Facility For Antiproton And Ion Research Research Articles

Electromagnetic form factors of the transition from the spin-3/2 Σ to the Λ hyperon

The three electromagnetic form factors for the transition from a $3/{2}^{+}\phantom{\rule{4pt}{0ex}}{\mathrm{\ensuremath{\Sigma}}}^{*}$ hyperon to the ground-state $\mathrm{\ensuremath{\Lambda}}$ hyperon are studied. At low energies, combinations of the transition form factors can be deduced from Dalitz decays of the ${\mathrm{\ensuremath{\Sigma}}}^{*}$ hyperon to $\mathrm{\ensuremath{\Lambda}}$ plus an electron-positron pair. It is pointed out how more information can be obtained with the help of the self-analyzing weak decay of the $\mathrm{\ensuremath{\Lambda}}$. In particular, it is shown that these transition form factors are complex quantities already in this kinematical region. Such measurements are feasible at hyperon factories such as, for instance, the Facility for Antiproton and Ion Research (FAIR). At higher energies, the transition form factors can be measured in electron-positron collisions. The transition form factors are related to decay distributions and differential cross sections. Using dispersion theory, the low-energy electromagnetic form factors for the ${\mathrm{\ensuremath{\Sigma}}}^{*}$-to-$\mathrm{\ensuremath{\Lambda}}$ transition are related to the pion vector form factor. The additionally required input, i.e., the two-pion--${\mathrm{\ensuremath{\Sigma}}}^{*}$--$\mathrm{\ensuremath{\Lambda}}$ amplitudes, is determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory, including the baryons from the octet and the decuplet. A poorly known NLO parameter is fixed to the experimental value of the ${\mathrm{\ensuremath{\Sigma}}}^{*}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}\ensuremath{\gamma}$ decay width. Pion rescattering is taken into account by using dispersion theory and solving a Muskhelishvili-Omn\`es equation. Subtracted and unsubtracted dispersion relations are discussed. However, in view of the fact that the transition form factors are complex quantities, the current data situation does not allow for a full determination of the subtraction constants. To reduce the number of free parameters, unsubtracted dispersion relations are used to make predictions for the transition form factors in the low-energy space- and timelike regions.

Exploring Cosmic Matter in the Laboratory—The Compressed Baryonic Matter Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is one of four scientific pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. In collisions between heavy nuclei at FAIR energies, it is expected that the matter in the reaction zone is compressed to more than five times saturation density, corresponding to the density in the core of a massive neutron star. This offers the unique opportunity to study in the laboratory the high-density equation-of-state (EOS) of nuclear matter, and to search for new phases of Quantum Chromo Dynamics (QCD) matter at large baryon-chemical potentials. Promising experimental observables sensitive to the EOS and to possible phase transitions will be discussed, together with a brief description of the CBM experiment.

Centrality Dependence of Multiplicity Fluctuations in Ion-Ion Collisions from the Beam Energy Scan at FAIR

Multiplicity distributions and event-by-event multiplicity fluctuations in AuAu collisions at energies in future heavy-ion experiment at the Facility for Anti-proton and Ion Research (FAIR) are investigated. Events corresponding to FAIR energies are simulated in the frame work of Ultra Relativistic Quantum Molecular Dynamics (URQMD) model. It is observed that the mean and the width of multiplicity distributions monotonically increase with beam energy. The trend of variations of dispersion with mean number of participating nucleons for the centrality-bin width of 5% are in accord with the Central Limit Theorem. The multiplicity distributions in various centrality bins as well as for full event samples are observed to obey Koba, Nielsen and Olesen (KNO) scaling. The trends of variations of scaled variance with beam energy are also found to support the KNO scaling predictions for larger collision centrality. The findings also reveal that the statistical fluctuations in 5% centrality-bin width appear to be under control.

System size dependence of net-charge fluctuation in nucleus-nucleus collisions at FAIR energies

Dynamical net-charge fluctuations are studied in symmetric nuclear collisions of different system size and at two different collision energies that in the near future will be available at the Facility for Antiproton and Ion Research (FAIR). Multiparticle emission data simulated by the ultra-relativistic quantum molecular dynamics (UrQMD) are analyzed for this purpose. Our primary objective is to examine the system size dependence of dynamical fluctuation of conserved charge at typical FAIR conditions. The centrality, pseudorapidity interval size and azimuthal angle interval size dependence of the dynamical fluctuations are studied too. The effects of global charge conservation (GCC) and finite multiplicity bin width correction are taken into account. To a large extent the systematics followed by the dynamical fluctuations at FAIR conditions are found to be a lower energy extrapolation of the observations made in this regard in the Relativistic Heavy-ion Collider (RHIC) experiments.

The Silicon Tracking System of the CBM Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) aims to study the properties of nuclear matter at high net-baryon densities and moderate temperatures.The Silicon Tracking System (STS) is the key detector to reconstruct with a high efficiency up to 1000 charged particle trajectories created in heavy-ion collisions at interaction rates of up to 10 MHz. It will determine the momentum of the particles with a momentum resolution Δp/p ≈ 1-2% which requires ultra-low detector material budget of 0.3-1% X0 per layer. The detector comprise eight layers of double-sided silicon micro-strip sensors and will be placed inside the 1 Tm superconducting magnet which limits the space available, which in turn requires advanced cooling approaches and mechanical design with precise tracking layers alignment. The micro-strip sensors have to be radiation hard and checked for their quality optically and electrically before the assembly.This contribution gives an overview of the STS and presents the status of its component quality control and assembly procedures.

Charge stripping at high energy heavy ion Linacs

For each heavy-ion accelerator facility charge stripping is a key technology – the stripping charge state, its efficiency to produce ions in the selected charge state, and the beam quality after stripping substantially determine the entire accelerator performance. Modern heavy ion accelerator facilities such as the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, Germany provide for high-intensity heavy-ion beams beyond 200 MeV/u. Heavy ions generated in an ion source at comparatively low charge states are pre-accelerated in a Linac to a few MeV/u, after charge stripping the average charge state is increased and one (or several) ion charge states are selected for further acceleration. This enables more efficient acceleration up to the final beam energy, compared to acceleration of ions with a low charge state. C-foil stripping allows for highest mean charge state and best stripping efficiency into the desired charge state. Therefore minimum acceleration voltage could be expected utilizing C-foil stripping. Due to the high power deposited by the ions in the stripping media and radiation damages if solids are used, self-recovering stripper media must be used in any case. First layout scenarios for a 200 MeV/u heavy ion Linac considering efficient heavy ion stripping will be presented.

Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state

In this article, we examine the equation of state (EoS) dependence of the anisotropic flow parameters ($v_{1}$, $v_{2}$ and $v_{4}$) of charged and identified hadrons, as a function of transverse momentum ($p_{\rm T}$), rapidity ($y_{c.m.}$) and the incident beam energy ($\rm E_{\rm Lab}$) in mid-central Au + Au collisions in the energy range $\rm E_{\rm Lab} = 6 -25$ A GeV. Simulations are carried out by employing different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode. In the hybrid mode, transport calculations are coupled with the ideal hydrodynamical evolution. Within the hydrodynamic scenario, two different equations of state (EoS) viz. Hadron gas and Chiral + deconfinement EoS have been employed separately to possibly mimic the hadronic and partonic scenarios, respectively. It is observed that the flow parameters are sensitive to the onset of hydrodynamic expansion of the fireball in comparison to the pure transport approach. The results would be useful as predictions for the upcoming low energy experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

A timing RPC with low resistive ceramic electrodes

For precise start time determination a Beam Fragmentation T0 Counter (BFTC) is under development for the Time-of-Flight Wall of the Compressed Baryonic Matter Spectrometer (CBM) at the Facility for Antiproton and Ion Research (FAIR) at Darmstadt/Germany. This detector will be located around the beam pipe, covering the front area of the Projectile Spectator Detector. The fluxes at this region are expected to exceed 105cm−2s−1. Resistive plate chambers (RPC) with ceramic composite electrodes could be use because of their high rate capabilities and radiation hardness of material. Efficiency ≥ 97 %, time resolution ≤ 90 ps and rate capability ≥ 105cm−2s−1 were confirmed during many tests with high beam fluxes of relativistic electrons. We confirm the stability of these characteristics with low resistive Si3N4/SiC floating electrodes for a prototype of eight small RPCs, where each of them contains six gas gaps. The active RPC size amounts 20×20 mm2 produced on basis of Al3O2 and Si3N4/SiC ceramics. Recent test results obtained with relativistic electrons at the linear accelerator ELBE of the Helmholtz-Zentrum Dresden-Rossendorf with new PADI-10 Front-end electronic will be presented.

Beam test of CBM-TOF MRPC prototype

The Compressed Baryonic Matter spectrometer (CBM) is expected to be operational in the year 2024 at the Facility for Anti-proton and Ion Research (FAIR) in Darmstadt, Germany. CBM aims to study strongly interacting matter under extreme conditions. The key element providing hadron identification is the Time-Of-Flight (TOF) wall at incident energies between 2 and 10 AGeV . The TOF-wall covers the polar angular range from 2.5̂–25̂ and full azimuth. According to the simulation results, the TOF system is required to reach a time resolution of better than 80 ps for the particle identification (PID) under high rate. The existing conceptual design foresees a 120 m2 TOF-wall composed of Multi-gap Resistive Plate Chambers (MRPC) which is subdivided into a high rate region, a middle rate region and a low rate region. The flux in the low rate region is around 1 kHz/cm2. For this region, we developed a Multistrip-MRPC using thin float glass as the resistive electrode. In this paper, we present the design of these MRPC prototypes and the results obtained during the beam test at the E3 line at Beijing Electron-Positron Collider (BEPC).

The CBM Time-of-Flight system

The Compressed Baryonic Matter spectrometer (CBM) is a future fixed-target heavy-ion experiment located at the Facility for Anti-proton and Ion Research (FAIR) in Darmstadt, Germany. The key element in CBM providing hadron identification at incident beam energies between 2 and 11 AGeV (for Au-nuclei) will be a 120 m2 large Time-of-Flight (ToF) wall composed of Multi-gap Resistive Plate Chambers (MRPC) with a time resolution of the system better than 80 ps. Aiming for an interaction rate of 10 MHz for Au+Au collisions the MRPCs have to cope with an incident particle flux between 0.1 kHz/cm2 and 100 kHz/cm2 depending on their location. Being the system characterized by wide ranges of both granularity and rate capability, the conceptual design of the ToF-wall foresees 6 different granularities and 4 different detector designs. In order to elaborate the final MRPC design of these counters several heavy-ion in-beam and cosmic-ray tests were performed. In this contribution we present the conceptual design of the TOF wall and discuss the performance results of full-size MRPC prototypes.

Study on cosmic test and QC method of high-rate MRPC for CBM-TOF

The CBM (Compressed Baryonic Matter) experiment constructed at FAIR (Facility for Anti-proton and Ion Research) at GSI, Darmstadt, Germany, will provide unique research opportunities to explore the phase diagram of nuclear matter. As one of the core detectors in the CBM experiment, the Time-of-Flight (TOF) system applies the MRPC (Multi-gap Resistive Plate Chamber) for a precise particle identification for all the incident charged hadrons. The CBM-TOF will be operated at an ion beam intensity up to 109/s, which means the particle fluxes on the TOF wall can reach an unprecedentedly high rate of 30 kHz/cm2. Almost half of the MRPC counters are from the inner region of the TOF wall, and they will be assembled with the low-resistive glass which enables them to work under such high rate. This is the first time of the large scale application of the low-resistive glass MRPCs into the nuclear and high-energy physics experiments. It is especially important to study on the production and test procedure to keep the good performance of all these counters. For this mass production, we have developed a set of specified manufacturing procedure and quality control method to guarantee the performance of all the counters. A newly developed method to check the uniformity of the gas gap with help of the projection imaging technique has been first applied. Until now, 73 MRPCs have been produced for the eTOF project in the BESII detector upgrade at STAR and the TOF system of mini-CBM. Tested by cosmic ray in a system based on TRB, all the produced counters show a stable performance of above 95% efficiency and below 90 ps time resolution. The study on the mass production of the low-resistive plate chamber will provide experience for wide application of MRPC into the high rate experiments in the future. In this paper, the counter design, manufacturing procedures, quality control methods and test results for this MRPC counter are described in a detailed way.

Final Design of the Superferric Branched Dipoles for the FAIR Super-FRS

The superconducting fragment separator (Super-FRS) of facility for antiproton and ion research (FAIR) located in Darmstadt, Germany, requires three branched superferric dipoles which are more complex than the 21 standard dipoles already designed by Commissariat l’Energie Atomique et aux nergies alternatives (CEA). The 50-ton branched dipoles allow the beam of particles to be directed towards the different branches of the separator. The final design proposed by CEA Paris-Saclay for these dipoles integrates features required for the installation of the Y-shaped vacuum chamber which have an impact on the magnetic and mechanical design of the magnet. The coil casing design was modified and the cold-to-warm supports had to be reorganized to contain the Laplace forces acting on the weakened mechanical structure. Cryogenic experiments have been conducted to characterize the behavior of the active thermosiphon concept and to validate the cryogenic design proposed last year. We present in this paper the final design for the FAIR Super-FRS branched dipole magnets along with the design simulation results (magnetic, cryogenic, and mechanical analyses) and the main results of the active thermosiphon tests conducted recently.

Simulation study of the reaction with PANDA at FAIR

The PANDA experiment will be one of the pillars of the new Facility for Antiproton and Ion Research (FAIR), which is currently under construction in Darmstadt, Germany. PANDA will be a fixed-target experiment which will allow the study of non-perturbative phenomena of the strong interaction. These will be probed in antiproton-proton collisions in the momentum range of 1.5 - 15 GeV/c. Within the PANDA physics program, strangeness production will be addressed through processes. Measurements of the channel for its comparison with the existing data of the channel are highly encouraged to study the role of isospin symmetry in hadron production dynamics. This work consists on a simulation study focusing on the feasibility of measuring the channel at PANDA.

Opportunities for measurements of astrophysical‐relevant alpha‐capture reaction rates at CRYRING@ESR

The heavy‐ion storage ring CRYRING@ESR has recently been installed and commissioned at GSI as one of the first installations of the upcoming Facility for Antiproton and Ion Research (FAIR). It is designed to store highly charged ions in the energy range between 300 keV/u and about 10 MeV/u. It will incorporate a gas‐jet target providing high‐density jets of, among other gases, hydrogen and helium. This will allow to study alpha‐capture reaction rates of astrophysical interest in the energy range of the Gamow window for core‐collapse supernovae. Special interest comes from the long‐lived radio‐isotope 44Ti (t1/2 = 58.9 years), which is supposed to be produced in the alpha‐rich freeze‐out during such an event. The nucleosynthesis of this isotope is of great interest, as the amount of material produced can be estimated by direct observation in remnants of recent supernovae. The disagreements between the observations and the estimations from astrophysical models show the need of more experimental data for the production and consumption reactions in the energy range of a core‐collapse supernova. In this article, we will describe the proposed method of injecting beams of 44Ti into CRYRING@ESR and performing the actual reaction rate measurements.

A magnetic spectrometer for electron‐positron pair spectroscopy in storage rings

We report an analysis of electron‐optical properties of a toroidal magnetic sector spectrometer and examine parameters for its implementation in a relativistic heavy‐ion storage ring, for example the High Energy Storage ring (HESR) at the future Facility for Antiproton and Ion Research (FAIR) facility. For studies of free–free pair production in heavy‐ion atom collisions, this spectrometer exhibits very high efficiencies for coincident e+–e− pair spectroscopy over a wide range of momenta of emitted lepton pairs. The high coincidence efficiency of the spectrometer is the key for stringent tests of theoretical predictions for the phase space correlation of lepton vector momenta in free–free pair production.

MRPC3b mass production for CBM-TOF and eTOF at STAR

The Compressed Baryonic Matter (CBM) spectrometer aims to study strongly interacting matter under extreme conditions. The key element providing hadron identification at incident energies between 2 and 11AGeV in heavy-ion collisions at the SIS100 accelerator is a Time-of-Flight (TOF) wall covering the polar angular range from 2.5̂–25̂ and full azimuth. CBM is expected to be operational in the year 2024 at the Facility for Anti-proton and Ion Research (FAIR) in Darmstadt, Germany. The existing conceptual design foresees a 120 m2 TOF-wall composed of Multi-gap Resistive Plate Chambers (MRPC) which is subdivided into a high rate region, a middle rate region and a low rate region. The MRPC3b Multistrip-MRPCs, foreseen to be integrated in the low rate region, have to cope with charged particle fluxes up to 1 kHz/cm2 and therefore will be constructed with thin float glass (0.28 mm thickness) as resistive electrode material. In the scope of the FAIR phase 0 program it is planned to install about 36% of the MRPC3b counters in the east endcap region of the STAR experiment at BNL as an upgrade for the Beam Energy Scan campaign (BESII) in 2019/2020.

MRPC3b for CBM-TOF

The Compressed Baryonic Matter (CBM) experiment will be one of the major scientific pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. The Multigap Resistive Plate Chamber (MRPC) has been adopted for the construction of the Time of Flight (TOF) Wall; a system time resolution of 80ps is necessary for hadron identification. MRPC3b, as defined in the CBM TOF TDR, has been designed for the outer region of the TOF system. The MRPC3b is a two-stack, 10 gas gaps with 32 strips read out at both ends. The thin floating glass will be used as the electrodes. In this paper, the design details will be discussed. The mass production has already during the spring of 2017. The assembly procedures and QA (Quality Assurance) & QC (Quality Control) methods will also be presented. The performance achieved from the cosmic ray test shows that the efficiency is better than 91% and the resolution is about 80ps with 95% Freon and 5% iso-butane gas mixture.

Investigations of High Throughput Computing for Event Selection Process of MuCh@CBM

There is a requirement of High Throughput Computation (HTC) for the large scale experiment Compressed Baryonic Matter (CBM) experiment which is carried out at Facility for Antiproton and Ion Research (FAIR) centre at GSI Darmstadt, Germany. CBM is a dedicated relativistic heavy ion collision experiment. In this experiment, highly energized ions will be collided with a fixed target resulting production of a rare particle J/Ψ named charmonia which will pass through different detectors of the experiment. One such detector is Muon Chamber (MuCh) Detector System to measure key observables including the measurement of J/Ψ which can be measured via their decay into the di-muon (µ+ and µ-) channel. However the production of charmonium is extremely small therefore experiment is instrumented such that per second total 107 events, one collision is known as one event, will be gathered to have good statistics. To select probable candidate of J/Ψ, an algorithm has been developed. To process the algorithm in optimal way use of heterogeneous platforms consisting of various types of processors are under study. In this work Intel, AMD CPUs and Intel Xeon-Phi co-processors are used with Open MP and P Thread parallel processing methodologies for the mentioned event selection process. The results of using different processors with different methodologies will be presented in this article. It is found that problem scales with the number of threads and optimal at the maximum number of hardware thread (without hyper-threading).

Study and test of an active thermosiphon experimental set-up to validate Super-FRS dipoles cooling system

In the framework of the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, CEA is in charge of the design studies for superferric dipole magnets of the Superconducting Fragment Separator (Super-FRS). Each of these dipoles has 2 coils with a trapezoidal shape, each coil being cooled by a horizontal 20 × 10 mm2 liquid helium channel (below or above the coil). The static heat load to extract is 5 W and, to generate a mass flow, the principle of a thermosiphon is implemented with a heater on the return pipe to force the flow direction of the thermosiphon. To validate this cooling system, an experimental set-up was designed and built at CEA Paris-Saclay. This paper presents the experimental set-up and the results of the tests. The effect of the horizontal heat load and the influence of the heater are reported.

Technical design report for the Barrel DIRC detector**The use of registered names, trademarks, etc in this publication does not imply, even in the absence of specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use.

The (anti-Proton ANnihiliation at DArmstadt) experiment will be one of the four flagship experiments at the new international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. will address fundamental questions of hadron physics and quantum chromodynamics using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c and a design luminosity of up to 2 × 1032 cm−2 s−1. Excellent particle identification (PID) is crucial to the success of the physics program. Hadronic PID in the barrel region of the target spectrometer will be performed by a fast and compact Cherenkov counter using the detection of internally reflected Cherenkov light (DIRC) technology. It is designed to cover the polar angle range from 22° to 140° and will provide at least 3 standard deviations (s.d.) π/K separation up to 3.5 GeV/c, matching the expected upper limit of the final state kaon momentum distribution from simulation. This documents describes the technical design and the expected performance of the Barrel DIRC detector. The design is based on the successful BaBar DIRC with several key improvements. The performance and system cost were optimized in detailed detector simulations and validated with full system prototypes using particle beams at GSI and CERN. The final design meets or exceeds the PID goal of clean π/K separation with at least 3 s.d. over the entire phase space of charged kaons in the Barrel DIRC.