118642754
TUnfold, an algorithm for correcting migration effects in high energy physics
TUnfold is a tool for correcting migration and background effects in high energy physics for multi-dimensional distributions. It is based on a least square fit with Tikhonov regularisation and an optional area constraint. For determining the strength of the regularisation parameter, the L-curve method and scans of global correlation coefficients are implemented. The algorithm supports background subtraction and the propagation of statistical and systematic uncertainties, in particular those originating from limited knowledge of the response matrix. The program is interfaced to the ROOT analysis framework.
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.
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%.
118475032
Polarisation at HERA - Reanalysis of the HERA II Polarimeter Data -
In this technical note we briefly present the analysis of the HERA polarimeters (transversal and longitudinal) as of summer 2011. We present the final reanalysis of the TPOL data, and discuss the systematic uncertainties. A procedure to combine and average LPOL and TPOL data is presented.
118897178
Searches for Contact Interactions at HERA
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.
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.