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The STAR experiment provides a perfect machinery for studying strange matter for more than two decades. Recently, we developed the express procedure, which allows online monitoring of the collected physics data. The high quality of express calibration and reconstruction provides a unique possibility to run the express production and observe almost in real time strange particles including mesons, hyperons, resonances and even hypernuclei.
The STAR Beam Energy Scan II program, including fixed target Au+Au collisions taken in 2018–2021, is particularly suited to study hypernuclei. Light hypernuclei are expected to be abundantly produced in low energy heavy-ion collisions. Measurements of hypernuclei production and their properties will provide information on the hyperon-nucleon interactions, which are essential ingredients for understanding nuclear matter equation of state at high net-baryon densities, such as inside neutron stars.
With the heavy fragment trigger introduced for the 2021 data taking, we were able to run the express production at the STAR High Level Trigger farm. The collected data were suffcient to observe the decay process of Λ5He →4Hepπ− with more than 11σ significance, measure binding energy as a function of hypernuclei mass, and study hypernuclei decay properties with the Dalitz plot technique.
The multiplicity fluctuations in A+A collisions at SPS and RHIC energies are studied within the HSD transport approach. We find a dominant role of the fluctuations in the nucleon participant number for the final fluctuations. In order to extract physical fluctuations one should decrease the fluctuations in the participants number. This can be done considering very central collisions. The system size dependence of the multiplicity fluctuations in central A+A collisions at the SPS energy range – obtained in the HSD and UrQMD transport models – is presented. The results can be used as a ‘background’ for experimental measurements of fluctuations as a signal of the critical point. Event-by-event fluctuations of the K/p , K/p and p/p ratios in A+A collisions are also studied. Event-by-event fluctuations of the kaon to pion number ratio in nucleus-nucleus collisions are studied for SPS and RHIC energies. We find that the HSD model can qualitatively reproduce the measured excitation function for the K/p ratio fluctuations in central Au+Au (or Pb+Pb) collisions from low SPS up to top RHIC energies. The forward-backward correlation coefficient measured by the STAR Collaboration in Au+Au collisions at RHIC is also studied. We discuss the effects of initial collision geometry and centrality bin definition on correlations in nucleus-nucleus collisions. We argue that a study of the dependence of correlations on the centrality bin definition as well as the bin size may distinguish between these ‘trivial’ correlations and correlations arising from ‘new physics’. 5th International Workshop on Critical Point and Onset of Deconfinement - CPOD 2009, June 08 - 12 2009 Brookhaven National Laboratory, Long Island, New York, USA
In the strong coupling and heavy quark mass regime, lattice QCD dimensionally reduces to effective theories of Polyakov loops depending on the parameters of the original Wilson action β,κ and Nτ. We apply coarse graining techniques to such theories in 1d and 2d, corresponding to lattice QCD at finite temperature and non-zero chemical potential in 1+1d and 2+1d, respectively. In 1d the method is applied to the effective theories up to O(κ4). Using the transfer matrix, the recursion relations are solved analytically. The thermodynamic limit is taken for some observables. Afterwards, continuum extrapolation is performed numerically and results are discussed. In 2d the coarse graining method is applied in the pure gauge and static quark limit. Running couplings are obtained and the fixed points of the transformations are discussed. Finally, the critical coupling of the deconfinement transition is determined in both limits. Agreement to about 12% with Monte Carlo results of 2+1d Yang-Mills theory from the literature is observed.
For the exploration of the phase diagram of QCD, effective Polyakov loop theories derived from lattice QCD provide a valuable tool in the heavy quark mass regime. In practice, the evaluation of these theories is complicated by the appearance of long-range and multipoint interaction terms. On the other hand, it is well known that for theories with such kind of interactions mean field approximations can be expected to yield reliable results. Here, we apply this framework to the critical endpoint of the deconfinement transition and results are compared to the literature. This treatment can also be used to investigate the phase diagram at non-zero baryon and isospin chemical potential.
Usually 4-ROD Radio Frequency Quadrupoles (RFQ) are built for frequencies up to 216 MHz. For higher frequencies 4-VANE structures are more common. The advantages of 4-Rod structures, the greater flexibility for tuning and being more comfortable for maintenance, are motivating the development of a 4-Rod RFQ for higher frequencies than 216 MHz. In particular a 325 MHz RFQ with an output energy of 3 MeV is needed for the proton linac for the FAIR project of GSI. This paper reports about the design studies and the latest developments of this RFQ.
We present the results of two-pion production in tagged quasi-free np collisions at a deutron incident beam energy of 1.25 GeV/c measured with the High-Acceptance Di-Electron Spectrometer (HADES) installed at GSI. The specific acceptance of HADES allowed for the first time to obtain high-precision data on π+π− and π−π0 production in np collisions in a region corresponding to large transverse momenta of the secondary particles. The obtained differential cross section data provide strong constraints on the production mechanisms and on the various baryon resonance contributions (∆∆, N(1440), N(1520), ∆(1600)). The invariant mass and angular distributions from the np → npπ+π −and np → ppπ−π0 reactions are compared with different theoretical model predictions.
To reach high luminosities in future linear colliders short range wakes havea to be controlled in the range of X-band frequencies or higher. Rectangular irises can be used to introduce strong focusing quadrupole-like rf-fields. Even circular irises in iris-loaded accelarator structures have the capability of focusing if the particle velocity differs from phase velocity. Theoretical investigations concerning the focusing strength to be expected are presented. Their applicability for linear colliders is discussed.
Differential invariant cross sections of light neutral mesons in p-Pb collisions at √sNN = 8.16 TeV and in pp collisions at √s = 8 TeV have been measured up to very high transverse momentum (pT). By combining independent reconstruction techniques available in ALICE using the EMCal and PHOS calorimeters as well as the central barrel tracking detectors, the combined spectra cover almost two orders of magnitude in pT for the π0 meson. The nuclear modification factor RpPb has been measured for the π0 and η mesons and is found to be consistent with NLO pQCD, CGC and energy loss calculations. Comparisons to the RpPb of π0 measured in √sNN = 5.02 TeV hint at a stronger suppression at low pT with increasing collision energy.
High perveance negative ion beams with low emittance are essential for several next generation particle accelerators (i. g. spallation sources like ESS [1] and SNS [2]). The extraction and transport of these beams have intrinsic difficulties different from positive ion beams. Limitation of beam current and emittance growth have to be avoided. To fulfill the requirements of those projects a detailed knowledge of the physics of beam formation the interaction of the H- with the residual gas and transport is substantial. A compact cesium free H- volume source delivering a low energy high perveance beam (6.5 keV, 2.3 mA, perveance K= 0.0034) has been built to study the fundamental physics of beam transport and will be integrated into the existing LEBT section in the near future. First measurements of the interaction between the ion beam and the residual gas will be presented together with the experimental set up and preliminary results.
The QGP that might be created in ultrarelativistic heavy-ion collisions is expected to radiate thermal dilepton radiation. However, this thermal dilepton radiation interferes with dileptons originating from hadron decays. In the invariant mass region between the f and J=y peak (1GeV <= M l+l <=. 3GeV) the most substantial background of hadron decays originates from correlated DD¯ -meson decays. We evaluate this background using a Langevin simulation for charm quarks. As background medium we utilize the well-tested UrQMD-hybrid model. The required drag and diffusion coefficients are taken from a resonance approach. The decoupling of the charm quarks from the hot medium is performed at a temperature of 130MeV and as hadronization mechanism a coalescence approach is chosen. This model for charm quark interactions with the medium has already been successfully applied to the study of the medium modification and the elliptic flow at FAIR, RHIC and LHC energies. In this proceeding we present our results for the dilepton radiation from correlated D¯D decays at RHIC energy in comparison to PHENIX measurements in the invariant mass range between 1 and 3 GeV using different interaction scenarios. These results can be utilized to estimate the thermal QGP radiation.
Euclidean strong coupling expansion of the partition function is applied to lattice Yang-Mills theory
at finite temperature, i.e. for lattices with a compactified temporal direction. The expansions
have a finite radius of convergence and thus are valid only for b <bc, where bc denotes the nearest
singularity of the free energy on the real axis. The accessible temperature range is thus the
confined regime up to the deconfinement transition. We have calculated the first few orders of
these expansions of the free energy density as well as the screening masses for the gauge groups
SU(2) and SU(3). The resulting free energy series can be summed up and corresponds to a glueball
gas of the lowest mass glueballs up to the calculated order. Our result can be used to fix
the lower integration constant for Monte Carlo calculations of the thermodynamic pressure via
the integral method, and shows from first principles that in the confined phase this constant is
indeed exponentially small. Similarly, our results also explain the weak temperature dependence
of glueball screening masses below Tc, as observed in Monte Carlo simulations. Possibilities and
difficulties in extracting bc from the series are discussed.
We show examples of the impact of the Maxwellian averaged capture cross sections determined at n_TOF over the past 20 years on AGB stellar nucleosynthesis models. In particular, we developed an automated procedure to derive MACSs from evaluated data libraries, which are subsequently used as input to stellar models computed by means of the FuNS code. In this contribution, we present a number of s-process abundances obtained using different data libraries as input to stellar models, with a focus on the role of n_TOF data.
Exotic nuclear matter
(2016)
Recent developments of nuclear structure theory for exotic nuclei are addressed. The inclusion of hyperons and nucleon resonances is discussed. Nuclear multipole response functions, hyperon interactions in infinite matter and in neutron stars and theoretical aspects of excitations of nucleon resonances in nuclei are discussed.
Am 27. und 28. September 2005 tagten Historiker und Philosophen der Mathematik und Naturwissenschaften in Frankfurt a.M. im Gebäude des Physikalischen Vereins. Eine Besonderheit des Internationalen Symposiums war der Dialog mit Vertretern der aktuellen Grundlagendebatte der Basiswissenschaft Physik. In zwölf Vorträgen wurden an zwei Tagen Raum- und Zeitkonzeptionen bedeutender Naturphilosophen der letzten 400 Jahre vorgestellt. Naturwissenschaftshistoriker rekonstruierten die Entwürfe von Giordano Bruno, Marin Mersenne, René Descartes, Otto von Guericke, Baruch Spinoza, Gottfried Wilhelm Leibniz, Isaac Newton und Leonhard Euler, während Grundlagentheoretiker der Physik einen Überblick über eigene Konzeptionen mit einem systematischen Anschluss an die Denktraditionen vorführten. Die Tagung wurde von der Fritz Thyssen Stiftung gefördert sowie vom Förderverein des Frankfurter Institutes für Geschichte der Naturwissenschaften "Arbor Scientiarum" und dem Physikalischen Verein finanziell unterstützt. ...
We investigate the properties of the QCD matter across the deconfinement phase transition. In the scope of the parton-hadron string dynamics (PHSD) transport approach, we study the strongly interacting matter in equilibrium as well as the out-of equilibrium dynamics of relativistic heavy-ion collisions. We present here in particular the results on the electromagnetic radiation, i.e. photon and dilepton production, in relativistic heavy-ion collisions and the relevant correlator in equilibrium, i.e. the electric conductivity. By comparing our calculations for the heavy-ion collisions to the available data, we determine the relative importance of the various production sources and address the possible origin of the observed strong elliptic flow ν2 of direct photons.
Gravitational-wave cosmology with dark sirens: state of the art and perspectives for 3G detectors
(2022)
A joint fit of the mass and redshift distributions of the population of Binary Black Holes detected with Gravitational-Wave observations can be used to obtain constraints on the Hubble parameter and on deviations from General Relativity in the propagation of Gravitational Waves. We first present applications of this technique to the latest catalog of Gravitational-Wave events, focusing on the comparison of different parametrizations for the source-frame mass distribution of Black Hole Binaries. We find that models with more than one feature are favourite by the data, as suggested by population studies, even when varying the cosmology. Then, we discuss perspectives for the use of this technique with third generation Gravitational-Wave detectors, exploiting the recently developed Fisher information matrix Python code GWFAST.
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the chemical equilibration of the system as a function of center of mass energy and of the parameters of the source. Additionally, we have tested and compared different versions of the statistical model, with special emphasis on possible explanations of the observed strangeness hadronic phase space under-saturation.
We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n_TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process.