Hadron Physics Experiments Research Articles

KinFit: A Kinematic Fitting Package for Hadron Physics Experiments

A kinematic fitting package, KinFit, based on the Lagrange multiplier technique has been implemented for generic hadron physics experiments. It is particularly suitable for experiments where the interaction point is unknown, such as experiments with extended target volumes. The KinFit package includes vertex finding tools and fitting with kinematic constraints, such as mass hypothesis and four-momentum conservation, as well as combinations of these constraints. The new package is distributed as an open source software via GitHub. This paper presents a comprehensive description of the KinFit package and its features, as well as a benchmark study using Monte Carlo simulations of the pprightarrow pK^+Lambda rightarrow pK^+ppi ^- reaction. The results show that KinFit improves the parameter resolution and provides an excellent basis for event selection.

From cosmic matter to the laboratory

AbstractThe recent discovery of binary neutron star mergers has opened a new and exciting venue of research into hot and dense strongly interacting matter. For the first time, this elusive state of matter, described by the theory of quantum chromo dynamics, can be studied in two very different environments. On the macroscopic scale, in the collisions of neutron stars; and on the microscopic scale, in collisions of heavy ions at particle collider facilities. We will discuss the conditions that are created in these mergers and the corresponding high energy nuclear collisions. This includes the properties of quantum chromo dynamics matter, that is, the expected equation of state as well as expected chemical and thermodynamic properties of this exotic matter. To explore this matter in the laboratory, a new research prospect is available at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. The worldwide unique accelerator and experimental facilities of FAIR will open the way for a broad spectrum of unprecedented research supplying a variety of experiments in hadron, nuclear, atomic, and plasma physics as well as biomedical and material science, which will be briefly described.

Spin-Zero Polarimetry for Linearly Polarised Photons at MAMI

Background: The tagged Coherent Bremsstrahlung technique is used to provide beams of linearly polarised photons at several of the world’s leading photonuclear facilities, including MAMI in Mainz, ELSA at Bonn, and GlueX at Jefferson Laboratory. The degree of linear polarisation in real photon experiments has direct impact on measurements of polarisation observables. Measurement of the linear polarisation is often the biggest source of systematic error in these experiments. Continuous, in-beam measurement will also allow the beam position to be adjusted to optimise the polarisation. Purpose: To determine whether it is possible to make an improved measurement of the degree of linear polarisation using a polarimeter based on a 12C target. Methods: Coherent π0 meson production from a spin-zero nucleus has a photon asymmetry of 1 and hence provides a direct method of measuring the beam polarisation. Results: Current methods of measurement are being employed as a comparison. Simulated statistics of π0 mesons produced off the polarimeter suggest the measurement is viable. Early results from production data support the viability of live, event-by-event measurements of the polarisation using this method. Conclusions: A spin-zero nucleus such as carbon will be developed as a polarimeter for measuring the degree of linear polarisation in hadron physics experiments with tagged photons of up to 1557 MeV.

Development of a time projection chamber for J-PARC hadron physics program

A time projection chamber (HypTPC) has been newly developed for the various hadron physics experiments at J-PARC. The design of HypTPC was carefully considered to cope with the J-PARC high intensity beam. The triple-layered GEM has been adopted as a signal amplification and the gating grid plane for an ion backflow suppression. The octagonal drift volume is defined by the cathode plane and the field cage structure with the height of 55 cm. A target is located inside the drift volume in order to have a large acceptance. The GET (General Electronic System for TPCs) is utilized for the data acquisition. The HypTPC was first commissioned with 230 MeV proton beam at HIMAC. The obtained position resolution is 400–700 µm, which gives the expected resolution of 230–300 µm under a magnetic field of 1 T. We have confirmed the high rate capability of the TPC up to 1 MHz with a good suppression of the ion backflow under the gate operation.

Parallel Algorithms for Online Track Finding for the ANDA Experiment at FAIR

ANDA is a future hadron and nuclear physics experiment at the FAIR facility in construction in Darmstadt, Germany. Unlike the majority of current experiments, ANDA’s strategy for data acquisition is based on online event reconstruction from free-streaming data, performed in real time entirely by software algorithms using global detector information. This paper reports on the status of the development of algorithms for the reconstruction of charged particle tracks, targeted towards online data processing applications, designed for execution on data-parallel processors such as GPUs (Graphic Processing Units). Two parallel algorithms for track finding, derived from the Circle Hough algorithm, are being developed to extend the parallelism to all stages of the algorithm. The concepts of the algorithms are described, along with preliminary results and considerations about their implementations and performance.

Experimental program of the Super-FRS Collaboration at FAIR and developments of related instrumentation

The physics program at the super-conducting fragment separator (Super-FRS) at FAIR, being operated in a multiple-stage, high-resolution spectrometer mode, is discussed. The Super-FRS will produce, separate and transport radioactive beams at high energies up to 1.5 AGeV, and it can be also used as a stand-alone experimental device together with ancillary detectors. Various combinations of the magnetic sections of the Super-FRS can be operated in dispersive, achromatic or dispersion-matched spectrometer ion-optical modes, which allow measurements of momentum distributions of secondary-reaction products with high resolution and precision. A number of unique experiments in atomic, nuclear and hadron physics are suggested with the Super-FRS as a stand-alone device, in particular searches for new isotopes, studies of hypernuclei, delta-resonances in exotic nuclei and spectroscopy of atoms characterized by bound mesons. Rare decay modes like multiple-proton or neutron emission and the nuclear tensor force observed in high-momentum regime can be also addressed. The in-flight radioactivity measurements as well as fusion, transfer and deep-inelastic reaction mechanisms with the slowed-down and energy-bunched fragment beams are proposed for the high-resolution and energy buncher modes at the Super-FRS.

Search for Pentaquark ${\mit \Theta }^{+}$ in Hadronic Reaction at J-PARC

A variety of nuclear and hadron physics experiments are being performed using meson beams at the J-PARC Hadron Facility. As the first experiment at the facility, the pentaquark Theta+ was searched for in the pi- p -> K- X reaction with a missing-mass resolution of 2 MeV (FWHM). The number of accumulated beam pions are 7.8x10^10 and 8.1x10^10 for different beam momenta of 1.92 and 2.01 GeV/c, respectively. No significant structure was observed in the missing mass spectra. Upper limits of the production cross section are obtained to be 0.28ub/sr in the laboratory frame at 90% confidence level for each beam momenta. With a help of theoretical models, an upper limit of the total decay width of Theta+ was estimated to be 0.36 and 1.9 MeV for J^P = 1/2+ and 1/2- states, respectively.

Online Tracking Algorithms on GPUs for the P̅ANDA Experiment at FAIR

P̅ANDA is a future hadron and nuclear physics experiment at the FAIR facility in construction in Darmstadt, Germany. In contrast to the majority of current experiments, PANDA's strategy for data acquisition is based on event reconstruction from free-streaming data, performed in real time entirely by software algorithms using global detector information. This paper reports the status of the development of algorithms for the reconstruction of charged particle tracks, optimized online data processing applications, using General-Purpose Graphic Processing Units (GPU). Two algorithms for trackfinding, the Triplet Finder and the Circle Hough, are described, and details of their GPU implementations are highlighted. Average track reconstruction times of less than 100 ns are obtained running the Triplet Finder on state-of- the-art GPU cards. In addition, a proof-of-concept system for the dispatch of data to tracking algorithms using Message Queues is presented.

FAIR - Cosmic Matter in the Laboratory

To explore cosmic matter in the laboratory - this fascinating research prospect becomes available at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed within the next five years adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. This includes new insights into the dynamics of supernovae depending on the properties of short-lived neutron-rich nuclei which will be investigated with intense rare isotope beams. New insights will be provided into the interior of stars by exploring dense plasmas with intense heavy-ion beams combined with a high-performance laser - or into neutron star cores by probing the highest baryon densities in relativistic nucleus-nucleus collisions at unprecedented collision rates. To the latter, the properties of hadrons play an important part which will be systematically studied by high precision hadron spectroscopy with antiproton beams at unmatched intensities. The worldwide unique accelerator and experimental facilities of FAIR will open the way for a broad spectrum of unprecedented fore-front research supplying a large variety of experiments in hadron, nuclear, atomic and plasma physics as well as biomedical and material science which will be briefly described in this article. This article is based on the FAIR Green Paper [4] and gives an update of former publications [5] - [12].

Triplet Finder: On the way to triggerless online reconstruction with GPUs for the [formula omitted] experiment

P¯ANDA is a state-of-the-art hadron physics experiment currently under construction at FAIR, Darmstadt. In order to select events for offline analysis, P¯ANDA will use a software-based triggerless online reconstruction, performed with a data rate of 200GB/s.To process the raw data rate of the detector in realtime, we design and implement a GPU version of the Triplet Finder, a fast and robust first-stage tracking algorithm able to reconstruct tracks with good quality, specially designed for the Straw Tube Tracker sub-detector of P¯ANDA. We reduce the algorithmic complexity of processing many hits together by splitting them into bunches, which can be processed independently. We evaluate different ways of processing bunches, GPU dynamic parallelism being one of them. We also propose an optimized technique for associating hits with reconstructed track candidates.The evaluation of our GPU implementation demonstrates that the Triplet Finder can process more than 8Mhits/s on a single K20X GPU, making it a promising algorithm for the online event filtering scheme of P¯ANDA.

FAIR – Cosmic matter in the laboratory

AbstractTo explore cosmic matter in the laboratory – this fascinating research prospect becomes available in 2018 at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed within the next five years adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. This includes new insights into the dynamics of supernovae depending on the properties of short‐lived neutron‐rich nuclei which will be investigated with intense rare isotope beams. New insights will be provided into the interior of stars by exploring dense plasmas with intense heavy‐ion beams combined with a high‐performance laser – or into neutron star cores by probing the highest baryon densities in relativistic nucleusnucleus collisions at unprecedented collision rates. To the latter, the properties of hadrons play an important part which will be systematically studied by high precision hadron spectroscopy with antiproton beams at unmatched intensities. The worldwide unique accelerator and experimental facilities of FAIR will open the way for a broad spectrum of unprecedented fore‐front research supplying a large variety of experiments in hadron, nuclear, atomic and plasma physics as well as biomedical and material science which will be briefly described in this article. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A pellet tracking system for the PANDA experiment

Frozen microspheres of hydrogen (pellets) will be one of the target types for the future hadron physics experiment PANDA at FAIR (GSI, Darmstadt, Germany) [1]. Pellets with a diameter of 25– μm are generated about 3 meters above the interaction region, to which they travel with a velocity around 80 m/s inside a narrow pipe. The interaction region is defined by the overlap of the pellet stream and the accelerator beam and has a size of a few millimeters. One would like to know the interaction point more precisely, to have better possibilities to reconstruct particle tracks and events e.g. in charmonium decay studies. One would also like to suppress background events that do not originate in a pellet, but e.g. may occur in rest gas, that is present in the beam pipe. A solution is provided by the presented pellet tracking system together with a target operation mode that provides one and only one pellet in the interaction region most of the time. The goal is to track individual pellets in order to know their position with a resolution of a few tenths of a millimeter at the time of an interaction. The system must also be highly efficient and provide tracking information for essentially all pellets that pass the interaction region. Presented results from the design studies show that the goals can be fulfilled by this solution.

Triplet Finder: On the Way to Triggerless Online Reconstruction with GPUs for the PANDA Experiment

PANDA is a state-of-the-art hadron physics experiment currently under construction at FAIR, Darmstadt. In order to select events for offline analysis, PANDA will use a software-based triggerless online reconstruction, performed with a data rate of 200 GB/s.To process the raw data rate of the detector in realtime, we design and implement a GPU version of the Triplet Finder, a fast and robust first-stage tracking algorithm able to reconstruct tracks with good quality, specially designed for the Straw Tube Tracker sub-detector of PANDA. We reduce the algorithmic complexity of processing many hits together by splitting them into bunches, which can be processed independently. We evaluate different ways of processing bunches, GPU dynamic parallelism being one of them. We also propose an optimized technique for associating hits with reconstructed track candidates.The evaluation of our GPU implementation demonstrates that the Triplet Finder can process almost 6 Mhits/s on a single K20X GPU, making it a promising algorithm for the online event filtering scheme of PANDA.

Studies on implementation of pellet tracking in hadron physics experiments

A system for optical tracking of frozen hydrogen microsphere targets (pellets) has been designed. It is intended for the upcoming hadron physics experiment PANDA at FAIR, Darmstadt, Germany. With such a tracking system one can reconstruct the positions of the individual pellets at the time of a hadronic interaction in the offline event analysis. This gives information on the position of the primary interaction vertex with an accuracy of a few 100 μm, which is very useful e.g. for reconstruction of charged particle tracks and secondary vertices and for background suppression. A study has been done at the WASA detector setup (Forschungszentrum Julich, Germany) to check the possibility of classification of hadronic events as originating in pellets or in background. The study has been done based on the instantaneous rate a Long Range TDC which was used to determine if a pellet was present in the accelerator beam region. It was clearly shown that it is possible to distinguish the two event classes. Also, an experience was gained with operation of two synchronized systems operating in different time scales, as it will also be the case with the optical pellet tracking.

A pellet tracking system for hadron physics experiments

Frozen microspheres of hydrogen (pellets) are used as targets in the hadron physics experiment WASA (Forschungszentrum Julich, Germany) (1) and will also be used in the future PANDA experiment at FAIR (GSI, Darmstadt, Germany) (2). The interaction region is defined by the overlap of the pellet stream and the accelerator beam and has a size of a few millimeters. One would like to know the interaction point more precisely, to have better possibility to reconstruct particle tracks and events. One would also like to suppress background events that do not originate in a pellet, but e.g. may occur in residual gas in the beam pipe. A solution is provided by the presented pellet tracking system, for which a prototype (3) has been developed in Uppsala. The goal is to track individual pellets in order to know their position at the time of an interaction. The design of such a system, simulation techniques and results are presented.

Physics with antiprotons at [formula omitted]ANDA

The P¯ANDA collaboration (anti-Proton ANnihilations at DArmstadt) is a next generation hadron physics experiment to be operated at the future Facility for Antiproton and Ion Research (FAIR) at Darmstadt, Germany. It will use intensive cooled antiproton beams with a momentum between 1.5 GeV/c and 15 GeV/c. The P¯ANDA detector is a state-of-the-art internal target detector allowing the detection and identification of neutral and charged particles almost in the whole solid angle.One of the major goal of the experiment is the comprehensive study of charmonium and candidates to the hybrids, molecules and other exotics. Charmonium states with different quantum numbers can be reached via the decay of these resonances. The P¯ANDA will scan the parameters of the resonances in formation mode with the use of the excellent momentum resolution Δp/p=104 – 105 of the HESR beam. The precision measurements of light mesons mass and width will be fulfilled as well as glueball search.Study of double hyperon production including their spin properties is another important item of the P¯ANDA experiment.

Hadron Experimental Facility at J-PARC

We introduce the hadron experimental facility at J-PARC. High-intensity secondary beam lines are in operation, where kaons, pions, and antiprotons are delivered for experiments in hadron, nuclear, and particle physics. We present overview of some experimental programs in this facility. A high-momentum beam line is under construction, where a new research project is proposed by RCNP of Osaka University under the MoU on collaborative research among RCNP, IPNS/KEK, and the J-PARC center. A future plan to extend the hadron experimental facility is also described.

STEP-to-ROOT – from CAD to Monte Carlo Simulation

Modern experiments in hadron and particle physics are searching for more and more rare decays which have to be extracted out of a huge background of particles. To achieve this goal a very high precision of the experiments is required which has to be reached also from the simulation software. Therefore a very detailed description of the hardware of the experiment is needed including also tiny details.To help the developers of the simulation code to achieve the required level of detail in geometry a semi-automatic tool was developed which is able to convert geometry descriptions coming from CAD programs into ROOT geometries which can be used directly in any ROOT based simulation software.

Status and hadron physics program of J-PARC

Current status and hadron physics programs of Japan Accelerator Research Complex (J-PARC) are reported. Several physics programs are proposed at the Hadron Hall of J-PARC. Strangeness and hyper nuclear physics is undertaken at K1.8 beam line. Study of meson nucleon bound system is underway at K1.8BR beam line. After the earth- quake, all beam line components and experimental setups are reassembled. Protons are successfully accelerated in the last December and hadron physics experiments are re- sumed in this February. In this manuscript, status of on-going experiment and near future plans of such physics programs are reported. Especially, a new beam line for a primary protons and high momentum secondary particles is proposed to study meson properties in nucleus.

High density cluster jet target for storage ring experiments

The design and performance of a newly developed cluster jet target installation for hadron physics experiments are presented which, for the first time, is able to generate a hydrogen cluster jet beam with a target thickness of above $10^{15}\,\mathrm{atoms/cm}^2$ at a distance of two metres behind the cluster jet nozzle. The properties of the cluster beam and of individual clusters themselves are studied at this installation. Special emphasis is placed on measurements of the target beam density as a function of the relevant parameters as well as on the cluster beam profiles. By means of a time-of-flight setup, measurements of the velocity of single clusters and velocity distributions were possible. The complete installation, which meets the requirements of future internal fixed target experiments at storage rings, and the results of the systematic studies on hydrogen cluster jets are presented and discussed.