No Arabic abstract
The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. First key results at low $t$ indicate a cusp-like structure in $K^+Sigma^0$ photoproduction at $W = 1900$,MeV, line shapes and differential cross sections for $K^+Lambda$(1405)$rightarrow K^+Sigma^0pi^0$, and a peak structure in $K^0_SSigma^0$ photoproduction. The peak in the $K^0_SSigma^0$ channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the $P_C$ pentaquark candidates in the heavy charmed quark sector.
BGO-OD is a newly commissioned experiment to investigate the internal structure of the nucleon, using an energy tagged bremsstrahlung photon beam at the ELSA electron facility. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating meson photoproduction. The extensive physics programme for open strangeness photoproduction is introduced, and preliminary analysis presented.
The BGO-OD experiment at the University of Bonns ELSA accelerator facility in Germany is ideally suited to investigate photoproduction at extreme forward angles. It combines a highly segmented BGO electromagnetic calorimeter at central angles and an open dipole magnetic spectrometer in the forward direction. This allows the detection of forward going kaons, and complex final states of mixed charge from hyperon decays. Current projects at the BGO-OD experiment include strangeness production of $gamma p rightarrow K^+ Lambda/Sigma^0$ at forward angles, $K^0Sigma^0$ with a deuteron target and $K^+Lambda(1405)$ line shape and cross section measurements.
Since the discovery of the $Lambda(1405)$, it remains poorly described by conventional constituent quark models, and it is a candidate for having an exotic meson-baryon or penta-quark structure, similar to states recently reported in the hidden charm sector. The $Lambda(1405)$ can be produced in the reaction $gamma p rightarrow K^+Lambda(1405)$. The pure I=0 decay mode into $Sigma^0pi^0$ is prohibited for the mass-overlapping $Sigma(1385)$. Combining a large aperture forward magnetic spectrometer and a central BGO crystal calorimeter, the BGO-OD experiment is ideally suited to measure this decay with the $K^+$ in the forward direction. Preliminary results are presented. *Supported by DFG (PN 388979758, 405882627).
An experiment designed to investigate the strangeness photoproduction process using a tagged photon beam in the energy range of 0.90 -1.08 GeV incident on a liquid deuterium target was successfully performed. The purpose of the experiment was to measure the production of neutral kaons and the lambda particles on a deuteron. The generation of photo produced particles was verified by the measurement of their decayed charged particles in the Neutral Kaon Spectrometer 2. The reconstructed invariant mass distributions were achieved by selecting events where two or more particles tracks were identified. Preliminary results are presented here.
We present the recent results of strangeness production at the mid-rapidity in Au + Au collisions at RHIC, from $sqrt{s_{rm NN}}$ = 7.7 to 200 GeV. The $v_2$ of multi-strange baryon $Omega$ and $phi$ mesons are similar to that of pions and protons in the intermediate $p_T$ range (2 - 5 GeV/$c$) in $sqrt{s_{rm NN}}$ = 200 GeV Au + Au collisions, indicating that the major part of collective flow has been built up at partonic stage. The breaking of mass ordering between $phi$ mesons and protons in the low $p_T$ range ($<$ 1 GeV/$c$) is consistent with a picture that $phi$ mesons are less sensitive to later hadronic interaction. The nuclear modification factor $R_{rm CP}$ and baryon to meson ratio change dramatically when the collision energy is lower than 19.6 GeV. It suggests a possible change of medium property of the system compared to those from high energies.