Advances in imaging the Alpine crust and mantle

The dense coverage of the AlpArray Seismic Network and related targeted arrays (LOBSTER, Swath D, EASI) has led to numerous new models of the Alpine orogenic lithosphere, slabs and mantle above the Mantle Transition Zone. We highlight some novel features of these models, how they may help to answer old questions, as well as pose new questions: (1) P-wave images from teleseismic travel-time tomography (Paffrath et al., 2021a,b; Handy et al., 2021) use an innovative approach to include the highly heterogeneous Alpine orogenic crust in their model. In addition to confirming previous models for partial slab detachment beneath the Western Alps, they find evidence for a long (≥300 km), subvertical slab anomaly underneath the Eastern Alps that is detached from the orogenic lithosphere at 70-150 km depth. The latter corroborates images from surface-wave tomographic studies (Kaestle et al., 2018), but contrasts with other past- and present images indicating deeper slab detachment (Handy et al., 2015) and/or a through-going connection of the slab with Adriatic lithosphere (e.g., Plomerová et al., 2022). Cooperation of the Bochum and Prague groups to explain these disparate features reveal that crucial features, e.g., the connection of slabs with the orogenic lithosphere, depends strongly the geometry of the model area and the chosen crustal model. (2) New receiver function (RF) studies extracted signals in the Eastern Alps where previous work only imaged a ‘Moho gap’ (Hetényi et al., 2018; Kind et al., 2021; Mroczek et al., 2023, Michailos et al., 2023). These studies confirm the notion of marked, along-strike variations in structure: in the west (TRANSALP, 11.9°E), the European Moho is clearly down-going (e.g., Kummerow et al., 2004), whereas in the east (14°E), competing interpretations range between an underlying Adriatic Moho (Hetényi et al., 2018) and a downgoing European interface to more than 100 km depth (Mroczek et al., 2023). All methods indicate that the upper-plate Moho shallows from the E. Alps to the Pannonian Basin. (3) The internal structure of the Eastern Alpine crust is imaged with local earthquake (Jozi Najafabadi et al., 2021) and ambient noise tomography (Molinari et al., 2020; Qorbani et al., 2020; Sadeghi-Bagherabadi et al., 2021; Kästle et al., this vol.). The LET models show a bulge-shaped fast anomaly just to the south of the western Tauern window, possibly indicating stacking of lower crustal nappes, probably of both European and Adriatic affinity (McPhee et al., this vol.), and a fast anomaly east of the Giudicarie Fault that may be related to a Permian magmatic body, as also indicated by gravity studies (Spooner et al., 2021). (4) AlpArray has opened the door to study crustal and mantle anisotropy in unprecedented detail (Kästle et al., 2022; Soergl et al., 2022; Kästle et al., this vol.). SKS studies (e.g., Hein et al., 2021) suggest that mantle flows around slabs and potentially through slab tears, in the Western and Eastern Alps. Newest results indicate that crustal anisotropy in the Eastern Alps is layered, with an upper layer with fast directions oriented mainly orogen-parallel, approximately following major Neogene oblique-slip faults exposed at the surface. The studies also show a clear distinction between the fast-axis orientations within the Alps and in its foreland. The latter results are in excellent agreement with findings from SKS studies, indicating similar dynamics affecting the entire lithosphere. The detailed analysis of Swath-D data conducted by Link et al. (2021) has further been able to show a sharp transition in SKS splitting orientations at around 13° longitude, that is indicative of the separate evolution of central and eastern Alps. (5) Preliminary results from the joint inversion of surface- and body-wave data provide a better understanding of the different sensitivities of P- and S-waves to the upper mantle structures under the Alps. Initial results of a P-wave velocity model from teleseismic full-waveform inversion (FWI, Friederich et al., this vol.) provide surprisingly high resolution in the crust and uppermost mantle with clear images of the Alpine orogenic roots and anomalies within the crust (e.g., Ivrea Body, E. Alps lower crustal bulge). The resulting FWI model is independent of any crustal correction and may provide a vital contribution to ongoing discussions on slab origin and detachment. Taken together, the diversity of seismological images in the same area with often contrasting tectonic implications underscores the need for serious benchmarking of seismological models. Large arrays like AlpArray provide an excellent opportunity to conduct such comparative studies

Alpine Crust and Mantle Structure From 3D Monte Carlo Surface- and Body-Wave Tomography

An ongoing controversy revolves around the detailed structure of the subducting European and Adriatic plates under the Alps and the adjacent orogens. Mostly based on P‐wave travel time tomographic images, slab break‐off at different times, reversals of subduction polarity and segmentation of the slab into independent units have been proposed. These processes may have important geodynamic consequences such as rapid surface uplift, past magmatic events or changes in the style of continental collision. However, some of the tomographic results are contradictory, particularly evident in the uppermost mantle where teleseismic P waves traverse the medium almost vertically with few ray crossings and a stronger dependence on the crustal correction. In this work, we present the result of an innovative joint inversion approach using surface‐ and teleseismic body‐wave travel times to mitigate some of the shortcomings in both data types. Applying a reversible‐jump Markov chain Monte Carlo approach, we simultaneously constrain the vP and vS structure and their uncertainties in the crust and upper mantle. The results indicate a continuous slab structure from the crust‐mantle boundary down to at least 400 km depth under the western, central and eastern Alps. The results, however, also suggest that fitting the data within their respective measurement uncertainties may not be sufficient to reliably determine the presence of a shallow slab break‐off beneath the Alps

Centrality Dependence of Charged Particle Multiplicity in Au-Au Collisions at sqrt(s_NN)=130 GeV

We present results for the charged-particle multiplicity distribution at mid-rapidity in Au - Au collisions at sqrt(s_NN)=130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find $dN_{ch}/d\eta_{|\eta=0} = 622 \pm 1 (stat) \pm 41 (syst)$. The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.Comment: 307 authors, 43 institutions, 6 pages, 4 figures, 1 table Minor changes to figure labels and text to meet PRL requirements. One author added: M. Hibino of Waseda Universit

Centrality dependence of pi^[+/-], K^[+/-], p and p-bar production from sqrt(s_NN)=130 GeV Au + Au collisions at RHIC

Identified pi^[+/-] K^[+/-], p and p-bar transverse momentum spectra at mid-rapidity in sqrt(s_NN)=130 GeV Au-Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. The multiplicity densities scale faster than the number of participating nucleons. Kaon and nucleon yields per participant increase faster than the pion yields. In central collisions at high transverse momenta (p_T greater than 2 GeV/c), anti-proton and proton yields are comparable to the pion yields.Comment: 6 pages, 3 figures, 1 table, 307 authors, accepted by Phys. Rev. Lett. on 9 April 2002. This version has minor changes made in response to referee Comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Net Charge Fluctuations in Au + Au Interactions at sqrt(s_NN) = 130 GeV

Data from Au + Au interactions at sqrt(s_NN) = 130 GeV, obtained with the PHENIX detector at RHIC, are used to investigate local net charge fluctuations among particles produced near mid-rapidity. According to recent suggestions, such fluctuations may carry information from the Quark Gluon Plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays.Comment: 6 pages, RevTeX 3, 3 figures, 307 authors, submitted to Phys. Rev. Lett. on 21 March, 2002. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (will be made) publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm

Flow Measurements via Two-particle Azimuthal Correlations in Au + Au Collisions at sqrt(s_NN) = 130 GeV

Two particle azimuthal correlation functions are presented for charged hadrons produced in Au + Au collisions at RHIC sqrt(s_NN) = 130 GeV. The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values v_2 show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone, epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p_T. A breakdown of this epsilon scaling is observed for charged hadrons with p_T > 1.0 GeV/c for the most central collisions.Comment: 6 pages, RevTeX 3, 4 figures, 307 authors, submitted to Phys. Rev. Lett. on 11 April 2002. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (will be made) publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm

Measurement of the mid-rapidity transverse energy distribution from sNN=130\sqrt{s_{NN}}=130 GeV Au+Au collisions at RHIC

The first measurement of energy produced transverse to the beam direction at RHIC is presented. The mid-rapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that E_T / N_ch remains relatively constant as a function of centrality. The energy density calculated via Bjorken's prescription for the 2% most central Au+Au collisions at sqrt(s_NN)=130 GeV is at least epsilon_Bj = 4.6 GeV/fm^3 which is a factor of 1.6 larger than found at sqrt(s_NN)=17.2 GeV (Pb+Pb at CERN).Comment: 307 authors, 6 pages, 4 figures, 1 table, submitted to PRL 4/18/2001; revised version submitted to PRL 5/24/200

Event-by-event fluctuations in Mean pTp_T and Mean eTe_T in sqrt(s_NN) = 130 GeV Au+Au Collisions

Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at sqrt(s_NN) = 130 GeV at RHIC. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of non-statistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant non-random fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p_T or e_T spectra, we exclude a region of fluctuations in sqrt(s_NN) = 130 GeV Au+Au collisions.Comment: 10 pages, RevTeX 3, 7 figures, 4 tables, 307 authors, submitted to Phys. Rev. C on 22 March 2002. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (will be made) publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm