformation in den 'homo oeconomicus' gelinge auch die soziale und finanzielle Absicherung sowie die Stabilisierung der Persönlichkeit. Sealsfields literarisches Werk sei programmatisch am 'american pastoralism' und an den ideologischen Vorstellungen des sklavenbesitzenden Agrarkapitals der Südstaaten orientiert. An drei Beispielen führt Alexander Ritter die narrativen Strategien vor, mit denen Sealsfield die vermeintliche Zerstörung der sozialen (auch wohlfahrtlichen) Übereinkünfte durch die korrumpierte Industrie-Elite des urbanen Nordostens zurückweist, gleichzeitig aber die reaktionäre Ideologie des südstaatlichen Agrarkapitals in die unaufhaltsame Modernisierungsdynamik der Gesellschaft retten will.
Sealsfields Mobilität, die ihn zwischen 1823 und 1858 viermal zwischen den Kontinenten pendeln lässt, rhythmisiert sein Leben und Arbeiten. Sie ist die Voraussetzung seiner transatlantischen Doppelperspektive, übernationalen Geschichtssicht wie international wirksamen publizistischen Vorgehensweise und liefert die Zäsuren für ein Agieren, das in zwei Phasen erfolgt, abhängig vom Wohnsitz in den USA und in Europa. Daran orientieren sich die nachfolgenden Ausführungen. Deren Ziel ist es an Hand der Buchveröffentlichungen zu erläutern, wie Sealsfield für seine innovative Schreib- und internationalisierte Vermarktungsstrategie potente Verlage als nützliche Dienstleister funktionalisiert und so das engagierte Erzählkonzept für die Selbstorganisation im literarsozialen Gefüge des Vormärz umsetzt.
Eine zuverlässige Identitätskontrolle ist zu dieser Zeit noch nicht möglich. Man muss dem 33-jährigen plantation-owner glauben, der sich unter selbst gewählter Identität als "CMSealsfield" beim Gouverneur von Louisiana vorstellt, einen Wohnsitz in Louisiana angibt, Leumundszeugnisse präsentiert, sein Vorleben samt Taufnamen Carolus Magnus Postl verschweigt und diese nur in der Unterschrift des "safe conduct pass" (US-Schutzzusage) andeutet. Die administrierenden Herren, Gouverneur Henry Johnson (Louisiana, USA), Albin Eusèbe Michel de Grilleau, Kanzler des französischen Konsulats, und C. N. Morant, Kapitän des amerikanischen Vollschiffs "American", können nicht ahnen, dass sie dem Reisenden im Juni 1826 zu einer amerikanischen Identität mit dem anglophonen Namen Charles Sealsfield (1793-1864) verhelfen und ihn in die nationale 'machinery of identification and integration' einbeziehen. Indem Johnson den Status als 'US-resident' legitimiert, vermittelt er dem politischen Österreichflüchtling und Priester durch Identitätswechsel von Postl zu Sealsfield eine provisorisch gesicherte Existenz.
Dieser Akt ist mit weitreichenden Konsequenzen für Sealsfield verbunden. Er absolviert als 'Amerikaner' Sealsfield die Karriere eines deutschsprachigen 'amerikanischen' Autors von Amerika-Romanen (1833-47) und reüssiert 1844/45 als englischsprachiger 'amerikanischer' Autor unter der Fehlschreibung Seatsfield kurzfristig zum Protagonisten der amerikanischen Nationalliteratur, nachdem 'The Boston Daily Advertiser' am 20. März 1844 in Folge von Theodor Mundts (1808-1861) Urteil aus dem Jahr 18422 ihn als "The Greatest American Author" einer nationalen democratical American literature apostrophiert hat.