113403181
New data acquisition system for the COMPASS experiment
The modern market offers low cost high performance FPGA integrated circuits equipped with dozens of multi gigabit serial links making them ideal devices for data transmission and data sorting applications. Therefore we have designed the new DAQ system that would perform the detector readout and event building in a custom made FPGA based hardware. The software part will provide the control and monitoring function. Currently, the prototypes of the new FPGA card are being tested and the control and monitoring software is being prepared for the tests with the real hardware.
14827287
FPGA based data acquisition system for COMPASS experiment
This paper presents the current data acquisition system (DAQ) of the COMPASS experiment at CERN and discusses development of a new DAQ. The aim of the new DAQ is to substitute software event building by structure composed of special FPGA cards that will do the event building. The software part of the new DAQ is robust multinode system with high emphasis on reliability. It is based on state machines and implemented in C++ with usage of the QT framework, the DIM library, and the IPBus technology. A prototype of the system has been developed and tested. The new DAQ software fulfills given requirements.
118063177
Measurement of the Pion Polarizability at COMPASS
The value of the pion polarizability is predicted with high precision by Chiral Perturbation Theory. However, the existing experimental values are at tension with this prediction as well as among themselves. The COMPASS experiment at the CERN SPS accesses pion-photon reactions via the Primakoff effect, where high-energetic pions react with the quasi-real photon field surrounding the target nuclei. Flagship channel is the Primakoff reaction in which a single real photon is produced, giving access to pion Compton scattering. Using this process the pion polarizability is extracted from the measured cross-section shape. End of 2009 COMPASS performed a measurement of the pion polarizability using a nickel target. The large amount of data collected in combination with the possibility to study systematic effects using the analogous reaction with a muon beam, the most precise experimental value to date was determined.
8636737
The universal sampling ADC readout system of the COMPASS experiment
The COMPASS experiment (COmpact Muon Proton Apparatus for Structure and Spectroscopy) is a fixed target experiment located at the CERN Super Proton Synchrotron. The physics program is focused on the study of hadron structure and hadron spectroscopy with high intensity muon and hadron beams, up to 160 GeV/c for muons and 190 GeV/c for hadrons respectively. To allow the tracking of charged particles with very low and as well very high momentum, COMPASS comprises two magnetic spectrometer stages extending to a total length of 60 m. From the data acquisition point of view, about 200000 analog detector channels have to be read along the complete experiment. Depending on the detector signal characteristics and the number of channels, this task is realized by frontend electronics using either dedicated ASICs and/or sampling analog-to-digital (ADC) or time-to-digital (TDC) components. The sampling ADC based readout system of the COMPASS experiment comprises today over 127k channels equipped with the APV25 frontend ASIC and 5728 direct sampling channels. An important feature from the beginning was the combination of data transfer, clock and trigger distribution and configuration access within a standardized serial interface between the different ADC modules and the first stage of data concentrator modules. By choosing between a copper or fiber realization for this interface, either a low cost interconnect or a link with galvanic decoupling can be realized. The ongoing development of the sampling ADC electronics is focused on the migration toward the Advanced Telecom Computing Architecture (ATCA) crate standard, to overcome the backplane bandwidth limitations in VME systems. In addition, the ATCA standard provides better cooling and monitoring capabilities. To simplify the transition to ATCA, the MSADC module was already realized as a mezzanine card, which can be mounted on an ATCA based carrier card as well. In addition, the MSADC card fits also to the MicroTCA form factor, which allows to provide a handy building block for laboratory based data acquisition systems.
47544178
A digital trigger for the electromagnetic calorimeter at the COMPASS experiment
At the COMPASS experiment at CERN's SPS many physics channels containing neutral particles are studied. These particles are identified by two electromagnetic calorimeters covering different transfers regions. For certain physics the main signature is described by these neutral particles which requires a calorimetric trigger system. The method described here is fully based on the existing front end electronics and uses digital pulse shape analysis techniques. This approach allows to implement a flexible trigger system as well as to reduce cost by avoiding to produce new electronic components. The implementation of this new trigger as well as the performance measured during the 2009 run will be discussed.
111119743
Upgrade of the COMPASS calorimetric trigger
In 2009 COMPASS performed a short measurement of neutral Primakoff reactions, characterised by highly energetic photons in one of the two electromagnetic calorimeters. A digital trigger was implemented in the existing readout electronics which calculates the energy released in the central region of the calorimeter. In 2012 a long measurement of these processes has been performed. In order to extend the kinematic range to lower energetic photons the trigger system has been upgraded in a way to be more selective to specific physics channels. The new ADC firmware preserves hit information and provides it to newly developed backplane trigger modules. There hits from all three thousand channels are processed and the trigger decision is made.
11354161
The Baryon asymmetry in the Standard Model with a low cut-off
We study the generation of the baryon asymmetry in a variant of the standard model, where the Higgs field is stabilized by a dimension-six interaction. Analyzing the one-loop potential, we find a strong first order electroweak phase transition for Higgs masses up to at least 170 GeV. Dimension-six operators induce also new sources of CP violation. We compute the baryon asymmetry in the WKB approximation. Novel source terms in the transport equations enhance the generated baryon asymmetry. For a wide range of parameters the model predicts a baryon asymmetry close to the observed value.
14730206
Reducing constraints in a higher dimensional extension of the Randall and Sundrum model
In order to investigate the phenomenological implications of warped spaces in more than five dimensions, we consider a 4 + 1 + δ dimensional extension to the Randall and Sundrum model in which the space is warped with respect to a single direction by the presence of an anisotropic bulk cosmological constant. The Einstein equations are solved, giving rise to a range of possible spaces in which the δ additional spaces are warped. Here we consider models in which the gauge fields are free to propagate into such spaces. After carrying out the Kaluza Klein (KK) decomposition of such fields it is found that the KK mass spectrum changes significantly depending on how the δ additional dimensions are warped. We proceed to compute the lower bound on the KK mass scale from electroweak observables for models with a bulk SU(2) × U(1) gauge symmetry and models with a bulk SU(2)R × SU(2)L × U(1) gauge symmetry. It is found that in both cases the most favourable bounds are approximately MKK ≳ 2 TeV, corresponding to a mass of the first gauge boson excitation of about 4 – 6 TeV. Hence additional warped dimensions offer a newwayof reducing the constraints on the KK scale.
5705117
Suppressing lepton flavor violation in a soft-wall extra dimension
A soft-wall warped extra dimension allows one to relax the tight constraints imposed by electroweak data in conventional Randall-Sundrum models. We investigate a setup, where the lepton flavor structure of the standard model is realized by split fermion locations. Bulk fermions with general locations are not analytically tractable in a soft-wall background, so we follow a numerical approach to perform the Kaluza-Klein reduction. Lepton flavor violation is induced by the exchange of Kaluza-Klein gauge bosons. We find that rates for processes such as muon-electron conversion are significantly reduced compared to hard-wall models, allowing for a Kaluza-Klein scale as low as 2 TeV. Accommodating small neutrino masses forces one to introduce a large hierarchy of scales into the model, making pressing the question of a suitable stabilization mechanism.
11539376
Baryogenesis in the two-Higgs doublet model
We consider the generation of the baryon asymmetry in the two-Higgs doublet model. Investigating the thermal potential in the presence of CP violation, as relevant for baryogenesis, we find a strong first-order phase transition if the extra Higgs states are heavier than about 300 GeV. The mass of the lightest Higgs can be as large as about 200 GeV. We compute the bubble wall properties, including the profile of the relative complex phase between the two Higgs vevs. The baryon asymmetry is generated by top transport, which we treat in the WKB approximation. We find a baryon asymmetry consistent with observations. The neutron electric dipole moment is predicted to be larger than about 10(-27) ecm and can reach the current experimental bound. Low values of tan beta are favored.
14031422
Cosmological constant, gauge hierarchy and warped geometry
It is suggested that the mechanism responsible for the resolution of the gauge hierarchy problem within the warped geometry framework can be generalized to provide a new explanation of the extremely tiny vacuum energy density ${\ensuremath{\rho}}_{V}$ suggested by recent observations. We illustrate the mechanism with some 5D examples in which the true vacuum energy is assumed to vanish, and ${\ensuremath{\rho}}_{V}$ is associated with a false vacuum energy such that ${\ensuremath{\rho}}_{V}^{1/4}\ensuremath{\sim}{\mathrm{TeV}}^{2}{/M}_{\mathrm{Pl}}\ensuremath{\sim}{10}^{\ensuremath{-}3}\mathrm{eV},$ where ${M}_{\mathrm{Pl}}$ denotes the reduced Planck mass. We also consider a quintessence-like solution to the dark energy problem.