119271704
A high precision Fabry-Perot cavity polarimeter at HERA
A Fabry-Perot cavity polarimeter, installed in 2003 at HERA for the second phase of its operation, is described. The cavity polarimeter was designed to measure the longitudinal polarisation of the HERA electron beam with high precision for each electron bunch spaced with a time interval of 96?ns. Within the cavity the laser intensity was routinely enhanced up to a few kW from its original value of 0.7 W in a stable and controllable way. By interacting such a high intensity laser beam with the HERA electron beam it is possible to measure its polarisation with a relative statistical precision of 2% per bunch per minute. Detailed systematic studies have also been performed resulting in a systematic uncertainty of 1%.
118897178
Searches for Contact Interactions at HERA
111251416
The CIP2k first-level trigger system at the H1 experiment at HERA
The ep-collider HERA at DESY, Germany, and the high energy physics experiments HI and ZEUS were upgraded in the years 2000-2002. The expected specified luminosity is five times higher than before. One of the upgrade projects was to build a set of new multi wire proportional chambers (CIP2k) providing information to distinguish between events induced by the beam background, and ep-interactions on an early stage of the trigger. This new first level trigger system provides a trigger decision using a total of about 10,000 channels of the chamber at a speed of 10.4 MHz. The system is realized in large field programmable gate arrays (FPGA) in order to comply with the timing requirements, which are necessary for a dead time free trigger decision within 1.5 /spl mu/s. This is achieved by simultaneous event pipelining and readout while preparing the trigger decision. The total data throughput rate is 108 GB/s. The system is developed in the hardware description language Verilog. Special attention is drawn to an integrated error correction system in the FPGA, which cannot be realized in hard wired electronics. This system is necessary to ensure maximum pattern recognition efficiency even at high occupancy. The CIP2k trigger system was installed in 2001 in parallel to the HERA startup and is now being commissioned in order to reach its best performance. The flexible programmable hardware clearly is a big advantage here.
14247648
Recent Results from the H1 Collaboration
DESY HamburgNotkestrase 85, 22607 Hamburg - GermanyAn overview of recent physics results from the H1 collaboration is given. The coveredareas are: rare processes and searches for new physics, structure functions and inclusivemeasurements, heavy ﬂavour production, QCD and hadronic ﬁnal states, diﬀractivescattering.
111088735
A first level trigger subsystem CIP2k for the H1 experiment at HERA
Abstract The ep-collider HERA at DESY and the high energy physics experiment H1 were upgraded in the years 2000–2002. A specific luminosity three times higher than before has recently been observed. To cope with the higher luminosity and the more complex background situation a set of five new cylindrical multiwire proportional chambers (CIP2k) were built providing information to distinguish between beam-gas induced background events and true ep-interactions within 2.3 microseconds on a first level trigger stage using all channels of the chambers. The five cylindrical chambers with a cathode pad readout have each a 16 fold segmentation of the azimuth angle and a segmentation of about 120 in z along the beam axis. The total number of readout channels amounts to 9600. Groups of 60 cathode pads are read out via striplines by a custom designed readout chip (CIPix). The on-chamber electronics digitizes and multiplexes the data and sends it via optical links to the trigger and data acquisition system at a rate of about 10 GBit/s per optical link. A histogram of the vertex distribution along the beam axis of the tracks crossing the chamber is calculated by the trigger system. From this histogram trigger informations are derived dividing the histogram in regions of background and physics events. The tracking algorithm is based on bit pattern comparison of pad data. Field-programmable gate arrays (FPGA) were chosen to accomplish this complex and highly parallelized task. In addition the FPGAs contain pipelines to store the chamber data making it possible to read out the information if a trigger occurs. The trigger, data acquisition and high voltage system are controlled and monitored by the experiment control system (ECS) based on commercial software called PVSSII.
117507353
Search for Leptoquarks and Lepton Flavor Violation at HERA
The data collected with the ep collider HERA at DESY in the years 1994–2000 at a centre-ofmass energy of 300− 320GeV has been searched for Leptoquarks and lepton-flavour violation. Leptoquarks are searched in the decay channels LQ− → `q(` = e,ν ,μ ,τ ). For masses below the centre-of-mass energy a leptoquark signals would show up as a resonance in the `q massspectra. At higher masses the signal may show up as a four-fermion interaction. No sign of processes involving leptoquarks has been found and limits on the leptoquark masses are set as a function of the leptoquark mass. For models involving lepton-flavour violation limits on the
110786689
A Fast Track Trigger for ATLAS at Super-LHC
The proposed upgrade of the LHC, the Super-LHC, will tenfold the peak luminosity to 1035 cm?2s?1 at a center of mass energy of (s)1/2 = 14 TeV. Depending on the upgrade scheme up to 400 events per bunch crossing have to be considered, a challenge especially for the tracking detectors and trigger systems of CMS and ATLAS. The ATLAS upgrade program foresees a new all-silicon inner detector and modifications to the trigger system. Exploiting track information already on the first trigger level, being only marginally done in the current ATLAS detector, is a promising option to reduce the L1 trigger rate and bandwidth. We describe a possible realisation of a Level 1 Track Trigger based on Content-Addressable-Memories and the impact of the new inner detector design on the track trigger performance.