This documents describes the technical design and the
expected performance of the Barrel DIRC detector for
the PANDA experiment.
The Barrel DIRC will provide hadronic charged particle
identification in the polar angle range of 22 to 140 deg
for particle momenta between 0.5 GeV/c and 3.5 GeV/c.
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 pi/K
separation with at least 3 standard deviations over the
entire phase space of charged kaons in the Barrel DIRC.
Submitted by u.kurilla on Fri, 20/05/2016 - 18:24.
The present thesis comprises two parts, the first of which deals with the analysis of data
recorded by the BESIII experiment at the symmetric electron-positron collider BEPCII
located in Beijing, China.
A data set of 1.31 · 10^9 recorded J/ψ events has been analyzed to study the radiative decay
J/ψ → γωω. Both ω mesons were reconstructed via their decay into π^+ π^− π^0 . A clean
sample of 75245 ± 274 events was retained after the application of an event-based back-
ground subtraction method. Prominent enhancements located at the ωω mass threshold
and at the mass of the η_c (1S) are observed in the invariant mass spectrum of the ωω
system; no resonant structures are observed in the γω system. The selected data set was
subjected to a full partial wave analysis, for which two strategies were employed: A model
independent partial wave analysis in slices of the invariant ωω mass revealed that the ωω
system is dominated by pseudoscalar (0^−+ ) contributions. This assignment also holds
for both enhancements discussed above. Additionally, significant scalar (0^++ ) and tensor
(2^++ ) contributions in the region below 2.3 GeV/c^2 were found. Based on these results,
three main contributions were considered in a model dependent analysis, where the K-
matrix formalism was employed for the description of the decay dynamics. As the result
of an iterative approach, a good description of the data was achieved using parameteriza-
tions containing five poles for the pseudoscalar (η(1760), X(1835), η(2225), X(2500), η c ),
and two poles for each of the scalar (f_0 (1710), f_0 (2020)) and tensor (f_2 (1640), f_2 (1950))
contributions, respectively. The branching fraction for the decay J/ψ → γωω was deter-
mined to be B(J/ψ → γωω) = (2.50 ± 0.01 stat ± 0.16 syst ) · 10^−3 . In a dedicated analysis
step, the branching fraction of the decay η_c → ωω was measured for the first time as a
part of this thesis and amounts to B(η_c → ωω) = (1.88±0.09 stat. ±0.17 syst. ±0.44 ext. )·10^−3 .
In the second part, studies to facilitate the construction of the electromagnetic calorimeter
of the PANDA detector at the antiproton storage ring HESR are presented. The PANDA
experiment is to be built as a part of the future FAIR facility near Darmstadt, Germany.
The production of close-to-final sub-modules for the forward endcap of the calorimeter
is presented and the assembly of photodetector-preamplifier units is discussed. These
units are equipped with a Vacuum Photo Tetrode or two Avalanche Photo Diodes, each,
to detect scintillation light from lead tungstate crystals. The calorimeter modules were
tested during various test beam times with a prototype setup, utilizing electron and tagged
photon beams in the energy range between 23 and 15000 MeV. The energy resolution of
symmetric crystal matrices was determined to be σ_E/E = (2.41±0.02)%⊕ (0.86 ± 0.02)% / sqrt(E[GeV ])
the analysis of the test beam data.
The PANDA experiment will be one of the flagship experiments at the future Facility
for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. It is a versatile
detector dedicated to topics in hadron physics, such as charmonium spectroscopy
and nucleon structure. A DIRC counter will deliver hadronic particle identification
in the barrel part of the PANDA target spectrometer and will cleanly separate kaons
with momenta up to 3.5 GeV/c from a large pion background. An alternative DIRC
design option, using wide Cherenkov radiator plates instead of narrow bars, would
significantly reduce the cost of the system. Compact fused silica photon prisms have
many advantages over the traditional stand-off boxes filled with liquid. This work
describes the study of these design options, which are important advancements of
the DIRC technology in terms of cost and performance. Several new reconstruction
methods were developed and will be presented. Prototypes of the DIRC components
have been built and tested in particle beam, and the new concepts and approaches
were applied. An evaluation of the performance of the designs, feasibility studies
with simulations, and a comparison of simulation and prototype tests will be
Submitted by e.prencipe on Wed, 04/05/2016 - 16:08.
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.
Submitted by a.sanchez on Mon, 11/04/2016 - 10:53.
Nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena.
Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their
outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems
which contain two or even more units of strangeness. 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 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. For the first time it will be possible to study the behaviour of anti-Cascade in
nuclear systems under well controlled conditions.