Proceedings (PRO)

Proceedings of the CHEP 2016 conference. This proceeding describes the first use of the FairRoot based message queue system FairMQ for the analysis of MVD test beam data.

\panda is a planned experiment at FAIR (Darmstadt) with a cooled antiproton beam in a range [1.5; 15] GeV/$c$, allowing a wide physics program in nuclear and particle physics. It is the only experiment worldwide, which combines a solenoid field (B=2T) and a dipole field (B=2Tm) in a spectrometer with a fixed target topology, in that energy regime. The tracking system of \panda involves the presence of a high performance silicon vertex detector, a GEM detector, a Straw- Tubes central tracker, a forward tracking system, and a luminosity monitor. The offline tracking algorithm is developed within the PandaRoot framework, which is a part of the FairRoot project. The tool here presented is based on algorithms containing the Kalman Filter equations and a deterministic annealing filter. This general fitting tool (GENFIT2) offers to users also a Runge-Kutta track representation, and interfaces with Millepede II (useful for alignment) and RAVE (vertex finder). It is independent on the detector geometry and the B field map, and written in C++ o.o. modular code. Several fitting algorithms are available with GENFIT2, with user-adjustable parameters; therefore the tool is of friendly usage. A check on the fit convergence is done by GENFIT2 as well. The Kalman-Filter-based algorithms have a wide range of applications; among those in particle physics they can perform extrapolations of track parameters and covariance matrices. The impact of GENFIT2 on physics simulations performed for the \panda experiment is shown, with the PandaRoot framework: significant improvement is reported for those channels where a good low momentum tracking is required ($\rm{p_T} <$ 400 MeV/$c$

In this work, the performance of a proposed algorithm to search for clusters in the PANDA electromagnetic calorimeter (EMC) in real time, which provides vital informationfor the online event selection procedure, is discussed. Two implementations will be discussed and compared to each other and to a third, less suited algorithm (at least, as far as online usage is concerned). After this, the implementation in the readout hardware and concepts for the following data collection network will be presented.

The PANDA detector will be build as a part of the future FAIR facility in
Darmstadt. The availability of an antiproton beam with beam momenta up to 15
GeV/c will make possible a broad nuclear physics program. Topics like hadron
spectroscopy in the charmonium mass region, the property of hadrons inside
nuclear matter, hypernuclei physics, or nucleon properties using
electromagnetic processes are part of the physics program of PANDA. The main
part of this contribution concentrates on the feasibility of measurement of
nucleon structure observables, such as electromagnetic form factors or
transition distribution amplitudes, via electron or photon experiments in
PANDA.

The non-perturbative nature of the strong interaction leads to spectacular phenomena, such as the formation of hadronic matter, color confinement, and the generation of the mass of visible matter. To get deeper insight into the underlying mechanisms remains one of the most challenging tasks within the field of subatomic physics. The antiProton ANnihilations at DArmstadt (${\bar{\rm P}}$ANDA) collaboration has the ambition to
address key questions in this field by exploiting a cooled beam of antiprotons at the High-Energy Storage Ring (HESR) at the future Facility for Antiproton and Ion Research (FAIR) combined with a state-of-the-art and versatile detector. In this contribution, I will address some of the unique features of ${\bar{\rm P}}$ANDA that give rise to a promising physics
program together with state-of-the-art technological developments.

PANDA is a planned experiment at FAIR (Darmstadt, Germany) with a cooled
antiproton beam in a range [1.5; 15] GeV/c, allowing a wide physics
program in nuclear and particle physics. It is the only experiment
worldwide, which combines a solenoid field (B=2T) and a dipole field
(B=2Tm) in an experiment with a fixed target topology, in that energy
regime. The tracking system of \panda involves the presence of a high performance silicon vertex detector, a GEM detector, a Straw-Tubes central tracker, a forward tracking system, and a luminosity monitor. The offline tracking algorithm is developed within the PandaRoot framework, which is a part of the FAIRRoot project. The algorithm here presented is based on a tool containing the Kalman Filter
equations and a deterministic annealing filter ($genfit2$). $genfit2$ offers to
users also a Runge-Kutta track representation, and interfaces with Millepede II
(useful for alignment) and RAVE (vertex finder). The Kalman-Filter-based
algorithms have a wide range of applications; among those in particle physics they can perform extrapolations of track parameters and covariance matrices. The impact on physics simulations performed for the \panda experiment is showed for the first time, with the PandaRoot framework: improvement is shown for those channels where a good low momentum tracking is required ($p_T$ <350 MeV/c) of about a factor 2.

The performance of the most recent prototypes of the PANDA Barrel EMC will be compared. The first large scale prototype PROTO60 was designed to test the performance of the improved tapered lead tungstate crystals (PWO-II). The PROTO60 which consists of 6x10 crystals was tested at various accelerator facilities over the complete envisaged energy range fulfilling the requirements of the TDR of the PANDA EMC in terms of energy, position and time resolution. To realize the final barrel geometry and to test the final front end electronics, a second prototype PROTO120 has been constructed. It represents a larger section of a barrel slice, containing the most tapered crystals and the close to final components for the PANDA EMC. The performance of both prototypes will be compared with a focus on the analysis procedure including the signal extraction, noise rejection, calibration and the energy resolution. In addition, the influence of the non-uniformity of the crystal on the energy resolution will be discussed.

Hyperon production and the study of their properties is an important part of the physics programme of the future PANDA experiment at FAIR. Antihyperon-hyperon pairs will be produced in antiproton-proton collisions through the annihilation of at least one light antiquark-quark (u,d) pair and the creation of a corresponding number of antiquark-quark ss pairs. By measuring the decay products of the hyperons, spin observables such as the polarisation can be measured.
Many hyperons have a long life-time which give rise to final state particles originating from displaced vertices. A pattern recognition algorithm using information from the PANDA Straw Tube Tracker is extended to reconstruct not only the transversal, but also the longitudinal components of charged tracks. A Hough transform and a path finding method as tools to extract the longitudinal components is being developed.

Understanding the excitation pattern of baryons is indispensable for a deep insight into the mechanism of non-perturbative QCD. Up to now only the nucleon excitation spectrum has been subject to systematic experimental studies, while very little is known on excited states of double or triple strange baryons. In studies of antiproton-proton collisions the PANDA experiment is well-suited for a comprehensive baryon spectroscopy program in the multi-strange and charm sector. In the present study we focus on excited Ξ states. For final states containing a ΞΞ pair cross sections up to the order of μb are expected, corresponding to production rates of ~ 10^{6}/d at a Luminosity L=10^{31} cm^{-2} s^{-1}. Here we present the reconstruction of reactions of the type pbar p → Ξ* Ξ with Ξ* → Lambda K^{-} and its charge conjugate channel with the PANDA detector.

Stored antiprotons beams in the GeV range represent a unparalleled factory for hyperon-antihyperon
pairs. Their outstanding large production probability in antiproton collisions will open the floodgates
for a series of new studies of strange hadronic systems with unprecedented precision. The behaviour
of hyperons and – for the first time – of antihyperons in nuclear systems can be studied under well
controlled conditions. The exclusive production of Lambda-antiLambda and Sigma-antiLambda pairs in antiproton-nucleus interactions
probe the neutron and proton distribution in the nuclear periphery and will help to sample
the neutron skin. For the first time, high resolution
gamma-spectroscopy of doubly strange nuclei will be
performed, thus complementing measurements of ground state decays of double hypernuclei with
mesons beams at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions.
High resolution spectroscopy of multistrange Cascade atoms are feasible and even the production of
Omega-atoms will be within reach. The latter might open the door to the |s|=3 world in strangeness nuclear
physics, by the study of the hadronic Omega-nucleus interaction and the very first measurement of a
spectroscopic quadrupole moment of a baryon which will be a benchmark test for our understanding
of hadron structure.