The Belle II experiment at the SuperKEKB collider in Tsukuba, Japan, has collected e+e- + e - collision data between 2019 and 2022. After reaching a record-breaking instantaneous luminosity of 4.71x1034 . 71x10 34 cm -2 s -1 and recording a dataset corresponding to 424 fb -1 , it completed its first planned long shutdown phase in December 2023. Aside from upgrades of the collider and detector maintenance, the shutdown was used for the installation of the two-layer Pixel VerteX Detector (PXD). As the innermost sub-detector, multiple scattering effects need to be reduced. PXD utilizes the Depleted P-channel Field Effect Transistor (DEPFET) technology, allowing for a material budget of 0.21% X0 0 per layer. Each of the tracker's 40 modules consists of an array of 250x768 pixels with a pitch ranging from 50 mu mx 55 mu m for the inner to 85 mu mx 55 mu m for the outer layer yielding high gain and high signal-to-noise ratio while retaining about 99% hit efficiency. This article discusses the experience of the 4-year operation of the previous single-layer PXD in harsh background conditions as well as commissioning and testing of the fully-populated PXD2 during Long Shutdown 1.

This corrects the article DOI: 10.1103/PhysRevLett.92.062301.

This corrects the article DOI: 10.1103/PhysRevLett.89.132301.

Studies of e(+)e(-)-> D-s(+)(D) over bar (()*K-)0(-) and the p-wave charmed-strange mesons are performed based on an e(+)e(-) collision data sample corresponding to an integrated luminosity of 567 pb(-1) collected with the BESIII detector at root s = 4.600 GeV. The processes of e(+)e(-)-> D-s(+)(D ) over bar*K-0(-) and D-s(+)(D ) over bar K-0(-) are observed for the first time and are found to be dominated by the modes Ds+Ds1 (2536)(-) and Ds(+)Ds*(s2) (2573)(-), respectively. The Born cross sections are measured to be sigma(B)(e(+)e (-)-> D-s(+)(D ) over bar K-*0(-) (10.1 +/- 2.3 +/- 0.8) pb and D-s(+)(D ) over bar K-0(-) = (19.4 +/- 2.3 +/- 1.6) pb, and the products of Born cross section and the decay branching fraction are measured to be sigma(B)(e(+)e (-)-> Ds+Ds1(2536)(-)+c.c).B(D-s1(2536)(-) = ( 7.5 +/- 1.8 +/- 0.7) pb and sigma(B)(e(+)e(-)-> Ds+Ds1+(2573)(-)c.c.). B(D-s1(2573)(-)-> (D ) over bar*K-0(-)) = (19.7 +/- 2.9 +/- 2.0) pb. For the D-s1(2536)(-) and D-s2(2573)(-) mesons, the masses and widths are measured to be M(D-s1(2536)(-)) = (2537.7 +/- 0.5 +/- 3.1) MeV/c(2), Gamma(D-s1(2536)(-)) = (1.7 +/- 1.2 +/- 0.6)MeV, and M(D-s2*(2573)(-)) = (2570.7 +/- 2.0 +/- 1.7) MeV/c(2), Gamma(D-s2(2573)(-)) = (17.2 +/- 3.6 +/- 1.1) MeV. The spin-parity of the D-s2*(2573)(-) meson is determined to be J(P) = 2(+). In addition, the processes e(+)e(-)-> D-s(+)(D ) over bar*K-0(-) are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the 90% confidence level on the cross sections are determined.

The Belle II experiment at the future SuperKEKB collider in Tsukuba, Japan, features a design luminosity of 8 . 10(35) cm(-2)s(-1), which is a factor of 40 larger than that of its predecessor Belle. The pixel detector (PXD) with about 8 million pixels is based on the DEPFET technology and will improve the vertex resolution in beam direction by a factor of 2. With an estimated trigger rate of 30 kHz, the PXD is expected to generate a data rate of 20 GBytes/s, which is about 10 times larger than the amount of data generated by all other Belle II subdetectors. Due to the large beam-related background, the PXD requires a data acquisition system with high-bandwidth data links and realtime background reduction by a factor of 30. To achieve this, the Belle II pixel DAQ uses an FPGA-based computing platform with high speed serial links implemented in the ATCA (Advanced Telecommunications Computing Architecture) standard. The architecture and performance of the data acquisition system and data reduction of the PXD will be presented. In April 2016 and February 2017 a prototype PXD-DAQ system operated in a test beam campaign delivered data with the whole readout chain under realistic high rate conditions. Final results from the beam test will be presented.

The BESIII experiment at the BEPCII electron positron collider at IHEP (Beijing) is collecting data in the charm-tau mass region. Electron positron collisions are a very well suited environment for the study of initial state radiation (ISR). However, the photons from ISR are strongly peaked towards small polar angles and are currently detected with limited efficiency.In order to increase the detection efficiency of ISR photons, we are developing small-size calorimeters to be placed in the very forward and backward regions. Each detector will consist of two 4 x 3 arrays of 1 x 1 x 14 cm(3) LYSO crystals. A 1 cm gap separating each of the two arrays will reduce the contamination from background at very low angles. The scintillation light will be collected by silicon photomultipliers (SiPMs). The expected event rate in the MHz range requires flash ADCs recording the preamplified SiPM outputs. The digitized waveforms will be analyzed in realtime yielding data reduction and pile-up detection. This high bandwidth data stream will be transmitted via optical fibers to FPGA-based hardware performing sub-event building, buffering, and event correlation with the BESIII trigger. The sub-events with a corresponding trigger will be sent to the BESIII event builder via TCP/IP.A single crystal equipped with a SiPM was instrumented as a prototype detector. Tests with radioactive sources were performed successfully.

Received 24 January 2017DOI:https://doi.org/10.1103/PhysRevC.95.039906©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective flowPolarization phenomenaRelativistic heavy-ion collisionsPhysical SystemsHyperonsNuclear Physics

The system created in non-central relativistic nucleus-nucleus collisions possesses large orbital angular momentum. Due to spin-orbit coupling, particles produced in such a system could become globally polarized along the direction of the system angular momentum. We present the results of Lambda and anti-Lambda hyperon global polarization measurements in Au+Au collisions at sqrts_NN=62.4 GeV and 200 GeV performed with the STAR detector at RHIC. The observed global polarization of Lambda and anti-Lambda hyperons in the STAR acceptance is consistent with zero within the precision of the measurements. The obtained upper limit, |P_Lambda,anti-Lambda| <= 0.02, is compared to the theoretical values discussed recently in the literature.

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (πN) TDAs from \(\bar pp \to e^ + e^ - \pi ^0 \) reaction with the future P̄ANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q 2, the amplitude of the signal channel \(\bar pp \to e^ + e^ - \pi ^0 \) admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring \(\bar pp \to e^ + e^ - \pi ^0 \) with the P̄ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. \(\bar pp \to \pi ^ + \pi ^ - \pi ^0 \) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q 2 < 4.3 GeV2 and 5 < q 2 GeV2, respectively, with a neutral pion scattered in the forward or backward cone \(\left| {\cos \theta _{\pi ^0 } } \right| > 0.5\) in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the P̄ANDA detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107) at low (high) q 2 for s = 5 GeV2, and of 1 · 108 (6 · 106) at low (high) q 2 for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb−1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with P̄ANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing π TDAs.

Using a sample of 1.31 x 10(9) J/psi events collected with the BESIII detector at the BEPCII collider, the decays J/psi -> phi pi(+)pi(-)pi(0) and J/psi -> phi pi(0)pi(0)pi(0) are investigated. The isospin- violating decay J/psi -> phi pi(0)f(0)(980) with f(0)(980)-> pi pi is observed for the first time. The width of the f(0)(980) obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the pi(0)f(0)(980) mass spectrum, there is evidence of f(1)(1285) production. By studying the decay J/psi ->eta', the branching fractions of eta' -> pi(+)pi(-)pi(0) and eta' -> pi(0)pi(0)pi(0), as well as their ratio, are also measured.

The P̅ANDA detector at the future FAIR facility in Darmstadt, Germany will operate with a very high anti-proton interaction rate of up to 2 × 107/s in a free streaming mode without hardware triggers. Several hundreds of GB/s of data have to be read out. Sophisticated event filtering mechanisms based on tracking, calorimetry and particle identification are required in order to reject background events and reducing the amount of raw data by three orders of magnitude. This goal can be achieved by full event reconstruction and filtering in a highly parallelized and pipelined architecture including Field Programmable Gate Array (FPGA) platforms as well as Graphics Processing Units and PC farms. In this contribution, we present a prototype setup consisting of up to 4 FPGA based Compute Nodes, xTCA (extended Telecommunications Computing Architecture) compliant boards with a microTCA form factor, featuring a Xilinx Virtex 5FX70T2 FPGA, 2 × 2 GB DDR2, 1 Gb Ethernet, and 4 SFP+ (Small Form-Factor Pluggable) interfaces. This subsystem will be driven by up to 9 data concentrators receiving data from sub-detector front-end electronics. The data is formatted into sub-events. Synchronization is achieved by matching SODANET (Synchronization of Data Acquisition) time stamps distributed to all sub-systems. Sub-events are subsequently combined to events that are transmitted to a server farm for further processing and mass storage. Each step of the Data Acquisition chain features optional event filtering.

At the future Belle II experiment the DEPFET (DEPleted Field Effect Transistor) pixel detector will consist of about 8 million channels and is placed as the innermost detector. Because of its small distance to the interaction region and the high luminosity in Belle II, for a trigger rate of about 30kHz with an estimated occupancy of about 3% a data rate of about 22GB/s is expected. Due to the high data rate, a data reduction factor higher than 30 is needed in order to stay inside the specifications of the event builder.The main hardware to reduce the data rate is a xTCA based Compute Node (CN) developed in cooperation between IHEP Beijing and University Giessen. Each node has as main component a Xilinx Virtex-5 FX70T FPGA and is equipped with 2 x 2 GB RAM, GBit Ethernet and 4 x 6.25 Gb/s optical links. An ATCA carrier board is able to hold up to four CN and supplies high bandwidth connections between the four CNs and to the ATCA backplane.To achieve the required data reduction on the CNs, regions of interest (ROI) are used. These regions are calculated in two independent systems by projecting tracks back to the pixel detector. One is the High Level Trigger (HLT) which uses data from the Silicon Vertex Detector (SVD), a silicon strip detector, and outer detectors. The other is the Data Concentrator (DATCON) which calculates ROIs based on SVD data only, in order to get low momentum tracks. With this information, only PXD data inside these ROIs will be forwarded to the event builder, while data outside of these regions will be discarded.First results of the test beam time in January 2014 at DESY with a Belle II vertex detector prototype and full DAQ chain will be presented.

This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.

This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the \(\overline{P}\)ANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole \(\overline{P}\)ANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.