PID Session at CM XXXI.

*** Cherenkov part *** Benno Kroeck, Giessen, The TOP Disc DIRC for the PANDA Detector Benno showed the focussing TOP design with 2-D readout and dichroic mirrors. he also showed simulations with and without knock-on electrons from the charged particles within the radiator disk. These electrons cause a background which makes the reconstruction more difficult. First results from the test experiment at GSI with 4 Si-PMTs from MEPhI fixed at the focussing light guide show expected results changing the incident angle.The amount of photons is only 3-10% of the expected yield, time resolution is 134ps. Alexander Britting, Erlangen, Progress of Lifetime measurement of MCP-PMT BINP #82 The quantum efficiency and aging measurements were presented. The photon efficiency as function of accumulated charge shows a drop of 30% at 30mC/cm2 for a gain of 7e5. The photon efficiency drop is stronger for longer wavelengths. He explains the drop with a ion deposit on the protection layer causing a loss in collection efficiency. That is consistent with the observation that the QE of the cathode measured without the channel plates drops slower than the photon detection efficiency measured behind the channel plates. Fred Uhlig, Erlangen, Studies of Photonis XP85013 MCP-PMT Results for two Planacon PMTs were shown. One called #81 shows a factor 100 higher dark rate compared to #82. The rate stability is a factor of 2 better than that of an 85011. The count rate uniformity of the channels of #82 suffers from 4 pixels with low count rates, the uniformity of gain suffers for both from pixels acting as hot spots with a higher gain factor of 2-3. The cross talk of #82 is 20% for all pixels when the outer pixels are illuminated. Otherwise it shows as #81 normal cross talk of a few percent. The timing resolution was for both around sigma = 50ps. Next step is to measure the aging of those candidates. Roland Hohler, GSI, Status of the radiator quality test Roland showed the absorption and reflection probability in one of the Lithotec radiator bars which he knows best for three wavelengths: 635nm, 532nm, and 405nm. He showed how he handled difficulties with the halo of the red laser and the non uniformity of the photo diodes with the blue laser. he looked also into the sensitivity of the measurement due to misaligned Brewster angle at which he couples the laser beam into the radiator. No big sensitivity was found. For that bar he gets a internal reflection probability which corresponds to an surface roughness of 15.5+-2.3 Angstrom. Dipanwita Dutta, GSI, Barrel DIRC Simulation in PANDAROOT The implementation of the barrel DIRC geometry in the PandaRoot framework was shown. The barrel has now a slit for the target pipe. The photon detector is now visible and the photons can be tracked. She corrected a bug in PndDrcHitProducerIdeal and implemented the new PndDrcHitProducerReal containing photon detection efficiency, pixelization and time resolution. She struggles in moment with the appearance of double rings in the image plane whose origin is unknown. Carsten Schwarz, GSI, Shape Measurements of Radiators He showed how to check if the angles of the radiator bars are rectangular and to measure the deviations from 90 degree. He found for two of the Lithotec bars deviations of up to 1-3mrad and for two bars from Miass deviations of 1-5mrad. A sample from the BaBar radiator producer (in that time Boeing) showed deviations in the order of the BaBar requirements of <0.25mrad. It is important to define the squareness requirements for the PANDA barrel DIRC. Matthias Hoek, Glasgow, Focussing Disc DIRC - Status Report After the introduction of setup and trigger scheme, analysis results from the GSI test experiments were shown. They measured the response of the quartz bar changing the incident angle of the beam. The light output of the PMT show a 25% gain mismatch compared to what was expected from the single photon response. The number of photons for different incident beam angles were compared to different absorption assumption within the radiator. The radiation hardness of Suprasil 2 is now better understood, the origin of two absorption maxima at wavelength 210nm and 260nm can be attributed to transition in the SiO2 system. For the simulation of the focussing DIRC there exists an implementation which is not yet available in PandaRoot. But it is expected that this happens within the next months. Matthias Hoek, Glasgow, Focussing Disc DIRC - TDR Draft Matthias explained, that a TDR is the deliverable for the current R&D funding period and it is due in early 2011. They need this deliverable to apply for the next funding period. It needs not to be a PANDA-TDR. He proposed a structure which can be also used by the TOP DIRC as a template. In the discussion it was not clear, if the name TDR as deliverable can be changed to something more neutral like Technical Report on the Focussing DIRC. Klaus Foehl, Giessen, Possible road map for the DIRCs The possible road map for the DIRCs in Klaus view included R&D, prototyping, test beams, simulations, performance assessments, design choices, and construction. He let open the question if the design choice between two versions of the endcap DIRC is before or after the TDR is written. The following discussion was driven by three questions of the Technical Coordinator: How many DIRCs do we want? How many TDRs do we want, need? What are the decision criteria? He urged for combining the efforts of the Glasgow and Giessen group to build one common endcap DIRC. In this context it was mentioned that there is already a working group "Towards the DIRC TDR" whose members consist of one representative from the participating institutes: Klaus Foehl (Giessen), Jochen Schwiening (GSI), Matthias Hoek (Glasgow), Albert Lehmann (Erlangen), Hans Marton (Vienna), and Valery Dodokhov (JINR). *** TOF part *** Alicia Sanchez Lorente, Mainz, Low kaon identification studies based on tof measurements Alicia showed a physics case for the TOF barrel. The associated production of Xi+ Xi- needs the efficient detection of the Xi+ which decays in low momenta kaons of about 0.5 GeV/c. the Xi+ annihilates with a nucleon of the primary target releasing up to two positive kaons which can be used to tag the reaction Xi-Xi+ over the pbarp annihilation process. The maximum of the kaon distribution is at polar angles of 30 degrees. The trigger efficiency increases by a factor of 1000 for a magnetic field of 0.5 T. Vladimir Vikhrov, PNPI, Relative TOF and PID Vladimir performed relative timing studies between different TOF detector subsystems with Pythia and Geant3. He reconstructs particles in the TOF wall assuming that TOF-left was hit by a negative pion. The same was done for negative and positive pions hitting the barrel. The studies show that pions can be well separated from protons. For the separation of pions from kaons a more elaborate implementation in PandaRoot is needed. Anton Izotov, PNPI, Forward TOF WALL prototype measurements Prototype measurements at the PNPI with a 730 MeV proton beam of a BC408 scintillator slab were shown. The slab was read out by a Hamamatsu R4998 PMT. The achieved a timing resolution better than 100ps. They plan next to equip the slabs with R2083 PMTs and with Geiger mode APDs.